FIRE RESEARCH STATION

Transcription

1 F;" r!:'~ ~''":- :!~,. ":''> "'-;1 ~~.~: ';::'.,'\'" ;.;'"!..;..:.~,;.= L",;~.: ~...;:;.; -::, ',,,., ::;.,;:: Fire Researh Note No _.._- TH FFCT OF FOAM LQUD CONCNTRATONS ON FR PRFORMANC ON LA BORA TORY FffiS by J G Corrie January 1976 FR RSARCH STATON BR Trust (UK) Permission is granted for personal nonommerial researh use. Citation of the work is allowed and enouraged.

2 Fire Researh Station BOR HA MWOOD Hertfordshlre \VD6 2BL Tel:

3 Fire Researh Note No January 1976 TH FFCT OF FCAM LQUD CONCNTRATONS ON FR PRFORMANC ON LABORATORY FRS by J G Corrie SUMMARY The effet of deterioration of foaming solutions of fluoroprotein and fluorohemial liquids has been simulated by dilution, and the onsequent hange in performane has been measured by means of the new 0.25 m 2 test fire desribed in FR Note No The results obtained are ompared with earlier ones on the Defene Standard 42-3 fire of 0.28 m 2 area, over whih the new fire is shown to have advantages. KY WORDS: Foam, laboratory, fire test, storage properties, fluorohemial, fluoroprotein. Crown opyright 1976 Department of the nvironment and Fire Offies' Committee Joint Fire Researh Organization

4 TH FFCT OF FOAM LQUD CONCNTRATONS ON FR PRFORMANC ON LABORATORY FRS by J G Corrie NTRODUCTON Only meagre information is available on the keeping properties of foam liquids and this work was undertaken to illustrate how hanges in the test methods, beause they are more eonomial of laboratory time, will permit more extensive information to be obtained. n a series of experiments to assess the storage properties of foam liquids 1,2 it was shown that a fire test onduted with the reommended onentration of foam liquid would not reveal deterioration until it had progressed to an unaeptable exterrt, This was overome by testing the foam liquid at a number of onentrations to determine the minimum onentration required for optimum effetiveness. The resulting work load was unaeptably large, beause between 6 and 10 experimental fires were required to assess eah stored sample. A new laboratory fire test for foam liquids has reently been developed 3 and it was thought that this new test might provide a more eonomial method of assessing storage samples. xperimental fires were therefore onduted with the new proedure, using two foam liquids at various onentrations. The results obtained were ompared with those previously obtained using the original fire test, and foam liquids of the same groups. The signifiant differenes between the two fire tests are that the new test employs foreful appliation of the foam, as ompared with gentle surfae appliation in the original test, and also inludes a burn-bak test whih the original test does not. The two tests differ slightly in size, the original test employing 0.28 m 2 fires, and the new test 0.25 m 2 area fires; and these fire sizes are used to differentiate the two test methods in the remainder of this report. XPRMNTAL MTHODS The 0.28 m 2 fires were onduted as desribed in UK Defene Standard and Fire Researh Note No The test uses petrol with a boiling range C as fuel. A preburn time of 30 seonds is allowed. The foam is applied gently onto the fuel surfae at m 2-min. The 0.25 m 2 fires were onduted as desribed in Fire Researh Note No exept that at the lower onentrations it was neessary to redue the foam

5 nozzle diameter from 7 mm to 5 mm, to allow the flow rate to be redued to the desired value. Aviation gasoline was ~sed as fuel. A preburn time of 1 minute was allowed. The foam was applied as a jet into the entre of the fire, for a total period of 3 minutes. A brass pot ontaining 1 litre of gasoline was then plaed in the entre of the tray and ignited, and the time for the fire to re-over the whole test area was measured. MATRALS USD Fluorohemial foam liquid Fluoroprotein foam liquid A ommerially available produt manufatured in Belgium - Grade FC 200 normally used at 6 per ent onentration. A ommerially available produt manufatured in UK, normally used at 4 per ent onentration. XPRMNTAL RSULTS Figures 1 and 2 show the results obtained on the 0.25 m2 fires using fluorohemial and fluoroprotein foam respetively. Figures 3 and 4 ompare the 90 per ent ontrol times of the 0.25 m 2 fires with those of the 0.28 m 2 fires. DSCUSSON The deterioration of foam liquids in solution may be simulated by diluting the solutions to varying degrees and determining how the foam properties hange with degree of dilution, as assessed by standard test methods. This approah is only valid if all the onstituents of the foam liquid degrade in storage at the same rate, and are onverted to inert end produts. n pratie deterioration in storage annot be expeted to follow suh an unompliated ourse, and these dilution tests are onsequently limited in value. Aepting this limitation, they give a simple and pratial tehnique for obtaining information. Different samples of foam liquids were used for the tests on the two test fires. The fluoroprotein foam liquids were from manufaturer A, while the fluorohemial foam liquids were from manufaturerob, one grade (FC 196) being used on the 0.28 m 2 fires, while another (FC 200) was used on the 0.25 m 2 fires. Some differenes between the results on the two fire sizes may be attributable to differenes in the foam liquid samples, but as the primary interest is in the shape of the urves obtained, the omparison of the two sets of results iso justifiable. 2

6 Referring to the results using fluorohemial, shown in Fig.1, it an be seen that the the ontrol and extintion times are not proportional to the onentration, and a dilution to almost 50 per ent of the reommended onentration was neessary before an unmistakable inrease was observed. Figure 3, however, shows that the 0.25 m 2 fire gave a more pronouned response than did the 0.28 m 2 whih required a dilution to 20 per ent of the reommended onentration before an unmistakable inrease in the ontrol time was observed. Returnir~ to Fig.1, the expansion and shear stress both fell progressively with inreasing dilution, and the effet of a 20 per ent dilution would be unmistakably observed. The drainage time showed relatively little hange with onentration. The burn-bak time also showed relatively little hange with onentration and therefore the 0.25 m2 test has no apparent advantage over the 0.28 m 2 test beause of the inlusion of a burn-bak measurement when onsidering the deterioration of fluorohemial samples. This is probably beause the burn-bak resistane of fluorohemial foam is largely influened by its film forming property and only small amounts of fluorohemial are neessary to ensure film formation, and suffiient is provided by even a 1~ per ent solution. The results for the fluoroprotein foam shown in Fig.2 and Fig.4 show a similar inrease in the dependene of the ontrol time on onentrations, when the 0.25 m 2 fire is ompared with the 0.28 m 2 fire, as was obtained with fluorohemial. 35 per ent dilution would be unmistakably deteted as ompared with 55 per ent with the 0.28 m 2 fire. The burn-bak time, and all three foam properties were highly dependent upon onentration and a 20 per ent dilution would be deteted by any of these measurements. The burn-bak times obtained by these dilution tests may not be a valid model of atual storage deterioration. t is not improbable that the burn-bak resistane is related to the total quantity of protein in the foam as a separate effet from its ability to foam. although i ts f'oami.ng properties may fall. n storage the total quantity of protein will not hange Another point of interest is that in the ase of fluorohemial the ontrol time and the extintion time both responded similarly to onentration and approximately 50 per ent dilution was required for an inrease to be unmistakably deteted. With the fluoroprotein the extintion time showed a greater dependene on onentration than did the ontrol time and a 20 per ent dilution would be unmistakably deteted. A 3

7 We an onlude therefore that the new 0.25 m 2 fire test, whih uses foreful appliation, is usefully more sensitive to onentration and should therefore be 'preferred for the assessment of the quality of storage samples, rather than the 0.28 m2 fire test whih uses gentle surfae appliation. f ontrol time, with the reommended onentration, is used alone as a basis for assessment even the 0.25 m 2 test may not reveal deterioration unless it exeeds 50 per 0ent. f, however, extintion time and foam properties are inluded as performane requirements a deterioration of 20 per ent is unlikely to pass undeteted. t is, however, generally aepted that quality assessment must primarily be related to fire ontrol and extintion and in the present state of knowledge it would be diffiult to justify ondemning stoks of foam liquid beause of a hange in foam properties if the produt will still ontrol and extinguish effetively. For the routine assessment of storage samples a simple single test is required. The proedure of determining a onentration x ontrol time urve is so demanding of time that it annot be applied on the wide sale whih is desirable. A single onentration test using'the new 0.25 m 2 fire provides a method whih will just suffie. Deterioration up to 50 per ent may not be deteted by the ontrol time observation, but if the extintion and burn-bak times, and the foam properties are also onsidered they will permit the reognition of samples whih are showing hanges and merit reappraisal after a further short period. n addition to their purpose of seleting methods for the examination of storage samples, these tests also permit the evaluation of the 0.25 m 2 fire as a purhase ontrol to ensure that new supplies have beenprepared to the orret onentration, and they also provide information on the margin of safety in the foam liquid to allow for errors in proportioning, variation in the effiieny of branhpipes and some deterioration in storage. As a purhase ontrol tool the test has the same limitations as its use for storage assessment; the ontrol and extintion times, at a single onentration, are not a reliable indiation that the material has been prepared to the orret onentration, but the expansion and shear stress provide good guides for fluorohemial foam, while for the fluoroprotein the expansion, shear stress, drainage time and burn-bak time all provide effetive indies of onentration. The safety margin an only be assessed from the onentration urves, and a test at a single onentration does not enable an assessment to be made. The test 4

8 results in Fig.1 indiate that the fluorohemial sample had a onentration safety margin 50 per ent above that required to give good ontrol and extintion, while Fig.2 indiates that the fluoroprotein sample had only a small margin of safety. The tests also supported the laims for the simpliity, quikness, reliability and fuel eonomy of the 0.25 m 2 fire, desribed in FR Note No CONCLUSONS AND RCOMMNDATONS 1. By using the new 0.25 m 2 fire test, desribed in Fire Researh Note No for assessing the quality of stored samples of foam liquids, a test at a single onentration will suffie to reveal a serious degree of deterioration. eonomy of this proedure will permit a more extensive monitoring of the keeping properties of foam liquids than does the urrent method requiring fire tests at a range of onentrations using the Defene Standard 42-3 laboratory fire. 2. Tests using the 0.25 m 2 fire, at a single onentration, will show whether the foam liquid is still effetive, but the ontrol time will not reveal the extent of any deterioration whih has ourred, and this ould be up to 50 per ent of the ative ingredients. 3. f the extintion time and foam properties are also observed, adverse hanges of a lesser degree will be noted, and deterioration exeeding 20 per ent is unlikely to pass undeteted. 4. ven with this new fire, tests at a range of onentrations are required to obtain a lose assessment of the extent of deterioration. 5. The new 0.25 m 2 fire test is not fully effetive in verifying the quality of new deliveries of foam liquid, if only the 90 per ent ontrol time is observed. The extintion time, the foam properties, and the burn-bak time are also neessary to provide a trustworthy assessment. The RFRNCS 1. CHTTY T B, GRFFTHS D J, TUCKR D M and CORR J G. Storage properties of four foam liquids (interim report) Department of the nvironment and Fire Offies' Committee Joint Fire Researh Organisation Fire Researh Note 933 April BNSON S P, GRFFTHS D J, TUCKR D M and CORR J G. Storage Properties of Four Foam Liquids (Final Report) Department of the nvironment and Fire Offies' Committee Joint Fire Researh Organisation Fire Researh Note 980 August

9 3. BNSON S P, BVAN P R and CORR J G. A laboratory fire test for foam 'liquids. Department of the nvironment and Fire Offies' Committee Joint Fire Researh Organisation Fire Researh Note 1007 April Defene standard 42-3ssue 124 January Foam Liquid - ~re rlinguishing. Diretorate of Standardization, Ministry of Defene, First Avenue House, High Hoborn, London WC ,5 e \ ' " sioo,-... so ;:; u 'j 80 -g 70 o f 60 ei C tl ';; tl Cl 0,- 0L '0... C tl lou - tl Q. glo C\ So C\ '0 7a e 6'.: o u ~5:)5.8 i ~ u ; J:J a. '0 o 30 3 e 'iii o Q. l:) ~ """,,a\: 2 00._-, - _e _- e- ~3 --:.~ Z j L 2 g 6i o 1=90 pzr ent ontrol t'lmll 2= 20 m 25 pllr ent droinogll t"lmz 3= xtintion t'lmz 4=xpons',on 5=Burn-bak t'lmll 6:Shllor str-ess FigUrlZ1 Q 25m 2 oreo petro: tires QXt'lnguishoo with fluorotlm1io.l foam appizd at 3llrrf-min and l.500 with various onentmtions 6

10 To 211 t 'f ~ '';:; ::f " '0 L "0 " '0~C C:i en ~ t ~ U') '~90 gn 0.- u B@ gbo.~ 'U x : ~ 0 " 70 7 C 0. Ē 60 6 x... u 0.a 0 u 50 5 : L ~ :J C J:J C: u 40 4'0 L C Ci 0 Q en 'in 0.~ 2 Q. ~ 6 ' 0 5 fill - Z o~.. in L g s: til & o Conerurotron-iper ent,= Stwlor stress 2: 90 pzr ent ontrol time 3=20m 25 PQt' ent droinogtl t"lmcl 4= xtlntion flmcl 5= xponston 6:Burn - bok t',mcl. Figura 2 Q 25m 2 oreo petrol fires Q.Xtingui.sh2d with fluoroprot<zwl foam applt2d at 3llm~min and used at various onentrotlons

11 en ell 90 1 '.;J eeo., 0 ~70 : u 560 Q o Conentr-tion-per ent 1=0 2emJ reo firtls C bo.hng point petrol - pplrotion rate = 2'4tJm l-m"1n -gtlntj<z 5ur10CCZ OPP COtion -trom F.re Researh Not(l933 2:.025m 2 reo fi,.as of ov".o6on gosojrw -applo(lon rotll 3 tlm 2 _ min foraztul app'iatton Figura 3 Comparison of 90 p2f" CQJ1t ontrol times of two nborotory fires usi1g fh..orohzrniaj foam at various orentronons

12 150n-----n----""'r-' en 90 ~.;; 80 ~ ~ 70 o u 1: 50 3 ~ &~O o at o 123 nenu-non- par ent 4 1=0'28m 2 or-e f 1rfls of C boiling rongz p<ltrol- appr.ot",on rate= 2 4 tlml-min - g<l ntle surf oe opplfo tion-rrorn ':-nl Reseorh Notfl 933 2=O 25m 1 ar ClO f.rfls of aviation gosdmfl oppflotion rolz=311m l - mm fot"flfuj oppliotlon Figurz4 Comprison of 90 par ant ontrd f.mas of two laboratory firtls using tluoroprotem foam at various onenfmtions Printed in nglmd for Her Majesty s Stationery Offie By Studio Trade Plates Ltd. Watford WD1 SSA. 1500