Modifications to improve operation of the roof test apparatus

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Modifications to improve operation of the roof test apparatus

Crampton, G. P.

NATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BlJlLDlNG RESEARCH

*

ClBR INTERNAL REPORT NO. 507

MODIFICATIONS TO IMPROVE OPERATION OF THE ROOF TEST APPARATUS by George P. Crampton

Checked by: T

.

Z

.

Harma t h y Approved by: L

.

W

.

Gold Date: F e b r u a r y 1986

Prsparsd far: Record P u r p o s e s

ABSTRACT

The r o o f t e s t a p p a r a t u s s p e c i f i e d i n ULC S107-M1980 w a s

t r a n s f e r r e d f r o m Ottawa t o NRC's N a t i o n a l F i r e L a b o r a t o r y l o c a t e d n e a r Almonte, Ont. Q u e s t i o n s were r a i s e d c o n c e r n i n g t h e

p e r f o r m a n c e of t h e a p p a r a t u s w h i c h d i d n o t meet t h e r e q u i r e m e n t s s t a t e d i n t h e s t a n d a r d . T h i s r e p o r t r e c o r d s t h e p r o b l e m s

a s s o c i a t e d w i t h t h e a p p a r a t u s ; t h e t e c h n i q u e s u s e d t o e v a l u a t e t h e p r o b l e m s ; . a n d t h e m o d i f i c a t i o n s made t o improve t h e p e r f o r m a n c e .

INTRODUCTION

The Roof T e s t A p p a r a t u s s p e c i f i e d i n ULC S107-M1980, o r i g i n a l l y i n s t a l l e d a t t h e N a t i o n a l R e s e a r c h C o u n c i l ' s M o n t r e a l Road l a b o r a t o r y , was

moved t o t h e N a t i o n a l F i r e L a b o r a t o r y n e a r Almonte, Ont. It was r e a s s e m b l e d a n d p u t i n t o s e r v i c e w i t h m i n o r m o d i f i c a t i o n s t o a d a p t t h e e q u i p m e n t t o i t s new s e t t i n g . After i n s t a l l a t i o n , a number o f d i f f i c u l t i e s w e r e e n c o u n t e r e d . Some of t h e s e were o n l y o p e r a t i o n a l i n c o n v e n i e n c e s . The o t h e r s were

more

s e r i o u s : i t was f o u n d i m p o s s i b l e , f o r e x a m p l e , t o o b t a i n s l m u l t a n e o u s l y t h e f l a m e s h a p e a n d t h e t e m p e r a t u r e s p e c i f i e d i n t h e s t a n d a r d .

The b u r n p a t t e r n a t t h e two s t a n d a r d t e m p e r a t u r e s was small, p o i n t e d , a n d s h i f t e d t o t h e r i g h t s i d e of t h e d e c k ( v i e w e d f r o m downwind). R e . g r a p h s o f t h e v e l o c i t y p r o f i l e s ( l o c a t e d h a l f w a y u p a n d 9 4 mm o f f t h e d e c k ) show a n o n u n i f o r m v e l o c i t y a c r o s s t h e d e c k ( s e e F i g u r e 1). V e l o c i t y p r o f i l e s a t t h e a i r d u c t o u t l e t were f o u n d t o b e n o n u n i f o r m . A s a i r s p e e d i n c r e a s e d , t h e f l a m e d e v e l o p e d a t i g h t s w i r l a n d moved t o t h e r i g h t . T h i s s w i r l i n t h e a i r f l o w was o b s e r v e d w i t h t h e n a k e d e y e ( a n d r e c o r d e d o n v i d e o t a p e ) , u s i n g s t r i n g s t i e d t o a g r i d

a t

t h e a i r d u c t o u t l e t . '!he a r e a of t u r b u l e n c e w a s f o u n d t o b e c o i n c i d e n t w i t h t h e f l a m e anomaly. A p r o g r a m was u n d e r t a k e n t o i m p r o v e t h e p e r f o r m a n c e o f t h e a p p a r a t u s a n d u p g r a d e some o f i t s a c c e s s o r y components.

ADAPTING THE APPARATUS TO I T S

NEW

LOCATION

The Roof T e s t A p p a r a t u s was o r i g i n a l l y b u i l t t o u s e a n e x i s t i n g w a l l as

a u n i o n t o c o n n e c t t h e f a n b l o w e r t o t h e a i r d u c t a n d a t t h e same t i m e

i s o l a t e t h e f a n i n l e t a i r f r o m t h e d u c t e x h a u s t a i r . When t h e a p p a r a t u s was moved t o t h e N a t i o n a l F i r e L a b o r a t o r y a n a d a p t e r u n i o n h a d t o b e b u i l t t o r e p l a c e t h e wall. W i t h t h e new u n i o n i n p l a c e t h e a p p a r a t u s was moved t o

i t s p r e s e n t l o c a t i o n i n t h e b u r n h a l l a g a i n s t a s l i d i n g d o o r t o

a

s t o r a g e room. The doorway w a s f r a m e d a n d s e a l e d t o s e p a r a t e t h e i n l e t a i r i n t h e s t o r a g e room f r o m t h e e x h a u s t a i r i n t h e b u r n h a l l . With t h i s a r r a n g e m e n t warm a i r c o u l d b e d r a w n f r o m a n a d j a c e n t t o w e r a n d t h e l o a d i n g d o c k area,

t h r o u g h t h e s t o r a g e room a n d i n t o t h e a p p a r a t u s .

The t y p e of g a s was a l s o c h a n g e d . S i n c e n a t u r a l g a s was n o t a v a i l a b l e i n t h e r u r a l l o c a t i o n , b o t t l e d methane ( c o m m e r c i a l g r a d e , 9 3 % ) w a s s u b s t i t u t e d u n t i l t h e b u r n e r c o u l d be m o d i f i e d t o r u n o n t h e b u i l d i n g ' s p r o p a n e s u p p l y . S p a r k i g n i t i o n w a s a d d e d t o l i g h t t h e b u r n e r , w h i c h was p r e v i o u s l y i g n i t e d by a p r o p a n e t o r c h . A s t a n d was b u i l t f o r t h e b u r n e r u s e d i n t h e b u r n i n g b r a n d t e s t a n d p o s i t i o n e r s w e r e a d d e d t o d e f i n e t h e 1525- s p a c i n g u s e d i n t h a t t e s t . Worn s e c t i o n s of a s b e s t o s b o a r d w e r e r e p l a c e d . F o r c o n t r o l o f t h e a i r v e l o c i t y , a r e m o t e l y o p e r a t e d p n e u m a t i c c y l i n d e r w a s i n s t a l l e d t o e n a b l e a d j u s t m e n t o f t h e a i r i n l e t damper t o t h e f a n . To e n s u r e a s u f f i c i e n t

a i r

f l o w , t h e r e s t r i c t o r r i n g o r i g i n a l l y p r e s e n t a t t h e f a n i n l e t was removed.

R o b l e n

1. The f l a m e p a t t e r n was p o i n t e d and s h i f t e d toward t h e r i g h t - h a n d s i d e of t h e deck (viewed from downwind) ( s e e F i g u r e 2). T h i s s h i f t was s e v e r e enough t o a f f e c t t h e ' t e m p e r a t u r e of t h e f l a m e , a s r e a d by t h e c a l i b r a t i o n t h e r m o c o u p l e , by as much a s 300°C. S t u d i e s were t h e r e f o r e made of t h e v e l o c i t y p r o f i l e s o n t h e t e s t d e c k a n d a t t h e t u n n e l mouth. 2. 'Ihe v e l o c i t y p r o f i l e a c r o s s t h e d e c k was n o t a u n i f o r m

5

m / s 2 0.2 m / s

as

r e q u i r e d i n t h e s t a n d a r d , b u t ranged from

5.5

m / s on t h e l e f t m e a s u r i n g p o i n t t o 4.2 m / s on t h e r i g h t p o s i t i o n w i t h l a r g e v a r i a t i o n s between them. A i r d e f l e c t o r s and s t a b i l i z e r s were added b u t t h e y c a u s e d t h e v a r i a t i o n s t o s h i f t o n l y . Another p r o b l e m w i t h t h e a i r f l o w w a s i n a c h i e v i n g t h e 8 m / s wind s p e e d s p e c i f i e d i n t h e s t a n d a r d . Upon removal of t h e e x i s t i n g 20% open b a f f l e t h e wind s p e e d s h o u l d i n c r e a s e t o 8

m l s

a t t h e t h r e e m e a s u r i n g p o i n t s . The a c t u a l s p e e d measured w a s 7

m l s

on t h e l e f t , 6

m l s

i n t h e m i d d l e , and 9 . 5 m / s o n t h e r i g h t s i d e .

3. To i n c r e a s e o r d e c r e a s e t h e o v e r a l l a i r s p e e d i t

was

n e c e s s a r y t o m a n u a l l y a d j u s t t h e f a n i n l e t damper a t one end a n d o b s e r v e t h e change

a t t h e o t h e r . T h i s , combined w i t h a d e l a y e d r e a c t i o n , made t u n i n g t h e s y s t e m a t e d i o u s two-man job. O b j e c t i v e s To s o l v e t h e p r o b l e m s , t h e t h r e e main o b j e c t i v e s were:

-

t o a c h i e v e a b r o a d , c e n t e r e d , a n d u n i f o r m f l a m e p a t t e r n ;

-

t o a c h i e v e a u n i f o r m a i r f l o w o v e r t h e d e c k ;

-

t o d e v e l o p a method of v a r y i n g t h e

a i r

f l o w t o g e t p r e c i s e l y

5

o r 8

_{m l s}

v e l o c i t i e s . H o d i f i c a t i o n e A f f e c t i n g t h e S y s t e m ' s A i r Plow and F l a m P a t t e r n Component p o s i t i o n i n g . E x a m i n a t i o n of c r i t i c a l d i m e n s i o n s showed t h a t t h e g a p between t h e l o w e r e d g e of t h e c o r n i c e a n d t h e t u n n e l f l o o r w a s

e x c e s s i v e a t t h e l e f t s i d e (viewed from downwind). The b u r n e r w a s

p o s i t i o n e d a p p r o x i m a t e l y 1 2 mm t o o h i g h and 50 mm downwind of t h e s t a n d a r d p o s i t i o n . These c o n d i t i o n s were c o r r e c t e d .

A i r d u c t m o d i f i c a t i o n s . A v a r i e t y of a i r s t r a i g h t e n e r s and d e f l e c t o r s

were p r e s e n t i n t h e a i r d u c t ( s e e F i g u r e 3). These d e v i c e s

were

f o u n d t o b e

i n e f f e c t i v e . A l l d e f l e c t o r s and s t r a i g h t e n e r s t h e r e f o r e were removed from t h e d u c t a n d r e p l a c e d w i t h two 35% open b a f f l e s : one

a t

t h e l o c a t i o n of t h e o r i g i n a l 20% open b a f f l e and t h e o t h e r 0.5 m upwind from t h e o u t l e t of t h e

a i r d u c t . The p u r p o s e w a s t o f o r m a plenum which would r e l e a s e a u n i f o r m

a i r f l o w t h r o u g h t h e s e c o n d b a f f l e w i t h less s w i r l . A 10-cm-thick aluminum

honeycomb was a d d e d downwind of e a c h b a f f l e t o s t r a i g h t e n t h e

a i r

f l o w f u r t h e r .

The m o d i f i e d s y s t e m p r o d u c e d a b l u e f l a m e 1.5

m

a c r o s s . The t u r b u l e n t

swirl was removed and t h e f l a m e w a s now c e n t e r e d on t h e d e c k w i t h t h e l o w e r

e d g e s m c h w i d e r t h a n t h e d e c k . The v e l o c i t y p r o f i l e s o n t h e d e c k showed a

s l i g h t l y h i g h e r wind s p e e d i n t h e c e n t e r t h a n a t t h e e d g e s (4.9 m / s a t t h e e d g e s and 5.2 m / s i n t h e c e n t e r ) . To remove t h e b l u e n e s s of t h e f l a m e a 35%

open b a f f l e 10 cm hLgh was i n s t a l l e ' d on t h e f l o o r of t h e t u n n e l mouth t o c o n t r o l t h e a i r f l o w a r o u n d t h e b u r n e r .

The v e l o c i t y p r o f i l e s on t h e d e c k now showed a n e v e n 5 m / s which c o u l d

be a d j u s t e d t o 8 m / s ( F i g u r e 4 ) s i m p l y by o p e n i n g t h e a i r i n l e t damper t o a

p r e s e t p o s i t i o n .

B u r n e r

&dificationa

The f l a m e s t i l l was more c o n c e n t r a t e d a t t h e e d g e s t h a n i n t h e middle.

The b u r n e r ' s i n n e r p i p e was found t o have l a r g e r h o l e s a t t h e e d g e s t h a n i n

t h e m i d d l e as shown i n F i g u r e 5. To p r o d u c e a b u r n e r w i t h u n i f o r m g a s

d i s t r i b u t i o n , 35 h o l e s were f i r s t d r i l l e d

2.5

mm a p a r t and t h e n t h r e a d e d f o r

i

20 b o l t s . Chambers were formed by p o s i t i o n i n g s t e e l w a s h e r s between t h e

i n n e r and o u t e r p i p e s a l o n g t h e l e n g t h o f t h e b u r n e r . The g a s f l o w i n t o a

chamber c o u l d be c o n t r o l l e d by p l u g g i n g o n e o r more of t h e h o l e s i n t h e

chamber w i t h b o l t s . By v a r y i n g t h e chamber s i z e s and t h e number of h o l e s

p e r chamber, a u n i f o r m f l a m e f r o n t w a s p r o d u c e d which c l o s e l y a p p r o x i m a t e d

t h e f l a m e s p e c i f i e d i n t h e s t a n d a r d . Class A and C l a s s C f l a m e s c o u l d now

b e p r o d u c e d by c o n t r o l l i n g t h e f l o w of g a s t o t h e b u r n e r w i t h one v a l v e .

T h i s b u r n e r a s s e m b l y as shown i n F i g u r e 6 a l l o w e d c h a n g i n g from methane t o

p r o p a n e g a s w i t h few m o d i f i c a t i o n s .

EFFECTS OF CHANCES TO

THE

APPARATUS

The a p p a r a t u s i n i t s p r e s e n t c o n f i g u r a t i o n i s shown i n F i g u r e 7. Most

of t h e c h a n g e s were made i n t h e a i r d u c t s i n c e t h e f l a m e s h a p e i s

d r a m a t i c a l l y m o d i f i e d by c h a n g e s i n a i r flow. S e v e r a l t e s t d e c k s were

c o n s t r u c t e d from plywood and p i n e s i d i n g t o o b s e r v e t h e f l a m e s h a p e and b u r n

p a t t e r n on a n a c t u a l deck. A t y p i c a l b u r n p a t t e r n shown i n F i g u r e 8 shows a

marked improvement i n w i d t h , l e n g t h and p o s i t i o n o v e r t h e p r e v i o u s p a t t e r n

shown i n F i g u r e 2. The improvements i n t h e a i r v e l o c i t y c o n t r o l g r e a t l y

r e d u c e t h e s e t - u p t i m e and b u r n e r improvements a l l o w f a s t e r c h a n g e s from

Class C t o Class A t e s t s .

POSSIBLE F U m HODIFICATIONS

The f o l l o w i n g a r e p o s s i b l e m o d i f i c a t i o n s t o improve o p e r a t i o n s t i l l

f u r t h e r :

-

move t h e g a s s o l e n o i d c l o s e r t o t h e b u r n e r t o r e d u c e i g n i t i o n d e l a y ;

-

add a

timer

t o c o n t r o l b u r n e r "on" and " o f f " t i m e s a u t o m a t i c a l l y ;

-

r u n t h e g a s f e e d p i p e s t o t h e b u r n e r u n d e r t h e p l a t f o r m t o r e d u c e a i r t u r b u l e n c e on t h e test d e c k ;

-

u s e a p i t o t t u b e f o r a i r v e l o c i t y measurements on t h e deck;

-

u s e a row of t h e r m o c o u p l e s i n s t e a d of o n e t o d e t e r m i n e a n a v e r a g e t e m p e r a t u r e of t h e f l a m e f r o n t r a t h e r t h a n t h e s i n g l e p o i n t s p e c i f i e d i n t h e s t a n d a r d .

Modifications were made under the direction of

Dr.

A.M. Phillips. Special thanks are extended to staff of the National Fire Laboratory for their assistance.

P O I N T N O . I I F I G U R E 1 I I V E L O C I T Y P R O F I L E O V E R D E C K W I T H O U T M O D I F I C A T I O N S I

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I I ( T A R G E T V A L U E l I I

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I I I I I I I I I 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 D E C K M

~

F I G U R E 2 F L A M E S H A P E B E F O R E M O D I F I C A T I O N S

STRA l GHT ENER A N D DEFLECTOR

5 c m 'x 1 0 crn x 9 0 0 c r n P I N E BOARD

2 0 % OPEN

BAFFLE EGG CRATE 12 rnrn ANGLE IRON

A I R STRA IGHTENERS F I G U R E 3 R O O F T E S T A P P A R A T U S W I T H O U T M O D l F l C A T I O N S 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 P O I N T N O . I I I I I I I I I I I

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F I G U R E 4 V E L O C I T Y P R O F I L E O V E R D E C K W I T H M O D I F I C A T I O N S

3 . 1 8 rnrn 4 . 7 6 m m 6 . 7 5 m m C R O S S S E C T I O N O U T E R P l P E I N N E R P l P E F I G U R E 5 1 l N M O D l F l E D B U R N E R C R O S S S E C T I O N

+

P L U G G E D O P E N 1 1 4 " O P E N 318" O U T E R P I P E / S L O T \ I N N E R P I P E W A L L F I G U R E 6 M O D I F I E D B U R N E R

BURNER BAFFLES

35% OPEN

FIRST BAFFLE

lw

A L U M I N U M

HONEY COMB 1.9 rnrn CEI

A I R STRAIGHTENER ALUMINUM HONEYCOMI F I G U R E 7 M O D I F I E D R O O F T E S T A P P A R A T U S D E C K _{. .- -&}

I

F I G U R E 8 T Y P I C A L B U R N P A T T E R N F O L L O W I N G M O D I F I C A T I O N S