Temperature variations in the DBR floor furnace

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NATIONAL RESEARCH COUNCIL CANADA D I V I S I O N O F B U I L D I N G RESEARCH T E ~ [ P E R A T ~ R E V A R I A T I O N S I N T H E DBR FLOOR E+ITRNACE by T. _{2 .} H a m a t h y ANALYZED I n t e r n a l R e p o r t No. 216 of t h e D i v i s i o n of B u i l d i n g R e s e a r c h OTTAWA D e c e m b e r 1960

PREFACE

A decision was made a t t h e time t h e f i r e t e s t f a c i l i t i e s of t h e Division were being designed t h a t a column furnace would n o t be provided. Recently t h e r e has been i n t e r e s t i n t h e p o s s i b i l i t y of carrying out f i r e t e s t s on columns, which i n t u r n r a i s e d a

question of t h e s u i t a b i l i t y of t h e e x i s t i n g f l o o r furnace f o r t h i s purpose. An examination of t h e temperature v a r i a t i o n s within t h e f l o o r furnace have been made and a r e now reported, !The author, a

mechanical engineer and a research o f f i c e r with t h e F i r e Research Section i s responsible f o r f i r e r e s i s - tance s t u d i e s c a r r i e d out

i n

t h e furnace f a c i l i t i e s of t h e Division.

Ottawa

December 1960

N. B, Hutcheon A s s i s t a n t D i r e c t o r

TEMPERATURE VARIATIONS I N THE DBR FLOOR FURNACE

T. Z. Harmathy

When t h e f i r e t e s t f a c i l i t i e s of t h e National

Research Council were designed c o n s i d e r a t i o n was given t o t h e p o s s i b i l i t y of using t h e f l o o r furnace f o r performing column t e s t s . By s e l e c t i n g t h e h e i g h t of t h e furnace s o a s t o allow t h e i n c l u s i o n of column specimens of t h e r e q u i r e d l e n g t h (1) provision was made t o f u l f i l l a t l e a s t t h e space requirement f o r such t e s t s . U n t i l r e c e n t l y , however, t h e f e a s i b i l i t y of column t e s t s was i n doubt, s i n c e a v a i l a b l e information on one furnace elsewhere i n d i c a t e d t h a t t h e temperature might vary along t h e h e i g h t of t h e furnace s i g n i f i c a n t l y enough t o i n v a l i d a t e any column t e s t r e s u l t .

With t h e i n s t a l l a t i o n of new r e f r a c t o r y covers it has been p o s s i b l e t o examine t h e temperature d i s t r i b u t i o n i n t h e DBR f l o o r furnace. On 20 A p r i l 1960, a preliminary t e s t was c a r r i e d out ( T e s t No. 1). Five thermocouples were

i n s t a l l e d i n t h e furnace i n such a way t h a t t h e d i s t a n c e of t h e i r h o t junction f r o m t h e furnace f l o o r could be v a r i e d . The average furnace temperature (measured i n conformance t o ASTM E119-58) was then s e t a t a n approximately c o n s t a n t value and temperature readings were taken a t various p o i n t s w i t h i n t h e furnace. A t lower average furnace temperatures (around 600°F) very s i g n i f i c a n t temperature d i f f e r e n c e s were found. The d e v i a t i o n from t h e standard average was sometimes a s high a s -70 o r + 10 per c e n t , and decreased very slowly w i t h time elapse. When t h e furnace temperature was s e t a t h i g h e r v a l u e s , t h e d e v i a t i o n became s m a l l e r n o t only in percentage b u t a l s o i n a b s o l u t e v a l u e , due t o t h e improved h e a t t r a n s f e r c h a r a c t e r i s t i c s . Since with f i r e t e s t s , only temperatures above 1000°P a r e of p r a c t i c a l importance, t h e r e s u l t of t h i s preliminary t e s t seemed very promising.

On 22 April another t e s t was performed ( T e s t No. 2 ) . f i f t e e n thermocouples were i n s t a l l e d a t f i v e d i f f e r e n t

l o c a t i o n s and t h r e e d i f f e r e n t h e i g h t s , a s shown i n Fig. 1. (The loose f i r e - b r i c k p i l l a r s used f o r p r o t e c t i n g t h e standard furnace thermocouples a r e a l s o shown i n Fig. 1.) The standard average temperature was v a r i e d roughly according t o t h e s t a n - dard temperature-time c o r r e l a t i o n . The v a r i a t i o n of tempera- t u r e a t l o c a t i o n ,"b" during t h e f i r s t 70 minutes of t h e t e s t i s shown in Fig. 3 . The thermocouples a t 3 f t 3 i n . i n h e i g h t were n e a r t h e l e v e l of t h e burners and t h e r e f o r e recorded

moderately h i g h e r values. The s t e a d y improvement of t h e temperature d i s t r i b u t i o n w i t h t h e temperature r i s e and time e l a p s e i s n o t i c e a b l e . The s i g n i f i c a n t d i f f e r e n c e between t h e

standard average furnace temperature and t h e o t h e r t h r e e temperatukes d u r i n g t h e f i r s t

5

minutes i s due t o t h e f a c t t h a t none of t h e thermocouples used f o r t h e temperature d i s t r i b u t i o n measurements were enclosed i n s t e e l p r o t e c t i n g tubes.

S i m i l a r curves have been obtained f o r t h e thermo- couples a t l o c a t i o n s "c" and "dr' F i g . 1 I n accordance w i t h t h e e x p e c t a t i o n t h e temperature r i s e n e a r t h e l e v e l of t h e burners was more pronounced a t l o c a t i o n "c" and l e s s d e f i n i t e a t l o c a t i o n "d". A t l o c a t i o n "en where t h e thermo- couples were shaded from t h e flames by a p i l l a r , a s t e a d y though n o t t o o s i g n i f i c a n t temperature r i s e f r o m t h e bottom t o t h e t o p of t h e furnace chamber was observed. A t l o c a t i o n

"a", q u i t e unexpectedly, t h e temperature s l i g h t l y decreased toward t h e t o p of t h e chamber, probably due t o some a i r lealkage a t t h e edge of t h e r e f r a c t o r y cover.

'Phe r e s u l t s of Test No. 2 i n d i c a t e d t h a t t h e temperature d i s t r i b u t i o n was, i n g e n e r a l , s a t i s f a c t o r y enough t o a l l o i ~ t h e performance of column t e s t s . I t seemed t h a t t h e b e s t l o c a t i o n of t h e column t o be t e s t e d would be a t equal d i s t a n c e s from t h e two rows of b u r n e r s , t h a t i s

somewhere along t h e l o n g i t u d i n a l a x i s of t h e f u r n a c e , n o t t o o c l o s e t o t h e e a s t o r west w a l l .

I n o r d e r t o confirm t h e previous c o n c l u s i o n s , on 26 A p r i l a f u r t h e r t e s t was conducted ( T e s t No. 3 ) . The b r i c k p i l l a r n e x t t o t h e e a s t w a l l was regarded a s a column specimen and was surrounded w i t h 8 thermocouples, symmetri- c a l l y disposed a t two l e v e l s , and placed 12 i n . away from t h e s u r f a c e of t h e p i l l a r , a s r e q u i r e d by AS931 E119-58

( F i g 2 ) . The lower l e v e l was d e l i b e r a t e l y chosen so a s t o coincide w i t h t h e l e v e l of b u r n e r s , i n o r d e r t o o b t a i n

a d d i t i o n a l information on t h e presumably maximum d e v i a t i o n from t h e average f u r n a c e temperature n e a r t h e east-west a x i s of t h e furnace. Again t h e measurements taken from l o c a t i o n

"bfr (which d i f f e r s b u t s l i g h t l y from l o c a t i o n "b" of T e s t No. 2 ) were s e l e c t e d t o be shown, and t h i s has been done i n Pig. 4.

"Smoothedrt curves showing t h e v a r i a t i o n of tempera

-

t u r e a t l o c a t i o n "b" while t h e standard average temperature i s r a i s e d according t o t h e temperature-time c o r r e l a t i o n of

ASTM E119-58, a r e shown i n Pig. 5. I t can be seen t h a t , except a narrow range around t h e h e i g h t of t h e b u r n e r s , t h e temperature d i s t r i b u t i o n n e a r t h e east-west a x i s of t h e f u r n a c e i s f a i r l y uniform. T\Teasurements taken from o t h e r

l o c a t i o n s a l s o i n d i c a t e t h a t t h e u n i f o r m i t y of t h e temperature w i t h i n t h e whole f u r n a c e chamber i s , i n g e n e r a l , s a t i s f a c t o r y and much b e t t e r t h a n t h a t r e p o r t e d f o r a n o t h e r f u r n a c e e l s e - mhere of more e l a b o r a t e c o n s t r u c t i o n .

The temperature r i s e a t t h e l e v e l of t h e burners seems t o be somewhat higher than t h a t which can be t o l e r a t e d during a c o l u m t e s t , The measurements a t l o c a t i o n "c" of Test No, 2 shorn, however, t h a t t h e "temperature bumpf1 can be eliminated by s h i e l d i n g t h e column from d i r e c t flame exposure, This can be achieved by b u i l d i n g two loose f i r e - b r i c k p i l l a r s , approximately 1 3 i n . s q and 3 f t 6 i n , i n h e i g h t , located a s shown i n Pig. 6 ,

Figure 6 shows how t h e column specimen and t h e

standard furnace thermocouples may be arranged i n t h e furnace when t h e t e s t i s t o be c a r r i e d out i n conformance t o t h e

"Alternate t e s t of p r o t e c t i o n f o r s t r u c t u r a l s t e e l columns" of ASTM E119-58, Only a few a d d i t i o n a l p a r t s a r e needed i f a request f o r such t e s t should a r r i v e and t h e s e can be

obtained in 3 t o 4 weeks.

Although a l l major requirements f o r performing f i r e t e s t s on loaded columns a r e a l s o f u l f i l l e d , such t e s t s cannot be undertaken i n t h e n e a r f u t u r e because of t h e l a c k of appropriate loading f a c i l i t i e s .

Reference

1, Standard methods of f i r e t e s t s of b u i l d i n g c o n s t r u c t i o n and m a t e r i a l s , American Society f o r Testing Materials Designation E119-58, Philadelphia, l l p , , 1958,

FIGURE

I

FIGURE

2

FIGURE 3

VERTICAL TEMPERATURE DISTRIBUTION ( T E S T NO. 2 )

dQ. 22254-3

TIME (MINUTES)

FIGURE

4

VERTICAL TEMPERATURE DISTRIBUTION (TEST NO.

3 )

FIGURE 5

VERTICAL TEMPERATURE DISTRIBUTION (LOCATION

"b")

@

STEEL COLUMN

@

COLUMN PROTECTION

@

RESTRAINING STEEL PLATES

@

INSULATING END PIECES

@

SHIELDING PILLARS

@

END SUPPORT

@

INCONEL HOLDING DEVICE FOR FURNACE THERMOCOUPLES

@

THERMOCOUPLE WIRES

FIGURE 6

FIRE TEST OF PROTECTED STEEL COLUMNS