Small-scale fire extinguishment test on mechanical foam. Part 1

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Small-scale fire extinguishment test on mechanical foam. Part 1 Sumi, K.

NATIONAL RESEARCH COUNCIL CANADA

D I V I S I O N OF B U I L D I N G RESEARCH

ShKGL-SCALE

FIRE

EXTINGUISHMENT

TEST

ON MECHANICAL FOAM

PART I by K. S u m i I n t e r n a l R e p o r t No. 224 o f t h e D i v i s i o n o f B u i l d i n g R e s e a r c h OTTAWA J u n e 1 9 6 1

PREFACE

Foam i s one of t h e more i m p o r t a n t f i r e e x t i n g u i s h i n g a g e n t s a n d i s u s e d e x t e n s i v e l y on flammable l i q u i d f i r e s .

It i s n e c e s s a r y t o be a b l e t o d e f i n e and t o measure t h e s u i t a b i l i t y of a g i v e n foam f o r a g i v e n a p p l i c a t i o n . U n t i l such t i m e a s it becomes p o s s i b l e t o p r e d i c t foam p r o p e r t i e s from measured p h y s i c a l p r o p e r t i e s it i s n e c e s s a r y t o r e l y , a s a t p r e s e n t , upon performance - t y p e t e s t s employing s t a n d a r d f i r e s s e t i n t a n k s c o n t a i n i n g a flammable l i q u i d . P r e l i m i n a r y

s t u d i e s , which it i s hoped w i l l l e a d t o t h e development of a n improved f i r e t a n k t e s t f o r mechanical foam, a r e now r e p o r t e d . !The a u t h o r , a chemical e n g i n e e r and a r e s e a r c h

o f f i c e r i n t h e F i r e Research S e c t i o n o f t h e D i v i s i o n , i s engaged i n s t u d i e s of v a r i o u s a s p e c t s of f i r e e x t i n g u i s h m e n t . Ottawa J u n e 1 9 6 1 N . _{B. Hutcheon,} A s s i s t a n t D i r e c t o r .

SMALL-SCALE FIRE EXTINGUISHMENT TEST ON MECHANICAL FOAJ1

PART

I by K. Sumi

The F i r e S e c t i o n of t h e D i v i s i o n o f B u i l d i n g R e s e a r c h , N a t i o n a l R e s e a r c h C o u n c i l , h a s been a s s i s t i n g t h e Royal

Canadian Air Force f o r s e v e r a l y e a r s w i t h t e s t s on foam- g e n e r a t i n g equipment i n s t a l l e d i n t h e i r c r a s h t r u c k s . T h i s work, a n d a s s o c i a t e d e x p e r i e n c e , i n d i c a t e d a n e e d f o r a b e t t e r method f o r e v a l u a t i o n o f foam, a n d it w a s d e c i d e d t o c o n d u c t s t u d i e s d i r e c t e d toward t h e development o f a f i r e e x t i n g u i s h m e n t t e s t s u i t a b l e f o r a s s e s s i n g t h e performance p o t e n t i a l of foam. One of t h e most w i d e l y u s e d of t h e e x t i n g u i s h m e n t t e s t s f o r foam a v a i l a b l e , a t p r e s e n t i s t h e f i r e t e s t d e s c r i b e d i n JFMC S p e u i f i c a t i o n No. 260.00 (which was

a d o p t e d from JAN-C-266 o f t h e U n i t e d S t a t e s ) (1, 2 ) . T h i s I1 _{go-no go" t e s t f o r foam l i q u i d i s c o n s i d e r e d u n s u i t a b l e f o r} a s s e s s i n g t h e p o t e n t i a l e x t i n g u i s h i n g e f f e c t i v e n e s s o f foam b e c a u s e t h e c h a r a c t e r i s t i c s o f foam c a n n o t be v a r i e d ( i n t h i s t e s t ) . I n p r a c t i c e t h e r e i s c o n s i d e r a b l e v a r i a t i o n i n t h e c h a r a c t e r i s t i c s o f foam, w i t h t h e r e s u l t t h a t t h e r e is a n e e d f o r a method t o a s s e s s t h e performance p o t e n t i a l o f foam o v e r a wide r a n g e o f c h a r a c t e r i s t i c s . It w a s t h e purpose o f t h e p r e s e n t i n v e s t i g a t i o n t o c a r r y o u t s t u d i e s t o w a r d s development o f a s m a l l - s c a l e f i r e e x t i n g u i s h m e n t t e s t , i n c o n t r a s t t o t h e l a r g e 10- by 1 0 - f t f i r e t e s t u s e d i n t h e JFMC s p e c i f i c a t i o n . A s m a l l - s c a l e f i r e t e s t which c o u l d be c o n d u c t e d i n a l a b o r a t o r y on a y e a r - round b a s i s would n o t o n l y be u s e f u l f o r r e s e a r c h i n v e s t i g a t i o n s b u t c o u l d a l s o b e c o n s i d e r e d e i t h e r

a s

a r e p l a c e m e n t o r

a s

a n a l t e r n a t i v e f o r t h e f i r e t e s t of JFMC S p e c i f i c a t i o n No. 260.00 i f i t p r o v e d t o be s u i t a b l e . The p r e s e n t r e p o r t d e a l s w i t h s t u d i e s t o d e t e r m i n e s u i t a b l e e x p e r i m e n t a l c o n d i t i o n s f o r e x t i n g u i s h m e n t of 2- by 2 - f t flammable l i q u i d f i r e s .

FIRE TEST I N JFMC SPECIFICATION NO. 260.00

d e s c r i b e d i n J P M C S p e c i f i c a t i o n No. 260.00. B r i e f l y , t h e t e s t p r o c e d u r e i s a s f o l l o w s : A minimum of 1 5 0 g a l " of g a s o l i n e i s f l o a t e d on 200 g a l of w a t e r i n a f i r e t a n k 1 0 by 1 0 by

3

f t deep. A f t e r a pre-burn p e r i o d of 60 s e c , foam i s d i s c h a r g e d t h r o u g h a s t a n d a r d n o z z l e a t

5

g a l p e r minute s u p p l i e d w i t h w a t e r a t a p r e s s u r e of 1 0 0 p s i . The foam s t r e a m i s d i r e c t e d from a p o s i t i o n j u s t above t h e s i d e of t h e t a n k a c r o s s t h e f i r e j n o r d e r t o s t r i k e t h e a p p r o x i m a t e c e n t r e of t h e o p p o s i t e t a n k w a l l a t r i g h t a n g l e s . Foam i s a p p l i e d f o r 5 m i n u t e s . V i s u a l o b s e r v a t i o n s a r e r e c o r d e d d u r i n g t h e t e s t . The f i r e t e s t h a s s e r v e d a u s e f u l p u r p o s e o v e r a number of y e a r s by making p o s s i b l e t h e i d e n t i f i c a t i o n o f poor q u a l i t y i n foam l i q u i d . It a p p e a r s s u i t a b l e f o r d i f f e r - e n t i a t i n g between good a n d bad q u a l i t y foam l i q u i d . Its

weakness, however, a p p e a r s t o e x i s t i n t h e c l a s s i f i c a t i o n o f foam l i q u i d s t h a t f a l l between t h e two e x t r e m e s . The

c r i t e r i a f o r f a i l u r e o f a sample o f foam l i q u i d a r e b a s e d l a r g e l y on v i s u a l o b s e r v a t i o n a n d p l a c e a g r e a t d e a l o f r e s p o n s i b i l i t y on o b s e r v e r s . Some o f t h e r e q u i r e m e n t s g i v e n i n t h e s p e c i f i c a t i o n a r e :

1. The foam s h a l l s p r e a d o v e r t h e t a n k i n n o t more t h a n 2 min. 2. The f i r e s h a l l be c o n t r o l l e d , i . e . , e x t i n g u i s h e d e x c e p t f o r l i c k s of f l a m e a t t h e e d g e s of t h e foam b l a n k e t , i n n o t more t h a n

4

min. The f i r e s h a l l b e more t h a n 5 min. c o m p l e t e l y e x t i n g u i s h e d i n n o t

4.

The foam s h a l l n o t s p r e a d a l o n g i n s l i p p l a n e s o v e r t h e g a s o l i n e s u r f a c e .

5. The foam s h a l l p r o t e c t t h e g a s o l i n e from r e - i g n i t i o n by a l i g h t e d t o r c h f o r a p e r i o d o f n o t l e s s t h a n 1 5 min. E x p e r i e n c e w a s g a i n e d i n a p p l y i n g t h e s e c r i t e r i a

in

t h e c o u r s e o f a number o f f i r e t e s t s , c a r r i e d o u t i n a c c o r d a n c e w i t h

JPMC

_{S p e c i f i c a t i o n No. 260.00, on a foam} l i q u i d which h a d met t h e r e q u i r e m e n t s o f t h e s p e c i f i c a t i o n . !he foam a p p e a r e d t o s a t i s f y t h e f i r s t two r e q u i r e m e n t s w i t h o u t d i f f i c u l t y , a l t h o u g h t h e a c t u a l t i m e s r e c o r d e d f o r

c o v e r a g e a n d c o n t r o l , p a r t i c u l a r l y t h e l a t t e r , a r e a t t h e d i s c r e t i o n of t h e o b s e r v e r . I n most c a s e s t h e r e q u i r e m e n t

f o r complete e x t i n g u i s h m e n t w a s n o t s a t i s f i e d . I t may be q u e s t i o n e d whether t h i s r e q u i r e m e n t i s a r e a s o n a b l e c r i t e r i o n f o r f a i l i n g a sample, because f l i c k e r s o f flame may remain a t t h e c o r n e r s o r edges o f t h e t a n k even though t h e f i r e h a s been c o n t r o l l e d f o r some t i m e . Foam d i d s p r e a d a l o n g i n

s l i p p l a n e s b u t o n l y t o a v e r y l i m i t e d d e g r e e . I n t e r p r e t a t i o n of t h i s r e q u i r e m e n t i s a l s o a t t h e d i s c r e t i o n of t h e o b s e r v e r . The foam d i d n o t g i v e p r o t e c t i o n a g a i n s t r e - i g n i t i o n a t t h e c o m e r s and edges of t h e t a n k where f l i c k e r s of flame h a d t o be e x t i n g u i s h e d a f t e r foam a p p l i c a t i o n h a d t e r m i n a t e d . These e x p e r i e n c e s i l l u s t r a t e t h e d i f f i c u l t i e s a r i s i n g from r e l i a n c e upon v i s u a l o b s e r v a t i o n a n d o b s e r v e r ' s judgment i n d e t e r m i n i n g t e s t c r i t e r i a . The u s e of a f i r e t a n k 1 0 by 1 0 by

3

f t deep r a i s e s f u r t h e r problems. Because o f t h e r e l a t i v e l y l a r g e s i z e of t h e t a n k , t e s t s a r e u s u a l l y conducted o u t d o o r s where

changes i n b o t h s p e e d and d i r e c t i o n of wind may a f f e c t t h e r e s u l t s . A foam l i q u i d which c o u l d meet t h e r e q u i r e m e n t s under i d e a l w e a t h e r c o n d i t i o n s m i g h t f a i l b e c a u s e of t h e i n f l u e n c e o f wind. A f u r t h e r d i s a d v a n t a g e o f such a l a r g e t e s t i s t h e expense i n c u r r e d . C a p i t a l expense w i l l , o f c o u r s e , be h i g h , b u t i n a d d i t i o n a minimum of 1 5 0 g a l o f g a s o l i n e i s r e q u i r e d f o r each t e s t . The f i r e t e s t i s n o t i n t e n d e d f o r e v a l u a t i n g r e l a t i v e q u a l i t y o f foam l i q u i d n o r f o r a s s e s s i n g t h e p o t e n t i a l e x t i n g u i s h i n g a b i l i t y of a foam of g i v e n c h a r a c t e r i s t i c s . I t s u s e a s a r e s e a r c h t o o l i s t h e r e f o r e v e r y l i m i t e d . PRESENT INVESTIGATION It was d e c i d e d t o r e t a i n t h e performance a s p e c t s of t h e 10- by 1 0 - f t f i r e t e s t , b u t t o a t t e m p t t o s c a l e it down i n o r d e r t o overcome s e v e r a l o f tine problems i n h e r e n t i n t h e u s e o f a l a r g e t a n k . A t a n k s i z e of 2 by 2 f t mhich i s small

enough t o p e r m i t t e s t i n g i n a l a b o r a t o r y ,

was

s e l e c t e d f o r d e t a i l e d i n v e s t i g a t i o n .

The s t a n d a r d n o z z l e u s e d i n t h e l a r g e f i r e t e s t

produces foam w i t h one s e t o f c h a r a c t e r i s t i c s . I n o r d e r t o v a r y t h e p a r a m e t e r s of foam c h a r a c t e r i s t i c s

it

w a s d e c i d e d t o u s e a l a b o r a t o r y foam g e n e r a t o r c a p a b l e o f p r o d u c i n g foam o v e r wide r a n g e s o f expansion r a t i o , 25 p e r c e n t d r a i n a g e t i m e and s o l u t i o n r a t e o f a p p l i c a t i o n w i t h r e s p e c t t o t h e s i z e o f t h e f i r e . Expansion r a t i o i s t h e r a t i o of f i n a l foam volume t o t h e o r i g i n a l foam s o l u t i o n volume. !be 25 p e r c e n t

d r a i n a g e t i m e i s t h e t i m e a t which

25

p e r c e n t o f foam

s o l u t i o n may be d r a i n e d from a sample of foam i n a s t a n d a r d foam c o n t a i n e r

( 3 ) ,

a n d i s a n i n d e x o f t h e d e g r e e o f s t a b i l i t y a n d f l u i d i t y of t h e foam. The i n f l u e n c e o f v a r i a t i o n i n t h e s e f a c t o r s upon e x t i n g u i s h m e n t was d e t e r m i n e d . I n a n a t t e m p t t o f i n d a more o b j e c t i v e e n d - p o i n t f o r t h e t e s t ,

i t

w a s d e c i d e d t o u s e a r a d i o m e t e r t o a s s e s s p r o g r e s s of e x t i n g u i s h m e n t , t h u s e l i m i n a t i n g i n c o n s i s t e n c i e s r e s u l t i n g from v i s u a l o b s e r v a t i o n a n d dependence upon o b s e r v e r ' s

judgment. I t was d e c i d e d a l s o t o u s e " c o n t r o l " t i m e , a s d e t e r m i n e d by t h e u s e o f a r a d i o m e t e r , r a t h e r t h a n " e x t i n g u i s h m e n t " t i m e a s t h e e n d - p o i n t f o r t h e p h a s e o f t h e i n v e s t i g a t i o n now r e p o r t e d . EXPERIMENTAL DETAILS A p p a r a t u s 1. Foain G e n e r a t o r An a d j u s t a b l e foam g e n e r a t o r c a p a b l e o f p r o d u c i n g foam o v e r w i d e r a n g e s o f e x p a n s i o n a n d f l u i d i t y a t d i f f e r e n t r a t e s of f l o w w a s c o n s t r u c t e d ; i t s d e s i g n i s similar t o t h a t u s e d by Tuve a n d P e t e r s o n ( 4 ) .

A pre-mixed foam s o l u t i o n i s pumped t h r o u g h a f l o w m e t e r i n t o t h e foam m i x i n g chamber o f t h e g e n e r a t o r a n d c o m p r e s s e d a i r i s f e d t h r o u g h a n o t h e r f l o w m e t e r i n t o t h e same m i x i n g chamber. The f l o w r a t e s o f t h e two f l u i d s a n d t h e i n p u t p r e s s u r e s a r e c o n t r o l l e d b y a p p r o p r i a t e v a l v e s t o g i v e t h e d e s i r e d r a t e s o f d i s c h a r g e , from which e x p a n s i o n r a t i o o f t h e foam c a n a l s o be d e t e r m i n e d . The m i x i n g chamber p r e s s u r e c a n b e v a r i e d t o c o n t r o l t h e f l u i d i t y o f foam by t h e u s e o f i n t e r c h a n g e a b l e o r i f i c e s a t t h e i n l e t a n d o u t l e t o f t h e m i x i n g chamber a n d w i t h i n t e r c h a n g e a b l e p e r f o r a t e d d i s c s a t r i g h t a n g l e s t o t h e d i r e c t i o n o f f l o w i n t h e m i x i n g chamber. The foam p r o d u c e d i n t h e m i x i n g chamber p a s s e s t h r o u g h a $-in. d i a m e t e r r u b b e r h o s e a n d d i s c h a r g e s t h r o u g h i n t e r c h a n g e a b l e n o z z l e s . The s i z e of n o z z l e t o b e u s e d f o r a p a r t i c u l a r f i r e e x t i n g u i s h m e n t t e s t w a s s e l e c t e d , i n g e n e r a l , on t h e b a s i s o f t h e l a r g e s t n o z z l e which would p r o j e c t

a

s o l i d s t r e a r n o f foam t o t h e o p p o s i t e s i d e o f t h e t a n k . I t w a s sometimes n e c e s s a r y t o u s e a s m a l l e r n o z z l e t o a v o i d a p p r e c i a b l e

f l u c t u -

a t i o n s d u r i n g t h e i n i t i a l s t a g e s o f foam a p p l i c a t i o n .

2. F i r e Tank

!The _{f i r e t a n k , 2 by 2 by 1 f t deep, was c o n s t r u c t e d} of s t e e l . 3. F u e l The f u e l u s e d w a s commercial g r a d e h e p t a n e .

It

w a s c o n s i d e r e d t h a t i t h a d c e r t a i n a d v a n t a g e s o v e r t h e g a s o l i n e used i n t h e f i r e t e s t d e s c r i b e d i n

JPMC

_{S p e c i f i c a t i o n No.} 260.00. It h a s a much n a r r o w e r d i s t i l l a t i o n r a n g e t h a n g a s o l i n e and i s b e l i e v e d t o p r o v i d e more r e p r o d u c i b l e c o n d i t i o n s , p a r t i c u l a r l y when t h e u n b u r n t f u e l of one t e s t i s used t o g e t h e r w i t h f r e s h f u e l f o r a s u c c e e d i n g t e s t . I n a d d i t i o n , t h e p r o p e r t i e s of g a s o l i n e a r e known t o v a r y s e a s o n a l l y and w i t h t h e p r o d u c e r and p o i n t o f o r i g i n

( 5 ) .

4.

Radiometer

R a d i a t i o n from a f i r e w a s measured by means o f a g o l d d i s c r a d i o m e t e r ( 6 ) , c o n n e c t e d t o a m i l l i v o l t r e c o r d e r . The r a d i o m e t e r was p l a c e d 6 f t from one s i d e o f t h e t a n k

a t

a n e l e v a t i o n of 2 f t above t h e t o p o f t h e t a n k .

5.

Ilwenty-five P e r Cent Drainage Time

The 2 5 p e r c e n t d r a i n a g e t i m e was u s e d as a measure of t h e f l u i d i t y of foam, d e t e r m i n e d a c c o r d i n g t o t h e method developed by 'Puve and P e t e r s o n ( 3 , 4 ) . T h i s _{t e s t i s e a s y}

t o perform a n d r e q u i r e s v e r y simple a p p a r a t u s . !Ihe

expansion r a t i o of foam

was

a l s o d e t e r m i n e d u s i n g t h e 1400-ml pan f o r t h e d r a i n a g e t e s t s , b u t t h e u s e o f t h i s method w a s c o n f i n e d t o c h e c k i n g t h e v a l u e s o b t a i n e d from t h e flolvrneter r e a d i n g s f o r a i r and f o r foam s o l u t i o n . Method Pour g a l l o n s of h e p t a n e , t h e volume e q u i v a l e n t o f a 2-in. l a y e r i n t h e 2-by 2 - f t f i r e t a n k f l o a t e d on 2 i n . o f w a t e r , w a s u s e d a s f u e l . A f t e r a p r e - b u r n p e r i o d o f 60 s e c , f o a n produced by t h e g e n e r a t o r was d i s c h a r g e d t h r o u g h a n o z z l e from a p o s i t i o n d i r e c t l y above t h e m i d - p o i n t o f one w a l l o f t h e t a n k and d i r e c t e d a c r o s s t h e f i r e t o s t r i k e t h e

o p p o s i t e s i d e a b o u t 4 i n . above t h e f u e l s u r f a c e . " C o n t r o l t i m e " , d e f i n e d as t h e tirne a f t e r foam

a p p l i c a t i o n a t which t h e r a d i a t i o n i n t e n s i t y from t h e f i r e was d e c r e a s e d t o 1 0 p e r c e n t of t h e maximum v a l u e r e a c h e d

d u r i n g t h e pre-burn p e r i o d ,

was

determined f o r each t e s t .

A p r o t e i n b a s e foam l i q u i d , whicll h a d met t h e

r e u i r e m e n t s o f JFMC S p e c i f i c a t i o n No. 260.00, was used a t a

2

p e r c e n t by volume c o n c e n t r a t i o n . m e t e s t s were

conducted

a t

expansion r a t i o s of 6 , 8 , 1 0 , 1 2 , 1 4 , 1 6 and

18, s o l u t i o n r a t e s of d i s c h a r g e of 7 , 8 , 1 0 , 1 4 and 18 g a l / h o u r (0.029, 0.033, 0.042, 0.058 a n d 0.075 gal/min/sq f t of f u e l s u r f a c e ) and 25 p e r c e n t d r a i n a g e t i m e s r a n g i n g from 0.5 t o 20 min.

RESULTS AND DISCUSSION

The a d o p t i o n o f c o n t r o l time a s a t e s t e n d - p o i n t h a d two d i s t i n c t a d v a n t a g e s :

i t

p e r m i t t e d t h e u s e of a r a d i o m e t e r , t h u s p r o v i d i n g a n o b j e c t i v e measure o f t h e end of t h e t e s t ; c o n t r o l t i m e was r e a c h e d much b e f o r e complete e x t i n g u i s h m e n t s o t h a t t h e r e was a g r e a t s a v i n g i n time and m a t e r i a l s . I t s u s e w a s c o n s i d e r e d j u s t i f i e d i n t h e s e t e s t s , s i n c e no f u l l y a c c e p t a b l e r e a s o n s c o u l d b e found t o s u p p o r t t h e u s e o f complete e x t i n g u i s h e n t i n a s q u a r e t a n k a s a good measure of foam q u a l i t y . A s i t i s e n t i r e l y

p o s s i b l e t h a t d i f f e r e n t p r o p e r t i e s may be i n v o l v e d depending on t h e e n d - p o i n t u s e d , it w i l l be n e c e s s a r y t o c a r r y o u t f u r t h e r i n v e s t i g a t i o n s t o determine t h e r e l a t i o n s h i p . A l l r e s u l t s r e p o r t e d f o r t h i s s e r i e s o f t e s t s a r e b a s e d on

" c o n t r o l " time a s d e f i n e d .

"Control" time v a r i e d a p p r e c i a b l y when t h e r a t e of

a p p l i c a t i o n of foam w a s low. T h i s b e h a v i o u r i s n o t s u r p r i s i n g f o r r a t e s o f f l o w j u s t above t h e " c r i t i c a l r a t e o f a p p l i c a t i o n " , because any i n t e r f e r e n c e such

a s

a s l i g h t d r a u g h t c o u l d

i n c r e a s e t h e c o n t r o l time s i g n i f i c a n t l y . F o r t h e w o r s t c o n d i t i o n s , e . g . , a t low expansion r a t i o s o f 6 a n d 8 a n d

a t

a low r a t e of a p p l i c a t i o n of 0.029 gal/min/sq f t o f f u e l s u r f a c e , t h e r e s u l t s h a d t o be d i s c a r d e d b e c a u s e o f e x c e s s i v e s c a t t e r and consequent u n r e l i a b i l i t y . The e x p e r i m e n t a l r e s u l t s were p l o t t e d on g r a p h s o f c o n t r o l t i m e a s a f u n c t i o n of 25 _{p e r c e n t d r a i n a g e t i m e}

_{a t}

expansion r a t i o s of 6 , 8 , 1 0 , 1 2 , 1 4 , 1 6 and 18 a n d s o l u t i o n r a t e s of a p p l i c a t i o n of a b o u t 0.029, 0.033, 0.042, 0.058 a n d 0.075 gal/min/sq f t . Drainage t i m e s r a n g i n g from 0.5 t o 20 min were examined. !he r a n g e o f d r a i n a g e time v a l u e s o b t a i n a b l e i s , however, l i m i t e d by t h e d e s i g n of t h e foam

producing equipment. A t low expansion r a t i o s a n d low s o l u t i o n r a t e s of a p p l i c a t i o n t h e l i m i t o c c u r s i n p r o d u c i n g foam of h i g h d r a i n a g e t i m e s , w h i l e

a t

h i g h expansion r a t i o s a n d h i g h

s o l u t i o n r a t e s t h e l i m i t o c c u r s i n producing foam of low drainage t i m e s . Some e x t r a p o l a t i o n of t h e c u r v e s was

c a r r i e d o u t when t h e t r e n d s were c l e a r , i n t o t h e s e r e g i o n s f o r which foam of d e s i r e d c h a r a c t e r i s t i c s could n o t be produced.

!The graphs were used a s a b a s i s f o r p l o t t i n g t h e s i x graphs i n c l u d e d i n t h i s r e p o r t ( F i g . 1 t o 6 ) . The

q u a n t i t y of s o l u t i o n r e q u i r e d t o c o n t r o l f i r e , a s one of t h e c o o r d i n a t e s of each of t h e s e g r a p h s , i s t h e c r i t e r i o n f o r a s s e s s i n g t h e e f f e c t i v e n e s s of f i r e s u p p r e s s i o n . P o r t i o n s

of t h e c u r v e s o b t a i n e d by e x t r a p o l a t i o n a r e shown dashed. Observations made from t h e s i x g r a p h s a r e g i v e n below. Figure 1:

S o l u t i o n r a t e of a p p l i c a t i o n of foam of 0.058 gal/min/ s q

f t

was more e f f e c t i v e t h a n any of t h e o t h e r s o l u t i o n r a t e s i n v e s t i g a t e d a t any drainage time between 2 and 20 min w i t h foam having an expansion r a t i o of 12. !The d i f f e r e n c e i n e f f e c t i v e n e s s of v a r y i n g t h e s o l u t i o n r a t e s from 0.030 t o 0.075 gal/min/sq f t w a s v e r y s m a l l f o r d r a i n a g e t i m e s of

foam between 2 and

5

min. !This d i f f e r e n c e , however., i n c r e a s e d a p p r e c i a b l y w i t h i n c r e a s e i n d r a i n a g e time from

5

t o 20 min, p a r t i c u l a r l y a t lovi s o l u t i o n r a t e s .

The i n f l u e n c e of changes i n d r a i n a g e time on t h e

q u a n t i t y of foam s o l u t i o n r e q u i r e d t o c o n t r o l t h e f i r e

w a s a t

a minimum f o r a s o l u t i o n r a t e of 0.058 gal/min/sq f t . !The i n f l u e n c e of changes i n drainage t i m e w a s small f o r drainage times between 2 and

5

min, b u t i n c r e a s e d a t h i g h e r d r a i n a g e times.

Figure 2:

Optimum expansion r a t i o of foam having a 25 p e r c e n t drainage time of 4 min depended on t h e s o l u t i o n r a t e of a p p l i c a t i o n . The optimum v a l u e w a s v e r y d i s t i n c t a t low

s o l u t i o n r a t e s of 0.030 and 0.033 gal/min/sq f t . The q u a n t i t y of s o l u t i o n r e q u i r e d t o c o n t r o l f i r e above a n expansion r a t i o of 1 2 v a r i e d v e r y l i t t l e a t h i g h e r s o l u t i o n r a t e s of a p p l i c a t i o n . In g e n e r a l , t h e optimum expansion r a t i o a p p e a r s t o be a b o u t

1 2 o r 14. Figure 3:

Foams w i t h expansion r a t i o s of 1 2 and 1 4 were more e f f e c t i v e than t h o s e w i t h expansion r a t i o of 1 0 a t c o n s t a n t

s o l u t i o n r a t e of a p p l i c a t i o n of 0.058 gal/min/sq f t . Foams of h i g h expansion r a t i o s of 1 6 and 18 o b t a i n a b l e were l i m i t e d t o t h o s e w i t h h i g h a p p a r e n t v i s c o s i t y . A s t h e c u r v e s f o r

t h e s e two expansion r a t i o s were b a s e d l a r g e l y on e x t r a p o l a t i o n , t h e y c a n n o t be g i v e n much weight.

The i n f l u e n c e o f changes i n 25 p e r c e n t d r a i n a g e time on q u a n t i t y of s o l u t i o n r e q u i r e d was s m a l l f o r expansion r a t i o s of 1 0 , 1 2 and 1 4 , b u t was much g r e a t e r f o r t h e lower expansion r a t i o s of 6 a n d 8.

F i g u r e 4:

The o r d e r o f d e c r e a s i n g e f f e c t i v e n e s s of foam h a v i n g a 25 p e r c e n t d r a i n a g e time of 4 min based on expansion r a t i o w a s : expansion 1 2 , 1 4 , 1 0 , 8 , 6 . Again, expansion r a t i o s

of 1 6 and 18 were n o t c o n s i d e r e d i n t h e comparison because

a g r e a t e r p o r t i o n of c u r v e s a t t h e s e expansion r a t i o s were p l o t t e d by e x t r a p o l a t i o n . The i n f l u e n c e of changes i n s o l u t i o n r a t e of a p p l i c a t i o n on t h e q u a n t i t y of foam ' s o l u t i o n r e q u i r e d w a s s m a l l e s t when t h e expansion r a t i o of foam w a s 12. F i g u r e 5 : The i n f l u e n c e of changes i n s o l u t i o n r a t e of a p p l i c a t i o n on t h e q u a n t i t y of s o l u t i o n r e q u i r e d w a s s m a l l e r f o r foam

w i t h d r a i n a g e t i m e s of 2 a n d 4 min than f o r foam w i t h d r a i n a g e t i m e s of 1 0 and 20 min.

F i g u r e 6 :

The d i f f e r e n c e i n e f f e c t i v e n e s s w a s small between

d r a i n a g e t i m e s of 2 and 4 min f o r foams w i t h expansion r a t i o s of 1 0 , 1 2 a n d 1 4 . The i n f l u e n c e of d r a i n a g e time on

e f f e c t i v e n e s s d e c r e a s e d a s expansion r a t i o of foam i n c r e a s e d . Foams of low d r a i n a g e t i m e s were n o t o b t a i n a b l e f o r expansion r a t i o s of 1 6 and 18.

CONCLUSIONS

AND

_{RECOl!~IENDATIONS}

1. A s m a l l - s c a l e f i r e e x t i n g u i s h m e n t t e s t such a s t h a t d e s c r i b e d i n t h i s r e p o r t o f f e r s some promise f o r a s s e s s i n g t h e performance p o t e n t i a l o f foam o v e r a wide r a n g e of foam c h a r a c t e r i s t i c s .

2. !be new f i r e t e s t h a s a number o f a d v a n t a g e s o v e r t h e o r i g i n a l 1 0 - by 1 0 - f t f i r e t e s t . Because t h e f i r e t a n k i s

small, t h e t e s t can be conducted i n a l a b o r a t o r y i n a n atmosphere a b s e n t from t h e i n f l u e n c e of w e a t h e r . The r e d u c t i o n i n

expense f o r c o n d u c t i n g small t e s t s i s s i g n i f i c a n t . The u s e of a r a d i o m e t e r f o r d e t e r m i n i n g t h e e n d - p o i n t o f a t e s t

r e d u c e s r e l i a n c e on v i s u a l o b s e r v a t i o n and t h e r e s p o n s i b i l i t y p l a c e d on t h e o b s e r v e r .

3 The f o l l o v i i n g e x p e r i m e n t a l c o n d i t i o n s a p p e a r e d optimum f o r t h e s u p p r e s s i o n of 2- by 2 - f t flammable l i q u i d f i r e by foam, u s i n g t h e method d e s c r i b e d i n t h i s report;:

( a ) S o l u t i o n r a t e o f a p p l i c a t i o n = 0.06 gal/min/sq f t o f f u e l s u r f a c e . ( F i g s . 1, 2 , 4 , 5 )

( b ) Expansion r a t i o o f foam = 12. ( F i g s . 2 , 3 , 4 , 6 )

( c ) 25 p e r c e n t d r a i n a g e time = 2 t o 4 rnin. ( F i g s . 1, 3 , 5 , 6 ) In g e n e r a l , u n d e r t h e c o n d i t i o n s g i v e n above t h e t h r e e

v a r i a b l e s were l e a s t dependent on one a n o t h e r w i t h r e s p e c t t o e f f e c t i v e n e s s i n t h e c o n t r o l o f f i r e s . The e x p a n s i o n r a t i o shown t o be optimum i n t h e p r e s e n t i n v e s t i g a t i o n i s h i g h e r t h a n e x p e c t e d . 4. The r e l i a b i l i t y o f t h e 2- by 2 - f t f i r e t e s t w i l l b e f u r t h e r examined by c a r r y i n g o u t a s e r i e s o f r e p e a t t e s t s w i t h n o t o n l y t h e 2- by 2 - f t t a n k b u t a l s o w i t h a 3- by 3 - f t t a n k a n d a 1 0 - by 1 0 - f t t a n k . I t i s hoped. t h a t c o m p l e t i o n o f t h e c o n t e m p l a t e d i n v e s t i g a t i o n w i l l l e a d t o a t e s t p r o c e d u r e t h a t may be c o n s i d e r e d e i t h e r a s a r e p l a c e m e n t o r a n a l t e r n a t i v e f o r t h a t g i v e n i n JFMC S p e c i f i c a t i o n No. 260.00. REFERENCES 1. J o i n t F i r e M a r s h a l s Committee S p e c i f i c a t i o n No. 260.00 F i r e e x t i n g u i s h i n g a g e n t

-

Foam l i q u i d (Mechanical A i r f o a m ) , Feb. 1 2 , 1958, 1 2 p . J o i n t Army-Navy S p e c i f i c a t i o n , JAN-C-266. N a t i o n a l F i r e P r o t e c t i o n A s s o c i a t i o n S t a n d a r d No. 11

-

1960, Foam E x t i n g u i s h i n g Systems. m v e , R.L. and H.B. P e t e r s o n , Naval R e s e a r c h L a b o r a t o r y R e p o r t 3725, Nashington,

D.C.,

Aug. 23, 1950, 89p.

Shoub, H., T. G. Lee a n d J.V. Cameron. N a t i o n a l Bureau of S t a n d a r d s B.M.S. R e p o r t 150. J u n e

1 4 ,

1957.

FdcGuire, J . H . a n d H. W r a i g h t , J o u r n a l o f S c i e n t i f i c I n s t r u m e n t s , v o l . 37, p. 1 2 8 , A p r i l 1960.

I

E X P A N S I O N R A T I O = 12 R A T E = 0 . 0 3 0

-

7 5 10 15

2 5 PER CENT DRAINAGE T I M E , MIN

F I G U R E I

C O N T R O L Q U A N T I T Y A S A F U N C T I O N O F D R A I N A G E T I M E A T C O N S T A N T

N I- F I G U R E 2 CONTROL Q U A N T I T Y A S A F U N C T I O N O F E X P A N S I O N R A T I O A T CONSTANT D R A I N A G E T l M E LL

>

0.15 a w W [L - LL A 0 a t- Z

2

0 . 1 0

P

0 W a

-

3 0 W [L Z 0 - I- 0 - 0 5 3 A 0 V) LL 0 > I- - I- Z

3

0 0

I

I

I

I

1

I

I

2 5 PER CENT DRAINAGE TIME = 4 MIN

RATE = - 0.0 3 0 X o 0 . 0 3 3

-

& cC 4 0 . 0 4 2 -4.075

-

-

----

--"0.058- 0 2 4 6 8 10 12 14 16 I 8 20 < EXPANSION RATIO

I

I I

.

EXPANSION = 6

25 PER CENT DRAINAGE TIME, MIN

F I G U R E 3

C O N T R O L Q U A N T I T Y A S A F U N C T I O N O F DRAINAGE TIME A T C O N S T A N T S O L U T I O N R A T E

FIGURE 4

CONTROL QUANTITY AS A FUNCTION OF SOLUTION RATE AT CONSTANT DRAINAGE TIME

'U 0 . 1 5 I-

?;

_-1

a

w

W LT

-

LL 1 0 Oz

5

_0.10- 0 0 0 I- n W Ir 3 0 W Oz 0 . 0 5

-

I- 3 1 0 m LL 0 t I-

-

I-

z

a 3 0 -

o

SOLUTION RATE OF APPLICATION. G A L / M I N / F T ~

-

I

I

I

I

I

I

2 5 _{PER CENT DRAINAGE TIME = 4 MIN}

EXPANSION = 6

-

18 10

'4.

\ " 4 \ 12 X-x-+-x-

-

2.-

I

I

I

0 0.01 0 . 0 2 0 . 0 3 0 . 0 4 0.05 0.06 0 . 0 7 0 . 0 8

FIGURE 5

CONTROL QUANTITY AS A FUNCTION OF SOLUTION RATE AT CONSTANT EXPANSION RATIO

N I-

t

-I

""=

a

t3

w'

oz

-

LL J 0 a I-

E

0.10 0

e

n w oz

-

3 O W oz z

O

0.05 C 3 J 0 v, LL 0 > I-

-

I-

z

a

3 0 0 ₀

I

I

DRAINAGE = 20 MIN

-

10 MIN 2 MIN 4 bMIN i a -, " -/

-

-

-

0.01 0.02 0.03 0-04 0.05 0.06 0.07 0.08

r~ 0.15 I- LL \ a (3 W [L

-

LL -J 0 [L 0.10 z 0 0 0 t- n W

cr

3 0 W [L z _{0 . 0 5} 0

-

I- 3 -I 0 v, LL 0 > k

-

k z a 3 0 0 F I G U R E 6 C O N T R O L Q U A N T I T Y A S A F U N C T I O N O F E X P A N S I O N R A T I O A T C O N S T A N T S O L U T I O N R A T E 0 2 4 6 8 10 12 14 16 18 i

I

I

I

I

DRAINAGE = 2 0 MIN 7 -

SOLUTION R A T E OF APPLICATION = 0.058 GAL/MIN/FT~

EXPANSION RATIO