operation, maintenance and repair of ......army tm 5-685 navy navfac mo-912 operation, maintenance...

ARMY TM 5-685NAVY NAVFAC MO-912

OPERATION, MAINTENANCE ANDREPAIR OF AUXILIARY GENERATORS

D E P A R T M E N T S O F T H E A R M Y A N D T H E N A V YAUGUST 1996

REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared. by and forpublic property and not ‘subject to copyright.

the Government and is

Reprints or republication of this manual should include a creditsubstantially as follows: “Joint Departments of the Army and theNavy TM 5-685/NAVFAC MO-912, Operation Maintenance and Repairof Auxiliary Generators, 26 August 1996”.

;P1 ARMY TECHNICAL MANUAL TM 5-685; No. 5-685 NAVFAC MO-912cI NAVY MANUAL5:.! No. NAVFAC MO-912,1i

HEADQUARTERS-___ -i” DEPARTMENTS OF THE ARMY AND THE NAVY?1; WASHINGTON, DC, 26 August 1996bt$ OPERATION, MAINTENANCE AND REPAIR OF AUXILIARY GENERATORSB,I

CHAPTER 1.

2

3.

--

4.

__Approved

INTRODUCTIONPurpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Explanation of abbreviations and terms ...................................................EMERGENCY POWER SYSTEMSEmergency power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Types ofpowergeneration sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Buildings & enclosures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fuel storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Distribution systems .....................................................................Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Load shedding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PRIME MOVERSMechanical energyy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diesel enginess. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Types of diesel engines.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diesel fuel system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diesel cooling system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Lubrication system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Starting system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Governor/speed control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Air intake system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Exhaust systemm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Service practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operational trends and engine overhaul ...................................................Gasturbineengines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Gas turbine engine classifications. ........................................................Principlesofoperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Gas turbine fuel system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Gas turbine cooling system.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Lubrication system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Starting system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Governor/speed control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Gas turbine service practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .GENERATORS AND EXCITERSElectrical energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Generator operationn. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Types of generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .AC generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Alternator types.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Design.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Characteristics of generators. .............................................................Exciters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Characteristics of exciters ................................................................Field flashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bearings and lubrication.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Generator maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Insulation testin gg.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

for public release. Distribution is unlimited.

Paragraph Page

l - l1-21-31-4

l - ll - ll - ll - l

2-l 2-l2-2 2-l2-3 2-22-4 2-22-5 2-32-6 2-32-7 2-42-8 2-42-9 2-82-10 2-9

3-l 3-l3-2 3-23-3 3-33-4 3-63-5 3-93-6 3-123-7 3-153-8 3-173-9 3-203-10 3-2 13-11 3-223-12 3-243-13 3-273-14 3-273-15 3-283-16 3-293-17 3-293-18 3-3 13-39 3-353-20 3-353-2 1 3-373-22 3-37

4-l 4-l4-2 4-l4-3 4-l4-4 4-l4-5 4-l4-6 4-74-7 4-74-8 4-84-9 4-94-10 4-94-11 4-94-12 4-104-13 4-11

TM 5-685/NAVFAC MO-912

CHAPTER 5.

6.

7.

8.

APPENDIX A.APPENDIX B.APPENDIX C.APPENDIX D.APPENDIX E.APPENDIX F.APPENDIX G.GLOSSARY

INDEX

SWITCHGEARSwitchgear definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Types of switchgear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Low voltage elements.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Medium voltage elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Transfer switchesss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Instrumentation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Relays.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Miscellaneous devices.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .OPERATING PROCEDURESRequirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Attended stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Unattended stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Nonparalleled stations.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Paralleled with the electric utility system. .................................................Paralleled with other generating units. ....................................................Operational testing.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ROUTINE MAINTENANCEInstructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Prime mover maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Generator and exciter maintenance .......................................................Switchgear maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .LUBRICATING OIL PURIFICATIONPurification systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Forms of contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Methods of purifyingg. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Oil maintenance procedures.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 - l5-25-35-45-55-65-75-85-9

6 - l6-26-36-46-56-66-7

7-l7-27-37-4

8- l8-28-38-4

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .FUEL AND FUEL STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .LUBRICATING OIL.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .COOLING SYSTEMS AND COOLANTS. ..............................................................SAFETY.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RECORDS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DIESEL ENGINES: OPERATION, TIMING, AND TUNING INSTRUCTIONS. ...........................

Paragraph Page

5-l5-l

--_

5-l5-95-135-155-175-185-20

6-l6-l6-26-26-46-46-4

7-l7-l7-47-5

8-l8-18-la 2A - lB - lc-1D-lE - lF - lG- l

. . . . . . . . . . . . . . . . . . ..~............................................................................... Glossary- 1

. . . . . . . . . . . . . . . . . . ..~...............................................................................

Figure 2- l .2-2.2-3.3- l .3-2.3-3.3-4.3-5.3-6.3-7.3-8.3-9.

3-10.3-11.3-12.3-13.3-14.3-15.3-16.3-17.3-18.3-19.3-20.3-2 1.

Typical installation of an emergency power plant. ....................................................Types of system grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical grounding system for a building .............................................................Typical gasoline powered emergency generator set, air cooled .........................................Typical small stationary diesel generator unit, air cooled. .............................................Typical large stationary diesel generator unit ........................................................Typical diesel power plant on transportable frame base. ..............................................Timing diagramss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diagram of typical fuel, cooling, lubrication, and starting systems .....................................Diesel engine liquid cooling system. .................................................................Cross section of diesel engine showing chamber for lubricating oil collection. ...........................Diesel engine lubrication system.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Battery for engine starting system.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chart of speed droop characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Mechanical governorr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Hydraulic governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Carburetor and pneumatic governor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Oil bath air cleanerr. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diagram of turbocharger operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Performance data plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance data plots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical gas turbine engine for driving electric power generator. .......................................Gas turbine engine, turboshaftt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical types of combustors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index- 1

Page2-32-52-93-23-33-33-43-53-73-103-143-153-163- 173-193-203-203-2 13-223-253-263-283-283-30

ii


rIr Figure 3-22.i 3-23.It

._ _3-24.IE$ 3-25.

[ 3-26.1 3-27.[i 4- l .7[ 4-2.;r - 4-3.

4-4.4-5.4-6.4-7.4-8.4-9.

4-10.5-l.5-2.5-3.5-4.5-5.5-6.5-7.5-8.5-9.

5-10.5-11.6- l .F- l .F-2.

Table 3- l .3-2.3-3.3-4.3-5.4- l .4-2.4-3.4-4.5-1.5-2.5-3.8-1.D-l.G-l.

Engine combustion section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Engine combustion liner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Air cooling modes of turbine vanes and blades .......................................................Turbine blade cooling air flow. ......................................................................Turbine vane cooling air flow .......................................................................Lubrication system for gas turbine ..................................................................Typical alternating current generator. ...............................................................Brush-type excitation system, schematic. ............................................................Brush-type AC generator field and rotor. ............................................................AC generator field with brushless-type excitation system .............................................Two-wire, single-phase alternator ...................................................................Three-wire, single-phase alternator .................................................................Three-wire, three-phase alternator ..................................................................Four-wire, three-phase alternator ...................................................................Dualvoltageandfrequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Powertriangle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Typical arrangement of metal enclosed switchgear. ...................................................Typical switchgear control circuitry, one-line diagram. ................................................Typical time-current characteristic curve ............................................................Instrument transformers, typical applications. .......................................................Current flow in instrument transformers. “Polarity” marks show instantaneous flows. ..................AC control circuitss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .AC control circuits with tie breaker .................................................................Maintenance for typical low voltage switchgear with air circuit breakers. ..............................Arc interruption in oil, diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Air blast arc interrupter, diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Cross sectional view of vacuum arc interrupter. ......................................................Typical station layout, one-line diagram .............................................................Emergency/Auxiliary generator operating log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Emergency/Auxiliary generator operating log (reverse). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LIST OF TABLES

Unit injector system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Common rail injector system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .In-line pumps and injection nozzle system ...........................................................Typical cooling system components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Dieselenginestroubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Generator inspection list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Generator troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Interpreting insulation resistance test results. .......................................................Condition of insulation indicated by dielectric absorption ratios .......................................Low voltage circuit breaker troubleshooting. .........................................................Switchgear equipment troubleshooting ..............................................................Relay troubleshootingg. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Oil quality standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Antifreeze solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Ignition delav and duration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page3-3 13-323-333-343-353-364-24-24--34-34-44-44-54--64-64-85-25-35-45-55-65-65-75-85-105-115-116-3F-2F-3

Page3-83-83-83-113-234-104-104-124-125-95-165-198-2D-2G- l

i i i

CHAPTER 1

INTRODUCTION


1-1. Purpose.This manual covers the various types of auxiliarypower generating systems used on military instal-lations. It provides data for the major componentsof these generating systems; such as, prime movers,generators, and switchgear. It includes operationof the auxiliary generating system componentsand the routine maintenance which should beperformed on these components. It also describesthe functional relationship of these components andthe supporting equipment within the complete sys-tem.

1-2. Scope.

-

The guidance and data in this manual are intendedto be used by operating, maintenance, and repairpersonnel. It includes operating instructions, stan-dard inspections, safety precautions, troubleshoot-ing, and maintenance instructions. The informationapplies to reciprocating (diesel) and gas turbineprime movers, power generators, switchgear, andsubsidiary electrical components. It also covers fuel,air, lubricating, cooling, and starting systems.

a. In addition to the information contained inthis manual, power plant engineers, operators, and

maintenance personnel must have access to allother literature related to the equipment in use.This includes military and commercial technicalmanuals and engineering data pertaining to theirparticular plant.

b. Appendixes B through F provide details re-lated to fuel storage, lubricating oil, coolant, formsand records, and safety (including first aid). Textsand handbooks are valuable tools for the trainedengineer, supervisor, and operator of a power plant.The manufacturers of the components publish de-tailed operating, maintenance, and repair manuals.Instructions, applicable to the equipment, are pro-vided by each manufacturer and should be filed atthe plant for safekeeping and use. Replacement cop-ies are available from each manufacturer.

1-3. References.Appendix A contains a list of references used in thismanual. Other pertinent literature may be substi-tuted or used as supplements.

1-4. Explanation of abbreviations and terms.Abbreviations and special terms used in thismanual are explained in the glossary.

1-1


CHAPTER 2

EMERGENCY POWER SYSTEMS

2-1. Emergency power.Emergency power is defined as an independent re-serve source of electric energy which, upon failureor outage of the normal source, automatically pro-vides reliable electric power within a specified time.

a. A reliable and adequate source of electricpower is necessary for the operation of active mili-tary installations. Power must also be available atinactive installations to provide water for fire pro-tection, energy for automatic fire alarms, light forsecurity purposes, heat for preservation of criticaltactical communications and power equipment, andfor other operations.

ally is started manually; a class B plant may haveeither a manual or an automatic start system. Ac-cordingly, a class B plant is almost as costly toconstruct and operate as a primary power plant ofsimilar size. Usually, a class B plant is apermanent-type unit capable of operating between1000 and 4000 hours annually. The class C plantalways has an autostart control system (set to startthe plant when the primary power voltage varies orthe frequency changes more than the specified op-erational requirements).

.._

b. Power, supplied by either the local utility com-pany or generated on-site, is distributed over theactivity. The source of distribution may be subject tobrownout, interruption or extended outage. Mis-sion, safety, and health requirements may requirean uninterruptible power supply (UPS) orstandby/emergency supply for specific critical loads.Justifiable applications for auxiliary generator are:

(1) Hospitals (life support, operating room,emergency lighting and communication, refrigera-tion, boiler plant, etc.).

(1) A class B plant (considered a standby long-term power source) is used where multiple commer-cial power feeders are not available or extended andfrequent power outages may occur. Total fuel stor-age must be enough for at least 15 days continuousoperation.

(2) Airfields (control tower, communications,traffic control, engine start, security, etc.).

(3) Data processing plant systems.(4) Critical machinery(5) Communication and security.

(2) A class C plant is used where rapid restora-tion of power is necessary to feed the load. Morethan one class C unit is usually used when thetechnical load exceeds 300 kW at 208Y/120 volts or600 kilowatts (kW) at 48OY/277 volts. Spare class Cunits are sometimes provided for rotational mainte-nance service. The autostart control system ensuresthat the load is assumed as rapidly as possible.Diesel engine prime movers may be equipped withcoolant and lubricating oil heaters to ensure quickstarting. Recommended total fuel storage must beenough for at least seven days continuous opera-tion.

c. It is essential that a schematic showing theloads to be carried by an auxiliary generator beavailable for reference. Do not add loads until it isapproved by responsible authority.

2-2. Types of power generation sources.a. The critical uses of electric power at a site

demand an emergency source of power whenever anoutage occurs. Selection of the type of auxiliary gen-erating plant is based on the mission of the particu-lar site and its anticipated power consumption rateduring an emergency. The cost of plant operation(fuel, amortized purchase price, depreciation, andinsurance) and operation and maintenance person-nel requirements must be analyzed. Future loadgrowth requirements of the site must be consideredfor size selection.

c. Emergency generators must provide adequatepower for critical loads of a building or a limitedgroup of buildings, heating plants, utility pumpingplant, communication centers, or other such instal-lations where interruption of normal service wouldbe serious enough to justify installation of an auxil-iary power plant. The plant must be reliable andeasily started in all seasons of the year. The plantbuilding should be completely fireproof with heatingand ventilation facilities that satisfy the plant’s re-quirements. The space around the units should per-mit easy access for maintenance and repair. Spaceshould be provided within the building for safe stor-age of fuel such as a grounded and vented “day”tank. Type and grade of fuel should be identified onthe tank. Important considerations for these plantsincluded the following:

b. Auxiliary power generating plants are desig- (1) Selection of generators (size and quantity,nated as either class B or class C. The design crite- type of prime mover, and load requirements).ria for a class B plant is comparable to those of a (2) Determination of need for instrumentationprimary power plant. A primary power plant usu- (meters, gauges, and indicator lights).

2-1


(3) Selection of protective equipment (relaysand circuit breakers).

(4) Determination of need for automatic start-ers, automatic load transfer, etc.

(5) Selection of auxiliary generator size isbased on satisfying the defined electrical load re-quirement (expressed as kilowatts).

d. Portable power plants are widely used on mili-tary installations because of the temporary natureof many applications. The power plants (including adiesel or gas turbine prime mover) are self-contained and mounted on skids, wheels, or semi-trailers. Although the size of portable units mayvary from less than 1 kW to more than 1,000 kW,the most commonly used units are less than 500 kWcapacity. Reciprocating prime movers are usuallyused for portable power plants. Gas turbine enginesare frequently employed for smaller units becauseof their relatively light weight per horsepower.

e. Portable diesel powered generators usually op-erate at 1200, 1800 or 3600 revolutions per minute(rpm), since high speeds allow a reduction in weightof the generator plant. To keep weight down, suchancillary equipment as voltage regulators, electricstarters and batteries are sometimes omitted fromthe smaller generators. Starting may be done bycrank or rope, ignition by magneto, and voltageregulation through air-gap, pole-piece, and windingdesign. Portable plants usually have a minimumnumber of meters and gauges. Larger size portableunits have an ammeter, a frequency meter, a volt-meter, and engine temperature and oil pressuregauges. Generator protection is obtained by fusedswitches or air circuit breakers.

2-3. Buildings and enclosures.a. Auxiliary power generating equipment, espe-

cially equipment having standby functions, shouldbe provided with suitable housings. A typical powerplant installation is shown in figure 2-l. The equip-ment should be located as closely as possible to theload to be served. Generators, prime movers,switchboards, and associated switching equipmentshould always be protected from the environment.Many small units are designed for exterior use andhave their own weatherproof covering. Transform-ers and high-voltage switching equipment can beplaced outdoors if they are designed with drip-proofenclosures.

b. The buildings housing large auxiliary powergenerating systems (see fig 2-1) require adequateceiling height to permit installation and removal ofcylinder heads, cylinder liners, pistons, etc., usingchain falls. An overhead I-beam rail, or movablestructure that will support a chain fall hoist, isnecessary. The building should have convenience

2-2

outlets and be well lighted with supplemental light-ing for instrument panels. Heat for the buildingshould be steam, heat pumps or electric heaters toavoid hazards from explosive vapors.

--

c. Prime movers require a constant supply oflarge quantities of air for combustion of fuel. Com-bustion produces exhaust gases that must be re-moved from the building since the gases are hazard-ous and noxious. The air is usually supplied via alouvered ventilation opening. Exhaust gases areconducted to the outside by piping that usually in-cludes a silencer or muffler (see fig 2-l).

d. Precautions must be taken when environmen-tal conditions related to location of the generatingsystem are extreme (such as tropical heat and/ordesert dryness and dust). Cooling towers and spe-cial air filters are usually provided to combat theseconditions. Arctic conditions require special heatingrequirements.

e. When required for the auxiliary generatingequipment, the building or enclosure should be fire-proof and constructed of poured concrete or concreteand cinder blocks with a roof of reinforced concrete,steel, or wood supports with slate or other fireproofshingles. Ventilation and openings for installationand removal of materials and equipment should beprovided.

(1) Foundations. A generator and its primemover should be set on a single, uniform foundationto reduce alignment problems. The foundationshould be in accordance with manufacturer’s recom-mendations for proper support of equipment anddampening of vibrations. Foundation, prime mover,and generator should be mechanically isolated fromthe building floor and structure to eliminate trans-mission of vibrations. All mechanical and electricalconnections should allow for vibration isolation.

(2) Floors. The floors are usually concrete withnon-skid steel plates over cable and fuel-linetrenches. The floor space should provide for servic-ing, maintenance, work benches, repair parts, toolcabinets, desks, switchboard, and electrical equip-ment. Battery bank areas require protection fromcorrosive electrolytes. Floors must be sealed to pre-vent dusting, absorption of oils and solvents, and topromote cleanliness and ease of cleanup. Plates andgratings covering floor trenches must be grounded.Rubber matting should be installed in front of andaround switchboards and electrical equipment tominimize shock hazard.

2-4. Fuel storage.Fuel storage space should be provided near theplant, with enough capacity to allow replenishmentin economical, reasonable intervals. The total fuelstorage capacity should be large enough to satisfy


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Figure 2-l. Typical installation of an emergency power plant.

the operational requirements of the class B or classC generating plants that are used. Fuel logisticsshould be considered when sizing fuel storage ca-pacity

a. Fuels for the equipment described herein (re-fer to app C) are combustible substances that can beburned in an atmosphere of oxygen. Two categoriesof fuel storage are discussed: liquids and gases. Ineither case, fuel storage tanks, associated pumpsand piping systems must be grounded and protectedfrom galvanic, stray current or environmental cor-rosion.

b. Liquid fuel for auxiliary power generating sys-tems is usually stored in buried tanks equippedwith vent pipes and manholes. Above-ground tanksmay be used for storage at some locations. Thesetanks usually have provisions for venting, fillingand cleaning. A gauge with indicator is used to de-termine tank contents. Two tanks are necessary toensure a continuous supply during tank cleaning(every two years) and maintenance operations. Pro-visions must be made to use a gauge stick to posi-tively determine depth of tank contents. Storagetanks should be checked for settled water accumu-lated through condensation and the free waterdrained periodically.

c. Gaseous fuel is stored in tanks either as a gasor a liquid, depending on the type of fuel. Naturalgas is stored as a gas. Butane and propane arecooled and kept under moderate pressure for stor-

age as liquids. Methods to determine tank contentsare covered in paragraph 5-7b(8).

d. Day tanks. A grounded and vented day tank,having not more than 275 gallons capacity, is in-stalled within the power plant building. The tank isnormally filled by transfer pump from the installa-tion’s main storage tank. Provision should be madeto fill the day tank by alternate means (or directlyfrom safety cans or barrels) if the transfer systemfails.

2-5. Loads.Most electrical plants serve a varied load of light-ing, heating equipment, and power equipment,some of which demand power day and night. Theannual load factor of a well-operated installationwill be 50 percent or more with a power factor of 80percent or higher. Equipment and controls must beselected to maintain frequency and voltage over theload range.

2-6. Distribution systems.a. The load determines direct current (DC) or

alternating current (AC), voltage, frequency (DC, 25Hertz (Hz), 50 Hz, 60 Hz, 400 Hz), phases and ACconfiguration (delta or wye). Voltage and other pa-rameters of the distribution system will have beenselected to transmit power with a minimum of con-version (AC to DC), inversion (DC to AC), (AC)transformer, impedance, and resistance loss. For a

2-3


given load; higher voltage, unity power factor, lowresistance/impedance, and lower frequency gener-ally result in lower distribution losses. Use of equip-ment to change or regulate voltage, frequency orphase introduces resistance, hysteresis and me-chanical losses.

b. A lagging power factor due to inductive loads(especially under-loaded induction motors) resultsin resistive losses (I’R) because greater current isrequired for a given power level. This may be cor-rected by the use of capacitors at the station bus orby “run” capacitors at induction motors to have thegenerator “see” a near-unity but yet lagging powerfactor.

c. Overcorrection, resulting in a leading (capaci-tive) power factor must be avoided. This conditionresults in severe switching problems and arcing atcontacts. Switching transients (voltage spikes, har-

monic transients) will be very damaging to insula-tion, controls and equipment. The electronics in ra-dio, word and data processing, and computer arraysare especially sensitive to switching and lightingtransients, over/under voltage and frequencychanges.

d. The distribution system must include sensingdevices, breakers, and isolation and transfer feedswitches to protect equipment and personnel.

2-7. Frequency.The frequency required by almost all electricalloads is the standard 50 or 60 Hz. Most electricalequipment can operate satisfactorily when the fre-quency varies plus or minus ten percent (tlO%).Steady state frequency tolerance (required forfrequency-sensitive electronic equipment) shouldnot exceed plus or minus 0.5 percent of design fre-quency. Since some equipment are sensitive to fre-quency changes, operators must closely monitor fre-quency meters and regulate frequency whennecessary.

2-8. Grounding.Grounding implies an intentional electrical connec-tion to a reference conducting plane, which may beearth (hence the term ground) but more generallyconsists of a specific array of interconnected electri-cal conductors referred to as grounding conductors.The term “grounding” as used in electric power sys-tems indicates both system grounding and equip-ment grounding, which are different in their objec-tives.

a. System grounding relates to a connection fromthe electric power system conductors to ground forthe purpose of securing superior performance quali-ties in the electric system. There are several meth-ods of system grounding. System grounding ensures

2-4

longer insulation life of generators, motors, trans-formers, and other system components by suppress-ing transient and sustained overvoltages associatedwith certain fault conditions. In addition, systemgrounding improves protective relaying by provid-ing fast, selective isolation of ground faults.

b. Equipment grounding, in contrast to systemgrounding, relates to the manner in whichnoncurrent-carrying metal parts of the wiring sys-tem or apparatus, which either enclose energizedconductors or are adjacent thereto, are to be inter-connected and grounded. The objectives of equip-ment grounding are:

----

(1) To ensure freedom from dangerous electricshock-voltage exposure to persons.

(2) To provide current-carrying capability dur-ing faults without creating a fire or explosive haz-ard.

(3) To contribute to superior performance of theelectric system.

c. Many personal injuries are caused by electricshock as a result of making contact with metallicmembers that are normally not energized and nor-mally can be expected to remain non-energized. Tominimize the voltage potential between noncurrent-carrying parts of the installation and earth to a safevalue under all systems operations (normal and ab-normal), an installation grounding plan is required.

d. System grounding. There are many methods ofsystem grounding used in industrial and commer-cial power systems (refer to fig 2-2), the major onesbeing:

(1) Ungrounded.(2) Solidly grounded.(3) Resistance grounding: low-resistance, high-

resistance.

-

(4) Reactance grounding.e. Technically, there is no generally accepted use

of any one particular method. Each type of systemgrounding has advantages and disadvantages. Fac-tors which influence the choice of selection include:

(1)(2)(3)(4)(5)(6)(7)

Voltage level of the power system.Transient overvoltage possibilities.Type of equipment on the system.Cost of equipment.Required continuity of service.Quality of system operating personnel.Safety considerations, including fire hazard

and othersf. An ungrounded system is a system in which

there is no intentional connection between the neu-tral or any phase and ground. “Ungrounded system”literally implies that the system is capacitivelycoupled to ground.

(1) The neutral potential of an ungrounded sys-tern under reasonably balanced load conditions will

-


VOLTAGERELAY

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Figure 2-2. Types of system grounding.A) UNGROUNDED GENERATOR, B) SOLIDLY GROUNDED, C) LOW RESISTANCE GROUNDING,

D) HIGH RESISTANCE GROUNDING

be close to ground potentials because of the ca-pacitance between each phase conductor andground. When a line-to-ground fault occurs onan ungrounded system, the total ground faultcurrent is relatively small, but the voltage to groundpotential on the unfaulted phases can reach anunprecedented value. If the fault is sustained,the normal line-to-neutral voltage on the un-faulted phases is increased to the system line-to-

line voltage (i.e., square root of three (3) timesthe normal line-to-neutral value). Over a period oftime this breaks down the line-to-neutral insulationand results in insulation failure. Ungrounded sys-tem operation is not recommended because of thehigh probability of failures due to transientover-voltages (especially in medium voltage i.e., 1kilovolt (Kv)-15 Kv) caused by restriking groundfaults.

2-5


(2) Overvoltage limitation is particularly im-portant in systems over 1 Kv, because equipment inthese voltage classes are designed with less marginbetween 50/60 Hz test and operating voltages thanlow voltage equipment. The remaining variousgrounding methods can be applied on systemgrounding protection depending on technical andeconomic factors. The one advantage of an un-grounded system that needs to be mentioned is thatit generally can continue to operate under a singleline-to-ground fault without significant damage toelectrical equipment and without an interruption ofpower to the loads.

g. A solidly grounded system refers to a system inwhich the neutral, or occasionally one phase, is con-nected to ground without an intentional interveningimpedance. On a solidly grounded system, in con-trast to an ungrounded system, a ground fault onone phase will result in a large magnitude of groundcurrent flow but there will be no increase in voltageon the unfaulted phase.

(1) On low-voltage systems (1 Kv and below),the National Electrical Code (NEC) Handbook, ar-ticle 250-5(b) requires that the following class ofsystems be solidly grounded:

(a) Where the system can be so groundedthat the maximum voltage to ground on the un-grounded conductors does not exceed 150 volts.

(b) Where the system is 3 phase, 4 wire wyeconnected in which the neutral is used as a circuitconductor.

(c) Where the system is 3 phase, 4 wire deltaconnected in which the midpoint of one phase wind-ing is used as a circuit conductor.

(d) Where a grounded service conductor isuninsulated in accordance with the exceptions toNEC articles 230-22, 230-30, and 230-41.

(2) Solid grounding is mainly used in low-voltage distribution systems (less than 1000 volt (V)system) and high-voltage transmission systems(over 15 Kv). It is seldom used in medium-voltagesystems (1 Kv to 15 Kv). Solid grounding has thelowest initial cost of all grounding methods. It isusually recomrrended for overhead distribution sys-tems supplying transformers protected by primaryfuses. However, it is not the preferred scheme formost industrial and commercial systems, again be-cause of the severe damage potential of high-magnitude ground fault currents.

(3) In most generators, solid grounding maypermit the maximum ground fault current from thegenerator to exceed the maximum 3-phase fault cur-rent which the generator can deliver and for whichits windings are braced. This situation occurs whenthe reactance of the generator is large in compari-son to the system reactance. National Electrical

2-6

Manufacturers Association 1-78 places a require-ment on the design of synchronous generators thattheir windings shall be braced to withstand themechanical forces resulting from a bolted 3-phaseshort circuit at the machine terminals. The currentcreated by a phase-to-ground fault occurring closeto the generator will usually exceed the 3-phasebolted fault current. Due to the high cost of genera-tors, the long lead time for replacement, and systemimpedance characteristics, a solidly grounded neu-tral is not recommended for generators rated be-tween 2.4 Kv and 15 Kv.

(4) Limiting the available ground fault currentby resistance grounding is an excellent way to re-duce damage to equipment during ground fault con-ditions, and to eliminate personal hazards and elec-trical fire dangers. It also limits transientovervoltages during ground fault conditions. Theresistor can limit the ground fault current to a de-sired level based on relaying needs.

h...Low-resistance grounding refers to a system inwhich the neutral is grounded through a consider-ably smaller resistance than used for high-resistance grounding. The resistor limits groundfault current magnitudes to reduce the damage dur-ing ground faults. The magnitude of the groundingresistance is selected to detect and clear the faultedcircuit. Low-resistance grounding is used mainly onmedium voltage systems (i.e., 2.4 Kv to 15 Kv),especially those which have directly connected ro-tating apparatus. Low-resistance grounding is notused on low-voltage systems, because the limitedavailable ground fault current is insufficient to posi-tively operate series trip units.

(1) Low-resistance grounding normally limitsthe ground fault currents to approximately 100 to600 amps (A). The amount of current necessary forselective relaying determines the value of resistanceto be used.

(2) At the occurrencee of a line-to-ground faulton a resistance-grounded system, a voltage appearsacross the resistor which nearly equals the normalline-to-neutral voltage. of the system. The resistorcurrent is essentially equal to the current in thefault. Therefore, the current is practically equal tothe line-to-neutral voltage divided by the number ofohms of resistance used.

i. High-resistance grounding is a system in whichthe neutral is grounded through a predominantlyresistive impedance whose resistance is selected toallow a ground fault current through the resistorequal to or slightly more than the capacitive charg-ing current (i.e., I, > 31,,) of the system. The resis-tor can be connected either directly from neutral toground for wye type systems where a system neu-tral point exists, or in the secondary circuit of a


grounding transformer for delta type systems wherea system neutral point does not exist. However,because grounding through direct high-resistanceentails having a large physical resistance size witha continuous current rating (bulky and very costly),direct high-resistance grounding is not practicaland would not be recommended. High-resistancegrounding through a grounding transformer is costeffective and accomplishes the same objective.

(1) High-resistance grounding accomplishesthe advantages of ungrounded and solidly groundedsystems and eliminates the disadvantages. It limitstransient overvoltages resulting from single phaseto ground fault, by limiting ground fault currents toapproximately 8 A. This amount of ground faultcurrent is not enough to activate series over-currentprotective devices, hence no loss of power to down-stream loads will occur during ground fault condi-tions.

(2) Special relaying must be used on a high-resistance grounded system in order to sense that aground fault has occurred. The fault should then belocated and removed as soon as possible so that ifanother ground fault occurs on either of the twounfaulted phases, high magnitude ground fault cur-rents and resulting equipment damage will not oc-cur.

(3) High-resistance grounding is normally ap-plied on electrical systems rated 5kV and below. Itis usually applied in situations where:

(a) It is essential to prevent unplanned sys-tem power outages.

(b) Previously the system has been operatedungrounded and no ground relaying has been in-stalled.

(4) NEC Articles 250-5 Exception No. 5 and250-27 have specific requirements for high imped-ance grounding for system voltages between 480and 1000 Vi For those system voltages the followingcriteria apply:

(a) The conditions of maintenance and su-pervision assure that only qualified persons willservice the installation.

(b) Continuity of power is required.(c) Ground detectors are installed on the sys-

tem.(d) Line-to-neutral loads are not served.

(5) Depending on the priority of need, high re-sistance grounding can be designed to alarm only orprovide direct tripping of generators off line in orderto prevent fault escalation prior to fault locatingand removal. High-resistance grounding (arrangedto alarm only) has proven to be a viable groundingmode for 600 V and 5 kV systems with an inherenttotal system charging current to ground (31,J ofabout 5.5 A or less, resulting in a ground fault cur-

rent of about 8 A or less. This, however, should notbe construed to mean that ground faults of a mag-nitude below this level will always allow the suc-cessful location and isolation before escalation oc-curs. Here, the quality and the responsiveness ofthe plant operators to locate and isolate a groundfault is of vital importance. To avoid high transientovervoltages, suppress harmonics and allow ad-equate relaying, the grounding transformer and re-sistor combination is selected to allow current toflow that is equal to or greater than the capacitivecharging current.

j. Ground fault current can be reduced in distri-bution systems which are predominantly reactivethrough reactance grounding. A reactor is connectedbetween the generator neutral and ground. Themagnitude of the ground fault is directly related tothe reactor size. The reactor should be sized suchthat the current flow through it is at least 25 per-cent and preferably 60 percent of the three phasefault current. Because of the high level of groundfault current relative to resistance grounded sys-tems, reactance grounded systems are only used onhigh reactance distribution systems.

k. Whether to group or individually ground gen-erators is a decision the engineer is confronted withwhen installing generator grounding equipment.Generators produce slightly non-sinusoidal voltagewaveforms, hence, circulating harmonic currentsare present when two or more generating units withunequal loading or dissimilar electrical characteris-tics are operated in parallel.

(1) The path for harmonic current is estab-lished when two or more generator neutrals aregrounded, thus providing a loop for harmonic circu-lation. Because of the 120” relationship of otherharmonics, only triple series (3rd, 9th, 15th, etc.)harmonic currents can flow in the neutral. Har-monic current problems can be prevented by: elimi-nating zero sequence loops (undergrounding thegenerator neutrals); providing a large impedance inthe zero sequence circuit to limit circulating cur-rents to tolerable levels (low or high resistancegrounding the generator neutrals); connecting thegenerator neutrals directly to the parallelingswitchgear neutral bus and grounding the bus atone point only; or, grounding only one generatorneutral of a parallel system.

(2) An effective ground grid system in powerplants or substations is highly important and onethat deserves careful analysis and evaluation. Theprimary function of a ground grid is to limit volt-ages appearing across insulation, or between sup-posedly non-energized portions of equipment orstructures within a person’s reach under groundfault conditions. Reducing the hazard ensures the

2-7


safety and well being of plant personnel or the pub-lic at large. A ground grid system should also pro-vide a significantly low resistance path to groundand have the capability to minimize rise in groundpotential during ground faults.

(3) The conductive sheath or armor of cablesand exposed conductive material (usually sheetmetal) enclosing electrical equipment or conductors(such as panelboards, raceways, busducts, switch-boards, utilization equipment, and fixtures) must begrounded to prevent electrical shock. All parts of thegrounding system must be continuous.

(4) Personnel should verify that grounding forthe system is adequate by performing ground resis-tance tests.

(5) The ground grid of the plant should be theprimary system. In some cases a metallic under-ground water piping system may be used in lieu of aplant ground grid, provided adequate galvanic andstray current corrosion protection for the piping isinstalled, used and tested periodically. This practiceis not acceptable in hazardous areas and is notrecommended if the piping system becomes sacrifi-cial.

(6) The plant ground grid should have a systemresistance of 10 ohms or less. Ground grid systemresistance may be decreased by driving multipleground electrode rods. A few rods, deeply driven andwidely spaced, are more effective than a large num-ber of short, closely spaced rods. Solid hard copperrods should be used, not copperplated steel. Whenlow resistance soils are deep, the surface extensionrods may be used to reach the low resistance stra-tum. Bonding of ground conductors to rods shouldbe by permanent exothermic weld (preferred) orcompression sleeve, and not by bolted clamp (corro-sion results in high resistance connection). Resis-tance at each rod in a multiple system should notexceed 15 ohms.

(7) Reliable ground fault protection requiresproper design and installation of the grounding sys-tem. In addition, routine maintenance of circuit pro-tective equipment, system grounding, and equip-ment grounding is required (refer to groundresistance testing, chap 7).

(8) Equipment grounding refers to the methodin which conductive enclosures, conduits, supports,and equipment frames are positively and perma-nently interconnected and connected to the ground-ing system. Grounding is necessary to protect per-sonnel from electric shock hazards, to provideadequate ground fault current-carrying capabilityand to contribute to satisfactory performance of theelectrical system. Electrical supporting structureswithin the substation (i.e., metal conduit, metal

2-8

cable trays, metal enclosures, etc.) should be electri-cally continuous and bonded to the protectivegrounding scheme. Continuous grounding conduc-tors such as a metallic raceway or conduit or desig-nated ground wires should always be run from theground grid system (i.e., location of generators) todownstream distribution switchboards to ensureadequate grounding throughout the electrical distri-bution system. Permanent grounding jumper cablesmust effectively provide a ground current path toand around flexible metallic conduit and removablemeters. Shielded cables must be grounded permanufacturers’ requirements. Shielded coaxialcable requires special grounding depending on useand function. A voltmeter must be used for detectingpotential differences across the break in a bondingstrap or conductor before handling.

__

(9) A typical grounding system for a buildingcontaining heavy electrical equipment and relatedapparatus is shown in figure 2-3. The illustrationshows the following:

(a) Grounding electrodes (driven into theearth) to maintain ground potential on all con-nected conductors. This is used to dissipate (into theearth) currents conducted to the electrodes.

(b) Ground bus (forming a protective ground-ing network) which is solidly connected to thegrounding electrodes.

(c) Grounding conductors (installed as neces---

sary) to connect equipment frames, conduits, cabletrays, enclosures, etc., to the ground bus.

(10) Radio frequency interference (RFI) is in-terference of communications transmission and re-ception caused by spurious emissions. These can begenerated by communications equipment, switchingof DC power circuits or operations of AC generation,transmission, and power consumers. The fre-quencies and sources of RFI can be determined bytests. Proper enclosures, shielding and grounding ofAC equipment and devices should eliminate RFI.RFI can be carried by conductive material or bebroadcast. Lamp ballasts, off-spec radio equipmentand certain controls may be the prime suspects. Theradio engineer or technician can trace and recom-mend actions to eliminate or suppress the emis-sions. Pickup of RFI can also be suppressed by in-creasing the separation distance between power andcommunication conductor runs.

2-9. Load shedding.Load shedding is sometimes required during emer-gency situations or while operating from an auxil-iary power source in order to ensure enough powergets to the critical circuits (such as the circuits re-quired for classified communications or aircraft


5GROUNDING ELECTRODE

CONFIGURATION-LESS THAN IO FT

Figure 2-3. Typical grounding system for a building.

flight control). Emergency situations include thehandling of priority loads during power “brown-outs” and sharing load responsibilities with primepower sources during “brown-outs”. Usually loadshedding consists of a documented plan that in-cludes a method for reducing or dropping power tononcritical equipment. This plan should include anupdated schematic for load shedding reference and“Truth Table” to ensure correct sequencing of drop-ping and restoring loads on the system. Plans forload shedding are part of the emergency operatinginstructions and vary from one facility to another.The extent of load shedding and the sequence ofdropping loads and restoring to normal are also

. contained in the plan.

2-10. Components.

Standards for selection of components for an auxil-iary power plant are usually based on the electricalloads to be supplied, their demand, consumption,voltage, phase, and frequency requirements. Also tobe considered are load trend, expected life of the

project and of the equipment, fuel cost and avail-ability, installation cost, and personnel availabilityand cost. Factors related to prime movers must alsobe considered: the diesel because of its relativelylow cost and good reliability record, as well as itsability to use liquid or gaseous fuel; the gas turbinefor permanent standby plants because it is rela-tively compact in relation to its high generatingcapacity (desirable if the anticipated power con-sumption rate is high). The components of the typi-cal power systems are briefly described in the fol-lowing paragraphs.

a. Prime movers are reciprocating engines, gasturbines, or other sources of mechanical energyused to drive electric generators.

b. Governors control and regulate engine speed.A governor must be capable of regulating enginespeed at conditions varying between full-load andno-load and controlling frequency.

c. Generators are machines (rotating units) thatconvert mechanical energy into electrical energy.

2-9


d. Exciters are small supplemental generatorsthat provide DC field current for alternating cur-rent generators. Either rotating or static-type excit-ers are used.

e. Voltage regulators are devices that maintainthe terminal voltage of a generator at a predeter-mined value.

f. Transfer switches are used to transfer a loadfrom one bus or distribution circuit to another, or toisolate or connect a load. The rating of the switch orbreaker must have sufficient interrupting capacityfor the service.

g. Switchgear is a cabinet enclosure containingdevices for electric power control and regulation,and related instrumentation (meters, gauges, andindicator lights).

h. Instrumentation senses, indicates, may record

-

and may control or modulate plant electrical, ther-mal and mechanical information essential forproper operation. It may also provide an alarm toindicate an unacceptable rate of change, a warningof unsatisfactory condition, and/or automatic shut-down to prevent damage.


CHAPTER 3

PRIME MOVERS

3-1. Mechanical energy.A prime mover is an engine that converts hydraulic,chemical, or thermal energy to mechanical energywith the output being either straight-line or rotarymotion. Rotary mechanical energy is used to driverotary generators to produce electrical energy. Overthe last 125 years, the internal combustion engine,steam turbine and gas turbine have displaced thesteam engine. Auxiliary electrical generators aretoday usually driven by either reciprocating engineor gas turbine. These are available in wide ranges ofcharacteristics and power rating, have relativelyhigh thermal efficiency and can be easily startedand brought on line. In addition, their speed can beclosely regulated to maintain alternating currentsystem frequency.

-

a. Fuel is burned directly in the internal combus-tion engine. The burning air/fuel mixture liberatesenergy which raises the temperature of the mixtureand, in turn, causes a pressure increase. In thereciprocating or piston engine this occurs once foreach power stroke. The pressure accelerates the pis-ton and produces work by turning the crankshaftagainst the connected load.

(1) Reciprocating spark ignition (SI) engines.These engines operate on the Otto Cycle principletypical for all reciprocating SI engines. The eventsare:

(a) Intake stroke. A combustible fuel/air mix-ture is drawn into the cylinder.

(b) Compression stroke. The temperatureand pressure of the mixture are raised.

(c) Power (expansion) stroke. Ignition of thepressurized gases results in combustion, whichdrives the piston toward the bottom of the cylinder.

(d) Exhaust stroke. The burned gases areforced out of the cylinder.

(2) Four strokes of the piston per cycle are re-quired (four-stroke cycle or four-cycle). One powerstroke occurs in two revolutions of the crankshaft.

(3) The outpu o an engine can be increasedt fwith some loss in efficiency by using a two-stroke(two-cycle) Otto process. During the compressionstroke, the fuel/air mixture is drawn into the cylin-der. During the power stroke, the mixture in thecylinder is compressed. Near the end of the powerstroke, burned gases are allowed to exhaust, andthe pressurized new mixture is forced into the cyl-inder prior to the start of the next compressionstroke.

(4) In the Otto cycle, the fuel/air mixture iscompressed and ignited by a timed spark. The exactratio of fuel to air is achieved by carburization of avolatile fuel. Fuel injection is also in use in the Ottocycle to achieve more precise fuel delivery to eachcylinder.

(5) Four-cycle SI gasoline engines are used asprime movers for smaller portable generator drives(see fig 3-l). The advantages are:

(a) Low initial cost.(b) Light weight for given output.(c) Simple maintenance.(d) Easy cranking.(e) Quick starting provided fuel is fresh.(f) Low noise level.

(6) The disa vantagesd of using four-cycle SIgasoline engines are:

(a) Greater attendant safety hazards due touse of a volatile fuel.

(b) Greater specific fuel consumption thancompression ignition (CI) engines.

(7) Reciprocating CI engines. These operate onthe Diesel Cycle principle typical for all CI engines.The-events are:

(a) Intake stroke. Air is drawn into the cylin-der.

(b) Compression stroke. Air is compressed,raising the pressure but ‘also raising the tempera-ture of the air above the ignition temperature of thefuel to be injected.

(c) Power stroke. A metered amount of fuel atgreater-than-cylinder-pressure is injected into thecylinder at a controlled rate. The fuel is atomizedand combustion occurs, further increasing pressure,thus driving the piston which turns the crankshaft.

(d) Exhaust stroke. The burned gas is forcedfrom the cylinder.

(8) As with the SI four-cycle engine, the fourcycles of the CI engine occur during two revolutionsof the crankshaft, and one power stroke occurs inevery two revolutions.

(9) The CI or diesel engine may also use two-d’cycle operation with increased output but at lowerengine efficiency.

(10) In the Diesel cycle, only air is compressedand ignition of the fuel is due to the high tempera-ture of the air. The CI engine must be more stoutlyconstructed than the SI engine because of thehigher pressures. The CI engine requires high-pressure fuel injection.

3-1

TM 5-685/NAVFAC MO-9 12

Figure 3-l. emergency

b. Gas turbine engine. The fuel and air burn in acombustion chamber in the gas turbine engine. Theresulting high-pressure gases are directed throughnozzles toward the turbine blades and produce workby turning the turbine shaft. This is a continuousprocess in the continuous-combustion or constant-pressure gas turbine.

(1) Gas tu br ines operate on the Brayton Cycleprinciple. While a number of configurations areused for aircraft propulsion (turbofan, turboprop,etc.), the one used as a prime mover for auxiliariesis generally the continuous combustion gas turbine.In this process, air is compressed by an axial flowcompressor. A portion of the compressed air is mixedwith fuel and ignited in a combustion chamber. Thebalance of the compressed air passes around thechamber to absorb heat, and then it is merged withthe burned products of combustion. The pressurizedmixture, usually at 1000°F or higher, flows into areaction turbine.

(2) The turbine drives the compressor and alsoproduces work by driving the generator. A portion ofthe exhaust gas may be recirculated and it is pos-sible to recover heat energy from the waste exhaust.The compressor uses a relatively large portion ofthe thermal energy produced by the combustion.The engine efficiency is highly dependent on theefficiencies of the compressor and turbine.

(3) The advantages of using a gas turbine are:(a) Proven dependability for sustained op-

eration at rated load.(b) Can use a variety of liquid and gaseous

fuels.(c) Low vibration level.

(d) High efficiency up to rated load.(4) The disadvantages of using a gas turbine

are:(a) Initial cost is high.(b) Fuel and air filtering are required to

avoid erosion of nozzles and blades.(c) Fine tolerance speed reducer between tur-

bine and generator is required and must be kept inalignment.

(d) Specialized maintenance, training, toolsand procedures are required.

(e) Considerable energy is required to spinfor start.

(f) High frequency noise level.(g) Exhaust volume is considerable.(h) A large portion of the fuel heat input is

used by the compressor.(i) A long bedplate is required.(j) Maximum load is sharply defined.(h) Efficiency is lower than reciprocating en-

gines.c. Rotary spark ignition engines. These engines

are typified by the Wankel-type engine operating onthe Otto principle. Each of the four cycles occurs ina specific sector of an annular space around the axisof the shaft. The piston travels this annular cham-ber and rotates the shaft. The power stroke occursonce in every shaft revolution, dependent on thedesign of the engine. This engine can produce alarge amount of power for a given size. The highrpm, low efficiency, friction and sealing problems,and unfavorable reliability of this engine make itunsatisfactory as a prime mover for auxiliary gen-erators. These faults may be corrected as the devel-opment continues.

__

3-2. Diesel engines.Diesel engines for stationary generating units aresized from 7.5 kW to approximately 1500 kW anddiesel engines for portable generating units aresized from 7.5 kW to approximately 750 kW. Seefigures 3-2 through 3-4. Efficiency, weight perhorsepower, and engine cost relationships are rela-tively constant over a wide range of sizes. Smallerengines, which operate in the high-speed range(1200 and 1800 rpm), are used for portable unitsbecause of their lighter weight and lower cost. Low-and medium-speed (200 and 900 rpm) engines arepreferred for stationary units since their greaterweight is not a disadvantage, and lower mainte-nance cost and longer life offset the higher initialcost.

a. The advantages of diesel engines include:(1) Proven dependability for sustained opera-

tion at rated load.(2) Efficiency.

3-2


Figure 3-2 Typical small stutionary dieselgenerator unit, air cooled

(3) Adaptability for wide range of liquid fuels.(4) Controlled fuel injection.

b. The disadvantages include:(1) High initial cost.(2) High weight per given output.(3) High noise level.(4) Specialized maintenance.(5) Fuel injection system has fine mechanical

tolerances and requires precise adjustment.(6) Difficult cranking.(7) Cold starting requiring auxiliary ignition

aids.(8) Vibration.

3-3. Types of Diesel Engines.Various configurations of single and multiple dieselengines, either two-cycle or four-cycle are used todrive auxiliary generators. Multi-cylinder enginesof either type can be of “V” or in-line configurations.

--

Figure 3-3. Typical large stationary diesel generator unit.

3-3


Figure 3-4. Typical diesel power plant on transportable frame base.

The “V” configuration is favored when there is alack of space because “V” engines are shorter andmore compact than in-line engines. Most engines inuse are liquid-cooled. Air cooling is sometimes usedwith single-cylinder and other small engines (driv-ing generators with up to 10 kW output). Air-cooledengines usually reach operating temperaturequickly but are relatively noisy during operation.

a. Two cycle. The series of events that take placein a two-cycle diesel engine are: compression, com-bustion, expansion, exhaust, scavenging, and air in-take. Two strokes of the piston during one revolu-tion of the crankshaft complete the cycle.

(1) Compression. The cycle begins with the pis-ton in its bottom dead center (BDC) position. Theexhaust valve is open permitting burned gases toescape the cylinder, and the scavenging air port isuncovered, permitting new air to sweep into thecylinder. With new air in the cylinder, the pistonmoves upward. The piston first covers the exhaust

3-4

port (or the exhaust valve closes), then the scaveng-ing air port is closed. The piston now compressesthe air to heat it to a temperature required forignition as the piston nears top dead center (TDC).As the piston nears TDC, a metered amount of fuelis injected at a certain rate. Injection atomizes thefuel, which is ignited by the high temperature, andcombustion starts. Combustion causes the tempera-ture and pressure to rise further.

(2) Power: As the piston reaches and passesTDC, the pressure of the hot gas forces and acceler-ates the piston downward. This turns the crank-shaft against the load connected to the shaft. Thefuel/air mixture continues to burn. As the pistonpasses eighty percent (80%) to eighty-five percent(85%) of the stroke travel towards BDC, it uncoversthe exhaust port (or the exhaust valve is opened).This allows exhaust gas to escape from the cylinder.As the piston continues downward, it uncovers thescavenging air port, allowing scavenging air (fresh


-.-

air at 3 pounds per square inch (psi) to 6 psi) tosweep the cylinder, further purging the exhaust gasand providing a fresh clean charge for the nextcycle. The piston reaches and passes through BDC.The compression stroke then begins again.

b. Four-cycle. The series of events taking place ina four-cycle engine are: inlet stroke, compressionstroke, expansion or power stroke, and exhauststroke. Four strokes (two revolutions of the crank-shaft) are necessary to complete the cycle.

(1) Inlet stroke. As the piston starts downwardfrom TDC, the inlet (intake) valve opens and allowsthe piston to suck a charge of fresh air into thecylinder. This air may be supplied at a pressurehigher than atmospheric air by a supercharger.

(2) Compression stroke. As the piston nearsBDC, the air inlet valve closes, sealing the cylinder.Energy supplied by the crankshaft from a flywheel,or power from other cylinders, forces the piston up-ward toward TDC, rapidly compressing the air andincreasing the temperature and pressure within thecylinder.

(3) Power stroke. As the piston approachesTDC, an amount of fuel (modulated by the governor)is injected (sprayed and atomized) into the cylinderwhich is ignited by the high temperature, and com-bustion starts. Combustion, at a controlled rate,further increases the temperature and pressure toaccelerate the piston toward BDC. The expansion ofthe hot gases forces the piston down and turns thecrank against the load. Engine efficiency dependson the fuel charge being completely burned duringthe power stroke.

(4) Exhaust stroke. As the piston passesthrough BDC at the end of the power stroke, theexhaust valve opens. The piston, using stored en-ergy from the flywheel or from the power stroke ofanother cylinder, forces the burned gases from thecylinder through the exhaust port. As the pistonapproaches TDC, the exhaust valve is closed andthe air intake valve opens to begin another cycle.

‘-__

c. Engine timing. Engine timing is critical. Intakeand exhaust valves have to open and close to allowthe greatest amount of work to be extracted fromcombustion. They must also be open long enough toallow fresh air to flow into and exhaust gas to flowout of the cylinder. Fuel must be injected at properrates during certain periods of time to get smoothpressure rise and complete combustion. Timing fortwo-stroke cycle and four-stroke cycle engines dif-fers (refer to the timing diagrams in fig 3-5). Dia-gram A illustrates two forms of the two-stroke cycleengine. The inner portion covers the typical crank-case scavenging type with uncontrolled fixed ports.

~cAv?~Z~~Z~ERIO~EXHAUST BlDW

A .

FUEL INJECTORV A L V E O P E N S

AIR STARTING

V A L V E O P E N S 7

COMPRESS10V A L V E O P E N

O V E R L A P - b AIR S T A R T2 V A L V E C L O S E S

Figure 3-5. Timing diagramsA) FOR A TWO STROKE CYCLE,

B) FOR A FOUR STROKE CYCLE.

The outer portion covers a port control (uniflow)system. Diagram B illustrates timing for a four-stroke cycle engine.

3-5


d. Advantages. Advantages of diesel power forgenerating units include the ability: to utilize spe-cific liquid or gaseous fuel other than highly volatilerefined ones (gasoline, benzene, etc.); to meet loadby varying the amount of fuel injected; to utilize arelatively slow design speed; and, to operate with-out external furnaces, boilers or gas generators.

e. Disadvantages. Major disadvantages include: aneed to reduce cranking power by use of compres-sion relief during start and a powerful auxiliarystarting engine or starting motor and battery bank;high-pressure, close-tolerance fuel injection systemscapable of being finely adjusted and modulated forspeed/load control; weight; and, noise.

3-4. Diesel fuel system.A typical diesel engine fuel system is shown in fig-ure 3-6. Information related to cooling, lubrication,and starting systems is also shown. Functional re-quirements of a diesel engine fuel system includefuel injection, injection timing, and fuel pressuriza-tion.

a. Fuel injection system. This system measuresand meters fuel supplied to each cylinder of theengine. Either inlet metering or outlet metering isused. In inlet metering, fuel is measured within theinjector pump or injector. In outlet metering, fuel ismeasured as it leaves the pumping element. Instan-taneous rate during injection must deliver fuel toattain correct propagation of the flame front andresulting pressure rise.

b. Timing. Fuel injection timing is critical. Theduration of fuel injection and the amount of fuelinjected vary during starting and partial, full, oroverload conditions, as well as with speed. The bestengine start occurs when fuel is injected at (or justbefore) TDC of piston travel because air in the com-bustion chamber is hottest at that instant. Duringengine operation, the injection timing may need tobe advanced to compensate for injection lag. Manymodern injection systems have an automatic injec-tion timing device that changes timing to matchchanges in engine speed.

c. Fuel pressurization. Fuel must be pressurizedto open the injector nozzle because the nozzle (orinjector tip) contains a spring-loaded check valve.The injection pressure must be greater than thecompression pressure within the compressionchamber or cylinder. Between 1500 psi and 4000 psipressure is required for injection and proper fuelatomization. Specific information is provided in theengine manufacturer’s literature. Fuel system com-ponents are listed in paragraph 3-4c.

d. Fuel contamination. Fuel injection equipmentis manufactured to precision accuracy and must bevery carefully handled. A small amount of abrasive

3-6

material can seriously damage moving parts. Con-taminated fuel is a major vehicle by which dirt andwater enter the system. Fuel must be filtered beforeuse.

e. Starting fuels. Diesel engines used for auxil-iary generators usually use distillate fuel forquicker starting. These fuels are light oils that aresimilar to kerosene. Various additives are fre-quently used with fuel such as cetane improverswhich delay ignition for smoother engine operation,corrosion inhibitors, and dispersants. Appendix Ccontains information related to fuel and fuel stor-age.

f. Injection systems. Diesel engine manufacturersusually use one of the following types of mechanicalfuel injection systems: unit injection, common railinjection, or in-line pump and injection nozzle. Alimited number of diesel engines currently in useemploy a common rail injection system. Electronicfuel injection has been developed for use in moderndiesel engines refer to paragraph 3-4b(4). Unit in-jector, common rail injector, and in-line pump andinjection nozzle systems are described in tables 3-1through 3-3. Injection of fuel in any system muststart and end quickly. Any delay in beginning injec-tion changes the injection timing and causes hardstarting and rough operation of the engine. Delay inending injection is indicated by heavy smoke ex-haust and loud, uneven exhaust sounds. The end ofinjection (full shutoff) should be total with nodribble or secondary injections. Some injection sys-tems include a delivery or retraction valve for fuelshutoff. In other systems, camshafts have cam lobesdesigned with a sharp drop to assure rapid fuelshutoff.

(1) Common rail injection. The common rail in-jection system is an older system where fuel is sup-piied to a common rail or manifold. A high-pressurepump maintains a constant pressure in the railfrom which individual fuel lines connect to the in-jection or spray nozzle at each cylinder. Fuel isdrawn from the supply tank by the low-pressurepump and passed through a filter to the suction sideof the high-pressure pump. The high-pressure pumpraises the fuel to the engine manufacturer’s speci-fied operating pressure. Constant pressure is main-tained in the system by the high pressure pump andrelated relief valve. If pressure is greater than therelief valve setting, the valve opens and permitssome of the fuel to flow back (bypass) into the tank.Check valves in the injection nozzle prevent thereturn of fuel oil to the injection system by cylindercompression pressure.

(2) Unit injection. This system consists of anintegral fuel-injector pump and injector unit. A com-plete unit is required for each cylinder. Fuel oil is

_-


Figure 3-6. Diagram of typical fuel, cooling, lubrication, and starting systems.

3-7


Table 3-l. Unit injector system.

Component Purpose

Gear pump

Injector

Filters

Low pressure pump; delivers fuel from tank toinjector: fuel also lubricates the pump.

Meters, times, and pressurizes fuel: camshaft-operated by pushrod and rocker arm; one injec-tor for each cylinder.

Protect machined components from dirt andwater in fuel.

Governor Controls engine speed. Varies position of theinjector plunger to vary amount of fuel in-jected.

Table 3-2. Common rail injector system.

Component Purpose

Low andhigh-pressure pump

Governor

Throttle

Injector

Filters

Low-pressure pump delivers fuel from tank tohigh-pressure pump; high-pressure pump deliv-ers fuel to injectors at the desired operatingpressure: fuel lubricates governor and pumps.

Flyweight-type; controls maximum fuel pres-sure; prevents engine overfueling; controls en-gine idle and prevents overspeeding by control-ling fuel supply: contained within main pumphousing.

Controlled by the operator; regulates fuel flowand pressure to injectors.

Meters, times and pressurizes fuel; camshaft-operated by pushrod and rocker arm: one injec-tor for each cylinder.

Protect machined components from dirt andwater in fuel.

Table 33. In-line pumps and injection nozzle system.

Injection pump Meters, times, pressurizes and controls fueldelivered to the injection nozzles; consists ofsingle pumping element for each cylinder; tit-ted into a common housing; operated by rockerarm or directly from the camshaft.

Governor Usually the flyweight-type: may be mounted onmain injection pump housing; controls fuel de-livery: variable-speed or limiting-speed type isused.

Fuel lines High-pressure type; transports fuel from pumpto injection nozzles.

Injection nozzle Spring-loaded; hydraulically operated valve thatis inserted in the combustion chamber: onenozzle for each cylinder.

Filters Protect machined components from dirt andwater in fuel.

supplied to the cylinders by individual pumps oper-ated from cams located on a camshaft or on anauxiliary drive. The pumps operate independently

3-8

of each other. Fuel from the supply tank is passedthrough a filter to the injector pump supply pipe.The injector pump receives the fuel which is theninjected into the cylinders in proper quantity and ata prearranged time.

(3) Electronic Fuel Injection. The electronicfuel injection system is an advanced design for mod-ern diesel engines, intended to produce improvedstarting and operating characteristics. Several sys-tems have been developed, mainly for smaller andintermediate-sized engines. Similarities to me-chanical injection systems include the following: afuel pump (or pumps), a governor or speed regula-tor, filters, and fuel injectors. The major differencebetween mechanical and electronic systems is thecomputer which replaces the mechanical compo-nents (cams and pushrods) used to control fuel in-jection. The computer processes data inputs (suchas engine speed and load, desired speed or governorsetting, engine temperature, and generator load).Computer output is precisely timed electrical sig-nals (or pulses) that open or close the fuel injectorsfor optimum engine performance. Adjustment of in-jection timing is seldom required after the initialsetup. Refer to the engine manufacturer’s literaturefor maintenance of injectors, pumps, and other fuelsystem components.

g. The main components of the fuel system. Fuelsupply source, transfer pump, day tank, fuel injec-tion pump, fuel injection nozzles, and filters andstrainers. These components are matched by theengine manufacturer for optimum performance andwarranty protection.

(1) The fuel supply source is one or more stor-age tanks. Each tank must have drain valves forremoval of bottom water, see paragraph 2-4 forgenera! requirements. Additionally, the fuel systemshould include a day tank and a transfer pump, seeparagraph 2-4d.

(2) The following paragraphs cover the fuel in-jection pump, fuel injection nozzles, and filters andstrainers.

(3) A fuel injection pump accomplishes thefunctions described in paragraph 3-4b(3). Addi-tional details are provided in the following para-graphs.

(a) The fuel injection pump must performtwo functions: first, deliver a charge of fuel to theengine cylinder at the proper time in the engineoperating cycle, usually when the piston has almostreached the end of the compression stroke; and sec-ond, measure the oil charge delivered to the injectorso the amount of fuel is sufficient to develop thepower needed to overcome the resistance at thecrankshaft.


(b) The fuel injection pump consists of a bar-rel and a reciprocating plunger. The reciprocatingplunger takes a charge of fuel into the barrel anddelivers it to the fuel-injecting device at the enginecylinder.

(4) Fuel injection nozzles for mechanical injec-tion systems are usually of the spring-loaded,needle-valve type. These nozzles can be adjusted toopen at the predetermined pressure. Consult themanufacturer’s specifications before adjusting fuelinjection valves. The nozzle components are as-sembled carefully at the factory and must never beintermixed. Most manufacturers use an individualpump for each cylinder (pump injection system) andprovide each cylinder with a spring-loaded sprayvalve. The spring keeps the needle from lifting untilthe pump has delivered oil at a pressure greaterthan the spring loading. As soon as the pressurelifts the needle, oil starts to spray into the enginecylinder through an opening in the valve body.

(5) Diesel fu 1e suppliers try to provide cleanfuel. However, contaminants (water, sand, lint, dirt,etc.) are frequently found even in the best grades. Ifforeign material enters the fuel system, it will clogthe nozzles and cause excessive wear of fuel pumpsand injection valves.

(6) Sulphur, frequently found in fuel oil, is veryundesirable. When sulfur is burned (during combus-tion), sulfur dioxide and sulfur trioxide form. Bothsubstances will combine with water condensates toform sulfuric acid. The maximum amount of sulfuracceptable in fuel oil must not exceed one percent.The engine manufacturer’s recommendation shouldbe used if acceptable sulfur in fuel oil requirementsare more restrictive. Strainers and filters capable ofremoving fine particles are placed in the fuel linebetween supply tank and engine, or between enginetransfer pump and injection pump, or sometimes atboth places. The basic rule for placement of strain-ers and filters is strainers before pumps, filters af-ter pumps. A filter should be placed in the storagetank fill line. This prevents accumulation of foreignmaterial in the storage tank. Strainers protect thetransfer pumps. A strainer should also be placedahead of each fuel flow meter. Always locate filtersand strainers where they are easily accessible forcleaning or replacement. Duplex filters should beprovided for engines that run continuously so thatfilter elements can be cleaned while the engine isrunning without interrupting its fuel supply. Pro-vide space under the edge of disk filters for a recep-tacle to receive material drained from the bottom ofthe filter when it is cleaned. If the filter or strainerhas an element that can be renewed or cleaned,space must be allowed to permit its easy removal.Follow the manufacturer’s recommendations on fre-

quency of cleaning and replacing filter elements.Adjust the frequency to meet unusual local operat-ing conditions. Generally, all metal-edge and wire-mesh devices are called strainers, and all replace-able absorbent cartridge devices are called filters.Fuel filters approved for military use consist of re-placeable elements mounted in a suitable housing.Simplex and duplex type fuel filters are available.Fuel strainers and filters must not contain pressurerelief or bypass valves. Such valves provide a meansfor the fuel to bypass the strainer or filter, therebypermitting the fuel-injection equipment to be dam-aged by contaminated fuel. Filter capacity is gener-ally described in terms of pressure drop between theinput and output sides of the filter. However, fuel oilfilters must be large enough to take the full flow ofthe fuel oil pumps with a pressure drop across thefilter not to exceed the engine manufacturer’s speci-fications. Fuel filter elements should be changedwhenever the pressure drop across the filter nearsor reaches a specified value. Refer to manufactur-er’s instructions for information on the replacementof filter elements. Filter capacity at a given pres-sure drop is influenced by the viscosity of the fuel.The filter should have ample capacity to handle fueldemand of the engine at full load. The larger thefilter, the less frequently it will have to be cleanedand the better the filtering performance will be.

3-5. Diesel cooling system.Diesel engines are designed to be either air cooledor liquid cooled. Cooling is used to prevent the cyl-inder walls, the head, the exhaust manifold, and thelube oil from overheating.

a. An air-cooled system depends on an enginedriven fan to blow ambient air over the fluted orfinned surfaces of the cylinder head and through aradiator type oil cooler, and over the exhaust mani-fold. The exterior surfaces must be kept free of dirtor corrosion. The oil must be kept free of sludge tosecure adequate cooling. Air cooling is seldom usedon engines over 5 HP or on multicylinder engines.

b. The liquid-cooled engine uses a treated coolantforced to circulate through passages in and aroundthe cylinder, head, exhaust manifold and a lube oilheat exchanger. The hot coolant is passed throughthe tubes of an air-cooled radiator, through thetubes of an evaporative heat exchanger, or througha shell and tube heat exchanger. A typical liquidsystem is shown in figure 3-7.

(1) Two basic types of liquid-cooling systemsare attached and remote.

(a) Attached. All components are mounted atthe engine. It is used with smaller and/or portableengine generator sets and usually consists of anengine-driven pump circulating treated coolant in a

3-9


METALEDGE

WATER INLET

MAKE UPWATER+-----

ADIATOR

f FAN MOTOR

1 JACK WATER1 TEMPERATUREI REGULATING

fI, I

-_II+- - - - - i_ --I OTHERMOMETER

SUMi’ I ; - k-j.----- & SH U T O f f V A L V E

Figure 3-7. Diesel Engine Liquid Cooling System.

closed circuit through a radiator (engine-driven fan)or a water-cooled heat exchanger.

(b) Remote. Primary coolant in a closed cir-cuit is piped to a heat exchanger system notmounted with the engine. Pumps and controls mayalso be remote. It is used for larger engines wheresize and complexity of heat dissipation systems aresignificant. It is also used to physically separate theliquid processing from the electrical generation andcontrol spaces.

c. System description and operation. Successfuloperation of the engine depends upon the removal ofexcess heat from lubricating oil, after cooler, andthe engine components (cylinders, pistons, andvalves) to keep the engine temperature within thelimits specified by the manufacturer. The kW ratingof the associated electric generator may requirederating when any temperature at the operatingengine exceeds the manufacturer’s limits. Table 3-4describes the various elements of the cooling sys-tem.

(1) Overheating of the engine reduces the effec-tiveness of engine lubricants, accelerates enginewear, and causes engine breakdown. Cooling pre-vents excessive stresses in or between engine partscaused by unequal temperature within the engine.Also, cooling prevents loss of strength caused byoverheating of the engine’s structural metal.

3-10

(2) The engine and its components are de-signed to withstand the mechanical and thermalstresses resulting from operating within certain pa-rameters. The design also allows for the effects oftemperature on the strength, resistance to fatigueand wear, the stresses induced by expansion andcontraction, and allowance for wear and corrosion,etc.

-

(a) Each component subject to heat is de-signed to operate within stated temperature iimits.Unsatisfactory operation, decreased life, damage orfailure will result if the engine operates outside ofthese limits. Lubricants will lose their necessaryproperties, clearances between parts will becometoo great or too little, and combustion of fuel will notbe proper. Fuel, air, exhaust and coolant passagesmay be fouled, melted, or chemically attacked, ormisalignment and excessive vibrations may result.

(b) Hot spots, cold spots, general overheatingand general overcooling can each cause problems.Approximately one-third of the energy consumed byan engine is removed by the cooling system.

(3) An engine used for auxiliary generator ser-vice will be one of proven capability and reliabilitywhen operated within the limits specified by themanufacturer. A particular engine will requirestated rate of coolant flow at certain inlet and outlettemperatures under various rates of fuel energy

-


Table 3-4. Typical cooling system components.

Coolant

Coolant jacketsor passages

Coolant pumps

Thermostat

Fan

Shutters

Heat exchanger

Coolant tower

Evaporative cooler

Treated coolant

Secondary system

Tertiary system

Closed system

The liquid, usually treated water, used to re-move excess heat from the engine. May be pri-mary, secondary. etc.

Spaces surrounding block, cylinders, and heads,through which primary coolant is circulatedunder pressure to cool the engine components.

also decreases heat transfer. It should have goodheat capacity and contain an antifreeze, anti-corrosion compound, and cleaning agent to keepcoolant passages in good condition. The coolantshould neither corrode nor attack any metals ororganic materials of the coolant system. It shouldnot be hazardous.

Water or primary (secondary, other) pump tocirculate coolant (water) through engine pas-sages to heat exchangers.

Regulates coolant flow to maintain engine tem-perature between specified limits.

(4) In rare cases, the engine may be cooled us-ing clean water in a once-through system. Cool wa-ter is pumped through the coolant passages, and thehot water leaving the engine is discarded. This hasmany disadvantages and will not be further dis-cussed.

Provides air movement to cool air-cooled en- (a) Smaller engines may have a single cool-gine or the radiator of a liquid-cooled engine to ant circuit (loop) through which coolant, leaving thecool the coolant for recirculation. engine, passes and is returned to the engine.

Blades used to vary air flow across a radiatorto regulate rate of heat removal from coolant.Would be closed when coolant is below normaltemperature and open when coolant is warm.May be thermostatically controlled.

A device to exchange heat from one medium toanother. Usually a shell and tube-type ex-changer.

(b) Larger engines may require the use ofadditional loops. In these, the engine coolant is in aprimary loop. It is cooled by the medium circulatingin a secondary loop and the secondary coolant maybe cooled by another medium in a tertiary loop. Nocooling medium mixes with another medium inthese “non-contact” systems.

A structure in which hot coolant is sprayed orfalls through air currents. As coolant evaporatesheat is given up by the remaining liquid cool-ant.

A device to remove heat from medium byevaporation of that medium in air (open cir-cuit). May also be by non-contact heat ex-changer from one medium to an evaporatingsecond. Applicable where ambient temperatureand relative humidity are below certain values.

Coolant fluid, usually filtered water with addi-tives to prevent freezing and to inhibit scaleformation and corrosion. Required for primarycoolant circuit. May not be required for sec-ondary or other circuits.

Describes the components of a second systemused to extract heat from the primary heat ex-changer. Used where waste heat may be usedfor building heating, etc.

Describes components of a possible third sys-tern to extract heat from a secondary system.

Coolant does not come in contact with air orother fluids.

(c) An example of a three-loop system istreated engine coolant in the primary loop passingthrough a heat exchanger cooled by freshwater in asecondary loop. The “hot” freshwater may be usedfor building heating or may be passed through an-other heat exchanger cooled by brackish or saltwa-ter in the tertiary circuit on a once-through basis.The purpose of this arrangement is to keep theseawater at low temperatures so that salts do notform scale. Leakage of seawater into the freshwatercircuit is prevented by having the freshwater athigher pressure than the seawater. The freshwatercircuit may operate at higher temperature and re-cover significant usable heat otherwise wasted.Contamination of engine coolant is prevented bybeing at a higher pressure than the freshwater. Theadditives used in the engine coolant are a cost. Verylittle coolant is lost when the coolant circuit issealed. Heat capacity and temperature may be el-evated by using a sealed, pressurized coolant loop.Coolant must be periodically tested to make surecorrect amounts of active additives are present.

consumption and mechanical energy output. Thecoolant must not contain any suspended solids thatcould settle and impede heat transfer or coolantflow. The coolant should be free of entrained ordissolved air or other gases which could cause cor-rosion and decrease heat transfer. The coolantshould not contain dissolved salts’ that could pre-cipitate or form an insulating scale coating which

(d) At the engine the coolant cools the lubri-cating oil, then the lower temperature areas, andfinally the hotter sections.

(e) In the crankcase the oil cools the crank-shaft assembly. Sprayed or splashed oil cools theunderside of the piston. Oil circulated to the cam-shaft, rocker arms, and valve guides picks up heatand drains into the sump. The oil pump forces thehot lube oil through the oil filter and through the oilcooler to the pressure-oiled points. The oil must not

3-11


become so hot that it loses its lubricating propertiesor breaks down.

(f) Coolant leaving the oil cooler flows to thecylinder water jackets, inlet ports and valves, injec-tors, exhaust ports and valves, intercooler or super-charger, turboblower, exhaust manifold jacket, andfinally to the heat exchanger where it is recircu-lated to the engine.

(5) Non-contact heat exchangers are used toadd or remove heat from one medium to anotherwithout intermixing. A radiator or fin-fan cooleruses an airflow to remove and dissipate the heat. Ina heat exchanger, one medium flows through tubesand the second medium flows around the tubes.Generally, the medium having a higher tendency tofoul the exchanger surfaces is inside the tubes toallow easier cleaning. The tubes may form part of asealed system. The tube bundle may be in an opentank or in a shell. The shell, enclosing the secondmedium, may be part of another sealed system.

(6) Cooling towers and evaporative coolers areboth used to dissipate waste heat to the atmo-sphere. They may be used where ambient air issufficiently cool and dry (low relative humidity) toabsorb water vapor. As water is sprayed or dividedinto many small streams, some will evaporate to thepassing air. The heat required to evaporate the wa-ter is approximately 1050 Btu/lb and is extractedfrom the unevaporated water. Additionally, the airwhich is now moist may be warmed by the water (ifthe water was originally warmer than the air), thusremoving more heat from the water. In a coolingtower, the fluid to be cooled is exposed to the air.Approximately eighty percent (80%) of the heat re-moved is due to evaporation. The water leaving thetower or cooler is usually five degrees Fahrenheit(5°F) higher than the entering air. Towers may useatmospheric draft or fans to move the air. Makeupwater is required to replace that lost by evaporationor entrained spray. Water treatment and blowdownare necessary because salts are concentrated by theevaporation. Dust, etc., in the air will contaminatethe exposed water. In an evaporative cooler, thecoolant passes through tubes. The tube bundle liesinside a cooling tower. The cooling tower spray andair movement cool the tubes but do not mix with thecoolant.

(7) Flow rates of fluid, fan speed, flow bypass,etc. are controlled to maintain proper conditions. Aproperly monitored, real-time, automatic controlsystem is preferred over a manually-operated sys-tem, especially where some parts of the engine aux-iliaries are remote or not in direct observation ofoperating personnel. Automatic data logging is ofreal value for determining trends and for trouble-shooting.

3-12

(8) It is necessary to control temperatures atvarious points of the engine and throughout thecooling systems. This may be done by bypassingsome portion of a coolant stream or by changing theflow rate.

(9) Overcooling can cause problems. A warmengine is easier to start and can quickly be broughtup to speed and loaded. Warm oil provides betterinitial oil circulation and lubrication which is vitalin cold weather. Heavy fuel oils must be at a tem-perature related to the viscosity required by the fuelsystem and injectors. The carburetor and inletmanifold of an SI engine must be warm enough toprevent “icing” and to vaporize the fuel/air mixture.Exhaust gas temperature must be kept above thedew point to prevent condensation and corrosion.An engine running cold will not achieve rated effi-ciency. Freezing of the coolant can cause breakageor interfere with required flow and circulation.

(10) Chemical control of the various cooling cir-cuits is important. Strainers and filters remove sus-pended solids. Additives prevent corrosion, mineralscale buildup, organic growth and organic fouling.Periodic sampling and analysis will indicate actualconcentrations of undesired materials dissolved inthe coolants. Comparison of test results will provideguidance for altering the treatment program. Someuntreated freshwater and brackish or seawater pro-mote growth of barnacles, etc., that prevent properflow and pressures. Visual inspection is recom-mended when increasing pressure drops indicatefouling. Physical and/or chemical cleaning may beperiodically required. Safety precautions must befollowed when using most cleaning compounds.

-

3-6. Lubrication system.The bearings and moving parts of all diesel enginesare lubricated by a full-pressure system, see figure3-6. Lubricating oil requirements and specificationsare covered in appendix C.

a. System elements. Smaller engines are usuallyself contained. The smaller engine system will havemany of the system elements used in the largerengines, as follows:

(1) Lube oil having proper properties for thespecific engine design.

(2) Lube oil t kan or sump to hold the volume ofoil required.

(3) Oil feed pump(s) driven from the engine tocirculate clean cool pressurized oil (5 to 75 psi).

(4) Oil feed piping, valves and controls to de-liver oil to various lube points of the engine.

(5) Engine internal oil passageways in thecrankshaft-piston assembly and in block and head.

(6) Hot oil sump to collect oil draining from allthe lubricated engine components.


(7) Hot oil sump pump (returnpump) to force hot used oil throughpurifier and cooler.

oil pump, filterfiltering and/or

(8) Oil filter to remove suspended solids, dirtand sludge.

(9) Sampling valves for taking samples of oiland filter solids periodically for testing and analy-sis.

(10) Transfer systems for adding new oil andremoving used oil from the engine lube system.

(a) Lube oil must have certain properties forspecific application. It must flow properly at theminimum temperatures (pour point), have properviscosity (resistance to shear) between moving partsand retain desired viscosity over the range of tem-peratures in the engine (viscosity index). The oilmust resist oxidation (stability) that forms gum andsludge and the associated catalytic effects of enginemetals present (especially copper and lithium) inthe detergent additives. It must allow sludge par-ticles to disperse and not clump or deposit through-out the engine. It will contain inhibitors to preventoxidation, a dispersing agent and a detergent tokeep surfaces clean.

(b) The physical specifications for crankcaselube oil are not positive indications of suitability.The experience of the engine manufacturer is guid-ance for recommended oils. The user must choose.

(c) Periodic sampling, analysis and evalua-tion of results is important. An out-of-spec problemwill be evident. It is also necessary to look for trendsthat warn of a condition that may become a majorproblem. An abnormal rise in the wear metals indi-cates abnormal wear. Increasing sulphur contentand acidity indicates that the lube oil is being con-taminated by high-sulfur fuel, oil blowby, etc.

(d) The lube oil tank must be sufficientlylarge to hold the oil required for the engine. It mustbe kept clean and closed to prevent contaminationof the oil. A vent with flame arrestor should exist.The tank is the reservoir that feeds the oil pumps.The pump suction line should be above any possiblesludge or water at the bottom. The tank and all thecomponents of the lube system should be of materi-als that will not contaminate the oil.

(e) Lube oil pumps circulate the oil at pres-sure (5 to 75 psi depending on engine design andsystem pressure losses when cold) through the oilfeedline to the engine lube oil header. An auxiliaryelectrically-driven pump is used prior to starting acold engine to provide warm oil to all points, espe-cially to heavily loaded main, crank, and wrist pinbearings, to make sure the lubricating film isformed at first movement. This auxiliary pump mayalso serve as an automatic standby should a normalengine-driven pump system fail. Controls and valv-

ing are provided for that changeover. The auxiliarypump is generally used long enough to return the oilfrom the critical points and to check the pressure,temperature and flow sensors, indicators, and con-trols to enable engine cranking. Pumps are usuallygear-type with pressure regulation. The engine-driven pump speed is directly related to enginespeed so that oil flow increases as speed increases.

b. Types and operation. Large diesel engines usea lubrication system different from that of smallerdiesel engines. Because large engines require alarge quantity of oil, a separate sump tank is in-stalled to receive oil from the crankcase. The lubri-cating oil pump draws oil from the sump tankthrough the strainers. Oil is then discharged, underpressure, into the oil cooler.

(1) The oil then goes to a header, located on theengine, with branches leading to the various partsof the system. Leads extend from the header to eachmain bearing. After the oil has been supplied to themain bearings, it passes through a drilled passagein the crank web. The oil then passes through a holein the crank bearing journal to the connecting rodbearing and up through a drilled hole in the con-necting rod to the wrist pin. At the wrist pin, the oil,in some engines, passes through a spray nozzle forsplash lubrication against the underside of the pis-ton for cooling. The oil then drains down to theengine crankcase and returns to the pump. Otherbranches from the header rnay supply oil to the geartrains, camshafts and bearings, rocker arms andpush rods, cylinder walls, turbo-chargers, blowers,and in some engines, to an oil-cooling system forpistons. Engines may vary in many details, but theprinciples are the same in all.

(2) Lubricati ng systems of small engines usu-ally are self-contained. The crankcase or a separateoil pan underneath the engine contains all the oilused in the system. Figure 3-8 is a cross section of adiesel engine, showing lube oil flow.

c. Process. The diesel engine lubrication systemmust circulate, filter, and cool large quantities oflubricating oil. Figure 3-9 shows a schematic ar-rangement of the main components of a diesel lubri-cation system. The arrows show the flow of lube oilthrough the system.

d. Oil storage. All high-speed engines and mostmedium and low-speed engines use the crankcasebase or a sump integral with the crank-case forstoring lubricating oil. Several engines operate witha so-called dry crankcase to avoid crankcase oil fogthat may cause excessive cylinder lubrication. Suchengines must have an outside sump tank placed sothat oil from the crankcase will drain into it. Onedesign has an elevated, closed pressure tank towhich oil is pumped from the crankcase. Open,

3-13


CYLINOER HEA9 II

COMBUSTION CHAMBER<

PLATFORM <

CYLINOER LINERS ’WATER COOLED

EXHAUST HEADER

‘Y FRAMES dREMOVABLE COVERS

CRANKPIN ANDMAIN BEARING SHELL2 \_Jj

CRANKSHAFT

T IE RCO

COVER FOR ACCESSTO SCAVENGING AIR VALVES

COOLING OIL AREAOF P ISTON HEAD

SCAVENGINGAIR HEADER

SCAVENGINGAIR PASSAGE

I N J E C T I O N P U M P

CONNECT ING ROD

. BEDPLATE

Figure 3-8. Cross Section of a diesel engine showing chamber for lubricating oil collection.

elevated tanks and two sets of pumps are also used.Sump capacities vary with horsepower.

e. Lube oil pumps. In most engines, an engine-driven rotary pump supplies pressure needed to cir-culate oil through the engine lubrication system. Oilpressure varies from 5 to 60 pounds, depending ondiesel engine type. The pressure depends on theamount of clearance in the bearings and the capac-ity of the pump.

f. Types of pumps. Lubricating oil pumps are usu-ally built into and driven by the engine. In high-speed engines, the oil pump is usually placed in thecrankcase sump and driven from the camshaft by avertical shaft. In larger engines, the pump can bechain-driven by the crankshaft, or mounted at the

3-14

end of the engine, either inside or outside the crank-case, and driven by the crankshaft. In other en-gines, the pump is mounted on the end and drivenfrom the camshaft gears. Larger diesel engines fre-quently have an auxiliary, motor-driven pump thatcirculates oil to the bearings before the engine isstarted. As soon as the engine is up to speed, thepump shuts down. The auxiliary pump also servesas an emergency lubricating oil pump in case theengine-driven pump fails. Finally, the auxiliarypump circulates the oil for a time after the engine isshut down to cool bearings, journals, and pistons.When this method is used, a check valve in thedischarge line of the auxiliary pump is necessary toprevent the oil from flowing back when the engine


LUBE OIL IN-\ 7

.

WATER INLET

LUBE OILFILTER

,_DRAlN

WATER OUT_ I

ERATURELATING

I

LUBE OIL OUT

SUMP

Figure 3-9. Diesel engine lubrication system.

comes up to speed and the auxiliary pump is shutdown. The check valve also prevents loss of oil incase of leakage.

g. Heating. Circulating lubricating oil absorbsheat from the engine. Frictional heat is absorbedfrom the bearings. The oil film on the cylinder wallsabsorbs heat from the combustion space before thisoil film drains into the crankcase. Heat must bedissipated by a cooler if the temperature is to bekept below 230” Fahrenheit. At higher tempera-tures, oil oxidizes and sludge forms. An oil cooler isnecessary when heat dissipated from the oil (byconduction through the walls of the sump and bycontact with water-cooled surfaces in the engine) isinsufficient to keep the temperature below manu-facturer’s recommendations. A cooler is particularlynecessary for engines having oil-cooled pistons.

h. Coolers. The oil cooler should be placed in theoil circuit after the lubricating oil filter. The filterthen handles hot oil of lower viscosity than if itreceived cooled oil. The filter performance is betterand the pressure drop through it is less with thisarrangement. Coolers are usually mounted on theside of the engine or on the floor alongside of theengine base. Cooling water passes through thecooler before entering the engine jackets. Excep-tions, such as placing the oil-cooling coils in thewater jackets at one end of the engine, are permis-

sible. Also, the coils may be placed in the side jack-ets. Some designs have the coil tubes in the coolingwater header, while in others, water entering thecooler is bypassed around the jacket system.

i. Oil filters. Proper installation and maintenanceof oil filters and mechanical operation of the engineare equally important for treatment of oil. Preven-tion of contamination and removal of contaminantsshould be coordinated. Because high-detergent oilsare used in engines, the purification system shouldnot remove the additive. Cellulose filter cartridgesdo not remove the additive, but a fuller’s earth filterdoes. In large engine installations, a centrifuge maybe used with filter purifiers, or large continuous oilpurifiers may be used in lieu of the centrifuge. Cen-trifuging does not remove acids because acidic com-pounds have approximately the same specific grav-ity as oil. Batch settling effectively removes organicacids from oil, improving its neutralization number.When purifiers are used, they should be used inaddition to, not in place of, lube oil filters.

3-7. Starting system.The starting system for diesel engines described inthis manual must perform as follows for automaticstart-up when primary electric power fails: com-press the air in the combustion chambers and de-liver fuel for combustion. To do this, the starting

3-15


system must rotate (crank) the engine at a speedsufficient to raise the cylinder air charge to the fueligniting temperature. See figure 3-6.

a. Types. Two types of starting systems are avail-able for the required automatic start-up capability:electric starting and air starting.

(1) Electric starting. Most small diesel enginesuse an electric starting system. This type of systemis generally similar to a starter for an automotivegasoline engine. Smaller diesel engines use a l2-volt battery-powered system for cranking. Starterand battery systems of 24, 32, and 48 volts are oftenused for larger engines. A typical system consists ofstorage batteries (as required for voltage output)connected in series, a battery charging system, andthe necessary grounding and connecting cables. Seefigure 3-10.

3-16

CABLE

CABLE TO

TO GROUND

BATTERY CONNECTING C:ABLE

(2) Air starting. Some larger engines may usean air starting system. Compressed air at a pres-sure of 250 or 300 psi is delivered to the workingcylinder’s combustion chambers during the powerstroke. This action results in positive and fast rota-tion (cranking). Depending on the manufacturer’sdesign, compressed air can be delivered to all orselected cylinders. This type of system requires anair compressor and receivers or air bottles for stor-age of compressed air.

(3) Air starter motor. Pneumatic air starter mo-tors are highly reliable. Air starter motors developenough torque to spin the engine at twice the crank-ing speed in half the time required by electricstarter motors. Compressed air at a pressure of 110to 250 psi is stored in storage tanks, regulated to110 psi and piped to the air motor. A check valve

-

Figure 3-10. Battery for engine starting system.


installed between the compressor and the storagetanks will prevent depletion of compressed airshould the plant system fail. Air starter motors aresuitable on diesel engine driven generators rangingfrom 85 kW up to the largest diesel engine genera-tor.

3-8. Governor/speed control.A diesel engine used in an auxiliary generator musthave a governor to regulate and control enginespeed. Since an automatic governor functions onlywith a change in speed, constant engine speed maynot be totally possible and “hunting” can occur dueto over-correction. The governor’s sensitivity is de-termined by the minimum change in speed of theprime mover which will cause a change in governorsetting; its speed regulation is the difference in gen-erator speeds at full-load and no-load divided by thearithmetical mean of the two speeds. Refer to theglossary for descriptions of governor characteristics.

a. Usually, this ratio is stated as a percentage,with synchronous speed considered rather thanmean speed. For example, a generator with a syn-chronous speed of 1,200 rpm, operated at 1,190 rpmwhen fully loaded and 1,220 rpm with no load, has2.5 percent speed regulation.

b. The governor must be capable of speed adjust-ment so the proper governed speed can be selected.In most governors, this adjustment is made bychanging the tension of the main governor spring.The governor should also be adjustable for speedregulation so the droop of the speed-load curve canbe altered as required to suit operating conditions.Determine the curve by observing the generatorspeed or frequency at various loads and plottingthem as abscissa against the loads (from no-load tofull-load) as ordinates. The curve droops at the full-load end (hence, the expression “speed droop” of thegovernor).

c. An example of speed droop characteristics isshown in figure 3-11. The characteristics are for amechanical governor but the same principles can beused for other engine/governor applications. Thechart is based on a six percent speed droop governoron an engine running at rated speed at no load.When full load is applied, engine speed drops to 94percent (94%) of rated value (line B). The enginecan be brought to rated speed at full load by reset-ting the governor (line A). However, with the loadremoved, engine speed would increase beyond itsrated limit. Intermediate speed settings are shownby lines C and D. Line E shows speed droop at 50percent (50%) load.

d. Speed droop can be determined quickly byloading the generator to full-load, observing thespeed, unloading the generator, and again observing

106

96

920 20 40 60 80 IOC

PER CENT, LOAD

SPEED VS LOAD-MECHANICAL GOVERNOR

A 6% DROOP-RATED SPEED AT 00% LOAD8 6% DROOP- RATED SPEED AT 0% L O A D

C 80 6 % DROOP - INTERMEDIATE SETTINGSE 4% DROOP-RATED SPEED AT 50% LOAD

Figure 3-11. Chart of speed droop characteristics.

the speed. Speed droop is usually adjusted bylengthening or shortening the governor operatinglevers, changing the ratio between governor move-ment and throttle or gate movement.

e. Alternating Current (AC) Generators. Gover-nors of prime movers driving AC generators whichoperate in parallel with other generators must haveenough speed regulation or speed droop to preventsurging of the load from one generator to another.Ordinarily, three to five percent speed regulation isadequate. Some governors have antisurging devicesto damp out the surges. Speed regulation should beincreased if the surges continue. Speed regulation ofgovernors controlling AC generators affects the fre-quency and the load division between generatorsbut has almost no effect upon voltage.

f. Direct Current (DC) Generators. Regulation ofDC generators affects voltage regulation and thedivision of load between generators. In general, the

3-17


speed regulation of generators operated in parallelshould be the same for each machine. Speed regula-tion for generators operating individually should beas favorable as possible without causing generatorsurge resulting from sudden load changes. Ordi-narily, 2.5 percent speed regulation is satisfactoryVoltage regulation of DC generators may be accom-plished through adjustment of the speed droop ofthe governor.

g. Types of governors. Usually four types of gov-ernors are used; mechanical, hydraulic, pneumatic,and electronic. When speed regulation must bemore precise, such as Defense CommunicationsAgency sites where no more than 0.8 percent varia-tion is permitted, an electronic (isochronous) gover-nor is used.

(1) The mechanical governor used in small air-cooled engines may be part of the fly-wheel. Thegovernor in multicylinder engines is usually a sepa-rate assembly driven by gear or belt from a cam-shaft or crankshaft. A typical mechanical governor,shown in figure 3-12, operates as follows: the gov-ernor drive gear (2) drives the governor shaft (10)and the governor weights (4). Centrifugal forcemoves the weights away from the shaft which pushthe operating-fork riser (6) against the operatingfork (ll), rotating the operating-fork shaft (7) andmoving the governor arm (9). In the external view,the governor spring (A) is connected to the governorarm and opposes movement of the governor weightsaway from the shaft. Adjusting screw (c) adjusts thetension of the governor spring, establishing thespeed at which the prime mover operates. Thegreater the governor-spring tension, the lower thegoverned speed. The auxiliary adjusting screw (D)adjusts the droop of the governor. Turning thisscrew in closer to the arm decreases the droop of thegovernor; this screw should be turned in as far aspossible without allowing the engine to surge. Aux-iliary adjusting screw (B) is turned in to damp outsurging of the engine at light-load or no-load; itshould not be turned in so far that it increases thespeed of the generator at no-load.

(2) The hydraulic governor (see fig 3-13) isused on large prime movers as well as diesel en-gines as small as 100 hp. The governor usuallyincludes: a speed-responsive device, usually fly-weights; a valve mechanism; a regulating cylinderand piston; and a pressure pump and relief valve.The assembly is adjustable for various ranges ofspeed and sensitivity. The hydraulic principle pro-vides greater power than could be obtained from amechanical type. Since the flyweights only controlan easily moved pilot valve (which in turn controlsthe hydraulic action), the governor can be made tooperate accurately and smoothly. Remote control

3 -18

and automatic equipment can be applied to the hy-draulic governor.

(a) The hydraulic governor requires pressur-ized oil for operation. This oil can come from theengine or from a separate sump in the governor. Oilis admitted to an auxiliary oil pump in the governor.The auxiliary pump furnishes necessary pressure toactuate the governor mechanism. In the governorshown, the fuel to the engine is decreased by theaction of the fuel-rod spring (10) on the fuel rod ( 12)and increased by the opposing action of the hydrau-lic serve piston (14), the admission of oil to which iscontrolled by a pilot valve (4). The pilot valve iscontrolled by flyweights of the governor (5) whichare driven by the governor shaft through gearing tothe engine. The centrifugal force of the flyweights inrotation is opposed by the speeder spring (6), thecompression of which determines the speed atwhich the governor will control the engine. Thespeeder-spring compression is adjusted through therotation of the speed-adjusting shaft (8) whichraises or depresses the spring fork (7) through itslinkage lever.

(b) The droop of the speed-load characteristicis adjusted by changing the effective length of thefloating lever (11). This is accomplished by movingthe droop-adjusting bracket forward or backward inthe slot of the floating lever. The effective length ofthe lever should be shortened to decrease the speeddroop and lengthened to increase the speed droop.

(3) The pneumatic governor (air-vane type) isused in certain small generator plants (see fig3-14). The engine flywheel includes an integral fanwhich forces air outward from the drive shaft. Theamount of air flowing from the engine depends onengine speed. A movable air vane is placed in the airstream. The air vane (blade) acts as a governorsince the air pressure depends upon engine speed.The air pressure on the vane is opposed by a gover-nor spring and these forces operate through linkageto control the throttle of the engine.

(4) Electronic (isochronous) speed control is themaintenance of constant engine speed independentof the load being carried (zero droop). An isochron-ous governor will maintain, or can be adjusted tomaintain, constant engine speed (within 0.2 percentvariation). This type of governor can be a combina-tion of a conventional hydraulic governor and anelectronic load-sensing system, or an all-electricsystem.

(a) Speed control by the hydraulic governor,see paragraph 3-8d(2), depends on variation in cen-trifugal force created by flyweights (centrifugalforces are not used in electric types). This forceoperates a piston-type pilot valve which controls the

01 BEARING

- E X T E R N A L


011 \OPERATING FORK

012 BUMPER SPRING -

n(13) BUMPER SPRING SCREW L \w

VIEW

ADJUSTING

ADJUSTABLE I

SCREWI

SCREW GOVERNORSPRING

DRIVEGEAR

COCK NUT

014 BUMPER SPRING SCREW

Figure 3-12. Mechanical Governor.

3-19

TM 5=685/NAVFAC MO-912

F R O M ENGINE

Figure 3-13. Hydraulic Governor.1) PLUNGER, 2) GEAR PUMP DRIVE, 3) GEAR PUMPIDLER, 4) PLUNGER PILOT VALVE, 5) FLYWEIGHT,

6) SPEEDER SPRING, 7) SPRING FORK,8) SPEED-ADJUSTING SHAFT, 9) SPEED-ADJUSTING

LEVER, 10) SPRING, 11) FLOATING LEVER,12) FUEL ROD, 13) TERMINAL LEVER,

14) SERVO PISTON

THROTTLE ADJUSTING SCREW

GOVERNOR BLADE

NEEDLE VALV

ADJUSTING

Figure 3-14. Carburetor and pneumatic governor.

flow of high-pressure oil to a servomotor, therebyoperating fuel controls.

(b) The isochronous system uses electronicsensing and amplifying devices that actuate a typeof servomotor throttle control. The system is usedwith power generation where precise frequency con-trol is required. An isochronous system may be sen-sitive to frequency changes (engine speed) or to bothfrequency and load. When responsive to loadchanges, the system corrects fuel settings beforeload changes can appreciably modify engine speedor frequency.

3-9. Air intake system.Approximately 15 pounds of air is required to burnone pound of fuel. Accordingly, the air requirementfor a 2000 horsepower engine is about 3600 cubicfeet per minute. The same horsepower-to-air rela-tionship applies to engines for other power ratings.Intake air carries dust particles, water vapor andother foreign material. Since these materials candamage moving parts within the engine, filtrationof the intake air is necessary. A 2000 horsepowerengine, breathing air containing three parts permillion dust contamination, would take in 25pounds of foreign material in 1000 operating hours.An air intake system must collect, filter, and dis-tribute the required air to the engine cylinders. Thismust be accomplished with a minimum expenditureof energy (pressure drop). The objective of air filtra-tion is the reduction of engine component wear. Sev-eral types of air filters or air cleaners are used. Thepleated-paper type are strainers, porous enough topass air but able to remove solid particles largerthan 0.002 of an inch. Larger engines use an oil-bath air cleaner (see fig 3-15). In oil-bath cleanersair is drawn through an oil bath. Solid particles aretrapped and settle in the unit’s bottom pan.

a. Supercharging. Supercharging increases theamount of air taken into a working cylinder. Thisprovides the injected fuel oil with more oxygen toenable combustion of a larger charge of air/fuel mix-ture. Power output of a certain size engine isthereby increased, enabling use of smaller engineswhere space prohibits larger engines.

(1) Advantages. The power output of a natu-rally aspirated engine is limited by the normal pres-sure and oxygen content of the atmosphere. Whensupercharging is used, the intake valve (port) closeswith the cylinder under the initial pressure. Super-charging is particularly effective at higher alti-tudes. The supercharged engine can develop greaterhorsepower than the standard naturally-aspiratedunit. The fuel consumption of a supercharged unitwill not exceed that of comparable horsepower sizesof naturally-aspirated units.

3-20


Figure 3-15. Oil bath air cleaner:

(2) Methods. The most successful method of su-percharging is the use of a turbocharger driven byexhaust gas (see fig 3-16). The heat and energypulsations in the exhaust gas, which are usuallylost in the exhaust silencer, are used to drive asingle-stage centrifugal turbine. The exhaust gasturbine is coupled to a centrifugal compressor thatcompresses the air to a pressure of four or fivepsi. The engine’s pressurized air is then delivered tothe individual cylinders through the intake mani-fold.

(3) Disadvantages. Although the superchargedengine has many advantages over nonsuperchargedengines, its disadvantages are not insignificant. Theturbocharger is another piece of equipment to main-tain and operate. It operates at varying speeds de-pending on engine load, barometric pressure, inletair temperature, exhaust temperature, smoke con-tent of the exhaust, or accumulations of dust anddirt on the impeller and diffuser. It may operate atvery high speed (up to 120,000 rpm) with a full loadon the engine and thus be subjected to all thetroubles of high-speed equipment. With propermaintenance, however, the turbocharger can be op-erated very successfully. If the turbocharger fails,the engine can usually be operated at reduced loadas a nonsupercharged engine. The turbocharger canbe partially dissembled and the opening blocked off,

but the coolant should be allowed to circulatethrough the supercharger.

(4) Operating instructions. Manufacturer’s in-structions must be followed to ensure proper opera-tion of superchargers. Filtered air only should enterthe air inlet, because foreign matter can cause rotorimbalance and damaging vibration. The manufac-turer’s recommendations for lubrication must be fol-lowed. Proper lubrication is necessary because theunit operates at high speed and at high tempera-ture. Not more than 15 seconds should elapse be-tween the start of rotation and an oil pressure indi-cation of 12 to 71 psi. Coolant circulation throughthe turbocharger should be regulated so the tem-perature rise does not exceed 30” Fahrenheit at fullengine load. A rise in excess of 30” Fahrenheit indi-cates faulty circulation. Coolant should be allowedto circulate through the turbocharger for about 5minutes after the engine is shutdown.

b. Aspiration. The term “naturally-aspirated” isapplied to engines that are not supercharged. A fourstroke cycle engine performs its own air pumpingaction with the piston intake stroke. When it issupercharged, a four-stroke engine with a blower orturbocharger provides pressure in the intake mani-fold greater than atmospheric. The increased pres-sure in the intake manifold is referred to as “boost”.Two stroke cycle engines require an air supply un-der pressure to provide scavenging air.

3-10. Exhaust system.Components. The exhaust system consists of theengine exhaust manifold and includes piping, ex-pansion joints, silencers, and exhaust pipe. Also thesystem may include exhaust waste heat recoveryequipment. The purpose of the system is to removeexhaust gas from engine cylinders to the atmo-sphere. Parts of the system are shown in figure 3-6.

(a) Leak-free. Exhaust systems must be leak freeto protect personnel from asphyxiation, and equip-ment from fire and explosion. Exhaust from gaso-line engines can contain dangerous carbon monox-ide. Diesel engine exhaust includes objectionablesmoke and odors. On supercharged engines, leaksahead of the turbine cause a loss of power.

(b) Piping. Exhaust piping must be the correctsize to minimize exhaust back pressure. Connec-tions between exhaust manifold and piping shouldhave an expansion joint and the exhaust pipesshould slope away from the engine. Also the exhaustpipes should have suitable devices to prevent entryof rainwater. The length of tail pipes from silencerto atmosphere should be kept to a minimum.

(c) Silencers. Silencers are used to reduce ormuffle engine exhaust noise. Silencing engine ex-haust sounds consists of trapping and breaking up

3-21

TURB’ IMPELLER

GAS INLET

ENGINECYLINDER

EXHAUST GASDISCHARGE

ENGINE EXHAUST GAS FLOW AMBIENT AIR!=) COMPRESSED AIR FLOW JNLET

Figure 3-16. Diagram of turbocharger operation.

the pressure waves. Usually, a cylindrical unit withbaffles, expansion chambers, and sound absorptionmaterials is used.

3-11. Service practices.a. Maintenance program. Service practices for

diesel engines consist of a complete maintenanceprogram that is built around records and observa-tions. The maintenance program includes appropri-ate analysis of these records. DD Form 2744(Emergency/Auxiliary Generator Operation Log)should be used to record inspection testing ofemergency/auxiliary generators. A copy of DD Form

3-22

2744 is provided at the back of this publication. Acompleted example of DD Form 2744 is located inappendix F, figure F-l. It is authorized for electronicgeneration.

(1) Record keeping. Engine log sheets are animportant part of record keeping. The sheets mustbe developed to suit individual applications (i.e.,auxiliary use) and related instrumentation. Accu-rate records are essential to good operations. Notesshould be made of all events that are or appear to beoutside of normal range. Detailed reports should belogged. Worn or failed parts should be tagged andprotectively stored for possible future reference and

_-

analysis of failure. This is especially importantwhen specific failures become repetitive over a pe-riod of time which may be years.

(2) Log sheet data. Log sheets should includeengine starts and stops, fuel and lubrication oil con-sumption, and a cumulative record of the following:

(a) Hours since last oil change.(b) Hours since last overhaul.(c) Total hours on engine.(d) Selected temperatures and pressures.

b. Troubleshooting. Perform troubleshooting pro-cedures when abnormal operation of the equipmentis observed. Maintenance personnel should then re-fer to log sheets for interpretation and comparisonof performance data. Comparisons of operationshould be made under similar conditions of load andambient temperature. The general scheme fortroubleshooting is outlined in the following para-graphs.

(1) Industrial practices. Use recognized indus-trial practices as the general guide for engine ser-vicing. Service information is provided in the manu-facturer’s literature and appendixes B through G.

(2) Reference Literature. The engine user mustrefer to manufacturer’s literature for specific infor-mation on individual units. For example, refer totable 3-5 for troubleshooting an engine that hasdeveloped a problem.

Table 3-5. Diesel engines troubleshooting.

HARD STARTING OR FAILS TO STARTCause Remedy

Air intake restricted. Check intake and correct as required.

Fuel shut-off closed, Make sure shut-off is open and supply is atlow supply of fuel. proper level.

Poor quality fuel. Replenish fuel supply with fresh, proper qualityfuel.

Clogged injector. Clean all injectors, refer to appendix G.

Injector inlet or drain Check all connections and correct as required.connection loose. En- Schedule the overhaul and correct as required.gine due for overhaul.

Incorrect timing. Perform timing procedure, refer to appendix G.

ENGINE MISSES DURING OPERATION

Air leaks in fuel suc- Check fuel suction lines and correct as re-tion lines. quired.

Restricted fuel lines. Check fuel lines and correct as required.

Leakage at engine Refer to manufacturer’s instructions and correctvalves. as required.

Incorrect timing. Perform timing procedure, refer to Appendix G.

EXCESSIVE SMOKING AT IDLE

Restricted fuel lines. Check fuel lines and correct as required.


Table 3-5. Diesel engines troubleshooting-Continued

EXCESSIVE SMOKING AT IDLECause Remedy

Clogged injector. Clean all injectors, refer to appendix G. ReferLeaking head gasket to manufacturer’s instruction and correct asor blowby. Engine due required. Schedule the overhaul and correct asfor overhaul. Incorrect required. Perform timing procedures. refer totiming. appendix G.

EXCESSIVE SMOKING UNDER LOAD

The same causes for“idle” apply.

Air intake restricted.

High exhaust backpressure.

Poor quality fuel.

The same remedies for “idle” apply.

Check air intake and correct as required.

Check exhaust system and turbocharger; correctas required.

Replenish fuel supply with fresh, proper qualityfuel.

Engine overloaded. Reduce load to proper ievel.

LOW POWER OR LOSS OF POWER


Poor quality fuel.


Replenish fuel supply with fresh, proper qualityfuel.

Clogged injector. Clean all injectors, refer to appendix G.

Faulty throttle linkage Check linkage and governor refer to manufac-or governor setting too turer’s instructions and correct as required.low.

Clogged filters andscreens.

Clean filters and screens.

Engine overloaded.

Engine due for over-haul.

Reduce load to proper level.

Schedule the overhaul and correct as required.

Incorrect timing. En- Perform timing procedure, refer to appendix G.gine requires tune-up. Perform tune-up procedure, refer to appendix

G.

DOES NOT REACH GOVERNED SPEED

The same causes for“low power”, apply.

The same remedies for “low power”, apply.

EXCESSIVE FUEL CONSUMPTION


High exhaust backpressure.

Poor quality fuel.

Faulty injector.

Engine overloaded.


Incorrect timing.



Check exhaust system and turbocharger; correctas required.

Replenish fuel supply with fresh. proper qualityfuel.

Clean all injectors, refer to appendix G.



Perform timing procedure, refer to appendix G.

ENGINE QUITS


3-23


Table 3-5. Diesel engines troubleshooting---Continued

ENGINE QUITSCause Remedy

High exhaust back Check exhaust system and correct as required.pressure turbocharger.

Fuel shut-off closed, Make sure shut-off is open and supply is atlow supply of fuel. proper level.


Faulty injector. Clean all injectors, refer to appendix G.

ENGINE SURGES AT GOVERNED SPEED

Air leaks in fuel suc- Check fuel suction lines and correct as re-tion lines. quired.

Faulty injector. Clean all injectors, refer to appendix G.

Leaks in oil system. Check for oil leaks, check oil lines, checkcrankcase drain plug and gasket; correct as re-quired.

Engine due for over- Schedule the overhaul and correct as required.haul. Piston rings or cylinder liners may be worn.

SLUDGE IN CRANKCASE

Fouled lubricating oilstrainer or filter.

Check strainers and filters, remove and serviceas required, reinstall on engine with new gas-kets.

Faulty thermostat. Check coolant thermostats, engine may be toocool.

Dirty lubricating oil. Drain old oil, service strainers and filters, refillwith fresh oil.

LUBRICATING OIL DILUTED

Fuel in lubricating oil. Check for loose injector inlet or drain connec-tion; correct as required. Drain old oil, servicestrainers and filters, refill with fresh oil.

Coolant in lubricating Check for internal coolant leaks. Correct asoil. required. Drain old oil, service strainers and

filters, refill with fresh oil.

LOW LUBRICATING OIL PRESSURE

Faulty oil line, suction Check oil lines for good condition, fill toline restricted, low oil proper oil level with fresh oil.level.

Engine due for over- Schedule the overhaul and correct as required.haul. Piston rings, crankshaft bearings, or cylinder

liners may be worn.

ENGINE RUNNING TOO HOT

High exhaust back Check exhaust system and turbocharger; correctpressure. as required.

Faulty thermostat. Check coolant thermostats; correct as required.

Low lubricating oil Fill to proper level with fresh oil.level.

Engine overload. Reduce load to proper level.

Faulty cooling system Check components; correct as required. Fillcomponent (pump, cooling system to proper level with coolant.hose, radiator fan belt).

3-24

Table 3-5. Diesel engines troubleshooting-Continued

ENGINE RUNNING TOO HOTCause Remedy

Low coolant level. Air Refer to appendix D.in system.

ENGINE KNOCKS


Air leaks in fuel suc-tion lines.

Engine overloaded.

Engine running toohot.

Check fuel suction lines and correct as re-quired.


Repeat the procedures for “too hot”, above.

Faulty vibrationdamper or flywheel.


Correct as required, refer to manufacturer’sinstructions.


3-12. Operational trends and engine over-haul.

a. Trending data. Usually, a graphic presentationof data simplifies detection of a trend toward dete-riorating engine performance. Samples of graphicaids are shown in figures 3-17 and 3-18. Theseinclude plots of fuel and lubricating oil consumptionversus electric load (power production), monthlypressure checks (engine parameters), and mainte-nance data showing cylinder wear and crankshaftdeflection. Interpretation of data and details areprovided in the specific engine manufacturer’s lit-erature. These kinds of data aid in developing crite-ria for equipment performance and determining theneed for engine overhaul or other repair.

(1) Samples of information appearing in figure3-17 are as follows:

__

(a) “A” on the chart may indicate lack of op-erating hours.

(b) “B” on the chart may indicate a peakvalue or seasonal characteristic.

(c) “C” on the chart may indicate the result offrequent starts or stops. “D” on the chart indicates asteady improvement.

(d) “E” on the chart shows lubricating oilconsumption. The steady decline at “F” may indi-cate a developing engine problem (i.e., oil controlring failure, lube oil leakage into combustion areas,or excessive oil feed).

(2) Samples of information appearing in part Aof figure 3-18 are as follows:

(a) “A” on the chart may indicate faulty fuelinjectors, or deviations in fuel timing.

(b) “B” on the chart (sharp rise in compres-sion) can be caused by carbon build up or may indi-cate new piston rings were installed.


0

I5

14

13

12

I I

I O

9

8

?

6

5

4

3

2

PLOT OF FUEL AND LUBE OIL CONSUMPTION VS. LOAD

ENGINE NO. 19-

Figure 3-l7. Performance data plots.

(c) “C” on the chart may indicate a develop-ing engine problem.

(d) “D” on the chart indicates engine gover-nor positions relative to " A " , “B”, and "C”.

- -

b. Engine overhaul. An engine consists of struc-tural parts and moving parts. Structural parts arethose having no movement relative to each other.They do not involve clearances, adjustments, or lu-brication. These parts consist of the following: foun-dation, bedplate, foundation bolts, frames, cylindersand block, cylinder heads, covers and associatedgaskets, and auxiliary housings. Moving parts arethose that normally require fitting and/or clearanceadjustment. These parts consist of the following:crankshaft (including journal surfaces, counter-weights, gears, and flywheels), main bearings,thrust bearings, camshafts and bearings, connect-ing rods and bearings, pistons (including rings andpins), timing gear mechanisms, and auxiliary oraccessory drives. All of these parts are engineeredand designed by the engine manufacturer to per-form a particular task. When the need to overhaulan engine is indicated by operational malfunctions

(refer to the troubleshooting table) consult the spe-cific manufacturer’s literature for instructions.

c. Overhaul procedure. Engine overhaul requiresdisassembly of the engine. Verify that all engineparts comply with the manufacturer’s specificationsand tolerances.

(1) Inspect structural parts as follows: (a) Foundations for deformation and cracks.(b) Bedplate for cracks and distortion; bear-

ing supports for good condition.(c) Foundation bolts for tightness and gen-

eral good condition including straightness.(d) Frames for cracks, distortion, and gen-

eral good condition.(e) Cylinders and cylinder blocks for cracks;

water jacket areas for corrosion, scale, and rust;machined surfaces for smoothness.

(f) Cylinder heads for cracks; water jacketareas for corrosion, scale, and rust; valve seats forcracks; machined surfaces for smoothness.

(g) Covers and gaskets for distortion andcracks; use satisfactory gaskets only after anneal-ing; use new seals and gaskets other than copper.

3-25


PLOT OF MONTHLY PRESSURE CHECKS

100 ’ 7I

4

,o.

’X

9 0I

,z 60 1 1 I I I I

5 0 COMPRESSION

9 0

: 60F3;

10

2 60

SOG O V E R N O R

g 40

of 30w; 20 ’

c3 I O0 f 4

JAM. FEB. MAR. APR. MAY JUN. JUL. AUG. SEP. OCT. NOV. OEC.

E N G I N E N O . _ A V E R . L O A D D U R I N G T E S T . _ KW 4

‘9-

A .

K E Y

- A L O N G E N G I N E C . L .

- - - - A C R O S S E N G I N E C L .

B.

--

Figure 3-18. Maintenance data plots.A) ‘AS-FOUND” PRESSURES, B) MEASUREMENTS OF MECHANICAL WEAR INDICATORS.

“.__

(2) Inspect moving parts as follows:(a) Crankshaft for out-of-alignment condi-

tion; journal surfaces for highly polished conditionand absence of scratches, nicks, etc.; and counter-weights, gears, and flywheels for proper condition.Verify that crankshaft complies with manufactur-er’s requirements. An engine crankshaft is a costlyand vulnerable component. Special care in handlingis required. Accurate alignment is essential to goodengine operation. Removal or installation may re-quire hoisting. Refer to the manufacturer’s instruc-tions for details and proper procedures.

(b) Main be arings for highly polished condi-tion, cracks, deformation and absence of scratches,nicks, etc.

(c) Thrust bearings for cracks and deforma-tion; surfaces for smoothness and absence ofscratches and nicks.

(d) Camshaft cams and cam faces for worn ordeformed condition; journal surfaces and bearingsfor highly polished condition and absence ofscratches, nicks, etc; and cam contours and camfollowers for good condition.

“-_

(e) Connecting rods for cracks or other flawsby magnaflux or dye penetrant method and forbending and for parallelism; bearings for highly pol-ished condition and absence of scratches, nicks,cracks, and deformation.

(f) Pistons for cracks and warped condition;verify pistons, rings, and pins comply with manu-facturer’s requirements; and rings and pins for gen-eral good condition.

(g) Timing gear mechanisms for good condi-tion; backlash for manufacturer’s tolerance require-ments; and gear teeth for general good condition.

(h) Auxiliary or accessory drives for good op-erating condition. Consult the specific manufactur-er’s literature for instructions.

d. Repair parts and supplies. Certain repairparts and supplies must be available for immediateuse. Refer to specific manufacturer’s literature forrecommendations. The following information is ageneral guide:

(1) The following parts should be renewed ateach: gaskets, rubber sleeves, and seals. Adequatequantities should be maintained.

(2) The following parts have a reasonably pre-dictable service life and require replacement at pre-dictable periods: fuel injectors, pumps, governors,and valves. A one-year supply should be main-tained.

(3) The following parts have a normally longlife and, if failure occurs, could disable the enginefor a long period of time: cylinder head, cylinderliner, piston and connecting rod, gear and chaindrive parts, and oil pressure pump. One item of


each part for an engine should be available.e. Parts salvage. Certain parts may be replaced

prior to their failure due to a preventive mainte-nance program. It may be possible to restore theseparts to specified tolerances. Refer to specific manu-facturer’s literature for recommendations and in-structions. The following information is a generalguide:

(1) Worn pump shafts and cylinder liners maybe built up and machined to specified dimensions.

(2) Grooves in pistons may be machined and l

oversize rings specified for use.(3) Press-fitted bushings and bearings may

loosen. The related body part may be machined to anew dimension and oversize bushings and bearingsfitted.

(4) Worn journals on crankshafts and cam-shafts may be built up and machined to specifieddimensions.

3-13. Gas turbine engines.The following provides a general description of gasturbine engines used for power generation. Informa-tion is also provided in paragraph 3-lb of thismanual. For generating electric power, a turboshaft(shaft turbine engine is used (see fig 3-19). In a)turboshaft engine, the turbine provides power inexcess of that required to drive the engine compres-sor. The excess power is applied as rotary drivingtorque available at an output shaft. The power todrive the output shaft is extracted from the sameturbine that drives the compressor. The turbine isusually connected through a gearbox to the genera-tor. The gearbox is used for speed reduction.

3-14. Gas turbine engine classifications.a. Pressure and stages. Gas-turbine engines used

for auxiliary power generator sets are classified ashigh-pressure-turbine (HPT) or low-pressure-turbine (LPT) types. Additionally, the engines areclassified by the number of stages employed in theturbine design. In general, the more stages used inthe design, the greater the engine torque. All of theturbine rotor stages in the multi-stage turbine areconnected to a common shaft.

b. Power requirement. For a specified primemover power requirement, the engine design can beeither a single-stage, large diameter turbine or anequivalent small diameter multi-stage turbine.

c. Simple cycle. Most engines are designed to usenatural gas and/or liquid fuel similar to kerosene.These are called simple-cycle engines.

”d. Compressor and combustor. Most engines havean axial flow compressor and a cannular or annularcombustion section (combustor).

3-27


3-15. Principles of operation.a. Components. A typical gas turbine engine con-

sists of a compressor, combustor and turbine (see fig3-20).

(1) The compressor is driven by the turbinethrough a common shaft. Air enters the compressorvia an inlet duct. The compressor increases the airpressure and reduces the air volume as it pumps airto the combustor and through the engine.

(2) Fuel (liquidd and/or natural gas) is deliveredto the combustor by a fuel system consisting of amanifold, tubes, and nozzles. Electrical igniters in

the combustor provide a spark to ignite the fuel/airmixture for engine start-up. The igniters are deac-tivated after start-up has been accomplished. Hotcombustion gases are expelled through the turbine.

(3) The turbine extracts energy from the hot

-

gases, converting it to rotary power which drivesthe compressor and any load, such as a generator.Exhaust gases are vented via ductwork to the atmo-sphere.

(4) The air intake for a gas turbine engine usu-ally consists of a plenum chamber with a screenedinlet duct opening. The plenum chamber and duct

INLETDUCT

EXHAUSTI DUCTI

Kd /SHAFT GEARBdX

TOR

-

Figure 3-19. Typical gas turbine engine for driving electric power generator.

Figure 3-20. Gas turbine engine, turboshaft.

3-28

P TM 5-685/NAVFAC MO-912

are engine emplacement features that may vary at connected by tubes to allow flame propagation dur-different installations. Air entering the duct passes ing ignition and operation.

3-16. Gas turbine fuel system.‘L through a filter assembly. The filters remove debrisand other material that would otherwise be drawninto the engine compressor and other operating ar-

4 eas causing damage. Usually the lowest part of theplenum is equipped with a drain for removal ofmoisture.

z b. Sequence of euents. Combustion causes an in-crease in gas temperature proportionate to theamount of fuel being injected, a moderate increasein velocity, and a negligible decrease in pressure.Approximately 25 percent of the compressor’s totalair flow is used for combustion at an air/fuel ratio ofabout 15:l. The remaining 75 percent of compressorair output is fed to the combustor and to cool com-bustor liners for cooling combustion gases beforethey enter the turbine.

System components. The system provides the enginewith the proper amount of fuel to sustain operation.System components include filters, a fuel manifold,fuel tubes, and nozzles. Off-engine components in-clude the fuel control equipment and a supply sys-tem.

‘“_

(1) The sequence of events during turbine en-gine start-up and operation is as follows:

(a) Air is drawn into the compressor by ro-tating the engine. Rotation is accomplished by theengine starter. The engine is rotated to the speed atwhich it becomes self-sustaining.

(b) As the engine shaft is rotated and accel-erated by the starter, fuel is fed to the combustor.When the air pressure is high enough, the air/fuelmixture is ignited by an electrical spark.

(c) The electrical spark is deactivated afterignition occurs. Since the air/fuel mixture is con-tinuously fed to the combustor by the turbine andcompressor, and since there is a flame in the com-bustor after ignition, engine operation is self-sustaining.

(d) Rotation of the engine by the starter isnecessary after combustion takes place to help ac-celerate the engine to rated speed. Once the enginespeed has increased to approximately 60 percent ofrated speed, the starter is deactivated.

(e) Gas turbine engines have dual-fuel capa-bility since they may use either liquid or gaseousfuel. Generating units with these engines are reli-able and virtually free of vibration.

(2) Types of combustors. Combustors for gasturbine engines for generators are either cannularor annular-type with newer engines usually havingan annular combustor. The annular-type engine isdescribed in this manual. See figure 3-21 for de-tails. The annular combustor consists of a continu-ous circular inner and outer casing or shell; thespace between the casings is open. The cannularcombustor consists of inner and outer combustioncasings mounted coaxially around the enginecompressor/rotor shaft. A cluster of burner cans arelocated between the two casings. The cans are inter-

a. Fuel. Fuel (liquid and/or natural gas) entersthe tubular fuel manifold ring via the supply sys-tem. The fuel tubes direct the fuel from the mani-fold to the fuel nozzles which are mounted in thefuel swirlers (see fig 3-22 and 3-23). Compressordischarge air flows radially inward through theprimary swirler in the combustion liner, whichrotates the air circumferentially and mixes it withthe fuel. Air entering radially inward throughthe secondary swirler is caused to rotate in theopposite direction. As the two counter-rotating mix-tures join, the fuel mixes completely with the air.This process promotes complete mixing of the fueland air and, therefore, more complete burning ofthe mixture resulting in less smoke emission andmore uniform temperature distribution within thecombustor.

b. Ignition. Ignition is accomplished by one ortwo igniter plugs. At ignition, the igniters are acti-vated and fuel is injected into the swirlers. Afterignition, the igniters are deactivated (refer to para3-15b( 1)).

3-17. Gas turbine cooling system.a. Approximately 25 percent of the air entering a

combustor is mixed with fuel and burned. The re-maining air is mixed with the products of combus-tion to reduce the temperature of gases entering theturbine to a safe operating level. Cooling is accom-plished by engine airflow.

.

(r

LL

b. Three forms of air cooling of the vanes andblades are used, either separately or in combina-tions. The types of cooling are convection, impinge-ment, and film (see fig 3-24).

(1) Convection. For convection cooling, airflows inside the vanes or blades through serpentinepaths and exits through the blade tip or holes in thetrailing edge. This form of cooling is used in thearea of lower gas temperature (see fig 3-25).

(2) Impingement. Impingement cooling is aform of convection cooling, accomplished by direct-ing cooling air against the inside surface of theairfoil through small internal high velocity air jets.Cooling is concentrated at critical sections, such asleading edges of vanes and blades (see fig 3-26).

3-29


INNERCOMBUSTIONCASING

COMBUSTION SECTION

~~

CANNULAR COMBUSTOR COMBUSTION OUTER CASING

FUEL

DIFF'U

3-30

ANNULAR COMBUSTOR

Figure 3-21. Typical types of combustors.ABOVE: CANNULAR TYPE; BELOW: ANNULAR TYPE


HIGH PRESSURETURBINE OUTER CASING

Figure 3--22. Engine combustion section.

(3) Film. Film cooling is a process whereby alayer of cooling air is maintained between high tem-perature gases and the external surfaces of the tur-bine blades and vanes. In general, film cooling is themost effective type.

3-18. Lubrication system.a. The lubrication system for a gas turbine en-

gine is usually self-contained with the engine andsupplies oil for lubrication and cooling during en-gine operation (see fig 3-27). Engine bearings in thecompressor, combustor, and turbine areas (identi-fied as areas A, B, and C, respectively) are suppliedby the system. System pressure is approximately 75psi and is usually maintained by a supply and scav-enge pump (refer to scavenging in appendix C).Most systems include a heat exchanger to cool theoil and an oil supply tank.

b. On-engine components usually include lubri-cation supply and scavenge piping, a supply tem-perature RTD sensor (resistance temperature detec-tor), and chip detectors at A, B, and/or C oilcollection sumps. Nozzles are provided for oil distri-

bution to bearings. Off-engine components includeflexible oil lines between on-engine and off-enginecomponents, oil cooler, oil tank, lubrication supplydifferential pressure sensor, and lubrication pump.Oil is supplied by jet or spray to bearings in otherareas via tubes. The engine starter is usually lo-cated in an accessory gearbox.

(1) A-Sump. Oil for A-- sump components is usu-ally piped from a gearbox into the sump. Internalpassages and manifolding carry the oil to theA-sump housing. A double-headed nozzle suppliesoil to the forward bearing and the undercooled car-bon seal runner for the bearing. The second bearingis lubricated through oil nozzles mounted on apower take-off housing. Oil is supplied to the rearbearings through jets on the forward and aft sides ofthe bearing. The carbon seal runner for the bearingis cooled by oil which has lubricated the power take-off unit and the compressor forward shaft, and isthen sprayed outward through holes in the shaft.This oil is then passed through holes at the sealrunner where an oil slinger moves it away from thecarbon seal.

3-31

TM 5-685lNAVFAC MO-912

OUTER SHELL

Figure 3-23. Engine combustion liner.

(2) B-Sump. Oil enters the B-sump via a framestrut and is directed through tubing in the housingto the mid-engine bearing oil nozzles. Each nozzlehas two jets. One jet supplies oil to the bearing andthe other jet supplies oil to the carbon seal runnerfor the bearing.

(3) C-Sump. Oil enters the C-sump through afeed tube and is diverted internally throughmanifolding and tubing to the oil nozzles. In many

engines, the rearmost nozzle has two heads withtwo jets in each head. One set of jets sprays oil onthe bearing. The other set sprays oil on the bearinglocknut which causes the oil to spray on the rearwall of the C-sump cover and vent collector to cool itand reduce coking. The adjacent bearing oil nozzlealso usually has two heads with two jets in each.Two jets direct oil onto the bearing and the othersdirect oil to the carbon seal runner for the bearing.

3-32

SCHEMATIC OF TYPICALFIRST STAGE TURBINEINLET STATIONARY VANES

CONVECTION


SCFITU

Figure 3-24. Air cooling modes of turbine vanes and blades.

3-33


NO

LEADING BLADE

EALER TIP

CAP ~-,

-INLET HOLES TRAILING BLADE

SQUEALER TIP

BLADE PLATFORM

CA

AIRFOIL AIRINLET HOLES

AIR DISCHARGEHOLES

TRAILING BLADE

MATINGSURFACE

Figure 3-25. Turbine blade cooling air flow.


INSERTCOVER

FRONT tNSERT

NOSE HOLES

16TH STAGE

SC3TS

Figure 3-26. Turbine vane cooling air f l o w .

(4) Scavenging. Scavenging is accomplished bya multi-element lubrication and scavenge pump.One element is used for pumping. The other ele-ments are used for forward and aft scavenging ofthe B-sump and C-sump. Oil in the A-sump drainsby gravity into the accessory gearbox.

vented. To maintain high differential pressure(5) Venting. S

across the carbon seals to prevent oil leakage, a

ome lubrication systems are

high sump vent capacity is required. The A and Csumps vent through the engine output shaft andvent collector to ambient. The B-sump vents to theturbine exhaust gas stream.

3-19. Starting system.Gas turbine engine starters must be capable of ro-tating an engine up to a speed-at which it becomesself-sustaining. The starter must provide sufficienttorque to accelerate the engine from a standstill to aself-sustaining speed within a specified time. Al-though it must continue to assist the engine in ac-celerating up to a predetermined speed.

a. Electric motor. An electric starter motor is usu-ally used for a gas turbine engine in service as anauxiliary generator prime mover. The starter ro-tates the engine compressor shaft via the gear trainin the accessory gearbox. In most installations thestarter can be energized either automatically ormanually.

b. Fuel. As the engine is accelerated by thestarter, fuel is supplied when a specified rotationalspeed is attained. When this speed is attained, thecompressor and engine-driven fuel pump will de-liver sufficient air and fuel, respectively to the com-bustion chamber to sustain satisfactory combustion.

c. Ignition system. An ignition system, consisting

ductor surface

of an ignition exciter, igniter plug lead assemblies,

coating at the tip between theelectrodes. The

and igniter plugs, is required. Fuel ignition is en-

semiconductor ma

sured by one or two igniter plugs connected to the

.terial is used

exciter by the separate igniter leads. The plugs arelocated in the combustion chamber. Each plug con-sists of center and outer electrodes with a semicon-

twoas a

shunt to aid in ionizing the air gap between the twoelectrodes so that the plugs will fire. An air shroudcovers the end of the plug immersed in the airstream for cooling.

d. Specialized system. Starting systems arehighly specialized and are usually applicable to agiven installation or site. Refer to supplier’s on-sitetechnical literature for details.

3-20. Governor/speed control.a. Engine operation. The engine is started by an

external power source. Once the engine reaches idlespeed, it is self-sustaining. All it needs is adequatesupplies of air and fuel. Combustion gas drives the

3-35


-

Figure 3-27. Lubrication system for gas turbine.

3-36

turbine which is mounted on a common shaft withk

L the compressor. The compressor draws in the air forcombustion and also drives the gearbox gear train.rc - About two-thirds of the power derived from combus-tion is required to sustain combustion. The remain-ing power is available for work purposes and drivesthe output shaft.

b. Speed signal. An engine speed signal, gener-ated by magnetic pickups (speed transducers) in thegearbox, provides electrical signals that are propor-tional to engine speed. The signal causes a dc volt-age to be generated.

c. Thermocouples. Thermocouples sense the tur-bine discharge/inlet total temperature. The electri-cal temperature sensing signal is an average of theoperating temperature profile.

d. Pressure sensing. Sensing of compressor dis-charge static pressure and turbine discharge pres-sure is also required for engine speed control. Thesepressures are combined to produce an electrical sig-nal equal to pressure ratio.

e. Computer. The three signals (speed, tempera-ture, and pressure ratio) are summed in anacceleration/deceleration computer. Computer out-put functions with a governor to meter fuel requiredfor engine operation. If required, a signal derivedfrom a tachometer can be used to determine a rate-of-change feedback signal.

-_ 3-21. Compressor.The function of the compressor is to raise the pres-sure and reduce the volume of the air as it pumpsit through the engine. An axial flow or centrifugalflow compressor is used. Most engines use a multi-stage, axial flow compressor such as describedherein. The axial flow consists of two major sub-assemblies: the rotor assembly and the stator as-sembly. Axial flow compressor efficiency is betterthan centrifugal flow compressor efficiency. Cen-trifugal flow compressors were first used in earlydesign gas turbine engines. The main component isan impeller which is mounted on a common shaftwith the turbine. These compressors are generallyused with smaller engines and have a fairly lowpressure ratio. The design has lower efficiency thanthe axial-flow design but is less expensive to manu-facture.

3-22. Gas turbine service practices.a. Maintenance program. Service practices for

gas turbine engines consist of a complete mainte-


nance program that is built around records andobservation. The program is described in the manu-facturer’s literature furnished with each engine. Itincludes appropriate analysis of these records.

b. Record keeping. Engine log sheets are an im-portant part of record keeping. The sheets must bedeveloped to suit individual applications (i.e., auxil-iary use) and related instrumentation.

c. Log sheet data. Log sheets should include en-gine starts and stops, fuel and lubrication oil con-sumption, and a record of the following:

(1) Hours sincee last oil change.(2) Hours since first put in service or last over-

haul.(3) Total hours on engine.

d. Oil analysis program. Use of a SpectrometricOil Analysis Program is recommended to determinethe internal condition of the engine’s oil-wetted(wear metal) components, such as bearings, gears,and lubrication pump.

(1) The program should be used as a supple-ment to the regular maintenance procedure of chipdetection and filter inspection. Normal wear causesmicroscopic metal particles (smaller than one mi-cron) to mix with the lubricating oil and remain insuspension. Samples of oil taken from the engineafter a shutdown will contain varying amounts ofwear-metal particles.

(2) Oil samples should be removed from theengine at the time intervals specified by the enginemanufacturer. A sample should always be takenfrom the same location on the engine (this may varyfrom each engine). Refer to manufacturer’s litera-ture. See appendix C paragraph C-le(2).

(a) Metal content. Evaluation of the oil’swear-metal content is very important. The quantityof wear-metal in the sample as well as type (iron orsteel, silver, chromium, nickel, etc.) must be evalu-ated and recorded.

(b) failure forecast. Evaluation records areintended as an aid in forecasting what componentsare in danger of failing. Contamination of the oilsample must be prevented to avoid false indicationof engine internal conditions. ,

e. Industrial practices. Use recognized industrialpractices as the general guide for engine servicing.Service information is provided in manufacturer’sliterature and appendixes B through G.

f. Reference Literature. The engine user should re-fer to manufacturer’s literature for specific informa-tion on individual units.

3-37

CHAPTER 4


GENERATORS AND EXCITERS-

4-1. Electrical energy.Mechanical energy provided by a prime mover isconverted into electrical energy by the generator(see fig 4-l). The prime mover rotates the generatorrotor causing magnetic lines of force to be cut byelectrical conductors. Electrical energy is therebyproduced by electromagnetic induction. The ratio ofoutput energy generated by input energy is ex-pressed as a percentage and always shows a loss inefficiency.

needed to direct the flow of current in one direction.The generator rotating commutator provides therectifying action.

4-4. AC generators.

4-2. Generator operation.a.A generator consists of a number of conducting

coils and a magnetic field. The coils are called thearmature. Relative motion between the coils andmagnetic field induces voltage in the coils. Thisaction is called electromotive force (emf). A sche-matic for a typical generator system is shown infigure 4-2.

a. AC generators are considered either brush orbrushless, based on the method used to transfer DCexciting current to the generator field. In addition,AC generators are classified as salient-pole ornonsalient-pole depending on the configuration ofthe field poles. Projecting field poles are salient-poleunits and turbo-type (slotted) field poles arenonsalient-pole units. Typical AC generatorarmatures are shown in figures 4-3 and 4-4.

’ .___

b. An alternating current (AC) generator needs aseparate direct current (DC) source to feed the mag-netic field. The required DC is provided by an exter-nal source called an exciter. Usually, the exciter is asmall DC generator that is driven by the generatorrotor. The exciter may be mounted on the rotor shaftor rotated by belt-drive. Some generating systemsuse a static, solid-state exciter to provide DC.

b. Damper windings on the rotor stabilize thespeed of the AC generator to reduce hinting underchanging loads. If the speed tends to increase,induction-generator action occurs in the damperwindings. This action places a load on the rotor,tending to slow the machine down. If the speedtends to decrease, induction-motor action occurs inthe damper winding, tending to speed the machineup. The windings are copper bars located in thefaces of the rotor pole pieces. Mounted parallel tothe rotor axis, the bars are connected at each end bya copper ring.

c. A voltage regulator controls the induced volt-age by regulating the strength of the electromag-netic field established by the exciter. Frequency iscontrolled by the speed at which the prime moverrotates the rotor.

c. AC generators that operate at a speed that isexactly proportional to the frequency of the outputvoltage are synchronous generators. Synchronousgenerators are usually called alternators.

4-5. Alternator types.

4-3. Types of generators.Depending on the type of generating equipment em-ployed, the electrical energy produced is either di-rect current ( D C ) or alternating current (AC).

a. AC generators. AC generators are classified assingle-phase or polyphase. A single-phase generatoris usually limited to 25 kW or less and generates ACpower at a specific utilization voltage. Polyphasegenerators produce two or more alternating volt-ages (usually two, three, or six phases).

Alternators are single-phase or polyphase. Varia-tions include three-phase alternators used assingle-phase units by insulating and not using onephase lead. Since the lead is unused, it is notbrought out to a terminal. The kilowatt rating isreduced from that of the three-phase unit as limited by the amount of current carried by a coil. An alter-nator designed only for single-phase operation usu-ally does not have coils in all of the armature slotsbecause end coils contribute little to the output volt-age and increase the coil impedance in the sameproportion as any other coil.

b. DC generators. DC generators are classified as (a) Single-phase alternators are usually used ineither shunt, series, or compound-wound. Most DC smaller systems (limited to 25kW or less) and pro-generators are the compound-wound type. Shunt duce AC power at utilization voltages.generators are usually used as battery chargers and (1) Terminal voltage is usually 120 volts. Theas exciters for AC generators. Series generators are electric load is connected across the terminals withsometimes used for street lights. The emf induced in protective fuses. One voltmeter and one ammetera DC generator coil is alternating. Rectification is measure the output in volts and amperes, respec-


--

Figure 4-l. Typical alternating current generator.

EXCITER GENERATOR

; IIIII

III

11

T2ATJ

STATORWINDINGS

t

; / ;;=I j ALkRNATOR "O&E F E E D B A C K = ’j

- - - -I - - - - - - - - - - - - - - - - - - - - - - - -

Figure 4-2. Brush-type excitation system, schematic.


SLIP R

DAMPER

Figure 4-3. Brush-type AC generator field and rotor:

Figure 4-4. AC generator field and rotor with brushless-type excitation system.

tively The two-wire alternator has two power termi-nals, one for each end of the armature coil (see fig4-5).

(2) The three-wire, single-phase alternator hasthree power terminals; one from each end of thearmature coil and one from the midpoint (neutral,see fig 4-6). Terminal voltage is usually 120 voltsfrom the midpoint to either end of the armature coil

and 240 volts between the two ends. The load isconnected between the two outside wires or betweeneither outside wire and neutral, depending upon thevoltage required by the load. Assuming alternatorvoltage to be 120/240 volts, load 1,0 and load 2,0would consist of 120-volt lamps and 120-volt single-phase power equipment. Load 1,2 would consist of240-volt power equipment. Two voltmeters and two


TO EXCITER AMMETER LOAD

Figure 4-5. Two-wire, single-phase alternator.

a- -1

Iv

l

TO EXClTER 0 LOAD1. 1, 1.2

AMMETER

Figure 4-6. Three-wire, single-phase alternator.

ammeters (or equivalent) are required to determinethe load in kilovoltamperes (kVA).

(b) Polyphase alternators are two, three, or sixphases. Two-phase power is used in only a few lo-calities. Six-phase is primarily used for operation ofrotary converters or large rectifiers. Three-phasealternators are the most widely used for power pro-duction. Polyphase alternators have capacities from3 kW to 250,000 kW and voltage from 110 V to13,800 V. Two general types of three-phases alterna-tor windings are the delta winding used in three-wire, three-phase alternators, and the star or wyewinding used in four-wire, three-phase types.Three-wire, three-phase alternators have three sets

of single-phase windings spaced 120 electrical de-grees apart around the armature. One electricaldegree is equivalent to one degree of arc in a two-pole machine, 0.50 degree of arc in a four-pole ma-chine, 0.33 degree of arc in a six-pole machine, andso on. The three single-phase windings are con-nected in series to form the delta connection, andthe terminals are connected to the junction point ofeach pair of armature coils (see fig 4-7). The totalcurrent in a delta-connected circuit is always equalto the vector sum of currents in two-phase wind-ings. The instantaneous current flows out to theload through two windings and returns from theload through the third winding. Since the coils are

-


EXCITER

SINGLE PHASEVOLTMcTERS AMMETERS LOAD

. I ,* . I _’VM AM. LOAD

GENERATORROTOR STATOR PHASE LOAD

VM AM LOAD

Figure 7.92 Three-wire, three-phase alternator.

‘i--

similar physically and electrically, equal voltagesare generated and applied to the terminals. Due tospacing of the coils about the armature, the maxi-mum voltage between the pairs of terminals doesnot occur simultaneously. The characteristics ofthree- wire, three-phase (or delta) alternators are:

(1) The amount of current through the alterna-tor terminals is the algebraic sum of currentthrough the alternator coils.

(2) The currents are not equal in magnitude ortime.

(3) Connection between coils can be made ei-ther inside or outside the generator.

\_

(c) In a 60-Hertz machine, each coil experiencesmaximum instantaneous voltage, first positive andthen negative, 120 times each second. Disregardingvoltage direction, the maximum instantaneous volt-ages occur on successive coils 0.003 seconds apart.Due to time differences between the voltages andresulting currents, the amount of current throughthe alternator terminals and the amount throughthe alternator coils are not equal in magnitude ortime. The current through the alternator is 73 per-cent greater than through the coils. Coil and termi-nal voltages are the same magnitude. Three voltme-ters and three ammeters (or equivalent) arerequired to measure the load on the alternator. Theaverage value of the three currents times the aver-age value of the three voltages plus 73 percent givesa close approximation of the alternator load inkilovolt-amperes. Two single-phase or one two-element polyphase kilowatt-hour meter is requiredto measure the alternator output in kilowatt-hours.

(d) The four-wire, three-phase alternator (see fig4-8) has three sets of armature coils spaced 120electrical degrees apart about the armature, thesame as the three-wire, three-phase alternator. Oneend of each of the three coils is connected to acommon terminal (neutral). The other end of eachcoil is connected to separate terminals (phase ter-minals). Thus, the four-wire alternator has fourterminals which connect to the three-phase con-ductors and the neutral of the power-plant bus.When each end of each coil is brought out to sepa-rate terminals, the connections between coils aremade outside of the alternator, enabling installationof a more comprehensive protective relaying sys-tem.

(e) The four-wire, three-phase alternator can beconnected to a transformer instead of the power-plant bus by using a wye-wye transformation. Ir-regular (double or triple) harmonics, which may beproduced, can be suppressed by using a core-type transformer. A third or tertiary winding with a deltaconnection may also be used as a suppressor. Awye-delta transformer may be used if the powerplant bus is three wire and the alternator is fourwire wye connected.

(f) Four-wire three-phase, dual voltage andfrequency alternators are also used. These are sup-plied in sizes from 15 to 1500 kW, 127-220 volts,three-phase, 60 Hertz, or 230-400 volts, three-phase, 50 Hertz. Dual stator coils are used on eachphase. Coil ends are brought out to a terminal boardfor making connections. Voltage and frequency com-binations are shown in figure 4-9.

4-5


VOLTMETERS SlNCLE PHASELOAD

AMMETERS LINE TO LOAD

I NEUTRAL LINE TO LINEI/IG E N E R A T O R

EXCITER ROTOR7

7 -r

LOAD1.2

LOAD2.3. ,

2 ’VM. AM. LOAD2,o l;O

I )I, *

Q 30 t

l * Y

VM.390

3

Figure 4-8. Four-wire, three-phase alternator.

VOLTAGE AN0 FREQENGINE-GENERATOR

UENCY COMSETS USED

ATIONSERSEAS

STATOR

%

(B 1 PARALLEL COIL CONNECTION(A) SERIES COIL CONNECTION

frequency.Figure 4-9. Dual voltage and

(g) Most parts of the world have standard-ized on either 50 or 60 Hertz alternating current

L power. Sixty Hertz power is commonly used in theUnited States. Fifty Hertz power is used in manycountries outside the United States. The ratio be-t

end of each coil is connected to separate terminals.Conductors attached to the four terminals carry thecurrent to the system’s switchgear and on to theload.

tween the 60-50 Hertz frequencies is 6:5. Electricalenergy received at one frequency can be convertedto a different frequency by using a frequencychanger. If a large power requirement exists, it maybe more economical to use a special alternator toproduce power at the desired frequency The appli-cable equation is:

V=KxQlxNxfwhere V = generated voltage

K = constant value number (speed)8 = phase/phase angleN = number of turnsf = line frequency

(h) The generated voltage is proportional to thestrength of the magnetic field, phase, and number ofturns in series between terminals and the speed.

4-6. Design.a. Components. A typical AC generator consists of

a stationary stator and a rotor mounted within thestator (see fig 4-l). The stator contains a specificnumber of coils, each with a specific number ofwindings. Similarly, the rotor consists of a specificnumber of field poles, each with a specific number ofwindings. In addition to the rotor and stator (referto paragraphs 4-6b and 4-6c, respectively), a gen-erator has a collector assembly (usually consistingof collector slip rings, brushes, and brush holders).The slip rings are covered in paragraph 4-6d. DCflows from the exciter, through the negative brushand slip ring, to the rotor field poles. The returnpath to the exciter is through the positive brush andslip ring.

d. Collector sl ip rings. Slip rings are usuallymade of nonferrous metal (brass, bronze or copper);iron or steel is sometimes used. Slip rings usuallydo not require much servicing. The wearing ofgrooves or ridges in the slip rings is retarded bydesigning the machine with limited endplay and bystaggering the brushes. Surfaces of the slip ringsshould be bright and smooth, polishing can be per-formed with fine sandpaper and honing stone. Elec-trolytic action can occur at slip ring surfaces pro-ducing formation of verdigris. Verdigris is agreenish coating that forms on nonferrous metals.Electrolytic deterioration can be prevented by re-versing the polarity of the slip rings once or twice ayear. The stator of the three-wire, three-phase unitalso has three sets of armature coils spaced 120electrical degrees apart. The ends of the coils areconnected together in a delta configuration. Conduc-tors are attached to the three connecting points.

4-7. Characteristics of generators.

“X-

a. Voltage. Generated voltage is the emf denotingthe electric pressure between phases in the arma-ture. The magnetic flux linking each armature coilchanges as the machine rotates. The change in fluxper turn occurs at the conductors in the armatureslots. Each conductor is regarded separately as itcuts the flux. At a specific rotating speed, instanta-neous volts per conductor are proportional to airgap flux density at the conductor.

b. Rotor. The rotor contains magnetic fields whichare established and fed by the exciter. When therotor is rotated, AC is induced in the stator. Thechanging polarity of the rotor produces the alternat-ing characteristics of the current. The generatedvoltage is proportional to the strength of the mag-netic field, the number of coils (and number of wind-ings of each coil), and the speed at which the rotorturns.

b. Current. Current is the rate of transfer (flow)of electricity, expressed in amperes. Field currentrequired for a particular load condition, i s deter-mined by the magnetic circuit, in conjunction witharmature and field windings. Load current is equalto the generated voltage divided by the impedanceof the load.

c. Speed. Normally, a generator operates at a con-stant speed corresponding to the frequency andnumber of poles. Variations may occur due tochanges in driving torque, load, field excitation, orterminal voltage.

c. Stator. The frame assembly is the main compo- d. Frequency. AC frequency is determined by thenent of the stator. Insulated windings (or coils) are rotating speed and number of poles of the generator.placed in slots near an air gap in the stator core. Frequency is usually expressed in Hertz, the fre-There is a fixed relationship between the unit’s quency used most is 60 Hertz. A two-pole generatornumber of phases and the way the coils are con- must operate at 3600 rpm to maintain 60 Hertz.nected. The stator in a four-wire, three-phase unit Four-pole and six-pole units must operate at 1800has three sets of armature coils which are spaced rpm and 1200 rpm, respectively, to maintain 60120 electrical degrees apart. One end of each coil is Hertz. Frequency at 60 Hertz is expressed in theconnected to a common neutral terminal. The other following equation:


.


Frequency = (Speed in rpm) (Pairs of poles)(60 Hertz) 60

e. Power. Power is the term used to describe therate at which electric energy is delivered by a gen-erator and it is usually expressed in watts or kilo-watts (lo3 watts).

(1) Watts. W tta s are units of active or workingpower, computed as follows: volts x measured orapparent amperes x power factor.

(2) Volt amperes reactance (Mars). Vars areunits of reactive or nonworking power (1 var = 1reactive volt-ampere).

(3) Power factor. Power factor is the ratio ofactive or working power divided by apparent power.The relationship of apparent power, active power,and reactive power is shown in figure 4-10. Thehypotenuse represents apparent power, the baserepresents active power, and the altitudepower triangle represents reactive power.

of thePower

factor (the cosine of angle 0) is a unitless numberwhich can be expressed in per unit or in percentage.For convenience, kilo (103) is often used with theterms volt- amperes, watts and vars in order toreduce the number of significant digits.

% Power Factor = kW x 100kVA

4-8. Exciters.a. An AC or DC generator requires direct current

to energize its magnetic field. The DC field currentis obtained from a separate source called an exciter.Either rotating or static-type exciters are used forAC power generation systems. There are two typesof rotating exciters: brush and brushless. The pri-mary difference between brush and brushless excit-ersren

is the method used tot to the generator field

transfers. Static

DC exciting cur-excitation for the

generator fields is provided in several forms includ-ing field-flash voltage from storage batteries andvoltage from a system of solid-state components. DCgenerators are either separately excited or self-excited.

b. Excitation systems in current use includedirect-connected or gear-connected shaft-driven DCgenerators, belt-driven or separate prime mover ormotor-driven DC generators, and DC suppliedthrough static rectifiers.

c. The brush-type exciter can be mounted on thesame shaft as the AC generator armature or can behoused separately from, but adjacent to, the genera-tor (see fig 4-2). When it is housed separately, theexciter is rotated by the AC generator through adrive belt.

d. The distinguishing feature of the brush-typegenerator is that stationary brushes are used totransfer the DC exciting current to the rotatinggenerator field. Current transfer is made via rotat-ing slip rings (collector rings) that are in contactwith the brushes.

e. Each collector ring is a hardened-steel forgingthat is mounted on the exciter shaft. Two collectorrings are used on each exciter, each ring is fullyinsulated from the shaft and each other. The innerring is usually wired for negative polarity, the outerring for positive polarity.

f. A rotating-rectifier exciter is one example ofbrushless field excitation. In rotating-rectifier excit-ers, the brushes and slip rings are replaced by arotating, solid-state rectifier assembly (see fig 4-4).The exciter armature, generator rotating assembly,and rectifier assembly are mounted on a commonshaft. The rectifier assembly rotates with, but is

ANGLE 0

Figure 4-10. Power triangle.

4-8

insulated from, the generator shaft as well as fromeach winding.

g. Static exciters contain no moving parts. A por-tion of the AC from each phase of generator outputis fed back to the field windings, as DC excitations,through a system of transformers, rectifiers, andreactors. An external source of DC is necessary forinitial excitation of the field windings. On engine-driven generators, the initial excitation may be ob-tained from the storage batteries used to start theengine or from control voltage at the switchgear.

4-9. Characteristics of exciters.a. Voltage. Exciter voltages in common use in-

clude 63 and 125 volts for small units and 250, 375,or 500 volts for large units. Exciters with normalself-excitation are usually rated at about 135 per-cent of rated voltage and a rate buildup of about 125volts per second. Working range is between 75 and125 percent of rated exciter voltage.

b. Current. An exciter provides direct current toenergize the magnetic field of an AC generator. AnyDC generator or storage battery may be used as afield current source.

c. Speed. Speed, in rotating exciters, is related togenerator output voltage. Usually, if magnetic fieldintensity is increased (by higher rotating speed),output voltage of the generator is also increased.

d. Power. Exciter voltage to the magnetic field ofan AC generator is usually set at a predeterminedvalue. A voltage regulator controls the generatorvoltage by regulating the strength of the magneticfield produced in the exciter.

4-10. Field flashing.a. Field flashing is required when generator volt-

age does not build up and the generating system(including the voltage regulator) does not have field-flash capability. This condition is usually caused byinsufficient residual magnetism in the exciter andgenerator fields. In some cases, a generator that hasbeen out-of-service for an extended period may loseits residual magnetism and require flashing. Re-sidual magnetism can be restored by flashing thefield thereby causing a current surge in the genera-tor. Refer to the voltage regulator manufacturer’sliterature for procedural instructions.

b. Solid-state components may be included in thevoltage regulator. Perform field flashing accordingto the manufacturer’s instructions to avoid equip-ment damage.

4-11. Bearings and lubrication.a. Location. Several types of bearings, each with

specific lubrication requirements, are used on thegenerators. Usually, a generator has two bearings,


one to support each end of the armature shaft. Onsome generators, one end of the shaft is supportedby the coupling to the prime mover and one bearingis used at the other end. The selections of bearingtype and lubrication are based on generator size,type of coupling to prime mover, and expected us-age. A generator is usually equipped with eithersleeve or ball bearings which are mounted in endshields attached to the generator frame.

b. Sleeve bearings. Sleeve bearings are usuallybronze and are lubricated with oil.

(1) Most unit s with sleeve-type bearings have areservoir for the oil and a sight gauge to verify oillevel. Bearings and the reservoir are fully enclosed.

(2) Distribution of oil to shaft and bearingsfrom the reservoir is by an oil-slinger ring mountedon the generator shaft. Rotation of the slinger ringthrows the oil to the top of the bearing. Holes in thebearing admit oil for lubrication.

(3) Some units with sleeve-type bearings havean absorbent fiber packing, saturated with oil,which surrounds the bearing. Holes in the bearingadmit oil for lubrication.

c. Ball bearings. Ball bearings (or roller-typebearings) are fully enclosed and lubricated withgrease.

(1) Most units with ball or roller-type bearingsare equipped with a fitting at each bearing to applyfresh grease. Old grease is emitted from a hoie (nor-mally closed by a plug or screw) in the bearingenclosure.

(2) Some units are equipped with prepacked,lifetime lubricated bearings.

d. Bearing wear. Noise during generator opera-tion may indicate worn bearings. If source of noiseis the generator bearing, replacement of the wornbearing is recommended.

e. Service practices. Service practices for genera-tors and exciters consist of a complete maintenanceprogram that is built around records and observa-tions. The program is described in the manufactur-er’s literature furnished with the component. It in-cludes appropriate analysis of these records.

f. Record keeping. Generator system log sheetsare an important part of record keeping. The sheetsmust be developed to suit individual applications(i.e., auxiliary use).

g. Log sheet data. Log sheets should include sys-tem starts and stops and a cumulative record oftypical equipment operational items as follows:

(1) Hours of operation since last bearing lubri-cation.

(2) Hours of operation since last brush andspring inspection or servicing.

(3) Days since last ventilating and coolingscreen and duct cleaning.

4-9


h. Industrial practices. Use recognized industrialpractices as the general guide for generator systemservicing.

i. Reference Literature. The generator system usershould refer to manufacturer’s literature for specificinformation on individual units.

4-12. Generator maintenance.a. Service and troubleshooting. Service consists of

performing basic and preventive maintenancechecks that are outlined below. If troubles developor if these actions do not correct a problem, refer tothe troubleshooting table 4-1. Maintenance person-nel must remember that the manufacturer’s litera-ture supersedes the information provided herein.

b. Operational check. Check the equipment dur-ing operation and observe the following indications.

(1) Unusual noises or noisy operation may in-dicate excessive bearing wear or faulty bearingalignment. Shut down and investigate.

(2) Equipment overheats or smokes. Shutdown and investigate.

(3) Equipment brushes spark frequently. Occa-sional sparking is normal, but frequent sparkingindicates dirty commutator and/or brush or brushspring defects. Shut down and investigate.

c. Preventive maintenance. Inspect the equipmentas described once a month. Maintenance personnelshould make a check list suited to their particularneeds. The actions listed in table 4-l are providedas a guide and may be modified. Refer to manufac-turer’s instructions.

Table 4-l. Generator inspection list.

Inspect Check For

Brushes

Commutator

Collector Rings

Insulation

Windings

Bearings

Bearing Housing

Ventilation and coolingsystem

Amount of wear, Improper wear, SpringTension

Dirt, Amount of wear, Loose leads, Loosebars

Grooves or wear. Dirt, carbon, and/orcopper accumulation.(verdigris)

Greenish coating

Damaged insulation. Measure and recordinsulation resistance.

Dust and dirt,connections

Loose windings or

Loose shaft or excessive endplay.Vibration (defective bearing)

Lubricant leakage, Dirt or sludge in oil(sleeve bearings)

Obstruction of air ducts or screens. Looseor bent fan blades

d. Troubleshooting. Perform general trouble-shooting of the equipment (as outlined in the follow-ing table) if a problem develops. Refer to the manu-facturer’s literature for repair information afterdiagnosis.

Table 4-2. Generator trouble shooting.

NOISY OPERATIONCause Remedy

Unbalanced load or coupling Balance load and check alignmentmisalignment

Air gap not uniform Center rotor by replacing orshimming bearings

Coupling loose Tighten coupling

OVERHEATING

Electrical load unbalanced Balance load

Open line fuse Replace line fuse

Restricted ventilation Clean, remove obstructions

Rotor winding shorted. opened or Repair or replace defective coilgrounded

Stator winding shorted, opened or Repair or replace defective coilgrounded

Dry bearings Lubricate

Insufficient heat transfer of cooler Verify design flow rate: repair orunit replace

NO OUTPUT VOLTAGE

-. ._

Stator coil open or shorted Repair or replace coil

Rotor coils open or shorted Repair or replace coils

Shorted sliprings Repair as directed by manufacturer

Internal moisture (indicated by Dry windinglow-resistance reading on megger)

Voltmeter defective Replace

Ammeter shunt open Replace ammeter and shunt

OUTPUT VOLTAGE UNSTEADY

Poor commutation Clean slip rings and reseatbrushes

Loose terminal connections Clean and tighten all contacts

Fluctuating load Adjust voltage regulator andgovernor speed

OUTPUT VOLTAGE TOO HIGH

Over-excited Adjust voltage regulator

One leg of delta-connected stator Replace or repair defective coils

open

FREQUENCY INCORRECT OF FLUCTUATING

Speed incorrect or fluctuating Adjust speed-governing device

Table 4-2. Generator trouble shooting-Continued

“C4u CauseVOLTAGE HUNTING

Remedy

Externalposition

field resistance in out Adjust resistance

Voltage regulator contacts dirty Clean and reseat contacts

STATOR OVERHEATS IN SPOTS

Open phase winding

Rotor not centered

Unbalanced circuits

Loose connections or wrongpolarity coil connections

Shorted coil

Cut open coil out of circuit andreplace at first opportunity. Cut andreplace the same coil from otherphases

Realign and replace bearings, ifnecessary

Balance circuits

Tighten connectionswrong connections

or correct

Cut coil out of circuit and replaceat first opportunity

FIELD OVERHEATING

Replace or repairShorted field coil

Improper ventilation Removeducts

obstruction, clean air

ALTERNATOR PRODUCES SHOCK WHEN TOUCHED

Reversed field coil

Static charge

Check polarity. Change coil leads

High-speedcharge

belts build up a static

Connect alternatorground strip

frame to a

4-13. Insulation testing.

I,

a. The failure of an insulation system is the mostcommon cause of problems in electrical equipment.Insulation is subject to many effects which cancause it to fail; such as mechanical damage, vibra-tion, excessive heat or cold, dirt, oil, corrosive va-pors, moisture from processes, or just the humidityon a muggy day. As pin holes or cracks develop,moisture and foreign matter penetrate the surfacesof the insulation, providing a low resistance path forleakage current. Sometimes the drop in insulationresistance is sudden, as when equipment is flooded.Usually, however, it drops gradually, giving plentyof warning, if checked periodically. Such checks per-mit planned reconditioning before service failure. Ifthere are no checks, a motor with poor insulation,for example, may not only be dangerous to touchwhen voltage is applied, but also be subject to burn-out.

b. The electrical test most often conducted to de-termine the quality of armature and alternator fieldwinding insulation is the insulation resistance test.It is a simple, quick, convenient and nondestructive


test that can indicate the contamination of insula-tion by moisture, dirt or carbonization. There areother tests available to determine the quality ofinsulation, but they are not recommended becausethey are generally too complex or destructive. Aninsulation resistance test should be conducted im-mediately following generator shutdown when thewindings are still hot and dry. A megohmmeter isthe recommended test equipment.

c. Before testing the insulation, adhere to the fol-lowing:

(1) Take the equipment to be tested out of ser-vice. This involves deenergizing the equipment anddisconnecting it from other equipment and circuits.

(2) If disconnecting the equipment from the cir-cuit cannot be accomplished, then inspect the in-stallation to determine what equipment is con-nected and will be included in the test. Payparticular attention to conductors that lead awayfrom the installation. This is very important be-cause the more equipment that is included in a test,the lower the reading will be, and the true insula-tion resistance of the apparatus in question may bemasked by that of the associated equipment. It isalways possible, of course, that the insulation resis-tance of the complete installation will be satisfac-tory, especially for a spot check. Or, it may be higherthan the range of the megohmmeter, in which casenothing would be gained by separating the compo-nents because the insulation resistance of each partwould be still higher.

(3) Test for foreign or induced voltages with avolt-ohm-milliammeter. Pay particular attentiononce again to conductors that lead away from thecircuit being tested and make sure they have beenproperly disconnected from any source of voltage.

(4) Large electrical equipment and cables usu-ally have sufficient capacitance to store a dangerousamount of energy from the test current. Therefore,discharge capacitance both before and after anytesting by short circuiting and grounding the equip-ment and cables under test. Consult manufacturer’sbulletins and pertinent references to determine,prior to such shorting or grounding, if a specified“discharge” or “bleed” or “grounding” resistor shouldbe used in the shorting/grounding circuit to limitthe magnitude of the discharge current.

(5) Generally, there is no fire hazard in thenormal use of a megohmmeter. There is, however, ahazard when testing equipment located in inflam-mable or explosive atmospheres. Slight sparkingmay be encountered when attaching test leads toequipment in which the capacitance has not beencompletely discharged or when discharging capaci-tance following a test. It is therefore suggested thatuse of a megohmmeter in an explosive atmosphere

4-11


be avoided if at all possible. If however testing mustbe conducted in an explosive atmosphere, then it issuggested that test leads not be disconnected for atleast 30 to 60 seconds following a test, so as to allowtime for capacitance discharge.

(6) Do not use a megohmmeter whose terminaloperating voltage exceeds that which is safe to ap-ply to the equipment under test.

d. To take a spot insulation reading, connect themegohmmeter across the insulation to be tested andoperate it for a short, specific timed period (60 sec-onds usually is recommended). Bear in mind alsothat temperature and humidity, as well as the con-dition of your insulation, affect your reading. Yourvery first spot reading on equipment, with no priortest, can be only a rough guide as to how “good” or“bad” the insulation is. By taking readings periodi-cally and recording them, you have a better basis ofjudging the actual insulation condition. Any persis-tent downward trend is usually fair warning oftrouble ahead, even though the readings may behigher than the suggested minimum safe values.Equally true, as long as your periodic readings areconsistent, they may be OK, even though lower thanthe recommended minimum values. You shouldmake these periodic tests in the same way eachtime, with the same test. connections and with thesame test voltage applied for the same length oftime. Table 4-3 includes some general observationsabout how you can interpret periodic insulation re-sistance tests and what you should do with theresults.

e. Another insulation test method is the time re-sistance method. It is fairly independent of tem-perature and often can give you conclusive informa-tion without records of past tests. You simply takesuccessive readings at specific times and note thedifferences in readings. Tests by this method aresometimes referred to as absorption tests. Test volt-ages applied are the same as those for the spotreading test. Note that good insulation shows a con-tinual increase in resistance over a period of time. Ifthe insulation contains much moisture or contami-nants’ the absorption effect is masked by a highleakage current which stays at a fairly constantvalue-keeping the resistance reading low. Thetime resistance test is of value also because it isindependent of equipment size. The increase in re-sistance for clean and dry insulation occurs in thesame manner whether a generator is large or small.You can therefore compare several generators andestablish standards for new ones, regardless of theirkW ratings.

f. The ratio of two time resistance readings iscalled a Dielectric Absorption Ratio. It is usefulin recording information about insulation. If theratio is a lo-minute reading divided by a l-minutereading, the value is called the Polarization Index.Table 4-4 gives values of the ratio and correspond-ing relative conditions of the insulation that theyindicate.

Table 4-3. Interpreting insulation resistance test results.

ConditionTEST RESULTS

What to Do

1.

2.

3.

4.

5.

Fair to high values andwell-maintained

Fair to high values, but showinga constant tendency towardslower values

Low but well-maintained

So low as to be unsafe

Fair or high values, previouslywell-maintained but showingsudden lowering

No cause for concern

Locate and remedy the causecheck the downward trend

and

Condition is probably all right, butcause of low values should bechecked

Clean, dry out or otherwise raisethe values before placingequipment in service (Test wetequipment while drying out)

Make tests at frequent intervalsuntil the cause of low values islocated and remedied; or until thevalues have become steady at alower level but safe for operation;or until values become so low thatit is unsafe to keep the equipmentin operation

--.

Table 4-4. Condition of insulation indicatedabsorption ratios. *

bY dielectric

InsulationCondition

60/30-SecondRatio

I Oi 1 -MinutePolarization

RatioIndex

Dangerous

Questionable

Good

Excellent

-

1.0 to 1.25

1.4 to 1.6

Above 1.6**

Less than 1

1.0 to 2

2 to 4

Above 4**

* These values must be considered tentative and relative; sub-ject to experience with the time resistance method over a periodof time.

** In some cases with motors, values approximately 20 percenthigher than shown here indicate a dry brittle winding which willfail under shock conditions or during starts. For preventivemaintenance, the motor winding should be cleared, treated anddried to restore winding flexibility.

4-12


CHAPTER 5

.- SWITCHGEAR

5-1. Switchgear definition.Switchgear is a general term covering switchingand interrupting devices that control, meter andprotect the flow of electric power. The componentparts include circuit breakers, instrument trans-formers, transfer switches, voltage regulators, in-struments, and protective relays and devices.Switchgear includes associated interconnectionsand supporting or enclosing structures. The variousconfigurations range in size from a single panel toan assembly of panels and enclosures (see fig 5-l).Figure 5-2 contains a diagram of typical switchgearcontrol circuitry. Switchgear subdivides large blocksof electricsions:

power and performs the following mis-

a. Distributes incoming power between technicaland non-technical loads.

b. Isolates the various loads.c. Controls auxiliary power sources.d. Provides the means to determine the quality

and status of electric power.e. Protects the generation and distribution sys-

tems.

5-2. Types of switchgear.Voltage classification. Low voltage and mediumvoltage switchgear equipment are used in auxiliarypower generation systems. Switchgear at militaryinstallations is usually in a grounded, metal enclo-sure (see fig 5-l). Per the Institute of Electrical andElectronics Engineers (IEEE), equipment rated upto 1000 volts AC is classed as low voltage. Equip-ment equal to or greater than 1000 volts but lessthan 100,000 volts AC is classed as medium voltage.

a. Low voltage. Major elements of low voltageswitchgear are circuit breakers, potential trans-formers, current transformers, and control circuits,refer to paragraph 5-3. Related elements of theswitchgear include the service entrance conductor,mainments

box, switches, indicator lights, and i. The service entrance conductor and

nstru-main

bus (sized as required) are typical heavy duty con-ductors used to carry heavy current loads.

b. Medium voltage. Medium voltage switchgearconsists of major and related elements as in lowvoltage switchgear. Refer to paragraph 5-4 for de-tails. Construction of circuit breakers employed inthe two types of switchgear and the methods toaccomplish breaker tripping are the primary differ-ences. The service entrance conductors and main

bus are typical heavy-duty conductors rated for usebetween 601 volts AC and 38,000 volts AC, as re-quired.

5-3. Low voltage elements.a. Circuit breakers. Either molded-case or air cir-

cuit breakers are used with low voltage switchgear.Usually the air circuit breakers have draw-out con-struction. This feature permits removal of an indi-vidual breaker from the switchgear enclosure forinspection or maintenance without de-energizingthe main bus.

(1) Air circuit breakers. Air circuit breakers areusually used for heavy-duty, low voltage applica-tions. Heavy-duty circuit breakers are capable ofhandling higher power loads than molded-caseunits and have higher current-interrupting capac-ity. Air circuit breakers feature actuation of contactsby stored energy which is either electrically ormanually applied. Accordingly, the mechanism ispowered to be put in a position where stored energycan be released to close or open the contacts veryquickly. Closing or tripping action is applied man-ually (by hand or foot power) or electrically (wherea solenoid provides mechanical force). The me-chanical force may be applied magnetically. Aircircuit breakers contain power sensor overcurrenttrip devices that detect an overcurrent to the loadand initiate tripping or opening of the circuitbreaker.

(a) Manual circuit breakers employ spring-operated, stored-energy mechanisms for operation.Release of the energy results in quick operation ofthe mechanism to open or close the contacts. Oper-ating speed is not dependent on the speed or forceused by the operator to store the energy.

(b) Fast and positive action prevents unnec-essary arcing between the movable and stationarycontacts. This results in longer contact and breakerlife.

(c) Manual stored-energy circuit breakershave springs which are charged (refer to the glos-sary) by operation of the insulated handle. Thecharging action energizes the spring prior to closingor opening of the circuit breaker. The spring, whenfully charged, contains enough stored energy to pro-vide at least one closing and one opening of thecircuit breaker. The charged spring provides quickand positive operation of the circuit breaker. Part ofthe stored energy, which is released during closing,may be used to charge the opening springs.

5-1


Figure 5-l. Typical arrangement of metal enclosed switchgear.

(d) Some manual breakers require severalup-down strokes to fully charge. The springs arereleased on the final downward stroke. In either ofthe manual units, there is no motion of the contactsuntil the springs are released.

(e) Electrical quick-make/quick-break break-ers are operated by a motor or solenoid. In smallunits, a solenoid is used to conserve space. In largesizes, an AC/DC motor is used to keep control-powerrequirements low (4 amps at 230 volts).

(f) When the solenoid is energized, the sole-noid charges the closing springs and drives themechanism past the central/neutral point in onecontinuous motion. Motor-operated mechanisms au-tomatically charge the closing springs to a predeter-mined level. When a signal to close is delivered, thesprings are released and the breaker contacts areclosed. The motor or solenoid does not aid in theclosing stroke; the springs supply all the closingpower. There is sufficient stored-energy to close thecontacts under short-circuit conditions. Energy foropening the contacts is stored during the closingaction.

(g) A second set of springs opens the contactswhen the breaker receives a trip impulse or signal.The breaker can be operated manually for mainte-nance by a detachable handle.

(h) Circuit breakers usually have two orthree sets of contacts: main; arcing; and intermedi-

5-2

ate. Arcing and intermediate contacts are adjustedto open after the main contacts open to reduce burn-ing or pitting of the main contacts.

_-

(i) A typical power sensor for an air circuitbreaker precisely controls the breaker opening timein response to a specified level of fault current. Mostunits function as overcurrent trip devices and con-sist of a solenoid tripper and solid-state compo-nents. The solid-state components are part of thepower sensor and provide precise and sensitive tripsignals.

(2) Molded-case circuit breakers. Low currentand low energy power circuits are usually controlledby molded-case circuit breakers. The trip elementsact directly to release the breaker latch when thecurrent exceeds the calibrated current magnitude.Typical time-current characteristic curves formolded-case circuit breakers are shown in figure5-3.

(a) Thermal-magnetic circuit breakers havea thermal bi-metallic element for an inverse time-current relationship to protect against sustainedoverloads. This type also has an instantaneous mag-netic trip element for short-circuit protection.

(b) Magnetic trip-only circuit breakers haveno thermal elements. This type has a magnetic trip-ping arrangement to trip instantaneously, with nopurposely introduced time delay, at currents equalto, or above, the trip setting. These are used only for


4 5 0 V O L T S , 3 P H 6 0 C P SGENERATOR BUS

LEGEND

r;!- AMMETER- WATTMETER

VM - VOLTMETER

F^u- GEN. CKT BREAKER- F U S E

---.--.----.--- _S$

- FREOUENCY HETER- SYNCHROSCOPE- TEMPERATURE METER

B- GE. CKT BREAKER

V R - VOLTAGE REGULATORP T - POTENTIAL TRANSFORMERC T - CURRENT TRANSFORMER

QOV - GOVERNOR

Figure 5-2. Typical switchgear control circuitry, one-line diagram.

short-circuit protection of motor branch circuits (1) Ratings. A PT is rated for the primary volt-where motor overload or running protection is pro- age along with the turns (step down) ratio to securevided by other elements. 120 VAC across the secondary.

(c) Non-automatic circuit interrupters haveno automatic overload or short circuit trip elements.These are used for manual switching and isolation.Other devices must be provided for short circuit andoverload protection.

b. Potential transformers. A potential trans-former (PT) is an accurately wound, low voltage lossinstrument transformer having a fixed primary tosecondary “step down” voltage ratio. The PT ismounted in the high voltage enclosure and only thelow voltage leads from the secondary winding arebrought out to the metering and control panel. ThePT isolates the high voltage primary from the me-tering and control panel and from personnel. Thestep down ratio produces about 120 VAC across thesecondary when rated voltage is applied to the pri-mary. This permits the use of standard low voltagemeters (120 VAC full scale) for all high voltage cir-cuit metering and control.

(2) Application. The primary of potential trans-formers is connected either line-to-line or line-to-neutral, and the current that flows through thiswinding produces a flux in the core. Since the corelinks the primary and secondary windings, a volt-age is induced in the secondary circuit (see fig 5-4).The ratio of primary to secondary voltage is in pro-portion to the number of turns in the primary andsecondary windings. This proportion produces 120volts at the secondary terminals when rated voltageis applied to the primary.

(3) Dot convention. A dot convention is used infigure 5-5. The dot convention makes use of a largedot placed at one end of each of the two coils whichare mutually coupled. A current entering the dottedterminal of one coil produces an open-circuit voltagebetween the terminals of the second coil. The volt-age measured with a positive voltage reference atthe dotted terminal of the second coil.

5-3


1CURRENT IN AMPERES AT- ~3.8bJOLTS

CURRENT IN AMPERES AT 13.8K VOLTS

Figure 5-3. Typical time-current characteristic curve.

a

09 z08 -

0 7 uAr

0 6 G

0 1

c. Current transformers. A current transformer(CT) is an instrument transformer having lowlosses whose purpose is to provide a f’ixed primaryto secondary step down current ratio. The primaryto secondary current ratio is in inverse proportion tothe primary to secondary turns ratio. The secondarywinding thus has multiple turns. The CT is usually

5 -4

either a toroid (doughnut) winding with a primaryconductor wire passing through the “hole”, or a sec-tion of bus bar (primary) around which is wound thesecondary. The bus bar CT is inserted into the busbeing measured. The CT ratio is selected to result ina five ampere secondary current when primaryrated current is flowing (see fig 5-4).

-


POTENT I AL CURRENTTRANSFORMER TRANSFORMER

L I D

V - V O L T M E T E R W-WATTMETER A-AMMETER

Figure 5-4. Instrument transformers, typical applications.

(1) Ratings. Toroidal CTs are rated for the sizeof the primary conductor diameter to be surroundedand the primary to secondary current (5A) ratio.Bus bar type CTs are rated for the size of bus bar,primary voltage and the primary to secondary cur-rent 5A) ratio.

(2) Application. The primary of a CT is eitherthe line conductor or a section of the line bus. Thesecondary current, up to 5A, is directly proportionalto the line current. The ratio of the primary tosecondary current is inversely proportional to theratio of the primary turns to secondary turns.

(3) Safety. A CT, in stepping down the current,also steps up voltage. The voltage across the second-ary is at a dangerously high level when the primaryis energized. The secondary of a CT must either beshorted or connected into the closed metering cir-

cuit. Never open a CT secondary while the primarycircuit is energized.

d. Polarities. When connection secondaries of PTsand Cts to metering circuits the correct polarities ofall leads and connections must be in accordancewith the metering circuit design and the devicesconnected. Wrong polarity connections will givefalse readings and result in inaccurate data, dam-age and injury. All conductors and terminationsshould carry identification that matches schemat-ics, diagrams and plans used for construction andmaintenance.

e. Control circuits. Switchgear control circuitsprovide control power for the starting circuit of theprime movers and the closing and tripping of theswitchgear circuit breakers. Additionally, the con-trol circuits provide control power to operate the

5-5


PRIMARY

Figure 5-5. Current flow in instrument transformers. ‘Polarity”marks show instantaneous flows.

various relays and indicating lights associated withthe control circuitry. The control circuits are classi-fied as either AC or DC.

__(1) AC control circuits. AC control circuits usu-ally derive their power from the source side of thecircuit breaker being controlled. This procedure ap-plies to main incoming line circuit breakers, genera-tor circuit breakers, and feeder circuit breakers (seefig 5-6). Depending on the system voltage, the con-trol power can be taken directly from the main bussince it can be connected through a control powertransformer.

(2) Tie break er control circuits. In systems us-ing a tie breaker, the control power for the tiebreaker and the feeder breakers is supplied througha throw-over scheme so control power is available ifeither side of the tie breaker is energized (see fig5-7). In applications that require synchronizing cir-cuitry, the running and incoming control buses areusually supplied via the potential transformers. Thetransformer primaries are connected to both theline side and the load side of the circuit breakersthat are used for synchronizing. The transformer

M A I N I N C O M I N G L I N E GENERATOR\\

4

M A I N ’

F U S E CONTROL POWERI * TRANSFORMER

CONTROLPOWER

BUS

\ L O A D /’

GEB

CONTROLPOWER

I TRANSFORMER

/\TN E R A T O R > &

R E A K E R I

I F U S E ,

FEEDERBREAKER

/LOAD

Figure 5-6. AC control circuits.


LOAD

Figure 5-7. AC control circuits with tie circuit breaker.

secondaries are connected to the proper control busthrough contacts on the synchronizing switch, orthrough contacts on certain auxiliary relays. Thesynchronizing switch would be used for manual op-eration and the auxiliary relay would be used whenautomatic synchronizing is provided.

(3) DC control circuits. DC control circuits de-rive their power from a battery source consisting ofa bank of batteries and a battery charger that main-tains the batteries at the proper charge. The batterybank can be rated at various levels ranging between24 volts and 125 volts DC. Those circuits that re-quire a source of control power completely indepen-dent of the power system are connected to the DCcontrol bus. Examples of these are the prime moverstarting circuits, and in some cases, the trip circuitsfor the circuit breakers when devices, other thanthe direct-acting overcurrent trip devices, are used.Also, the closing circuits for the circuit breakers aresometimes connected to the DC control bus.

f. Service practices. Service practices for low volt-age switchgear consist of a complete maintenance

program that is built around equipment and systemrecords and visual inspections. The program is de-scribed in the manufacturer’s literature furnishedwith the components. If a problem develops, theuser should perform general troubleshooting proce-dures. The program includes appropriate analysis ofthe records.

(1) Record keeping. Equipment and system logsheets are important and necessary functions ofrecord keeping. The log sheets must be specificallydeveloped to suit individual application (i.e., auxil-iary use).

(2) Troubleshoo ing.t Perform troubleshootingprocedures when abnormal operation of the systemor equipment is observed. Maintenance personnelmust then refer to records for interpretation andcomparison of performance data (i.e., log sheets).Comparisons of operation should be made underequal or closely similar conditions of load and ambi-ent temperature. Theshooting is outlined introubleshooting table.

general scheme for trouble-the following paragraphs and

5-7


(a) Use recognized industrial practices as thegeneral guide for servicing and refer to manufactur-er’s literature.

(b) The user should refer to manufacturer’sliterature for specific information on individual cir-cuit breakers.

(c) General service information for circuitbreakers includes the following safety require-ments. Do not work on an energized breaker. Do notwork on any part of a breaker with test couplersengaged. Test couplers connect the breaker to thecontrol circuit during testing. Spring-chargedbreaker mechanisms shall be serviced only by per-sonnel experienced in releasing the spring load in acontrolled manner. Make operational tests andchecks on a breaker after maintenance, before it isreturned to service. Do not work on a spring-charged circuit breaker when it is in the chargedposition.

(d) Switchgear needs exercise. If the circuitbreaker remains idle, either open or closed, for sixmonths or more, it should be opened and closed

/

several times during the period, preferably underload. If the breaker is operated by a relay or aswitch, it should be so operated at this time.

( e ) Service for molded-case circuit breakersconsists of the following procedures. Inspect connec-tions for signs of arcing or overheating. Replacefaulty connectors and tighten all connections. Cleanthe connecting surfaces. Perform overload trippingtests. Verify automatic opening of breaker. Verifythat the magnetic tripping feature is operating. Per-form circuit breaker overload tripping tests. Properaction of the breaker tripping components is veri-fied by selecting a percentage of breaker currentrating (such as 300%) for testing. This overload isapplied separately to each pole of the breaker todetermine how it will affect automatic opening ofthe breaker. Refer to manufacturer’s test informa-tion. Turn the breaker on and off several times toverify satisfactory mechanical operation.

( f ) Service for air circuit breakers consists ofthe following procedure (see fig 5-8). Install thesafety pin to restrain the closing spring force. With

CONNECTEDALL POWER CON-NECTED (PR I MA R Y 8CONTROL)

CONTROL POWERSTILL CONNECTED

--DISCONNECTEDALL POWER DISCON-NECTED

ry WITHDRAWNBREAKER WITHDRAWNREADY FOR REMOVAL

--

Figure 5-8. Maintenance for typical low voltage switchgear with air circuit breakers.

5-8


the pin in place, the contacts will close slowly whenthe breaker is manually operated. Inspect connec-tions for signs of arcing or overheating. Replacefaulty connectors and tighten all connections. Cleanthe connecting surfaces. An infrared (IR) survey is arecommended inspection procedure. The IR surveyshould be performed when the circuit breaker isunder load and closed to detect overheating of con-nections. Perform general troubleshooting of thebreaker (refer to the following table) if a problemdevelops. If the trouble cannot be corrected, refer tothe manufacturer’s literature for specific informa-tion on individual breakers. Instrument transform-ers require no care other than keeping them dryand clean. Refer to manufacturer’s literature if spe-cific information is required. Information related tocontrol circuit components is provided in paragraph5-3e of this chapter.

Table 5-l. Low voltage circuit breaker troubleshooting.

Refer to manufacturer’sindividual circuit breakers.

Note

l i terature for specific information on

Cause Remedy

OVERHEATING

-

Contacts not aligned

Contacts dirty, greasy, or coatedwith dark film

Contacts badly burned or pitted

Current-carrying surfaces dirty

Corrosive atmosphere

Insufficient bus or cable capacity

Bolts and nuts at terminal connec-tions not tight

Current in excess of breaker rating

Inductive heating

Adjust contacts

Clean contacts

Replace contacts

Clean surfaces of current-carryingparts

Relocate or provide adequate en-closure

Increase capacity of bus or cable

Tighten, but do not exceed, elasticlimit of bolts or fittings

Check breaker applications ormodify circuit by decreasing load

Correct bus or cable arrangement

FAILURE TO TRIPAdjust or replace tripping deviceTravel of tripping device does not

provide positive release of trippinglatch

Worn or damaged trip unit parts Replace trip unit

Mechanical binding in overcurrenttrip device

Correct binding condition or re-place overcurrent trip device

Electrical connectors for powersensor loose or open

Tighten, connect, or replace electri-cal connectors

Loose or broken power sensor con-nections

Tighten or re-connect tap coil tapconnections

Table 5-l. Low voltage circuit breakertroubleshooting-Continued

Refer to manufacturer’sindividual circuit breakers.

Note


Cause

FALSE TRIPPING

Remedy

Overcurrent pick-up too low

Overcurrent time setting too short

Mechanical binding in over-condition current trip device

Captive thumbscrew on power sen-sor loose. Fail safe circuitry revertscharacteristics to minimum settingand maximum time delay

Ground sensor coil improperly con-nec ted

Check application of overcurrenttrip device

Check application of overcurrenttrip device

Correct binding or replace over-current trip device

Adjust power sensor. Tightenthumbscrew on desired setting

Check polarity of connections tocoil. Check continuity of shieldand conductors connecting the ex-ternal ground sensor coil

FAILURE TO CLOSE AND LATCHBinding in attachments preventing Realign and adjust attachmentsresetting of latch

Latch out of adjustment

Latch returnbroken

spring too weak or

Hardened or gummy lubricant

Safety pin left in push rod

Motor burned out

Faulty control circuit component

Adjust latch

Replace spring

Clean bearing and latch surfaces

Remove safety pin

Replace motor

Replace or adjust faulty device

BURNED MAIN CONTACTSImproper contact sequence (main Increase arcing contact wipe Adjustcontacts not sufficiently parted contact opening sequence Refer towhen arcing contacts part) opening. Refer to manufacturer’s

literature for contact maintenanceand adjustment information. Alsorefer to paragraph 5-3a( I )(,g)

Short-circuit current level aboveinterrupting rating of breaker

Requires system study and possiblereplacement with breaker havingadequate interrupting capacity

5-4. Medium voltage elements.a. Circuit breakers. Medium voltage switchgear

uses oil, air-blast, or vacuum circuit breakers. Usu-ally the circuit breakers have draw-out constructionto permit removal of an individual breaker from theenclosure for inspection or maintenance without de-energizing the main bus. All of these circuit break-ers can quickly interrupt and extinguish the electricarc that occurs between breaker contacts when thecontacts are separated.

5-9


(1) Oil circuit b reakers. When the contacts areseparated in oil, the interrupted voltage and cur-rent can be greater as compared to contact separa-tion in air at room temperature.

(a) Arc interruption is better in oil than airbecause the dielectric strength of oil is much greaterthan air. Also, the arc generates hydrogen gas fromthe oil (see fig 5-9). The gas is superior to air as acooling medium.

(b) Usually the contacts and the arc are en-closed in a fiber arcing chamber, with exhaust portson one side, to increase the capacity.

(2) Air circuit breakers. Arc extinction by highpressure air blast is another method of quickly in-terrupting and extinguishing electric arc. Cross-blast type breakers are usually used in mediumvoltage switchgear.

(a) A cross-blast breaker uses an arc chutewith one splitter (insulating fin) that functions asan arc barrier (see fig 5-10).

(b) The arc is drawn between the upper andlower electrodes. During interruption, a blast of

high-pressure air is directed across the arc pushingthe arc against the splitter. The arc is broken atcurrent zero and carried downstream.

(3) Vacuum circuit breakers. Vacuum arc inter-ruption is the newest and quickest method of extin-guishing an electric arc. This type of breaker (seefigure 5-11) is oil-less, fireproof and nearly mainte-nance free. Service life is very long. Arc interruptionis very rapid, usually in the first current zero. Highdielectric strength of a small vacuum gap contrib-utes to the rapid interruption of the arc. Short con-tact travel permits the mechanism to part the con-tacts much faster than for oil breakers.

(4) Warning. Mechanical indication of “open”may not be true. Always make sure no voltage existson load/line side before performing any work.

b. Potential transformers. A potential trans-former (PT) is an accurately wound, low voltage-lossinstrument transformer having a fixed primary tosecondary “step down” voltage ratio. The PT ismounted in the high voltage enclosure and only thelow voltage leads from the secondary winding are

--

FIBER WALLS STATIONARY

FORMING ARCING CONTACTCHAMBER \ I

ARC

EXHAUST

HYDROGEN

SPLITTERS

MOVINGCONTACT

Figure 5-9. Arc interruption in oil, diagram.

I

-

ORIFICE PLATE __I

HIGH AIR PRESSURE

AIR BLAST,

UPSTREAMARCINGELECTRODE

ORIFICE PLATE ___+

TM 5=685/NAVFAC MO-912

(2) Application. Refer to paragraph 5-3b(2) for- application information .

c. Current transformers. A Current Transformer

j - (CT) is an instrument transformer having lowLOW AIR PRESSURE

IDOWNSTREAMARCINGELECTRODE

losses whose purpose is to provide a fixed primaryto secondary step down current ratio. The primaryto secondary current ratio is in inverse proportion tothe primary to secondary turns ratio. The secondarywinding thus has multiple turns. The CT is usuallyeither a toroid (doughnut) winding with primaryconductor wire passing through the “hole” or a unitsection of bus bar (primary), around which is woundthe secondary, inserted into the bus run. The CTratio is selected to result in a five ampere secondarycurrent when primary rated current is flowing.

Figure 5-10. Air blast arc interrupter, diagram.

brought out to the metering and control panel. ThePT isolates the high voltage primary from the me-tering and control panel and from personnel. Thestep down ratio produces about 120 VAC across thesecondary when rated voltage is applied to the pri-mary. This permits the use of standard low voltagemeters (120 VAC full scale) for all high voltage cir-cuit metering and control.

(1) Ratings. Potential transformers are usuallyrated at 120 volts in the secondary circuit.

(1) Ratings. Current transformers are usuallyrated at 5 amperes in the secondary circuit.

(2) Application. Refer to paragraph 5-3c(2) ap-plication information.

d. Control circuits. Switchgear control circuits formedium voltage are functionally similar to thoseused for low voltage systems. The control circuitsare similarly classified as either AC or DC.

(1) AC control circuits. Refer to the descriptionprovided in paragraph 5-3e( 1).

(2) DC contro circuits. Refer to the descriptionlprovided in paragraph 5-3e( 3).

e. Service practices. Service practices for mediumvoltage switchgear consist of a complete mainte-

FlexibleMetallicBellows

Assembly

I

insulatingVacuum

ElectricalContacts

Vacuum

Metal-to-insulationVacuum Seal

Metal LaporCondensing Shield

Eleckc Arcing Metal-tcLinsulationRegion Vacuum Seal

Figure 5-11. Cross sectional view of vacuum arc interrupter:

5-11


nance program that is built around equipment, sys-tem records, and visual inspections. The program isdescribed in the manufacturer’s literature fur-nished with the components. If a problem develops,the user should perform general troubleshootingprocedures. The program includes appropriateanalysis of the records.

(1) Record keeping. Equipment and system logsheets are important and necessary functions ofrecord keeping. The log sheets must be specificallydeveloped to suit individual applications (i.e., auxil-iary use).

(2) Troubleshooting. Perform troubleshoot-ing procedures when abnormal operation of thesystem or equipment is observed. Maintenance per-sonnel must then refer to records for interpretationand comparison of performance data (i.e., logsheets). Comparisons of operation should be madeunder equal or closely similar conditions of load andambient temperature. The general scheme fortroubleshooting is outlined in the following para-graphs.

(a) Use recognized industrial practices as thegeneral guide for servicing and refer to manufactur-er’s literature.

(b) The user should refer to manufacturer’sliterature for specific information on individual cir-cuit breakers.

(c) General service information for circuitbreakers includes the following safety require-ments. Do not work on an energized breaker. Do notwork on any part of a breaker with the test couplersengaged. Test couplers connect the breaker to thecontrol circuit during testing. Maintenance closingdevices for switchgear are not suitable for closing inon a live system. Speed in closing is as important asspeed in opening. A wrench or other maintenancetool is not fast enough. Before working on theswitchgear enclosure, remove all draw-out devicessuch as circuit breakers and instrument transform-ers. Do not lay tools down on the equipment whileworking on it. It is too easy to forget a tool whenclosing an enclosure.

(d) Switchgear needs exercise. If the circuitbreaker remains idle, either open or closed, for sixmonths or more, it should be opened and closedseveral times during the period, preferably underload. If the breaker is operated by a relay or aswitch, it too should be operated at this time.

(e) Service circuit breakers using insulatingliquid require special handling. Elevate the breakeron an inspection rack and untank it to expose thecontacts. The insulating liquid usually used in cir-cuit breakers is mineral oil. Equipment using liq-uids containing polychlorinated biphenyls (PCBs)may still be in use. Since PCBs are carcinogenic and

5-12

not biodegradable, some restrictions to their useapply. Silicone insulating liquid can be used as sub-stitute for PCBs when authorized by the Base engi-neer. Special handling is required if PCBs are usedin any equipment. Refer to 40 CFR 761 for PCBdetails. PCBs are powerful solvents. Handling anddisposal information and special gloves are re-quired. Check condition, alignment, and adjustmentof contacts. Verify that contacts surfaces bear withfirm, even pressure. Use a fine file to dress roughcontacts; replace pitted or burned contacts. Wipeclean all parts normally immersed in liquid, removetraces of carbon that remain after the liquid hasdrained. Inspect insulating parts for cracks, orother damage requiring replacement. Test the di-electric strength of the liquid, using a 0.1 inch gapwith 1.1 inch diameter disk terminals. If strength isless than 22 kV, remove and filter or replace withnew liquid having a dielectric strength of at least 26kV. Filter the liquid whenever inspection shows ex-cessive carbon, even if its dielectric strength is sat-isfactory, because the carbon will deposit on insulat-ing surfaces decreasing the insulation strength.Liquid samples should be taken in a large-mouthedglass bottle that has been cleaned and dried withbenzene. Use a cork stopper with this bottle. Drawtest samples from the bottom of the tank after theliquid has settled. The samples should be from thetank proper and not from the valve or drain pipe.Periodically remove the liquid from the tank andwipe the inside of the tank, the tank linings, andbarriers to remove carbon. Inspect breaker and op-erating mechanisms for loose hardware and missingor broken cotter pins, retaining rings, etc. Checkadjustments and readjust when necessary (refer tothe manufacturer’s instruction book). Clean operat-ing mechanism and lubricate as for air-magnetictype breakers (refer to the manufacturer’s instruc-tion book). Before replacing the tank, operatebreaker slowly with maintenance closing device toverify there is no friction or binding to prevent orslow down its operation; then, check the electricaloperation. Avoid operating the breaker any morethan is necessary when testing it without liquid inthe tank. It is designed to operate in liquid andmechanical damage can result from excessive op-eration without it. When replacing the tank, fill tothe correct level with liquid, be sure the gaskets areundamaged and the tank nuts and flange nuts ongauges and valves are tightened properly to preventleakage.

.-

(f) Service air-blast type circuit breakers.Circuit breakers should be serviced (tested, exer-cised, and calibrated) at intervals not to exceed twoyears (refer to AR 420-43). Withdraw the breakerfrom its housing for maintenance. Circuit breakers

-

TM 5_685/NAVFAC MO-912

are designed to perform up to 5000 and 3000 opera-tions for 1200 ampere or 200 ampere breakers, re-spectively, without major overhaul. More frequentservicing may be necessary if operating conditionsare severe. Inspection and servicing should be per-formed after every fault clearing operation. Refer toinstructions provided by the manufacturer. Wipeinsulating parts, including bushings and the insideof box barriers; clean off smoke and dust. Repairmoderate damage to bushing insulation by sandingsmooth and refinishing with a clear insulating var-nish. Inspect alignment and condition of movableand stationary contacts. Check their adjustment asdescribed in the manufacturer’s instruction book. Tocheck alignment, close the breaker with pieces oftissue and carbon paper between the contacts andexamine the impression. Do not file butt-type con-tacts. Contacts which have been roughened in ser-vice may carry current as well as smooth contacts.Remove large projections or “bubbles” caused by un-usual arcing, by filing. When filing to touch up, keepthe contacts in their original design; that is, if thecontact is a line type, keep the area of contact lin-ear, and if ball or point-type, keep the ball or pointsshaped out. Check arc chutes for damage. Replacedamaged parts. When arc chutes are removed, blowout dust and loose particles. Clean silver-platedbreaker primary disconnecting devices with alcoholor silver polish (refer to the manufacturer’s instruc-tion book). Lubricate devices by applying a thin filmof approved grease. Inspect breaker operatingmechanism for loose hardware and missing or bro-ken cotter pins, retaining rings, etc. Examine cam,latch and roller surfaces for damage or excessivewear. Clean and relubricate operating mechanism(refer to the manufacturer’s instruction book). Lu-bricate pins and bearings not disassembled. Lubri-cate the ground or polished surfaces of cams, rollers,latches and props, and of pins and bearings that areremoved for cleaning. Check breaker operatingmechanism adjustments and readjust as describedin the manufacturer’s instruction book. If adjust-ments cannot be made within specified tolerances,excessive wear and need for a complete overhaul isindicated. Check control device for freedom of op-eration. Replace contacts when badly worn orburned. Inspect breaker control wiring for tightnessof connections. After the breaker has been serviced,operate it slowly with closing device to check ab-sence of binding or friction and check that contactsmove to the fully-opened and fully-closed positions.Check electrical operation using either the test cabi-net or test couplers.

(g) Service vacuum circuit breakers. Thisbreaker has primary contacts enclosed in vacuumcontainers (flasks), and direct inspection or replace-

ment is not possible. The operating mechanism issimilar to that used in other medium voltage circuitbreakers, and the general outlines are the same formaintenance work. The enclosures are similar. Fig-ure 5-11 shows a breaker with the primary electri-cal contacts exposed. The stationary contact is sol-idly mounted; the moving contact is mounted in theenclosure with a bellows seal. Contact erosion ismeasured by the change in external shaft positionsafter a period of use. Consult the manufacturer’sinstruction book. High voltage applied during test-ing may produce X-ray emission. Personnel per-forming a hi-pot test must stay behind a protectiveshield during testing. Condition of the vacuum ischecked by a hi-pot test applied every maintenanceperiod. Consult manufacturer’s instruction book fortest procedures. The contacts in a vacuum circuitbreaker cannot be cleaned, repaired or adjusted.The vacuum bottle is usually replaced if the testindicates a fault.

5-5. Transfer switches.During actual or threatened power failure, transferswitches are actuated to transfer critical electricalload circuits from the normal source of power to theauxiliary (emergency) power source. When normalpower is restored, the transfer switches either auto-matically retransfer their load circuits to the nor-mal supply or must be transferred manually. Volt-age and frequency-sensing relays are provided tomonitor each phase of the normal supply. The relaysinitiate load transfer when there is a change involtage or frequency in any phase outside of prede-termined limits. Additionally, the relays initiateretransfer of the load to the normal source as soonas voltage is restored in all the phases beyond thepredetermined pick-up value of the relay. A transferswitch obtains its operating current from the sourceto which the load is being transferred.

a. Types of transfer switches. There are two typesof transfer switches: electrically operated or manu-ally operated. Electrically operated transferswitches also come with an optional bypass func-tion.

( 1) Electrically operated. An electrically oper-ated switch obtains its operating current from thesource to which the load is being transferred. Aseparate voltage supply is used in some systems.Electrically operated switches consist of three func-tional elements: main contacts to connect and dis-connect the load to and from the sources of power;sensing circuits to constantly monitor the conditionof the power source and provide the informationnecessary for switch and related circuit operation;and transfer mechanism to make the transfer fromsource to source.

5-13


(a) Circuit breaker type. Circuit breakertransfer switches are mechanically held devices us-ing two circuit breakers. Usually the breaker han-dles are operated by a transfer mechanism whichprovides double-throw switching action connectingone circuit terminal to either of two others. Thetransfer mechanism is operated electrically by aunidirectional gear motor (motor and integralspeed-reducing gearbox) or by dual motor operatorswith all parts in positive contact at all times. Theseswitches can also be operated manually and haveprovisions for disengaging the generator when nec-essary.

(b) Neutral position. Some transfer switcheshave a neutral position. However, the switch is me-chanically and electrically interlocked so that a neu-tral position is not possible during electrical opera-tion. Also, load circuits cannot be connected by theswitch to normal and emergency sources simulta-neously whether the switch is operated electricallyor manually.

(c) Contactor type. Contactor type transferswitches have mechanically or electrically heldcontactors with a command load bus. The switchesare mechanically and electrically interlocked so thata neutral position is not possible under normal elec-trical operation. Additionally, the load circuits can-not be connected to normal and emergency sourcessimultaneously.

(2) Bypass function. An electrically operatedtransfer switch can be provided with a bypass func-tion. The bypass function manually transfers thepower around the automatic transfer switch. Theelectrically operated switch can then be tested, re-moved, and repaired. The bypass function may ormay not cause a momentary interruption to the loaddepending upon the manufacturer. The bypass ispurely a manual function, therefore, if the source towhich the bypass is connected fails the bypass mustbe manually transferred to the alternate source.Bypass transfer switches are only used in the mostcritical applications where the load is operationalcontinuously.

(3) Manually operated. Manual transferswitches are mechanically held devices using twocircuit breakers operated by a handle. All parts arein positive contact at all times. The switch is me-chanically interlocked; it is impossible for the loadcircuits to be connected to normal and emergencysources simultaneously. Manually operated transferswitches are available with single or dual operatinghandles. A common operating mechanism across thetwo breakers mechanically connects and operatesthe breakers.

b. Operation. Transfer switches have two operat-ing modes: automatic and non-automatic.

5-14

(1) Automatic. Automatic transfer switcheshave voltage sensing relays for each phase. Thesensing relays are connected to the normal powerbus, behind the protecting devices.

(a) The transfer switch is connected to thenormal power source under normal conditions.When the sensing relays detect a sustained drop inthe voltage of the normal power source, the relayswill automatically start the auxiliary generator. Thetransfer switch operates upon a sustained drop involtage in any phase of the normal source (approxi-mately a 30 percent drop and delay of about twoseconds) to start the auxiliary generator.

(b) When voltage and frequency of the auxil-iary generator are at rated values, and the normalpower source is still below normal, the automaticcontrol will transfer the load to the emergencysource.

(c) Upon return of normal power to within 10percent of rated voltage on all phases and after apreset time delay, the switch automatically trans-fers the load to the normal source. Usually the aux-iliary generator will run unloaded for about fiveminutes after the transfer, before it shuts down.The controls automatically reset for the next emer-gency start.

(d) Usually the controls of a power transfersystem have a test switch. This permits simulationof failure of the normal power source and test oftransfer switch operation.

(e) Power transfer indicators are provided inmost automatic transfer systems to indicate the cur-rently used power source. Usually an amber lightmarked “Emergency Power” shows that the systemis on emergency power when illuminated. A whitelight marked “Normal Power” shows that the sys-tem is receiving power from its normal source whenilluminated.

(2) Nonautomatic. In nonautomatic operation,an operator is needed to manually transfer to orfrom the emergency power source. The operator canusually make the transfer without opening an en-closure. The transfer is usually based on instrumentindications and is made by placing the transferswitch in the required emergency or normal posi-tion.

(a) Power transfer indicators are providedfor the operator. An amber light (Emergency Power)shows that the system is on emergency power whenilluminated. A white light (Normal Power) showsthat the system is receiving power from its normalsource when illuminated.

(b) The operator is usually provided with anoverride switch which bypasses the automatictransfer controls. This feature permits indefinite

connection of the emergency power source regard-less of the condition of the normal power source.

c. Service practices. Service practices for transferswitches consist of a complete maintenance pro-gram that is built around records and visual inspec-tions. The program includes appropriate analysis ofthese records.

(1) Record keeping. Equipment and system logsheets are important and necessary functions ofrecord keeping. The log sheets must be specificallydeveloped to suit auxiliary use.

(2) Troubleshooting. Use recognized industrialpractices as the general guide for transfer switchand systern troubleshooting. Troubleshooting of sys-tem circuits that are not performing according tospecifications and to the required performance levelshould be accomplished as follows: refer to engi-neering data and drawings pertaining to the par-ticular plant.

(a) The user should refer to manufacturer’sliterature for specific information on individualtransfer switches.

(b) Perform general troubleshooting of thetransfer switch if a problem develops. Refer to themanufacturer’s literature for specific information.Usually, all control elements are renewable fromthe front of the switch without removing the switchfrom its enclosures and without removing the mainpower cables.

5-6. Regulators.A voltage regulator maintains the terminal voltageof an alternator or generator at a predeterminedvalue. Voltage is controlled by regulating thestrength of the electromagnetic field produced inthe alternator exciter. A voltage regulator automati-cally overcomes voltage drop within the alternatorby changing field excitation automatically as it var-ies with the load.

a. Types of regulators. The types of voltage regu-lators are electromechanical, static voltage, andstatic exciter.

(1) Electroo -mechanical voltage regulators.These regulators usually have a servo-control sys-tem with three principal elements.

(a) First is a voltage sensing device with avoltage regulating relay. The device monitors theoutput voltage and sends a signal to the controlcircuits.

(b) Second i s an amplifying section with orwithout time delay, which amplifies the voltage sig-nal.

(c) Third is a motor drive which responds tothe signal by moving a tap changer or inductionregulator in a direction to correct the voltage.


(2) Static voltage regulators. A static regulatorusually has a static voltage sensor instead of avoltage-regulating relay.

(a) Operation. The voltage sensor output isapplied to a solid-state or magnetic amplifier and adiscriminator circuit. Signals are thereby providedfor changing alternator output to raise or lower thevoltage as required. The voltage zone between ini-tiation of raising or lowering control action is calledthe voltage band. The band must be more than theminimum correction obtainable through the regula-tor or regulator hunting will occur.

(b) Accessories. Accessories include eitherthermal delay relays or a resistance capacitancenetwork to provide time delay for load trend correc-tion. Time delay retards the signal until accumu-lated time outside the voltage limit, less accumu-lated time inside the voltage limit, exceeds the timedelay setting.

(3) Static exciter regulators. A static exciterregulator supplies the alternator field with DC volt-age obtained from a three-phase, full wave bridgerectifier.

(a) Operation. A small part of the alterna-tor’s output goes to the regulator which meters therectified DC voltage back to exciter’s field windings.The rectified DC voltage produces a 60 cycle ripple.If the ripple gets into the field windings, an electri-cal discharge from windings to shaft can occur. Afilter can be used to reduce ripple. The discharge iscaused because copper in the field windings and themetal shaft act like the plates in a capacitor. Thisaction may result in shaft and bearing pitting andeventual bearing failure. A static exciter is a manu-factured subassembly, assembled and wired at themanufacturer’s plant, usually using one or moresilicon rectifiers to convert AC voltage to DC. Thesubassembly usually includes a regulator and a fil-ter. Refer to the manufacturer’s literature for testand adjustment details.

(b) Accessories. Accessories include eitherthermal delay relays or a resistance capacitancenetwork to provide time delay for load trend correc-tion (refer to para 5-6a(2)(b). A suppressor circuit orripple filter is usually provided to bypass ripple toground before it gets to the generator field.

b. Service practices. Service practices for voltageregulators consist of a complete maintenance pro-gram that is built around records and visual inspec-tions. The program includes appropriate analysis ofthese records.

(1) Record keeping.Equipment and system logsheets are important and necessary functions ofrecord keeping. The log sheets must be specificallydeveloped to suit auxiliary use.

5-15


(2) Troubleshooting. Use recognized industrialpractices as the general guide for servicing. Refer tomanufacturer’s literature for specific informationon individual voltage regulators. Troubleshootingprocedures include the following:

(a) Check voltage for compliance with manu-facturer’s specifications.

(b) Check fo r 1 oose or insecure electrical con-nections.

Table 5-2. Switchgear equipmenttroubleshooting-Continued

Note

liRefer to manufacturer’sindividual equipment.

terature for information onspecific

RELAYS FAILING TO TRIP BREAKERSContacts improperly adjusted Adjust contacts. verify proper wipe

(c) Check for correct setting, refer to manu-facturer’s literature. Open or short circuit in relay con-

(d) Check for unregulated voltage. Refer tomanufacturer’s literature.

(e) Check the enclosure. Should be weathertight.

(f) Check motor for proper operation andloose connections. Clean and lubricate as required.Refer to manufacturer’s literature for details.

(g) Voltage regulators and associated equip-ment are normally mounted within switchgearequipment and are interconnected with differentcomponents. The proper operation and trouble-shooting of voltage regulator equipment can dependon these different components. Perform the proce-dures in the following table:

nectionsCheck to verify that voltage is ap-plied and that current is passingthrough relay in question

of target andImproper applicationholding coil

ofVerify proper tripping actiontarget and holding coi IS

Faulty or improperly adjusted tim-ing devices

If timing device is of bellows oroil-film type, clean and adjust. if ofinduction-disk type, check for me-chanical interference. Refer tomanufacturer’s literature

NOISES DUE TO VIBRATING PARTSLoose bolts or nuts permitting ex-cessive vibration

Tighten to proper torque value

Loose laminations in cores oftransformers, reactors, etc.

clampsTighten loose nuts or coreto proper torque value

CONNECTIONS OVERHEATING

Table 5-2. Switchgear equipment troubleshooting. current due to overloadIncrease ofconditions

Increase the carrying capacity (in-crease the number or size of con-

Note ductors) Remove excess current

Refer to manufacturer’s literature for specific information onindividual equipment.

from circuit

Connecting bolts and nuts not tight Tighten ail bolts and nuts to propertorque value

Cause Remedy

WATTHOUR METER INACCURATEMeter may be dirty or damaged Install new meter, return faulty

meter to repair depot for repair andcalibration

FAILURE IN FUNCTION OF ALL INSTRUMENTS AND DEVICESHAVING POTENTIAL WINDINGS

Loose nuts, binding screws or bro-ken wire at terminals

Tighten all loose connections toproper torque value or repair bro-ken wire circuits

Faulty wiring or connections Inspect and repair as necessary

WATTHOUR METER FAILS TO REGISTERBlown potential transformer fuse, Renew blown fuses Check wiringbroken wires or other fault in con- and repair as requirednections

Blown fuse in potential transformercircuit

Renew blown fuses

Open circuit in potential trans-former primary or secondary cir-cuits

Repair open circuit and check en-tire circuit for continuity and goodcondition

Wedge or block accidently left attime of test or inspection

Remove wedge or block Verify thatmeter is in good operating condi-tion

BREAKER FAILS TO TRIPMechanism binding or sticking Lubricate breaker mechanism; refercaused by lack of lubrication to manufacturer’s instructions

DAMAGED CONTROL, INSTRUMENT TRANSFER SWITCH,OR TEST BLOCKS

Burned or pitted contacts Dress or clean burned contacts orreplace with new contacts if neces-sary

Mechanism out of adjustment Adjust all mechanical devices,(toggles, stops, buffers, openingsprings, etc.) according to manu-facturer’s instructions

RELAYS FAILING TO TRIP BREAKERSImproper setting Adjust setting to correspond with

circuit conditions. Refer to manu-facturer’s instructions

Failure of latching device Examine surface of latch, replacelatch if worn or corroded. Checklatch wipe, adjust according tomanufacturer’s instructions

Damage trip coil Replace damaged coilDirty, corroded or tarnished con-tacts

5-16

Clean contact with knife or tile Donot use emery cloth or sand-paper


Table 5-2. Switchgear equipmenttroubleshooting-Continued

Note


Faulty connections (loose or bro-ken wire) in trip circuit

Repair faulty wiring, tighten allbinding screws to proper torquevalue

OIL CONTAMINATEDCarbonization from too many op- Drain oil and filter, clean or re-erations place. Add fresh oil. Clean inside

of tank and all internal parts ofbreaker; refer to manufacturer’sinstructions

Condensationconditions

Overheating Eliminate cause of overheating

due to atmospheric Same procedure as above

5-7. Instrumentation.Switchgear instrumentation, based on the complex-ity of the complete system, may include all or anycombination of indicating, recording, and meteringinstruments. Potential and current transformersare used to isolate instrument circuits from thepower circuit. Usually, the secondary winding ofpotential transformers is rated at 120 volts. Currenttransformer output is 5 amperes.

a. Types of instrumentation. Instrumentation in-cludes indicating and recording types.

b. Application. Information related to instrumenttransformer application is covered in paragraphs5-3b( 2) and 5-3c(2).

(1) Voltage. Voltage values are indicated by avoltmeter.

(2) Current. Current values are indicated by anammeter.

(3) Power. Power values are described as watts,vars and power factor (refer to para 4-7e for addi-tional information).

(a) Watts. Watts or kilowatts (units of electricpower) are indicated by a wattmeter.

(b) Vars. Vars or kilovars (units of reactivepower) are obtained by multiplying effective valueof current, effective value of voltage and the sine ofthe angular phase difference between current andvoltage.

(c) Power factor. Power factor, the ratio ofactive power to apparent power, is displayed on apower factor meter. The meter scale is usuallygraduated in percentage power factor.

(4) Frequency. Frequency of alternating cur-rent is indicated on a frequency meter. The meterscale is usually graduated in 50/60 Hertz.

(5) Speed. Rotational speed of the prime moveris indicated by a tachometer in revolutions perminute (rpm). Generating systems covered hereinusually use an impulse tachometer, including theinductor and eddy current types. These tachometersuse a magnetic pick-up to sense speed.

(6) Temperature. Several temperature values(including coolant, lubricating oil and exhaust) areusually required to assure safe prime mover opera-tion. Each value is monitored by a sensing devicewith a remote indicator or thermometer. The sens-ing device can be thermocouple or a combination ofsensing bulb and capillary tube.

(a) Thermocouple. A thermocouple consists ofa pair of electrical conductors, each of differentmetal, which are joined at the end adjacent to thetemperature to be measured. A thermal emf is pro-duced at the junction of the conductors. The otherend of each conductor is connected to a voltmeterwhich measures and indicates the thermal emf.

(b) Sensing bulb and capil lary tube. T h esensing bulb and capillary tube contain a specificamount of liquid or gas whose pressure varies withtemperature. The variation appears on the ther-mometer and represents the temperature of coolant,oil or exhaust.

(7) Pressure. Pressure in the prime mover isindicated by sensing devices and remote gauges.Usually a bourdon tube is used. The variation ap-pears on the gauge and represents lubricating oil orother pressure. Other pressure values may beshown on the system instrument panel dependingon the type of prime mover and the overall systemrequirements. These pressure values include start-ing air, turbo boost, scavenging air, exhaust mani-fold and fuel gas. Gauges or meters are used forindication as required.

(8) Fuel level. Various methods are used forfuel level measurement. Fuel in underground stor-age tanks can be measured by immersing a cali-brated dip stick in the tank. For day tanks, a glasssight-gauge or a float actuated gauge can be used tomeasure the quantity of liquid fuel, Remote indica-tors using pneumatic, electric or hydraulic devicesare also used.

(9) Running time. The amount of time an aux-iliary generating system operates is a required partof system record keeping. Time is usually recordedon a digital measuring device or counter located onthe system instrument panel. Usually the counter isused with electric or electronic circuitry. An electricsystem usually has an AC synchronous motor thatis geared to the counter. Accuracy of motor and


counter depends on the frequency of the generatoroutput voltage. An electronic system also recordsoperating time on a digital measuring device. Thissystem measures time by counting the number ofcycles produced by the frequency of the generatoroutput voltage. Counter indications are propor-tional to frequency vs time.

5-8. Relays.Relays are used with the automatic controls for aux-iliary power generating systems. A relay responds toelectrical or other operating parameters and causesan abrupt change in the control circuits when themeasured values change. A relay consists of a sens-ing element and a control element with contacts.

a. Types of relays. Relays used in switchgear in-clude general purpose and protective types.

(1) General purpose. General purpose relaysfunction as part of regulation and verification de-vices throughout the system including the primemover.

(a) Industrial. Portions of electrical systemsare energized or de-energized under normal or ab-normal conditions by relays. Since the relays areusually used with subsystems or equipment circuitbreakers, the overall operating plan must be electri-cally coordinated. Coordination is usually accom-plished by designing the system circuitry to selec-tively initiate the opening or closing of the relays.Relays constantly monitor the power system.

(b) Overload. 0 verload relays are used toprovide overload protection for the auxiliary motors.When an overload condition occurs in any of thethree phases in which heaters are inserted, it willcause the relay to trip.

(c) Time delay. Relays employed for time de-lay purpose are usually solid-state type. Some pneu-matic relays may still be in use. Pneumatic relaysutilize a bellows type arrangement to provide thetime delay. They can be adjusted for time periods ofless than a second to several minutes.

(d) Solid-state. Solid-state relays derive theirtime delay from a combination of several electroniccomponents. They are also adjustable between frac-tions of a second to several minutes.

(e) Voltage sensitive. Voltage sensitive relaysare used to sense an increase or decrease in a spe-cific voltage. They provide an output signal whenthe voltages pass the preset level.

(2) Protective relays. Protective relays detect,isolate, and/or indicate abnormal electrical condi-tions. The operation of circuit breakers or otherprotective devices is initiated by relays as required.Some of the electrical hazards protected against areshort circuit, overcurrent, over or under voltage,and phase or frequency irregularities. Relays in-

5-18

stalled to protect generator stator windings frominternal shorts and overheating are sensitive tofaults in the generator and do not respond to faultsoutside the generator. These relays act rapidly toprevent damage to the generator and isolate thegenerator from the system. Relay action includesde-energizing the generator field winding. Protec-tive relays are provided in systems when reversepower flow occurs. Those relays operate on a succes-sion of power reversals and current impulses todetect loss of synchronism. Protective relays includethe following types:

- -

(a) Overcurrent. Overcurrent relays functionwhen current flow exceeds the normal or desiredvalue. Induction disk relays with time delay andcup type relays (without time delay) are known aselectromechanical type relays. Solid state relays arenormally used on more recently installed equip-ment.

(b) Overvoltage. Overvoltage relays functionwhen voltage exceeds the normal or desired value.Induction disk relays with time delay and cup typerelays without time delay are used.

(c) Undervoltage. Undervoltage relays func-tion when voltage is less than normal or desiredvalue. Induction disk relays with time delay may beused in a balanced position between minimum andmaximum voltages.

(d) Reverse power. Reverse power relaysfunction whenever power flows in the reverse direc-tion from normal or desired. These relays detect lossof synchronism.

- -

(e) Underfrequency. Underfrequency relaysfunction whenever the desired frequency becomesless than normal value. This condition is usuallythe result of reduced prime mover speed and may becaused by the prime mover governor or excess elec-trical load.

(f) Differential. Differential relays functiondue to the difference between two quantities of thesame kind such as, two currents or two voltages.Differential relays, usually used to detect statorwinding electrical failure, respond to current per-centage differences. Current or voltage transform-ers used in differential network should be inmatched sets. Percentage differential relays arealso used to prevent relay operation for faults due tocurrent transformer ratio error outside the pro-tected zone. In this application, the overcurrent re-lay operates instantly when there is a bus shortcircuit but will not operate if a current transformersecondary opens. The contacts of the two relays areconnected in series.

(g) Current balance. A current balance relaycircuit monitors two or more current circuits andprovides an output if the difference between any

---


two exceeds the setting of the relay. The relaysenses the difference between the current of onegenerator and the current of another generator orthe average of all other generators. Relay outputmay be used to trip bus tie contactors and split aparallel system to remove an unbalance.

(h) Ground fault protection. Ground faultprotection is usually provided by a ground sensorrelay which measures the sum of currents in thelines to the load in a three-phase system. Anotherrelay is sometimes added to the transformerneutral-to-ground connection for backup.

b. Testing of relays. Periodic testing of relays isconsidered preventive maintenance. The preventivemaintenance program is built around records andvisual inspections and includes analysis of therecords.

(1) The frequencyy of testing is dependent onthe variables involved i.e., type of relay, environ-mental conditions, history, and experience. The am-bient operating temperature must be recorded.Most relays have draw-out construction so that arelay can be separated from its enclosure. Discon-nection for test or repair is usually not required.

(2) Checks and tests to be performed are deter-mined by the type of relay. The schedule for perfor-mance of tests should comply with the requirementsof AR 420-43. Proceed as follows:

(a) Inspect the relay cover before testing. Re-move dust and other foreign matter to prevent itfrom entering the relay. Record the inspection re-sults.

(b) Check relay for “flag” indication. Also,check cover glass for fogging. If fogging is excessive,investigate the cause.

(c) Check all connections for proper tight-ness. If necessary, tighten to proper torque value.

(d) Check armature and connect gaps. Com-pare with previous measurements. Adjust gaps ifnecessary and refer to manufacturer’s instructions.

(e) Check contacts for burned or eroded con-dition. Burnish if necessary and refer to manufac-turer’s instructions.

(f) Verify proper contact operation. Open orclose contacts to observe proper trip or reclose ac-tion and refer to manufacturer’s instructions.

(g) Apply current or voltage to verify thatpickup is within manufacturer’s tolerances.

(h) Reduce the current until the relay dropsout or fully resets. Verify that there is no bindingduring operation and refer to manufacturer’s in-structions.

(i) Verify that related devices such as capaci-tors are functioning properly and refer to manufac-turer’s instructions.

(j) Note that differential relays are usuallyvery sensitive devices that use polarized sensingcircuitry. Repeat the pickup test. Use the secondtest for comparison with previous and future testdata. Refer to manufacturer’s instructions.

c. Record keeping. Equipment and system logsheets are important and necessary functions ofrecord keeping. The log sheets must be specificallydeveloped to suit auxiliary use.

d. Troubleshooting. Perform troubleshooting pro-cedures when abnormal operation of the system orequipment is observed. Maintenance personnelmust then refer to records for interpretation andcomparison of performance data, i.e., log sheets.Comparisons of operation should be made underequal or closely similar conditions of load and ambi-ent temperature. The general scheme for trouble-shooting is outlined in the following table.

Table 5-3. Relay troubleshooting.

Refer to manufacturer’sindividual equipment.

Note


Cause Remedy

MAGNET-OPERATED INSTANTANEOUS TYPEHigh Trip Action

Faulty coil Install coil with correct rating

Low Trip ActionShorted turns on high trip Test coil and replace with new coil

if found defective

Mechanical binding; dirt, corrosion Clean parts

Assembled incorrectly See manufacturer’s instructions

MAGNET-OPERATED INVERSE-TIME TYPESlow Action Trip

Fluid too heavy, vent too small, or Change fluid and open venttemperature too low slightly, regulate temperature

Worn parts Replace and adjust

Worn, broken partsFast Trip Action

Replace and adjust

Fluid too light, vent too large ortemperature too high

Change fluid to proper grade Closevent slightly or regulate tempera-ture. Clean dashpots and refill withfresh fluid or proper grade

THERMAL TYPEFails to Trip Causing Motor Burnout

Wrong size heater Check rating with recommenda-tions on instruction sheet

Mechanical binding; dirt, corrosion Clean and adjust

Relay damaged by short circuit Replace relay

Motor and relay in different ambi- install motor and control near eachent temperature other or make temperature uniform

for both

5-19


Table 5-3. Relay troubleshooting-Continued

Note


Cause Remedy

Trips at Too Low TemperatureWrong heater Check rating with manufacturer’s

instruction sheet

Assembled wrong See manufacturer’s instructions

Relay in high ambient temperature Install controls closer to each otheror make temperature uniform

Fails to ResetBroken mechanism; worn parts; Replace broken parts, clean andcorrosion, dirt adjust. Install new relay

5-9. Miscellaneous devices.Miscellaneous devices include control switches,push buttons, indicating lights, batteries, surge ca-pacitors, lightning arresters, maintenance tools,test equipment, and fuses.

a. Control switches and push buttons. Switchgearand related control panels contain complete controlsfor all functions of the auxiliary generator equip-ment. Control for voltage regulation, phase adjust-ment, current compensation, engine operating pa-rameters as well as engine start, stop, and runningspeed, battery charging and brightness or dimmingof indicator lights are usually provided.

b. Indicating lights. White indicating lamps withcolored caps are used to show breaker positions.Green lights indicate open breakers, red lights indi-cated closed breakers. White lights, when used, areenergized from potential transformers to indicatelive circuits. Some stations include amber or orangelights to indicate that the circuit has been trippedautomatically. Low voltage lamps, connected in se-ries with appropriate resistors, are usually used toreduce lamp size and glare. Red and green lightsare usually wired so that they are energizedthrough the trip coil of the breaker. An opening inthe trip coil circuit is indicated by a dark unlit lamp.Similar indicating lamps and colored caps are usedto indicate normal and abnormal conditions forother control functions of the system.

c. Batteries. Storage batteries and battery sys-tems are frequently a part of an auxiliary powersystem. Batteries are used for prime mover crank-ing, or an uninterruptible power system. The bat-teries maintain a charge through the application ofa “floating” battery charger. As the battery dis-charges its energy the charger increases its chargerate by increasing the flow of current into the bat-tery. The converse is true as the battery reaches afull charge, a very small current flows into the bat-

5-20

tery. In addition, batteries provide power forswitchgear control and power to trip some circuitbreakers. Most applications for auxiliary power usesome form of “wet” lead acid battery, however, somesystems use “dry” nickel cadmium (nicad) batteries.Both types of batteries produce direct current re-peatedly by chemical reactions. Batteries must berecharged after each use to restore their power. Wetcell batteries require scheduled maintenance. Thisincludes a visual inspection of all cells, a weeklyhydrometer reading of the sample cell, and monthlyreadings of floating voltage, water level, hydrom-eter, and temperature of each cell. Cell connectorsmust be kept. clean and tight to prevent heating dueto high resistance or voltage drop. Tops of cells mustbe kept free of dirt or conductive materials. Charg-ing area must be exhausted to positively preventhydrogen build up and explosion.

-__

d. Surge capacitors. Surge absorbing capacitorsare sometime used, with or without lightning ar-resters, to modify the shape of the surge voltagewave. These capacitors operate at voltages of 240,480, 600 and higher for single or three-phase opera-tion. Capacitor banks, formed by individual unitsconnected in parallel, are sometimes used. Fusesand circuit breakers with time-current characteris-tics are used to prevent rupture of the capacitorcase under severe conditions. Safety precautionsmust be observed when working on capacitors.

(1) Surge capacitors using polychlorinatedbiphenyls (PCBs) may still be in use. Refer to 40CFR 761. Since PCBs are carcinogenic and are notbiodegradable, some restrictions to their use apply.

(2) Special handling is required if PCBs areused in any equipment. PCBs are powerful solvents.Handling and disposal information and specialgloves are available in the base engineer’s office.

e. Lightning arresters. A lightning arrester (aprotective device) limits voltage caused by a light-ning strike and bypasses the related current surgeto a ground system which absorbs most of the strikeenergy. An overvoltage condition can also be causedby a fault in the electrical system.

(1) There are two general types of arresterdesigns, valve type and expulsion type. The valvetype has one or more sets of spark gaps (seriesconnected) which establish spark-over voltage, in-terrupt the flow of current, and prevent highcurrent flow. The expulsion type has an arc extin-guishing chamber in series with the gaps to inter-rupt the power frequency current which flows afterthe gaps have been sparked over. Design refine-ments include using oxide film coated componentsand sealing the inner components in a chamberfilled with an inert gas. Aluminum cells are used insome units.


(2) Installed lightning arresters can retain alethal electric charge. Accordingly, lightning arrest-ers must be considered as loaded to full circuit po-tential unless disconnected from the circuit andgrounded.

f. Special maintenance tools. Always use theproper tool for the job being done. Avoid the use ofimprovised tools or tools in poor condition. Storetools not in use properly.

(1) Hand tools include the following: screw-drivers, pliers, wrenches, wire insulation strippers,and wire cutters.

(2) Powered hand tools include the following:hydraulic, pneumatic and electrical. Unless an elec-trical tool is battery powered or double insulated,make sure the tool has a line cord with a groundedconductor and polarized grounding plug. Make surethe receptacle to be used is properly grounded.

(3) Machine tools include grinding wheels andcutting tools.

g. Test equipment. Before using any test equip-ment make sure that it has valid calibration certifi-cation. Test equipment required for switchgearmaintenance usually includes many or all of thefollowing items.

(1) Multim te er. The multimeter is sometimescalled a volt-ohm-milliammeter or VOM. It is asingle test instrument with a number of differentranges for measuring voltage, current, and resis-tance.

(2) Voltmeter. An instrument used for measur-ing voltage. Its scale indicates microvolts, millivolts,volts or kilovolts.

(3) Voltamm te er.. An instrument used as eithera voltmeter or an ammeter.

(4) Ohmmeter.. An instrument used for measur-ing resistance. It consists of a DC milliammeter, aDC source, and a resistor network.

(5) Ammeter. An instrument that measures theamount of current in amperes. Its meter shows cur-rent value in microamperes, milliamperes, orkiloamperes.

(6) Frequency meter. An instrument for mea-suring the frequency of an alternating current. Itsscale shows Hertz (cycles per second), kiloHertz(kilocycles), or megaHertz (megacycles).

(7) Wattmet er.. An instrument for measuringelectric power. Its scale is usually graduated inwatts or kilowatts.

(8) Megohmmeter. A device that is a high rangeohmmeter, sometimes referred to as a megger. Itconsists of a hand driven, motor driven, or batterydriven generator as the DC source, and a meter. Itis used to measure insulation resistance and otherhigh resistance. It can be used to check for continu-ity, grounds, and short circuits.

(9) Electrical analyzer: An instrument for mea-suring the various parameters of AC circuits. Itconsists of a voltmeter, ammeter, wattmeter, andpower factor meter. The analyzer also includes twocurrent transformers and switches necessary foruse. It can be used for testing insulation.

(10) Certification. Test equipment should havevalid calibration certification.

h. Fuses. Fuses detect circuit overload conditionsand open when there is too much current flowing.Fuses are the safety valves of the installation’s elec-trical system and provide the most economical typeof circuit protection.

(1) Application. There are many types of fuseswith various characteristics. Always verify that afuse, whether a new or replacement unit, is of theproper type and rating before installing. Never ar-bitrarily replace one type of fuse with another fuseof the same physical size just because it fits the fuseholder. The fuse used should have the correct cur-rent and voltage ratings, proper time delay andcurrent limiting characteristics and an adequate in-terrupting rating to protect the circuit and its com-ponents. Fuse holders should never be altered orforced to accept fuses which do not fit.

(2) Construction. A fuse consists of two mainparts: the fusible link and the enclosing housing orbody. The link is a metallic alloy that melts whenexcessive current flows through it, thereby breakingthe circuit. When the current heats the alloy to itsmelting point, the link breaks and an arc forms.Melting continues rapidly until the resultant gap istoo wide for the arc to span. A fuse usually can carrya 100 percent load indefinitely and will blow in aspecified time at 150 percent overload. The follow-ing fuse types are usually used.

(a) Current limiting fuses. Current limitingfuses are used where necessary to limit the amountof fault energy flowing through a fuse to the circuit.A fuse must clear a fault in less than l/2 cycle of thefault current sine wave to be considered a currentlimiting fuse. If the fault current is allowed to flowfor % cycle or more, the maximum (peak) fault cur-rent is passed through the fuse. A current limitingfuse must act quickly to limit the energy let throughthe fuse to the protected circuit. The total clearingtime of a fuse is made up of two components; themelting time, and the arcing time. The fault currentreaches maximum at the conclusion of the meltingtime, much less than l/4 cycle. An arc is establishedinside the fuse at the conclusion of the melting time.The arc presents a high resistance to the flow offault current and the current decays to zero, clear-ing the fault. Whenever possible de-energize thefuse-holder circuit before removing or installing afuse.

5-21


(b) Metal-en Zc osed fuse. Fuse enclosed in anoil filled metal housing and used (up to 7,500 volts)for protecting transformer banks and other distri-bution elements. Refer to the manufacturer’s litera-ture for details.

(c) Glass-enclosed fuse. Fuse enclosed in aglass tube filled with arc quenching liquid. Carbontetrachloride is the liquid frequently used. Refer tothe manufacturer’s literature for details.

(d) Expilsion fuse. Fuse enclosed in a fibertube filled with dry (powdered) boric acid. When thefuse element blows, the boric acid produces a gaswhich aids in promptly deionizing the arc. Used oncircuits up to 138 kV. Refer to the manufacturer’sliterature for details.

(3) Checks and examinations. Examine fuseterminals and holders for discoloration caused byheat from poor contact and/or corrosion. Checks tobe performed are determined by the type of fuse andfuse holder, proceed as follows:

(a) Inspect fuse and fuse holder contact sur-faces for pitting, burning, alignment, and springpressure. Badly pitted or burned components mustbe replaced.

(b) Examine the fuse unit, and renewable el-ement if the fuse type is used, for corrosion. Checkfor signs of discharge tracking on the fuse. Replacecomponents that show deterioration.

(c) Verify that all attaching parts are in-stalled and tightened to proper torque value.

(d) Check fuse tubes made of fiber or otherorganic material. Refinish the fuse tube as required.Refer to manufacturer’s literature.

(e) Check vented expulsion fuses. Some fusesmay have condensers or mufflers to restrict expul-

sion of gases during operation. A dropout fea-ture that automatically disengages the fuse when itoperates may be used. These fuses usually haveseals to keep moisture out of the interrupting cham-ber. Refer to manufacturer’s literature for instruc-tions.

( f ) Replace fuse holders and clips whichare worn or make poor contact. Remove oxidationand corrosion from fuses, holders and clips. Deter-mine the causes of overheating and correct as re-quired.

i. Synchroscope. A synchroscope, usually in-stalled on a switchgear control panel, is used todetermine the phase difference or degree of syn-chronism of two alternating current quantities ortwo generators. The synchronism always indicatesthe condition of the incoming machine with respectto the bus. If the frequency of the incoming machineis higher than the bus frequency, the synchroscopepoint revolves in the “fast” direction. If the fre-quency of the incoming machine is lower than thebus frequency, the synchroscope pointer revolves inthe “slow” direction. If the pointer stops at a posi-tion other than 0 degrees, it indicates that the in-coming machine is at the same frequency as the busbut out of phase. Correct the phase error by adjust-ing the prime mover governor of the incoming ma-chine for higher speed. The synchroscope pointershould revolve slowly in the “fast” direction. Themachines are paralleled when the pointer reachesthe 0 degree position while traveling in the “fast”direction. When paralleled, the pointer will stay at 0degrees. Refer to manufacturer’s literature for spe-cific operation and inspection information on indi-vidual equipment.

5-22


CHAPTER 6OPERATING PROCEDURES

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6-1. Requirements.A successfully operating auxiliary power generatingsystem has several requirements. First, the equip-ment in the system must be selected with ease ofoperation and maintenance as prime consider-ations. Second, the equipment must be installed bycompetent personnel.

a. Adequate records must be kept during instal-lation and operational shakedown so that any fu-ture modifications can be implemented with mini-mal research. Third, the operating personnel mustbe thoroughly trained in proper operating proce-dures. Training must include performance of main-tenance as well as operation. Fourth, a detailedrecord keeping system must be instituted.

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b. The record keeping system must include a li-brary of the various equipment manufacturers’ in-structions, operating log sheets, routine mainte-nance instructions, maintenance log sheets, andpiping and electrical drawings. The records shouldbe assembled in binders or folders and stored in theinstallation’s engineering office for availability andsafekeeping.

6-2. Attended stations.a. Attended stations have one or more operators

on duty around the clock or for a portion of the dayif the plant is not used full time. Plants that havean operator on duty only for a portion of the daysometimes require an operator’s presence duringthe entire period that the plant is supplying powerto the system. Attended stations can be operated ina manual mode, a semi-automatic mode, or an au-tomatic mode. If the plant is manned at all times,the manual or semi-automatic mode is usually em-ployed. In the manual mode, the operator has com-plete control of the power plant and would start theprime mover, bring it to operating speed, apply ex-citation to the generator, and close the circuitbreaker to pick up the station load. When parallel-ing with another generator, the operator must per-form the paralleling procedures described in para-graph 6-6. If paralleling with the electric utilitysystem is desired, approval must be obtained fromthe utility and the need for special relaying, such asreverse power relays, must be determined. The pro-cedures for parallel utility operation are describedin paragraph 6-5.

‘L--b. In the semi-automatic mode, sensing devices

monitor the normal source of power. Upon a loss of

the normal power source, the sensing devices areactivated and initiate a starting signal to the primemover. An alarm circuit is also initiated at this timeto alert the operator that normal power has beenlost and the emergency unit has started. As theprime mover approaches rated speed, excitation isautomatically applied to the generator. The powerplant will then remain in this condition, i.e., ratedspeed and voltage, until the operator closes the cir-cuit breaker connecting the emergency generator tothe load. If the station has more than one generator,and the load requires more than one generator, theoperator must initiate the synchronizing circuitry.Using the techniques provided in paragraphs 6-5and 6-6, the operator must parallel the second gen-erator with the first. If additional generators arerequired, they must be added to the system in thesame manner. The operator can then adjust thegovernors and excitation controls to obtain the de-sired load division and reactive power division be-tween generators.

c. The automatic mode is similar to the semi-automatic mode up to the point that the unitreaches rated speed and voltage. When the speedand voltage have stabilized, if the unit is picking upa completely dead plant, a closing signal is initiatedto the circuit breaker. The circuit breaker energizesthe desired loads. If the load demands more thanone unit, as the second unit reaches its operatingspeed and voltage, automatic synchronizing cir-cuitry is enabled. The speed of the incoming unitwill be adjusted automatically, and when the syn-chronizing relay is satisfied that the conditions arecorrect, a closing signal to the circuit breaker for thesecond unit will be sent. If additional units areneeded, the automatic synchronizing circuitry willbe switched as the units become available. Oncenormal power is again available, the procedure forreturning the load to the normal bus is usually donein the manual mode. Installations that permit par-alleling with the electric utility system canretransfer without an interruption of power. If par-alleling is not permitted, there will be a momentaryoutage when the switching is performed. Some in-stallations are designed with an automaticretransfer to normal power. However, these are usu-ally the smaller-rated units that use a transferswitch arrangement rather than circuit breakers forswitching loads.

6-1


6-3.. Unattended stations.Unattended stations operate without an operator inattendance. Their operation is the same as an at-tended station used in the automatic mode.

6-4. Nonparalleled stations.a. Nonparalleled stations are those stations that

do not have provisions for connecting the emergencygenerator bus to the commercial bus. It also appliesto a station that has a tie breaker between twoincoming lines that, because of electric utility regu-lations, cannot be connected together. Electrical in-terlocks are used to prevent an unwanted parallel-ing from occurring. These interlocks usually consistof two circuit breakers electrically connected. Thearrangement is such that only one circuit breakercan be in the closed position at a time, thus prevent-ing paralleling.

b. In some arrangements, mechanical interlocksmay also be provided. A mechanical interlock is adevice that physically prevents both circuit break-ers from being closed at the same time. This methodalso prevents paralleling from occurring.

c. Immediately before starting the prime movers,make a thorough inspection to insure that the fol-lowing is in order. Verify that engine generator isnot set to operate in a semi-automatic or automaticstarting mode during prime mover inspections. Ifnot, extreme caution should be used. Unexpectedstart of prime mover while inspecting can lead tosevere injury or death. Check for leaks in the lubri-cating system, the fuel system, and the cooling sys-tem. If any of the auxiliaries are belt-driven, checkfor tightness of the belts. Check for proper levels ofoil, water and fuel. Look for tools or other looseobjects, such as rags, that may have been left in thearea, and remove. If air pressure is a part of thestarting system, make sure the air pressure is atthe correct value. Verify that none of the intake airvents or exhaust ports are blocked. Start auxiliarypumps (lube oil, fuel or water) that are necessaryprior to running the unit.

d. When the preparations for starting have beencompleted, a start signal is given to the primemover. The engine (prime mover) should start torotate and, under control of the governor, accelerateto idling speed. Once the speed has stabilized, readthe pressure and temperature gauges to make surethat normal pressure and temperatures are beingmaintained. Listen to any unusual noises. Shut theengine down if any unusual pressures or tempera-tures are observed, or if unusual noises are heard.Be familiar with the engine manufacturer’s litera-ture for information on acceptable pressures andtemperatures. Once the unit has been placed under

load, readings should be taken according to the op-erating log developed for that station. When theunit is no longer required and the load has beenremoved, operate the engine at no load, or at somepreset idle speed to allow the engine to cool gradu-ally. When the cooling period has expired, shut theengine down. Cooling periods vary for differentprime movers. Refer to manufacturer’s instructions.Stop the auxiliaries that do not stop automatically.Make an inspection of the unit, looking for anyunusual conditions.

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e. It is essential that each power generator havea complete set of standard operating procedures.The procedures include an up-to-date one-line dia-gram of the electrical system showing the genera-tors and the associated switchgear components (seefig 6-l). Notes and legends are usually includedwith the diagram.

AM Ammeter AS Ammeter SwitchVA4 Voltmeter VS Voltmeter SwitchWM Wutt-hour Meter WHDM Wutt-hour Demand MeterCPT Control Power Transformer VAR Volt-Ampere MeterCT Current Transformer PT Potential TransformerG1 ,G2 Generators FU Fuse

f. Before the unit is started an inspection shouldbe made. This can be done in conjunction with theinspection of the prime mover. Look for any mate-rial or loose parts that could be drawn into thegenerator. Make sure that the air flow will not berestricted either on the intake or exhaust.

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g. When the prime mover has the generator atoperating speed, excitation can be applied. Adjustthe voltage regulator until the generator is at ratedvoltage. Adjust the governor control for the primemover so that the generator is at rated frequency.Close the main circuit breaker connecting the gen-erator to the load. If necessary adjust the voltagecontrol for rated voltage and the governor controlfor rated frequency. Readings of various parametersare taken according to the operating log for thatstation. Care must be taken so that the generator isoperated at or below its nameplate rating. After theunit has been shut down, a visual inspection similarto that performed prior to startup can be performed.

h. Proper operation of the switchgear requires aknowledge of the standard operating proceduresand the familiarity with the one-line diagram of theelectrical system. It requires some knowledge of thevarious protective relays and other devices associ-ated with the system. The operator must be able torecognize an impending problem by observing themeters or other indicators. The operator can thentake proper action. The operator must be able toperform some basic troubleshooting and mainte-nance.

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6-5. Paralleled with the electric utility system.a. Stations that can be paralleled with electric

utility systems have the same basic characteristicsas those discussed in paragraph 6-2. They haveadditional features including synchronizing cir-cuitry and, in the case of the unattended station, anautomatic mode.

b. The prime movers in these stations can beoperated in the manual or automatic mode. Opera-tion in the manual mode is discussed in paragraph6-2a . In the automatic mode, relays in theswitchgear will sense the loss of commercial powerand provide a starting signal to the prime mover. Itwill then accelerate under control of the governor tothe operating speed. The remainder of the primemover operation is as previously discussed.

c. This discussion is the same as paragraph 6-4dwith the exception that if the station is in auto-matic, excitation will be applied by the automaticcircuitry. Also, in automatic the main circuitbreaker will close automatically, provided the in-coming line circuit breaker is open.

d. The comments regarding proper switchgearoperation as noted in paragraph 6-4h pertain toparalleling with the utility system. In addition, thistype of system requires paralleling circuitry whichis part of the switchgear. It includes one or moresynchronizing switches, a synchroscope, synchroniz-ing lights, incoming voltmeter, incoming frequencymeter, running voltmeter, and a running frequencymeter. The synchronizing circuitry is energized byturning the synchronizing switch on.

e. The synchroscope indicates the condition of theincoming machine with respect to the bus. If thefrequency of the incoming machine is higher thanthat of the bus, the synchroscope pointer will re-volve in a clockwise or “fast” direction. The operatorshould adjust the governor control of the incomingprime mover until the synchroscope pointer is re-volving slowly in the “fast” direction. The machinesshould be paralleled by closing the breaker of theincoming generator when the pointer reaches 12o’clock. Because there is a slight lag in the breakeror switching mechanism, it is good practice to startthe breaker closing operation at about the 11:30position or slightly before the pointer reaches 12o’clock.

f.: Synchronizing lamps provide a means of check-ing the synchroscope for proper operation. As thepointer revolves, the lamps go alternately brightand dark in unison. Both lamps must be dark as thepointer passes 12 o’clock or the synchroscope is de-fective.

g. Now that the generator is paralleled with theelectric utility system, the load (kW) can be con-trolled by adjusting the governor control. The reac-

6-4

tive load (vars) can be controlled by adjusting thevoltage control. To remove load from the generator,reduce the load by decreasing the governor controlwhile observing the kW meter for the generator.When the kW meter indicates zero, open the gen-erator circuit breaker. The load will now be trans-ferred to the electric utility bus. The prime movercan then be shut down by following normal proce-dures.

6-6. Paralleled with other generating units.a. Stations that have two or more generators that

can be operated in parallel have the same basiccharacteristics as previously discussed in para-graphs 6-2 and 6-3. In addition, they may haveautomatic synchronizing circuitry and also droopcircuits for the voltage regulators. The automaticsynchronizing circuitry includes speed-matching re-lays, voltage-matching relays, and automatic syn-chronizing relays. These relays function when thestation is in the automatic mode and when two ormore AC sources are in agreement within specifiedlimits of phase angle and frequency. The voltageregulator droop circuits are energized when two ormore generators are operated in parallel. Their pur-pose is to prevent the undesirable condition of cir-culating currents between generators.

b. Parallel operation of generators with regula-tors is accomplished by appropriate cross-currentcompensation. The method employs an equalizingreactor or compensator which adds a small voltage,proportional to the reactive current delivered by thegenerator, to the voltage delivered by the potentialtransformers. This gives a slight droop to the volt-age held by the regulator on reactive loads anddivides reactive currents in proportion to load cur-rents. Differential compensation is used when line-droop compensators are installed to automaticallyincrease the voltage as the load increases. With thisconnection, all the equalizing reactors or compensa-tors are connected in series. There is no current flowin the equalizing reactors under balanced load con-ditions. If the load is unbalanced, the currents flowthrough the regulators to decrease the excitation ofthe generator carrying excessive reactive currents.This increases the excitation of the generator carry-ing low reactive current.

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6-7. Operational testing.a. Emergency generator power units must be op-

erated under load conditions periodically to insuretheir reliability. The period for this exercising willvary from station to station. It is important thataccurate logs be kept of the conditions encounteredduring the exercising.

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b. It is suggested that the manufacturer of theauxiliary power unit be consulted to determine thetime intervals in which the auxiliary power unitshould be exercised and the length of each exercise.

,Nationaleration.

and local codes may enter into this consid-

c. The procedures used for exercising the unitswill also vary from station to station. The mostdesirable condition is to use the actual load. How-ever, this is not always possible and in these cases aload bank can be used. A load bank is generally aportable set of resistors that allows a generator tobe tested under load by disconnecting the generatorfrom the actual load and connecting it to the loadbank. In those stations that permit paralleling with

the electric utility system another method is used.After paralleling, the load on the generator can becontrolled by adjusting the governor control.

d. In addition to exercising the units, it is alsodesirable to periodically perform an operationaltest. This test is accomplished by opening the cir-cuit breaker from the electric utility and verify-ing that the necessary relays and contactors ener-gize such that the emergency generator breakercloses and starts the auxiliary power generatingsystem. Performance of the test simulates a loss ofcommercial power. The frequency of this test is de-pendent on the nature of the load, i.e., critical ornon critical, but is usually performed on a monthlybasis.

6-5


CHAPTER 7

ROUTINE MAINTENANCE

7-1. Instructions.a. Manufacturers provide specific instructions for

the use and care of each of their products. Theirinstructions are the result of wide experience ob-tained under varying conditions and should be fol-lowed closely. Maintenance personnel should alwayscheck equipment first for signs of physical damagebefore performing any other checks.

b. Routine maintenance instructions consist ofscheduled inspections of prime movers, generatorsand exciters, and switchgear. When a need for ser-vice or repair is indicated, refer to the manufactur-er’s literature for specific information. Servicerecords of the auxiliary power systems are filed inthe installation’s engineering office.

c. Maintenance information provided in thismanual supplements the manufacturer’s instruc-tions but does not supersede them. Checklists andschedules furnished herein are intended as guidesfor operators and service personnel.

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d. Since auxiliary power systems are operatedintermittently, the usual time frames for routinemaintenance such as weekly, monthly, quarterly,annually may not apply. Accordingly, “short-term” isused for tasks to be performed less frequently. Ex-ceptions are noted in the manufacturer’s manual.

e. Electrical systems acceptance tests are func-tional tests to verify the proper interaction on allsensing, processing, and action electrical devices. Itis critical that these tests be performed on standbygenerator power systems to ascertain the safe andoperational reliability of a system. A system must betested as a united series of devices in addition to thetesting of individual components. For systems thatinclude auto-start, auto-transfer, and/or auto-synchronizing equipment, every six months utilityelectrical power should be removed (open main cir-cuit breaker) from a building, or part of the facilitythat is supplied electrical power by commercialpower/generation combination to ascertain that thesystem will operate under abnormal conditions.

7-2. Prime mover maintenance.Routine maintenance instructions for prime moversconsist of short- and long-term checklists for dieseland gas turbine engines.

a. Short-term (diesels). Short-term checklist for

‘L-- diesel engines.(1) General comments. Before performing any

tasks required by the following checklist, review the

station log sheets, related records, and the manu-facturer’s recommendations.

(2) Checklist.(a) Values. Check valve operation.(b) Fuel injection nozzles. Check fuel injec-

tion nozzles for secure mounting and connectionseach time the engine is shut down. Torque down thenozzles according to the manufacturer’s instruc-tions.

(c) Starting system. Check the general condi-tion of the air compressor, air lines, and valves,when applicable. Briefly pop open the system’ssafety valve weekly. Check for proper operation. Re-fer to manufacturer’s instructions for details.

(d) Governor alarms and instruments. Checkoperation of governor alarms and instruments. Re-fer to manufacturer’s instructions‘

(e) Pressure gauges. Check pressure gaugesand clean exposed indicating elements. Refer tomanufacturer’s instructions.

(f) Intake and exhaust systems. Check air fil-ters and engine exhaust. A smoking exhaust indi-cates incorrect adjustments. Clean air filters as nec-essary.

(g) Exhaust Lines. Clean and inspect exhaustlines. On two-cycle engines, remove carbon fromexhaust ports and clean thermocouples. Refer tomanufacturer’s instructions for frequency of checks.

(h) Evaporative cooling. Refer to manufac-turer’s instructions for cooling tower maintenance.Inspect and oil fanshaft bearings, oil damper bear-ings and linkage. Inspect spray nozzles; clean asnecessary. Clean pump suction screen. Clean sumppan. Inspect cooling coil. If scale has formed, circu-late cleaning solution. Do not operate fan whilecleaning coil. Check belts for condition and propertension. Refer to manufacturer’s instructions.

(i) Fuel oil system. Clean fuel oil strainers asrequired by operating conditions. Check the systemcomponents for clean condition. Refer to manufac-turer’s recommendations.

(j) Fuel filters and centrifuges. Check fuel oilfilters and centrifuges. Check fuel oil system forleaks and correct as required. Refer to manufactur-er’s instructions.

(k) Lubricating systems. Check mechanicallubrication hourly during operation. Oil all handlubrication points, following manufacturer’s in-structions. Correct leaks.

7-1


(l) Sight-feed Lubricators. Clean sight-feedlubricating oil strainers as necessary. Check for ad-equate lubricant supply.

(m) Lubricating oil filters. Check lubricatingoil filters. Clean and replace filter elements as nec-essary.

(n) Piston assembly and connecting rods. Ontwo-cycle engines, remove upper handhole inspec-tion cover from side of engine immediately after theengine is shut down, and inspect the piston forproper lubrication.

(o) Cylinders and cylinder heads. Use com-pressed air to blow out indicator connections. Cleanindicators and install. Refer to manufacturer’s in-structions.

(p) Crankshaft, crankpin and main bearings.Remove crankcase covers immediately after engineis shut down. Check main and crankpin bearings forproper lubrication. Check bearing temperatures forexcessive heat by hand-touch. Refer to manufactur-er’s instructions for frequency of checks.

(q) Gauges and instruments. Verify thatgauges and instruments have up-to-date calibrationcertifications. Read and record all indications ofgauges, thermometers and other instruments atregular intervals as required by the operating log.

(r) Turbocharger. Observe every four hoursduring operation. Check for general condition andsigns of vibration. Evaluate vibration if present.

(s) Turbocharger impeller. Check turbo-charger impeller for accumulated dirt and axialendplay. Dirt may indicate faulty filtering equip-ment. Clean and service according to manufactur-er’s instructions.

b. Long- term (diesels). Long-term checklist fordiesel engines. Performance of checklist tasks isrelated to frequency and extent of use of the auxil-iary power plant.

(1) General comments. The following tasksshould be performed annually, unless otherwisenoted, following performance of short-term checks.

(2) Checklist and schedule.(a) Valve inspection. Inspect exhaust valves;

clean and remove carbon on two-cycle engines andvalves as necessary. Refer to manufacturer’s in-structions.

(b) Inlet valves. . Inspect and regrind inlet andexhaust valves and valve seats as necessary. Referto manufacturer’s instructions.

(c) Valve springs and guides. Check valvespring length and tension and inspect valve stems,bushings, and guides annually or after 2000 hoursof use, whichever comes first. Replace parts as nec-essary. Refer to manufacturer’s instructions.

7-2

(d) Camshaft and drive. Check and adjustgears and/or timing chain. Refer to manufacturer’sinstructions.

(e) Camshaft bearings. Inspect and adjustcamshaft bearing clearances. Refer to manufactur-er’s instructions.

(f) Fuel injection nozzle inspection. After2000 hours of use, remove and check nozzles in thetest stand. Service and adjust nozzles followingmanufacturer’s instruction.

(g) Fuel injection pumps. Inspect fuel injec-tion pumps for secure mounting, cleanliness, andproper operation.

(h) Fuel injection pump inspection. Disas-semble and recondition all injection pump nozzlesafter 2000 hours of use. Repair or replace worn ordamaged parts. Reassemble and adjust, followingthe manufacturer’s instructions.

(i) Air Lines. Drain water from air lines andtank monthly or as necessary. Drain valves are usu-ally located at the lowest point(s) in the air feedsystem.

(j) Air valves. Clean air valves and reseat ifnecessary. Refer to manufacturer’s instructions.

(k) Air compressor. Disassemble and over-haul the air compressor and starting equipmentevery five years based on frequency of use of theauxiliary power plant.

(l) Pressure gauge inspection. Check the dateof calibration. Verify that gauges have valid calibra-tion certification. Calibrate per manufacturer’s in-structions as required.

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(m) Governor overhaul. Overhaul the gover-nor after 2000 hours of use or when needed asindicated. Repair or replace worn or damaged parts.Reassemble and adjust, following the manufactur-er’s instructions.

(n) Muffler (silencer). Keep the muffler andwaste heat equipment, boiler or heat exchangeclean. Accumulations of unburned lubricating oiland soot or carbon are potential fire hazards. Makesure fuel combustion is as efficient as possible. Re-fer to manufacturer’s instructions.

(o) Cooling systems. Inspect piping andvalves for leaks and clean the heat exchanger. Per-form cooling system maintenance, refer to appendixD, herein, and manufacturer’s instructions.

(p) Cooling tower. Drain and clean coolingtower; clean and inspect piping, circulating pumpsand equipment. Refer to appendix D.

(q) Cooling system service. Clean and inspectentire cooling system yearly. Overhaul pumps andrecondition valves and other equipment as neces-sary. Refer to manufacturer’s instructions.


(r) Fuel oil tanks and lines. Drain service crankwebs for crankshaft deflection. Check journaltanks and lines. Remove water and sediment. level and clean oil passages. Replace bearings asCheck heating coil for proper operation. Refer to necessary and adjust running clearance followingappendix B. the manufacturer’s instructions.

(s) Lubricating oil cooler. Clean and inspectlubricating oil cooler for leaks and good condition.Clean outer surfaces more often under dusty oper-ating conditions for more efficient cooling. Refer tomanufacturer’s instructions.

(ad) Turbocharger inspection. Disassemble,clean and inspect entire turbocharger following themanufacturer’s instructions and specifications.

(t) Crankcase. Drain crankcase semi- annu-ally or more frequent based on number of hours runper manufacturer’s recommendations or acceptableindustrial engine maintenance procedures. Inspectlubricating oil pumps; flush crankcase and refill.Refer to manufacturer’s instructions and to theArmy Oil Analysis Program (TB 43-0210) for in-structions.

(ae) General overhaul. Overhaul diesel en-gines and driven equipment every ten years orabout 16,000 hours of auxiliary use. Follow themanufacturer’s recommendations and instructions.Comply with the manufacturer’s specifications.

c. Short-term (gas turbines). Short-term checklistfor gas turbines. Checks are limited to inspectionand cleaning tasks that can be performed on theexterior of an engine.

(u) Lubricating oil pump. Inspect the pumpafter 2000 hours of use for proper operation. Referto manufacturer’s specifications for the pump.

(v) Cylinder heads. Remove cylinder headsaccording to the manufacturer’s instructions after2000 hours of use. Inspect cylinder liners. Cleanand inspect water jackets. Remove scale&and corro-sion as necessary. Inspect and measure diameter ofcylinder liners. Check gaskets for annealing, brittle-ness or cracks. Install new gaskets if necessary.

(1) General Comments. Before performing anytasks required by the following checklist, review thestation log sheets, related records and the manufac-turer’s recommendations.

(w) Piston assembly inspection. On four-cycle engines, pull one piston after 2000 hours ofuse and inspect for proper cooling, lubrication andcarbon deposits. Inspect piston rings and wrist pinand the cylinder liner for compliance with enginemanufacturer’s specifications.

(2) The following precautions must be met.Shut the engine down. Apply “Do not operate” tagsto the operating controls. Open the engine auto-matic start circuit. Deactivate the fire extinguishingsystem. Keep all engine enclosure doors open whileworking on the engine. Allow engine to cool downbefore working on it.

(x) Inspection of pistons. Pull pistons after4000 hours of engine use. Clean and inspect allparts for wear, proper lubrication and cooling.Verify that rings and ring clearances comply withengine manufacturer’s specifications.

(y) Cylinder inspection. Use the barring de-vice (jacking bar) to turn each piston to top deadcenter during step x. Inspect each cylinder liner forscoring. Refer to manufacturer’s instructions.

(z) Anchor bolts. Check anchor bolts forproper torque value.

(3) Checklist.(a) Inlet inspection. Verify that the inlet

drain at lower part of duct is open and free of anyobstruction so that moisture (rain or condensation)can run off. Check inlet temperature sensor forsigns of damage. Clean sensor and surroundingarea with approved solvent to remove dirt and con-taminants. Refer to manufacturer’s instructions.Make sure sensor is securely attached to engine.

(b) Exhaust inspection. Visually inspect en-gine exhaust casing, struts, and center body forcracks, nicks and other signs of damage. Refer tomanufacturer’s instructions. Inspect exhaust stackfor freedom from obstructions and general good con-dition.

(aa) Flywheel bolts. Check flywheel bolts forproper torque value. Refer to manufacturer’s in-structions. Verify alignment and coupling to genera-tor, comply with specifications.

(ab) Main and crankpin bearings. Removebearing caps; check journals and bearings forproper lubrication, wear or scoring. Check mainbearings for proper alignment. Refer to manufactur-er’s instructions.

(ac) Crankshaft. Verify compliance with en-gine manufacturer’s specifications. Examine crank-shaft for cracks. Measure distance between

(c) Chip detectors. Engines usually haveplugs with magnetic chip detectors at lubricationsumps. During normal operation, some fuzz-likeparticles will be found on the detectors. Also, othermaterials (non-metallic sludge and/or flakes, bronzepowder, aluminum chips, etc.) may accumulate onthe plugs. Refer to manufacturer’s literature forspecific information. Check chip detectors for elec-trical continuity while installed. Continuity is anindication of contamination. Remove chip detectorsif contaminated. Discard packing and clean chipdetector. Check chip detector for good thread andproper magnetism. Place new packings on chip de-

7-3


tectors and install on engine. Tighten to propertorque.

(d) External inspection. Inspect enginetubes, hoses, tube/hose fittings, electrical assem-blies and connectors for security, and overheatingand damage due to leakage. Perform inlet and ex-haust inspection as described previously. Checkstandoffs, brackets and struts for looseness, cracks,and damage. Check ignition exciter, igniter plugsand leads for damage, overheating and security.Check mechanical control for signs of excessivewear, damage and security. Check fuel manifold forleaks, signs of damage and security. Check for rustand/or corrosion.

d. Long-term (gas turbines). Long-term checksusually affect interior areas of the engine and areseldom performed in the field. Repairs, if necessary,may involve changes in component balance relation-ships and should be performed at the designatedoverhaul location. Refer to the manufacturer’s lit-erature for information.

7-3. Generators and exciters.Routine maintenance instructions for generatorsand exciters consist of short- and long-term check-lists for rotating and static type equipment.

a. Short- term. Short-term checklists for genera-tors and exciters.

(1) General comments. Before performing anytasks required by the following checklist, review thestation log sheets, related records and the manufac-turer’s recommendations.

(2) Checklist .(a) Air screens or filters. Air screens or filters

should be changed when the air flow is restrictedenough to increase generator operating tempera-ture. Refer to manufacturer’s literature.

(b) Exciter coupling (if applicable). When thegenerator unit is shut down prior to operation, wipeoff excess lubrication from the coupling to preventspatter.

(c) Coupling Leaks and alignment. When thegenerator has been shut down, check for lubricationleaks and tightness of coupling. Note ahy evidenceof improper alignment and correct if necessary.

(d) Axial position. Check axial position of theprime mover, generator and exciter shafts for cor-rect alignment and angularity.

(e) Bearings. Lubrication of generator andexciter bearings is required. Refer to manufactur-er’s literature for instructions for pressure andnonpressure lubricated bearings.

(f) Rotary exciters. Brushes and brush rig-ging. Remove carbon dust from collector ring andcommutator with vacuum and dry with compressed

7-4

air at about 25 psi monthly. Check brushes for wearand indications of arcing and chattering monthly.Check condition of slip rings. Refer to manufactur-er’s instructions.

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(g) Static exciters. Verify that the equipmentis clean and free from dirt and moisture. Verify thatall connections are tight. Check connections for cor-rosion and clean as required.

b. Long-term. Long-term checklists for genera-tors and exciters.

(1) General comments. The following tasksshould be performed annually unless otherwisenoted, following performance of short-term checks.

(2) Checklist and schedule.(a) Coupling Lubrication. Drain lubricant,

disassemble and clean the coupling annually orwhenever necessary. Reassemble, using new gas-kets and fresh lubricant. Refer to manufacturer’sinstructions for flexible coupling.

(b) Brush replacement. When brushes haveworn to half their original length, replace, seatproperly and adjust brush rigging tension from 2.5to 3.6 psi on brush riding surface. Repair and re-place damaged or worn brush rigging parts. Refer tomanufacturer’s instructions.

(c) Brush electrolysis. Electrolytic action canoccur at collector ring surfaces. This action forms agreenish coating (verdigris) on brass, bronze or cop-per. Effects of this action can be reduced or elimi-nated by reversing the polarity annually or as re-quired. Refer to manufacturer’s instructions.

---

(d) Commutator and collector rings. Cleancommutator and collector rings with vacuum. Cleanoil film and dirt with approved solvent. Dry withcompressed air at about 25 psi. Check for rough-ness, hard spots and out-of-round condition. Servicecommutator and collector rings as necessary follow-ing manufacturer’s instructions.

(e) Rotor winding. Rotor maintenance beginswith measuring and recording the insulation resis-tance before the unit is placed in service. Refer tomanufacturer’s literature for instructions. The rotorshould be thoroughly cleaned annually and in-spected as follows: Check the damper winding forloose bars and the connection of each bar to its ringsegment. Check the joints in the ring segments be-tween poles. Refer to manufacturer’s instructions.Check clearance per manufacturer’s specificationsbetween blower and coils. Check the field coils formovement and separation. Clean dirt and oil fromwinding and air passages. Check condition of turn-to-turn insulation on strap field coils. Verify condi-tion of ground insulation on pole pieces. Check allconnections between field coils and lead-out connec-tions to collector rings. Measure and record insula-

- -

_--_

tion resistance between field coils and ground in-cluding the collector rings. Refer to manufacturer’sinstructions. Check bearings and journals for dam-age or excessive wear. Compare micrometer read-ings with the manufacturer’s table of wear limits.Repair or replace mechanical parts to meet thesespecifications. Dry out according to manufacturer’sinstructions. Repair insulation damage and coatwith approved insulating varnish.

(f) Rotor balancing. Measure and record vi-bration limits of repaired unit when it is started.Refer to manufacturer’s specifications for vibrationlimits for the specific unit. Perform static or dy-namic balancing of the unit, according to instruc-tions, if necessary.

(g) Stator winding. Measure and record insu-lation resistance between stator winding andground at the machine terminals annually.

(h) Stator service. Open up the stator annu-ally. Clean thoroughly and inspect for the following:broken, damaged, loose or missing wedges; move-ment or distortion of coil ends; security of all lash-ing and spacers; tightness of coil supports; coolingpassages are open and clean; looseness of coils inslots; cracks or other damage to coil insulation; and,connections between coils and around the frame.Measure and record insulation resistance betweenwinding and ground at the machine terminals.Compare the values with those recorded when themachine was first put in service.

(3) Checkli ts and schedule for solid-state excit-ers. Solid-state equipment does not require long-term checks. If the equipment does not functionproperly, refer to the manufacturer’s literature forinformation. Repair or replace as required.

7-4. Switchgear maintenance.Routine maintenance instructions for switchgearconsist of short- and long-term checklists.Deenergize switchgear before performing mainte-nance. Disconnect primary and secondary sources ofpower.

(e) Circuit breakers. Trip and close circuitbreakers, check for proper operation quarterly.Check time delay and freedom of movement. Referto manufacturer’s instructions.

(f) Coils and heaters. Check coils and heatersquarterly for secure mounting and circuit continu-ity. Check controls and thermostats for proper op-eration, refer to manufacturer’s instructions.

(g) Contactors.. Check magnet surfaces ofcontactors quarterly for cleanliness. Remove gun,rust or corrosion. Adjust for even contact pressureaccording to manufacturer’s instructions.

(h) Voltage regulators. Check voltage regula-tors for proper operation and adjustments quarterly.Various makes and types are used. Refer to themanufacturer’s literature for instructions.

b. Long- term. Long-term checklists for switch-gear. Performance of tasks is related to frequencyand extent of use of the auxiliary power plant.

(1) General comments. The following tasksshould be performed annually unless otherwisenoted, following performance of short-term checks.The procedures are general but apply primarily todraw-out equipment.

(2) Checklist and schedule.

a. Short-term. Short-term checklists for switch-gear.

(1) GeneralZ comments. Before performing anytasks required by the following checklist, review thestation log sheets, related records, manufacturer’srecommendations and NFPA-70E, Electrical SafetyRequirements for Employee Workplaces.

(2) Checklist.(a) Panels and other exterior surfaces. Panels

and exterior surfaces must be kept scrupulouslyclean at all times.

(a) Meters and instruments. Check metersand instruments against a verified standard. Re-turn defective or inaccurate meters and instru-ments to the manufacturer or designated repair lo-cation for service and calibration.

(b) Buses. Inspect ‘buses and connections forsigns of overheating or weakening of insulating sup-ports. Overheating is indicated by discoloration ofthe busbar. Inspect insulators for cracks and/or arctracks. Replace defective insulators. Tighten busbarand terminal connections to the proper torquevalue.

(b) Relays and actuating mechanisms. Clean (c) Indicating devices and interlocks. Checkand inspect relays and actuating mechanisms indicating devices and interlocks for proper opera-monthly. Many types of relays are used. Identify the tion. Refer to manufacturer’s instructions.


relays such as thermal, current overload, overspeed,liquid level, lubricating oil pressure and/or flow, fre-quency change, etc. Refer to manufacturer’s litera-ture for inspection procedures. Verify that all con-nections are tight and free of corrosion.

(c) Conductors and coils. Clean and inspectconductors and coils monthly. Verify that coating ofinsulating varnish is in good condition (clean,smooth and polished) and there are no indications ofoverheating or corona arcing.

(d) Switches. Inspect switches for properalignment, firm contacts and smooth operationmonthly. Burned or pitted copper contact surfacesmay be dressed with 2/O sandpaper. Do not dresssilver contacts.

7-5


(d) Disconnecting devices. Check primarydisconnecting device contacts for signs of overheat-ing or abnormal wear. Clean contacts with silverpolish. Clean disconnecting device contacts and ap-ply light coating of approved lubricant.

(e) Enclosure. Verify that interior anchorbolts and structural bolts are tight. Inspect cableconnections for signs of overheating. Tighten looseconnections as required.

( f ) Circuit breakers. Manually operate eachbreaker while in test position, verify proper opera-tion. Refer to manufacturer’s instructions.

(g) Environmental conditions. More frequentinspections of the switchgear must be made whenunusual service conditions exist, such as contami-nating fumes, excessive moisture, or extreme heator cold. Additional protection may be required ifadverse conditions are present.

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(h) Ground resistance. Measure and recordground resistance values using a ground resistancetest set. Compare these values with those recordedduring previous tests. The tests indicate groundingsystem effectiveness and possible deteriorationsince the last tests.


CHAPTER 8

LUBRICATING OIL PURIFICATIONh-

8-1. Purification systems.Oil purification systems, either in the engine pres-sure system or oil supply system are classified bythe method of flow used’ in purifying the oil. Thesystems frequently used are the bypass and full-flow types as follows:

a. In the bypass system part of the total oil circu-lating in the engine passes through the filter orpurifying equipment. The system continuouslycleans a small portion of the oil and, in general,removes contaminants as fast as they are formed inthe engine. Thus, new oil may deteriorate but willgradually stabilize when the effectiveness of thefiltration system matches the rate of production ofcontaminants.

b. In the full-flow system all of the oil circulatingin the engine passes through filtering equipmentprior to going to the engine.

8-2. Forms of contamination.Refer to appendix C paragraph C-le(2) for informa-tion on complete sample testing. Oil contaminationusually occurs in one of two forms, as follows:

a. Impurities such as dirt, carbon particles orother solid matter entering the oil.

b. Undesirable substances such as water, poly-merized products of oil breakdown, acids and otherchemical matter entering the oil.

8-3. Methods of purifying.Oil purification is accomplished by the use of one, orany combination, of the following methods: strain-ing, filtering, centrifuging, or reclaiming.

a. Straining. The usual type of oil strainer can bewoven wire screen or perforated sheet metal. Edge-type and wire-wound strainers are also used. Theedge-type consists of stacks of metal discs separatedby thin washers. The wire-wound type consists of aspool wrapped with finely serrated wire forming aclearance between adjacent wires. Strainers are de-signed to remove solid particles from the oil, usuallybetween 0.0015 and 0.003 inches in size, dependingon the engine manufacturer’s specifications. Referto the strainer manufacturer’s literature for detailsand servicing instructions.

b. Filtering. Filtering is accomplished usingchemically neutral or chemically activated filteringmaterial.

(1) Chemically neutral. The oil filter usuallyconsists of a canister or tank containing a chemi-

cally neutral, highly absorbent material. Cotton,cellulose waste, or paper is usually used as theabsorbent filtering material. The filter tank is pro-vided with necessary entry and exit ports, internaltubing (perforated and solid), check valves and ori-fices to ensure proper flow of the oil through thefiltering material. Filters are more efficient thanstrainers in removing very small particles and areusually designed to process strained oil. Refer to thefilter manufacturer’s literature for details and ser-vicing instructions.

(2) Chemically actiuated. Absorbent filters con-tain chemically activated material instead of chemi-cally neutral material. Construction of absorbent-type and adsorbent-type filters is similar. Thefiltering materials include charcoal, clay and fuller’searth. These materials remove water, acidic compo-nents, and may absorb certain light petroleum ele-ments, waxes or residual products. They usuallyaccomplish good purification and may reduce acid-ity as well as remove the solid contaminants. Absor-bent or adsorbent filters may be used on straightrun, uncompounded mineral oils where there is nodanger of removing essential additives. Absorbentfilters (chemically-neutral filters) should be used inconjunction with compounded or additive-type oil.Refer to the filter manufacturer’s literature for de-tails and servicing instructions. Ensure that thefiltering system complies with the engine manufac-turer’s recommendations.

c. Centrifuging. An oil purification centrifugeusually consists of a stationary bowl that encloses arotating element. The element, mounted on a verti-cally arranged axis, rotates at a high speed withinthe bowl. High-speed rotation causes a column of oilto form in the portion of the element nearest thecenter and a column of water to balance this at theouter edge of the centrifuge bowl. Solid particleshaving a gravity value heavier than that of the oilare thrown outward, and the heavy solids accumu-late in the centrifuge bowl. Water is removed by thehigh gravity differential produced by the high speedof the centrifuge. Effective mechanical separationoccurs; however, materials in a suspended state arenot always removed by this method. Chemical con-taminants are separated only if they have a mark-edly different specific gravity from that of the oil.Polymerized products having a gravity similar tothat of oil are not separated and, in general, fuel oildilution is not affected or corrected. The centrifugeis used extensively in fuel oil purification but has

8-1


reduced application to diesel and internal combus-tion engine lubricants. If used in an oil reclaimingsystem, it is usually only a part of the total process.Refer to the manufacturer’s literature for detailsand servicing instructions.

d. Reclaimming. Various types of oil reclaimingequipment are used. Most reclaimers operate withthe oil heated at about 4OO”F, which drives off watervapor and lighter fuel oil dilution. Highly effectivereclamation of regular mineral oil is possible. Al-most complete removal of additive material occursduring reclaiming. Oils produced from a reclaimermust be limited to services not requiring an addi-tive oil. Operation at temperatures above 400°F re-sult in partial breakdown of the lubricating oil,which can produce an oil having a higher viscositythan the original oil. Oil reclaimers are normallyused for processing oil between the impure oil andthe clean oil system or may route the reclaimed oilto a separate tank for use in other lubricating ser-vices. Refer to the manufacturer’s literature for de-tails and servicing instructions.

e. Oil quality standards. Oil quality standardsare provided below.

Table 8-1. Oil quality standards.

Normal Maximum

Water and Sediment 1 .oc;/c 5.0%Water 0.5% 3.0%Sediment 0.5% 2.0%

Table 8-I. Oil quality standards-Continued

8-4. Oil maintenance procedures.The following information is a general guide formaintenance of lubricating oil.

a. Water and sediment. Clean by centrifuging.b. Viscosity. Treat with oil reclaimer to drive off

dilution.c. Viscosity. Centrifuge C hot) to remove heavy

sludge. If necessary, add straight run mineral oil oflower viscosity.

d. Corrosion. Treat with activated-type reclaimer.If an additive oil is in use, the presence of corrosivequalities indicates that the additive is exhausted.New oil must be used if the benefit of additives isrequired. Used oil may be reclaimed and used forother services not requiring the additive.

e. Particles. Passage of particles larger than thefilter’s specifications are a definite sign of channel-ing or structural damage to filter elements. Replacefilter cartridges.

8-2


APPENDIX AI REFERENCES--_

Government Publications.AR 420-43

DA PAM 738-750

MIL-STD-188-124

NAVFAC MO-207

TB 750-65 1

TM 5-682

TM 5-683/NAVFACMO-ll6/AFJMAN 32-1083

TM 750-254

40 CFR 761

Facilities Engineering Electrical Services

Functional Users Manual for the Army Maintenance Management Sys-tem (TAMMS)

System Grounding Standards

Operation and Maintenance of Internal Combustion Engines

Use of Antifreeze Solutions, Antifreeze Extender, and Cleaning Com-pounds in Engine Cooling Systems

Facilities Engineering; Electrical Facilities Safety

Facilities Engineering; Electrical Interior Facilities

Cooling Systems-Tactical Vehicles

Toxic Substances Control Act

Nongovernment Publications.American Society for Testing and Materials (ASTM):

1916 Race St., Philadelphia, PA 19103D-877 Dielectric Voltage Tests

D-923 Sampling Insulating Liquids

D-1524 Liquid Color Tests

D-1534 Liquid Acidity TestsNational Fire Protection Association (NFPA):

1 Batterymarch Park, Quincy, MA 02269

NFPA 70 National Electric Code, (1993)

NFPA 70B Recommended Practice for Electrical Equipment Maintenance, ( 1994)

Prescribed FormDD Form 2744 Emergency/Auxiliary Generator Operating Log (Inspection Testing)

‘-,

A-1


APPENDIX B

FUEL AND FUEL STORAGE4-,

B-1. Diesel fuel.Diesel fuel should comply with Federal Specifica-tions W-F-800 MIL-F-16884, or specifications forJP-8. These specifications include grades DF-A,DF-1, DF-2 or types I and II. All are suitable foruse under applicable temperature and service con-ditions. Different grades of fuel should not bemixed.

a. Cleanliness. Fuel must be clean. All dirt, dust,water, sediment, and other contaminants must bekept out of the fuel to prevent damage to engine fuelinjection equipment. The specified grade of cleanfuel must be used to ensure long, economical engineoperation. Handling of fuel must be reduced to aminimum to avoid entry of contaminants. Deliveryof fuel to storage tanks and then pumping it directlyto the day tank through filters is a recommendedprocedure. Filters must be installed in all enginefuel lines and must be cleaned as recommended bythe engine manufacturer.

b. Contamination. Stored fuel and fuel storagesystems must be inspected at regular intervals suchas every 90 days. Samples for detecting fuel con-taminations are as follows:

(1) Inspect fuel filters for indication of microor-ganism growth, rust, scale, or sediment. In a glassjar, collect a sample of diesel fuel from the bottom ofthe tank. Solid contaminants will settle and collectat the bottom of the jar. Clean the filters as directedby manufacturer’s instructions.

(2) Detect water in diesel fuel by collecting in aglass jar a sample of fuel from the bottom of thetank. Fuel and water will separate when the sampleis allowed to settle, water will sink to the bottom ofthe jar. Fuel with water in it may appear white andcloudy when agitated.

.

(3) Detect gasoline or kerosene in diesel fuel bycollecting a sample (refer to b above). Fuel and con-taminants will separate when the sample is allowedto settle, the gasoline or kerosene will float on thefuel.

(4) Detect Oil soluble soaps in diesel fuel byhaving an appropriate laboratory test performed.Avoid this kind of contamination, do not use galva-nized storage tanks or piping.

(5) Prevent condensation within storage tanksby keeping the tanks full. Tanks must be kept fullduring cold weather.

c. Storage. Fuel tanks used for storage must havedrain valves for removal of bottom water (to be done

once every six months). Deterioration of stored fuelis caused by three factors: oxidation, microorganismcontamination and corrosion.

(1) Oxidation occurs directly or through cata-lytic action. Oxygen from the air or fuel combineswith fuel hydrocarbons causing oxidation. Result-ant oxidation continues as long as oxygen ispresent. Metals suspended in the fuel act as cata-lysts. Metals can enter the fuel during refining,distribution or storage. The engine fuel system canthereby be damaged.

(2) Microorganism contamination is caused bybacteria and fungus that exist in the bottom water.Waste by-products of the microorganisms form aself-sustaining corrosive environment. The by-products can form a gelatinous mass which plugsfuel lines and filters, and forms a fuel sludgethereby reducing engine efficiency and possiblydamaging the engine.

(3) Corrosion of the storage tank does not di-rectly deteriorate the fuel. Corrosion can destroy ametal storage tank, usually at the bottom. Metalsthat enter the fuel act chemically to speed up oxida-tion. The combination of microorganism growth andwater causes oxidation.

B-2. Gas turbine fuel.Fuel for gas turbines consists of natural gas or lightdistillate oil such as kerosene or commercial jetengine fuel, Jet A or Jet A-l. All are suitable for useunder applicable temperature and service condi-tions. Most gas turbines can burn fuels used bydiesel engines. Gas and oil fuels should not bemixed.

a. Cleanliness. Fuel must be clean. All dirt, dust,water, sediment, and other contaminants mustbe kept out of fuel to prevent damage to enginecomponents. Only the specified grade of clean fuelshould be used to ensure reliable engine operation.Handling of fuel must be reduced to a minimum toavoid entry of contaminants. Refer to paragraphC-1a for information relating to cleanliness of liq-uid fuel. Natural gas should be passed through sev-eral fine screen filters, to remove solid particles andwater vapor, before it is fed to the gas turbine en-gine.

b. Contamination. Stored fuel and fuel storagesystems must be inspected at regular intervals suchas every 90 days. Examples for detecting fuel con-tamination in distillate (liquid) fuels are given in


paragraph C-lb( 1) through (5). Perform the follow-ing checks when cleaning filters for a natural gassystem.

(1) Inspect the solid particles removed by finescreen filters. Determine if the particles are dust ordirt, or the type of metal if metallic.

(2) Inspect water accumulation for acid or al-kaline content.

c. Storage. Methods and problems for storing dis-tillate (liquid) fuels are described in paragraphC-lc. Information relating to storing natural gasfuel follows:

(1) Natural gas can be stored in low pressuresurface containers or high pressure sub-surface con-tainers and metal bottles.

(2) Liquefied natural gas can be stored in insu-lated metal tanks installed as sub-surface units.

(3) The type of storage employed for naturalgas depends on plant requirements and fuel avail-ability.

B-3. Fuel storage maintenance procedures.a. Provide the base engineer’s office with the re-

ports and results of inspections performed in para-graphs C-lc and C-2c. The base engineer will re-view this data and take appropriate correctiveaction which may include any or all of the following.

(1) Add an an ioxidant to prevent oxidation ort’“aging” of a fuel.

---.

(2) Add a fungicide or biocide to destroy organ-isms present in the water beneath stored fuel.

(3) Add a metal deactivator because metals infuel catalyze or speed up oxidation. Inhibitors thatplace an amine film on metal surfaces are available.Amines are organic compounds that neutralize anelectrical charge in metals.

b. Note that any chemical or additive that isadded to stored fuel must be approved by the Envi-ronmental Protection Agency. Also, the base engi-neer’s office should monitor the removal of bottomwater from storage tanks (refer to para B-1c).

B-2

APPENDIX C

LUBRICATING OIL


C-1. Diesel engine oil.Lubricating oil for diesel engines should complywith Federal Specifications MIL-L-2 104 andMIL-L-9000. Oil that complies with the specifica-tions produces acceptable amounts of carbon resi-due during engine use and has acceptable pour,flash, and fire points. Straight mineral oil is thebasic ingredient. Inhibitors or chemicals are addedto the oil by the oil refiner to ensure compatibilitywith a range of engines operating under varyingconditions. The user must observe recommenda-tions by the engine manufacturer for specific typesand grades of oil for optimum engine performance.

a. Characteristics. Engine lubrication requiresselection of the proper oil. Refer to the engine man-ufacturer instructions. Examples of required oilcharacteristics are as follows:

(1) Oil should have sufficient viscosity to pre-vent metal-to-metal contact. Oils with lower SAEnumbers are lighter and flow more readily than oilswith higher numbers. Heavier oils, those withhigher SAE numbers, may cause sluggish operationand power loss.

(2) Oil should remain stable during use underchanging temperatures and conditions for satisfac-tory service.

(3) Check the engine periodically, such as everysix months, for accumulation of sludge in the enginefilters and strainers and around valve springs. Re-fer to the engine manufacturer’s literature for spe-cific information.

(4) Oil must be free of water and sediment.Collect a sample of oil in a glass jar. Allow thesample to settle. Water and solid contaminantssettle to the bottom of the jar.

b. Additives. Straight mineral oil does not havedetergent qualities. Therefore, various compoundsare added to the oil. These additives keep the en-gine clean by controlling varnish formation or re-sisting chemical changes to reduce oxidation. Otheradditives form a protective film against corrosiveacids.

c. Mixing oils. Different refineries may use differ-ent types of additives or certain characteristics ofthe mineral oil may vary. Mixing types of oil maychange the necessary detergent actions. To obtainmaximum benefit from additive type oils do not mixthem with straight mineral oil. Concentrations ofthe additives is reduced when detergent oils andstraight oils are mixed.

d. Changing oil. Lubricating oil must be changedperiodically. Refer to recommendations by the en-gine manufacturer to specific conditions, time inter-vals, and instructions. General oil change proce-dures are as follows:

(1) Operate the engine before draining old oil.Oil should be drained while warm and immediatelyafter engine shut down because contaminants are insuspension and will drain readily.

(2) Obtain a sample of the drained oil and de-liver it to the base engineer for testing. Drained oilshould be examined for fuel dilution, acidity, andpresence of solids and other contaminants. Testinghelps establish the overall condition of the engineand approximate frequency of need for oil changes.

(3) Observe the viscosity of drained oil. In die-sel engines oil viscosity increases during service dueto the gradual oxidation of the oil. Viscosity de-creases if fuel gets into the oil by passing the pistonrings or through leaks.

e. Oil analysis program.(1) Personnel in the engineer’s office, and other

cognizant personnel, should refer to the Army OilAnalysis Program (AOAP) for sampling and analy-sis information. The program is described inTB 43-0210.

(2) The ana ysis1 of periodic samples of the lu-bricating oil should report the character andamount of contaminants, wear metals and additivesin the oil. However, some amounts of wear metalsand contaminants will have been collected by thechip collectors, strainers, filters, separators of thesystem and also as sludge. To secure the total pic-ture it is necessary to analyze all such collectedmater ia l to determine the to ta l rate o fincrease/decrease of each. This will indicate whathas occurred during the period between samples.

(3) The prudent responsible operator will logand use all such data to track trends that givewarning of conditions that may result, if uncor-rected, in major problems.

C-2. Gas turbine oil.Lubricating oil for gas turbines should comply withFederal Specifications MIL-L-23699 or MIL-L-7808. Oil that complies with the specification canwithstand the high temperatures encountered dur-ing engine operation.

a. Additives. Various compounds are added tomineral oil to provide the special characteristicsrequired for use in gas turbines. The user must

C-1


observe lubricating oil recommendations by the en-gine manufacturer for optimum engine perfor-mance.

b. Changing oil Refer to the engine manufactur-er’s literature for recommendations related to spe-cific conditions, time intervals, and instructions forchanging the lubricating oil.

(1) Collect a sample of old oil when oil isdrained from the engine storage tank. Examine thedrain plug or valve, filter, and chip detector if used,for metal particles. Save the particles for analysis.

(2) Deliver the drain oil sample and particles tothe base engineer for tests and analysis. The pres-ence of some particles in the drain oil is usuallyconsidered normal by the engine manufacturer.

(3) Refer to the manufacturer’s literature. Anoil analysis program is usually recommended, in-cluding a spectrometric analysis of the metal par-ticles. It is necessary to collect and evaluate data fortype and quantity of engine wear-metals. Study ofthis data shows trends of engine wear and expectedfuture reliability.

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APPENDIX D

COOLING SYSTEMS AND COOLANTS

D-1. Coolant.The coolant used in diesel engines usually consistsof a mixture of ethylene glycol antifreeze, corrosioninhibitor, and fresh water. When the engine is usedin an extremely cold area, such as Arctic regions, aspecial antifreeze mixture is used. Specifications re-lated to the mixtures are as follows:

Antifreeze, Ethylene glycol MIL-A-46 153Antifreeze, Arctic- type MIL-A-11755Inhibitor, Corrosion O-1-490The specification for cooling system cleaning compound isMIL-C-10597.

D-2. Engine water treatment.The prime consideration in a closed water coolingsystem is proper water treatment to ensure no cor-rosion or scale occurs during static or dynamic en-gine conditions.

a. Acceptable conditions. In most modern dieselengines the following cooling water conditions areacceptable:

(1) pH 8.5 to 10(2) Chloride and Sulfate 100 ppm(3) Total Dissolved Solids 500 ppm(4) Total Hardness 200 ppm

b. Softened water. If possible softened watershould be utilized to reduce the total hardness levelof the engine cooling loop. The use of softened waterwill increase engine performance by reducing theprecipitation of calcium and magnesium at elevatedtemperature conditions, ensuring higher heattransfer rates.

c. Antifreeze. Typically, engine cooling systems in-corporate antifreeze solutions which inhibit scaleand protect the cooling system when temperaturesare encountered below freezing. Ethylene glycolmixed with a corrosion inhibitor such as triazolesform an inhibiting film on metal surfaces that actsas a barrier in the corrosion process. The followingconcentration curves should be utilized when add-ing glycol solutions to engine cooling system.

d. Concentration. As indicated by the chart theconcentration should exceed 30 percent. If morethan 60 percent of solution is added two effects willbe realized; first a decrease in heat transfer rates,second a lowering of the system freeze protection.

D-3. Cooling system maintenance.Maintenance consists of periodically testing the an-tifreeze, inspecting the coolant for cleanliness, and

flushing or cleaning the system with compoundwhen necessary. Engines used in Arctic regions arecovered in paragraph D-4.

a. Testing antifreeze. Perform tests to verifyfreeze protection and reserve alkalinity.

(1) Test for freeze protection using the combi-nation antifreeze and battery tester, stock number6630-00-105-1418. Instructions for using thetester are included with it.

(2) Test for reserve alkalinity (corrosion protec-tion) using the reserve alkalinity test kit, stocknumber 6630-00-169-1506.

(3) Cooling systems with freeze protection be-low - 7 degrees F ( -22 degrees C) that fail thereserve alkalinity test may be replenished with cor-rosion inhibitor, stock number 6850-00-753-4967.Replenishment is a one-time service. If the reservealkalinity test is failed again, replace the coolant. Ifthe system passes the test, record the date.

b. Inspecting coolant.(1) Inspect the coolant visually for cleanliness.

Obtain a coolant sample and place it in a clean glasscontainer. After allowing about five minutes for set-tling, examine the sample for contamination (rust,foreign particles, and/or sediment). The sample mayhave some color (same color as original antifreeze)and should be clear.

(2) Examine the sample to determine the typeand quantity of contamination. Rust, a chemicalcombination of iron, water, and air, is frequentlyfound. The presence of rubber particles usually in-dicates deterioration of hoses. Replacement hosesmay be indicated. Sediment may be caused by im-purities in the water used in the coolant. Contami-nants in the coolant can clog a radiator or heatexchanger and cause engine and generating systembreakdown.

c. Cleaning the system. Clean the cooling systemwhenever the coolant is drained. Usually the sys-tem requires nothing more than thorough flushingout with fresh water. Refer to the engine manufac-turer’s literature for instructions. If any part of thesystem is rusted or partially clogged, it is necessaryto use cooling system cleaning compound and condi-tioner, stock number 6850-00-598-7328. Do not usethe compound as a routine maintenance procedure.Instructions for using the compound are includedwith it.


D-4. Filling the cooling system.Refer to the engine manufacturer’s literature forinstructions on filling the cooling system. This isapplicable to either new systems or those justcleaned and serviced.

a. Cooling system protection is required for allliquid cooled diesel engines. In areas where tem-peratures no lower than -55 degrees F ( -48 de-grees C) are expected, prepare a solution accordingto the table D-l below. When temperatures belowfreezing are not expected, use a weak solution suchas one pint of ethylene glycol antifreeze for eachgallon of solution for general protection against rustbuild up and scale formation with the engine.

b. Use arctic-type antifreeze in areas where tem-peratures below -55 degrees F ( --48 degrees C) areexpected.

D-2

c. Do not dilute arctic-type antifreeze with wateror inhibitor. It is ready for use as issued.

Table D-l. Antifreeze solutions.

GUIDE FOR PREPARATION OF ETHYLENEGLYCOL ANTIFREEZE SOLUTIONS

Lowest Estimated Pints of Antifreeze Needed toTemperature in Area Prepare I -Gallon of Solution

+2O”F (-7°C) I .so+IO”F (- 12°C) 2.000°F (- 18°C) 2.75- 10°F (-23°C) 3.25- 20°F ( - 29°C) 3.50-30°F (-34°C) 4.00- 40°F ( - 40°C) 4.25- 50°F ( - 46°C) 4.50- 55°F ( - 48°C) 4.75


APPENDIX E

SAFETY

E-1. General.The base engineer and his representatives are re-sponsible for general safety conditions, for enforce-ment of safety rules, and for the condition and useof all protective devices. The base engineer is re-sponsible for the competency of his representatives.

E-2. Safe operation.Safe operational practices must be followed to pre-vent injury to personnel and damage to equipment.These practices are applicable to diesel engines, gasturbines, and generators including associated elec-trical equipment. Protective devices include carbondioxide fire extinguishers and first aid kits. When-ever carbon dioxide extinguishers are used, enterthe area where used cautiously. Make sure the areahas been ventilated thoroughly before entering.Never use water to extinguish a fire in the engine,generator, or associated electrical equipment.

a. Diesel engines. The engine operator must per-form the following visual checks before and duringoperation.

(1) Make sure engine coolant is at the properlevel and has the proper amount of antifreeze.Check hoses for good condition.

(2) Make sure engine air requirements for com-bustion are met. Check air filters and cleaners forcleanliness and good condition.

(3) Make sure the engine, generator, and re-lated equipment are clean. Keep oil-soaked rags outof the generating facility to avoid a fire hazard.

(4) Guard against accidental or unintentionalstarting when work is being done on the engine orassociated equipment. Attach an approved safetyclearance tag such as DA Form 4324 to the startingcontrol when work is being done.

(5) Make sure engine lubricant and fuel are atthe proper levels.

b. Gas turbines. The engine operator must bealert for the presence of health and fire hazards.Make sure the generating facility is well ventilatedwhen using cleaning solvents. The following re-quirements must be met when the engine room isentered.

(1) The gas turbine shall be shut down or lim-ited to idle power.

(2) The enclosure door shall be kept open. Ifthe gas turbine is operating, station an observer atthe enclosure door.

(3) Do not touch any part of an operating en-gine, as the engine becomes extremely hot. Wearinsulated gloves as necessary.

(4) Wear approved ear protection if the engineis operating.

(5) Do not remain in the room or enclosure, orin the plane of rotation, when starting or monitor-ing the engine.

(6) Attach an approved safety clearance tagsuch as DA Form 4324 to the starting control whenwork is being done.

(7) Make sure the engine, generator, and re-lated equipment are clean. Keep oil-soaked rags outof the generating facility to avoid a fire hazard.

c. Generators. Personnel must be familiar withrecommendations and procedures described in TM5-682.

E-3. Electrical safety.a. General. All operating must be familiar with

the following general safety precautions.(1) Do not rely on safety devices. Never assume

power is off or disconnected. Use and/or look for asafety clearance tag before working on high voltageequipment.

(2) Use rubber gloves, with valid “usefulness”certification, when working on equipment or trans-mission lines.

(3) Stand on good rubber mat when working ongenerator equipment or switchgear.

(4) Have a person qualified in first aid for elec-trical shock present at all times when working.

b. Rescue of shock victims. (1) Protect yourself with dry insulating mate-

rial.(2) Open the circuit, wear rubber gloves to pull

the victim away from the live conductor. Do nottouch the victim with bare hands until the circuit isopen.

c. First aid. Look for hemorrhage, stoppage ofbreathing, wounds, fractures, etc. Indications ofshock include: pale face, clammy and sweaty condi-tions, weakness, and a weak and rapid pulse. Do thefollowing in any emergency.

(1) Send for a doctor or carry the victim to adoctor.

(2) Make sure the victim is comfortable. Keepthe victim warm, quiet, and flat on the back.

(3) Loosen the victim’s clothing. If breathinghas stopped, apply artificial resuscitation. Studythe procedures in TM 5-682, Section VIII. Do not

E-1


wait until an emergency requiring aid occurs, knowwhat to do.

(4) Treat serious bleeding and stoppage ofin that order before anything else is done.

artificial resuscitation. Continue until the doctor

(5) Feel for the patient’s pulse. Failure to find apulse does not indicate death. Immediately begin

arrives..-


APPENDIX F

RECORDS

F-1. Manufacturer’s forms.Manufacturers provide specific instructions for theuse and care of their products. Very often theseinstructions include forms and log sheets for recordkeeping on an hourly or daily basis for continuouslyoperating engines and generators.

F-2. DD Form 2744 (Emergency/AuxiliaryGenerator Operation log).Use DD Form 2744 for inspection testing ofemergency/auxiliary generators. Enter readings im-mediately after start and prior to shut-down. If theengine runs more than one hour, record every twohours with a minimum of two readings. Use theform to record system performance during inspec-tion and testing. Record information such as operat-ing data, condition of lube oil (viscosity test), condi-tion of plant and subsystems, deficiencies and

corrective measures. This data helps determine theneed for further maintenance. Supervisors can de-velop a local checklist and use it for inspections notrequiring generator operations. Complete a DDForm 2744 for each scheduled emergency or auxil-iary generator exercise. When possible, fill out theforms during unscheduled power outages. Duringextended generator operations, check generators asfrequently as manpower and scheduling permit.Only one form is necessary for each event. Annotateeach check on the back of the form, to assist introubleshooting if a problem arises between checks.The workcenter should keep completed forms forquick reference. If desired, place a second copy onthe unit in a protective cover. The supervisor re-sponsible for maintaining emergency/auxiliary gen-erators and associated equipment must review com-pleted forms periodically.

F-1


EMERGENCY/AUXILIARY GENERATOR OPERATING LOG (INSPECTION TESTING)

1 m ENGINE DATA

a. MAKE

(y@ii-p?<_;? ({4 &<c. SERIAL NUMBER

\Q‘S &fl/

c. HOUR METER(7C_i;L:‘L

f. INSPECTION TEST OPERATOR

c jclr ~~~:'~\fQq~h. BASE/POST

LtX mbk2. ALTERNATOR DATA

a. M A K E K&i-l?

6. VOLTAGE REGULATOR (See Note 7)

b. MODEL U N REMARKS_. .:;:... ~::::. :::::. ::. :: .:_ ‘. :::: ‘_‘.~.~_~.~_~.‘.~_~.~,~.~.~.~.~.~.~.~.~‘-Q . ;i ‘i- i_.!‘/ a. REGULATOR

d. RPM MOUNTS L/

1 6 il i;, b. RHEOSTAT CONDITIONlCorroded,connections,

(11 START (2) FINISH etc.\/

3c:‘) -

. ‘._L 20,~ y 7. AUTOMATIC TRANSFER PANEL (See Note 7). . . . . . . . . . .

g. D TE

pl

,.;,.,._.,._..._.;,. ._._.,., :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.: :.:.:....‘.‘.‘.‘.~_~.‘.~.‘.~.~ ._. ,~,~.~.~.~_~.~.~.~,~.~.~.~.~.~.~.~,~.~,~,~.~.~.~.~.,............‘.‘.‘.‘.‘.~.~.‘. :: .~_~,~_~.~.~.~.~_~.~.~.~.~,~.~.~.~.~.~ ~:::::: ‘.~_~,~_~.~_~_~_‘_‘.~.~.~.:.:.:.:.:.:.:.,. :.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.~:.:.:.:.: :.:.:.:.:.:.:.:.:.:.:.:.::.:.:.:.:.: S U N REMARKS

'g- 15 q.qa. CONTACTS BURNED

i. UNIT , L/

5-s -- ii I'Yb. MECHANISM BINDING .J

b. MODEL

2a‘r C! c. WIRING DAMAGED!J

c. SERIAL NUMBER d. KW RATING d. COMPONENTS

‘sy ! y’ Lb,’ OVERHEATEDi/

t. VOLTS ., ~

4%f. PHASE

Qt

8. COOLING SYSTEM (See Note 2 )

L -’ 1a. TEMP. DURING STANDBY b. TEMP. DURING OPERATIONS

g. SHOP SUPERVISOR h. DATE;

5 /yl p&7

1 I’-, 5 y_ 1 ‘3 (:I @= 6

-xb’& 14J?\\( &J c. COOLANT ADDED lLeve/J d. ANTIFREEZE PROTECTION (See

i. LOCATION lBuildingJY

.3, - ib

j. RECORD IDENT NUMBER

3 cc :: % l,i‘ !t ‘-;)7 -cl *uL Note 33 - - 5 ’ F

i2, e. FAN BELT CONDITION f. RADIATOR AND LOUVER CON-

3. GENERAL CONDITIONS /See Note 7) c? ‘6 DITION (?c

REMARKS 9. LUBE OIL SYSTEM

Jca. OIL CHANGED (Xl b. OIL ADDED (Sum /eve/J

a. CLEANLINESS , \YES NO YES NO

b. EXHAUST / d. LEVEL IN GOVERNOR

CONDITION v’

c. LUBE OIL CONDITION lViscosityJ

c; p.+_

c. ENGINE VIBRATION

d. LOOSE ITEMSfBolts, Linkage, etc. J

L/ITEM (See Note 2J ALTERNATOR EXCITER

I10. KW LOAD . .

T,ij.i ,+I: l-7 \ ,-;3 >(I

t/ i-4 p;,c PHl PH2 PH3

1 1 . A M P E R A G E

c. TURBO VIBRATION /‘t

f. WATER LEAKS (XI g. LOCATION OF LEAK

YES NO A’r ” i<,Il i-1 It, /(T{ ?Lt crpj iq

4. FUEL SYSTEM (See Note 7)

& +q c(Q

PHl PH2 PH312. VOLTAGE

$(? .&I 4 &!.

13. BRUSHES ANDBRUSHES RIGGING i

S U N REMARKS 14. SLIP RINGa. FUEL LEVEL (Day Tank) CONDITION

15. COMMUTATORb. FUEL LEVEL [Storage CONDITION

Tank) 16. VOLTAGE PHl PH2 PH3

c. WATER DRAINED (XJ d. FUEL LEAKS (XJ (Commerciall da;. r)$(! i\ei,

YES NO YES lx1.>

NO 17. BATTERY CHARGER

c. LOCATION OF LEAK b. AMPS I

I L5I

5. BATTERY BANK (See Note 7) 18. HYDROMETER 19. STARTING AIR 20. AMBIENT

U N REMARKS, READING lPsiJ TEMP. ioF/

II. CONNECTIONSJ

L<i_' 3 i-" '7+jH

<cl jqk3::r i Ctlj 21. FILTER CHANGE

b. CLEANLINESSJ

$i\ )‘nv\‘y’ nE:fi;:j&i 5 ~ (1. L U B E O I L fXJ b. FUEL fXJ c. AIR INTAKE /XI

f &?‘d iz c’_&)._i Ea >:I Y E S NO XI YES 1 1 NO 1 YES NO

c. ELECTROLYTE LEVEL22. UNIT STARTED ON (XJ

.1ST TRY 2ND TRY 3RD TRY NOT AT ALL

F-2

Use the reverse side of this form and/or 8-l /2 x 11” paper if required for additional comments, continuation of item entries (identify by itemnumber), and for corrective action(s) taken.NOTE 1: Mark S for Satisfactory, U for Unsatisfactory, N for Normal, or indicate in Remarks column, as applicable.NOTE 2: Enter data as indicated. Where no instrumentation is provided, indicate Satisfactory, Unsatisfactory, etc., as applicable.NOTE 3: Enter Antifreeze Protection as the freeze temperature in degrees (F) as indicated on an appropriate hydrometer.

DD FORM 2744, MAY 96 LOCAL REPRODUCTION AUTHORIZED.

Figure F-1. Sample DD Form 2744 (Emergency /Auxiliary Generator Operating Log

c

TM 5-685/NAVFAC MO-912c

Figure F-1. Sample DD Form 2744 (Emergency/Auxiliary Generator Operating Log (page 2)


APPENDIX G

DIESEL ENGINES: OPERATION, TIMING, AND TUNING INSTRUCTIONS

G-1. Starting and stopping.a. General. Starting and stopping procedures ap-

ply to diesel engines that are not equipped with anautomatic start and shutdown feature such as themanually operated engine used in a Class B system.The procedures may be used if an engine is to beexercised. Instructions for the operator, includingoperation and recording of instrument data, areprovided.

b. Starting. Before starting make sure engine an-cillary equipment is ready to function. The majorportion of normal wear occurs while starting a coldengine or an engine which has been idle. Properstarting technique includes inspection to verify thatthe engine and its accessory plant are ready foroperation, adequate fuel is available, and lubricat-ing oil, coolant and other supplies are at properlevels. Starting involves proper positioning of theengine, use of the starting system and proper accel-eration to operating speed. Starting also includesapplication of the load to the engine.

c. Operation. After engine operation starts andthe load is applied, operator duties include followingthe load variations and making necessary opera-tional adjustments. The operator must continuouslyobserve operation to determine deviations from nor-mal or acceptable including ranges of operatingpressures, temperatures or other operational pa-rameters. Unusual sounds, smells, vibrations of os-cillations of the engine and major variations in in-strument readings, may indicate some abnormalcondition.

d. Recording. Instrument readings and operatorobservations must be recorded for analysis. Thesedata may indicate trends toward deterioration orneed for adjustment. Entries on engine and relatedlogs must be at regular intervals and accurate.

e. Operational maintenance. The operator shouldbe alert to possible malfunctions or deviations dur-ing operation. Operational adjustments such aspressure and temperature should be noted and re-corded, if unusual. Ancillary equipment must beinspected during engine operation.

f. Stopping. Proper technique in stopping the en-gine and shutting down the ancillary equipment isnecessary. Correct shutdown permits the engine tocool without excessive distortion of parts or stressesbeing imposed. The engine will be ready for restart

and subsequent use when needed. An engine can bedamaged by improper shutdown or starting prac-tices.

G-2. Engine timing.a. Timing function. The fuel injection system

must be timed so that combustion starts at, or justbefore, piston top dead center (TDC).

(1) Early ignition produces excessively highcylinder pressures and detonation from the rapidpressure rise. Late ignition occurs when the pistonis moving away from the cylinder head, conse-quently the expansion ratio is reduced and effi-ciency is lost. Another timing function is the rate ofinjection, or the duration of the injection period.

(2) Injection continues over a measurable pe-riod of time, usually expressed in degrees of crank-shaft rotation. It is desirable to inject the fuel asquickly as possible without creating high cylinderpressures. The fuel burning period should be com-pleted within the 15-20 degrees of crankshaft rota-tion after top dead center.

(3) The time of start of injection is determinedby ignition delay, since initial combustion must besecured by top dead center, or slightly before. Dura-tion of the injection period is determined by theallowable rate of pressure rise in the cylinder. Ifignition delay is assumed to be .0025 second, thefollowing applies to high, medium and low speedengines operating at 1,800,600 and 300 rpm respec-tively.

Table G-1. Ignition delay and duration.- -

Description

Engine RPMRcvolutions/secondDegrees/secondIgnition delay. degreesProbable duration, degrees

ENGINE SPEEDHigh Medium Low

I .800 600 _wo30 I 0 5

10,800 3,600 I ,?wo27 9 4.530 20 IS

(4) Note that the high-speed engine would re-quire an injection start timing 27 to 30 degreesbefore top dead center, and that all fuel is in thecylinder by 3 degrees after top dead center. Pressurerise is rapid once ignition starts, because nearly allof the fuel is in the cylinder. As speed is reduced, alater start of injection is possible. For the medium-speed engine, about half of the total fuel charge is inthe cylinder when ignition occurs, but the balance ofthe charge is injected into the burning portion.

G-1


(5) For the 1ow-speed engine, about one-third ofthe fuel charge is present, while two-thirds of thecharge is injected at a controlled rate after ignitionoccurs. In practice, the lower speed engines use alower octane fuel. Since such engines are usuallylarge, a relatively coarse atomization is used, re-sulting in greater ignition delay. In low-speed en-gines, actual fuel timing is usually in the rangefrom 7 to 12 degrees before top dead center.

(6) The med’ium-speedd engines usually aretimed from 10 to 18 degrees before top dead centerwhile high-speed units will range as much as 35 to40 degrees before top dead center. Generally, theduration of injection decreases with speed.

b. Timing procedure. Timing is established bysetting the fuel injection cam with the control sys-tem in the maximum fuel position. Since the fuelcam is usually symmetrical, lost motion affects theopening and closing times equally. For example, ifan engine were timed at full load for opening 10degrees before top dead center and closing 10 de-grees after top dead center, at half load, the timingmight be 6 degrees before top dead center to 6 de-grees after top dead center. By lowering fuel pres-sure, the injection period can be lengthened to ap-proach the full load values. Balance is secured byadjusting the lost motion device for each of the cyl-inders. It is important to maintain all fuel nozzletips in good condition, and to have carefullymatched orifices on the nozzle. The nozzle orificeand duration of injection are the only balancingadjustments. Since duration should be similar forall cylinders, matched orifices must be used. Alwaysinstall new fuel nozzle orifices in full sets for acommon rail engine.

G-3. Engine tuning.a. General Tuning of diesel engines is necessary

whenever the engine is not running normally, haslost power, or has operated the number of hoursthat constitute a tune-up interval.

b. Tune-up categories. There are two categories oftune-up, minor and major. Refer to the time intervalspecified by the manufacturer for minor and majortune-ups. The specific manufacturer’s literatureshould be consulted for tune up details related tothe engine in use.

(1) Minor tune-up includes the following:(a) Retorque cylinder head. This is optional;

follow manufacturer’s instructions.(b) Adjust tappet clearance.(c) Adjust injector timing or setting on en-

gine using unit injectors.(d) Check pump static timing on engines us-

ing a pump-nozzle combination.(e) Change fuel filters and strainers.

G-2

( f ) Check air filter. Change air filter oil if oilbath type.

(g) Check high idle speed.(h) Check low idle speed(i) Check engine for correct horsepower. Use

dynamometer.

1

(j) Visually check engine for leaks.(k) In addition to these items, some engines

may require additional adjustment or checking be-fore the tune-up is complete.

(2) Major tune-up includes the following:(a) Retorque cylinder head.(b) Adjust tappet clearance.(c) Clean and adjust injectors and/or injec-

tion nozzles.(d) Check pump static timing.(e) Change fuel filters and strainers. Drain

engine coolant.(f) Service air cleaner.(g) Check and overhaul injection pump if

needed.(h) Check high idle speed.(i) Check low idle speed.(j) Check engine for correct horsepower. Use

dynamometer(k) Visually check engine for leaks.

(3) During the tune-up, check for any loosebolts or hose clamps that may be a potential troublespot. Also, replace all gaskets, such as tappet covergaskets, pump gaskets, timing cover gaskets, andany other gaskets that have been disturbed duringthe tune-up.

_-

G-4. Engine failure and repairs.a. Failure identification. A well planned and ex-

ecuted preventive maintenance program reducesthe possibilities of experiencing a catastrophic en-gine failure. However, it is not completely possibleto prevent or anticipate such a failure. Indication ofsome of these failures are as follows:

(1) Crankcase explosions. If, during operation,explosions can be heard in the crankcase, shut theengine down immediately. Allow the engine to coolbefore removing any cover plates for inspection.

(2) Runaway engine. May be caused by a stuckfuel pump rack or defective engine safety stop. Lu-bricate the control linkage when the engine is atrest or shut off the fuel supply to the engine, asnecessary.

(3) Sudden stop. May be caused by overload,low lubricating oil, seized engine components, orempty fuel tank. Inspect to identify the problem.Allow the engine to cool before removing any coverplates.

(4) Unusual noises. Can be caused by fuel in-jection equipment troubles, a loose or broken con-

-+*


necting rod, faulty piston rings or wrist pins, or aloose flywheel. Inspect to identify the problem.

b. Repairs. Repairs must be prompt and thoroughL to restore the engine to serviceable condition as

rapidly as possible. Such repairs normally dependon the immediate repair parts inventory but may

* also require maximum ingenuity in producing auseable repair part. Particular attention mustbe given to not only the part which failed, butalso to all other parts which might be affectedby the failure. Merely replacing an obviously de-fective part often will lead to a series of diffi-

culties originating from by-products or effects ofthe initial failure. Therefore, carefully check allof the related and resultant functions of the faultypart or any other component affected by it to makesure that the engine has been thoroughly restoredto operable condition. For example, if a connect-ing rod bearing fails, replace the bearing and exam-ine the crank journal to see if it has been scoredor damaged and if all oil passages to the pistonare properly clear. Also, verify that connecting rodbolts or adjacent main bearings have not been af-fected.

G-3


Section IAbbreviations

A, AMPamperes

ACalternating current

ASammeter switch

kvkilo volts

kwkilo watts

LPTlow pressure turbine

BDCbottom dead center

CCentigrade

CFMcubic feet per minute

CFRCode of Federal Regulation

Clcompression ignition

CPTcontrol power transformer

L CTcurrent transformer

DCdirect current

EMFelectromotive force

FFahrenheit

FUfuse

HPhorsepower

HPThigh pressure turbine

Hzhertz

IR VARinfrared volt amperes reactance

kVAR, kilovarsI!I kilo volt amperes reactance

--I kVAI

kilo volt amperes

NEMANational Electrical Manufacturers Association

NFPANational Fire Protection Association

PCBpolychlorinated biphenyls

PHpouvior hydrogene

PPMparts per million

psipounds per square inch

PTpotential transformer

RFIradio frequency interference

RPMrevolutions per minute

RTDresistance temperature detector

SIspark ignition

TDCtop dead center

UPSuninterruptible power supply

Vvolt

VMvoltmeter

VOMvolt ohm milliammeter

Glossary 1


vs WHDMI voltmeter switch watt-hour demand meter

W WMwatt

Section IITerms

Alternating currentAn electric current that is continually varying invalue and reversing its direction of flow at regularintervals. A cycle is one complete set of positive andnegative values of an alternating current. The num-ber of cycles occurring in one second (cycles persecond or Hertz) is called frequency. Alternatingcurrent voltage is expressed as volts AC.

Brayton cycleThe operating principle by which a gas turbine en-gine operates, called constant pressure combustion.

Charge (circuit breaker)The loading or tensioning of circuit breaker springsby compression and/or extension.

Circuit breakerA device for closing and/or interrupting a circuitwithout damage to itself or the equipment it is pro-tecting when properly applied within its rating. Theinterruption feature of this device functions whenan abnormal condition such as an overload or shortcircuit occurs. The device usually is set to trip at125 percent of full load current.

Dew pointDew point is the temperature at which dew starts toform (vapor condenses into liquid).

Direct currentAn electric current that flows continually in onedirection. Direct current voltage is expressed asvolts DC.

Electromotive forceThe potential, or voltage, developed by a dynamo orbattery.

Emergency powerA power source (held in reserve) that is available foruse in the event of failure of the normal powersource. Transfer to and/or from emergency powercan be automatic or manual.

Fault currentCurrent flowing to a fault. It may be leakage, ashort circuit, or a direct ground.

Four cycle (four stroke) engineA reciprocating (piston) engine, using gasoline ordiesel oil for fuel. The engine produces one power

Glossary 2

every four strokes of thepass through the cylinder.

impulse per cylinder forpiston. One stroke is one

Fuel filterDevice used to separate solids, impurities, and wa-ter from the fuel.

Gear pumpDelivers fuel from tank to injectors.

GovernorA mechanism used to control the speed of an engine.

Governor characteristicsTerms used in discussion of a governor:

a. Governor sensitivity. Ability to detect a changein engine speed, expressed as percent of rated topspeed.

b. Governor speed droop. Change in engine speedas load increases, expressed as percent of ratedspeed.

c. Governor reset. Adjustment to the governor (in-ternal or external) which changes the set speed atany given load point.

_

d. Isochronous governor. A governor with auto-matic reset which compensates for speed droop.Constant engine speed is maintained regardless ofload.

e. Governor output. Measure of power the gover-nor can provide to activate the fuel control mecha-nism. Expressed in pounds per inch or pounds perfoot.

GroundingGrounding is the connection of a low resistance me-tallic conductor between the power distribution sys-tem’s neutral lead and earth (or an equivalent con-ducting body). Grounding safely clears line-to-ground faults.

HertzA unit of frequency equal to one cycle per second(refer to alternating current).

HuntingPeriodic increase and decrease (oscillation) inspeed, voltage, or other quantity.

InjectorMeters, times, and pressurizes fuel to be deliveredto the cylinder.


Magnetism SwitchgearProperty of certain materials which exerts a me-chanical force, attraction or repulsion, on an adja-cent mass of similar materials.

General term, covers switching and interrupting de-vices including their associated control, instrumen-tation, metering, protective devices, and housing.Used relative to generation, transmission, distribu-tion, and conversion of electric power.Otto cycle

The operating principle by which a piston (recipro-cating) engine operates, called constant volumecombustion.

Polychlorinated biphenylsPCB, a liquid with high dielectric strength that wasused as an insulator in power transformers, relays,circuit breakers, etc.

ScavengingThe removal of exhaust (burned) gases from thecylinders of a piston (reciprocating) engine. Also,refers to the collection and removal of excess lubri-cating oil from a bearing housing in a gas turbineengine.

SuperchargeA method of increasing the volume of air charge inthe cylinders of piston engines to produce higherpower output. A belt or chain driven blower is usedto supercharge an engine.

TachometerInstrument that measures angular speed, such asthat of a rotating prime mover shaft. Tachometerscovered herein usually use a magnetic pick-up tosense speed.

Two-cycle (two-stroke) engineA reciprocating (piston) engine using diesel oil forfuel. The engine produces one power impulse percylinder for every two strokes of the piston. Onestroke is one pass through the cylinder.

TurbochargeA method of increasing the volume of air charge inthe cylinders of piston engines to produce higherpower output. Flow of exhaust gases operates a tur-bocharger.

Voltage regulatorA device which controls the output voltage of a gen-erator.

Glossary 3

v

TM 5-685/NAVFAC

INDEX

MO-912

.Air intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–9Alternator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4–5

Polyphase . . . . . . . . . . . . . . . . . . . . . . . . . . ...4-5a(1)Single . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4-5a(2)

Auxiliary power . . . . . . . . . . . . . . . . . . . . . . ..1–1,2–3aBatteries . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . ..5–9cBearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4–11

Ball bearings . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-llcSleeve bearings . . . . . . . . . . . . . . . . . . . . . . . ..4-llb

Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–21Cooling system . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–5

Air-cooled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–5aCoolant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5c(4)(f)Liquid-cooled . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–5b

Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4–7bCurrent transformers . . . . . . . . . . . . . . . . . . . . . ..5–3cDiesel Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–2Distribution systems . . . . . . . . . . . . . . . . . . . . . . . ..2–6

Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . ..2–6.2–7Power factor . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–6a

Emergency generators . . . . . . . . . . . . . . . . . . . . . ..2–2cEmergency power . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–1Engine timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–3cEquipment grounding . . . . . . . . . . . . . . . . . . ..2–8k(8)Exciters . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–l0a, 4-8

Brush-type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-8cCurrent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-9bPower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-9dRotating-rectifier . . . . . . . . . . . . . . . . . . . . . . . ..4–8fSpeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-9cStatic exciters . . . . . . . . . . . . . . . . . . . . . . . . . .. .4-8gVoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4-9a

Exhaust system . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–10Field flashing . . . . . . . . . . . . . . . . , . . . . . . . . . . ...4-10Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–3e(2)Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–3e( 1)Four-cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–3bFrequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-7dFuel injection system . . . . . . . . . . . . . . . . . . . . . ..3–4aFuel storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–4

Day tanks, . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–4dFuel system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–4Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–9h

Current limiting fuses . . . . . . . . . . . . . . . 5–9h(2)(a)Expulsion fuse . . . . . . . . . . . . . . , . . . . . ..5–9h(2)(d)Glass-enclosed fuse . . . . . . . . . . . . . . . . ..5–9M2)(c)Metal-enclosed fuse . . . . . . . . . . . . . . . . ..5–9h(2)(b)

Gas turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–lbGas turbine engines . . . . . . . . . . . . . . . . . . . . . . ..3–13Generator operation . . . . . . . . . . . . . . . . . . . . . . . ...4-2

Exciter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4–2bAC generators . . . . . . . . . . . . . . . .. 4-2b. 4-3a, 4-4Coils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4–2a

DC generators . . . . . . . . . . . . . . . . . . . . . . . . . ..4–3bVoltage regulator . . . . . . . . . . . . . . . . . . . . . . . ..4–2c

Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4–1Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–8.3–20

Electronic (Isochronous) . . . . . . . . . . . . . . . .3–8g(4)Hydraulic governor . . . . . . . . . . . . . . . . . . ..3–8g(2)Mechanical governor. . . . . . . . . . . . . . . . . ..3–8g(l)Pneumatic governor.. . . . . . . . . . . . . . . . . ..3–8g(3)

Governors . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–10b(2)Ground grid . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–8k(2)Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–8

Equipment grounding . . . . . . . . . . . . . . . . . . ..2–8bGround fault . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8f(1)Ground fault current . . . . . . . . . . . . . . . . . . . . . . 2-8jHigh-resistance grounding . . . . . . . . . . . . . . . ..2–8iLow-resistance grounding . . . . . . . . . . . . . . . . 2–8hNeutral potential . . . . . . . . . . . . . . . . . . . . . ..2–8f(l)Resistance grounding . . . . . . . . . . . . . . . . . . ..2–8hSolid grounding . . . . . . . . . . . . . . . . . . . . . . ..2–8g(2)Solidly grounded . . . . . . . . . . . . . . . . . . . . . . . . ..2–8gSystem grounding. . . . . . . . . . . . . . . . . .12–8a.,2–8d

Grounding systemGround bus . . . . . . . . . . . . . . . . . ... . . . . . . ..2–8k(l)Grounding conductors . . . . . . . . . . . . . . . .2–8k(9)(c)Grounding electrodes. . . . . . . . . . . . . . . ..2–8k(9)(a)

Harmonic current . . . . . . . . . . . . . . . . . . . . . . ..2–8k(1)Hospitals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–lb(1)Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–7Insulation testing . . . . . . . . . . . . . . . . . . . . . . . ...4-13Lightning arresters, . . . . . . . . . . . . . . . . . . . . . . ..5–9eLoad shedding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–9Loads . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . ..2–5Low voltage switch gear..... . . . . . . . . 5–2a(l),5–3

Air circuit breakers . . . . . . . . . . . . . . . . . . ..5–3a(1)Circuit breakers . . . . . . . . . . . . . . . . . . . . . . . ..5–3a

Lubrication system . . . . . . . . . . . . . . . . . . . ..3–6.3–18Lube oil . . . . . . . . . . . . . . . .3-6a(10)(a), 3–6a(10)(d)

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..7–1Medium voltage . . . . . . . . . . . . . . . . . . . ..5–2a(2), 5–4

Air circuit breakers . . . . . . . . . . . . . . . . . . ..5–4a(2)Circuit breakers . . . . . . . . . . . . . . . . . . . . . . . ..5–4aCurrent transformers . . . . . . . . . . . . . . . . . . . ..5–4cOil circuit breakers . . . . . . . . . . . . . . . . . . ..5–4a(1)Potential transformers . . . . . . . . . . . . . . . . . . . 5–4bVacuum circuit breakers . . . . . . . . . . . . . . ..5–4a(3)

Oil filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–6iOil purification . . . . . . . . . . . . . . . . . . . . . . . . . . ..8–laOperational testing . . . . . . . . . . . . . . . . . . . . . . . . ..6–7Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–2bPolarities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–3dPortable diesel . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–2ePortable power plants . . . . . . . . . . . . . . . . . . . . ..2–2dPotential transformers . . . . . . . . . . . . . . ..5–3b.5–4b

Index 1

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Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7ePower Factor . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-7e(3)Power generation . . . . . . . . . . . . . . . . . . . . . . . . . . ..2–2Prime movers . . . . . . . . . . . . . . . . . . . . ..2–3c, 3–1, 7–2Protective relays . . . . . . . . . . . . . . . . . . . . . . . ..5–8a(2)

Current balance . . . . . . . . . . . . . . . . . . . . .5-8a(2)(g)Differential . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8a(2)(f)Ground fault protection . . . . . . . . . . . . . 5-8a(2)(h)Overcurrent . . . . . . . . . . . . . . . . . . . . . . . ..5–8a(2)(cz)Overvoltage, . . . . . . . . . . . . . . . . . . . . . ...5-8a(2)(b)Reverse Power . . . . . . . . . . . . . . . . . . . ...5-8a(2)(d)Underfrequency . . . . . . . . . . . . . . . . . . . . ..5–8a(2)(e)Undervoltage . . . . . . . . . . . . . . . . . . . . . ...5-8a(2)(c)

Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–6Electro-mechanical voltage regulators . ..5–6a(1)Static exciter regulators . . . . . . . . . . . . . . . .5–6a(3)Static voltage regulators. . . . . . . . . . . . . . . . 5–6a(2)

Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–8Overload . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–8a(l)(b)Solid-state . . . . . . . . . . . . . . . . . . . . . . . . ..5–8a(l)(d)Time delay . . . . . . . . . . . . . . . . . . . . . . . . ..5–8a(l)(c)Voltage sensitive, . . . . . . . . . . . . . . . . . ...5-8a(l)(e)

Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-6bSemi-automatic mode . . . . . . . . . . . . . . . . . . . . ..6-2bSlip rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-6dSpeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-7cSpeed control . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–20

Starting system . . . . . . . . . . . . . . . . . . ..0. ..3–7.3–19Air starting . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–7bElectric starting . . . . . . . . . . . . . . . . . . . . . . . ..3–7a .

Stator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-6cStroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3–laSurge capacitors . . . . . . . . . . . . . . . . . . . . . . . ..5–9d(l)Switchgear . . . . . . . . . . . . . . . . . . . . .. 2–10g, 5–1, 7–4

Voltage classification . . . . . . . . . . . . . . . . . ... .5-2aSynchroscope . . . . . . . . . . . . . . . . . . . . . . . . ..5-9i, 6-5eTest equipment.....,...,.,.. . . . . . . . . . . . . . ..5–9g

Ammeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9g(5)Electrical analyzer . . . . . . . . . . . . . . . . . . . ..5-9g(9)Frequency meter . . . . . . . . . . . . . . . . . . . . . ..5–9g(6)Megohmmeter . . . . . . . . . . . . . . . . . . . . . . . ..5–9g(8)Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9g( 1)Ohmmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9g(4)Voltammeter . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9g(3)Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-9g(2)Wattmeter . . . . . . .... .. . . . . . . . . . . . . . . . . 5–9g(7)

Tie Breaker . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5–3e(2)Transfer switches . . . . . . . . . . . . . . . . . . . . . 2-10f, 5-5Two cycle . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . ..3–3Vans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-7e(2)Voltage, generated . . . . . . . . . . . . . . . . . . . . . . ...4-7aVoltage regulators . . . . . . . . . . . . . . . . . . ..2–10e. 5-6Watts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-7e(l)

Index 2


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c

The proponent agency of this publication is the Office of theChief of Engineers, United States Army. Users are invited to sendcomments and suggested improvements on DA Form 2028 (Rec-ommended Changes to Publications and Blank Forms) directlyto Director, U.S. Army Center for Public Works, ATTN: CECPW-EE,7701 Telegraph Rd., Alexandria, VA 2231593862.

By Order of the Secretaries of the Army and the Navy:

DENNIS J. REIMERGeneral, United States Army

Chief of StaffOfficial:

patiJOEL B. HUDSON

Administrative Assistant to theSecretary of the Army

D. J. NASHRear Admiral CEC, United States NavyCommander, Naval Facilities Engineering

Command

Distribution:Army:

To be distributed in accordance with initial distribution number(IDN) 344596, requirements for TM 5-685.

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rr

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EMERGENCY/AUXILIARY GENERATOR OPERATING LOG (INSPECTION TESTING)

1. ENGINE DATA3. MAKE

J. SERIAL NUMBER

c. HOUR METER

b. MODEL

d. RPM

(1) START (2) FINISH

6. VOLTAGE REGULATOR (See Note 7)

U N

a. REGULATORMOUNTS

b. RHEOSTAT CONDITIONlCorroded,connecrions,etc.

REMARKS

1 7. AUTOMATIC TRANSFER PANEL (See Note 1)f. INSPECTION TEST OPERATOR

h. BASE/POST

2. ALTERNATOR DATA

I

g. DATE REMARKS

a. CONTACTS BURNEDi. UNIT

’ b. MECHANISM BINDING

m. MAKE b. MODEL I c . WIRINQ DAMAQED

:. SERIAL NUMBER d. KW RATING d. COMPONENTSOVERHEATED

a. VOLTS f. PHASE

.8. SHOP SUPERVISOR h. DATE

I. LOCATION (Building) j. RECORD IDENT NUMBER

3. GENERAL CONDITIONS (See /Vote 1)

8. COOLING SYSTEM (See /Vote 21a. TEMP. DURING STANDBY’ b. TEMP. DURING OPERATIONS

c. COOLANT ADDED (Level) d. ANTIFREEZE PROTECTION (SeeNote 3)

e. FAN BELT CONDITION f. RADIATOR AND LOUVER CON-

DITION

II. CLEANLINESS

b. EXHAUSTCONDITION

U N REMARKS 9. LUBE OIL SYSTEMa. OIL CHANGED /XI b. OIL ADDED (Sum level)

YES NO YES NO

c. LUBE OIL CONDITION Wiscosifyl d. LEVEL IN GOVERNOR

c. ENGINE VIBRATION

d. LOOSE ITEMS(Bolts. Linkage, etc. I

ITEM (See Note 21

. 10. KW LOAD

11. AMPERAGE

ALTERNATOR

PHl PH2 PH3

EXCITER

c. TURBO VIBRATIONPHl PH2 PH3

12. VOLTAGEf. WATER LEAKS (XI g. LOCATION OF LEAK

YES NO 13. BRUSHES AND4. FUEL SYSTEM {See Note 1) BRUSHES RIGGING

S U N REMAFiKS 14. SLIP RINGa. FUEL LEVEL /Day Tank) CONDITION

16. COMMUTATORb. FUEL LEVEL (Storage CONDITION

Tank) 16. VOLTAGE PHl PH2 PH3

c. WATER DRAINED fX/ d. FUEL LEAKS /XI /Commercial)

YES NO YES NO 17. BATTERY CHARGERc. LOCATION OF LEAK a. VOLTS b. AMPS

I I5. BATTERY BANK /See Note 1) 1 18. HYDROMETER 1 19. STARTING AIR 1 20. AMBIENT

a. CONNECTIONS

U N REMARKS READING Psi) TEMP. l“FI

21. FILTER CHANGE

b. CLEANLINESS

c. ELECTROLYTE LEVEL

a. LUBE OIL /XI b. FUEL /XI c. AIR INTAKE /XI

YES NO YES NO YES NO

22. UNIT STARTED ON /XI

1ST TRY 2ND TRY 3RD TRY NOT AT ALL

Use the reverse side of this form and/or 8-l /2 x 1 1” paper if required for additional comments, continuation of item entries (identify by itemnumber), and for corrective action(s) taken.NOTE 1: Mark S for Satisfactory, U for Unsatisfactory, N for Normal, or indicate in Remarks column, as applicable.NOTE 2: Enter data as indicated. Where no instrumentation is provided, indicate Satisfactory, Unsatisfactory, etc., as applicable.NOTE 3: Enter Antifreeze Protection as the freeze temperature in degrees (F) as indicated on an appropriate hydrometer.

DD FORM 2744, MAY 96 LOCAL REPRODUCTION AUTHORIZED.


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"U.S. G.P.0.:1996-404-611:40009

operation, maintenance and repair of ......army tm 5-685 navy navfac mo-912 operation, maintenance...

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