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Development of a 4-ft corner wall fire test apparatus

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A c o r n e r w a l l t e s t a p p a r a t u s 4 by 4 by 4 f t was c o n s t r u c t e d t o e v a l u a t e t h e r o l e o f f a c t o r s s u c h a s f i r e e x p o s u r e magnitude and

geometry, and t h e confinement o f h o t g a s e s i n t h e c e i l i n g a r e a , i n flame p r o p a g a t i o n by b u i l d i n g m a t e r i a l s . I t was i n t e n d e d t h a t t h i s a p p a r a t u s b e t h e f o r e r u n n e r o f an 8 - f t c o r n e r w a l l t e s t whose d e s i g n was t o b e . s t a n d a r d i s e d . E . x p l o r a t o r y t e s t s w i t h f i b r e b o a r d r e v e a l e d t h a t f l a m e h e i g h t and h e a t l o s s e s from t h e u p p e r g a s l a y e r e x e r t e d a s t r o n g i n f l u e n c e on t h e r a t e o f flame p r o p a g a t i o n . S e v e r a l p l a s t i c foam i n s u l a t i n g m a t e r i a l s were a l s o t e s t e d ; t h e r e s u l t s were c o n s i s t e n t w i t h t h o s e o f p r e v i o u s l y r e p o r t e d 8 - f t c o r n e r t e s t s . Ottawa November 1976 C

.

B. Crawford D i r e c t o r , D R R / N R C

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DEVELOPMENT OF A 4-FT CORNER WALL FIRE TEST APPARATUS by

M.V. DISouza and

J.H.

McGuire

INTRODUCTION

It is well known that, where most plastic foams are concerned, the ASTM E-84 (ULC S102) flame spread test gives anomalous results (1,2).

Experience with actual fire conditions demonstrates that plastic foams do not conform with the merit sequence established for conventional materials.

The concept of a single flammability rating system for both plastic foam and more conventional materials may no longer be tenable because under some circumstances a plastic foam can appear more flammable than some more conventional material, whereas under other circumstances the reverse can prevail. A comparison of E84 results with those given by various burn tests that have been carried out to date illustrates this possibility.

One school of thought regards differences in thermal inertia

(pl-oduct of thermal conductivity, density and specific heat) of surfaces adjacent to the specimen to be highly significant. Others discuss

chemical aspects and the feature that the effective surface area of a foam is much greater than that of a conventional material. It is clear that there is no real understanding of plastic foam flammability.

Pending proper understanding of the issue, interim test methods must be developed to assess the hazard of plastic foams under

unfavourahle circumstances. These methods would involve (unlike E84 tunnel conditions) arrangements in which all participating surfaces have a low thermal inertia.

The corner wall, employing a configuration formed from the intersection of two adjacent walls and a ceiling, is well suited to satisfying some of these requirements. It is a critical configuration because it ensures near maximum exposure of materials under test to heat by conduction, convection and radiation. Although complete room

enclosures are preferable because heat loss to the surrounding area is reduced, high running costs and poor visibility are major disadvantages.

Because the corner wall test is not standardised, wide variations exist in the type and size of the initiating fire source and in the

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geometries used by involved laboratories (2-6). A ceiling height of 8 ft is most commonly used, although Factory Mutual has cxamincd a ceiling 25 ft high in reproducing an industrial environment. Wall lengths have varied from 2 to 50 ft, and ignition sources have includcd wood cribs, plasticised paper milk cartons, kraft paper and gas burners. PRESENT STUDY

Exploratory work on a corner wall apparatus 8 by 8 by 8 ft, with a truncated ceiling, was begun at DBR/NRC in 1969, in the context of conventional materials, to gain an insight into the significance, under fairly realistic fire conditions, of tunnel flame-spread ratings. This previous arrangement was modified by the addition of a canopy 2 ft deep

(7), combining the advantages of a clear unobstructed view during a test, offered by the corner wall test, and the confinement, albeit partial, of hot gases in the ceiling area, favoured by the room

enclosure test. In all, more than 80 tests were run with 3 variety of

lining materials, lining configurations and fire sourccs.

Based on the results of these initial tests, a proposed standard configuration for a corner wall test was drawn up comprising a ceiling height of 8 ft and area of 8 by 8 ft. However, in an effort to reduce developmental costs, scale modelling was considered a necessary

intermediate step to resolve uncertainties such as fire exposure magnitude, instrumentation location, the need for canopy lining, and material rating criterion. Moreover, if carefully designcd, the scale model could be used as a preliminary screening test.

This paper reports the work conducted during this second phase of the corner wall program. The scaling requirements are set out, the apparatus described and experimental results presented, comparing where possible the performance of the scale model with that of the prototype, full-scale apparatus of 1973.

DESCRIPTION OF TEST APPARATUS (a) Test Compartment

Experimental fire studies involving scaling techniques have usually employed models that are 1/4-scale or less of the test to be simulated (8, 9). At the same time, a study of fire in corridors by McGuire (10) has shown that the contribution of floor coverings to

flame propagation as compared to that of ceiling linings is (i) very small for tests with a ceiling height of 8 ft, (ii) substantial for tests with a ceiling height of 2 ft, and (iii) almost as important for tests with a ceiling height of 1 ft.

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Thus, model b e h a v i o u r was n o t r e p r e s e n t a t i v e o f a f u l l s c a l e c o r r i d o r when a c e i l i n g h e i g h t o f 8 f t was s i m u l a t e d by 1 f t and h a r d l y s o when t h e model h e i g h t was i n c r e a s e d t o 2 f t .

Such s m a l l s c a l e s were t h e r e f o r e r e j e c t e d f o r t h e p r e s e n t s t u d y . A s c a l e f a c t o r o f one h a l f was a d o p t e d i n t h e hope t h a t i t would g i v e b e t t e r r e p r e s e n t a t i o n o f t h e f u l l s c a l e w h i l e s t i l l b e i n g s m a l l enough t o r e a l i z e s a v i n g s i n o p e r a t i n g c o s t s .

The t e s t compartment i s shown i n F i g . 1 . I t was made from l o w - d e n s i t y (45 l b / f t 3 ) a s b e s t o s cement b o a r d (ACB) 1 / 2 - i n . t h i c k , b o l t e d t o a n a n g l e i r o n frame. The canopy was 1 8 - i n . d e e p a l l a r o u n d , w i t h a r e c e s s measuring 6 by 18 i n . c u t i n one s i d e t o s i m u l a t e t h e t o p o f a doorway. The c e i l i n g was t o p p e d w i t h 22 SWG s t e e l c c 1 l u l : l r f l o o r d e c k i n g f o r r i g i d i t y . For t h e p u r p o s e of i d c n t i f i c ; l t i o n , t h e two w : l l l s were l a b e l l e d A and B, and t h e c e i l i n g C , a s shown i n F i g . 1 .

( h ) I g n i t i o n S o u r c e

S e v e r a l c e l l u l o s i c f u e l s o u r c e s and a n a t u r a l g a s b u r n e r were used i n t h e o r i g i n a l NRC c o r n e r t e s t s . Although maximum g a s

t e m p e r a t u r e s f o r t h e two s o u r c e t y p e s were s i m i l a r , t h e c e l l u l o s i c f i r e s d e v e l o p e d f a s t e r g i v i n g a more i n t e n s e e x p o s u r e i n t h e i n i t i a l s t a g e s o f a t e s t . Gas b u r n e r s a r e t o b e p r e f e r r e d f o r a s t a n d a r d t e s t b e c a u s e t h e i r m a n u f a c t u r e and performance a r e e a s i l y r e p r o d u c i b l e . V a r i a t i o n s i n b u r n i n g r a t e can a l s o b e a c h i e v e d s i m p l y by c o n t r o l l i n g g a s flow r a t e s . I t i s p o s s i b l e t o program t h e g a s flow r a t e t o a b u r n e r t o r e p r o d u c e a g i v e n t e m p e r a t u r e p r o f i l e , b u t Nadeau e t a 1 (8) found i t n e c e s s a r y t o i n c l u d e a s e r i e s o f b a f f l e s and r e f l e c t i v e s u r f a c e s i n model t e s t i n g t o e f f e c t n good match w i t h p r o f i l e s from a f u l l s i z e a p p a r a t u s . For r e a s o n s o f s i m p l i c i t y , a n n t u r a l g a s b u r n e r o f c o n s t a n t h e a t

o u t l n ~ t r:rtc was chosen f o r t h i s i n v e s t i g:iti on.

'I'hc I'ropcr clcsign o f ;In i g n i t i o n s o u r c e f o r model t e s t i n g r c c l u i r c s t 1 i ; l t gas t e m p e r a t u r e s and h e a t f l u x e s i n t h e modcl b e

s i m i l a r t o t h o s e i n t h c f u l l s i z e t e s t . 'Two s c a l i n g c r i t e r i a t o be s a t i s f i e d a r c ( i ) f l a m e h e i g h t s i m i l a r i t y and [ i i ) c o n s t a n t h e a t i l l p t i t r a t e p e r u n i t s u r f a c e a r e a o f t e s t m a t e r i a l . To a f i r s t o r d e r of a p p r o x i m a t i o n , c o r n e r w a l l t e s t f i r e s c o u l d be c l a s s e d a s d i f f u s i o n f l a m e s b u r n i n g i n a n u n c o n f i n e d a t m o s p h e r e . Fuel v e l o c i t i e s a t t h e s u r f a c e a r e n o r m a l l y q u i t e low ( < 8 . 0 i n . / s e c ) , s o t h a t buoyancy f o r c e s w i l l i n f l u e n c e f l a m e h e i g h t . Using s i m p l e d i m e n s i o n a l a n a l y s i s , Thomas e t a 1 (11) g i v e t h e f o l l o w i n g f u n c t i o n a l e q u a t i o n f o r s u c h a flow system:

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where R i s t h e flame h e i g h t above t h e b u r n e r s u r f a c e , D i s a

c h a r a c t e r i s t i c dimension of t h e b u r n e r , Q i s t h e v o l u m e t r i c flow r a t c o f t h e gaseous f u e l , g i s t h e g r a v i t a t i o n a l c o n s t a n t , B i s t h c

c o e f f i c i e n t of expansion of t h e g a s e s and AT i s t h e e x c e s s t e m p c r a t u r c i n t h e f l a m e . For a g i v e n f u e l - a i r system, i t may b e assumed t h a t mean flame t e m p e r a t u r e s and g a s c o n c e n t r a t i o n s a t t h e flame t i p a r e

independent o f t h e g a s flow r a t e and b u r n e r s i z e , s o t h a t E q . ( I ) r e d u c e s t o :

An e m p i r i c a l r e l a t i o n s h i p between t h c two q u a n t i t i e s i n E q . (2) was determined by measuring f l a m e h e i g h t s from t h r c e g c o m c t r i c n l l y s i m i l a r b u r n e r s w i t h d i a m e t e r s o f 1 1 , 7 , and 4 i n . The d c s i g n o f t h c s e b u r n e r s was based on t h e performance o f t h c 1 2 - i n . cube-shapcd snnd- b u r n e r used i n some e a r l i e r NRC t c s t s . I ~ x p c r i m c n t s wcrc conductcd i n t h e open atmosphere and b o t h t h e 4- and 8 - f t compnrtnlcnts, w i t h t h c b u r n e r s p l a c e d d i r e c t l y a g a i n s t t h e t e s t c o r n c r . The r e s u l t s shown i n F i g . 2 a r e approximated by:

Flame h e i g h t s i m i l a r i t y r e q u i r e s t h a t - - - C o n s t a n t L

where L i s a c h a r a c t e r i s t i c dimension o f t h e t e s t compartment. The second s c a l i n g c r i t e r i o n p r e s c r i b e s t h a t :

= C o n s t a n t

L~

Thus, e l i m i n a t i n g

6

and g i v e s :

The 1 1 - i n . d i a m e t e r b u r n e r was deemed s u i t a b l e f o r u s e i n t h e proposed 8 - f t c o r n e r a p p a r a t u s s o t h a t , w i t h t h e s c a l e f a c t o r 1 / 2 , t h e model b u r n e r d i a m e t e r was d e t e r m i n e d a s 8 3/4 i n . F i g . 3 ( a ) shows t h e f i n a l d e s i g n which was used i n a l l 4 - f t c o r n e r w a l l t e s t s e x c e p t where n o t e d .

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The ignition exposures selected for the 4-ft corner tests were 625, 1250 and 1875 Btu/min, corresponding to 2500, 5000 and 7500 Btu/min for the 8-ft corner tests, as given by

Eq.

(5). The calorific value of the gas used was approximately 1000 ~ t u / f t ~ . The performance of the

8 3/4 in. burner is listed in Table 1 and included in Fig. 2.

The fuel-handling system was equipped with a variable area flow meter, a flow control valve, a solenoid operated check valve and a spark

igniter. The time from fuel-on to full-flame height was reduced by minimizing volumes downstream of the check valve and by gas-line and burner purging prior to a test. Typically, the delay time at 0.625 cfm was 0.07 min.

INSTRLIMENTAT ION

Ten thermocouples of 24 SWG (.022 in.) chromel-alumel wire were used to measure gas and flame temperatures at the locations shown in Fig. 4. Initially, the thermocouple beads were positioned 1 in. away from the test material surface after the lead wires had been bent to follow expected isotherms to reduce losses. This arrangement was

inconvenient and was rejected in favour of straight-through probes when a comparative test showed that conduction errors were insignificant, and smaller than those associatcd with delays given by larger beads with higher thermal inertia. An eleventh thermocouple was positioned 1 in. below the doorway to measure exit gas temperatures.

A water-cooled, shielded, gold-disc radiometer, of the type

described by McGuire and Wraight ( 1 2 ) , provided continuous monitoring of the thermal radiation incident on the floor of the compartment (Fig. 4). The unit was calibrated up to 2.8 w/cm2. A response time of 10 sec for 95 per cent true value was claimed.

Video and two separate audio commentary tape recordings were made of most tests, providing three independent assessments of events. TEST MATERIALS

Thc corncr was formed from three 4- by 4-ft panels of the test mnteri:il, which werc positioned to ensure tight joints and bolted to the ns1,estos ccmcnt board lining. Thirteen bolts were used for the ceiling, :lncl n i n c for tach of thc two walls.

At the outset, n total of 14 experiments were run with untreated fibrchonrd 7/16 in. thick, having a flame spread rating (FSR) of 70, to asscss thc pcrformance of thc 4-ft corner wall test apparatus in terms of geometry and igniting source exposure. These were followed by tests on bare and foil-covered polyurethane boardstock and polystyrene bead- board, 1 in. thick, aimed at arriving at a suitable criterion for rating materials. Table 2 lists the materials tested with their relevant

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TEST DETAILS

A l l t e s t s were conducted i n a c u b i c burn room o f s i d c 40 f t .

A s i n g l e d o o r , s i t u a t e d 40 f t away from t h e a p p a r a t u s , and a 6000 cfm c a p a c i t y , c e i l i n g - m o u n t e d e x h a u s t f a n p r o v i d c d t h e n e c c s s a r y a i r srrly)l y and gas v e n t i l a t i o n .

T e s t s were t e r m i n a t e d soon a f t e r flames i s s u e d from under t h e canopy o r a t t h e end o f 10 min, whichever came f i r s t . A 5 - s e c b u r s t o f a f i n e s p r a y o f w a t e r from a garden hose was s u f f i c i e n t t o e x t i n g u i s h a l l f i r e s r e p o r t e d .

The c o n d i t i o n o f t h e m a t e r i a l a f t e r t h e t e s t was c a r e f u l l y n o t e d and s k e t c h e d . The t a p e r e c o r d i n g s were a n a l y s e d f o r t i m e s f o r ( I )

m a t e r i a l i g n i t i o n ( 2 ) f l a m e s t o r e a c h c e i l i n g , (3) c e i l i n g i g n i t i o n , ( 4 )

flame p r o p a g a t i o n a c r o s s c e i l i n g t o canopy ( l a t e r a l ) and doorway ( d i a g o n a l ) , and (5) flames t o emerge from under canopy o r doorway. RESULTS AND DISCUSSION

E x p l o r a t o r y T e s t s ( R e s u l t s l i s t e d i n T a b l e 3)

(a) G e n e r a l . F i b r e b o a r d was chosen f o r t h i s s e r i e s o f t e s t s because

i t s b e h a v i o u r i n f i r e s i s f a i r l y p r e d i c t a b l e from t h e r e s u l t s o f t h e E-84 t u n n e l t e s t . I t s d i s t i n c t i v e f e a t u r e i n t h e 4 - f t c o r n e r w a l l t e s t w i t h a round b u r n e r was t h a t , f o l l o w i n g w a l l i g n i t i o n , a narrow f u n n e l o f flame c o n f i n e d t o t h e v e r t i c a l AB c o r n e r proceeded

r e l a t i v e l y s l o w l y up t h e c o r n e r u n t i l it r e a c h e d and i g n i t e d t h e c e i l i n g . P r o p a g a t i o n o f t h e f i r e a l o n g t h e two h o r i z o n t a l c o r n c r s

(AC and BC) and a c r o s s t h e c e i l i n g was g e n e r a l l y f a s t e r , and was accompanied by a more r e s t r a i n e d p r o g r e s s i o n o f flame from t h e s c c o r n e r s down t h e two w a l l s . Flames emerged from under t h e canopy s h o r t l y t h e r e a f t e r , a t t i m e t 2 .

The AB c o r n e r and a small a r e a around t h e ABC j u n c t i o n were b a d l y burned and had a f l a k e d a p p e a r a n c e . The r e m a i n d e r o f t h e c e i l i n g and t h e t o p p a r t o f t h e w a l l s , above a l i n e drawn from t h e b u r n e r t o t h e canopy, were d i s c o l o u r e d and c h a r r e d on t h e s u r f a c e . Below t h i s l i n e t h e m a t e r i a l was u n b u r n t .

U n f o r t u n a t e l y , t e s t s r u n on f i b r e b o a r d i n t h e o r i g i n a l 8 - f t c o r n e r w a l l d i d n o t match t h e c o n d i t i o n s t e s t e d h c r e .

A " f l a s h o v e r " t i m e o f 2.00 min was r e c o r d e d from a c o r n e r l i n e d p a r t i a l l y w i t h f i b r e b o a r d o f FSR 97, and i g n i t e d by a K r a f t p a p e r s o u r c e , a p p r o x i m a t e l y r a t e d a t 1760 Btu/min (440 Btu/min

e q u i v a l e n t ) . T h i s r e s u l t i s comparable w i t h t 2 from t e s t No. 3 . ( b ) R e p e a t a b i l i t y . Three t e s t s (Nos. 2 , 3 , 10) were r u n w i t h t h e

0.625 cfm e x p o s u r e . I f t h e b u r n e r i g n i t i o n problems e n c o u n t e r e d i n t e s t 2 a r e i g n o r e d , t e s t r e p e a t a b i l i t y i n t e r m s of t i s f a i r l y

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good. A mean time o f 2.05 min was r e c o r d e d w i t h a s t a n d a r d d e v i a t i o n o f . 0 . 0 4 min. Gas t e m p e r a t u r e s a t l o c a t i o n C (Tc2) and i n t h e doorway ( T D w ~ ) and t h e t i m e a t which TDW exceeded 1000°F were a l s o r e p r o d u c i b l e , b u t T B ~ and R2 were n o t .

( c ) Exposure magnitude. A s e x p e c t e d , i n c r e a s e s i n e x p o s u r e magnitude r e d u c e d t 2 . However, i t s e f f e c t s on t e m p e r a t u r e were minimal a t t h e l o c a t i o n s n o t e d above. Over t h e r a n g e t e s t e d

(d) Flame H e i g h t . The i n f l u e n c e o f flame h e i g h t on b u r n i n g p a t t e r n was i n v e s t i g a t e d u s i n g t h c 4 - i n . b u r n e r . For a g i v e n f l o w r a t e , an i n c r e a s e o f a p p r o x i m a t e l y 53 p e r c e n t i n t r u e f l a m e h e i g h t ( e x c l u d i n g b u r n e r h e i g h t ) s h o r t e n e d t 2 by 24 p e r c e n t . In

c o n t r a s t , f o r a g i v e n flame h e i g h t , a r e d u c t i o n o f 38 p e r c e n t i n Q i n c r e a s e d t 2 by o n l y 1 3 p e r c e n t . The r e s u l t s may b e p r e d i c t e d from t h e r e l a t i o n s h i p o b t a i n e d by combining Eqs. (3) and ( 7 ) , namely:

a s shown i n F i g . 5. Gas t e m p e r a t u r e s were a b o u t t h e same f o r a l l t h r e e t e s t s (Nos. 3 , 8 , 9 ) .

( e ) E f f e c t o f canopy. In t e s t No. 15, t h e canopy was removed c o m p l e t e l y . The f l a m e s r e a c h e d t h e e x t r e m i t i e s o f t h e AC, BC

c o r n e r s a t 1 . 3 4 min a s i n t e s t No. 3 , and t h e n p r o g r e s s e d v e r y s l o w l y from t h c s c c o r n c r s t h r o u g h t h e unburned m a t e r i a l r e a c h i n g t h e "doorway" p o s i t i o n a t 2.60 min. A comparison o f t h i s t e s t and t c s t No. 3 showed t h a t r e d u c t i o n o f h e a t l o s s from t h e u p p e r p o r t i o n o f t h c e n c l o s u r e , by confinement o f t h e h o t g a s e s , e x e r t e d a s t r o n g j n f l u c n c e on flame p r o p a g a t i o n a c r o s s t h e c e i l i n g . T h i s a s p e c t was d e m o n s t r a t e d a g a i n i n t e s t No. 7 when t h e u p p e r l a y e r h e a t l o s s e s were c u r t a i l e d f u r t h e r by l i n i n g t h e canopy a s well w i t h t h e t e s t m a t e r i a l . The f i r e produced was more i n t e n s e and s h o r t e n e d t 2 t o

1.55 min.

A n a t u r a l e x t e n s i o n o f t h i s s e r i e s of t e s t s was t o e x t e n d t h e canopy t o t h e f l o o r , t h u s s i m u l a t i n g a room w i t h a doorway. A b l a c k i r o n o x i d e c o a t i n g was a p p l i e d t o t h e s u r f a c e o f t h e ACB p a n e l s t h a t were added, t o conform w i t h t h e e m i s s i v i t y o f t h e r e g u l a r canopy. The two ncw w a l l s were u n l i n e d . S u r p r i s i n g l y , t 2 remained a t 2.00 min ( a s i n t e s t No. 3 ) , i n d i c a t i n g t h a t a c o r n e r w a l l w i t h canopy

was n s u f f i c i e n t l y a c c u r a t e r e p r e s e n t a t i o n o f a room, a t l e a s t f o r f i h r c b o a r d

.

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( f ) F l o o r l i n i n g . Sand was used a s f l o o r l i n i n g i n a l l f i b r e b o a r d t e s t s . However, no e f f e c t on t-, was n o t e d when ns1)estos p a p e r

L

.

.

was s u b s t i t u t e d f o r t h e s a n d , i n t e s t No. 6 . A s b e s t o s p a p e r was

used i n a l l foam t e s t s .

(g) Line b u r n e r . The t e n d e n c y o f p o l y s t y r e n e foam t o s h r i n k away from a flame makes t h e u s e o f a c i r c u l a r b u r n e r i m p r a c t i c a l , e s p e c i a l l y because t h i s m a t e r i a l i s known t o m e l t , d r i p and burn a s n pool

f i r e on t h e f l o o r . Rose (7) found t h a t e x c e l s i o r , d i s t r i b u t e d e v e n l y a l o n g t h e bottom o f t h e w a l l s , was c a p a b l e o f p r o d u c i n g a " f l a s h o v e r " s i t u a t i o n . In t h i s r e g a r d , t h e l i n e b u r n c r shown i n F i g . 3 ( b ) was developed. T e s t s showed t h a t a s e t o f 28 f u e l h o l e s o f d i a m e t e r 0.077 i n . on a p i t c h o f 2.5 i n . was c a p a b l e o f

r e p r o d u c i n g t h e r e s u l t s o f t h e 8 3/4 i n . round b u r n e r . The l i n e b u r n e r was found t o b e s u s c e p t i b l e t o d r a f t s .

(h) C o n c l u s i o n s . The e x p l o r a t o r y t e s t s d e m o n s t r a t e d t h e performance c h a r a c t e r i s t i c s o f t h e 4 - f t c o r n e r w a l l a p p a r a t u s . The r a n g e o f f u e l flow r a t e s chosen produced a s u f f i c i e n t l y l a r g e v a r i a t i o n i n

t 2 f o r f i b r e b o a r d , t o make measurement p r a c t i c a l . Flame h e i g h t and h e a t l o s s e s from t h e u p p e r g a s l a y e r e x e r t e d a s t r o n g i n f l u c n c c on t h e r a t e o f flame p r o p a g a t i o n . Thc 8 3/4 i n . b u r n c r and t h c 1 8 - i n . canopy, u n l i n e d , a d e q u a t e l y f u l f i l l e d t h e r e q u i r c n c n t s o f a model c o r n e r w a l l t e s t .

P l a s t i c Foam T e s t s

( a ) G e n e r a l . Both t h e 0.625 and 1.875 cfm b u r n e r f u e l i n g r a t e s were t e s t e d when s u f f i c i e n t m a t e r i a l was a v a i l a b l e , s o a s t o e n l a r g e t h e d a t a b a s e . T a b l e 4 summarizes t h e r e s u l t s o b t a i n e d .

(b) F o i l - c o v e r e d P o l y u r e t h a n e Foam. The b u r n i n g p a t t e r n s of t h e s e foams were e s s e n t i a l l y t h e same ( M a t e r i a l s 2 , 3 , 4 ) . Flame p r o p a g a t i o n was dependent on whether t h e h e a t g e n e r a t e d by t h e s o u r c e f i r e and t h e b u r n i n g m a t e r i a l was s u f f i c i e n t t o m e l t o r b u r n t h e f o i l p r o t e c t i o n and expose t h e flammable foam below. A t t h e s t a r t o f t h e t e s t , b u r n i n g o f t h e m a t e r i a l below t h e f o i l formed g a s b l i s t e r s on t h e s u r f a c e which were r e l e a s e d from t i m e t o t i m e a s t h i c k smoke. Wall i g n i t i o n d u r i n g t h i s i n i t i a l s t a g e was c o n f i n e d t o exposed foam, e i t h e r on t h e edge o f t h e specimen o r a t t h e r e t a i n i n g b o l t s . Thcsc s o u r c e s produced c o p i o u s amounts o f smoke b u t d i d n o t c o n t r i b u t e s i g n i f i c a n t l y t o t h c p r o g r e s s i o n o f flame up t h e AB c o r n e r . T h i s l a t t e r a c t i o n o c c u r r e d p r i m a r i l y by flame p e n e t r a t i o n o f t h e f o i l c o v e r i n g . A f t e r i g n i t i n g t h e c e i l i n g , f l a m e s s t a r t e d t o move a l o n g t h e AC, BC c o r n e r s and a c r o s s t h e c e i l i n g . However, t h e d i m i n i s h i n g i n f l u e n c e o f t h e b u r n e r a t t h i s s t a g e was compounded by t h e t e n d e n c y o f t h e f o i l c o v e r i n g on t h e c e i l i n g t o s e p a r a t e from t h e m a t e r i a l a s t h e i n i t i a l l a y e r s burned o r t h e m a t e r i a l s h r a n k , t h u s p r o v i d i n g an i n s u l a t i n g l a y e r

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o f gas between t h e f o i l and t h e p a r t i a l l y burned m a t e r i a l . A t

t i m e s f l a s h e s o f flame were v i s i b l e t h r o u g h t h e t h i c k smoke,

t r a v e l l i n g a c r o s s t h e c e i l i n g . Where flames were a b l e t o r e a c h t h e canopy c o n s i s t e n t l y , b i l l o w s o f smoke and flame were n o t i c e d i n t h e u p p e r p a r t o f t h e e n c l o s u r e b e f o r e t h e f l a m e s emerged from u n d e r t h e canopy.

The most s e v e r e l y damaged a r e a s were t h e A B c o r n e r and about 112 t h e l e n g t h o f t h e AC and BC c o r n e r s . Here t h e foam had been burned c o m p l e t e l y w i t h s i g n s o f s h r i n k a g e . The f o i l was u s u a l l y t o r n and p i t t e d b e c a u s e o f m e l t i n g . I n a d j a c e n t a r e a s t h e f o i l was d i s c o l o u r e d b u t i n t a c t . Beneath i t , o n l y t h e s u r f a c e l a y e r s o f t h e m a t e r i a l were b u r n e d , t h e e x t e n t o f which d e c r e a s e d w i t h d i s t a n c e from t h e b u r n e r .

( c ) Bare P o l y u r e t h a n e Foams. M a t e r i a l s 2 , 3 , 4 were a l s o t e s t e d w i t h t h e f o i l s t r i p p e d o f f t h e exposed f a c e s . The b u r n i n g p a t t e r n f o r t h e s e and 0th;; n o r m a l l y b a r k foams ( 5 , 6) were a l s o - e s s e n t i a l l y t h e same. Flame p r o p a g a t i o n was v e r y r a p i d up t h e A B and a l o n g t h e AC, BC c o r n e r s , t o g e t h e r w i t h heavy smoke f o r m a t i o n . A t t h i s p o i n t flames t r a v e l l e d down w a l l s A and B from t h e s e c o r n e r s .

Billowing o f flame was noted a g a i n , p r i o r t o emerging from t h e canopy.

Almost t h e e n t i r e w a l l s and c e i l i n g were c h a r r e d o r s c o r c h e d . M a t e r i a l s 2 , 4 and 5 showed s i g n s o f s h r i n k i n g and b u r n i n g i n

l a y e r s t h a t b r o k e away t o expose f r e s h m a t e r i a l . Beneath t h e s e c h a r l a y e r s and i n a d j a c e n t s c o r c h e d a r e a s t h e foam had darkened t o a golden brown c o l o u r , t h e d e g r e e o f which r e d u c e d w i t h d i s t a n c e from t h e b u r n e r . M a t e r i a l s 3 and 5 a l s o showed s i g n s o f s h r i n k a g e b u t t h e unburned m a t e r i a l below was exposed t o t h e flame t h r o u g h c r a c k s and f i s s u r e s i n t h e u p p e r c h a r l a y e r s .

(d) I s o c y a n u r a t e Foam. Only one such foam was t e s t e d , which had a v e r y low FSR o f 23 ( M a t e r i a l 7 ) . M a t e r i a l i n t h e d i r e c t p a t h o f t h e h e a t flow c h a r r e d and s h r a n k , p a r t i c u l a r l y c l o s e t o t h e b u r n e r . Smoke f o r m a t i o n was moderate t o heavy. O u t s i d e t h i s r e g i o n , t h e specimen d i s t o r t e d and buckled v e r y s e v e r e l y . With t h e l a r g e s o u r c e ( t e s t No. 30) f l a m e s r e a c h e d t h e canopy a l o n g t h e two c o r n e r s b u t d i d n o t emerge from b e n e a t h i t .

(c) P o l y s t y r e n e Foams. When h e a t e d , t h e r e g u l a r g r a d e foams s h r a n k , m e l t e d , r a n down t h e w a l l s and dropped o f f t h e c e i l i n g i n "blobs". The molten s u b s t a n c e on t h e w a l l s i g n i t e d and b u r n e d , t h u s

p r o p a g a t i n g t h e f i r e t o t h e f l o o r . Thick b l a c k smoke was g i v e n o f f . No b u r n i n g o c c u r r e d on t h e c e i l i n g . Although f l a m e s r e a c h e d t h e c e i l i n g by 0 . 7 5 min, t h e r e was no m a t e r i a l i n t h e immediate h e a t zone t o p r o p a g a t e t h e f l a m e . A t 2 . 0 0 min t h e e n t i r e c e i l i n g and t h e upper w a l l s , t o t h e d e p t h o f t h e canopy, were b a r e . The b u l k o f t h e b u r n i n g t o o k p l a c e from t h e s o u r c e c o r n e r outwards a l o n g t h e w a l l s A

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A f t e r a p p r o x i m a t e l y 2 1 / 2 min, m a t e r i a l on t h e f l o o r a l o n g t h e edge o f t h e w a l l s became i n v o l v e d , b u r n i n g s t e a d i l y o u t w a r d s .

By s p r e a d i n g t h e h e a t w i t h a l i n e b u r n e r ( t e s t No. 3 6 ) , b o t h w a l l s were i n v o l v e d v e r y q u i c k l y . Oncc a g a i n , whcn f l a m e s r c a c h c d t h e c e i l i n g a t 1 . 1 5 min, n o t much m a t c r i s l was l c f t t h c r c t o 1 ~ 1 r n . However, b e c a u s e o f t h c i n t c n s c h e a t b e i n g g c n c r n t c d , i ~ l m o s t ha 1 f t h e f l o o r a r e a was a l i g h t a t t h i s t i m e . Flames from t h e wxl Is emerged from u n d c r t h c canopy a t 2 . 2 8 min.

I n c o n t r a s t , t h c f i r e r e t a r d e d g r a d c was n f f c c t e d o n l y w i t h i n t h e immediate s p h e r e o f i n f l u e n c e o f t h e l i n c b u r n e r f l a m c s . Iivcn though most o f t h e c e i l i n g specimen had s h r u n k , i t d i d n o t f a l l o f f . Over t h e b u r n e r t h e foam had m e l t e d away b u t remained suspended

from t h e r e m a i n i n g m a t e r i a l , e x p o s i n g t h e a s b e s t o s b o a r d t o a r a d i u s o f 2 f t . T h e r e was no b u r n i n g on t h e c e i l i n g o r f l o o r and v e r y l i t t l e on t h e w a l l s . S i m i l a r b e h a v i o u r was n o t e d i n t h e 8 - f t c o r n e r w a l l t e s t . A " f l a s h o v e r " s i t u a t i o n was provoked o n l y w i t h m a t e r i a l 2 i n . t h i c k , w i t h b o t h t h e r e g u l a r and s e l f - e x t i n g u i s h i n g g r a d e s . ANALYSIS ( a ) Comparison w i t h p r e v i o u s 8 - f t c o r n e r w a l l t e s t s . M a t e r i a l s 5 , 6 and 7 were a l s o t e s t e d i n t h e 8 - f t c o r n e r w a l l t e s t . However, d i r e c t c o m p a r i s o n s o f r e s u l t s a r e l i m i t e d h e c a u s e o f d i v c r s c t c s t c o n d i t i o n s , a s shown i n T a b l e 5 . S i n c e t h e 8 - f t c o r n c r w a l l was n e v e r l i n e d c o m p l e t e l y , t h e c o r r e l a t i o n w i t h t h e 4 - f t c o r n c r w a l l was made v i a t h e exposed s u r f a c e a r e a e x p r e s s e d a s n p e r c e n t a g e o f t h e t o t a l l i n i n g p o s s i b l e . A s mentioned p r e v i o u s l y , t h e s o u r c e s i z e s o f 625 and 1875 Btu/min shown f o r t h e 4 - f t c o r n e r w a l l t e s t c o r r e s p o n d t o s o u r c e s i z e s o f 2500 and 7500 Btu/min f o r an 8 - f t c o r n e r w a l l t e s t . D e s p i t e t h e s e d i f f e r e n c e s , t h e t i m e s l i s t e d i n T a b l e 5 a r e l o o s e l y l i n k e d t h r o u g h Eqs. (5) and (7) a n d , t o g e t h e r w i t h t h e t e m p e r a t u r e s shown, i n d i c a t e a f a i r measure o f agreement between t h e two t e s t a p p a r a t u s e s .

(b) Comparison w i t h Tunnel Furnace R e s u l t s . F i g u r e 6 shows t h e wide s c a t t e r o b t a i n e d by p l o t t i n g FSR, a s g i v e n by t h e ASTM E-84

s t a n d a r d , v e r s u s t 2 . The 1975 e d i t i o n o f t h e N a t i o n a l B u i l d i n g Code o f Canada (13) r e q u i r e s t h a t , where t u n n e l t e s t flame

p r o p a g a t i o n i s more t h a n 10 f t b u t l e s s t h a n 1 9 . 5 f t ( i . e . , E-84 FSR between 55 and 7 8 ) , t h e FSR s h o u l d b e c a l c u l a t e d a c c o r d i n g t o 25 d / t , where d i s t h e d i s t a n c e t r a v e l l e d i n f e e t and t i s t h e t i m e f o r t h i s t r a v e l i n m i n u t e s . A more a c c u r a t e f o r m u l a t i o n would have been 28.21 d / t , which would g i v e a FSR o f 100 f o r

1 9 . 5 f t o f flame t r a v e l i n 5 . 5 min, t h e s t a n d a r d o b t a i n e d w i t h r e d oak f l o o r i n g . When t h i s l a t t e r form i s a p p l i e d , t h e r c s u l t s shown

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on Table 4 as 'Modified FSR' (MFSR) and the plot of Fig. 7 are obtained. The fibreboard test results have been included. Using a least squares method to curve fit the results, the following

approximations were calculated:

Bare foam, large source: MFSR = 59.4

, 1.32

Foil covered foam, large source: MFSR = 172.7

3.60 (10)

t2

Rare foam, small source: MFSR = 192.0/t2 1.08 (11)

The large source produced less scatter when the foil-covered foams were considered separately. The above relationships apply strictly to the 1-in.-thick foams tested. Although the results from the 7/16-in. fibreboard tests comply with Eqs. (9) and (11)

,

this agreement is perhaps fortuitous because the effect of material thickness on flame spread in the corner wall is not known quantitatively.

(c) Temperature and Radiation Measurements. An examination of the gas temperatures at Stations B and C and the doorway, measured at time t2, revealed surprisingly little variation with no trends evident in relation to t2.

l'hc radiation measurements wcrc inconclusivc. The large variations werc probably due in part to thc proximity of the radiometer to thc burner. The vicw factor of thc meter could be affcctcd by debris on the floor although this is unlikely in the pre-flashover period. The slow response of the meter used made it unsuitable for measurements with high FSR foams.

(d) Criterion for rating plastic foams. A practical criterion might be based on elapsed time for a specified event to occur. The simplest one is visual observation of time for flames to emerge from beneath the canopy. This criterion is subject to operator error, which assumes increasing importance as t2 reduces. Further, it does not differentiate between plastic foams below 25 FSR. Nevertheless, the results for polyurethane type foams were encouraging.

Table 6 suggcsts that the time taken for either TB or TC to surlJass a value of 1250°F or 1000°F, respectively, is a good

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method of estimating t2. Rose (7) employed a valuc of 1000°F at a location equivalent to C in this test, whereas Pr~rkcr and I.cc

(9) recommend an average upper gas layer temperature of 1300°F 3 s

a measure of fire severity. It was hoped that a correlation would exist between t2 and the floor level radiation, but results wcrc not reproducible.

CONCLUSIONS AND RECOMMENDATIONS

Results of the 4-ft corner wall test apparatus described in this paper showed fair agreement with available results from earlier 8-ft corner wall tests. The elapsed time for flames to issue from under the canopy t2 was considered a suitable method to rate materials.

A reasonable correlation with tunnel test results was obtained, provided the 25 d/t method of calculating FSR for materials in the 55-78 range, as recommended by the National Building Code of Canada (131, was used. However, the t2 method was dependent on the source sizc and surface condition of the specimen.

In future testing, it is rccomrnended that thc large sourcc bc adopted because it results in reduced expcrirnental scattcr. Thc linc burner performed satisfactorily with polystyrene foam and hence would be suitable for most thermoplastic-type materials where melting precedes ignition. Temperature measurements at the locations specified should be retained; the radiation measurements can be eliminated.

Similar tests will be conducted in a new 8-ft corner wall test apparatus constructed along the lines of the present 4-ft model, to verify the findings of the current investigation.

ACKNOWLEDGEMENTS

Construction of the apparatus and the conduction of tests were carried out by Mr. P. Huot and Mr. R. Lamirande. Their help is gratefully acknowledged.

REFERENCES

1, Cellular Plastic Products, Federal Rcgistcr, FR 30842 (16 CFR Part 4391, Vol. 40, No. 412, July 1975.

2. Williamson, R.B. and Baron, F.M. A Corner Fire Test to Simulate Residential Fires, Journal of Fire and Flammability, Vol. 4, April 1973.

3. Flammability Studies of Cellular Plastics and Other Building Materials used for Interior Finishes, Subject 723, Underwriters'

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4. Fire Test Methods Used in Research at the Forest Products Laboratory, U.S. Dept. of Agriculture, Report No. 1443, Forest Products

Laboratory, Madison, Wisconsin, December 1953.

5. Maroni, W.F. Rigid Cellular Plastic Wall Insulation, Fire Journal, Vol. 66, No. 6, November 1972.

6. Fang, J.B. Fire Buildup in a Room and the Role of Interior Finish Materials, National Bureau of Standards, Technical Note 879, 1975. 7. Rose, A. Fire Testing of Rigid Cellular Plastics, National Research

Council of Canada, Division of Building Research, Internal Report No. 422, Ottawa, September 1975.

8. Nadeau, H.G., Waszeciak, P.H., Zane J. and Gambardella, T. Design and Simulation of the Steiner Tunnel Test (ASTM E-84) and the

Factory Mutual Corner Wall Test, Unpublished report, The Upjohn Company, Donald S. Gilmore Laboratories, North Haven, Conn., September 1974.

9. Parker, W.J. and Lee, B.T. Fire Buildup in Reduced Size Enclosures, National Bureau of Standards Special Publication 411, November 1974. 10. McGuire, J.H. The Spread of Fire in Corridors, Fire Technology,

Vol. 4, No. 2, May 1968.

11. Thomas, P.H., Webster, C.T. and Raftery, M.M. Some Experiments on Buoyant Diffusion Flames, Combustion and Flame, Vol. 5, No. 4, 1961. 12. McGuire, J.H. and Wraight, H. Radiometer for Field Use, Journal

of Scientific Instruments, Vol. 37, April 1960.

13. National Building Code of Canada, 1975, Issued by Associate

Committee on the National Building Code, National Research Council of Cai~ada, Ottawa, NRCC 13982.

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TABLE 1

GAS BURNER PERFORMANCE

Mean Flame Height

Gas Flow, Gas V e l o c i t y , P r e s s u r e Drop, above F l o o r ,

~ t . 3/min i n . / s e c i n . H 2 0 i n . 8 3/4 i n . Dia. Sand Burner

0.625 0 . 3 0 0.081 2 3

1 1 - i n . Dia. Sand Burner

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TABLE 2 TEST MATERIALS

No. M a t e r i a l Type D e n s i t y , ASTb1 E-84, ASTM E-84, Oxygen Index l b i n . / f t 3 FSR Smoke Devld N a t u r a l f i b r e b o a r d P o l y u r e t h a n e foam

-

f o i l c o v e r e d P o l y u r e t h a n e foam

-

f o i l c o v e r e d P o l y u r e t h a n e foam

-

f o i l covered P o l y u r e t h a n e foam

-

b a r e P o l y u r e t h a n e foam - b a r e I s o c y a n u r a t e foam P o l y s t y r e n e - r e g u l a r P o l y s t y r e n e - f i r e r e t a r d e d Nominal t h i c k n e s s - 1 i n . f o r m a t e r i a l s 2-9 and 7/16 i n . f o r m a t e r i a l 1.

*

Values g i v e n f o r foam w i t h f o i l s t r i p p e d o f f .

* *

Values g i v e n f o r f o i l c o v e r i n g i n t a c t and f o i l c o v e r i n g s t r i p p e d o f f , r e s p e c t i v e l y .

(18)

TABLE 3

RESULTS OF EXPLORATORY TESTS WITH FIBREBOARD No. Purpose Source Rate,

cfm Remarks 2 R e p e a t a b i l i t y Round 0.625 2.06 2.30 1700 1565 1135 1.36 2.23 2.13 Ign. l a g 0.30 n i n 3 burner 8 3/4 Dia. 0.625 1.70 2.04 1500 1575 1135 0.87 2.09 1.84 10 0.625 1.80 2.10 1730 1530 1260 1.92 1.95 1 . 8 3 4 F i r e s i z e RB8 3/4 1.250 0.96 1 . 2 0 1740 1625 1270 - 0.93 5 1.875 0.73 0.89 1650 1610 1290 1.10 0.80 0.65 8 Flame h e i g h t R B 4 0.625 1 . 2 0 1.56 1675 1525 1005 1.60 1.45 1.55 Height 31.5 i n . 9 Flame h e i g h t R B 4 0.385 1.75 2.30 1540 1450 1035 1.77 2.15 1.89 Height 24.8 i n . 15 No canopy RB8-3/4 0.625 2.60

-

-

7 Canopy l i n e d 0.625 1.30 1.55 1570 1540 1305 1.23 14 "Room" burn 0.625 1.58 2.00 1800 1550 1145 1.86 1.87 1.68 6 Asbestos paper f l o o r l i n i n g RB8-3/4 0.625 1.57 1.96 1580 1580 1110 1.60 1.88 1 . 6 6 11 Line burnerf 2 8 0.625 1.95 2.02 1830 1450 998 2.97 1 . 7 0 1.90 12 37 0.625 3.44 3.54 1480 1440 1135 1.66 3.48 3.37 13 19 0.424 2.37 2.48 1730 1650 1135 1.03 2.47 2.68 Symbols: t = Time (min. ) S u b s c r i p t s : 1 Flames a t doorway

T = Temperature (OF) 2 Flames under canopy R = Radiation (w/cm2) B Measuring s t a t i o n (Fig. 4) l Line b u r n e r geometry i n terms o f

numbers o f h o l e s each 0.077 d i a .

C Measuring s t a t i o n ( F i g . 4) DW Doorway

(19)

SUMMARY OF PLASTIC FOAM TESTS

T e s t M a t e r i a l Fuel Time, Temperature, Time, R a d i a t i o n Time, AS'IM Modified

No. Flow min O F a t t, min min E-84

cfm 1 2 T ~ 2 T ~ 2 T~~~ T ~ ~ = ~ O O O ~ F R=1.10 -- W 2 FSR FSR cm cm No. 2 - w i t h f o i l - w i t h f o i l - w i t h f o i l - without f o i l No. 3 - w i t h f o i l - w i t h f o i l - w i t h f o i l - without f a i l - w i t h o u t f o i l No. 4 - w i t h f o i l - w i t h f o i l - w i t h o u t f o i l - w i t h o u t f o i l No. 5 No. 6 No. 7 No. 8 No. 9 No. 1 NR: Event n o t r e a c h e d NA: Not a v a i l a b l e LB: Line b u r n e r w i t h 28 h o l e s

(20)

U X L L

k d o E

(21)

Temperature TABLE 6 TEMPERATURE ANALYSIS Range ( O F ) 1140/1740 965/1625 730/1 290 Mean ( O F ) 1476 1315 9114 Std. Dev. (OF) 162.0 173.9 165.7

(22)

2 2 S W G S T E E L I J ' ~ " A S B E S T O S B O A R D C E L L U L A R F L O O R O N B A C K W A L L S A N D D E C K 7 C E I L I N G ( I N S I D E F R A M E 1 W A L L A L 1 / 7 " A S B E S T O S B O A R D O N F L O O R ( I N S I D t F R A M L ) F l G U R t I 4 F 1 C O R N E R W A L L TEST C O M P A R T M E N T f I G U R L 2 E X P C R I M E N T A I B U R N E R F L A M E H E I G H T TEST R E S U L T S 00 100 n 10 I 0.

--

1 I I 1 1 1 1 1 1 I 1 I 1 1 1 1 1 ~ I 1 I I I I I - 7 - - - U N C O N F l NED A T M O S P H E R E - -

-

0 4 " B U R N E R - - V 7" B U R N E R

-

8 314" B U R N E R - A 11" B U R N E R - - -

d

- 7 -

-

-

-

-

-

U N C O N F l N E D - -

-

1. A T M O S P H E R E -

-

- - -

,

1

1

~

8

314" B U R N E R I N 4 ' C W - I I I 1 1 1 1 1 1 I I I 1 1 1 1 1 1 I I I I 1 1 1 1 01 0 L O 1 00 10

(23)

C O A R S E S A N D M E S H S I Z E 8 - 1 2 M E S H 1 4 : I " / A S S O R T E D S I / I C E R A M I C B E A D S - - / , ' 2 2 4 H O L E S , C A C H S I D E , 0 9 6 " D I A E Q U I - S P A C E D F I G U R E 3 l a ) 8 314" D I A S A N D B U R N E R 3 7 H O L E S , , 0 7 7 " D I A E Q U I - S P A C E D , O N 2 1/2" P I T C H . ( 1 8 H O L E S O N E A C H A R M P L U S 1 " I N C O R N E R ) TEST S P E C I M E N 5.18" O . D . C O P P E R CB W A L L 8 F L O O R G A S I N I N S T A L L A T I O N

-

P L A N F I G U R E 3 ( b ) L I N F B U R N E R

(24)

0 G A S T E M P E R A T U R E - 1 " B E L O W C E I L I N G G A S T C M P E R A T U R E - 1 " F R O M W A L L A , 1 9 " 8 3 7 " B E L O W A C B C L l L l N G 0 ( ; A S I I M P I U A I U R E - I " B I L O W I I O O R W A Y 8 C A 5 I 1 M P l R A l U R f - l o ' ' X 7 7 1 7 ' A H O V E A C H t I O O K 3 7 ' I W A L L A

I

C I I L I N G P L A N F I < ; ( l R l 4 I N 5 I R l I M I N I A I I O N I A Y O U I I O K 4 1 1 C O R N I K W A L L 4 t I L I\ t L A M I t i 1 I G H l C O R R E L A T I O N F R O M I I ? I 5 c ' i N I I R U t R L ~ A R l l

(25)

FIGURE

7

MODIFIED FLAME SPREAD

RATING CORRELATION

1 . 0

t 2 , m i n u t e s

FIGURE

6

STANDARD FLAME SPREAD

RATING CORRELATION

Figure

Table  6  suggcsts that the time taken for either  TB  or  TC  to surlJass  a  value of 1250°F or 1000°F, respectively, is a good
TABLE  2  TEST  MATERIALS

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