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Optimizing an advanced ceramic
Dynamic sealing
Optimizing an advanced ceramic
likely to u n d e r g o t h e t h e r m a l d i s t o r t i o n s t h a t c a n f o r m g a p s for a b r a s i v e m a t e r i a l to enter. A t u b e s h a p e a l s o e l i m i n a t e s t h e t e n d e n c y for s t i n g a n d f i b r o u s m a t e r i a l to c a t c h o n p r o j e c t i o n s , w i n d a r o u n d t h e r o t a t i n g p a r t s a n d c a u s e t h e faces to s e p a r a t e . O t h e r e l e m e n t s , s u c h a s t h e drive p i n s , s p r i n g s a n d s p r i n g h o l d e r s , a r e s u b j e c t e d to wear. In t h e n e w d e s i g n , all a s y m m e t r i c a l p a r t s , i n c l u d i n g t h e drive slots, w e r e p l a c e d i n s i d e t h e seal. T h e e x t e r i o r w a s thus made totally flush so that any turbulence that might induce wear was minimised. V a r i o u s m e a s u r e s w e r e t a k e n to p r e v e n t t h e a c c u m u l a t i o n of m a t e r i a l in t h e slot b e t w e e n t h e s e a l r i n g a n d t h e fixed p a r t , w h i c h c a n p o t e n t i a l l y c e m e n t t h e s e a l r i n g in p l a c e . F i r s t a n a d d i t i o n a l r u b b e r s h i e l d w a s i n s t a l l e d to p r o t e c t t h e slot from t h e p u m p e d m e d i u m . H e a t d i s s i p a t i o n from t h e n e a r b y s u r f a c e s w a s a l s o a c h i e v e d b y p l a c i n g t h e slot s o m e d i s t a n c e a w a y f r o m t h e s e a l face a n d b y cooling the area. T h e O - r i n g w a s p r e v e n t e d f r o m s t i c k i n g to its o u t e r face b y m o d i f y i n g t h e c r o s s - s e c t i o n so t h a t its s t i f f n e s s in t h e a x i a l d i r e c t i o n is low. W i t h t h i s m o d i f i c a t i o n , t h e r i n g is flexible e n o u g h to a c c o m m o d a t e t h e n e c e s s a r y t r a v e l in t h e a x i a l d i r e c t i o n even if it s t i c k s to its c o u n t e r s u r f a c e . F o r its overall sliding, w e a r a n d t o u g h n e s s characteristics, cemented carbide was chosen as the s e a l face m a t e r i a l . However, b e c a u s e c o b a l t - c e m e n t e d c a r b i d e is often s u b j e c t to c o r r o s i o n , t h e corrosion-sensitive binder was replaced by a more r e s i s t a n t alloy c o n t a i n i n g c h r o m i u m a n d nickel, among other materials. The new composition also r e s i s t s h e a t Checking m o r e effectively. T h e r m a l o v e r l o a d is likely to o c c u r if a p u m p r u n s d r y or if it c a r r i e s h o t l i q u i d s . In o r d e r to i m p r o v e t h e g e n e r a l d i s s i p a t i o n of h e a t . T h e n e w s e a l i n c o r p o r a t e s s e v e r a l m e a s u r e s . T h e r e is metal-to-metal contact between seal ring and pump h o u s i n g a n d f o r c e d oil c i r c u l a t i o n , s e a l r i n g m a t e r i a l s have high thermal conductivity, and large areas are e x p o s e d to c o o l i n g m e d i a . The seal performance was further improved by p l a c i n g it in a c h a m b e r s e p a r a t e from t h e p u m p volute. T h i s a r r a n g e m e n t r e d u c e s t h e i n t r u s i o n of solid p a r t i c l e s , a n d b e c a u s e t h e i m p e l l e r is s c r e e n e d it r e d u c e s t h e r o t a t i o n a l s p e e d of t h e m e d i u m . T h e s e f e a t u r e s s e r v e to l e n g t h e n t h e life of t h e seal.
Contact: J o h a n Brattall, ITT Flygt AB, S v e t a r v a g e n 12, Box 1 3 0 9 , Solna, S - 1 7 1 2 5 , S w e d e n . Tel: +46 8 6 2 7 6 5 0 0 ; Fax: + 4 6 8 6 2 7 6 9 0 0 .
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T i t a n i u m d i b o r i d e is one of t h e n e w a d v a n c e d c e r a m i c m a t e r i a l s w i t h a u n i q u e s e t of p r o p e r t i e s t h a t , like a l u m i n i u m , for m a n y y e a r s h a d n o t f o u n d c o m m e r c i a l a p p l i c a t i o n . A d v a n c e d R e f r a c t o r y T e c h n o l o g i e s is c u r r e n t l y d e v e l o p i n g t h e p r o d u c t to c a p i t a l i s e on its wear resistance, high temperature and machinability p r o p e r t i e s a n d offer c o m m e r c i a l v a l u e . T h e m a t e r i a l c a n b e u s e d in a v a r i e t y of a p p l i c a t i o n s i n c l u d i n g s e a l s , n o z z l e s a n d c u t t i n g tool c o m p o s i t e s . TiB2 c a n be c o m b i n e d w i t h a v a r i e t y of o t h e r n o n - o x i d e c e r a m i c m a t e r i a l s s u c h a s silicon c a r b i d e (SIC) a n d t i t a n i u m c a r b i d e (TIC), a n d w i t h oxide m a t e r i a l s , s u c h a s a l u m i n a (A1203) to i n c r e a s e t h e m e a n s t r e n g t h a n d f r a c t u r e t o u g h n e s s of the material. A R T s a y s t h a t w i t h t h e a r r i v a l of its t e c h n i c a l g r a d e of t i t a n i u m d i b o r i d e (TGF), w h i c h c a n b e r e a d i l y p r e s s u r e l e s s s i n t e r e d , t h e u s e s for TiB2 a r e e x p a n d i n g . A R T c o n t r o l s t h e c h e m i s t r y of t h e final p r o d u c t in a n u m b e r of w a y s , i n c l u d i n g t h e r a w materials used, the synthesis and the post-processing. P r o d u c t s w i t h low o x y g e n c o n t e n t a n d i m p u r i t i e s c a n b e d e l i v e r e d a n d even t h e s u r f a c e c h e m i s t r y of t h e p o w d e r c a n be c o n t r o l l e d . In a d d i t i o n to p o w d e r , A R T h a s d e v e l o p e d TiB2 w h i s k e r s , p r e f o r m s a n d d e n s e p a r t s for e n g i n e e r i n g a p p l i c a t i o n s .
Contact: A d v a n c e d Refractory T e c h n o l o g i e s Inc., 6 9 9 Hertel Avenue, Buffalo, New York 1 4 2 0 7 , USA. Tel: +1 7 1 6 8 7 5 4 0 9 1 ; Fax: +1 7 1 6 8 7 5 0 1 0 6 .
Packing m e e t s regulations at low cost Marlo has launched a new braided graphite c o m b i n a t i o n p a c k i n g , Style 396C. F o l l o w i n g e x t e n s i v e r e s e a r c h a n d d e v e l o p m e n t a n d field t e s t i n g , t h e p a c k i n g w a s d e s i g n e d to p r o v i d e e n d u s e r s w i t h a positive m e a n s to s e a l r i s i n g a n d fixed s t e m v a l v e s in t h e p r o c e s s i n d u s t r i e s . M a r l o c l a i m s it e x c e e d s EPA r e q u i r e m e n t s for fugitive e m i s s i o n s , h a v i n g p a s s e d t h e F u g i t i v e E m i s s i o n s T e s t p e r Exxon, Revision A, a n d API t e s t s 589 a n d 6 0 7 for valves. O n c e i n s t a l l e d , it p r o v i d e s s u p e r i o r r e c o v e r y of s e a l i n g e f f e c t i v e n e s s after m e c h a n i c a l u p s e t . At its h e a r t is a r e s i l i e n t core of i n t e r n a l l y - s p r u n g high temperature, high pressure graphite with helical b r a i d e d i n c o n e l wire, a n d a n o v e r b r a i d of c a r b o n - i n s e r t e d exfoliated g r a p h i t e foil t o r e s i s t e x t r u s i o n a n d f o r m a r o u n d s m a l l radii. T h e i n t e r n a l s t r u c t u r e e n a b l e s it to c o n f o r m a n d r e c o n f o r m t h r o u g h c o n s t a n t t e m p e r a t u r e c y c l i n g to v a r i o u s s t e m , bore and clearance conditions. Heavy wall thickness
Sealing Technology No. 3 4
Optimizing an advanced ceramic
likely to u n d e r g o t h e t h e r m a l d i s t o r t i o n s t h a t c a n f o r m g a p s for a b r a s i v e m a t e r i a l to enter. A t u b e s h a p e a l s o e l i m i n a t e s t h e t e n d e n c y for s t i n g a n d f i b r o u s m a t e r i a l to c a t c h o n p r o j e c t i o n s , w i n d a r o u n d t h e r o t a t i n g p a r t s a n d c a u s e t h e faces to s e p a r a t e . O t h e r e l e m e n t s , s u c h a s t h e drive p i n s , s p r i n g s a n d s p r i n g h o l d e r s , a r e s u b j e c t e d to wear. In t h e n e w d e s i g n , all a s y m m e t r i c a l p a r t s , i n c l u d i n g t h e drive slots, w e r e p l a c e d i n s i d e t h e seal. T h e e x t e r i o r w a s thus made totally flush so that any turbulence that might induce wear was minimised. V a r i o u s m e a s u r e s w e r e t a k e n to p r e v e n t t h e a c c u m u l a t i o n of m a t e r i a l in t h e slot b e t w e e n t h e s e a l r i n g a n d t h e fixed p a r t , w h i c h c a n p o t e n t i a l l y c e m e n t t h e s e a l r i n g in p l a c e . F i r s t a n a d d i t i o n a l r u b b e r s h i e l d w a s i n s t a l l e d to p r o t e c t t h e slot from t h e p u m p e d m e d i u m . H e a t d i s s i p a t i o n from t h e n e a r b y s u r f a c e s w a s a l s o a c h i e v e d b y p l a c i n g t h e slot s o m e d i s t a n c e a w a y f r o m t h e s e a l face a n d b y cooling the area. T h e O - r i n g w a s p r e v e n t e d f r o m s t i c k i n g to its o u t e r face b y m o d i f y i n g t h e c r o s s - s e c t i o n so t h a t its s t i f f n e s s in t h e a x i a l d i r e c t i o n is low. W i t h t h i s m o d i f i c a t i o n , t h e r i n g is flexible e n o u g h to a c c o m m o d a t e t h e n e c e s s a r y t r a v e l in t h e a x i a l d i r e c t i o n even if it s t i c k s to its c o u n t e r s u r f a c e . F o r its overall sliding, w e a r a n d t o u g h n e s s characteristics, cemented carbide was chosen as the s e a l face m a t e r i a l . However, b e c a u s e c o b a l t - c e m e n t e d c a r b i d e is often s u b j e c t to c o r r o s i o n , t h e corrosion-sensitive binder was replaced by a more r e s i s t a n t alloy c o n t a i n i n g c h r o m i u m a n d nickel, among other materials. The new composition also r e s i s t s h e a t Checking m o r e effectively. T h e r m a l o v e r l o a d is likely to o c c u r if a p u m p r u n s d r y or if it c a r r i e s h o t l i q u i d s . In o r d e r to i m p r o v e t h e g e n e r a l d i s s i p a t i o n of h e a t . T h e n e w s e a l i n c o r p o r a t e s s e v e r a l m e a s u r e s . T h e r e is metal-to-metal contact between seal ring and pump h o u s i n g a n d f o r c e d oil c i r c u l a t i o n , s e a l r i n g m a t e r i a l s have high thermal conductivity, and large areas are e x p o s e d to c o o l i n g m e d i a . The seal performance was further improved by p l a c i n g it in a c h a m b e r s e p a r a t e from t h e p u m p volute. T h i s a r r a n g e m e n t r e d u c e s t h e i n t r u s i o n of solid p a r t i c l e s , a n d b e c a u s e t h e i m p e l l e r is s c r e e n e d it r e d u c e s t h e r o t a t i o n a l s p e e d of t h e m e d i u m . T h e s e f e a t u r e s s e r v e to l e n g t h e n t h e life of t h e seal.
Contact: J o h a n Brattall, ITT Flygt AB, S v e t a r v a g e n 12, Box 1 3 0 9 , Solna, S - 1 7 1 2 5 , S w e d e n . Tel: +46 8 6 2 7 6 5 0 0 ; Fax: + 4 6 8 6 2 7 6 9 0 0 .
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T i t a n i u m d i b o r i d e is one of t h e n e w a d v a n c e d c e r a m i c m a t e r i a l s w i t h a u n i q u e s e t of p r o p e r t i e s t h a t , like a l u m i n i u m , for m a n y y e a r s h a d n o t f o u n d c o m m e r c i a l a p p l i c a t i o n . A d v a n c e d R e f r a c t o r y T e c h n o l o g i e s is c u r r e n t l y d e v e l o p i n g t h e p r o d u c t to c a p i t a l i s e on its wear resistance, high temperature and machinability p r o p e r t i e s a n d offer c o m m e r c i a l v a l u e . T h e m a t e r i a l c a n b e u s e d in a v a r i e t y of a p p l i c a t i o n s i n c l u d i n g s e a l s , n o z z l e s a n d c u t t i n g tool c o m p o s i t e s . TiB2 c a n be c o m b i n e d w i t h a v a r i e t y of o t h e r n o n - o x i d e c e r a m i c m a t e r i a l s s u c h a s silicon c a r b i d e (SIC) a n d t i t a n i u m c a r b i d e (TIC), a n d w i t h oxide m a t e r i a l s , s u c h a s a l u m i n a (A1203) to i n c r e a s e t h e m e a n s t r e n g t h a n d f r a c t u r e t o u g h n e s s of the material. A R T s a y s t h a t w i t h t h e a r r i v a l of its t e c h n i c a l g r a d e of t i t a n i u m d i b o r i d e (TGF), w h i c h c a n b e r e a d i l y p r e s s u r e l e s s s i n t e r e d , t h e u s e s for TiB2 a r e e x p a n d i n g . A R T c o n t r o l s t h e c h e m i s t r y of t h e final p r o d u c t in a n u m b e r of w a y s , i n c l u d i n g t h e r a w materials used, the synthesis and the post-processing. P r o d u c t s w i t h low o x y g e n c o n t e n t a n d i m p u r i t i e s c a n b e d e l i v e r e d a n d even t h e s u r f a c e c h e m i s t r y of t h e p o w d e r c a n be c o n t r o l l e d . In a d d i t i o n to p o w d e r , A R T h a s d e v e l o p e d TiB2 w h i s k e r s , p r e f o r m s a n d d e n s e p a r t s for e n g i n e e r i n g a p p l i c a t i o n s .
Contact: A d v a n c e d Refractory T e c h n o l o g i e s Inc., 6 9 9 Hertel Avenue, Buffalo, New York 1 4 2 0 7 , USA. Tel: +1 7 1 6 8 7 5 4 0 9 1 ; Fax: +1 7 1 6 8 7 5 0 1 0 6 .
Packing m e e t s regulations at low cost Marlo has launched a new braided graphite c o m b i n a t i o n p a c k i n g , Style 396C. F o l l o w i n g e x t e n s i v e r e s e a r c h a n d d e v e l o p m e n t a n d field t e s t i n g , t h e p a c k i n g w a s d e s i g n e d to p r o v i d e e n d u s e r s w i t h a positive m e a n s to s e a l r i s i n g a n d fixed s t e m v a l v e s in t h e p r o c e s s i n d u s t r i e s . M a r l o c l a i m s it e x c e e d s EPA r e q u i r e m e n t s for fugitive e m i s s i o n s , h a v i n g p a s s e d t h e F u g i t i v e E m i s s i o n s T e s t p e r Exxon, Revision A, a n d API t e s t s 589 a n d 6 0 7 for valves. O n c e i n s t a l l e d , it p r o v i d e s s u p e r i o r r e c o v e r y of s e a l i n g e f f e c t i v e n e s s after m e c h a n i c a l u p s e t . At its h e a r t is a r e s i l i e n t core of i n t e r n a l l y - s p r u n g high temperature, high pressure graphite with helical b r a i d e d i n c o n e l wire, a n d a n o v e r b r a i d of c a r b o n - i n s e r t e d exfoliated g r a p h i t e foil t o r e s i s t e x t r u s i o n a n d f o r m a r o u n d s m a l l radii. T h e i n t e r n a l s t r u c t u r e e n a b l e s it to c o n f o r m a n d r e c o n f o r m t h r o u g h c o n s t a n t t e m p e r a t u r e c y c l i n g to v a r i o u s s t e m , bore and clearance conditions. Heavy wall thickness
Sealing Technology No. 3 4