noncoring secrey...recommendation: revise the foreword as follows: foreword. this document is...

Report of the Committee on Boiler Combustion System Hazards

Technical Correlating Committee

Dale E. Dremel, Om/r Monsanto Co., MO [U]

Merton W. Bunker, Noncoring SecreY.ary Nat'l Fire Protection Assn., MA

Courtney D. Alvey, Lutherville, MD [SE] William H. Axtman, Gray Gull Assoc., Inc., VA [SE] ohnny W. (Bill) Bass, Forney Corp., TX [M]

es IL Bostick, Bailey Controls CO., OH [M] dem BukowsH, Underwriters Laboratories Inc., IL [RT]

Paul L. Cioffi, Babcock & Wilcox, OH [M] William E. Cunnlngham, Jr., Raytheon Engr & Constructors, MA

[SE] ohn C. deRuyter, The DuPont Co., DE [U] obert S. Elek, Kemper Insurance, OH [I]

Ronald F.. Fringeli, M&M Protection Consultants, OH [I] Steven IL Funk, The DuPont Co., TX [U] Pep. American Petroleum Inst.

Gordon G. Gaetke, Union Carbide Corp., WV [U] Masaaki Kinoshita, Mitsubishi Heavy Industries Lid, [M] DonaldJ. L. Lin, Qilln Inc., TX [SE] Francis X. Maskol, Honeywell, Inc., PA [M] Russell N. Mosher, American Boiler Mfrs. Assn., VA [M]

~ r r y J . Moskal, ABB Combustion Engr, Inc., CT [M] ichaei C. Polagye, Factory Mutual Research Corp., MA[I]

George P. Seroka, The Detroit Edison Co., MI [U] James I , Sherman, B',dtimore Gas & Electric Co., MD [U] Henry IL Wong, Foster Wheeler Energy Corp., NJ [M]

Alternates

Te~uyal Fujino, Mitsubishi Heavy Industries America, Inc., CA t*,LJ

(Alt. to M. Kinoshita) Raymond J. Heitland, Monsanto Co., FL [U]

(Alt. to D. E. Dressel) Dennis P. Jenkins, Kemper Nat'l Insurance Cos., NC [I]

(Alt. to 1L S. Elek) John P. O'Rourke, ABB Combustion Engr, Inc., CT [M]

(Air. to J . J . Moskal) RichardJ. Wachter, Industrial Risk Insurers, CT [I]

(Voting Alt. to IRI Rep.) J. C. Waung, Babcock & Wilcox CO., OH [M]

(Alt. to P. L. Cioffi) William G. Yeich, Exxon Research and Engr, Co., NJ [U]

(Alt. to S. K. Funk)

Nonvoting

Wilfiam H. Axtman, Gray Gull Assoc., Inc., VA Shelton Ehrlich, Palo Alto, CA Thomas B. Hamilton, Hamilton Consulting Services, NC Robert P. Kaltenbech, Burns & McDonnelfEngr, MO Peter B. Matthews, Hartford Steam Boiler Insp & Ins Co., CT PeterJ. Gore Wlllse, Industrial Risk Insurers, CT

StalfLialson: Merton W. Bunker, Jr.

Committee Scope: This Committee shall have primary responsibility for documents on the reduction of combustion system hazards in single- and multiple-burner boilers with a heat input rate of 12,500,000 Btu/hr and above. This includes all fuels. This Committee also is responsible for documents on the reduction of hazards in pulverized fuel systenm, fluidized-bed boilers, heat recovery steam generators, and stoker-fired boilers, at any heat input rate.

Technical Committee on

Heat Recovery Steam Generators

Peru- B. Matthews, Chair Hartford Steam Boiler Imp & Ins Co., CT [I]

Samuel H. Allen, Dow Chemical U.S.A., LA [U] David Paul Cannon, Houston Lighting & Power, TX [U] James F. Carberry, Jr., American Insurance Services Group, NY [I] lan M. Clark, ABB Combustion Engr Services, Inc., CT [M] Ralph S. Clemens, InterGen, MA [I3] James W. Dunlap, DuPont Power, DE [U] Gordon G. Gaetke, Union Carbide Corp., WV [U] Paul A. Giansirecusa, United Engr & Constructors, MA [SE] Alfred W. Grusi, John Zink Co./Div. Koch Engr, Co., OK [M] Harold F. Honath, Jr., Coen Co. Inc., CA [M] Robert P. Kaltenbach, Burns & McDonnell Eng, MO [SE] George Y. Keller, Burns & Roe Enterprises, Inc., NJ [SE] Steven J. Knott, Westinghouse Electric Corp., FL [M] Steven A. Lefton, Aptech Engr Services, CA [SE] Francis X. Muskol, Honeywell, Inc., PA[M] Russell N. Mosher, American Boiler Mfrs. Assn., VA [M] Martin C. Nygard, Nooter/Eriksen, MO [M] Owen M. Preiton, Factory Mutual Engr, FL [I] Kishin Sujan, Callidus Teclmologies Inc., OK [SE] John Van Name, Raytheon Engr & Constructors, NY [SE] Joseph M. Vavrek, Sargent & Lundy, IL [SE] James M. Witt, Jr., Southern Co. Services Inc., AL [U]

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Alternates

Donald W. Bairley, ABB Combustion Engr Systems, CT [M] (Alt. to I. M. Clark)

Rick Fioreaza, Coen Co., Inc., CA [M] (Alt. to H. F. Honath)

Allan G. Gilson, Burns & McDonnell, MO [SE] (AIt. to R. P. Kaltenbach)

W. J. Johnson, The Dow Chemical Co., TX [U] (Alt. to S. H. Allen)

Gerald E. McCullion, Honeywell I.A.C., PA [M] (AIt. to F. X. Maskol)

Michael C. Polagye, Factory Mutual Research Corp., MA[I ] (Alt. to O. M. Preston)

Stephen L. Somers, John Zink Co/Division of Koch Engr, Co., OK [M]

(Alt. to A. W. Grusi) Stephen B. Statz, Raytlleon Engr & Constructors, NY [SE]

(Alt. toJ . Van Name) Robert H. Warburton, Jr., J. Makowski Mgmt., Co., RI [U]

(Alt. to R. S. Clemens)

Shaft Liaison: Merton W. Bunker, Jr.

These lists represent the membership at the time each Committee was balloted on the text of this edition. Since that time, change~ in the membership may have occurre& A key to classifications is found at the back of this document.

Committee Scope: This Committee shall have primary responsibility for documents covering the operation of heat recovery steam generators and die related reduction of combustion system hazards and prevention of boiler furnace explosions. This includes all fuels at any heat input rate.

The Report of the Committee on Bailer Combustion System Hazards is presented for adoption.

This Report was prepared by die Technical Committee on Heat Recovery Steam Generators, and proposes for adoption amendments to NFPA 8506-1995, Standard on Heat Recovery Steam Generator Systems. NFPA 8506-1995 is published in Volume 9 of the 1997 National Fire Codes and in separate pamphlet form.

This Report has been submitted to letter ballot of the Technical Committee on Heat Recovery Steam Generators, which consists of 23 voting members. The results of d~e balloting, after circulation of any negative votes, can be found in die report.

This Report has also been submitted to letter ballot of the Technica/Correlat ing Committee on Boiler Combustion System Hazards, which consists of 23 voting members; of whom all 23 voted affirmatively.

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(Log #16) 8506- 1 - (Foreword): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Add to, or modify last paragraph as follows:

"...heat recovery steam genera tor systems and...". SUBSTANTIATION: This establishes the in tent to address the CT safety issues as they apply to the HRSG. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMI'Iq 'EE ACTION:

AFFIRMATIVE: 19 NOT RETURNED: 4 Carberry, Dunlap, Giatasiracusa, Witt

(Log #59) 8506- 2 - (Foreword): Accept SUBMITTER: Francis X. Maskol, Honeywell, Inc. RECOMMENDATION: Revise the Foreword as follows:

Foreword. This documen t is in tended to be used in the design, installation,

operation, and maintenance of heat recovery steam generator systems. It is not possible for dais s tandard to encompass the specific hardware applications, nor should it be considered a "cookbook" for the design of a safe HRSG system.

The simplest combined cycle plant automatically has certain hazards that are common to all designs. Coupling various designs of heat recovery unit~ with combustion turbines of varying characteristics in different configurations (such as varying damper arrangements) can produce very unique hazards.

The potential ineffective use of the combustion turbine as the source of the purge and potential sources of substantial fuel enter ing the HRSG f iom normal and false starts are major considerations that need to be addressed.

Other concerns include special provisions such as automatic transfer during transients, multiple stacks that can create reverse flows, internal maintenance of the HRSG with the combustion turbine in operation, multiplicity of cross connect ions between units to prevent shutdown, a n d / o r fitting it into a small space using f inned tubes which ate more sensitive to temperature a n d s u b j e c t to iron fires.

Insufficient failure analysis of arrangements , configurations and equipment may increase the number of damaging incidents, lost product ion and the possibility of personal injury or death.

It is vital that the designer of the combustion turbine and any burner safety system(s) be completely familiar with the features, characteristics, and limitations of the specific hardware and also possess a thorough unders tanding of this s tandard and its intent. SUBSTANTIATION: The suggested wording is more descriptive of the potential hazards that are particular to heat recovery steam

neration systems than the existing wording. MMITTEE ACTION: Accept.

NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 19 NOT RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

(Log #17) 8506- 3 - (1-1.I): Accept in Principle SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Last paragraph of Section I d A should be reworded and num bered accordingly..

"The heat recovery steam generator (HRSG) shall be unfired, or supplemental f i red by either natural gas or fuel oil." SUBSTANTIATION: 1-1.1 aplblies to combustion turbines. Last paragraph should be d e t a c h e d f o r clarity and style. COMMITTEE ACTION: Accept in Principle.

1. Revise Section 1-1.1 to read as follows: "This standard shall apply to steam generators that recover heat

f rom a combust ion turbine. 1-1.1 The combustion turbine shall be permit ted to fire the

following fuels ei ther alone or in combination: (a) Natural gas; (b) No. 2 fuel oil; (c) Kerosene; (d) JP-4 je t fuel; (e) Diesel fuel. 1-1.1.2 The HRSG shall be permi t ted to be unfired, or

supplemental firing shall be permi t ted to be provided f rom natural gas or fuel oil, as def ined in dais standard.

2. Delete existing Section 1-1.5. 3. Add a new 1-1.3 z.s follows:

1-1.3 This s tandard does not specifically address the firing of fuels other than those specified in 1-1.1.1 and 1-1.1.2. This s tandard is in tended to apply to other fuels not covered by 1-1.1.1 and 1- 1.1.2 (see 1-2.2). Other fuels can have unique characteristics requir ing special design and operat ion considerations for fuel handling, purging, and burning.

4. Renumber Sections 1-1.3 and 1-1.4 as 1-1.4 and 1-1.5 respectively. COMMITTEE STATEMENT: Changes to the submitter 's proposed text were for consistency and satisfy the intent of the submitter. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #18) 8506- 4 - (1-1.2): Accept SUBM1TTER: Peter B. Matthews, Hartford Steam Boiler

I RECOMMENDATION: Replace "...is not to dictate..." etc. with "...shall not be construed to dictate...". SUBSTANTIATION: Need "shall" in paragraph. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #19) 8506- 5 - (1-1.3): Reject SUBMITTER; Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Revise text as follows:

"This standard shall not be applied to simultaneous...". SUBSTANTIATION: Style ..."shall". COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The existing wording meets the intent of the Committee. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #20) 8506- 6 - (1-1.5): Reject SUBMITTER: Peter B. Matthew's, Hartford Steam Boiler RECOMMENDATION: Revise the second sentence to read:

"...This s tandard shall not apply to fuels not covered by Section 1- 1.1 (see Section 1-2.2)...'. SUBSTANTIATION: Second sentence contradicts opening sentence. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The Commit tee disagrees with the submitter 's p roposed change and substantiation because the s tandard is in tended to apply to fuels no t covered by Section 1-1.1. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #21) 8506- 7- (1-1.7): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Add the following text after the first sentence:

", nor does it address single or multiple combustion turbines exhausting into multiple heat recovery steam generators through a header." SUBSTANTIATION: As written it permits multiple CTS into multiple HRSGs which is incorrect. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


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(Log #13) 8506- 8- (1-1.9): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Delete Section 1-1.9. SUBSTANTIATION: Redundant text and incorrect as Chapter 8 covers all configurations. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #14) 8506- 9- (1-1.10): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler

I RECOMMENDATION: Delete Section 1-1.10. SUBSTANTIATION: No longer applicable to revised document. COMMITTEE ACTION: Accept. NUMBER OF COMMIT]?EE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #15) 8506- 10 - (1-1.11): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler

[ RECOMMENDATION: Delete Section 1-1.11. SUBSTANTIATION: See Index - Redundant text. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #22) 8506- 11 - (1-2.1): Accept in Principle SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Delete "shall" in third sentence and change "require" to "requires". SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept in Principle.

Revise existing Section 1-2.1 to read as follows: 1-2.1 The purpose of this standard shall be to: (a) contribute to operating safety;, (b) prevent explosions, implosions, and uncontrolled fires in

HRSG sections and exhaust ductwork; (c) establish minimum standards for the design, installation,

operation, and maintenance of heat recovery steam generators and their fuel-burning, air supply, and combustion products removal systems;

(d) Require the coordination of operating procedures and components, control systems, interlocks, and structural design;

(e) Require the establishment of training programs in equipment operation and maintenance, for both new and existing personnel, to ensure that minimum standards for operation and maintenance are understood and followed. COMMITTEE STATEMENT: The changes were editorial to comply with the Manual of Style. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #23) 8506- 12- (1-2.3): Reject SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Change to:

"Emphasis shall be placed..." SUBSTANTIATION: Style - editorial. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The existing wording correlates with NFPA 8501 and NFPA 8502. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23

VOTE ON COMMITTEE ACTION: AFFIRMATIVE: 19 NOT RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

(Log #10) 8506- 13 - (2-1.7 Note and D-l.3 (New)): Accept in Principle SUBMITTER: Alfred W. Grusi, John Zink, a KOCH Industries Company RECOMMENDATION: Delete the "NOTE" and replace with the followingtext:

2-1.7 HRSG Enclosure, Fin-Metal Tube Fires. (Iron Fires) CAUTION: Due to misoperation, there have been occurrences

of fin-metal tube fires in HRSG's, and there is a need to address this potential. Iron fires in conventional and marine boilers have also occurred principally in air preheaters. The reader is directed to a reference/ist in Appendix D-1.3 for specific articles related to iron fires which in turn have references to previous literature.

CAUTION: At a temperature of approximately 1060 degrees Fahrenheit (571 degrees Centigrade), carbon steel fins oxidize at an accelerated rate, and with insufficient cooling, an iron fire is inevitable.

Add a new Appendix "D" item as follows: D-1.3 Reference Literature Regarding Iron Fires McDonald, C.F., "The Potential Danger of Fire in Gas Turbine

Heat Exchangers" ASME Paper No. 69-GT-38 Theoclitus, G., "Heat Exchanger Fires and the Ignition of Solid

Metals" Journal of Engineering for Gas Turbines and Power, July 1985,

Vol 107, pp 607-612 Johnson, A.A., Von Franuhofer, J.A., and Jannett, E.W., "Combustion of Finned Steel Tubing During Stress Relief Heat

Treatment" Journal of Heat Treating, June 1986, Vol. 4, No. 3 ,pp 265-271

SUBSTANTIATION: The potential for uncontrolledfire from any source warrants further clarification. The existing note, although good, did not give adequate information regarding this potential hazard. The addition to reference material in the appendix will educate those inexperienced in this matter. The strong "CAUTIONS" will direct attention to the text on the hazard.

It is asked that this change be incorporated so that a greater awareness is brought to the users of this standard and this industry in general about fin-metal tube fires. COMMITTEE ACTION: Accept in Principle.

Revise the submitter's proposal as follows: 1. Delete the "NOTE" andreplace with the following text:

* 2-1.7 HRSG Enclosure, Fin-Metal Tube Fires. (Iron Fires) CAUTION: Due to misoperation, there have been occurrences

of fin-metal tube fires in HRSG's, and there is a need to address this potential. The reader is directed to a reference list in Appendix D-1.3 for specific articles related to iron fires which in turn have references to previous literature.

2. Add a new A-2-1.7 to read as follows: Iron fires in conventional and marine boilers have also occurred

principally in air preheaters. At a temperature of approximately 1060 degrees Fahrenheit (571 degrees Centigrade), carbon steel fins oxidize at an accelerated rate, and with insufficient cooling, an iron fire is inevitable.

3. Add a new Appendix "D" item as follows: D-1.3 Reference Literature Regarding Iron Fires McDonald, C.F., "The Potential Danger of Fire in Gas Turbine

Heat Exchangers" ASME Paper No. fi9-GT-38 Theoclitus, G., "Heat Exchanger Fires and the Ignition of Solid

Metals" vJournal of Engineering for Gas Turbines and Power, July 1985, ol 107, pp 607-612 Johnson, A.A., Von Franuhofer, J.A., and Jannett, E.W., "Combustion of Finned Steel Tubing During Stress Relief Heat

Treatment" cJoournal of Heat Treating, June 1986, Vol. 4, No. 3, pp 265-271.

MMITTEE STATEMENT: The Committee relocated the sentence in the caution note because it refers to air preheaters and marine boilers, which are not directly covered by this standard. The Committee consensus was that the specific temperature information was explanatory in nature. Other changes were for clarity and consistency. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23

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VOTE ON COMMITrEE ACTION: AFFIRMATIVE: 19 NOT RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

(Log #24) 8506- 14- (2-1.7.3): Reject SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Revise text with:

"Recognition of a fin-metal fire shall result in operator action to initiate a master fuel trip." SUBSTANTIATION: Removing fuel from CT and HRSG is a MFT. COMMITTEE ACTI(~N: Reject. COMMITTEE STATEMENT: The submitter's substantiation is incorrect by the definition of a Master Fuel Trip. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMI'ITEE ACTION:


(Log #CPS) 8506- 15 - (2-3.3, 4-1.1, 4-3.1, 5-3.2.3.12, and 7-4.5): Accept SUBMITTER: Techrfical Committee on Heat Recovery Steam Generators

I RECOMMENDATION: Change the word "Note" to "CAUTION" in the notes following Sections 2-3.3, 4-1.1, 4-3.1, 5-3.2.3.12, and 7-4.5. SUBSTANTIATION: These changes were for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. The Committee consensus is to emphasize the importance of the statement, rather than place the material in Appendix A. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #12) 8506- 18 - (3-1 Damper; Damper, Air Inlet; Damper, Bypass; Damper, Diverter; Damper, HRSG Isolation; Damper, Stack; False Start; Positive Means of HRSG Isolation; Stack, Bypass (New)): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Add the following new definitions to Chapter 3:

Damper*° A mechanical device for controlling or blocking gas flow to a specific component.

Damper, Air Inlet. A damper used to admit fresh air into the HRSG, either as an alternative method of purging or to supply combustion air when the combustion turbine is out of service. See DM4 on Figure A-3-1 Damper.

Damper, Bypass. A damper that allows combustion turbine exhaust gases to bypass the HRSG. See DM1 on Figure A-3-1 Damper.

Damper, Diverter. A damper that is used to select alternate gas paths.

Damper, HRSG Isolation. A damper used to block combustion turbine exhaust gases from entering the HRSG. See DM2 on Figure A-3-1 Damper.

Damper, Stack. A damper used to block gas flow through the stack. See DM3 on Figure A-3-1 Damper.

False Start. A condition where the combustion turbine fails to complete its ignition sequence (failure to start) and may result in unburned fuels entering the HRSG enclosure.

Positive Means of HRSG Isolation. A device in the gas path to the HRSG, which will completely prevent turbine exhaust gas entrance to the HRSG and allow personnel entry into the HRSG enclosure (e.g., a blocking plate).

Stack, Bypass. A stack applied in addition to and separate from the normal HRSG exhaust stack that allows combustion turbine exhaust gas to flow independently to atmosphere. SUBSTANTIATION: Needed definitions to append the standard. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CP4) 8506- 16 - (3-1 Air, Excel) : Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators

] RECOMMENDATION: 1. Delete the note following the definition of "Air, Excess".

2. Add the following sentence to the definition of "Air, Excess" as a new second sentence:

"This is not "Air-Rich" as defined in this section." SUBSTANTIATION: This change was for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 2~ VOTE ON COMMITI'EE ACTION:


(Log #58) 8506- 17 - (3-1 Augmented Air Firing): Accept SUBMITrER: Harold Honath, Coen Co., Inc. RECOMMENDATION: Revise the definition of Augmented Air Firing, as follows:

"Supplementary firing with the addition of air at the duct burners to support and stabilize combustion, or imvrove emissions." SUBSTANTIATION: Augmented air firing is sometimes included

Vothe burner manufacturer solely to improve emissions. MMITTEE ACTION: Accept.


AFFIRMATIVE: 19 NOT RETURNED: ~ Carberry, Dunlap, Giansiracusa, Witt

(Log #25) 8506- 19 - (4-5.1.1 (New)): Accept in Principle SUBMITTER: Peter B. Matt.hews, Hartford Steam Boiler RECOMMENDATION: Add new Section 4-5.1.1 as follows and renumber accordin g . l F.

"The owner or designated representative shall establish minimum levels of education and competence in the selection and

~ ualification of new operators." UBSTANTIATION: Prior loss history indicates operator

~ t~)alification problems. MMITTEEACTION: Accept in Principle.

I Add revised new Section 4-1.1.5 as follows and renumber I accordingly:

"The owner or designated representative shall establish minimum levels of education and competence to be used in the selection and qualification of operators." COMMITTEE STATEMENT: Changes to text were editorial. Relocation of section was to bring the requirements under the a~leneral requirements prior to training requirements because they

to selection of new operators. BElt OF COMMFVI'EE MEMBERS ELIGIBLE TO VOTE: 23

VOTE ON COMMITTEE ACTION: AFFIRMATIVE: 19 NOT RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

(Log #26) 8506- 20 - (4-6.5 (New)): Reject SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Add new Section 4-6.5:

"Process and instrumentation drawings shall be updated to reflect changes or modifications from initial drawings." SUBSTANTIATION: SOP. COMMITTEE ACTION: Reject~ COMMITTEE STATEMENT: This proposed change is already covered by Section 4-6.4.

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N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 VO TE O N COMMITTEE ACTION:


(Log #CPS) 8506- 21 - (5-1, 5-3.2.3.1, 6-5.1, 7-5.4.1, %5.4.2.1, and %5.4.2.2): Accept SUBMITTER: Technical Commi t t ee on Heat Recovery Steam Genera to r s RECOMMENDATION: Delete tile notes following Sections 5-1, 5-3.2.3.1, 6-5.1, 7-5.4.1, 7-5.4.2.1, a n d 7-5.4.2.2. S U B S T A N T I A T I O N : These changes were for compl iance with the Manual of Style, and NFPA Standards Council direct ion to el iminate notes in the body of the s tandard. T he Commi t tee consensus is to delete the notes because they are r edundan t . COMMITTEE ACTION: Accept. N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 V O T E ON COMMITTEE ACTION:

AFFIRMATIVE: 19 N O T RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

(Log #27) 8506- 22 - (5-2.1.1): Reject SUBMITTER: Peter B. Matthews, Har t ford S team Boiler RECOMMENDATION: Replace "stop valves" with "safety shutof f valves". S U B S T A N T I A T I O N : Consis tent with def ined text in 85 series. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: As def ined, "safety shu tof f valves" .applies to "main burne r s or igniters", a n d is no t used in the tu rb ine lnoustry. N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 V O T E ON COMMITTEE ACTION:


(Log #CP9) 8506- 23 - (5-2.1.1): Accept SUBMITTER: Technical Commi t t ee on Hea t Recovery Steam Ge nera tors RECOMMENDATION: Revise Section 5-2.1.1 to read as follows:

5-2.1.1 For fuel oil, two stop valves or equivalent valves in series, with p roof of closure, shall be provided in the oil line to the combus t ion turbine. Means shall be provided to prevent or relieve excess pressure between these valves. S U B S T A N T I A T I O N : These changes were for compl iance with the Manual of Style, and NFPA Standards Council direct ion to e l iminate notes in the body of the s tandard. T he Cormnit tee consensus is to make this no te manda to ry because of its impor t ance . COMMITTEE ACTION: Accept. N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #28) 8506- 24 - (5-2.1.2): Reject SUBMITTER: Peter B. Matthews, Har t ford S team Boiler RECOMMENDATION: Replace "stop valves" with "safety shutoff Valves". S U B S T A N T I A T I O N : To be consis tent with text. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Commi t tee Action a n d S ta tement on Proposal 8506-22 (Log #27). NUMBER OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #29) 8506- 25 - (5-2.2.2): Reject SUBMITTER: Peter B. Matthews, Har t ford Steam Boiler RECOMMENDATION: Replace "means" with s o m e t h i n g m o re definitive, (discussion) and in the Note: replace "stop valves" with "safety shut-off valves".

Do we m e a n "Permissive"? S U B S T A N T I A T I O N : Clarity a n d consistency. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Commi t t ee Action and S ta tement on Proposal 8506-22 (Log #27). Fur thermore , combus t ion tu rb ine controls are outside the scope of the d o c u m e n t . N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 VO TE O N COMMITTEE ACTION:


(Log #CP10) 8506- 26 - (5-2.2.3 (New)): Accept SUBMITTER: Technica l Commi t t ee on Heat Recovery Steam Genera to r s

I RECOMMENDATION: Convert the note following Section 5-2.2.2 to become a new Section 5-2.2.3 as follows:

5-2.2.3 The vo lume between the combus t ion turb ine stop valves shall be minimized . S U B S T A N T I A T I O N : This change was for compl iance with tile Manual of Style, and NFPA Standards Council direct ion to e l iminate notes in dae body of the s tandard. The Commit tee consensus is to make the no te manda to ry because of its impor tance . COMMITTEE ACTION: Accept. N U M B E R OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE O N COMMITTEE ACTION:


(Log #49) 8506- 27 - (5-2.3.1(g) (New)): Accept SUBMITTER: Harold H o n a t h , Coen Co., Inc. R E C O M M E N D A T I O N : Add a new i tem (g) to Section 5-2.3.1 as follows:

(g ) A u g m e n t e d air supply in operat ion, See Section 7-4.2.4. S U B S T A N T I A T I O N : Inter locking the a u g m e n t e d air system prior to s tar t ing the combus t ion tu rb ine ensures that combus t ion turbine exhaus t gases do no t penet ra te tile a u g m e n t e d air system and subsequent ly exit the HRSG system a n d en te r the opera t ing area.

Duct bu rne r s with a u g m e n t e d air systems are c o m m o n e n o u g h that material per ta in ing to it is worthy of inclusion in the main body of NFPA 8506. COMMITTEE ACTION: Accept. N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 V O T E ON COMMITTEE ACTION:


(Log #CPI 1) 8506- 28 - (5-2.3.2, and 6-4.1.1): Accept SUBMITTER: Technica l Commi t t ee on Hea t Recovery Steam Genera tors

I RECOMMENDATION'- In the CAUTION notes following Sections 5-2.3.2 and 6-4.1.1, change the word "shall" to "should". S U B S T A N T I A T I O N : These changes were for compl iance with the Manual of Style. COMMITTEE ACTION: Accept . N U M B E R OF COMMITTEE MEMBERS ELIGIBLE T O VOTE: 23 V O T E ON COMMITTEE ACTION:


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(Log #CP12) 8506- 29 - (5-3.2.1.8, 5-3.2.3.2, 5-3.4.1.5, 5-3.4.1.6, 5-6.4, 7-2.7.2, and %2.7.3): Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators

I RECOMMENDATION: Chan~e the notes following Sections 5-3.2.1.8, 5-3.2.3.2, 5-3.4.1.5, 5-3.4.1.6, 5-6.4, 7-2.7.2, and 7-2.7.3 to Appendix A items corresponding to their respective sections. SUBSTANTIATION: These changes were for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in tee body of the standard. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMrVI'EE ACTION:


(Log #5) 8506- 30 - (5-3.2.2.1): Reject SUBMrrTER: Alfred W. Grusi, John Zink, a KOCH Industries Company RECOMMENDATION: Revise the last sentence as follows:

"Where full relievir~g capacity is not installed, a high supply gas oressure trip shall be included." SUBSTANI"IATION: This change would be consistent with NFPA 8502, 1995 Edition, ~';ection 6-3.1.2. However, a conflict may exist between this and the requirements of ANSI B31.1. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The proposed change is inconsistent with recognized piping codes. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CPI 3) 8506- 31 - (5-3.2.2.1): Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators RECOMMENDATION: 1. Delete the note following Section 5-3.2.2.1.

2. Revise the second sentence of Section 5-3.2.2.1 to read as follows:

"Where full relieving capacity, vented to a safe location is not installed, the piping system shall be designed, for the full su.pply pressure up to and including all individual burner and igmter safety shutoff valves." SUBSTANTIATION: These changes were for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. The intent of the note has been incorporated into the body of the text. COMMITTEE ACTION: Accept. NUMBER OF COMMITrEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #50) 8506- 32- (5-3.2.2.4): Accept SUBMITTER: Harold Honath, Coen Co., Inc.

I RECOMMENDATION: Add the words "augmented air supply (where provided)" to Section 5-3.2.2.4 after "...combustion turbine air intake,". SUBSTANTIATION: The augmented air supply is another avenue for discharges from atmospheric vents to inadvertently enter the HRSG. Duct burners with augmented air systems are common enough that material pertaining to it is worthy of inclusion in the main body of NFPA 8506. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #30) 8506- 33 - (5-3.2.2.4.1 Exception): Accept in Principle SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Revise text to read:

"Manifolding of all vents shall be permitted." Exception No 1: Burner vents shall not be manifolded with

igniter vents. Exception No 2: Header vents shall be manifolded only with

other header vents. Exception No. 3 through 6 in NFPA 8502 Section 6-3.1.9" Include

TANTIATION: Revision made in NFPA 8502-1995. Copy and revise accordingly. COMMITTEE ACTION: Accept in Principle.

1. Delete Sections 5-3.2.2.4.1, 5-3.2.2.4.2, and 5-3.2.2.4.3. 2. Add new Section 5-3.2.2.5 to read as follows: Manifolding of all vents shall be permitted. Exception No. 1: Burner vents shall not be manifolded with

igniter vents. Exception No. 2: Header vents shall be manifolded only with

other header vents. Exception No. 3: Vents of headers being served from different

pressure reducing stations shall not be manifolded. Exception No. 4: Vent systems of different HRSGs shall not be

manifolded. Exception No. 5: Vents of systems operating at different pressures

shall not be manifolded. Exception No. 6: Vents of systems using different fuel sources

shall not be manifolded. 3. Renumber existing Section 5-3.2.2.5 as 5-3.2.2.6. 4. Relocate the last sentence ofA-5.3.2.2.2 as a new Secdon A-

5.3.2.2.5 to read as follows: A-5-3.2.2.2 Where vents are manifolded from safety shutoff

systems, the cross-sectional area of the manifold pipe should be equal to, or greater than, the sum of the cross-sectional areas of the two largest vents involved. COMMITTEE STATEMENT: The changes to the submitter's

pposed text were for consistency with other NFPA standards A 8502). These changes satisfy the intent of the submitter.



(Log #54) 8506- 34 - (5.3.1.1(f) (New)): Accept SUBMITTER= Harold Honath, Goen Co., Inc. RECOMMENDATION: Add a new Section 5-3.1.1 (f) as follows:

(f) Augmented air supply. SUBSTANTIATION: Duct burners with augmented air systems are common enough that material pertaining to it is worthy of inclusion in the main body of NFPA 8506. COMMITTEE ACTION: AcceEt. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CP14) 8506- 35 - (5-3.3.7): Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators RECOMMENDATION: 1. Delete the Caution note following Section 5-3.3.7.

2. Revise Section 5-3.3.7 to read as follows: 5-3.3.7 Ignition devices shall be removable for maintenance while

the HRSG is in service. Precautions shall be taken for personnel protection when removing such parts during operation, as they will be hot and hot gases will exit the opening left by the removed part. SUBSTANTIATION: These changes were for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. The intent of the note has been incorporated into the body of the text. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


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(Log #CP15) 8506- 36 - (5-5.4 (New)): Accept SUBMITTER: Technical Commit tee on Heat Recovery Steam Generators

I RECOMMENDATION: Convert the CAUTION note following Section 5-5.3 into a new Section 5-5.4 as follows:

5-5.4 Precautions shall be taken when selecting a storage area for ammonia, as the pressure in storage vessels can rise significantly when exposed to elevated temperatures. SUBSTANTIATION: These changes were for compliance with the Manual o f Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. The intent of the note has been incorporated into the body of the text. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #31) 8506- 37- (6-2.2.1): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler

[ RECOMMENDATION: Replace "in not more than" with "within". SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #53) 8506- 38 - (6-3.2.1.10 (New)): Accept SUBMITTER: Harold Hona th , Coen Co., Inc. RECOMMENDATION: Add a new Section 6-3.2.1.10 as follows:

6-3.2.1.10 Loss of Augmented Air Supply. Consequently, change "6-3.2.1.9" to "6-3.2.1.10" in 6-3.2.1.

SUBSTANTIATION: Having loss of augmented air supply as a required alarm will alert operators to take steps to prevent ho t exhaust gases exiting the HRSG and enter ing operating personnel areas th rough the augmented air system. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #7) 8506- 39- (6-4.2.6 (New)): Reject SUBMITTER: Alfred W. Grusi, J o h n Zink, a KOCH Industries Company RECOMMENDATION: Add new text to read as follows:

6-4.2.6 Where the burner is designed to have a cross lighting burner e lement that will be fired continuously, two flame detectors shall be fitted, one at each end of the cross lighting burner element, ff the cross lighting burner e lement will not be fired continuously, then two flame detectors shall be fitted, one at each end of the cross lighting burner e lement and one flame detector on each of the remaining burner elements. SUBSTANTIATION: This addit ion supports the flame detect ion Section 6-4.2.1. "Each burner e lement or zone to be supervised individually." Such elements as pilot runners should require supervision along with the main elements of the burner. The pilot runner should no t be considered an igniter. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: This Proposal would make the standard design specific. The existing s tandard permits, and does not prohibi t these arrangements . NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #8) 8506- 40- (6-4.3): Reject SUBMITTER: AffredW. Grusi, J o h n Zink, a KOCH Industries Company RECOMMENDATION: Revise as follows:

6-4.3 Duct Burner Master Fuel Trip. A duct burner master fuel trip shall be initiated by the following conditions:

(a) Low fuel pressure; (b) Loss of all burner flame; (c) Partial loss of flame sufficient to introduce a hazardous

accumulat ion of unbu rned fuel; (d) Closing of last individual safety shutoff valve; (e) High fuel pressure, if a pressure above the operating limits of

the burner(s) can occur; (f) Loss of energy supply for burner managemen t or interlock

system; (g) Atomizing media supply pressure low; (h) Burner managemen t system malfunct ion detected; or any of the following additional balance of plant shutdown

conditions: (i) Combust ion turbine trip; (j) Total combustion turbine exhaust flow that drops below the

min imum required for safe operat ion of the duct burner as specified by the burner manufacturer or as proven by trial; it shall be permi t ted to infer this flow from the operating status of the combust ion turbine;

(k) Low water level on high pressure section of HRSG; or (1) Loss of energy supply fo rbo i l e r control.

SUBSTANTIATION: The separation o f the shutdown conditions that are specific to the duct burner equ ipment will allow for the local only resetting of the MFT relay on those conditions. Tbe operator needs to go to the local location, at the duct burner, inspect the equ ipment and de te rmine that is is in safe condition. While there he needs to reset the MFT relay and perform the first- t ime startup as required by Section 7-1.2(b).

The separation of the additional shutdown conditions, for the balance of the plant, will allow resetting of the MFT relay from either a local or remote location. The remote reset could be followed by a remote startup of the duct burner . COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Commit tee Action and Statement on Proposal 8506-62 (Log #6). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CP3) 8506- 41 - (6-4.3(1) (New)): Accept SUBMITTER: Technical Commit tee on Heat Recovery Steam Generators

I RECOMMENDATION: Add a new subsection to 6-4.3 as follows: "(1) Manual Trip, See 6-5.10."

SUBSTANTIATION: A manual trip is required in Section 6-5.10. The change was made for consistency and correlation. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #32) 8506- 42- (6-5.12.3): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Revise text as follows:

After "include" add "but shall no t be limited to ' . SUBSTANTIATION: To match 6-5.12.3 in NFPA 8502. COMMITTEE ACTION: Accept. COMMITTEE STATEMENT: The Commit tee understands that the reference in NFPA 8502 is actually Section 4-3.2.3.2 and the change is for correlation. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


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NFPA 8506 - - A98 ROP

(Log #33) 8506- 43 - (6-5.12.4 (New)): Reject SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Add new text as follows:

'q'he logic system shall be limited to one HRSG system only." SUBSTANTIATION: To match up with NFPA 8502 (4-3.2.3.3). COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Present technology safely permits this to be accomplished using a redundant DCS system. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #41) 8506- 44 - (Chapter 7 Tide): Accept in Principle SUBMITTER: Ralph Clemens, InterGen RECOMMENDATION: Revise fide of this Chapter to "Purge, Startup, Operation and Shutdown HRSG Systems Using Fuel or Fuel Oil". SUBSTANTIATION: Proposed wording is more descriptive of the actual material contained in this chapter and may eliminate confusion to an unfamiliar reader of the total context. COMMITTEE ACTION: Accept in Principle.

I Revise the submitter's proposed title of this Chapter to "Purge, I Startup, Operation and Shutdown of HRSG Systems U=!ng F'_'e! or i Fucl Oil". COMMITTEE STATEMENT: Changes were editorial and satisfy the submitter's intent. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #4) 8506- 45 - (7-1.2(b)): Reject SUBMITTER: Alfred W. Grusi, John Zink, a KOCH Industries Company RECOMMENDATION: Revise as follows:

"The start-up of the burner as a first time function, and after each duct burner master fuel trio. shall be accomplished by an operator at the burner location who-has a direct view of the burner." SUBSTANTIATION: The addition clarifies what a "first time function" is. The statement in the standard could mean the first time that the burner management system was put into operation, and never have any credence after. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Action and Statement on Proposal 8506-62 (Log #6). Additionally, "first time ~ refers to startup at commissioning or major alterations. NUMBER OF COMMrVrEE MEMBERSELIGIBLE TO VOTE: 23 VOTE ON COMMrITEE ACTION:


(Log #CP16) 8506- 46 - (7-4.1): Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators RECOMMENDATION: 1. Delete the note following Section 7-4.1.

2. Revise Section 7-4.1 to read as follows: 7-4.1" The purge of die combustion turbine shall be in

accordance with the manufacturer's instructions and the requirements of 7-4.2 and 7-4.3. A complete purge of the combustion turbine and applicable portions of the HRSG enclosure shall be accomplished before light-off of the combustion turbine.

A-%4.1 The objective of dais practice is to remove potential accumulations of hazardous unburned fuel from the volume defined in 7-4.2.1 that could be ignited by light-off of the combustion turbine. SUBSTANTIATION: These changes were for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. The intent of the note has been incorporated into the body of the standard or has been relocated to the ap!aendix. COMMITTEE ACTION: Accept.

NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: VOTE ON COMMITTEE ACTION:


23

(Log #47) 8506- 47 - (7-4.2 and 7-4.3): Accept in Principle in Part SUBMrlq'ER: Kris Gamble, Black & Veatch RECOMMENDATION: Delete Sections 7-4.2.2 and 7-4.2.5 and replace with the following:

7-4.2.2 The purge rate shall provide sufficient velocity within the connecting duct and HRSG enclosure to ensure sufficient dilution and removal of combustible gases prior to turbine light-off. The adequacy of this purge rate shall be demonstrated by one of the following methods:

(a) An engineering model of the system from the outlet of the turbine to the outlet of the HRSG shall be constructed andpurge adequacy shall be demonstrated with flow testing performedat the equivalent purge conditions. (b ) A similar HRSG combustion turbine system burning similar

fuel and with similar ductwork and stack geometry has previously been installed and has an extensive documented history of successful startups performed in accordance with the manufacturer's recommendations and without occurrences of uncontrolled combustion of fuel accumulations in the HRSG enclosure during turbine light-off.

(c) Provide combustible gas analyzers that would prevent startup of the combustion turbine if combustible gas concentrations greater than 75 percent of the Lower Explosive Limit exist in the HRSG. SUBSTANTIATION: 1. Historical records from the Edison Electric Institute, insurance companies, and the utility industry indicate no occurrence of a loss due to explosion caused by combustion of gaseous fuel accumulation in an HRSG enclosure when manufacturer's recommended stactup procedures are followed. Based on this extensive successful history, no mandatory increase in purge rates is warranted.

2. The addition of supplemental purge equipment can result in higher potential for ntis-operation and unsafe conditions due to leaking of ltigh temperature combustion products fi'om the purge air system to surrounding equipment or personnel. These alternatives should be considered only as a last resort if the turbine or HRSG and ductwork can't be modified to be adequately purged by the turbine starting system.

3. Physical flow modeling of HRSG's have demonstrated that purge rates from the combustion turbine starting system are sufficient for adequate purge of the HRSG. COMMITTEE ACTION: Accept in Principle in Part.

1. Modify Section 7-4.2.2 to read as follows: %4.2.2* The purge rate shall provide sufficient velocity within the

connecting duct and HRSG enclosure to ensure sufficient dilution and removal of combustible gases prior to turbine light-off. The adequacy of this purge rate shall be demonstrated by one of the following methods:

(a) during the purge of the combustion turbine, a flow rate of not less than 8 percent of full-load mass airflow shall be provided through the HRSG enclosure.

(b) an engineering model of the system from the outlet of the turbine to the outlet of the HRSG shall be created and purge adequacy shall be demonstrated with flow testing performed at the equivalent purge conditions.

(c) a similar HRSG combustion turbine system burning similar fuel and with similar ductwork and stack geometry has previously been installed and has an extensive documented history of successful startups performed in accordance with the manufacturer's recommendations and without occurrences of uncontrolled combustion of fuel accumulations in the HRSG enclosure during turbine light-off.

(d) provide combustible gas analyzers that would prevent starmp of the combustion turbine if combustible ga s concentrations greater than 25 percent of the Lower Explosive Limit exist in the HRSG."

2. Add a new Section A-%4.2.2 as follows: A-7-4.2.2 Purge Modeling. (a) An engineered model study has shown the capability of

accurately depicting the gas flow characteristics within an HRSG enclosure. The greatest experience base for model studies has

i been physical scale models utilizing a cold air flow. These models i are generally accurate if kinematic similitude is maintained by ensuring the test flow within the model is fully turbulent (Reynolds Number >3,200). The increasing availability of computational fluid

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I dynamics (CFD) programs offers an alternative to physical modeling. With any model study, the accuracy of the results are d e p e n d e n t on the skill of the modeller, the quality of the modell ing tools and the detail of the model.

Engineered model studies may be used to de termine purge effectiveness. For this use, the physical model generally offers the advantage of ease of visualization when identifying areas of high combustibles concentrations. It is difficult, however, to quantify purge efficiencies with a physical model . The CFD model , .when properly created, is able to define the change in concentrat ion of the combustibles, but in general, is less easily visualized. It is also recognized that it is possible to consolidate the results of many model studies to develop a calculative me thod of correlating HRSG configurations with specific purge rates.

(b) Physical or computational model ing or o ther engineer ing approaches can demonst ra te or define a specific purge rate (higher or lower than 7-4.2.2) for HRSGs. However, the parameters vary for each installation and are unique.

As a minimum, consideration should be given, but not be l imited to the following:

1. ductwork and stack geometry 2. HRSG geometry 3. Fuel characteristics (lower explosive limits, autoignit ion

temperature , density, etc.) 4. combust ion tu rb ine /HRSG condit ions (hot or cold) 5. fuel accumulat ion zones In general, when usingphysical or computat ional modeling, the

reproduct ion of areas where gas may accumulate is of extreme impor tance .

An example of this would be the steam drum and collection header cavities located on the top of HRSGs. These pockets can be very large and vary in size considerably depend ing on

i manufacturer and model . Low purge rates may no t be able to dissipate the f lammable vapors in these locations and could require separate venting or blowers to reduce the flammable vaI.13(ors.

(~aution: While not covered by this s tandard at the present time, in t e rconnec ted multiple combustion turbines and HRSGs are being installed and operated. These configurations require special purge considerations and may require purge rates significantly higher than required by this standard." COMMITTEESTATEMENT: 1. The new section reducing the flow rate to 8 percent min imum was added considering the following:

(a) flow models (b) a comparison with conventional boilers operat ing at 3

percent oxygen levels, versus HRSGs operat ing at approximately 15 percent oxygen levels,

(c) historical data indicating acceptable loss exper ience by operating at these reduced purge rates.

2. Section 7-4.2.3 was re ta ined because it is a viable alternative. 3. The 75 percen t LEL was changed to 25 percent LEL for

consistency with safe industry practices. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 18 NEGATIVE: 1 NOT RETURNED: 4 Garberry, Dunlap, Giansiracusa, Witt

EXPLANATION O17 NEGATIVE: LEFTON: A change f rom 15 percen t to 8 percen t min imum is a

large step. Historical data is based on 95-15percen t and poor records on small units. Newer units are larger and we should approach this step wise, eg. 15 percent to 10 percent at minimum. C. T. starting a n d C r a n k i n g motors can be sized to meet this requi rement .

COMMITTEE STATEMENT: Reject the main rule, because there is no technical substantiation to validate the p roposed change. Accept in Principle the p roposed Exception, see Committee Action and Statement on Proposal 8506-47 (Log #47). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 18 NEGATIVE: 1 NOT RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

EXPLANATION OF NEGATIVE: LEFTON: 8 percent min imum is too low (See my Explanation of

Negative on Proposal 8506-47 (Log #47).

(Log #3) 8506- 49 - (7-4.2.2): Accept in Principle in Part SUBMITTER: T.C. Clayton, Black & Veatch RECOMMENDATION: Revise text as follows:

7-4.2.2* During the purge of the combustion turbine (a) A mass flow rate of no t less than 15 percent of full load

airflow shall be provided th rough the HRSG enclosure. OR (b) An engineer ing evaluation shall be per formed to

demonstra te a reduct ion of vapor concenlxation below the lower explosive limits (LEL) of the fuel to be used.

A-7-4.2.2 Physical or computat ional model ing or o ther engineer ing approaches can demonst ra te or define a specific purge rate for HRSG's. However, the parameters wary for each installation and are unique.

As a minimum, consideration should be given to but no t limited to the following:

1. HRSG Geometry 2. Fuel characteristics (lower explosive limits, auto ignition

temperature , etc.) 3. Combustion turbine purge capability 4. Ductwork and Stack Geometry 5. Combustion t u rb ine /HRSG condit ions (hot or cold) In general when using physical or computational model ing the

reproduct ion of areas where gas may accumulate is of extreme impor tance .

An example of dais would be the steam d rum and collection header cavities located at the top of HRSGs. These pockets can be very large and vary in size considerably depending on manufacturer and model . Low purge rates may no t be able to dissipate the f lammable vapors in these areas and could require separate venting or blowers to reduce the f lammable vapors. SUBSTANTIATION: (a) The specified purge rates may be too low based on specific design and create ahaza rdous operating condit ion.

(b) The proposed wording including appendix material gives additional guidance to the eng inee r /des igne r to minimize operat ion under a potential hazardous condition.

(c) Clarification of paragraph 1-2.2. COMMITTEE ACTION: Accept in Principle in Part.

Reject p roposed Section 7-4.2.2(a). Accept the remainder of the Proposal in Principle. COMMITTEE STATEMENT: See Commit tee Action and Sta tement on Proposal 8506-47 (Log #47). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #34) 8506- 48 - (7-4.2.1): Accept in Principle in Part SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Revise test as follows:

"Purge prior to the light off of the combustion turbine shall be accomplished by at least ten volume changes and for a durat ion of no t less than 5 minutes.

Exception: If the combustion turbine starting motor or motor generator can supply a m in imum of 8 percen t of full-load mass airflow through the HRSG enclosure 5 volume changes for a durat ion of no t less than 5 rain is permit ted." SUBSTANTIATION: Based on recent model testing and loss history, the above purge is considered adequate to remove any residual fuel capable of causing a damaging explosion. COMMITTEE ACTION: Accept in Principle in Part.

(Log #35) 8506- 50 - (7-4.2.2): Reject SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Revise text as follows:

"The HRSG enclosure shall be purged using the flow rate capability of file combust ion turbine." SUBSTANTIATION: Based on lack of an indication of problems f rom inadequate purge in combined cycle systems in operation using a less restrictive purge condition. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The submit ter has no t provided sufficient technical substantiation to suppor t the proposed change. Also see Commit tee Action and Sta tement on Proposal 8506-47 (Log #47).

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(Log #44) 8506- 51 - (7-4.2.2): Reiect SUBMITTER: Gary N. Miller, Edison Electric Inst. RECOMMENDATION' , Revise 7-4.2.2 to read as follows:

"During the purge af the combus t ion tu rb ine and prior to any restart, either:

(a) A mass flow tale of no t less than 15 percent of full load air flow shall be provided t h rough the HRSG enclosure, for a t ime period equal to that recluiredto achieve 25 pe rcen t of the Lower Explosive Limit for the fuel used, plus 5 minutes .

(b) A mass flow pvrge rate less than 15 percen t of full air flow may be acceptable if the manufac ture r , supplier, or compe ten t eng ineer can demon~m~te effective removal of any gaseous or s u s p e n d e d combust ib les for a t ime per iod equal to tha t r equ i red to achieve 25 pe rcen t oF the Lower Explosive Limit for the fuel used,

~ lus 5 minutes . U B S T A N T I A T I O N : The p rob lem is to provide sufficient purge

air flow to remove ol di lute any gaseous or su spended combustibles . HILSC technology can provide various sizes a n d shapes , as opposed t,) convent ional s team genera tors which require l t igh tu rbu len t flow rates to adequate ly purge "dead" gas flow zones. HRSG's can be des igned to e l iminate these areas. No loss history for present ly opera t ing units exists which shows that t t igher flow rates are needed . COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The submi t te r has provided insuff icient technical substant ia t ion to suppor t the proposed change in purge requi rements . T he Technical Commi t tee has provided technical substant ia t ion to allow a decrease in the purge rates. See Commi t tee Action and S ta tement on Proposal 8506-47 (Log #47). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITrEE ACTION:


(Log #46) 8506- 52 - (7-4.2.2): Accept in Principle SUBMITTER: Rick R. Scbartel , PA Power & Light Co. RECOMMENDATION: Revise Section 7-4.9.2 to read as follows:

"The mass flow rate requi red for purg ing the hea t recovery s team genera to r to 25 percen t of the Lower F lammable Limit shall be d e t e r m i n e d by the manu fac t u r e r or o ther c o m p e t e n t engineer , based on fuel type and uni t configurat ion. Calculations d e m o n s t r a t i n g th i s capability shall be p repared a n d submi t t ed for approval.

Except ion 1. Except where a combust ib le gas detect ion system is provided in the un i t enclosure which demons t r a t e s tha t 25 pe r cen t of the Lower Flammable Limit for the fuel being used is no t present , and such demons t r a t ion is used as a permissive for uni t s tartup." SUBSTANTIATION: T he cur ren t language requires the same levels of purge for H~kSG's as for larger base load s team generators . However, the des ign of the HRSG may lend themselves to lower rates. T h e sugges ted wording is i n t ended to be more pe r fo rmance based a n d therefore easier for des igners to achieve in the mos t cost-effective manne r . COMMITTEE ACTION: Accept in Principle. COMMITTEE STATEMENT: See Commi t tee Action and S ta tement on Proposal 8506-47 (Log #47). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 19 N O T RETURNED: 4 Carberry, Dunlap, Giausiracusa, Witt

(Log #36) 8506- 53 - (7-4.2.3): Reject SUBMITTER: Peter B. Matthews, Har t ford Steam Boiler RECOMMENDATION: Delete text. S U B S T A N T I A T I O N : Not necessary if prior proposals are accepted. COMMITTEE ACTION: Reject.

COMMITTEE STATEMENT: The pr ior Proposals were n o t accepted. See Commi t t ee Action a n d S ta tement on Proposals 8506- 48 (Log#34) and 8506-50 (Log #35). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #45) 8506- 54 - (7-4.2.3): Reject SUBMITTER: Gary N. Miller, Edison Electric Inst. RECOMMENDATION: Delete Section 7-4.2.3 SUBSTANTIATION: The prob lem is to provide sufficient purge air flow to remove or dilute any gaseous or s u s p e n d e d combustibles. HRSG technology can provide various sizes an d shapes, as opposed to convent ional s team genera tors which require h igh tu rbu len t flow rates to adequately purge "dead" gas flow zones. HRSG's can be des igned to e l iminate these areas. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Commi t t ee Action and Sta tement on Proposal 8506-47 (Log #47). NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CP6) 8506- 55 - (%4.3 Note): Accept SUBMITTER: Technical Commi t t ee on Heat Recovery Steam Gen erators RECOMMENDATION: 1. Revise the Caut ion note following existing Section 7-4.3 to be a new section 7-4.3.1 and to read as follows:

7-4.3.1 Excessive retries shall be avoided. Where o p e r a t i n g exper ience indicates there are p rob lems in combus t ion turb ine light-off, the light-off a t tempts shall be t e rmina ted a n d the cause investigated a n d corrected.

2. R e n u m b e r subsequen t sections accordingly. 3. Revise the first Caut ion note following existing Section 7-4.3.3

to s t and as a new Section 7-4.3.5 to read as follows: 7-4.3.5 Stratification of gasses shall be considered where analyzing

for combust ibles . 4. Delete the second Caut ion note (Caut ion 2) following existing

Section 7-4.3.3. SUBSTANTIATION: The changes were made to comply with the Manual of Style. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #37) 8506- 56 - (7-4.3.3): Accept SUBMITTER: Peter B. Matthews, Har t ford S team Boiler

[ RECOMMENDATION: Delete last sen tence . S U B S T A N T I A T I O N : Too restrictive. We already state "...after proving tha t combust ibles have been removed". COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 19 N O T RETURNED: 4 Garberry, Dunlap, Giausiracusa, Witt

(Log #1) 8506- 57 - (%5): Accept in Part SUBMITTER: H a r o l d H o n a t h , Coen Co., Inc. RECOMMENDATION: Make Except ion s t a t emen t part of previous sentence , as shown below ( f rom last draf t before publ icat ion) , or, if tile Except ion mus t s tand out due to NFPA conventions, reword it as:

Exception: For duc t burne r s opera ted as a single unit , sequences of 7-5.4.2 un ique to mult iple bu rne r opera t ions shall no t apply.

7-5.4 A duc t bu rne r purge credit shall be m e t as long as the duc t bu rne r purge rate is ma in t a ined a n d all duc t bu rne r purge

2 1 9

N F P A 8 5 0 6 m A 9 8 R O P

requirements are satisfied. The duct burner shall be permit ted to be lit, or a normal shutdown made, as long as the purge credit is maintained. Failure of the duct burner purge rate to be maintained or loss of any duct burner purge requi rement shall require a repurge in accordance with 7-5.1 and 7-5.2.

7-5.5 Duct Burner. 7-5.5.1 Testing igniters for duct burners shall be conducted in

accordance with the following: (a) A comple te periodic operational test o f each igniter shall be

made. The frequency of testing depends on the design and operat ion history of each individual HRSG and ignition system. As a minimum, the test shall be made during every start-up following an overhaul or o ther significant maintenance.

NOTE: The importance of reliable igniters and ignition systems cannot be over stressed.

(b) Individual igniters or groups of igniters also shall be

~ ermitted to be tested while the unit is in service. Such tests shall e made with no main fuel present in the igniters' associated

burner . 7-5.5.2 Starting Sequence. 7-5.5.2.1" The operat ing sequences described in 7-5.5.2 assume

die use of multiple e lement duct burners opera ted independendy of each other. For installations with a duct burner (single e lement or multiple element) operated as a single unit, procedures similar to that outl ined in 7-5.5.2 shall be followed with the exception that sequences unique to multiple burner operat ions shall no t apply.

NOTE: For typical fuel supply systems for duct burners that operate as a single unit, see Figures A-%5.5.2.1(a), (b), (c), and (d) .

%5.5.2.2* These starting sequences shall be per formed in the following order consistent with the manufacturer 's instructions:

NOTE: The sequences are based on the typical fuel supply systems shown in Figures A-7-5.5.2.2(a), (b), (c), (d), (e), and (0.

(a) All duct burner main fuel safety shutoff valves shall be proven to be closed. Also, all duct burner igniter fuel safety shutoff valves shall be proven to be closed.

(b) The main fuel header and the igniter fuel header shall be pressurized up to the individual m a i n b u r n e r and igniter safety shutoff valves in accordance with established operat ing procedures.

(c) The first individual igniter safety shutoffvalve shall be opened, and the ignition t ransformer shall be energized. If flame on the first igniter is not established within 10 seconds, the individual igniter safety shutoff valve shall be closed. The cause of failure to ignite shall be de te rmined and corrected. With turbine exhaust flow maintained, repurge is no t necessary, but a waiting per iod of at least 1 minute shall elapse before a t tempting a retrial of this or any o ther igniter. SUBSTANTIATION: Exception s ta tement as publ ished contradicts the first sentence of %5.4.2.1.

Proposal makes the wording meet the intent of the Committee 's original text. COMMITTEE ACTION: Accept in Part.

I Accept only the proposed changes to the Exception as follows: Exception: For duct burners opera ted as a single unit, sequences

of 7-5.4.2 unique to multiple burner operations shall not apply. COMMITTEE STATEMENT: The remainder of the Proposal was rejected because it was no t in tended to be submit ted by the proposer. The change to only the exception meets the intent of the submitter. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #57) 8506- 58 - (7-5.3 (New)): Accept SUBMITTER: Harold Hona th , Coen Co., Inc. RECOMMENDATION: Add a new 7-5.3 after the note following 7- 5.2 as follows:

%5.3 Where augmented air firing is provided, the augmented air p lenum and associated ductwork shall be purged into the HRSG enclosure. This requ i rement is in addit ion to the requi rements of the duct burner purge (See 7-5.2).

Renumber the subse otu _uent.P aragraphs app ro p riately . SUBSTANTIATION: Havang the augmented air system purged ensures that no combustible mixtures are t rapped within. The augmented air system may be separated f rom the HRSG enclosure so that combustion turbine purge and or operat ion may no t be able to purge it, therefore the augmented air p lenum and any

associated ductwork should be purged pr ior to duct burner light off.

Duct burners with augmented air systems are common enough that material pertaining to it is worthy of inclusion in the main body of NFPA 8506. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATWE: 19 NOT RETURNED: 4 C, arberry, Dunlap, Giansiracusa, Witt

(Log #CP17) 8506- 59 - (%5.3 (New)): Accept SUBMITTER: Technical Commit tee on Heat Recovery Steam Generators RECOMMENDATION: 1. Convert the note following Section 7- 5.2 to become a new Section 7-5.3 to read as follows:

7-5.3 Purge prior to light-off of the combust ion turbine shall not be considered a duct burner purge unless the requirements of 7-5.1 and 7-5.2 have been satisfied.

2. Renumber subsequent sections accordingly. SUBSTANTIATION: These changes were for compliance with the Manual of Style, and NFPA Standards Council direction to eliminate notes in the body of the standard. The intent of the note has been incorporated into the body of the text. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #38) 8506- 60 - (7-5.4.1 (b)): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler

I RECOMMENDATION: Eliminate the word "also". SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CP7) 8506- 61 - (7-8.1): Accept SUBMITTER: Technical Commit tee on Heat Recovery Steam Generators RECOMMENDATION: In existing Section 7-8.1, change "...7-3(d) t h rough (j)..." to "...7-3(d) th rough (j) and (m)...". SUBSTANTIATION: The change corrects an editorial mistake made in the processing of the 1995 edit ion of the standard. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #6) 8506- 62- (%9.4): Reject SUBMITTER: AffredW. Grusi, J o h n Zink, a KOCH Industries Company RECOMMENDATION: Add the following new sentences to the end of 7-9.4:

"The master fuel trip relay shall be reset only f rom a control location local to file duct burner after a shutdown from a duct burner master fuel trip condition. Shutdowns f rom additional master fuel trip conditions may be reset ei ther f rom a local or remote location." SUBSTANTIATION: This addit ion assures that operat ing personnel are present at the duct burner , after a duct burner master fuel trip, to make sure that the duct burne r equ ipment is ready for lighting. Other balance of p lant shutdowns could be reset from a remote location. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The standard does no t presently require a local station for the duct burner . Existing Section %9.4

220

N F P A 8 5 0 6 1 A 9 8 R O P

requirements are sufficient because they require an investigation and correction of trip conditions prior to restart. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 2~ VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 18 NEGATIVE: 1 NOT RETURNED: 4 Carberry, Dunlap, Giansiracusa, Witt

EXPLANATION OF NEGATIVE: GRUSI: This Proposal was rejected stating that the present

standard does not require a local station for the duct burner. I would to get a better understanding of the requirement stated in

Section 7-1.2(b), which states: "The start-up of the burner as a first time function shall be

accomiglished by an operator at the burner location who has direct view o t the burner."

It would seem difficult for the operator, who is at the burner location, to start the burner without some local station and control capability. It is my understanding that this local operator, according to Section 7-1.2(b), is to perform the physical action of starting the burner aad witnessing that start-up. The physical action would require some sort of control.

I solicit the Commit.tee for guidance in my understanding of this section of the standald.

(Log #CP18) 8506- 63- (7-9.4): Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators

J RECOMMENDATION: In Section 7-9.4, change "unit" to "duct burner". SUBSTANTIATION: Change is for consistency with terminology used in the standard, and is more explicit as to the type of purge required. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMrITEE ACTION:


(Log #40) 8506- 64 - (Chapter 9 (New), Figure A-9-3.1, and C,-2, ): Accept SUBMITTER: Ralph Clemens, InterGen RECOMMENDATION: Add new Chapter 9 as follows: Chapter 9 Combustion Turbine Exhaust Bypass Systems for Unfired

HRSG's 9-1" General. Caution: There are several aspects of a gas bypass damper system

that raise serious issues of safety and property damage. 9-1.1 The requirements covered in Chapters 1 through 8 shall

apply to HRSG configurations unless amended or supplemented in the subsequent sections of this chapter.

9-1.2 The application of dampers, bypass stacks or other equipment to a HRSG system greatly adds to the complexity of the system. The system designer shall incorporate design features and safeguards for the increased hazards associated with the added equipment. 9-1.3 Theprinciples outlined in this standard shall be

incorporatedin HRSG configurations that do not fit the designs outlined in Figures A-9-3.1, C-1 and G-2 (NFPA please note change from Committee minntes). Additional safety considerations and requirements shall apply where these configurations are used.

9-1.4 The owner or the owner's designated representative shall consider implications of the following points in any application using dampers and the methods employed will address the following concerns:

(a) Due to the physical size, shape and mass, a damper cannot be assumed to reliably fully seal a gas flow path

(b) Due to leaking fuel supply system or false start, a possibility exists of having an explosive mixture in the HRSG enclosure on either side of a gas damper during shut down periods.

(c) Failure to adequately purge the explosive mixture prior to intentional or unintentionalintroduction of the hot combustion turbine gas could result in the (NFPA pleas note change from Committee minutes) ignition of the mixture. It is likely that even at full speed, no load, the combustion turbine exhaust temperatures are abo~e the auto-ignition temperatures for common combustion turbine and HRSG fuels.

(d) Modern combustion turbine exhaust temperatures are sufficient to ignite and sustain the basic iron fire (oxidation reaction).

(e) Systems utilizing two stacks (HRSG and Bypass), with or without dampers, can develop a reverse flow of fresh air through the HRSG. This reversal is induced by the high temperature gas flow up the bypass stack.

(f) Failure of damper operating mechanisms may allow instantaneous reversal of damper position (open to close and vice versa) due to aerodynamic effects. Sudden closure of an operating combustion turbine free exhaust path will result in extremely high transient duct internal pressures. These high pressures can cause distortion of the HRSG enclosure and rupture of the duct expansion joints.

9-2 Purge. 9-2.1 A purge of both the HRSG enclosure and the bypass system

shall be completed as required in Section 7-4 prior to admitting combustion turbine exhaust gas into the HRSG.

9-2.2 Following the purge as required in 9-2.1, it is permitted to interrupt the flow through the HRSG using the gas bypass stack. Combustion turbine exhaust flow is permitted to reenter the HRSG at a later time without repurging, provided the combustion turbine has been in continuous operation with no trips or misfires.

9-2.3 Where a positive means of HRSG isolation is continuously maintained, the combustion turbine shall be permitted to purge and operate with combustion turbine exhaust through the bypass stack.

Exception No.l: When the positive means of HRSG isolation is removed, a purge of the HKSG enclosure shall be performed as required by Section 9-2.1. After this purge, and interruption as allowed by Section 9-2.2 is again permitted.

Exception No 2: In the event that the positive means of HRSG isolation is disabled and the combustion turbine can continue to be operated with an exhaust temperature at least 100°F (56°C) lower than the auto ignition temperature of fuels designed for use in the specific combustion turbine, the combustion turbine exhaust gas at this lower temperature may be used to purge the HRSG.

9-3 Damper Requirements. 9-3.1" Figure A-9-3.1 shows separate dampers for isolating gas

flow to the HRSG and allowing gas flow to the bypass stack. The requirements of Section 9-3 shall apply regardless of physical hardware, i.e., single bladed diverting damper, two separate dampers (single or multi-blade) for isolation or bypass service or multiple dampers in series with seal air provision.

9-3.2 Damper System. 9-~.2.1 The gas bypass damper failure mode shall be determined

and the exposed system shall be capable of withstanding the resultant transient design pressure as defined in Section 5-4.2.

9-3.2.2 Where unburned fuels could bypass leaking dampers, a means shall be provided for recognizing leakage of combustion turbine exhaust gas past the closed damper and into the HRSG. Where leakage is detected, the HRSG shall be purged at a temperature at least 100°F below the auto ignition temperature of the fuel before allowing hot combustion turbine gasses to enter the HRSG enclosure. Alternatively, means shall be provided to prevent exhaust leakage into the HRSG enclosure.

9-3.2.3 A positive means of HRSG isolation shall be provided if either of the following operating conditions are encountered:

(a) Work within the HRSG enclosure is necessary while the combustion turbine is operated through the bypass stack, or

(b) HRSG is empty of water while the combustion turbine is operated through the bypass stack.

Exception: HRSG specifically designed to run dry using special materials, following the guidelines of the HRSG manufacturer.

9-3.2.4 A means of assuring that the HRSG enclosure is free of combustible materials or a means of purging the portion of the HRSG enclosure that is downstream of the positive means of HRSG isolation shall be provided and used to meet the requirements of Section 7-4.

9-3.2.5 Where tight shutoff dampers are utilized, a means to prevent combustible fuel accumulation upstream of the damper shall be provided.

9-3.2.6 During planned maintenance outages the owner/operator shall be responsible to ensure that the following is accomplished:

(a) The damper system inspected for tightness when the damper(s) is fully closed;

(b) The damper operating devices checked for proper operation and positioning; and

(c) Correct damper system positioning during purge, start-up, and shutdown verified by functional test.

9-3.3 Monitoring.

221

N F P A 8 5 0 6 - - A 9 8 R O P

9-3.3.1 In addit ion to the requirements in Section 6-2.3, the position of the bypass stack damper(s) shall be continuously moni tored.

9-3.3.2 In addit ion to the required alarms in Section 6-3.2, reverse flow through an HRSG (air flow from exhaust stack th rough HRSG to bypass stack) shall be alarmed if the bypass damper system can be mainta ined in an intermediate position.

9-3.4 Interlocks. 9-3.4.1 To satisfy the intent of the position of stack damper

starting permissive interlock [See 5-2.3.1(e)] the following conditions shall be met:

(a) the bypass damper proven open or, (b) both the HRSG isolation damper and the stack damper

proven open 9-3.4.2 To satisfy the intent of the position of stack damper

interlock (See 5-2.3.2) the following condit ions shall be met: (a) the stack damper proven not to be fully open or; (b) the HRSG isolation damper is proven no t to be fully open. Exception: Where the bypass damper is proven fully open. 9-3.4.3 The combustion turbine tr ipping requirements of Section

5-2.3.2 shall be followed unless the bypass damper is opened in a manne r that prevents unsafe pressurization of the combustion turbine exhaust plenum.

B. Delete exiting Appendix C-2 in its entirety and renumber subsequent Appendix C material.

C. Add new Figure A-9.3.1 to Appendix A as follows:

t ?M1 / taok °;2 'd3

turbine

DM.j Bypass damper DM 2 HRSG isolation

damper DM 3 Stack damper

Figure A-9.3.1 Combustion turbine and unfired HRSG with bypass stack.

SUBSTANTIATION: Damper systems for unfired HRSG's were not included in the body of the 1995 edition. After Committee study, the above changes are r e c o m m e n d e d to add emphasis in the mandatory section of this document . COMMITTEE ACTION: Accept.

Accept the Proposal with the following editorial changes: 1. In Exception No. 1 following proposed section 9-2.3, change

"...and interruption. . ." to "...an interruption.. .". Paragraph will now read:

Exception No.l: When the positive means of HRSG isolation is removed, a purge of the HRSG enclosure shall be pe r fo rmed as required by Section 9-2.1. After this purge, an interruption as allowed by Section 9-2.2 is again permitted.

2. In proposed Section 9-1.4, delete "and the methods employed will address the following concerns:" Paragraph will now read:

9-1.4 The owner or the owner's designated representative shall consider implications of the following points in any application using dampers.

3. In proposed Section 9-1.4(c), delete "(NFPA please note change from Committee minutes)". Also, delete the word "common" in the second sentence. Paragraph will now read:

(c) Failure to adequately purge the explosive mixture pl ior to intentional or un in ten t iona l in t roduc t ion of the hot combustion turbine gas conld result in the ignition of the mixture . It is likely that even at full speed, no load, the combustion turbine exhaust temperatures are above the auto-ignition temperatures for combust ion turbine and HRSG fuels.

4. In proposed Section 9-3.4.1, change "...5-2.3.1(e)] the..." to "...5-2.3.1(e)] ei ther of the...". Paragraph will now read:

9-3.4.1 To satisfy the in tent of the position of stack damper starting permissive interlock [See 5-2.3.1(e)] ei ther of the following condit ions shall be met:

5. In proposed Section 9-3.4.2, change "...5-2.3.2) the..." to "...5- 2.3.2) ei ther of the...". Paragraph will now read:

9-3.4.2 To satisfy the in tent of the position of stack damper interlock (See 5-2.3.2) ei ther of the following conditions shall be met: COMMITTEE STATEMENT: These changes are strictly editorial in nature. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


8506- 65 - (Figure A-3-1 (New)): Accept SUBMITTER: Peter B. Matthews, Hartford Steam Boiler RECOMMENDATION: Add a new Figure A-3-1:

(Log #11)

DM 1 Bypass damper DM 2 HRSG isolation

damper DM 3 Stack damper DM 4 Air inlet damper

"K DM4 DM1 I "

J I J ~ f

DM 2 DM 3

0o

Proposed terminology. Figure A-3.1

SUBSTANTIATION: To clarify the location and definitions for dampers used in text. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #51 ) 8506- 66 - (A-5-3.2.2.2): Accept SUBMITTER: Harold Hona th , Coen Co., Inc. RECOMMENDATION: Add a new second paragraph to A-5- 3.2.2.2 as follows:

"Special precautions should be taken to safely vent heavier than air gases." SUBSTANTIATION: Heavier than air gases can accumulate in low spaces unless proper precautions are taken. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #CP2) 8506- 67 - (Figure A-7-5.4.2.2(a)): Accept SUBMITTER: Technical Commit tee on Heat Recovery Steam Generators RECOMMENDATION: Swap the descriptions of items Q and R and add "for R" after the parenthetical expression in the R 1 descript ion in the legend o f Figure A-7-5.4.2.2(a).

2 2 2

N F P A 8 5 0 6 ~ A 9 8 R O P

C 4 Igniter header a lmo~nm¢ ~ent ~alve ((~otlonal) C s Igniter supply almOSp/rl~lc venl wlw E Ign=~er heade~ safety shutoff val~, F IQnl~+ luel control valve G (nd~du~ *gnder eafely shutoff v~lvS K Pressure l ehe l " ~

s©

Q H~Jh fuel prasstle interlock R Low luel p~essure interlock FIt Low luel p~e~aum ~lmloCk (atlerr~W k)callon for R) S Fuel pmSSLne 9eug e

Msnu~ shutoff valve

' I= Olhln Ii, ~gr=tBs

petm~en ly msteJled)

Figure A-7-5.4.2.2(a) Typical duct burner gas igniter system.

SUBSTANTIATION: Changes are for consistency with the schematic diagram and with other figures containing R l. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #2) 8506- 68 - (Figure A-7-5.4.2.2(b)): Accept SUBMITTER= Harold Honath, Coen Co., Inc. RECOMMENDATION: Correct spelling in legend of Item T; shutoff misspelled as "shutoof'. SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept.

To guton system It [ ~3 Fl~J~e A-7-6,4 2 2~e))

[3-

B M I ~ b~r,e~ ~ / ~ (lYpcal}

)_

o - rnm~ b = r ~ s

A Mare ~t rely t ~ l u H valve M Flow mmw B InClvldt J~t bum~l la f~ly ~tt Jlof I vsiv~ O ~ ~IG~81 hlgi~ lu~ p~8~tlle lll6¢hJck C1 M 81fl b*j n~f h1841d~f Ch~I~IE~ m imo~ ~SflC ¥~4 yalve (o~liOflSI) ~ Bcmer Imad~ ~W Iuel gnN,stle inl~kx:k D~* Main I~lnel hmdel s~vJolf m~de f¢ v~lva)ve R I ~ heedel *ow tu~ p~eu~Jfe interlock

MB~ fu~ eonl~i vaf~e {all=trim IOcallon fa R) 0~ M=~ tml bypass control valce (optloqal) S Fu~ I~eSeu~e ~tuge J Fuel pces~aJle mgulllle~ (optional) F Manual ~lhut oil valVe

(Log #CP1) 8506- 69 - (Figure A-7-5.4.2.2(e) and Figure A-7-5.4.2.2(f)): Accept SUBMITTER: Technical Committee on Heat Recovery Steam Generators, Hartford Steam Boiler RECOMMENDATION: Add the words "alternate location for R', after "R 1 Low fuel pressure interlock" in the legend of Figures A-7-5.4.2.2(e) and A-7-5.4.2.2(f):

o,i ~ l e u m -

©© 000-

A ~ ~ ,~ ~ulo~ v=,v. aa L~ temperature ~ ~l~i~ v~ l y a~m {op lq~ I~ ~t,~le~l~l)

Ms~Jelcontrcdvedve R 1 L ~ rued pr~sule ~*lod~ (alt~nale I (~et~ k~ R) D 1 M~m ~g=el bypess oordrol vaJv8 (l~(imll} S Fu~101~=le 0~g~

il C~;cula prig ~lve { o p i ~ i tot u tlll ml~d ~1) W S ~ v ~ r ~ valve M F~OW m~le~ Y CheOk valve O Cl~n~ ~ st mnna

~gure A-7-5.4.2.2(e) Typical mechanical atomizing main oil duct burner system.

, 0 -

II o I

BA yam =~=yl~ulo~ v=v.

Wlow mare Cam~mO v*hnl 1 ~ f~ ~1~ o~ o c ; ~ m m ~ m m

s

a w ~

Tt

R I L~ klg plmwm mlefccX O~[fc~m I~¢altcn ~" R) At

T W~ l l h t . *n v~**

M ~ t ~ ml~J m h I~iw s l ~ VIIVL &tael'a~t'c (lll~'~t~l t 0 T0 f ~ v q m 0

y c~¢,~ vev.

z

l~gure A-7-5.4.2.2(f) Typical steam or air atomizing main oil duct burner system.

SUBSTANTIATION: Changes are for consistency with figures A-7-5.4.2.2(a) and A-7-5.4.2.2(b). Without the proposed additional text, it appears that both R and R 1 are recommended. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


Figure A-7-5.4.2.2(b) Typical main gas duct burner system.



(Log #43) 8506- 70- (A-9-1 (New) and G-l): Accept SUBMITTER: Ralph Clemens, InterGen RECOMMENDATION: 1. Add a new paragraph A-9-1 as follows:

(a) The requirements in Chapters 1 through 8apply to other combustion turbine and HRSG configurations (see Figures C-1 and C-2) except as amended or supplemented in subsequent sections of this chapter. There are additional safety considerations and requirements that apply where these configurations are used.

NOTE: Chapters 1 through 8 of this standard have been written based on a directly coupled combustion turbine and HRSG either with or without duct burners. Combustion turbine exhaust is the

223

N F P A 8 5 0 6 w A 9 8 R O P

only source of heat to the HRSG where no duct burners are supplied and is theprincipal source of combustion air for the duct burners where the HRSG system is so equipped. [See Figures A-9-1 (a) and (b).]

(b) The Technical Committee on Heat Recovery Steam Generators considers the application of both gas bypass and supplemental firing systems on the same HRSG system to be of a particularly complex nature with significant safety issues. Although particular strategies have been postulated that may be satisfactory for a specific application, it is felt that such would be unworkable to define as a universal requirement that would be implied if dais were included in the main body of this standard. Accordingly, the material contained in Appendix (2-1 is included for advisory Pthurposes only until a consensus can be reached for inclusion in

e main body (mandatory sections) of this standard. (c) Similar concerns exist in the Technical Committee's

judgement regarding HRSG systems with fresh air firing capability. The material contained in Appendix C-2 on these systems is

! additionally included for advisory purposes only. ! 2.. Delete existing paragraph C-1 and renumber following Appendix Cparagraphs appropriately. SUBSTANTIATION: Proposed modification to Appendix C by Technical Committee members suggest need to bring this discussion into Appendix A to follow movement of existing Section (3-2 into Chapter 9. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #42) 8506- 71 - (Figure C-I (a) and C-1 (b), Figure A-9-1 (a) and (b)): Accept SUBMITTER: Ralph Clemens, InterGen RECOMMENDATION: 1. Delete existing Figures C-l(a) and C-1 (b)

2. Add new Figures A-9-1 (a) and A-9-1 (b) as shown below:

~ D~ ~tack turbine

(Log #55) 8506- 72 - (Figure G-3, Figure A-5-3.5 (New)): Accept SUBMITTER: Harold Honath, Coen Co., Inc.

I RECOMMENDATION: Move Figure C,-3 to now become Figure A-5-3.5. SUBSTANTIATION: Duct burners with augmented air systems are common enough that material pertaining to it is worthy of inclusion in the main body of NFPA 8506. ff the Committee agrees with dais task group, Section G-3 will be eliminated and the subject figure appropriately should be in Appendix A as Figure A-5-3.5. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #52) 8506- 73 - (C-3-1, 5-3.5 (New)): Accept SUBMITTER: Harold Honath, Coen Co., Inc. RECOMMENDATION: Move C-3.1 to new Section 5-3.5 and change it to the following:

5-3.5 Augmented Air. 5-3.5.1 Where provided, the fan(s) supplying augmented air to

the duct burners shall be operated in accordance with the instructions provided by the supplier of the augmented air system or organization having responsibility for the overall design.

5-3.5.2 Upon failure of the augmented air supply, means shall be provided to prevent hot gases from exiting the HRSG through the augmented air system. SUBSTANTIATION: New 5-3.5.1 was C-3.1, with the change that the responsibility for the instructions for operation of the augmented air fans is reassigned from the manufacturer to the supplier of the augmented air system or the organization having responsibility for the overall design. The fan manufacturer may not be aware of all the hazards specific to operation of the fans for augmented air supply to a duct burner in an HRSG. 5-3.5.2 is added to prevent the unsafe situation of hot exhaust gases exiting the HRSG and entering operating personnel areas.



DM 3 Stack damper Figure A-9-1(a) Combustion turbine with directly coupled unfired

HRSG.

n ~ , ]~Qtack r

Bur DM 3 turbine DM 3 Stack damper

Figure A-9-1(b) Combustion turbine and directly coupled HRSG with burners.

SUBSTANTIATION: Proposed modification to Appendix C by Technical Committee members render the intent of these figures relevant to Appendix A material versus Appendix C. COMMITTEE ACTION: Accept. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


(Log #48) 8506- 74- (C-3-2.1, 7-4.2.4 (New)): Accept SUBMITTER: Harold Honath, Coen Co., Inc. RECOMMENDATION: Move G-$.2.1 to a new paragraph 7-4.2.4 worded as follows:

7-4.2.4 Where augmented air firing is provided, a means shall be supplied for interlocking and purging the augmented air system,

~ rior to initiating and during the combustion turbine purge. UBSTANTIATION: Having file augmented air system purged

ensures that no combustible mixtures are trapped within. The augmented air system may be separated from the HRSG enclosure so that combustion turbine purge may not be able to purge it, therefore tile augmented air should be used to purge the augmented air system prior to the combustion turbine purge. With file augmented air on during the combustion turbine purge, no purge gases can back into or beyond the augmented air system and into file operating area.



224

N F P A 8 5 0 6 - - A 9 8 R O P

(Log #56) 8506- 75 - (C-3-2.2, 6.4.3(1) (New)): Accept SUBMITI'ER: Hmold Honath, Coen Co., Inc. RECOMMENDATION: Move C-3.2.2 to new Section 6-4.3(1) and revise it to the following and therefore delete heading C-3.2:

"(1 ) Loss of augmented air supply where the safe operation of the duct burner requires augmented air." SUBSTANTIATION: Duct burners with augmented air systems are common enough that material pertaining to it is word W of inclusion in the main body of NFPA 8506. COMMITTEE ACTION: Accept. NUMBER OF COMMrI'TEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:

AFFIRMATIVE: 19 NOT RETURNErD: 4 Carberry, Dunlap, Giansiracusa, Witt

(Log #9) 8506- 76 - (C-4): Accept in Principle SUBMITTER: S.H. Allen, Dow Chemical U.S.A RECOMMENDATION: 1. Delete Section C-4 in its entirety and renumber subsequent sections accordingly.

2. Proposed changes to Section C-1 as follows: C-1 Combustion Turbine and Fired HRSG with Bypass Stack.

(See Figure C-1.) **Existing Figure C-4 of NFPA 8506** G-l.1 General. CAUTION: There are several aspects of a gas bypass damper

system that raise serious issues of safety and property damage. C-l.l.1 The requirements covered in Chapters 1 through 8 apply

to all HRSG configurations unless amended or supplemented in the subsequent sections of this appendix.

G-l.l.2 The application of dampers, bypass stacks or other equipment to a HRSG system greatly adds to the complexity of the system. The system designer should incorporate design features and safeguards for the increased hazards associated with the added equipment.

G-l.l.3 The principles outlined in this standard should be incorporated in HRSG configurations that do not fit the designs oudined in Figures A-9-3.1, t2-1 and G-2 **existing Figures C-2, C-4 and C-5, respectively). Additional safety considerations and requirements apply where these configurations, are used. .

C-1.1.4 The owner or the owner's destgnated representative should consider implications of the following points in any application using d:mapers and the methods employed will address the following concerns:

(a) Due to the physical size, shape and mass, a damper cannot be assumed to reliably fully seal a gas flow path.

(b) Due to leaking fuel supply system or false start, a possibility exists of having an explosive mixture in the HRSG enclosure on either side of a gas damper during shut down periods.

(c) Failure to adequately purge the explosive mixture prior to intentional or unintentional introduction of the hot combustion turbine gas could r~ul t in the autoignition of the mixture. It is likely that even at full speed, no load, the combustion turbine exllaust temperatures are above the autoignition temperatures for common combustion turbine and HRSG fuels.

(d) Modern comlmstion turbine exhaust temperatures are sufficient to ignite and sustain the basic iron fire (oxidation reaction).

(e) Systems utilizing two stacks (HRSG and Bypass), with or without dampers, c~n develop a reverse flow of fresh air through the HRSG. This reversal is induced by the high temperature gas flow up the bypass stack.

(f) Failure of damper operating mechanisms may allow instantaneous reversal of damper position (open to close and vice versa) due to aerodynamic effects. Sudden closure of an operating combustion turbine free exhaust path will result in extremely high transient duct internal pressures. These high pressures can cause distortion of the HRSG enclosure and rupture of the duct expansion joints.

C-1.2 Purge. C-1.2.1 A purge of both the HRSG enclosure and the bypass

system should be completed as required in Section 7-4 prior to admitting combustion, turbine exhaust, gas. into the HR, SG.

C-1.2.2 Follovang a combustion turbine slmtdown, a combustion turbine purge should be completed as required in Section 7-4 prior to admitting combustion turbine exhaust gas into the HRSG.

C-1.2.3 Following the purge as required in C-1.2.1, interruption of the flow through the HRSG using the bypass damper should require a re-purge of the HRSG.

G-1.2.4 Where flesh air is maintained through the HRSG after proper purging, and the combustion turbine is purged and operated through the by-pass stack (DM1) it is permitted to transfer gas flow of the operating combustion turbine to the HRSG by means of damper positioning.

C-1.2.5 Where a positive means of HRSG isolation is continuously maintained, the combustion turbine may be permitted to purge and operate with combustion turbine exhaust through the bypass stack.

C-1.2.5.1 When the positive means of HRSG isolation is disabled or removed, a purge of the HRSG enclosure should be performed as required by Section C-1.2.1.

C-1.2.5.2 In the event that the positive means of HRSG isolation is disabled and the combustion turbine can continue to be operated with an exhaust temperature at least 100°F (56°C) lower than the autoignition temperature of fuels designed for use in the specific combustion turbine and HRSG, the combustion turbine exhanst gas at this lower temperature may be permitted to be used to purge the HRSG.

C-1.3 Figure G-1 shows separate devices for isolating gas flow to the HRSG and allowing gas flow to the bypass stack. The requirements of Section C-1 should apply regardless of physical hardware, i.e., single bladed directing damper, two separate dampers (single or multi-blade) for isolation or bypass service or multiple dampers in series with seal air provision.

C-1.4 In addition to file parameters in 6-2.3, combustion turbine exhaust flow through the HRSG should be continuously monitored.

C-1.5 In addition to the required alarms in 6-3.2, low flow and reverse flow through an HRSG (air flow from exhaust stack through HRSG tobypass stack) should be alarmed if the bypass damper system can be positioned in an intermediate position.

C-1.6 Interlocks. C-1.6.1 As a supplement to the combustion turbine starting

dPermissive interlock in 5-2.3.1 (e) [position of the stack closure amper (if provided)], the damper allowing gas flow into the

HRSG should additionally be proven open. C-1.6.2 As a supplement to the combustion turbine tripping

interlock in 5-2.3.2 [position of stack closure (if provided) not correct], it is permitted to position bypass damper to the open position as an alternative to tripping the combustion turbine.

C,-1.6.3 Wbere file HRSG system is not designed for maintaining the bypass damper is an intermediate position, in addition to the required interlocks in 6-4.3, a duct burner master fuel trip should be initiated if the bypass damper is not closed.

G-1.6.4 Where the HRSG system is designed for maintaining the bypass damper in an intermediate position, the interlock in C-1.6.3 is not recommended. However, the damper intermediate position should be interlocked or duct burner operation should be interlocked with turbine exhaust gas flow through the duct burners.

C-1.6.5 Where it is desired to bypass the HRSG for a period of time, and then return tile HRSG to service without a power interruption, then a continuous flow of at least purge rate of exhaust or fresh air should be maintained through the HRSG whenever the combustion turbine is operating. This is intended to purge any inadvertent fuel accumulation in the HRSG.

Note 1. Depending on the dew point of the exhaust gasses it may be necessary to evaluate the effects of corrosion, and consider the use of corrosion resistant materials.

Note 2. It may also be necessary to take special precautions to protect the superheater or other circuits from excessive temperatures or pressures by allowing any steam that may be generated to be vented off and to make arrangements to replenish this vented steam.

C-1.6.6 An acceptable means to accomplish a duct burner purge is to reduce load on the combustion turbine so that the exhaust temperature is at least 100°F below the lowest autoignition temperature of any fuel being used in the HRSG system.

C-1.6.7 For maintenancepurposes, the combustion turbine may be permitted to be operatedwithout the minimum flow recommended in C-1.6.5 where a positive means of HRSG isolation is installed. Where removal of the positive means of HRSG isolation necessitates a combustion turbine shutdown and a combustion turbine purge per C-1.2.1, prior to admitting combustion turbine exhaust into the HRSG. Where removal of file positive means of HRSG isolation does not necessitate a combustion turbine shutdown, a HRSG purge per C-1.6.6 is recommended.

C-1.7 Where HRSG isolation dampers or diverter dampers are utilized, minimal exhaust gas leakage is permitted.

Note 1. Where leakage is suspected, care should be taken to maintain water supply to the HRSG to maintain tube cooling and prevent fin metal fires. Where water cannot be maintained for

225

N F P A 8 5 0 6 1 A 9 8 R O P

sufficient cooling, the corrlbustion tu rb ine should be removed f rom service.

Note 2. The change to HRSG isolation may be permi t ted to be delayed du r ing scavenge of oil bu rne r e lements .

C-1.8 W h e n the positive m e a n s of HRSG isolation has been installed, all fuel sources to the duc t bu rne r shou ld be isolated, e i ther via manua l valves or removable pipe spools.

C-1.9 Combus t ion tu rb ine operat ion may be permi t ted to be con t inued with exhaus t flow t h r o u g h the bypass duct.

G-I.10 Prior to re- int roduct ion of full exhaus t flow to the HRSG enclosure, it shou ld be purged with e i ther fresh air in accordance with Section 7-5 or with combus t ion turb ine exhaus t at a t empera tu re at least 100°F (56°C) below the autoigni t ion of any fuel that migh t be present.

G-1.11 Following re- in t roduct ion of full exhaus t flow t h r o u g h the HRSG, the isolation of the fuel sources to the duc t bu rne r s may be permi t ted to be removed and they may be permi t ted to be restar ted in accordance with Section 7-5.4.2.

3. Add new Figure C-1 as follows:

A Bypass stack ~ Stack H RSG

Burners Combustion turbine

Figure C-1 Combustion turbine and fired HRSG with bypass stack.

SUBSTANTIATION: Existing material u n d e r G-4 is incomple te and misleading. The material was developed to upgrade the existing C,4 to a more in dep t h and useful documen t . COMMITTEE ACTION: Accept in Principle.

1. In p roposed Section C,1.1.4, delete the words "and the m e t h o d s employed will address the following concerns ." Paragraph will now read:

Crl . l .4 The owner or the owner 's des igna ted representat ive shou ld consider implicat ions of the following points in any appl icat ion us ing dampers .

2. In p r o p o s e d Section C-1.1.4(c), delete the word "common" . Paragraph will now read:

(c) Failure to adequate ly purge the explosive mix ture pr ior to in tent ional or un in t en t iona l in t roduct ion of the h o t combus t ion tu rb ine gas could result in the autoigni t ion of the mixture. It is likely tha t even at full speed, no load, the combus t ion tu rb ine exhaus t t empera tu res are above the auto igni t ion t empera tu res for combus t ion tu rb ine a n d HRSG fuels.

3. In p roposed Section C-1.6.7, change ". . .shutdown a n d a combus t ion tu rb ine pu rge pe r C-1.2.1 . . . . " to ". . .shutdown, a combus t ion tu rb ine purge per C-1.2,1 is needed. . ." . Paragraph will now read:

C-1.6.7 For m a i n t e n a n c e p u r p o s e s , the combus t ion tu rb ine may be permi t ted to be o p e r a t e d w i t h o u t the m i n i m u m flow r e c o m m e n d e d in C,1.6.5 where a positive m e a n s of HRSG isolation is installed. W h e r e removal of the positive m e a n s of HRSG isolation necessi ta tes a combus t ion tu rb ine shu tdown, a combus t ion tu rb ine purge per G-1..2 1 is n e e d e d prior to admi t t ing combus t ion turb ine exhaus t into the HRSG. W here removal of the positive m e a n s of HRSG isolation does no t necessi tate a combus t ion tu rb ine shu tdown, a HRSG purge per C-l.fi.6 is r e c o m m e n d e d . COMMITTEE STATEMENT: Changes are editorial only for clarity. Additionally, it is u n d e r s t o o d tha t the parenthet ica l re ference to exist ing f igures C-2, 0 4 a n d C-5 in p roposed Section C-1.1.3 is for clarity a n d will no t be part of the new text. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON C O M M I T T E E ACTION:


(Log #39) 8506- 77 - (C-5): Accept in Principle SUBMITTER: Martin C. Nygard, Noo te r /Er iksen RECOMMENDATION: Revise Section C-5 to G-2 with text an d f igure as follows:

C-2 Combus t ion Turb ine and HRSG with Fresh Air Firing Capability. (See Figure C-2)

Note 1 N°ie i ~

Burner

Note 1: The fresh air inlet portion may include but is not limited to a bypass damper, an HRSG isolation damper, an air inlet damper, or a forced draft fresh air fan.

Note 2: The outlet duct may include but is not limited to an induced draft fan, an HRSGisolation damper, or a stack damper.

Figure C-2 Combustion turbine and HRSG with fresh air firing capability.

Note 1. The fresh air inlet por t ion may include bu t is no t l imited to a bypass damper , an HRSG isolation damper , an air inlet d a m p e r or a forced draft f resh air fan.

Note 2. The outlet duc t may include but is no t l imited to an induced draft fan, an HRSG isolation d a m p e r or a stack damper .

C-2.1 Opera t ing Configurat ions. C-2.1.1 Opera t ion o f an HP~SG system in the fresh air firing m o d e

may be pe r fo rmed by a variety of e q u i p m e n t configurations. Generally, amb ien t air (with of wi thout preheat ing) enters the HRSG enclosure ups t r eam of the duc t burner . This flow is genera ted ei ther t h rough a forced draft fan or an induced draft fan and may be of a different mass or vo lume flow than the normal HRSG system opera t ing flow. Dur ing this operat ion, bypass or isolation damper s are used to reconf igure the HRSG flow path to accommoda te the change f rom turb ine exhaus t to f resh air.

C-2.1.2 Operat ional Considerat ions. Because of the lack of s tandardizat ion of f resh air f ir ing configurat ion, and because of the potential for injury if the system malfunct ions , it is impor tan t that each system's operat ional modes of failure be analyzed in addit ion to the r equ i r emen t s of Section 9-1.4. Where the fresh air conf igura t ion has been def ined, each system opera t ing m o d e shou ld be evaluated to ensure safe operat ion. It is especially impor t an t to closely analyze the opera t ion du r ing t ransfer f rom combus t ion tu rb ine to f resh air f ir ing m o d e or f rom fresh air firing m o d e to combus t ion turb ine mode .

C-2.1.3 For fresh air firing, the owner or the owner 's des ignated representat ive shou ld consider the following operat ional modes:

(a) Opera t ion of the HRSG system with the combus t ion turb ine in operat ion. The duc t b u r n e r m igh t or m igh t no t be firing.

(b) Opera t ion of the HRSG system in the f resh air f ir ing mode. The duc t bu rne r will be in operat ion. T h e system shou ld be reviewed to conf i rm tha t any applicable por t ions of NFPA 8501 or NFPA 8502 are satisfied.

(c) Opera t ion with the combus t ion tu rb ine exhaus t ing t h ro u g h a bypass stack with the HRSG opera t ing in the f resh air f ir ing mode. The system shou ld be reviewed to conf i rm tha t any applicable por t ions of NFPA 8501 or NFPA 8502 are satisfied.

Caution: Fresh air f ir ing shou ld no t be combined with operat ion on combus t ion tu rb ine exhaus t except du r ing per iods of transi t ion between modes . The t ransi t ion per iod between modes m u s t be carefully evaluated to cons ider all potential hazards to safe opera t ion a n d the system des igner shou ld incorpora te design features and safeguards against the increased hazards.

C-2.2 Purge Requi rements . C-2.2.1 Dur ing system star tup with combus t ion tu rb ine

operat ion, pu rge shou ld be in accordance with the r equ i rements of Section 7-4 and 7-5. E q u i p m e n t used solely for the fresh air firing mode shou ld be secured a n d a m e a n s of assur ing the air p l en u m s a n d associated ductwork are f ree of combust ib le mixtures or a m e a n s of pu rg ing this ductwork into the HRSG enclosure should be provided.

C-2.2.2 Dur ing system star tup to fresh air f ir ing mode , purge shou ld be in accordance with the r equ i rements o f Section 7-5 or 25 pe rcen t of the full load fresh air mass flow, whichever is greater. The combus t ion tu rb ine shou ld be isolated to prevent reverse flow

2 2 6

N F P A 8 5 0 6 1 A 9 8 R O P

and ensure full p m g e . A means of assur ing the combus t ion turb ine ductwork is free of combust ib le mix tures should be provided.

C-2.2.3 Dur ing t ransfer f rom combus t ion turb ine operat ion to the fresh air firing ,mode, the purge shou l d be ma in ta ined as long as tile flow rate t h rough file enclosure is at or above purge rate.

C-2.2.4 Dur ing transfer f rom the fresh air f ir ing m o d e to combus t ion operat ion, the combus t ion tu rb ine pu rge shou ld be in accordance with Section 7-4. The combus t ion tu rb ine pu rge flow may be di rected t h r o u g h the HRSG enclosure or a bypass stack.

C-2.3 Controls, Moni tor ing, Alarms and Interlocks. C-2.3.1 In addi t ion to the r equ i r emen t s of Section 6-2, the

c o m b u s t i o n / t u r b i n e exhaus t flow or air flow t h r o u g h the HRSG enclosure shou ld be cont inuous ly r ecorded a n d t rended.

C-2.3.2 In addi t ion to tile r equ i rements of Section 6-3, reverse combus t ion turbine exhaus t flow or air flow t h r o u g h the HRSG enclosure shou ld be a larmed.

C-2.3.3 In addi t ion to tile r equ i rements of Sections 5-2 and 6-4, the following shou ld be interlocked:

(a) Imprope r d m n p e r posi t ion (b) Fresh air fan no t opera t ing C-Z3.4 A combus t ion tu rb ine trip should cause a Master Fuel

Tr ip (MFT) unless flow t h r o u g h tile HRSG enclosure can be ma in t a ined at or above the purge rate. Considera t ion should be given to reduc ing the duc t bu rne r f ir ing rate to a p r ede t e rmined m i n i m u m .

C-2.3.5 The m i n i m u m airflow when opera t ing in fresh air f ir ing mode is the purge Ilow rate (25 percent ; See C~2.2.2). A MF]" shou ld occur if fresh air flow falls below 20 percent . SUBSTANTIATION: The existing section too narrowly addressed a very complex opera t ing scenario. T h e sect ion has been rewritten to include mos t of the current ly opera t ing or p roposed fresh air f ir ing configurat ions.

COMMITTEE ACTION: Accept in Principle. 1. In p roposed Section C-2.1.2, change " . . .combust ion turbine to

fresh air f ir ing m o d e or from..." to " . . .combust ion tu rb ine opera t ion to fresh air to f ir ing m o d e a n d from...". Paragraph will now read:

G-2.1.2 Operat ional Gonsiderat ions. Because of file lack of s tandardizat ion of f resh air f ir ing configurat ion, and because of tile potential for, injury if . . . . . the system malfunct ions , it is impor tan t tha t each system s operat ional modes of failure be analyzed m addi t ion to the r equ i r emen t s of Section 9-1.4. Where the f resh air conf igura t ion has been def ined, each system opera t ing m o d e shou ld be evaluated to ensure safe operat ion. It is especially impor t an t to closely analyze the opera t ion du r ing t ransfer f rom combus t ion turbine opera t ion to fresh air to fir ing m o d e a n d f rom fresh air f ir ing m o d e to combus t ion turb ine mode .

2. In p roposed sect ion C-2.2.4, change " . . .combust ion operation. . ." to " . . .combust ion turb ine operation.. ." . Paragraph will now read:

C-2.2.4 Dur ing transfer f rom the fresh air f ir ing m o d e to combus t ion turb ine operat ion, the combus t ion tu rb ine pu rge shou ld be in accordance with Section 7-4. T h e combus t ion tu rb ine purge flow may be directed t h r o u g h the HRSG enclosure or a bypass stack.

3. In p roposed Section C-2.3.1, change " . . . combus t ion / tu rb ine . . . " to " . . . combust ion turbine.. .". Also, change " . . .continuously r ecorded a n d t rended ." to " . . .monitored.". Paragraph will now read:

C-2.3.1 In addi t ion to the r equ i r emen t s of Section 6-2, the combus t ion turb ine exhaus t flow or air flow th rough the HRSG ;nclosure shou ld be moni tored . 4. Change p roposed Section G2.3.5 to read as follows: C-2.3.5 The system should be reviewed to conf i rm tha t may

~,l~licable por t ions o f NFPA 8501 or NFPA 8502 are satisfied. .OMMITTEE STATEMENT: Changes were for clarity, a n d

consistency. NUMBER OF COMMITTEE MEMBERS ELIGIBLE TO VOTE: 23 VOTE ON COMMITTEE ACTION:


2 2 7

noncoring secrey...recommendation: revise the foreword as follows: foreword. this document is...

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