k D-R16B 927 RLTERII*TIVE RFFF (ROIJOUS FILM FORMING FORM) /PROPORTIONING SYSTEMS FOR THE SSN 21 DESIGN -T&E(u)

I NAVAL RESEARCH LRB MASHINOTOK DC F U MILLIANS ET AL.I UNCLASSIFIED_ 62 JUN 86 NRL-KR-5770 FIG 13/12 Mmhh77_hhi

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Naval Research LaboratoryWashington, DC 20375-5000 NRL Memorandum Report 5778 June 2, 1986

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00 Alternative AFFF Proportioning Systemsfor the SSN 21 Design-T&E

I F. W. WILLIAMSC) Combustion and Fuels Branch

Chemistry Division

R. C. BELLER, R. E. BURNS AND J. L. SCH4EFFEY

Hughes Associates, Inc.

Wheaton, MD 20902

j d

Approved for pubi~c release; distribution unlimited.

SECURITY CLASSIFICATION OF THIS PAGE

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2b. DECLASSIFICATION, DOWNGRAING SCHEDULE Approved for public release; distribution unlimited.

4 PERFORMING ORGANIZATION REPORT NUMBER(S) 5 MONITORING ORGANIZATION REPORT NUMBER(S)

NRI. Memorandumn Report 5778

68 AEO EFRIGOGAIAIN 6 FIESMO 74. NAME Of MONITORING ORGANIZATION(if applicable)

Navl esarh LboatryCode 6180S6f ADDRESS (City, Stitt, and ZIP Code) 7b. ADDRESS (City, State, and ZIP Code)

Washington. D)C 20375-5000

8.NMOFFUNDING I SPONSORING Sb. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBERORGANIZATION O~f dpplKable)

Naal aStm s Command 0511265 R 2St. ADDRESS (City, State, and ZIP Code) 10 SOURCE OF FUNDING NUMBERS

PROGRAM PROJECT TASK WORK UNITWashinlgrton, DC 20360 ELEMENT NO NO NO ACCESSION NO

___________________________________ 63561 >0364-SL 20 A000 )N880-17111 TITLE (Include Socurrty Casification)

Alternative AFTF Proportioning Systems for the SS'21 Design - T&E

• o.

12 PERSONAL AUTHOR(S)Williams, F. W., Beller, It. C.,* Burns, R. E.* and Scheffe-, J. L.*

13. TYPE OF REPORT 13b TIME COVERED 14 DATE OF REPORT (Year, Month, Day) 5 PAGE COUNT -Interim FROM 10,85 TO 1/86 1986 June 2 21

16 SUPPLEMENTARY NOTATION*l1ugles Associ;aes. Inc.. Wheaton, MD 20902

1I COSATI CODES 1S SUBJECT TERMS (Continue on reverse if necessary and identily by block number)FIELD jEGROUP SUB-GROUP Fire fighting Fixed systems

19 ABSTRACT (Continue on reverse if necenary and identify by block number)

The .. (IOU-MIS Film P'ornilg )-oam lAFFF) fire supp)ression systems proposed for flammable liquid fuel hazards onthe SSN 21 r-li(rv prlopir? ionilng systems to inject T;~ AFFF concentrate into seawater systems to create AFFF solu-tion. . Altvrnawi% proii)ort iinig systems each of which utilizes an air-pressurized concentrate storage tank are beingevaluiatedl by the Naval Iiewarch Laboratory (NRL I. One candidate system uses multiple single-user injection points(e.g., OrIf ,ITIO I oN 0to proportion AApr at each hose station or sprinkler system. The other system, whichuses an in-hO.' oahIIIct~l pr-essure proplirt joner and ratio controller, is designed as a central system which can proportionover a rang"-

Vrt~portwn Iihl .~~us the orifice plate system is pressure sensitive and not flow sensitive. As pressure differentialletwec, ti-. ,~- "m vntnwtot and se-w\aler increases, flow rate increases. If the pressure differential can vary consid-

eralIly during )I wrat o n,\l A F flo)w and storage roquiremients must be overdesigned to meet the lowest design point, --I.e., :J ,It th( nriali- pressrc differential. The size of the orifice in the orifice plate design may he so small (e.g., 0.1in. (111. I that 'i ~iTiig of tihe orifice could he a probflem.

(Continues)

20 DiSTRITION /AVAILABILITY OF ABSTRACT 2 ABSTRACT SECURITY CLASSIFICATIONM)UNCLASSIFiEDIJNILMITED 0 SAME AS RPT ODTIC USERS UNC'LA.SSIFIED)

22. NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (include Area Code) 22c OFFICE SYMBOLF. W. Wiliams l202) 767-2476 (Code 6180DO FORM 1473, a4 MAR n3 APR edition may be used untCl exhausted SECURITY CLASSIFICATION OF THIS PAGE

All other editions are obsolete

I -'. -:

.............................................-.--...- * ... *".1%

0ECUFNITY CLAUWP1CAYI" OF ml.8 PA"

19. ABSTRACT (Continued)

Proportioning using the balancing valve system is flow sensitive. A steady level of % concentrate is maintained overa range of flows. The use of a central proportioning system creates, in effect, a separate AFFF fireinain system. Thecentral proportioning system allows more effective use of AFFF concentrate, but significant design and operationalproblems result from the requirement to have seawater only capability at AFFF hose stations.

Future R&D work will focus c n the single-user injection point system. Two additional single-user injection point -systems may be available for testing in the near future.

U IMCUOPAtY CLANIVICATION OF THIS5 PAGE

-T-I . 0.- 7.0--

CONTENTS

1. INTRODUCTION.............................................1

II. TECHNICAL DESCRIPTION .................................... 1

A. General.............................................. 1B. Orifice Plate System............. .......** ....... ... 4C. In-Line Balanced Pressure Proportioner...................... 4

III. TEST RESULTS ............................................

A. Orifice Plate System . . . . . . . . . . . . . . . . .B. In-line Balanced Pressure Proportioner...................... 11C. Evaluation of Proportioning Systems....................... 11

IV. ALTERNATIVE SYSTEMS.................................... 15

V. SUMMARY ................................................. 15

"I A c A

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ALTERNAT IVE AFFFPROPORTIONING SYSTEMS FOR THE SSN 21 DESIGN -T&E

-. INTRODUCTION

The Aqueous Film Formning Foam (AFFI) 'ire sucpression*svstems Drocosed for flammable liquid fuel hazards on the SSN

2 1 (including the diesel auxiliary generator space, lube oilbay bilge and aft hydraulic plant) require pr-oortioningsystems to inject 3% AzFF F concentrate into seawater systems tocreate AF -FF solution at sprinkler systems and hose stations.Alternative proportioning systems which utilize anair-oressurized concentrate storage tank are being evaluated.Cne candidate proportionfing system uses orifice metering plates

*to crooortion AFFF at each seawater injection point (i.e.,sprinkle r system or hose station.) An alternative system uses

* ~an in-line balanced oressure proportioner and rati otrleo proportzion AFFF over a range of system demands.

'he objective of this report is to provide an interim*analvsis of the alternative oroportioning systems, bCased on a

review of the proosed designs and results of conceotualtesting of the systems.

* :.TECl-ICAL DESCRIPTION

A. General

As now envisioned, the AFFF firefighting systems will besuzolied from the on-board seawater flushing system. This is a

*new ccnceot comzared to the SSN 688 class design, whereseawater fre- hnose stations are supplied directly from the t rim

* discharge header. AFFF concentrate storage tanks, locatedforward; and aft of the reactor comnartment, will be oressurizedrom available service air systems to inject AF-'"?: concentrateLnto brancn, Lnes serv;:na AF-71 scrinklers and nose s~ia:.ns.

_ s an:::z;:a~ed t'-a:: each -oncentrat:e :an. -d 1 e=ressur::zed at 3.79 ~gc 2 (125 p:si), wnlch, will eliminate th

* need for concentrate oumos t:oicallvi found in sur-face sh-io ATAP 4oes",ons. A schematic of tne proposed system, develcoed b

'MA7SZA 56Y_"2, ._s shown in Tic. 1. Conceptual schematics of the*~candoidate orooortionina s';stems are sh~cwn in Flz. 2.

Manuscript approved February '26. 986

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It is currently estimated that each concentrate tank will besized for 5 minutes of agent applcation when the largestsprinkler system and two 3.31 cm (1-1/2 in.) handlines areopceratiLng simultaneously. Tentativ.e criteria 'lave beenestablished to provide AFFF hose stations so that any point canbe reached from at least two hose stations with 15.24 m (50ft.) of hose.

The seawater service pressure, supplied from either theflushing water or trim discharge header, has not beenfinalized, and it is not known whether this pressure will berelatively constant (e.g., 3.52 kg/cm 2 (50 psi) from theflushing water system) or variable as is the case in the SSN

* 688 desian where trim discharge pressure is increased (through" air pressurization or pump activation) in the event of a fire.

Testing has assumed a variable seawater service oressure at theS.?? in: ection point of 2.11-7.03 k 1/cm2 (30-100 psi), and aconcentrate injection of 8.79 kg/cm2 (125 psi).

NAVSEA has established two criteria which are important inthe overall conceotual development of the proportioning system:A? F? hcse stations must have seawater-only capability at anygiven time; and, AFFF may not be introduced into the primarytrim discharge or flushing water lines.

B. Orifice Plate System

The orfi4ce. metering plate system uses a single-userinjection toint method of procortioning AFF?. An AF?-.concentrate ine from the concentrate tank would supply AFFF toan orifice olate at each hose station or sprinkler system. Theorifice ciameter of each plate would be sized for 3% AFFproportloning, based on the oressure differential between theconcentrate line pressure and seawater firemain pressure at thein-ecticn points, and flow demand of the nozzle or sprinklers.

C. In-line Balanced Pressure Proportioner

The in-line balanced oressure orooortioner system is acentral orcccrtioning system with a single concentrate1n-ection zcnt, based on the same concepts which apply to thebalanced pressure orcoortioner currently soecified for surfaces,.:os. A regulating valve is located in the concentrate suoolvIine. ilot lines connected to the upstream side cf theseawae! - suto; and aownstream s Ie of the concentrate suc'vznrott e ccen or clcse) the _au~aong ahraom tcr..

'a. net cressures at the i-ect-on o..nt. A ra:ctontrol-e wl:h an internal 7orifce olate s:eo for A 7croccrtonnc -n s installed at the in-ection point andcrccrticns tne AFFF at 3% over a range of flows. nlike thes-r:ace sn in caancea oressure zrooortioner, the in-!inezalancez cressure orzzortoner aces not nave a concentrate__trn _-- -acLz to tne tan . The throttlang :alve opens asiemanL nzcreases and closes as Jemand decreases; the ocositens true "n the surface sniz balanced pressure orccort~cnlncsystem iner-? regulating valve -s _ccated _n the 7oncentrate

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A pressure regulating valve and ratio controllersmanufactured by Feecon Corp. are being used in these tests.Similar commercial units are available from other vendors.

ZI. TEST RESULTS

A. Orifice Plate System

A series of tests were conducted to confirm the feasibility ".of the orifice metering plate injection system. Straight-edgedorifice plates were fabricated to proportion AFFF based on flowrates being used in concurrent testing of sprinkler nozzles.Tables 1 and 2 show proportioning and orifice coefficient ofdischarge Cd data for 4 orifice diameters tested using freshwater. The data confirm that the pressure differentialbetween the concentrate inject-n line and the firemain is thegovernina factor on concentrate flow for a aiven orifice.Concentrate flow is not sensitive to seawater flow. Average Cd --for all tests was 0.74.

in order for an orifice olate system to be efficient, theconcentrate/firemain oressure dif:erential must remainrelativelv constant. An example of the change in AFFFconcentrate resulting from varying pressure differentials for agiven orifice plate is shown in Figure 3. in these tests, flowwas held constant as oressure differential was varied. in anactual submarine situation, flow will also change as firemainoressure changes, which 4n turn will effect % AFF"concentration. The impact, of this is shown in Table 3, whichisnn is shownaio or Tabl 3, w'is a calculation for determinina the crifice plate and AFF7Fconcentrate storage recuirements for a 3.81 cm (1 1/2In.) diameter hose line at various oressures. :his exampleshows the inefficiency of the orifice plate design (i.e.,overcesizn recuirements) when there is a large firemainoressure variation.

Tests of orifice plates were also conducted to determine theaccuracy in calculating the orifice plate diameter for 3%procortioning. For a given orifice plate diameter and solution %-low rate, required oressure differenti l for 3% concentratef-ow was calculated, and then tested using water to determinethe accuracy of the calculation. Data in 'Table 4 shows good_greement between actual and calculated results.

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A series of tests was conducted to confirm the conceptual7 easibility of an in-line balanced pressure proportioning

system. Tests using water have been completed for 5.8 cm (2in.) and 7.62 cm (3 in.) diameter ratio controllers designed toproportion at 3%. The data in Tables 5 and 6 indicate that:

1. Proportioning is constant over a range of demands;

2. Constant proportioning is independent of pressuredifferential; and

3. Friction loss across the unit increases as flowincreases, but is within acceptable limits forapplication to the SSN 21 design.

was noted in some of the 7.62 cm (3 in.) ratio controllertests that there was a slight pressure gain across the unit,probably due to the high injection pressure. when water onlyis flowing through the ratio controller (i.e., no concentrateinjection), :he pressure drop is higher. A complete set ofwater-only data would be required if the unit is used onsubmarines, since this is a possible scenario.

C. Evaluation of Proportioning Systems

Table 7 is an evaluation of the two proportioning systemswith respect to simplicity, proportioning efficiency,design/ooerationai efficiency, reliability, general space,weight and cost factors. The orifice plate system is the moresimple system, but suffers in proportioning efficiency if thepotential for a wide range of flows and pressure differentialsexist. 3oth systems can be considered reliable, but havespecific design details which reduce overall reliability.Additional check and isolation valves are required in theorifice plate system, while supply piping is larger in thebalanced pressure proportioning system.

From a design and operational standpoint, the balancedpressure troportioner has design features which significantlyreduce its efficiency if the recuirement to have combinationseawater and AFFF' stations is maintained.

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T able 7 - Evaluation of orifice plate and balanced pressure porportioning systems

FACMtR ZORIFC PtXTE SYS%4 WANCEDI ORES.URE PRPR:-

I Siliccy Very simnple Simple

2. Prcp=Icn±.nW Eficiuecya. Variable tlcu/ tritficient at :a='e flow :Ocele.t efficiency

pressure differential. and pressure diffeentialsb . Relati.vely costant flowi/ :mroved ef ficiency Excellent efficiency/

pressure differential

*3. OnsigrI/Cperatcal Hose stals- can easily Signficant design Lmlcaticnsefftc-ency flow seawater only for coie seawater only

wit.h a minnu impact on and AFlT capaoil-.tydesign o wet pipe system - slug of seawater

.fn t.he line wn~ch must oedsqdprior to AFFT f2.cw at

the ap'pliance - nign-y Lines;.ac.eo rj pipe system n sidered

-1ye~ral 4v AVSEA)-l.ess reliacle-sli.ght delay i.n agent f'-

o once AFlF is introducedt svstr,seawater only c3paoiity' .s l~-thie alternati.ve is to zreace,in effect, separate AFT-and seawater =ancltu.res "o%1each dual agent szartcn

4. Sajn2it aJ2 crifi.ce diameters fcr Oed end systemi - single valveindividual ,neticn points failure at the conect.on --o t.nemay be easily clogged seawater supply results .n titeo Flne mesh strainers mnay we loss of t21e entire AFT7 system

required- impact on =icentratepressure duje to friction lossacoss strainer

Lnqmct offriction .1oss cnarac-tar!stlCs Over t-na, I.e., as Ppe~sdeteriorate with age, !rict-,on CoSschdactc.stic3 -nay orange, wmcn -myresult In inefficient proprt-ontirs

*5. Gener3l Space, ',ei'nt, Aditionial d~/bacxflow preven- Zaz-er supply pipe size requiredcotticn & gate valves recuired from central inecin pit -

because each ±iLscrarge station irdiv~dual discrar-ge o.jtlots--t:-_sIs onecota to t!' seawater supply lina is an AF oF tc in eftssible agent storage Lncrease nrsea of a conentrate Linif potential 'cr large centratei Balani-cng valve and ratio conrt:=11-seawater pressure diffe-rent.al exists b'r "--stead or or~f~ce p,.3te5

14

IV. ALTERNATIVE SYSTEMS

Two additional alternatives to orifice metering plates havebeen identified for distributed single-user injection points.An automatic flow control valve has been ordered forevaluation. This diaphragm operated valve may be able tomaintain a constant flow of AFFF concentrate over a range ofdifferential pressures. This may reduce overdesignrequirements as shown in Table 3 (i.e., flow rate will notincrease as pressure differential increases). The effective .free area of the orifice opening may also be larger than theopening in an orifice plate for the same design point, which 0could reduce the possibility of clogging and increasereliability.

Akron Brass Co. is working on a modified eductorproportioning concept. Their goal is to create an eductor ""which will oroportion concentrate (injected under pressure)within a relatively nacrow range (e.g., 3-5%) over a range ofpressures and flows, while maintaining relatively low pressuredrop across the unit. NRL will maintain contact with Akron tokee abreast of this developmental work.

V. SUMMARY

The AFFF fire suppression systems proposed for flammable'iqui fuel hazards on the SSN 21 require proportioning systemsto inject 3% AFFF concentrate into seawater systems to createAFFF solution. Alternative proportioning systems each of whichutilizes an air-pressurized concentrate storage tank are beingevaluated by the Naval Research Laboratory (NRL). Onecandidate system uses multiple single-user injection points(e.g., orifice metering plates) to proportion AFFF at each hosestation or sprinkler system. The other system, which uses anin-line balanced pressure proportioner and ratio controller, isdesigned as a central system which can proportion over a rangeof demands.

Proportioning using the orifice plate system is pressuresensitive and not flow sensitive. As pressure differentialbetwee:n the iniected concentrate and seawater increases, flowrate increases. if pressure differential can vary considerablyduring operation, AFFF flow and storage requirements must beoverdesigned to meet the lowest design point, i.e., 3% at thesmallest cressure diffee na. ie size of the orifice in the*f te design may be so small (e.., 2. cm (0.1 in.)ia.) -hat clogging cf :he oriffice couCd e a Zroo-1m.

Prooortioning usina the balancing valve system is flowsensitive. A steady level of % concentrate is maintained overa range of flows. The use of a central proportionina systemcreates, in etzct, a secarate AFFE firemain system. Thecentral croportioning system allows more effective use of AFFFconcentrate, but significant desion and oceraticnal problemsresult from the recuirement to have seawater onv cacabilitv atAFF hose stations.

15

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Future R&D work will focus on the single-user injectionpoint system. Two additional single-user injection pointsystems may be available for testing in the near future.

16

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