- Email: [email protected]
Protector for drive shaft lip seal
Patents
p o s i t i o n e d on o p p o s i t e e n d s of the seal. The s i g n a l g e n e r a t e d i n r e s p o n s e to received r a d i a t i o n m a y be m e a s u r e d a n d s t o r e d b y a digital storage oscilloscope or o t h e r s i g n a l m e a s u r i n g device. With perlect seals, i n w h i c h a c a r b o n loaded 14asker a t t a c h e d to the door is in i n t i m a t e c o n t a c t with the deck, little or n o s i g n a l is received by the receiver. If the seal is n o t complete, r a d i a t i o n is transmitted through, and pulses are detected. As the seal is progressively b r e a c h e d , the m a g n i t u d e a n d s h a p e of the received signal c h a n g e s . The c o m p u t e r is p r o g r a m m e d to generate an a l a r m signal when a t h r e s h o l d v a l u e is exceeded, w a r n i n g t h a t the seal h a s b e e n breathed. In s i t u a t i o n s w h e r e a g a s k e t is not p r e s e n t , is n o t c o n s t r u c t e d of c a r b o n loaded r u b b e r , is r a d i a t i o n t r a n s m i s s i v e or if m i n o r b r e a c h e s of the seal c a n be tolerated, controlled trials m u s t be c a r r i e d o u t to d e t e r m i n e the received signal c h a r a c t e r i s t i c s w h e n the seal is c o r r u p t e d . This m e t h o d m a y also be s u i t a b l e lor m o n i t o r i n g the i n t e g r i t y of inetal c l o s u r e s in variety of situalions.
Protector for drive shaft lip seal
P
/ 10B /
26 25 F i g u r e 2. T h e s e a l i n g s y s t e m , w i t h s h a f t p r o t e c t o r f i t t e d .
t h e r e i n . In m a n y i n s t a n c e s the lip seal will be d a m a g e d b y this p r o c e d u r e , as the shaft is n o t perfectly s m o o t h a n d i n p a s s i n g t h r o u g h the e l a s t o m e r i e seal m a y a b r a d e , score a n d m u t i l a t e it. The b l u n t e n d of the drive shaft, w h e n p a s s i n g t h r o u g h the lip seal, m a y c a t c h a n d d i s t o r t its s h a p e , c a u s i n g the 360 ° r e t a i n e r s p r i n g in the s h o u l d e r of the lip seal to pop out. This will s u b s t a n t i a l l y r e d u c e seal life. The i n s t a l l a t i o n of a s e a l i n g s y s t e m is also a b l i n d p r o c e d u r e , as the i n s t a l l e r c a n n o t see into the b e a r i n g . The i n s t a l l e r therefore will n o t k n o w w h e t h e r the s p r i n g h a s b e e n dislodged. S i m i l a r p r o b l e m s are e n c o u n t e r e d w h e n retrofitting a s e a l i n g s y s t e m several
times i n the c o u r s e of a vessel's life. F i g u r e 2 s h o w s the s e a l i n g s y s t e m i n quesrJon. Coaxially m o u n t e d on the s h a f t l 0 is a lip seal 23, w h o s e i n t e r n a l wall is conically t a p e r e d a n d t e r m i n a t e s in r e s i l i e n t lip that frictionally e m b r a c e s the s h a f t s u r f a c e . The preferred e m b o d i m e n t of the protector device P is s h o w n m o r e clearly in F i g u r e 3. The u n i t is formed of a relatively stiff b u t frangible s y n t h e t i c p l a s t i c m a t e r i a l s u c h as polyvinyl chloride. It h a s a top h a t s h a p e with a p a i r of t a b s e x t e n d i n g diametrically. Score lines S m a k e the p r o t e c t o r w e a k e n o u g h to t e a r or rip it off the shaft. To u s e the device, the p r o t e c t o r is telescoped into the lip seal before
Patent number: US5503404 P u b l i c a t i o n d a t e : 2 April 1 9 9 6 Inventors: J Newton, J Strong This i n v e n t i o n g e n e r a l l y d e s c r i b e s a s e a l i n g s y s t e m lor the drive s h a f t of a m a r i n e propeller. T h e s y s t e m i n c l u d e s a b e a r i n g a n d a lip seal comxial with the s h a f t m o u n t e d a d j a c e n t to one e n d of the b e a r i n g . More p a r t i c u l a r l y , prior to i n s t a l l a t i o n , a s y s t e m of this type is provided with a p r o t e c t o r h a v i n g a sleeve t h a t telescopes i n t o t h e lip seal. a n d p r e v e n t s d a m a g e d u r i n g the c o u r s e of i n s t a l l a t i o n . W h e n i n s t a l l i n g this type of s e a l i n g s y s t e m , the i n b o a r d e n d of the drive shaft i l l u s t p a s s t h r o u g h the bearinK a n d the lip seal m o u n t e d
Sealing Techr~ology No. 31
P''~ ~w,~/26
27 F i g u r e 3. A f t e r u s e , t h e s c o r e l i n e s S e n a b l e t h e p r o t e c t o r t o b e r i p p e d off the shaft.
13
Patents the sealing a s s e m b l y is installed. The sleeve gently e x p a n d s the lip seal a n d p r o t e c t s it w h e n the shaft is inserted. Once the shaft is fitted, the p r o t e c t o r is w i t h d r a w n a n d r i p p e d off the shaft.
Rigid sheet PTFE material Patent number: WO9613676 P u b l i c a t i o n date: 9 May 1 9 9 6 I n v e n t o r s : J Dolan, D Mills A p p l i c a n t : W L Gore This p a t e n t d e s c r i b e s an improved m a t e r i a l s u i t a b l e for g a s k e t i n g a n d other sealing a p p l i c a t i o n s . It c o m p r i s e s a c o m p o s i t e s h e e t of flexible c o n f o r m a b l e PTFE layers b o n d e d to at l e a s t one e m b e d d e d layer of densified e x p a n d e d PTFE. The c o m p o s i t e m a t e r i a l is quite rigid, while r e t a i n i n g the a d v a n t a g e s of c o n v e n t i o n a l e x p a n d e d PTFE. The u s e of c o n f o r m a b l e o u t e r layers provides good sealing p r o p e r t i e s , e n a b l i n g it
to fill gaps a n d imperfections between sealing surfaces. The m a t e r i a l will keep its position d u r i n g cutting a n d m o u n t i n g . Additionally, the material is c o n s i s t e n t a c r o s s its entire surface, allowing it to be cut or modified into a n y variety of s h a p e s . Figure 4 shows a version of the p r o p o s e d material. The sheet m a t e r i a l c o m p r i s e s external layers of a p o r o u s e x p a n d e d PTFE m e m b r a n e a n d a core m a t e r i a l of a higher rigidity PTFE m e m b r a n e . The external layers are c o n s t r u c t e d from a flexible, conformable m a t e r i a l which is chemically inert, s u c h as Goretex GR. The s h e e t h a s a t h i c k n e s s ranging from 0.0254 to 25 m m a void volume of 40 to 85%, a l o n g i t u d i n a l tensile s t r e n g t h of a b o u t 22 to 38 Mpa a n d a t r a n s v e r s e tensile s t r e n g t h of a b o u t 11 to 22 Mpa. The m a t e r i a l is soft to t o u c h a n d will readily conform to imperfections in sealing surfaces. These layers m a y be a t t a c h e d to the core m a t e r i a l by adhesive or melting. The rigidity of the p r o p o s e d m a t e r i a l is s u p p l i e d by the core, which is sufficiently stiff to p r e v e n t
i 12
1
~
~
~-,'.~:..-~';" ~..: ~..,..:~.'.:~...-.~. ~ . \ ,~,
Figure 4. T h e m a t e r i a l g e t s i t s r i g i d i t y f r o m a d e n s i f l e d PTFE c o r e .
the g a s k e t from "flopping" w h e n held on edge. The core m a t e r i a l consists of e x p a n d e d PTFE layers which are e s s e n t i a l l y s i n t e r e d together in a v a c u u m . C o m p a r a t i v e t e s t s were p e r f o r m e d on the m a t e r i a l as well as conventional g a s k e t m a t e r i a l s of Goretex GR a n d Gylon. The tests p e r f o r m e d i n c l u d e d creep relaxation, sealability, compressibility/recoveryand rigidity. The r e s u l t s are s u m m a r i s e d in Table 1. The m a t e r i a l provides a n even sealing a r e a a c r o s s its entire surface m a y be readily c u t into a n y desired s h a p e a n d can w i t h s t a n d t e m p e r a t u r e s up to 315°C.
Sealing assembly with undercut groove Patent number: US5511518 P u b l i c a t i o n date: 3 0 April 1 9 9 6 I n v e n t o r s : J Balbir, J I n c l o n g Applicant: Fel Pro I n c . This invention r e l a t e s to sealing a s s e m b l i e s for u s e with i n t e r n a l c o m b u s t i o n engines. Various c o m p o n e n t s of i n t e r n a l c o m b u s t i o n engines require g a s k e t s for p r o p e r sealing a g a i n s t leakage of fluids. Prior sealing a s s e m b l i e s s u g g e s t e d for these a p p l i c a t i o n s involved providing a groove in one of the engine p a r t s , s u c h as in a n a p p r o p r i a t e metal engine part. A m o u l d e d g a s k e t is i n s e r t e d a n d r e t a i n e d by the wails of the groove. The initial a s s e m b l y of s u c h g a s k e t s is difficult a n d s o m e t i m e s
Table 1: Material performance comparison. Creep relaxation % Material
Thickness mm
23°C
100°C
Sealability 32/500 Microinch
Rigidity (Degrees) Comp/Rec
Mpa
Unwtd
Operating Temp. Limitations
Wtd
(°C)
Gore-tex GR sheet gasketing
1.9
36.5
61.8
22.4/34.5
62.7/12.1
44
75
315
Rigid sheet (Figure 4)
1.4
19.1
55
21.9 / 23.4
27.1 / 26
16
43
315
Gylon 3504
1.6
33.8
85.3
17.6 / 30.3
35 / 30
2.0
12.7
260
14
Sealing Technology No. 31
p o s i t i o n e d on o p p o s i t e e n d s of the seal. The s i g n a l g e n e r a t e d i n r e s p o n s e to received r a d i a t i o n m a y be m e a s u r e d a n d s t o r e d b y a digital storage oscilloscope or o t h e r s i g n a l m e a s u r i n g device. With perlect seals, i n w h i c h a c a r b o n loaded 14asker a t t a c h e d to the door is in i n t i m a t e c o n t a c t with the deck, little or n o s i g n a l is received by the receiver. If the seal is n o t complete, r a d i a t i o n is transmitted through, and pulses are detected. As the seal is progressively b r e a c h e d , the m a g n i t u d e a n d s h a p e of the received signal c h a n g e s . The c o m p u t e r is p r o g r a m m e d to generate an a l a r m signal when a t h r e s h o l d v a l u e is exceeded, w a r n i n g t h a t the seal h a s b e e n breathed. In s i t u a t i o n s w h e r e a g a s k e t is not p r e s e n t , is n o t c o n s t r u c t e d of c a r b o n loaded r u b b e r , is r a d i a t i o n t r a n s m i s s i v e or if m i n o r b r e a c h e s of the seal c a n be tolerated, controlled trials m u s t be c a r r i e d o u t to d e t e r m i n e the received signal c h a r a c t e r i s t i c s w h e n the seal is c o r r u p t e d . This m e t h o d m a y also be s u i t a b l e lor m o n i t o r i n g the i n t e g r i t y of inetal c l o s u r e s in variety of situalions.
Protector for drive shaft lip seal
P
/ 10B /
26 25 F i g u r e 2. T h e s e a l i n g s y s t e m , w i t h s h a f t p r o t e c t o r f i t t e d .
t h e r e i n . In m a n y i n s t a n c e s the lip seal will be d a m a g e d b y this p r o c e d u r e , as the shaft is n o t perfectly s m o o t h a n d i n p a s s i n g t h r o u g h the e l a s t o m e r i e seal m a y a b r a d e , score a n d m u t i l a t e it. The b l u n t e n d of the drive shaft, w h e n p a s s i n g t h r o u g h the lip seal, m a y c a t c h a n d d i s t o r t its s h a p e , c a u s i n g the 360 ° r e t a i n e r s p r i n g in the s h o u l d e r of the lip seal to pop out. This will s u b s t a n t i a l l y r e d u c e seal life. The i n s t a l l a t i o n of a s e a l i n g s y s t e m is also a b l i n d p r o c e d u r e , as the i n s t a l l e r c a n n o t see into the b e a r i n g . The i n s t a l l e r therefore will n o t k n o w w h e t h e r the s p r i n g h a s b e e n dislodged. S i m i l a r p r o b l e m s are e n c o u n t e r e d w h e n retrofitting a s e a l i n g s y s t e m several
times i n the c o u r s e of a vessel's life. F i g u r e 2 s h o w s the s e a l i n g s y s t e m i n quesrJon. Coaxially m o u n t e d on the s h a f t l 0 is a lip seal 23, w h o s e i n t e r n a l wall is conically t a p e r e d a n d t e r m i n a t e s in r e s i l i e n t lip that frictionally e m b r a c e s the s h a f t s u r f a c e . The preferred e m b o d i m e n t of the protector device P is s h o w n m o r e clearly in F i g u r e 3. The u n i t is formed of a relatively stiff b u t frangible s y n t h e t i c p l a s t i c m a t e r i a l s u c h as polyvinyl chloride. It h a s a top h a t s h a p e with a p a i r of t a b s e x t e n d i n g diametrically. Score lines S m a k e the p r o t e c t o r w e a k e n o u g h to t e a r or rip it off the shaft. To u s e the device, the p r o t e c t o r is telescoped into the lip seal before
Patent number: US5503404 P u b l i c a t i o n d a t e : 2 April 1 9 9 6 Inventors: J Newton, J Strong This i n v e n t i o n g e n e r a l l y d e s c r i b e s a s e a l i n g s y s t e m lor the drive s h a f t of a m a r i n e propeller. T h e s y s t e m i n c l u d e s a b e a r i n g a n d a lip seal comxial with the s h a f t m o u n t e d a d j a c e n t to one e n d of the b e a r i n g . More p a r t i c u l a r l y , prior to i n s t a l l a t i o n , a s y s t e m of this type is provided with a p r o t e c t o r h a v i n g a sleeve t h a t telescopes i n t o t h e lip seal. a n d p r e v e n t s d a m a g e d u r i n g the c o u r s e of i n s t a l l a t i o n . W h e n i n s t a l l i n g this type of s e a l i n g s y s t e m , the i n b o a r d e n d of the drive shaft i l l u s t p a s s t h r o u g h the bearinK a n d the lip seal m o u n t e d
Sealing Techr~ology No. 31
P''~ ~w,~/26
27 F i g u r e 3. A f t e r u s e , t h e s c o r e l i n e s S e n a b l e t h e p r o t e c t o r t o b e r i p p e d off the shaft.
13
Patents the sealing a s s e m b l y is installed. The sleeve gently e x p a n d s the lip seal a n d p r o t e c t s it w h e n the shaft is inserted. Once the shaft is fitted, the p r o t e c t o r is w i t h d r a w n a n d r i p p e d off the shaft.
Rigid sheet PTFE material Patent number: WO9613676 P u b l i c a t i o n date: 9 May 1 9 9 6 I n v e n t o r s : J Dolan, D Mills A p p l i c a n t : W L Gore This p a t e n t d e s c r i b e s an improved m a t e r i a l s u i t a b l e for g a s k e t i n g a n d other sealing a p p l i c a t i o n s . It c o m p r i s e s a c o m p o s i t e s h e e t of flexible c o n f o r m a b l e PTFE layers b o n d e d to at l e a s t one e m b e d d e d layer of densified e x p a n d e d PTFE. The c o m p o s i t e m a t e r i a l is quite rigid, while r e t a i n i n g the a d v a n t a g e s of c o n v e n t i o n a l e x p a n d e d PTFE. The u s e of c o n f o r m a b l e o u t e r layers provides good sealing p r o p e r t i e s , e n a b l i n g it
to fill gaps a n d imperfections between sealing surfaces. The m a t e r i a l will keep its position d u r i n g cutting a n d m o u n t i n g . Additionally, the material is c o n s i s t e n t a c r o s s its entire surface, allowing it to be cut or modified into a n y variety of s h a p e s . Figure 4 shows a version of the p r o p o s e d material. The sheet m a t e r i a l c o m p r i s e s external layers of a p o r o u s e x p a n d e d PTFE m e m b r a n e a n d a core m a t e r i a l of a higher rigidity PTFE m e m b r a n e . The external layers are c o n s t r u c t e d from a flexible, conformable m a t e r i a l which is chemically inert, s u c h as Goretex GR. The s h e e t h a s a t h i c k n e s s ranging from 0.0254 to 25 m m a void volume of 40 to 85%, a l o n g i t u d i n a l tensile s t r e n g t h of a b o u t 22 to 38 Mpa a n d a t r a n s v e r s e tensile s t r e n g t h of a b o u t 11 to 22 Mpa. The m a t e r i a l is soft to t o u c h a n d will readily conform to imperfections in sealing surfaces. These layers m a y be a t t a c h e d to the core m a t e r i a l by adhesive or melting. The rigidity of the p r o p o s e d m a t e r i a l is s u p p l i e d by the core, which is sufficiently stiff to p r e v e n t
i 12
1
~
~
~-,'.~:..-~';" ~..: ~..,..:~.'.:~...-.~. ~ . \ ,~,
Figure 4. T h e m a t e r i a l g e t s i t s r i g i d i t y f r o m a d e n s i f l e d PTFE c o r e .
the g a s k e t from "flopping" w h e n held on edge. The core m a t e r i a l consists of e x p a n d e d PTFE layers which are e s s e n t i a l l y s i n t e r e d together in a v a c u u m . C o m p a r a t i v e t e s t s were p e r f o r m e d on the m a t e r i a l as well as conventional g a s k e t m a t e r i a l s of Goretex GR a n d Gylon. The tests p e r f o r m e d i n c l u d e d creep relaxation, sealability, compressibility/recoveryand rigidity. The r e s u l t s are s u m m a r i s e d in Table 1. The m a t e r i a l provides a n even sealing a r e a a c r o s s its entire surface m a y be readily c u t into a n y desired s h a p e a n d can w i t h s t a n d t e m p e r a t u r e s up to 315°C.
Sealing assembly with undercut groove Patent number: US5511518 P u b l i c a t i o n date: 3 0 April 1 9 9 6 I n v e n t o r s : J Balbir, J I n c l o n g Applicant: Fel Pro I n c . This invention r e l a t e s to sealing a s s e m b l i e s for u s e with i n t e r n a l c o m b u s t i o n engines. Various c o m p o n e n t s of i n t e r n a l c o m b u s t i o n engines require g a s k e t s for p r o p e r sealing a g a i n s t leakage of fluids. Prior sealing a s s e m b l i e s s u g g e s t e d for these a p p l i c a t i o n s involved providing a groove in one of the engine p a r t s , s u c h as in a n a p p r o p r i a t e metal engine part. A m o u l d e d g a s k e t is i n s e r t e d a n d r e t a i n e d by the wails of the groove. The initial a s s e m b l y of s u c h g a s k e t s is difficult a n d s o m e t i m e s
Table 1: Material performance comparison. Creep relaxation % Material
Thickness mm
23°C
100°C
Sealability 32/500 Microinch
Rigidity (Degrees) Comp/Rec
Mpa
Unwtd
Operating Temp. Limitations
Wtd
(°C)
Gore-tex GR sheet gasketing
1.9
36.5
61.8
22.4/34.5
62.7/12.1
44
75
315
Rigid sheet (Figure 4)
1.4
19.1
55
21.9 / 23.4
27.1 / 26
16
43
315
Gylon 3504
1.6
33.8
85.3
17.6 / 30.3
35 / 30
2.0
12.7
260
14
Sealing Technology No. 31