Fire hazard tests on small masonry chimneys

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NATIONAL R E S M 2 C H C I O W C I L CANADA

D I V I S I O N O F B U I L D I N G R E S - U G H

F I R E HAZARD

TESTS

ON SIULL MASONRY CHIMNEYS by G. T. T a r n u r a and A . G. Wilson Internal R e p o r t N o . 202 o f the 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 O t t a w a D e c e m b e r 1960

TABLE

OP CONTENTS

Page Ro

.

...

CONSIDERATIONS I N SELECTING !ITST CONDITIONS

3

....

D e s c r i p t i o n of Equipment a n d T e s t Chimneys 4 C o n d i t i o n s of T e s t and Procedure

...

6

llEST RESULTS 7

...

'Pernpe~~ature Measurements

7

...

O b s e r v a t i o n s of S t r u c t u r a l P r o p e r t i e s 1 2

...

SUMMARY AND DISCUSSION

1 4

The, Division has been aware, f c r many y e a r s ,

of many of t h e d i f f i c u l t i e s presented by domestic

chimneys. Not only must a chimney operate s a t i s f a c t o r i l y a s a gas venting device, f o r which purpose

it

must produce < r a f t , bnt it must a l s o pr0vid.e p r o t e c t i o n a g a i n s t t h e i g n i t i o n of m a t e r i a l s a d j a c e n t t o ' i t . The problems a r e tgreatly increased because t h e conventional chimney i s constructed. a s a g a r t of t h e house, and y e t must serve any, f uel-burning appliance t h a t may subsequently be connected t o

it.

A small l a b o r a t o r y has been d-eveloped f o r %he study of t h e thermal and f i r e hazard a s p e c t s of chimneys.

A f i r s t r e p o r t on t h e work c a r r i e d out over t h e p a s t

s e v e r a l years i s now presented. I t d e a l s with the d i f f i -

c u l t matter o f t h e t e s t methods and c r i t e r i a t o be a p p l i e d t o chimneys t o determine t h e i r f i r e s a f e t y , and p r e s e n t s the r e s u l t s of experiments which have been c a r r i e d out t o d a t e . This work i s continuing. The a u t h o r s a r e mechanical engineers; M r , Tamura i s a r e s e a r c h o f f i c e r with t h e Building Services Section and M r . Wilson i s

Head of t h a t Section of t h e Division o f Building Research.

Ottawa

FIm HAZARa TZSTS ON SMALL DTUSONRY CHIMNEYS

by

G. T. Tamura a n d A.G. Wilson

The f u n c t i o n o f a chimney i s t o p r o v i d e f o r t h e s a f e d i s c h a r g e t o o u t d o o r s o f f l u e g a s c s from h e a t - p r o d u c i n g

a p p l i a n c e s . To do t h i s t h e chimney mus% n o t o n l y p r o v i d e a d e q u a t e d r a f t a t a l l t i m e s , b u t i t must a l s o p r e v e n t o v e r h e a t i n g o f a d j a c e n t c o n s t r u c t i o n a n d must remain gas t i g h t a n d s t r u c t u r a l l y sound u n d e r t h e extreme c o n d i t i o n s t o which

it

may be exposed. T h i s has long: been r e c o m A l z e d by b u i l d i n g o f f i c i a l s a n d Code a u t h o r i t i e s , a n d s t a n d a r d s f o r c o n s t r u c t i o n o f masonry chimneys a n d c l e a r a n c e r e q u i r e m e n t s i n t e n d e d t o e n s u r e s a f e t y h a v e g r a d u a l l y e v o l v e d . S t a n d a r d i z a t i o n of masonry chimney c o n s t r u c t i o n h a s b e e n encouraged i n Canada by p u b l i c a t i o n o f t h e N a t i o x a l B u i l d i n g Code ( N B C ) . Both t h e 1 9 4 1 a n d

1953

i s s u e s o f t h i s a d v i s o r y document, f o l l o v l i n g t h e a p p r o a c h of t h e N a t i o n a l Board o f F i r e U n d e r w r i t e r s (NBFU) o f t h e U n i t e d S t a t e s , h a v e s p e c i f i e d i n d e t a i l a method o f d e s i g n i n g a n d c o n s t r u c t i n g masonry chimneys c o n s i d e r e d s u i t a b l e f o r t h e v e n t i n g o f ' a p p l i a n c e s b u r n i n g a n y f u e l . A s do most Codes, t h e NBC e n v i s a g e s l e s s r e s t r i c t i v e r e q u i r e m e n t s f o r t h e p r o t e c t i o n of f l u e s s e r v i n g g a s a p p l i a n c e s t h a t produce f l u e g a s t e m p e r a t u r e s n o t e x c e e d i n g 550'3'. F u r t h e r s t a n d a r d i z a t i o n o f v e n t s f o r g a s a p p l i a n c e s h a s r e s u l t e d from t h e p u b l i c a t i o n i n 1958 by t h e Canadian S t a n d a r d s A s s o c i a t i o n of' t h e I n s t a l l a t i o n Code f o r

Gas B u r n i n g Equipment.

The d e s c r i p t i v e r e q u i r e m e n t s f o r t h e s t a n d a r d masonry chimney g e n e r a l l y e n v i s a g e s o l i d u n i t masonry o r c o n c r e t e

c a r r i e d t o f o o t i n g s a n d s e l f s u p p o r t i . n g , u s u a l l y w i t h a c l a y t i l e f l u e l i n i n g . I n r e c e n t y e a r s chimney m a t e r i a l s a n d

methods o f c o n s t r u c t i o n h a v e been d e v e l o p e d which c a n n o t a l w a y s b e e v a l u a t e d i n t e r m s o f t h e s e d e s c r i p t i v e r e q u i r e m e n t s . m e r e a r e ttvo g e n e r a l g r o u p s of chimney c o n s t r u c t i o n s i n t h i s c a t e g o r y . One g r o u p c o n s i s t s o f preformed masonry chimney b l o c k s o f

d i f f e r e n t m a t e r i a l s , f o r m s , a n d t h i c k n e s s e s . Those f o r m i n g t h e second g r o u p a r e f a c t o r y - b u i l t chimneys, which i n g e n e r a l

a r e l i g h t , i n s u l a t e d s t r u c t u r e s , u s u a l l y m e t a l c o v e r e d , i n t e n d e d t o be s u p p o r t e d from t h e h o u s e f r a m i n g .

Preformed masonry chimney b l o c k s a r e u s u a l l y made o f c o n c r e t e , pumice o r expanded s l a g a g g r e g a t e a n d u s u a l l y form e i t h e r a whole, o r h a l f , segment o f a chimney. The m a t i n g h o r i z o n t a l s u r f a c e s o f t h e u n i t s may be f l a t o r may i n t e r l o c k t o improve t h e m o r t a r e d j o i n t . The c o n c r e t e s u r r o u n d i n g t h e c e n t r a l h o l e may be s o l i d o r c o n t a i n a i r s p a c e s . The a s s e s s m e n t of v a r i o u s f o r m s o f p r e c a s t masonry b l o c k s i s s i m p l i f i e d t o t h e

e x t e n t t h a t chimneys c o n s t r u c t e d o f t h e s e c l o s e l y r e s e m b l e s t a n d a r d masonry chimneys. So l o n g a s t h e w a l l s a r e

3 3/4

i n , of s o l i d c o n c r e t e , a n d s e p a r a t e c l a y chimney l i n e r s a r e u s e d , t h e i n t e n t o f t h e d e s c r i p t i v e r e q u i r e m e n t s f o r t h e s t a n d a r d masonry chimney a p p e a r t o be met. However, when t h e w a l l s

p r o v i d e l e s s t h a n

3 3/4

i n . of s o l i d c o n c r e t e , when l i g h t w e i g h t a g g r e g a t e s a r e u s e d , o r when u n i t s a r e i n t e n d e d f o r u s e w i t h o u t s e p a r a t e c l a y t i l e l i n e r s , t h e e x t e n t t o which t h e a s s e m b l i e s a r e e q u i v a l e n t t o t h e s t a n d a r d masonry chimney w i t h r e g a r d t o t h e r m a l r e s i s t a n c e

,

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

masonry chimney a n d t h i s h a s l e d t o t h e development o f performance t e s t s a n d r e q u i r e m e n t s by U n d e r w r i t e r s L a b o r a t o r i e s I n c . These a r e p u b l i s h e d a s " S t a n d a r d s f o r S a f e t y o f Cr~imneys, 7 a c t o r y

Buil-b",

UL103.

T h i s h a s become t h e b a s i s o f l i s t i n g o f f a c - t o r y - b u i l t chimneys by U n d e r w r i t e r s I a b o r a t o r i e s o f Canada. I n a d d i t i o n t o g e n e r a l d e s i g n r e q u i r e m e n t s , it o u t l i n e s t e s t s f o r t h e s t r u c t u r a l s u f f i c i e n c y o f t h e assembly a n d d u r a b i l i t y of t h e l i n e r , a n d a f i r e h a z a r d t e s t i n which a chimney i n s t a l l a t i o n i s s i m u l a t e d . I n t h e f i r e h a z a r d t e s t t h e chimney i s e n c l o s e d i n a t y p i c a l c o n s t r u c t i o n . !be i n i t i a l t e s t c o n s i s t s of t h r e e t h e r m a l shock t e s t s o f 170O0I? f l u e g a s t e m p e r a t u r e f o r 1 0 m i n u t e s w i t h e a c h t e s t s t a r l i n g w i t h t h e chimney a t room t e m p e r a t u r e o r f o u r h o u r s a f t e r t h e t e s t , w h i c h e v e r o c c u r s f i r s t . No t e m p e r a t u r e r e a d i n g on t h e e n c l o s u r e i s t a k e n . With t h e f l u e g a s i n p u t a t 1000°4" t h e chimney i s - t e s t e d u n t i l e q u i l i b r i u m c o n d i t i o n i s r e a c h e d , f o l l o w e d by a f l u e g a s i n p u t o f 1400°F f o r one h o u r . Temperat-ures of t h e e n c l o s u r e a n d c o m b u s t i b l e s i n c o n t a c t w i t h t h e chimney

m u s t

n o t exceed 160°P a t 1000°P f l u e g a s i n p u t d u r i n g t h e p e r i o d e n d i n g

4 4

h o u r s of t e s t a n d 185OF f o r a n y s u b s e q u e n t p e r i o d , a n d

m u s t

n o t exceed 210°P when f l u e g a s i n p u t i s m a i n t a i n e d a t 1400°P f o r one h o u r . The s o o t b u r n o u t t e s t c o n s i s t s o f f l u e g a s i n p u t o f 1000°F u n t i l e q u i l i b r i u m t e m p e r a t u r e s a r e a t t a i n e d f o l l o w e d by 1700°F f o r 1 0 m i n u t e s . !be maximum t e m p e r a t u r e l i m i t on t h e c o m b u s t i b l e i s 242OP d u r i n g t h i s t e s t a n d a f t e r t h e g e n e r a t o r is- s h u t o f f , Chimney a s s e m b l i e s p a s s i n g t h e t e s t s a r e r e g a r d e d a s a c c e p t a b l e f o r u s e w i t h g a s , l i q u i d o r s o l i d - f u e l - f i r e d h e a t i n g a p p l i a n c e s a n d d o m e s t i c i n c i n e r a t o r s i n which f l u e g a s t e m p e r a t u r e s g e n e r a l l y do n o t exceed 1000°F. T e s t s c o n d u c t e d on s t a n d a r d masonry chimneys (1) i n d i c a t e t h a t t h e s e f a i l t o meet t h e U.L. t h e r m a l performance r e q u i r e m e n t s f o r f a c t o r y - b u i l t chimneys. It can be assumed t h a t most chimney b l o c k c o n s t r u c t i o n s would s i m i l a r l y f a i l . T h i s h a s l e d t o q u e s t i o n s a b o u t t h e adequacy of t h e s t a n d a r d masonry chimney c o n s t r u c t i o n a n d c l e a r a n c e r e q u i r e m e n t s .

To assist, i n t h e f u r t h e r development of masonry chimney c o n s t r u c t i c n r e q u i r e m e n t s , based an performance,

t h e D i v i s i o n of B u i l d i n g Research h a s been engaged i n a program of chimney t e s t i n g . The t e s t s have been designed t o o b t a i n f u r t h e r i n f o r m a t i o n on t h e thermal performance of t h e s t a n d a r d masonry chimney and t h e t e m p e r a t u r e s of c o m b u s t i b l e s i n

t y p i c a l s u r r o u n d i n g c o n s t r u c t i o n , t o determine t h e r e l a t i v e t h e r m a l r e s i s t a n c e of v a r i o u s masonry chimney c o n s t r u c t i o n s and t h e i r s t a b i l i t y under thermal s t r e s s i n g , a n d t o o b t a i n some i n f o r m a t i o n on t h e behaviour of c l a y t i l e l i n e r s .

CONSII)ARATIONS I N SELECTING -TEST CONDITIONS

One of t h e major d i f f i c u l t i e s i n a s s e s s i n g ' t h e s a f e t y a s p e c t s of chimney c o n s t l - u c t i o n s i s t h e s e l e c t i o n of c o n d i % i o n s t h a t r e p r e s e n t r e a s o n a b l e extremes t o which t h e c o n s t r u c t i o n s a r e l i k e l y t o be s u b j e c t e d . For p u r p o s e s of developing i n f o r m a t i o n

i t

was t h o u g h t d e s i r a b l e t o o b t a i n performance r e c o r d s w i t h extended exposure t o f l u e g a s t e m p e r a t u r e s of 500, 750 and 1000°F r e p r e s e n t i n g t h e range i n extremes t o be a n t i c i p a t e d from v a r i o u s a p p l i a n c e s under s e v e r e c o n d i t i o n s . 'The v a l u e of 500°F r e l a t e s t o t h e

maximum (550°F) u s u a l l y s p e c i f i e d i n s a f e t y s t a n d a r d s f o r g a s - f i r e d c e n t r a l h e a t i n g equipment. The v a l u e of 750°P

i s t h e maximum s e l e c t e d f o r o i l - f i r e d c e n t r a l h e a t i n g equipment by t h e Canadian S t a n d a r d s A s s o c i a t i o n subcommit t e e developing s t a n d a r d s f o r t h i s equipment. A c o r r e s p o n d i n g subcommittee on o i l - f i r e d s p a c e h e a t e r s h a s s e l e c t e d 1000°F a s t h e maximum p e r m i s s i b l e f l u e g a s temperature. This a l s o a p p e a r s t o be r e p r e s e n t a t i v e of f l u e g a s t e m p e r a t u r e s w i t h i o r c e d f i r i n g of c o a l b u r n i n g a p p l i a n c e s where v a l u e s of UOO t o 1200°F a r e r e p o r t e d . Peak t e m p e r a t u r e s i n e x c e s s of t h i s o c c u r w i t h b o t h c o a l and wood f i r i n g a c c o r d i n g t o a v a i l a b l e i n f o r m a t i o n . I t w i l l be r e c o g n i z e d t h a t u n d e r normal c i r c u m s t a n c e s s u b s t a n t i a l r e d u c t i o n s i n f l u e g a s t e m p e r a t u r e from t h e o u t l e t of t h e a p p l i a n c e t o t h e i n l e t of t h e chimney occur a s a r e s u l t of h e a t l o s s from t h e f l u e o r v e n t pipe and b l e e d i n g of room a i r tlzroufih d r a f t hoods, b a r o m e t r i c d r a f t - r e g u l a t o r s

,

o r p l a t e dampers. A s a r e s u l t t h e t e m p e r a t u r e of f l u e g a s a t

e n t r y t o t h e chimney may have a v a l u e only one h a l f t h a t a t t h e a p p l i a n c e o u t l e t . I t i s d i f f i c u l t t o t a k e t h i s i n t o

a c c o u n t i n s e l e c t i n g t e s t c o n d i t i o n s , s i n c e t h e e f f e c t i s v a r i a b l e . The c o n d i t i o n s r e f e r r e d t o above, however, can be r e g a r d e d

a s abnormally s e v e r e f o r t h e r e s p e c t i v e a p p l i a n c e s .

H i g h e s t t e m p e r a t u r e s i n chimneys a r e most l i k e l y t o o c c u r a s a r e s u l t of chimney f i r e s . Chimney f i r e s a r e u n l i k e l y w i t h g a s - f i r e d equipment and w e l l a d j u s t e d o i l - f i r e d

c e n t r a l h e a t i n g u n i t s . F i r e s do o c c u r i n chimneys v e n t i n g some o i l - a n d c o a l - f i r e d u n i t s a n d a r e q u i t e common v i i t h wood-

b u r n i n g a p p l i a n c e s . I n v e s t i g a t i o n s i n Norway ( 2 ) h a v e shown t h a t f l u e t e m p e r a t u r e s d u r i n g chimney f i r e s may r a n g e from 1250 t o 2200°F o v e r p e r i o d s from 1 0 m i n u t e s t o 1 h o u r . The h i g h e s t mean t e m p e r a t u r e r e c o r d e d d u r i n g a n y one h o u r p e r i o d was 1760°P. Based on t h i s , a n d o t h e r i n f o r m a t i o n , c o n d i t i o n s of 1400°F f o r 1/2 h o u r fol-lowed by 1800°F f o r 1/2 h o u r were c h o s e n t o r e p r e s e n t chimney f i r e c o n d i t i o n s f o r t h e t e s t s r e p o r t e d h e r e i n . D e s c r i p t i o n o f Equipment a n d T e s t Chimneys

The chimney s t u d i e s were c a r r i e d o u t i n a small

l a b o l - a t o r y shown i n P i g s . 1 a n d 2. The p o r t i o n o f t h e l a b o r a t o r y i n which t h e chimneys were t e s t e d was o v e r two s t ; o r i . e s h i g h a n d w a s s e p a r a t e d i n t o W.ro s p a c e s by a f l o o r l 4 $ f t above ground f l o o r l e v e l . T h i s was i n t e n d e d t o p e r m i t t h e s i m u l a t i o n of s u r r o u n d i n g c o n s t r u c t i o n f o r i n s i d e chimneys s e r v i n g

14-

a n d 2 - s t o r y h o u s e s . F o r t h e t e s t s r e p o r t e d h e r e i n

b o t h u p p e r a n d lovier s p a c e s were m a i n t a i n e d a - t t h e same c o n d i t i c n s . A s p e c i a l propane f u r n a c e w i t h f o r c e d a i r s u p p l y w a s

u s e d t o g e n e r a t e f l u e g a s . Its f l u e g a s o u t p u t c o u l d be

c o n t r o l l e d b e t v ~ e e n 1 5 a n d 300 cfm ( a t s t a n d a r d c o n d i t i o n s ) a t

t e m p e r a - t u r e s from 150°F t o 2000°P. The propane was f i r e d t a n g e n t i a l l y i n t o a c e n t r a l chamber t h r o u g h f o u r b u r n e r s w i t h i n d i v i d u a l c o n t r o l s . The q u a n t i t i e s of' propane a n d o f p r i m a r y a n d s e c o n d a r y a i r , a n d t h e t e m p e r a t u r e s o f f u e l , a i r a n d f l u e g a s were measured. Propane q u a n t i t i e s were measured w i t h a w e t

t e s t g a s m e t e r . A i r volumes were measured w i t h c a l i b r a t e d

s h a r p edged o r i f i c e s l o c a t e d i n t h e end o f a small o r i f i c e t a n k c o n n e c t e d t o t h e s u c t i o n s i d e o f t h e f u r n a c e b l o w e r .

To o b t a i n a u n i f o r m v e l o c i t y d i s % ~ i b u t i o n o f

f l u e g a s e n t e r i n s t h e chimney, a m e t a l

ese;

c r a t e s t r a i g h t n e r

w a s p l a c e d i n t h e i n s u l a t e d m e t a l c o a n e c t i n g p i p e ups-tream of t h e thermocouple m e a s u r i n g t h e f l u e g a s i n l e t t e m p e r a t u r e .

The t e m p e r a t u r e s o f t h e chimneys a n d any. a d j a c e n t c o n s t r u c t i o n were measured w i t h chrornel-alumel t h e r m o c o u p l e s c o n n e c t e d t o r e c o r d i n g p o t e n t i o m e t e r s f o r c o n t i n u o u s r e c o r d s a n d a p o r t a b l e p o t e n t i o m e t e r f o r s p o t r e a d i n g s . Bare chromel- a l u m e l t h e r m o c o u p l e s were u s e d f o r f l u e g a s t e m p e r a t u r e

measurements a n d were checked w i t h a n a s p i r a t i n g t h e n n o c o u p l e a r r a n g e m e n t .

I n i t i a l measurements were made on a f u l l s c a l e b r i c k chimney c o n f o r m i n g t o r e q u i r e m e n t s i n t h e 1 9 5 3

N.B.9.,

t h e d e t a i l s o f which a r e shown

i n

F i g . 3 , It was c o n s t r u c t e d 3f

a s i n g l e course of d r y p r e s s e d s o l i d c l a y b r i c k ( 2 1/4 by

3

3/4

by 8 ) w i f n 8; by 8s v i t r i f i e d c l a y f l u e l i n e r f u l l y g r o u t e d .

m e chimney w a s

27

f t i n h e i g h t , measured frorn t h e f l o o r , w i t h t h e t h i m b l e

3

f t 4 i n . from t h e f l o o r . F l o o r c o n s t r u c t i o n s b u i l t t o I\Tational B u i l d i n g Code minimum r e q u i r e m e n t s were l o c a t e d 1 f t 9 i n . a n d 1 3 f t

6

i n . from t h e bottom of t h e

j o i s t s t o t h e t h i m b l e l e v e l , t o s i m u l a t e 1 s t a n d 2nd f l o o r l o c a t i o n s . F o r one s e r i e s of t e s t s an e n c l o s u r e w a s f i t t e d a r o u n d t h e chimney between f l o o r s , a s shown i n F i g .

3.

The e n c l o s u r e was c o n s t r u c t e d of 3/8-in. p l a s t e r b o a r d n a i l e d t o 2- by 4 - i n . wood s t u d s f i x e d t o t h e c o r n e r s of t h e chimney.

The r e m a i n d e r of t h e t e s t chimneys were o n l y

6

f t

l o n g . It was t h o u g h t t h a t t h e s h o r t chimneys would be a d e q u a t e f o r p u r p o s e s of c o m p a r a t i v e t e s t i n g a n d t h a t s i g n i f i c a n t

s a v i n g s i n t i m e a n d expense v ~ o u l d r e s u l t . It was p o s s i b l e t o c o n s t r u c t t h e s h o r t s p e c i n e n s on heavy me-tal p a l l e t s a n d t o move them i n t o p o s i t i o n f o r t e s t i n g on a d o l l e y . During t e s t t h e y were v e n t e d i n t o a m e t a l f a c t o r y b u i l t chimney suspended

from ' t h e r o o f above. A s shocvn i n F i g . 4 , t h e s h o r t t e s t chimneys were no-t p r o v i d e d w i t h c l e a n o u t o p e n i n g s a n d t h e h e i g h t of

t h e t h i m b l e opening w a s c o r r e s p o n d i n g l y l e s s . To d a t e , t e s t s h a v e been c o n d u c t e d on t h e follov-ling f i v e s h o r t t e s t chimneys.

1. S i n g l e c o u r s e d r y p r e s s e d c l a y b r i c k w i d i a m e t e r h o l e s i n b r i c k w i t h 8$ by 8$ v i t r i f i e d c l a y l i n e r f u l l y g r o u t e d . t h 3

f l u

2. S i n g l e c o u r s e d r y p r e s s e d c l a y b r i c k w i t h f r o g i n b r i c k a n d 85 by 8$ v i t r i f i e d c l a y f l u e l i n e r f u l l y g r o u t e d .

3.

S i n g l e c o u r s e d r y p r e s s e d c l a y b r i c k w i t h f r o g i n b r i c k a n d

84

by 84- v i t r i f i e d c l a y f l u e l i n e r s m o r t a r e d a t j o i n t s , b u t w i t h o n l y enough m o r t a r - betvieen 1j-i:ler a n d b r i c k t o l o c a t e t h e l i n e r . 4. Double c o u r s e d r y p r e s s e d c l a y b r i c k w i t h f r o g i n b r i c k w i t h no l i n e r . 5. C o n c r e t e b l o c k chimney w i t h 8-:? by 8$ v i t r i f i e d c l a y f l u e l i n e r f u l l y g r o u t e d . Wall t h i c k n e s s of c o n c r e t e b l o c k 3 3/4 i n .

A s t a n d a r d m o r t a r mix of one p a r t l i m e , one p a r t cement a n d s i x p a r t s sand was u s e d f o r a l l t e s t chimneys. S t a n d a r d i z a t i o n of c l a y l i n e r s , however, was more d i f f i c u l t .

A l l c l a y l i n e r s were o b t a i n e d from a l o c a l s u p p l i e r . Those u s e d f o r t h e f u l l s c a l e chimney were produced by m a n u f a c t u r e r

A. The r e s u l t s f o r s h o r t chimneys Nos. 1 a n d 5 , which were t h e f i r s t t e s t e d , i n d i c a t e d s i g n i f i c a n t d i f f e r e n c e s i n t h e t h e r m a l r e s i s t a n c e of t h e l i n e r s . It was s u b s e q u e n t l y

e s t a b l i s h e d t h a t t h e l i n e r s of s h o r t chimney 1 were produced by m a n u f a c t u r e r A , b u t t h o s e of s h o r t chimney 5 were produced by m a n u f a c t u r e r B.

It was c l e a r t h a t some s t a n d a r d i z a t i o n o f c l a y

l i n e r s w a s n e c e s s a r y s o t h a t d i f f e r e n c e s i n observed chimney performance were n o t mainly t h e r e s u l t of d i f f e r e n c e s i n t h e p r o p e r t i e s of t h e l i n e r s used. Some e x p l o r a t o r y thermal t e s t s on l i n e r s produced by b o t h m a n u f a c t u r e r s were c a r r i e d o u t , b u t d i f f e r e n c e s observed were n o t g r e a t . However,

l i n e r s of m a n u f a c t u r e r A were more uniform i n dimensions and a p p e a r a n c e , - a n d a number of them were hand-picked from t h e s t o c k of t h e l o c a l s u p p l i e r f o r t h e c o n s t r w c t i o n of o t h e r s h o r t chimneys.

C o n d i t i o n s of T e s t and Procedure

The f u l l - s c a l e masonry chfmney, w i t h t h e f i r s t and secand f l o o r c o n s t r u c t i o n s and w i t h o u t an e n c l o s u r e , w a s

e x p s e d t o t h e f o l l o w i n g i n l e t f l u e g a s c o n d i t i o n s . E s s e n t i a l l y steady s t a t e c o n d i t i o n s had been e s t a b l i s h e d a t t h e end of t h e t e s t p e r i o d i n d i c a t e d .

I n l e t temp., Flue g a s f l o w , Duration of t e s t

Ol? cfm h r !Be f l u e g a s f l o w r a t e s of 1 0 0 and 50 cf'm a t s t a n d a r d c o n d i t i o n s correspond a p p r o x i m a t e l y t o t h a t produced i n b u r n i n g 1 i m p e r i a l g a l l o n of o i l p e r h o u r w i t h

4

p e r c e n t and 8 p e r

cent

C02 r e s p e c t i v e l y . Illhe r a t e of 100 cfm was s e l e c t e d f o r s u b s e q u e n t t e s t s s i n c e

i t

seemed t o r e p r e s e n t a r e a s o n a b l e extreme f o r t h e s m a l l chimneys involved. With t h e e n c l o s u r e , a s shown i n t h e c r o s s - s e c t i o n of Fig.

3,

between 1 s t and 2nd f l o o r l e v e l s t h e

f u l l

s c a l e chimney was exposed t o t h e follorving i n l e t f l u e gas c o n d i t i o n s .

I n l e t temp., Flue g a s f l o w Duration o f t e s t

OF cfm h r

The p e r i o d of 1 4 h o u r s

w a s

chosen because s t e a d y s t a t e c o n d i t i o n s were approximated i n this time and a l s o t e s t s c o u l d be

completed i n one extended work p e r i o d by t h e same l a b o r a t o r y t e c h n i c i a n .

The s h o r t masonry chiwteys were exposed t o f l u e gas i n l e t c o n d i t i o n s of TOO,

750

'.r).c! ?.IILJO"P a t a f l o w r a t e of 100 cfm f o r 14 h r . Thi:; wa? f o l l c w c d b y t n o o r more thermal shock t e s t s of one-half hour 2 - t

:19QO0P

and one-ha1.f hour a t

1800°F. Chimneys 1 m d

5

mere t e s % e d both with and without surrounding f l o o r - rcnstruct-ion.

The

remainder were t e s t e d withou-t t h e f l o o r c o n s t r u c t i o n . The e f f e c t on chimney and f l o o r c o n s t r u c t i c n s u r f a c e temperatures of i n s u l a t i o n between

j o i s t s and chimney and o f metal f i r e s t o p p i n g between t h e chimney and underside of j o i s t s i?r;:,s determined a t

750°F

and 100 cfrn i n l e t :Pl?lc gas conclitions t v i t h ckiimney

5.

O'aservations of s u r f a c e temperatures o f chimney and surrounding construct-ior! and temperature g r a d i e n t s a c r o s s t h e components o f t h e chimneys were made w i t h a l l chimneys a t each e c n d i t i o n of t e s t . Temperatures under a

6-

by 6 - b y 3/16-in.

f e l t pad glued t o t h e surface of t h e s h o r t t e s t chimney No. 1 j u s t above t h e f i r s t f l o o r l e v e l were a180 measured. The pad, perhaps of d o u b t f u l v a l u e , was intended t o give a comparative s u r f a c e temperature measuremenb l e 2 s a f f e c t e d by v a r i a t i o n s i n o u t s i d e s u r f a c e ~ o n d u c t a n c e , A t eack t e s t c o n d i t i o n measure- ments were made of dimensional changes, both h o r i z o n t a l l y and v e r t i c a l l y , 02 t h e s u r f a c e of s e v e r a l of t h e s h o r t t e s t chimneys and a l l chimneys were inspec-ted f o r c r a c k s i n masonry and l i n e r s .

A s a f u r t h e r index of cracking t h e a i r leakage r a t e s of t h e s h o r t chimneys were measured following exposure t o caeh c o n d i t i o n a t p r e s s u r e s up t o 4 i n . water gauge. T h i s was done by connecting a blower and c a l i b r a t e d v a r i a b l e a r e a f l o w r a t e r t o t h e chimney thimble and s e a l i n g t h e o u t l e t o f t h e chimney w i t h a gasketed cap clamped i n p o s i t i o n .

I n t h e thermal t e s t s on t h e chimney l i n e r s t h r e e s e c t i o n s were cemented one above t h e o t h e r t o provide a t e s t specimen

6

f t

high. The specimen was smroimded by a wire cage, a s a s a f e t y precaution, and vented i n t o t h e f a c t o r y b u i l t

chimney, Continuous records of i n s i d e and o u t s i d e s u r f a c e temperatures and observations of cracking were made under a v a r i e t y of f l u e gas i n l e t c o n d i t i o n s ,

TEST HESULTS

Temperature Measurements

Temperatures of t h e chimney components and t h e

s m -

rounding combustibles were measured with chromel-alumel thermocouples. Thermocouples were placed on t h e o u t s i d e s u r f a c e of chimney and held i n place with s a u r e r i z e n cement. Ilhermocouples f o r t h e l i n e r s were embedded f l u s h with t h e r e s p e c t i v e s u r f a c e s and h e l d i n p l a c e w i t h s a u r e r i z e n cement

w i t h t h e exception of t h e o u t e r s u r f a c e of t h e l i n e r s o f t h e f u l l scsl-e masonry chimney and chimneys No. 1 and

5

where t h e therruclcouplcs were placed on t h e s u r f a c e and h e l d with mortar. Temperatures of t h e surrounding combustibles

t h e s u r f a c e and h e l d i n p l a c e w i t h p l a s t i c wood. Thermocouple l o c a t i o n s were i n most c a s e s d u p l i c a t e d on t h e f o u r s i d e s of t h e chimney, b u t o n l y t h e maximum t e m p e r a t u r e s a r e r e c o r d e d i n t h i s r e p o r t . Temperatures d i f f e r e d somewhat on t h e v a r i o u s s i d e s due t o t h e v a r i a t i o n s i n c o n v e c t i o n a i r c u r r e n t s i n t h e l a b o r a t o r y a n d , a l s o , due t o t h e n o n - u n i f o r m i t y o f t h e f l u e g a s t e m p e r a t u r e d i s t r i b u t i o n w i t h i n t h e f l u e . A m e t a l s h i e l d w i t h a n a s b e s t o s b a c k i n g was p l a c e d on t o p of t h e c o n n e c t i n g

p i p e t o d i v e r t i t s h e a % away from t h e chimney a n d t h e f l o o r s e c t i o n .

S i n c e t h e b a s e b o a r d mas made w i t h h i n g e s a t t h e c o r n e r s and clamped a r o u n d t h e chimney and n o t a t t a c h e d t o t h e f l o o r b o a r d s , a g a p of 1/4 i n . i n viidth o c c u r r e d between t h e b a s e b o a r d a n d t h e f l o o r b o a r d s w i t h t h e v e r t i c a l e x p a n s i o n of t h e chimney d u r i n g t h e t e s t . T h i s a i r g a p p r o b a b l y a l l o w e d more c o n v e c t i o n a i r t o f l o w u p througli t h e f l o o r s e c t i o n a n d may h a v e r e s u l t e d i n l o w e r framework t e m p e r a t u r e s t h a n w i t h -the b a s e b o a r d f i x e d t o t h e f l o o r b o a r d s .

F u l l - S c a l e Clay B r i c k Chimney.

-

With f i r s t a n d second f l o o r s e c t i o n s i n p l a c e , t e m p e r a t u r e measurements o b t a i n e d on t h e

f u l l

s c a l e masonry chimney a r e shown i n Figs.

5 , 6

a n d

7.

Iaximum t e m p e r a t u r e s were r e c o r d e d a t t h e f i r s t f l o o r l e v e l , a n d a s t h e t i m e t e m p e r a t u r e c u r v e s i n d i c a t e , e q u i l i b r i u m t e m p e r a t u r e s o f t h e chirnne y a n d t h e s u r r o u n d i n g f rameviork were r e a c h e d a f t e r 22 t o 28 h o u r s of s t e a d y o p e r a t i o n , It w i l l be n o t e d t h a t e q u i l i b r i u m t e m p e r a t u r e s a r e a p p r o a c h e d w i t h i n 1 0 t o 15OP a f t e r 1 4 h o u r s o f o p e r a t i o n .

A comparison was made between t h e chimney s u r f a c e

and

t h e framework t e m p e r a t u r e s obta.ined w i t h f l u e g a s flow of 50

a n d 1 0 0 cfm. The r e s u l t s a r e p r e s e n t e d i n F i g . 8. A s e x p e c t e d , l o w e r tempera-lures o c c u r a t t h e l o w e r f l o w r a t e f o r c o r r e s p o n d i n g i n l e t f l u e g a s t e m p e r a t u r e s . T h i s i s due t o t h e l o w e r s u r f a c e c o n d u c t a n c e a n d , a l s o , t o g r e a t e r c o o l i n g o f t h e f l u e g a s a t t h e l o w e r h e a t i n p u t . The r e s u l t s o f t h e t e s t s w i t h t h e p l a s t e r b o a r d e n c l o s u r e betvceen f i r s t a n d second f l o o r l e v e l s a r e g i v e n i n F i g .

9.

H i g h e r framework t e m p e r a t u r e s were o b t a i n e d a t t h e s e c o n d f l o o r l e v e l . T h i s i s due t o t h e v e r t i c a l t e m p e r a t u r e g r a d i e n t i n t h e a i r i n s i d e t h e e n c l o s u r e a s a r e s u l t of

c o n v e c t i o n . The ma:cimum c o m b u s t i b l e t e m p e r a t u r e was o b t a i n e d a t t h e wood f i r e s t o p l o c a t e d between t h e j o i s t a n d t h e chimney s u r f a c e . The maximum t e m p e r a t u r e o f t h e s t u d s a t t a c h e d t o t h e

c o r n e r s of t h e chimney was f o u n d t o b e l o w e r t h a n t h e f l o o r o r j o i s t t e m p e r a t u r e s a t t h e second f l o o r l e v e l .

Chimney s u r f a c e a n d j o i s t t e m p e r a t u r e s a t t h e s e c o n d f l o o r l e v e l w i t h t h e e n c l o s u r c clre compared w i t h t h o s e a t t h e

f i r s t

f l o o r l e v e l o f t h e chimney w i t h o u t t h e e n c l o s u r e i n F i g . 1 0 . Tempera-tures w i t h t h e e ~ ~ c l o s u r e were f o u n d t o b e s i g n i f i c a n t l y h i g h e r . T e m p e r a t u r e s o f j o i s t , f l o o r , p l a s t e r b o a r d a n d f i r e s t o p a t t h e s e c o n d f l o o r l e v e l a r e p l o t t e d v e r s u s t i m e i n F i g s . 11, 1 2 , 1 3 and 1 4 . Comparison o f t h e s e w i t h t i m e t e m p e r a t u r e c u r v e s i n F i g s .

5 , 6

and

7

f o r t h e chimney w i t h o u t a n e n c l o s u r e i n d i c a t e s t h a t t h e s l o p e s o f t h e c u r v e s a t t h e end o f 1 4 h o u r s a r p g r e a t e r f o r t h o s e o f t f i e chimney w i t h a n e n c l o s u r e , a n d t h a t t h e t i m e r e q u i r e d t o r e a c h s t e a d y s t a t e i s p r o b a b l y much l o n g e r .

Shc;rt S i n g l e Course Clay - --.--- B r i c k Chi:nnexs.

-

-

Illhe r e s u l t s o f

t h e r m a l t e s t s a - t t h e e n d o f

1 4 h o u r s on s h o r t chimney

NO. 1 a r e shown i n P i g . 1 5 a n d t h e s e a r e compared w i t h chimney

s u r f a c e a n d framework t e m p e r a t u r e s f o r t h e f u l l s c a l e chimney i n F i g . 1 6 . These t e m p e r a t u r e s tvere f o u n d t o be h i g h e r f o r t h e s h o r t chimney. S i m i l a r l y , t h e f l u e g a s t e m p e r a t u r e s a - t t h e f i r s t f l o o r l e v e l were f o u n d t o be l o w e r a t c o r r e s p o n d i n g i n l e t f l u e g a s t e m p e r a t u r e s f o r t h e f u l l s c a l e chimney. Chimney s u r f a c e a n d framework t e m p e r a t u r e s f o r t h e f u l l s c a l e a n d t h e s h o r t chimney a r e r e p l o t t e d a g a i n s t t h e f l u e g a s t e m p e r a t u r e a t t h e f i r s t f l o o r l e v e l i n F i g .

17.

Temperature r e l a t i o n s h i p s f o r b o t h chimneys a r e s i m i l a r w i t h o n l y s l i g h t l y h i g h e r t e m p e r a t u r e s f o r t h e s h o r t chimney. The h i g h e r f l u e g a s t e m p e r a t u r e d r o p from i n l e t t o f i r s t f l o o r l e v e l o b t a i n e d w i t h t h e f u l l - s c a l e chilnney i s p r o b a b l y due t o l e a k a g e a i r from t h e c l e a n o u t d o o r a n d t h e l o n g e r f l u e l e n g t h below t h e t h i m b l e l e v e l which p r o v i d e d g r e a t e r c o o l i n g a r e a . A s shown i n F i g . 1 5 t h e b a s e b o a r d t e m p e r a t u r e

i s

r e d u c e d 1 5 t o 20°F w i t h cement a s b e s t o s i n s u l a t i o n betvieen t h e b a s e b o a r d a n d t h e chimney s u r f a c e . Die t h e r m a l performance w i t h o u t f l o o r s e c t i o n o f c l a y b r i c k chimney No. 1 wi"& f u l l y g r o u t e d l i n e r a n d c l a y

b r i c k chimney No.

3

w i t h j u s t enough m o r t a r t o l o c a t e t h e l i n e r a r e compared i n F i g . 18. S u r f a c e t e m p e r a t u r e s were f o u n d t o b e a l m o s t t h e same w i t h v a l u e s f o r t l i e chimney wLth l i n e r n o t g r o u t e d a p p r o x i m a t e l y 1 0 ° F l o w e r . Temperature u n d e r t h e

6- by 6- by 3/16-in. f e l t pad l o c a t e d j u s t above t h e first

f l o o r l e v e l a p p r o x i m a t e d t h e s u r f a c e t e m p e r a t u r e o f s h o r t chimney No. 1 w i t h f l o o r s e c t i o n . The c l a y b r i c k chimney No. 2 w i t h

t h e l i n e r s f u l l y g r o u t e d was s u b j e c t e d t o one t h e r m a l t e s t

a t a 1000°P f l u e g a s i n l e t t e m p e r a t u r e . S u r f a c e t e m p e r a t u r e s

a t t h e end of 1 4 h o u r s o f t e s t were s i m i l a r t o t h o s e o f t h e c l a y chimneys No. 1 a n d No. 3 . _{Clay b r i c k s w i t h c o r e d h o l e s} were u s e d f o r t h e c o n s t r u c t i o n o f c h i n ~ n e y s No. 1 a n d c l a y b r i c k s w i t h f r o g s f o r t h e chimneys No. 2 a n d No. 3.

S h o r t Double Course Clsy Eri.cl; I_-V Qiircnex.

-

!Thermal t e s t

r e s u l t s on t h e double c o u r s e c l a y b r i c k chimney w i t h o u t a

l i n e r (No, 4 ) a r e g i v e n i n Pig.

29.

A t t h e end of 1 4 h o u r s of t e s t w i t h 1000°F i n l z t f l u e g a s t e m p e r a t u r e , t h e chimney s u r f a c e temperature i s 7OUF lovser t h a n t h a t of t h e s i n g l e c o u r s e c l a y b r i c k chimney w i t h l i n e r .

S h o r t Concrete Block Chimnsx.

-

S u r f a c e t e m p e r a t u r e s of t h e c o n c r e t e b l o c k chimney

(iK

5 )

w i t h o u t a f l o o r s e c t i o n a r e shown i n Fig. 20. Comparing this w i t h Pig. 18 s u r f a c e t e m p e r a t u r e s of c o n c r e t e b l o c k and c l a y b r i c k chimneys a r e found t o be s i m i l a r w i t h t h e former g i v i n g s l i g h t l y l o w e r v a l u e s ,

R e s u l t s of t h e r m a l t e s t s c a r r i e d o u t a t a n i n l e t f l u e g a s temperature of 750°P and a f l u e gas flow of 1 0 0

cfm

t o determine t h e e f f e c t o f i n s u l a t i n g t h e j o i s t and t h e u s e of a s h e e t m e t a l f i r e s t o p a r e a l s o shown i n Fig. 20.

With m i n e r a l wool between t h e j o i s t a n d chimney t h e j o i s t t e m p e r a t u r e w a s lower d u r i n g t h e i n i t i a l p a r t of t h e t e s t b u t a t t h e end of 1 4 h o u r s it was t h e same a s t h a t of t h e

j o i s t w i t h o u t any i n s u l a t i o n , If t h e t e s t had been o o n t i n u e d beyonc t h e 14-hr p e r i o d , t h e t e m p e r a t u r e of t h e j o i s t w i t h i n s u l a t i o n would probably have exceeded t h a t of t h e j o i s t

w i t h o u t i n s u l a t i o n . With

a

_{s h e e t m e t a l f i r e s t o p}

_{a t}

_{t h e bottom}

of t h e j o i s t , t h e j o i s t t e m p e r a t u r e a t t h e end of 1 4 h r

was 60°F

h i g h e r t h a n t h a t of t h e s t a n d a r d f l o o r s e c t i o n . !T!hese h i g h e r frame- work t e m p e r a t u r e s a r e caused by t h e r e s t r i c t i o n of t h e c o n v e c t i o n

of a i r around t h e frameworlc, Baseboard t e m p e r a t u r e s were t h e same, e i t h e r w i t h t h e j o i s t space i n s u l a t e d o r w i t h t h e m e t a l

f i r e s t o p and were 50°P h i g h e r t h a n w i t h t h e s t a n d a r d f l o o r s e c t i o n , The h i g h e r baseboard t e m p e r a t u r e s a r e a r e f l e c t i o n of lower

h e a t l o s s e s from t h e chimney i n t h e v i c i n i t y of t h e f l o o r

s e c t i o n below which l e a d s t o h i g h e r chimney s u r f a c e t e m p e r a t u r e s . S h o r t T e s t Chimney Erne -Temperature R e l a t i o n s h i p .

-

The r a t e s of s u r f a c e t e m p e r a t u r e r i s e of t h e s h o r t t e s t chimneys a r e compared i n P i i s . 21 and 22. Although a t t h e end of i 4 h r

a t

1000°P i n l e t f l u e g a s t e m p e r a t u r e t h e s u r f a c e t e m p e r a t u r e of t h e c o n c r e t e b l o c k chimney No. 5

is

a l m o s t t h e same a s t h a t of t h e s i n g l e c o u r s e c l a y b r i c k chimneys No. 1 and No.

3 ,

t h e c u r v e s i n d i c a t e t h a t t h e former h a s g r e a t e r t h e r m a l c z p a c i t y and t h a t t h e s u r f a c e t e m p e r a t u r e of t h e c o n c r e t e b l o c k chimney may be h i g h e r a t s t e a d y s t a t e c o n d i t i o n . The s u r f a c e t e m p e r a t u r e of

t h e double c o u r s e chimney No. 4 i s l o n e r by 75OP and it i s

e x p e c t e d t h a t t h e time t o t h e r m a l e q u i l i b r i u m i s much l o n g e r t h a n f o r t h e o t h e r s h o r t t e s t chimneys. The time t e m p e r a t u r e c u r v e of t h e c l a y b r i c k chimney No. 2 tended t o f l a t t e n a t

4

h r of t e s t . This w a s probably caused by t h e l a t e n t h e a t

of e v a p o r a t i o n of t h e m o i s t u r e i n t h i s chimney. Since no t h e r m a l t e s t w a s r u n p r i o r t o t h e 1000°P t e s t , t h i s chimney probably

S u r f s c e t ~ r n p e r a t i : ~ . ; ; ~ I-ec:o:rd.eii

_.

d u r i n g a n d a f - t e r t h e

.

1 - h r t h e m a 1 shock , t e a t s

are

s?l~'i;,:n l n !.;'if:, 22 f o r t h e s i n g l e a n d doubla c o u r s e c l ? y b-cici; chimneys vvvitl~aut a f l o o r s e c t i o n and t h e c o n c r e t e b l o c k chimr!:,:~ wj-th a f ' l o o r s e c t i o n . The

maximum s u r f a c e -temperature:; f o r ' t h c c o r i c r e t e b l o c k a n d s i n g l e c o u r s e c l a y b r i c k chimneys, wliick o c c ~ r r e d 1$ h r a f t e r t h e end of t e s t , wel-e a p p r o x i n c ? t c l y 20D0T". 'The maximum s u r f a c e t e m p e r a t u r e f o r t h e double c o u r s e c l e y b r i c k chimney, r e a c h e d

3 s

h r a f t e r t h e end of t h e t e s t , was l2C"P.

A f t e r four' the-mzl. shock . t e s t s , a lGGO°F t h e r m a l t e s t was r e p e a t e d w i t n t h e c o ~ i c r e . t e b l o c k chimney. Although t h e

chimney was CI-aclce t l s e v e r e l y , t h e surface t e n l p e r a t u r e

r e a d i n g s were f o u n d t o be u ~ a l t e r ' e d from t h e p r e v i o u s 1C30°F t h e m a l . t e s t , .

Temperature G r a d i e n t s IIlhrouG c'k1imne;y S e c t i o n s .

-

Temperature g r a d i e n t s 'througt-i t h e s h o r t t e s t c h i m ~ e y s a t t h e end o f 1 4 h r of t e s t a r e giv.c-11 i n W b l e I. The x ~ e s i s t a n c e s t o h e a t f l a w of t h e c o m p o n e ~ t s of t h e chirnney a r e p r o p a r t i o n a l t o t h e r a t i o of the t e m p e ~ a t u : r e d r o p s a c r o s s t h e components t o t h e o v e r - a l l t e m p e r a t u r e d r o p , u n d e r s-beady s t a t e c o n d i t i o n s . The r a t i o o f t h e t e m p e r a t u r e d r o p s a c r o s s masonry a n d l i n e r t o t h e t e m p e r a t u r e d i f f e r e n c e between f l u e g a s a n d a m b i e n t a i r a r e a l s o g i v e n i n Table I , i n d i c a t i n g t h e r , e l . a t i v e r e s i s t a n c e s o f t h e s e components. It c a n be s e e n -tinat a p p r o x i m a t e l y h a l f o f t h e o v e r - a l l t h e r m a l r e s i s t a n c e :is p r o v i d e d by t h e chimney w a l l s a n d t h e r e m a i n d e r by t h e i n s i d e and o u t s i d e f i l m r e s i s t a n c e s . The c l a y b r i c k chimney w i t h l i n e r s vcnl:roirted (chimney No.

3 )

shows a s l i g h t l y h i g h e r r e s i s t a n c e t h a n v?ith t h e l i n e r s g r o u t e d (chimney No. 2 ) , assumin,y tile resiz;tar!ce o f i n s i d e a n d o u t s i d e f i l m s e s s e n t i a l l y t h e sainr: ri.n ho-tfi t e s t - , a I t i s s e e n t h a t t h e

t h e m a l r e s i s t a n c e of t h e c o n c r e t e 5:iock chimricy KO.

5

i s h i g h e r t h a n t h a t o f t h e c l a y b r i c k c=hi,nney ?To. 1, ai:ain assuming t h a t t h e f i l m r e s i s t a n c e s were e s s e n - t i a l - l y - t h e same i n b o t h t e s t s e r i e s . The l i n e r i n t h e concre-be bl-oclc chi.r;l_ney, however, r e p r e s e n t s a g r e a t e r por-l;i.on o f 'iil-ie chimney w a l l r e s i s t a n c e .

T h i s may h a v e been due a t l e a s t i n p a r t t o th.e g r e a t e r w a l l t h i c k n e s s of t h e l i n e r s i n t h e c o r ~ c r e t e b l o c k chimney

(3/4

i n . a s compared t o 5/8 i n . ) . The t l ~ e r m a l r e s i s t a n c e o f t h e

c o n c r e t e b l o c k would a p p e a r t o b e ~ o n ~ ~ p a r a b 1 . e t o t h a t of t h e b r i c k .

The o v e r - a l l w a l l r e s i s t a n c e of chimney No. 2 ( b r i c k w i t h f r o g ) i s s l i g h t l y g r e a t e r t h a n t h e t of chimney No. 1 ( b r i c k w i t h c o r e d h o l e s ) . However a s u b s t a n t i a l d i f f e r e n c e

i n

t h e

r a t i o of -the l i n e r and masonry r e s i s t a n c e s was o b t a i n e d . !Phis may be due l a r g e l y t o t h e d i f f e r e n t method u s e d

i n

l o c a t i n g t h e t h e r m o c o u p l e s on t h e o u t s i d e s u r f a c e of t h e l i n e r . The t h e r m o c o u p l e was .gbacarl o n th.3 s u r f a c e and h e l d w i t h m o r t a r f o r

chimney No. 1 and I l u s h w i t h t h e s u r f a c e i n a groove a n d h e l d w i t h cement f o r chimney No. 2 , r e s u l t i n g

i n

a h i g h e r t e m p e r a t u r e

reading f o r t h e l a t t e r . The method of mounting t h e thermo- couple on t h e outside surface of, t h e l i a e r o f chimney No. 3 was s i m i l a r t o t h a t f o r chimney No, 2, while t h e method used f o r chimney No. 5 was s i m i l a r t o t h a t f o r chimney No, 1.

Observations of S t r u c t u r a l I?roperties

Thermal Ekpansion Measurements.

-

During t h e thermal t e s t a v e r t i c a l and h o r i z o n t a l expansion measurements were taken on t h e outside s u r f a c e opposi%e t h e i n l e t opening. A s shown i n

Table

I1

t h e u n i t v e r t i c a l expansion of t h e c l a y b r i c k chimneys, Nos. 1 and

4 ,

i s twice a s g r e a t a s t h a t o f t h e concrete block chimney Bo.

5 ,

mith t h e concrete block

and h o r i z o n t a l expansions a r e i d e n t i c a l expansion f o r t h e c l a y b r i c k chimney i s

chimney t h e v e r t i c a l whereas t h e h o r i z o n t a l l e s s t h a n t h a t of t h e concrete block chimney. !Phis may be due t o t h e l a r g e r number of h o r i z o n t a l mortar j o i n t s i n t h e b r i c k chimney, which

s e p a r a t e and allom g r e a t e r v e r t i c a l movement o f t h e masonry. No expansion measurements were taken on chimneys nos. 2 and

3.

Cracks i n Chimneys.

-

Chimneys were examined f o r cracks and r e s u l t s recorded a f t e r each thermal t e s t . The s e v e r i t y of cracking was d i f f i c u l t t o evaluate by v i s u a l observation.

Since l i n e r s were f i x e d i n s i d e t h e chimney

it

was p o s s i b l e t o examine them only a t i n l e t and e x i t . No cracking was observed during t h e 500°P thermal t e s t s on any c l a y b r i c k chimneys. H a i r l i n e cracks were noted on t h e concrete block chimney extending v e r t i c a l l y througli t h r e e blocks. During t h e 750°F t h e r n a l t e s t , a l l chimneys showed h a i r l i n e cracks i n mortar

j o i n t s and i n t h e masonry. These cracks were more numerous and wider a f t e r t h e 1000°F t e s t . Severe cracks i n t h e masonry

of a l l chimneys appeared during t h e thermal shock t e s t , with cracks ranging from h a i r l i n e t o 1/8-in. i n width. These cracks tended t o c l o s e up a s t h e chimney cooled down a f t e r t h e t e s t .

No l i n e r cracks mere observed a f t e r t h e 500°P and 750°P thermal t e s t s . H a i r l i n e cracks appeared i n t h e l i n e r s a f t e r t h e 1000°P thermal t e s t i n some of t h e chinnegs. Liners i n a l l chirmeys cracked durixg t h e thermal shock t e s t . No

fragment of l i n e r s i n any cllirnney was found t o have f a l l e n out. Besides t h e v i s u a l observation of cracks, s t r u c t u r a l degradation o f chimneys was assessed by a i r leakage measurements before and a f t e r each thermal - t e s t . To ensure t h a t t h e i n l e t f i t t i n g f o r p r e s s u r i z i n g t h e chimney and t h e o u t l e t opening were properly s e a l e d , t h e s e a l i n g j o i n t s were checked with soap

s o l u t i o n f o r extraneous leakage. The a i r leakages measured were adjusted t o standard condition,

23, 24, c o n d i t i

The r e s u l t s o f a i r leakage t e s t s a r e shown i n

25 and 26. Exposure t o t h e various thermal t e . s t Pigs. .ons resu1ted.i.n reductions i n t h e a i r leakage

r e s i s t a l ~ c e of t h e d i f f e r e n t chimneys, Af_'ter t h e 500°F and 750°P thernial t e s t -the i n c r e a s e i n a i r l e a k a g e was found t o be s m a l l . A decided i n c r e a s e i n a i r leaka{;e was n o t e d a f t e r t h e 1000°P t h e r m a l t e s t . A f t e r -i;he chimney had been s u b j e c t e d t o t h e thermal shock t e s t , t n e r a t e of a i r l e a k a g e r o s e

s i g n i f i c a n t l y and c o n t i n u e d t o i n c r e a s e w i t h s u b s e a u e n t thermal shock t e s - t s .

A comparison o f a i r l e a k a g e s f o r t h e s i n g l e c o u r s e c l a y b r i c k chimneys w i t h t h e l i n e r s g r o u t e d (chimneys No. 1 a n d 2 ) a n d t h e l i n e r s n o t g r o u t e d (chimney No.

3 )

shorvs

s i m i l a r r a t e s u p t o t h e 1000°F t h e r m a l t e s t . A f t e r t h e

thermal sl~oclt te s t s , however, t h e chimney w i t h t h e l i n e r g r o u t e d shows l e s s l e a k a g e i n d i c a t i n g t h a t t h e m o r t a r behind t h e

l i n e r a s s i s t s i n t h e p r e v e n t i o n o f a i r l e a k a g e . The a i r

l e a k a g e s of t h e c o n c r e t e b l o c k chimney No. 5 measured a f t e r t h e s t e a d y thermal t e s t s a r e a l m o s t t h e same a s t h o s e o f t h e s i n g l e c o u r s e c l a y b r i c k chimney, b o t h w i t h l i n e r s f u l l y g r o u t e d . Hmvever, h i g h e r a i r l e a k a g e was measured w i t h t h e

former a f t e r each thermal siiock t e s t . The a i r l e a k a g e s measured a f t e r t h e s t e a d y -thermal t e s t and t h e r m a l shock t s a t s , were

g r e a t e r f o r t h e double c o u r s e c l a y b r i c k chimney No. 4 w i t h o u t

a

l i n e r t h a n f o r t h e o t h e r chimneys. It can be concluded t h a t t h e l i n e r s 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 e r e s i s t a n c e t o a i r

l e a k a g e of t h e c l a y b r i c k chimneys.

F l u e L i n e r T e s t s

9310 s e t s of v i t r i f i e d c l a y f l u e l i n e r s from m a n u f a c t u r e r

A and one s e t from ~ ; a n u Y a c t u r e r B w e r e t e s t e d w i t h t h e l i n e r s f r e e s t a n d i n g . Each s e t c o n s i s t e d o f tilree 2 - f t l i n e r s placed on t o p of each o t h e r ( w i t h ends m o r t a r e d ) . I n s i d e and o u t s i d e s u r f a c e t e m p e r a t u r e s were r e c o r d e d a t each i n l e t f l u e g a s

t e m p e r a t u r e c o n d i t i o n , w i t h t h e f l u e g a s f l o w m a i n t a i n e d a t 100 cfm.

With t h e f i r s t s e t of l i n e r s from m a n u f a c t u r e r A ,

c r a c k s o c c u r r e d i n i t i a l l y i n t h e t o p l i n e r a t t h e 750°F

i n l e t t e m p e r a t u r e . !Chis was thouglit t o be due t~ t h e w e i g h t of t h e f a c t o r y b u i l t chimney on t o p of t h e l i n e r . The t o p l i n e r was r e p l a c e d and viith t h e w e i g h t of t h e f a c t o r y b u i l t chimney r e l i e v e d , a l l l i n e r s cracked a t 1000°P. A l l of t h e second s e t of l i n e r s c r a c k e d a t t h e 750°7? i n l e t t e m p e r a t u r e c o n d i t i o n .

Clay l i n e r s o b t a i n e d from m a n u f a c t u r e r B a l s o cracked a t t h e 750°P i n l e t t e m p e r a t u r e . With t h e f l u e g a s t e m p e r a t u r e i n c r e a s e d from 900°P t o 1900°P i n 100°F i n c r e m e n t s a t h a l f

h o u r i n t e r v a l s , t h e l a r g e s t c r a c k i n t h e f l u e l i n e r was

1/4

i n . wide and extended v e r t i c a l l y from t h e t o p t o t h e bottom of t h e

~ l t h o u g h the liners cracked in a number of places when subjected to inlet temperatures above

750°P,

the liners remained in one piece, with no fragments of liners falling out.

In

Table I11 surface temperatures of the liners

obtained during the liner test are compared with those obtained during tests on the short chimney. Since thermal stress in the liner is a function of the temperature difference between the inside and outside surfaces, temperature drops are also included. Because the maximum temperature drop across the liners in the thermal tests on the test chimneys occurred after two hours of exposure, temperature readings in Table

111

are recorded for this time.

The temperature drop across liner A was consistently greater than across liner 3 at the same inlet flue gas tempera- ture. This is due to the greater wall thic'mess for liner B, and the ratio of the thermal resistances of liner A.and liner B approximates the thichess ratio, The relative thermal resis- tance of the liners increased as the inlet flue gas temperature was increased, This is due to the decrease in the inside and

outside surface film resistances with increasing chimney temperatures.

Since a similar method was used in locating thermo- couples on free-standing liner A and the liners in chimneys No, 2 and No.

3,

temperature drops across these liners may be compared. Maximum temperature differences across liners in chimneys No.

2

and No.

3

are

14OF

and 24OP lower respectively than with the liner free standiilgatlOOOOP inlet flue gas temperature.

In

the free-standing test on liner

A

cracking occurred with a temperature drop across the wall of

9g°F.

!This temperature drop is exceeded in chimneys No,

2

and No.

3

at an inlet flue gas temperature of 1000°F. Furthermore, the mean temperature of the liners in the chimneys is higher at this inlet flue gas temperature than the mean temperature of the free-standing liner at

750°F

inlet temperature. Cracking

of the liners in these chimneys can be expected, therefore,

at

the

1000°F

flue gas inlet temperature. Cracking of the liner in chimney No. 2 might be reduced due to the restraint on the outer surface of the liner provided by the surrounding mortar and masonry.

S W R Y AND DISCUSSION

In

thermal tests on the full scale chimney in which typical surrounding construction was simulated, maximum

temperatures of framework and other combustibles were higher at the second floor level than at the first floor level. The maximum temperature of combustible construction occurred at the firestop in contact with the chimney. Floor temperatures were almost as high. Temperatures of combustibles attached at the corners of the chimney, as in the case of studs for the enclosure, were found to be lower than the floor or joist

temperatures and

it

would appear t h a t t h i s p r a c t i c e does n o t m a t e r i a l l y i n c r e a s e f i r e hazard.

For purposes of comparative t e s t i n g , s h o r t t e s t chimneys were found t o be adequate, R e l a t i v e thermal

r e s i s t a n c e s , c r a c k s and expansions of masonry chimneys were evaluated w i t h t h e s h o r t t e s t chimneys. A c l a y b r i c k s h o r t chimney was t e s t e d w i t h a f l o o r s e c t i o n t o compare i t s thermal performance w i t h t h a t of t h e f u l l s c a l e chimney. A t equal f l u e gas temperature a t t h e

f i r s t

f l o o r l e v e l , chimney s u r f a c e and framework temperatures were found t o be about t h e same f o r both chimneys.

The use of 1/8-in. a s b e s t o s i n s u l a t i o n between t h e baseboard and chimney s u r f a c e reduced t h e baseboard temperature 15 t o 20°F. I n s u l a t i o n placed between t h e j o i s t s and chimney r e s u l t e d i n h i g h e r f l o o r and baseboard temperatures. P i r e s t o p s placed a t t h e bottom of t h e j o i s t s had t h e same e f f e c t and a l s o m a t m i a l l y increased framework temperatures.

Thermal performance of t h e c l a y b r i c k chimneys w i t h

%he

l i n e r s grouted was compared w i t h t h e l i n e r s n o t grouted. The l a t t e r gave s l i g h t l y lower s u r f a c e temperatures. It

i s

believed t h a t t h e e f f e c t i v e n e s s of t h e i n s u l a t i n g a i r with t h e l i n e r s n o t grouted i s reduced due t o gas leakage through c r a c k s and mortar j o i ~ t s of t h e l i n e r s .

Chimney s u r f a c e temperatures f o r t h e concrete block chimney a t t h e end of 14-hr t e s t s gave s l i g h t l y lower tempera- t u r e s t h a n those of t h e c l a y b r i c k chirney. Hov~ever, t h e r a t e of temperature r i s e of t h e Indo chimneys showed h i g h e r thermal c a p a c i t y f o r t h e concrete block chimney and t h e s u r f a c e

temperatures f o r t h i s chimney may p o s s i b l y be h i g h e r a t

s t e a d y s t a t e condition. The o v e r - a l l r e s i s t a n c e t o h e a t flow of t h e concrete block chimney determined a t

1 4

h r vtas h i g h e r t h a n t h a t of t h e c l a y b r i c k chimney, Liners of g r e a t e r w a l l t h i c k n e s s were used f o r t h e concrete block chimney and t h e r e s i s t a n c e t o h e a t flow of t h e concrete block

was

found t o be

e q u i v a l e n t t o t h a t of t h e s i n g l e course c l a y b r i c k based on r e s u l t s a t

1 4

hours, However, t h e concrete block may give l e s s thermal r e s i s t a n c e t h a n t h a t of t h e c l a y b r i c k a t s t e a d y s t a t e condition,

The double course c l a y b r i c k chimney without a l i n e r gave much lower s u r f a c e temperatures a t t h e end of a

1 4

hour t e s t , due t o i t s h i g h e r r e s i s t a n c e t o h e a t flow and i t s thermal c a p a c i t y .

With t h e c l a y b r i c k chimney thermal expansion measurements i n d i c a t e d t h a t t h e v e r t i o a l expansion i s much g r e a t e r t h a n t h e h o r i z o n t a l expansi

a n ,

whereas with t h e c o n c r e t e block chimney expansions i n both d i r e c t i o n s a r e about t h e same. This may be due t o more numerous h o r i z o n t a l mortar j o i n l s of t h e c l a y b r i c k chimney with t h e s e p a r a t i o n a t t h e s e mor-i;zr j o i n t s adding t o t h e v e r t i c a l expansicln

measurements. The u n i t h o r i z o n t a l expansion of t h e c l a y b r i c k chimney

i s

almost h a l f tha-L- of t h e c o n c r e t e block chimney, whereas t h e u n i t v e r t i c a l expansion of t h e former i s twice t h a t of t h e l a t t e r .

Measurement of t h e a i r leakages of chimneys a f t e r t h e thermal t e s t g i v e s some i n d i c a t i o n of t h e r e l a t l v e amount

o f

c r a c k i n g of t h e chimneys. H a i r l i n e c r a c k s appeared i n t h e masonry d u r i n g t h e 500'3 thermal t e s t f o r t h e c o n c r e t e b l o c k chimney and d u r i n g 750'3 t h e m a l t e s t f o r t h e c l a y b r i c k chimneys, A f t e r t h e 1000°P t l ~ e r m a l t e s t , l i n e r c r a c k s were observed a t t h e i n l e t opening of some t e s t chimneys. A i r

leakage measurements gave a slight i n c r e a s e i n t h e r a t e of a i r leakage a f t e r t h e 500'3' and 750°P thermal t e s t s and a decided i n c r e a s e a f t e r t h e 1000°P t h e m a l t e s t . A f t e r t h e t h e r n a l shock t e s t , t h e c r a c k s i n t h e masonry and l i n e r s were e x t e n s i v e and t h e r a t e of a i r leakage r o s e s i g n i f i c a n t l y .

A i r leakages of t h e c l a y b r i c k chimneys measured a f t e r t h e thermal shock t e s t s were much h i g h e r w i t h t h e l i n e r s n o t grouted t h a n w i t h t h e l i n e r s grouted. A i r leakages measured a f t e r t h e thermal t e s t s mere about t h e same f o r b o t h c a s e s . On t h i s b a s i s it i s b e l i e v e d t h a t t h e rnol-tar behind t h e l i n e r s a s s i s t s i n reducing t h e a i r leakage of chirrieys s u b j e c t e d t o s e v e r e thermal shock. However, from t h e s e t e s t s t h e e f f e c t of t h e mortar on t h e c r a c k i n g o f t h e l i n e r i s n o t knovm. The

r e p o r t on chimney t e s t s by t h e National Bureau of Standards (1)

recommends no g r o u t i n g of l i n e r s f o r chimney c o n s t r u c t i o n .

This recommendation i s based. on t h e o b s e r v a t i o n of c o ~ ~ t i n u o u s c r a c k s through t h e l i n e r s and masonz-y of c h i r a e y s w i t h t h e

l i n e r s f u l l y grouted. Because o f t h e narrow space between t h e l i n e r and t h e chimney, t o f u l l y g r o u t t h e l i n e r i - b was n e c e s s a r y t o tamp t h e mortar in-to t h e space w i t h a s t e e l rod.

I n p r a c t i c e , t h e l i n e r s

are

probably only p a r t i a l l y grouted, The c o n c r e t e block chimney gave h i g h e r a i r leakages a f t e r t h e thermal shock t e s t s compared t o t h e c l a y b r i c k chirmey w i t h t h e l i n e r s grouted. A i r leakages o f t h e double course c l a y b r i c k chimney w i t h no l i n e r were h i g h e r f o r both s t e a d y t h e r n a l and thermal shock t e s t s t h a n t h o s e of a l l o t h e r chimneys. Besides providing a d d i t i o n a l thermal r e . s i s t a n c e

,

t h e l i n e r s a s s i s t s i g n i f i c a n t l y i n providing gas ti&-bness,

A i r leakage measurements were made w i t h t h e s h o r t chimneys p r e s s u r i z e d up t o

4

i n . w a t e r gauge. The chimney d r a f t i s u s u a l l y l e s s t h a n 0.10 i n , water gauge and t h e r a t e of a i r leakage a t t h i s p r e s s u r e d i f f e r e n t i a l was found t o be about 1 cfm a f t e r t h e s t e a d y t h e m a l t e s t s and about

3

cfm a f t e r t h e f i r s t t h e r a a l shock t e s t . I t i s b e l i e v e d t h e r a t e s of a i r leakage under a c t u a l d r a f t c o n d i t i o n s w i l l n o t s e r i o u s l y a f f e c t t h e chimney performance.

The c r a c k i n g of l i n e r s due t o thermal s t e s s i s