The CETIM 4th international fluid sealing symposium

The CETIM 4th international fluid sealing symposium

Feature The CETIM 4 t h intern a t i o n a l fluid sealing symposium T h e C e n t r e T e c h n i q u e d e s I n d u s t r i e s M e c a n i q u e ...

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The CETIM 4 t h intern a t i o n a l fluid sealing symposium T h e C e n t r e T e c h n i q u e d e s I n d u s t r i e s M e c a n i q u e s (CETIM) h e l d its 4 t h i n t e r n a t i o n a l s y m p o s i u m o n fluid s e a l i n g o f s t a t i c g a s k e t e d j o i n t s last m o n t h in M a n d e l i e u , n e a r C a n n e s in S o u t h e r n France. The principle t h e m e s w h i c h e m e r g e d f r o m t h i s well a t t e n d e d and s u c c e s s f u l c o n v e n t i o n were, i n e v i t a b l y , t h e r e c e n t b a n o n a s b e s t o s u s e in F r a n c e and e s t a b l i s h i n g c o m m o n a l i t y b e t w e e n A m e r i c a n and E u r o p e a n b o l t e d flange g u i d e l i n e s . This article will p r o v i d e a r o u g h o v e r v i e w o f t h e s e a l s papers p r e s e n t e d and t o p i c s c o v e r e d . The event attracted over 200 participants, a b o u t 65% of w h o m were French, over 30 seals papers and speakers, and a contingent of 17 exhibitors. Broadly, the presentations were divided into those from gasket manufacturers, laboratories and users, and those concerning specific applications and standardization efforts. Papers marked with an asterisk are written in French.

Gasket manufacturers M i n i m i z i n g e m i s s i o n s w i t h ePTFE gaskets using new gasket factors a c c o r d i n g t o DIN and EN... Presenting a comparison of the new US and E u r o p e a n standards, and the advantages of using the new gasket constants instead of the old m and y factors. The new constants give the user additional information a b o u t what leakage to expect and how to install a gasket to achieve required emission levels. The need for and interest in gasket test programs from the user's point of view is demonstrated. (Hans Tuckmantel) A contribution to the solution o f p r o b l e m s arising f r o m t h e a s b e s t o s s u b s t i t u t i o n by e x p a n d e d graphite... Arguing that there is little need for the substitution of asbestos fibre with another fibre type in flange gaskets and compressed packings. Non-fibrous, expanded graphite with metal foils, sheets, caps or wires is recommended. The paper demonstrates that an envelope of nearly gastight PTFE improves the sealability, and a metal cap improves the compressive and

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corrosion resistance in oxygen higher than 450°C. (Hans Tuckmantel) O p t i m i s e d s e a l i n g s y s t e m for g a s k e t s w i t h PTFE e n v e l o p e s . . . This paper highlights the need for the widely used sealing system of a corrugated stainless steel ring, compressed sheet inserts and PTFE envelope to be examined more rigorously with regards to its operational reliability, leak tightness and safety margins. A core material based on flexible graphite has been developed and optimised for this application. (A Hirschvogel) Repetitive sealing - poppet v a l v e applications*... Demonstrating that a resilient metallic seal, designed initially for static assemblies only, could be used for poppet valve applications. In well defined conditions the seals can be subjected to tightening/ loosening cycles without loss in sealing levels. (C Rouaud, P Caplain) M o t i v a t i o n for t h e replacem e n t o f a s b e s t o s in i n d u s t r i a l sealing*... A s u m m a r y of the reasons why legislative factors are not the only reasons industry should be conscious of the need for the replacement of asbestos. (A Servant) N o n - a s b e s t o s g a s k e t s for a w i d e range of applications*... Theoretical methods for replacing asbestos in industrial sealing applications, do not always stand up to real requirements. In order to take into a c c o u n t traditional maintenance methods and the need for rationalisation of non-asbestos sealing products, PTFE based gaskets are proposed with reticular and isotropic structures, specifically

targeted at the pharmaceutical and chemical industries where the temperature remains below 300°C. (A Servant) Factors which influence the performance of valve stem seals... Test a p p a r a t u s is described which allows the performance of control valve stem seals to be assessed in terms of both the rate of loss of pressure from a given volume of gas and m a s s leakage rate. The performance of m o d e r n valve stem seals is shown to be far in excess of the best of the previous generation of seals based on asbestos. (J Hoyes, L Thorpe} The Kempchen convex gasket*... Exploring the possibilities of a new "convex" gasket type, which facilitates high level sealing in h a r s h service conditions s u c h as flange torsion where pipes are subjected to transverse forces - and satisfying fire resistance and heat exchanger requirements. (P Funel) Finite element analysis of b o l t e d flange a s s e m b l i e s . . . Recent advances in the use of finite element analysis are described in the study of actual bolted flange assemblies. Using this a p p r o a c h to designing and u n d e r s t a n d i n g bolted flange assemblies is shown to provide joint integrity data to a degree which could not be determined by empirical means. (A Smith, G Briggs) The u t i l i z a t i o n o f K y n o l N o v o l o i d fibres in a s b e s t o s free g a s k e t s . . . The unique properties of these fibres are presented. Unlike any other organic fibre, for example, they do not melt at high temperature, b u t are instead carbonised. They are highly physically compatible with matrix elastomers and resins, and chemically cross link with m a n y of them, particularly with those which cure or vulcanize with heat. This permits m a n u facture of semi-cured gaskets which undergo final cure after installation, providing improved surface conformity. (Y Mizuta) PC s o f t w a r e for d e t e r m i n a t i o n of b o l t i n g p a r a m e t e r s in g a s k e t e d j o i n t s . . . A computer program has been developed which calculates all the necessary parameters to ensure the tightness of gasketed joints. For calculation of tightness and bolting parameters, the two different procedures of the FSA

Sealing Technology No. 34

Feature a n d t h e PVRC a r e t a k e n i n t o a c c o u n t . (F B e r n a r d , I B o r o v n i c a r , M Ghirland)

Creep and l e a k a g e p r o p e r t i e s of m o d i f i e d P T F E . . . T h e p r a c t i c e of c a t e g o r i z i n g g a s k e t m a t e r i a l s into b r o a d g r o u p s is q u e s t i o n e d h e r e for e x a m p l e , c o m p r e s s e d fibre m a t e r i a l s . PTFE a n d flexible graphite. Between each group there m a y a c t u a l l y be s m o o t h t r a n s i t i o n s and within each group there are m a t e r i a l s w i t h totally different p r o p e r t i e s . The c h a r a c t e r i s t i c s of PTFEs a r e d i s c u s s e d . (Dr J Latle, C Rossi)

Laboratories / u n i v e r s i t i e ~ D e t e r m i n a t i o n of l e a k a g e gap o f flange j o i n t s u n d e r n o n a x i s y m m e t r i c Ioadings, u s i n g non-linear gasket material... A finite e l e m e n l m o d e l w a s g e n e r a t e d to i n v e s t i g a l e t h e d e v e l o p m e n t of l e a k a g e g a p s of f l a n g e . j o i n t s c a u s e d b y e x t e r n a l m o m e n t s or, for e x a m p l e , holt l a i l u r e . T h e 3D 180 degrec model developed includes the s p e c i a l e l a s l i c ~ p l a s t i c m a t e r i a l behaviour and contact condition b e t w e e n g a s k e t a n d llange. R e s u l t s were c o m p a r e d w i l h e x p e r i m e n t a l d a t a fl-om a real llan~e. (R Kauer, U Steil, K S t r o h m e i e r )

N o n - c i r c u l a r b o l t e d flanged connections c o m p a r i s o n of d e s i g n m e t h o d s w i t h r e s u l t s of finite e l e m e n t a n a l y s i s . . . F r a m e b e n d i n g a n d o u t - o f p l a n e flange b e n d i n g a p p r o a c h e s to d e s i g n a r e discussed and matched with results from FEA. C a l c u l a t i o n s , experim e n t a l v a l u e s a n d FE r e s u l t s w e r e o b t a i n e d for s e v e r a l facing a n d gasket types including strip gaskets a n d full face g a s k e t s . (A Blach)

On t h e u s e o f a s i m p l e t e s t fixture as a reliable r e p r e s e n t a t i o n o f t y p i c a l ANSI B 1 6 . 5 flanged j o i n t r e l a x a t i o n behaviour... O v e r time, m a n y b o l t e d flanged j o i n t s left d u e Io t h e loss of bolt a n d ~{asket l o a d s c a u s e d by c r e e p r e l a x a t i o n of t h e g a s k e t e s p e c i a l l y at e l e v a t e d t e m p e r a t u r e s . T h e a u t h o r s u s e d a HATR s i m p l e fixture a l r e a d y d e v e l o p e d for g a s k e t s c r e e n i n g t e s t s lo i n v e s t i g a t e . S p e c i a l focus w a s p l a c e d on w e l d e d neck type tlan~es with sheet gaskeling and lheir behaxdour under blow-out conditions. (A Bouzid, M D e r e n n e )

C h a r a c t e r i z a t i o n of t h e h o t c r e e p / r e l a x a t i o n and g r o s s

S e a l i n g T e c h n o l o g y No. 3 4

l e a k a g e b e h a v i o u r of PTFE b a s e d gasket materlals... The Tightness T e s t i n g a n d R e s e a r c h L a b o r a t o r y of Ecole P o l y t e c h n i q u e of M o n t r e a l h a s completed an extensive test program which developed a protocol for qualifying t h e t i g h t n e s s a n d hot p e r f o r m a n c e of a wide r a n g e of KFFE g a s k e t s b a s e d on a d i r e c t m e a s u r e of t h e i r s h o r t t e r m h o t relaxation resistance and their m a r g i n of s a f e t y a g a i n s t blowout. (M D e r e n n e , L M a r c h a n d , J Payne)

C h a r a c t e r i s a t i o n of t w o different NPS b o l t e d flanged j o i n t s s u b j e c t e d to e x t e r n a l b e n d i n g m o m e n t s . . . T h e effects of b e n d i n g m o m e n t s on two b o l i e d flange j o i n t s - one w i t h weld n e c k flanges a n d one w i t h l a p j o i n t flanges - w e r e i n v e s t i g a t e d . T h e analysis showed that the bending m o m e n t h a s a n i m p o r t a n t effect on t h e t i g h t n e s s of t h e weld n e c k flanges, b u t no effect on t h e l a p j o i n t flange t i g h t n e s s . This b e h a v i o u r is r e l a t e d to t h e differing gasket contact stress distribution. (L M a r c h a n d , D Laviolette, M Derenne, Y Birembaut, T Ledauphin)

C o n c e p t s relating to g a s k e t d e s i g n data... D e s i g n d a t a philosophy and concepts are d i s c u s s e d , a n d n e w u s e r friendly design procedures, graphical and a l g e b r a i c a r e d e s c r i b e d . An e x t e n d e d a n a l y t i c a l g a s k e t m o d e l is p r e s e n t e d w h i c h i n c l u d e s factors not n o r m a l l y i n c l u d e d s u c h a s viscosity, iemperature and dimensional aspects such as ~asket thickness. (B Nau)

The s e a l i n g p e r f o r m a n c e of liquid s e a l a n t in flexible b o x - s h a p e flanged b o l t e d j o i n t s . . . E x p e r i m e n t s w e r e c o n d u c t e d lo o b s e r v e l e a k a g e from a b o x - s h a p e flanged j o i n t in w h i c h liquid s e a l a n t s a r e a p p l i e d to t h e interfaces between aluminium flexible flanges, a n d on b o l t e d j o i n t s with a s b e s t o s g a s k e t s . S e a l i n g performance using the conlact s t r e s s d i s t r i b u t i o n s at t h e i n t e r f a c e s w a s e x a m i n e d , a n d it w a s f o u n d t h a t t h e liquid s e a l a n t p e r f o r m e d better. (M Yoneno, T Sawa, H Kawamura)

S e a l i n g p e r f o r m a n c e o f pipe flange c o n n e c t i o n s w i t h full-face gaskets subjected to external b e n d i n g m o m e n t s . . . The effect of bolt p i t c h circle d i a m e t e r , g a s k e t material, internal pressure and e x t e r n a l b e n d i n g m o m e n t on t h e

contact stress distribution was m e a s u r e d . In o r d e r to m o n i t o r l e a k a g e , s e n s i t i v e p i n s . to w h i c h t h e s h a n k s s t r a i n g a u g e s were a t t a c h e d , w e r e e m b e d d e d in pipe flanges. It w a s f o u n d t h a t t h e performance was improved when l h e bolt p i t c h circle d i a m e t e r a n d Young's m o d u l u s of g a s k e t s a r e s m a l l . (T S a w a , T M o r o h o s h i , K Meguro)

~tlx~ltmlilt~ilm A s b e s t o s - f r e e m a t e r i a l s for g a s k e t s for b o l t e d f l a n g e d c o n n e c t i o n s . . . W i t h i n Brite E u R a m , the EC h a s s p o n s o r e d t h i s initiative. Project 5191, a s t u d y involving 22 i n d n s t r i a l p a r t n e r s . The p r o i e c t d e v e l o p e d g a s k e t l e s t i n g p r o c e d u r e s a n d , on l h e b a s i s of test results, adapted and optiimsed t h e s e m e t h o d s . It is i n t e n d e d t h a t l h e d e s c r i p t i o n c,l t h e s e t e s t s will form t h e b a s i s l~,r a CEN s t a n d a r d on g a s k e t testing. It w a s s h o w n t h a t the gasket factors defined were u s e f u l for t h e d e s i g n c a l c u l a t i o n of real flanged joints, b u t m o r e c a l c u l a t i o n s m u s t be c a r r i e d out usin~thenewEm-opean prEN 1591 S t a n d a r d . (H K o c k e h n a n n , Y Birembaut)

Verification of g a s k e t f a c t o r s d e t e r m i n e d in s t a n d a r d i z e d t e s t s by m e a n s of flanged j o i n t s . . . W i t h i n T a s k 9 of Project B E - 5 1 9 1 ~ a s k e t l e c t o r s r e l a t e d 1o l i g h t n e s s c h a r a c t e r i s l i c s w e r e verified in real flanged join {:s. at different pressures, temperatures and o p e r a t i n g fluids. B e s i d e s t h e gasket stress and the tightness c h a r a c t e r i s t i c s , lee d e f o r m a t i o n b e h a v i o u r of l h e < a s k e t h a s Io b e c o n s i d e r e d in t i g h t n e s s a s p e c t s . To establish the tightness characteristics, it m a y be n e c e s s a r y to k n o w the real g a s k e t s t r e s s , a n d ii w a s l o u n d t h a t this L{asket s t r e s s c a n only be c a l c u l a t e d u s i n g t h e e l a s t o plastic deformation behaviour of the g a s k e t . (J B a r l o n i c e k . H K o c k e l m a n n . J C Vi~naud, Y Birembaut)

D e t e r m i n a t i o n of g a s k e t behaviour against chemical a t t a c k and i n v e s t i g a t i o n of t h e s e a l i n g b e h a v i o u r o f g a s k e t s in b o l t e d flanged c o n n e c t i o n s w i t h liquid c h e m i c a l m e d i a s . . . T e s t i n g m e t h o d s w e r e e s i a b l i s h e d to d e t e r m i n e t h e c h a r a c t e r i s t i c s of c h e m i c a l a t t a c k on g a s k e t s in t e r m s of d a m a g e , c h a n < e s in m a s s ,

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Feature volume, leakage and mechanical behaviour as a function of service temperature, time and media. It was a complex matter to find simple evaluation tests as gasket materials showed s u c h very different results. Among those tested were CAF, aramid fibre, expanded graphite, and PTFE. (M Rommler) New rules for t h e d e s i g n of bolted gasket assemblies North A m e r i c a n and E u r o p e a n a p p r o a c h e s to g a s k e t characterisation*... The efforts by ASME to generate new rules to cover stresses and tightness in flange assemblies are compared with the E u r o p e a n draft design code pr EN 1591, which incorporates tightness and external loading. (Y Birembaut, T Ledauphin, J Vignaud, M Derenne, J Payne) An u p d a t e o n t h e PVRC b o l t e d flange r e s e a r c h program... This program has resulted in greatly enhanced u n d e r s t a n d i n g of the leakage p h e n o m e n a of a flanged joint. Test protocols and gasket qualification tools for elastomeric sheet and flexible graphite sheet materials are proposed, although fine tuning of these procedures is necessary t h r o u g h further studies. (K Hsu, J Payne, J Winter) C o m p a r i s o n of p r o p o s e d ASME rules for b o l t e d flanged j o i n t s . . . An ASME special working group is implementing the new PVRC gasket constants (Gb and Gs) along with several other changes to the traditional bolted flange design rules of Appendix 2 of the Code. The n a t u r e and effect of the new aspects of the proposed rules are discussed along with parametric comparisons of key ratios s u c h as bolt areas and m o m e n t s for a simple ring geometry and some detailed aspects of specific flanges. (J Payne, R Schneider) Sneciflc a n o l i c a t i o n s P r e s e n t a t i o n of an e m i s s i o n s r e d u c t i o n project b y I n n o T e c h / ECS o n a p e t r o c h e m i c a l site*... A real experience of operating a leak detection and repair program at ARCO Chimie Fos. The driving forces, the savings realised and improvements in hygiene, safety and the environment are recounted. (J Leygue, C Gaigneux) Fugitive e m i s s i o n s - n e w r e g u l a t i o n s for t h e p r o t e c t i o n of t h e e n v i r o n m e n t * . . . In the light of

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US and European environmental legislation, requiring in the first instance ppm m e a s u r e m e n t s of emissions, and in the second, g/h, CETIM embarked on a study for French Valve Manufacturers to evaluate correlation between the two. First proposals on standardised testing procedures for fugitive emissions control and qualification of industrial valves are offered. (J Garrigues, Y Birembaut, T Ledauphin) User8 E x p e r i e n c e with welded flanges*... Presenting some of the lessons learned in the field of large flanges. Big shell flanges for a pressure vessel were studied. A design was developed to avoid the problems of machining the piece economically, and welding and heat treating the connection between the shell and the flange. The authors finally propose a quick calculation guide for this type of flange. (G Robert) H o w to p r e v e n t l e a k a g e s from c r y o g e n i c b o l t e d assemblies*... Gaz de France has u n d e r t a k e n studies to better u n d e r s t a n d this process. Two problematic thermal p h e n o m e n a have been identified. The first is the temperature gap between the flange and bolts when the assembly is cooled down, and the second is the irreversible loss of tightening stress after each cooling and warming up cycle. Experimentation was the only way to learn to characterise the behaviour. (E Flesch, F Blanc) E v a l u a t i o n of bolt load in m e t a l - m e t a l c o n t a c t a c c o r d i n g to t h e RCC-M code*... A modification of the RCC-M code, appied to mechanical components of the nuclear island of a pressurised water reactor, is used to proposes a method specific to connection with metal to metal contact within a bolt circle submitted to axial load and bending moment, and method to verify the connection u n d e r transversal loading and torque moment. This paper establishes the basic principles of the verifications which will be required by the modification. (C Heng, T he Courtois, J Vignaud) R e c e n t e x p e r i e n c e s with inward b u c k l i n g of spiral w o u n d flexible graphite filled g a s k e t s for piping flanges... This paper serves to alert users of these gaskets to the potential for failure. Gaskets which complied fully with ASME B 16.20 requirements were shown to have

major instability problems u n d e r bolt-up. It highlights the need for industry wide attention to several apparent deficiencies in current design and m a n u f a c t u r i n g standards. (R Mueller) S u r v e y o n t h e s e a l i n g of b o l t e d j o i n t s in practice*... Electricit~ de France launched this international survey in order to u n d e r s t a n d how other fields of industry coped with sealing problems, u n a u t h o r i s e d rejects, fugitive emissions and the asbestos ban. Out of the 172 companies queried, 29% responded, of whom 90% considered sealing to be of great importance. The cost of maintenance for leakage prevention estimated variously at between 0 and 20% and the effect of leakage on production at between 1 and 100% - this latter case being a nuclear power plant. (J Vignaud, G Pierron) I m p r o v e m e n t s in t h e sealing of a h e a t exchanger*... A special partition gasket was set up in the water cistern in a heat exchanger. The solution involved Electricite de France, Latty International and the CETIM Laboratory. (R Cormier, C Brou) The qualification of seals at ultra-high v a c u u m and pressure o p e r a t i n g at a t e m p e r a t u r e of 1.8 K*... The large Hadron Collider project will be the next major high energy physics facility at CERN. Magnetic m e a s u r e m e n t s are made using a device where demountable seals are required. The seals m u s t be leaktight to v a c u u m , and m u s t also resist pressure b u r s t s up to 20 bar during resistive transitions. (J Brunet, A Jacquemod) Glycol reboiler c o v e r flange leakage - h o w t h e u s e of a special g a s k e t could s o l v e a difficult t i g h t n e s s s i t u a t i o n . . . Leakage at the flange of this reboiler had been observed for years, probably caused by the fact that it was singlehandedly supporting the six ton weight of two chimneys. A special corrugated gasket with soft layers in graphite was created, and a proper supporting structure built for the chimneys. (C Aubert) For full details of t h e CETIM conference proceedings, contact: The Fluid S e a l i n g and M e c h a n i c a l Calculation Dept., CETIM, 7 4 route de la Joneli~re, BP 7 6 1 7 , 4 4 0 7 6 N a n t e s Cedex 03, France. Tel: +33 2 4 0 3 7 3 6 3 5 ; Fax: +33 2 4 0 3 7 3699.

Sealing Technology No. 34