PEEK Seated Ball Valve Sealing

Question

PEEK Seated Ball Valve Sealing

aggieengineerrmb (Mechanical)

(OP)

10 Jun 04 10:08

Does anyone know what the expectations are in the industry for sealing quarter-turn, trunnion mounted ball valves when using PEEK as the materail for the seat?

All the valves I am concerned with are API-6D complaint, and I know that this standard requires zero leakage between the ball and seat, with H20 or a gas like air or N2. We can achieve a reasonably reliable seal using H20 as the test media, but really struggle getting these valves to seal when a gas is used. The problems occur at both high and low pressure, but it is most difficult to achieve a seal at low pressures.

Are there manufacturers out there that can achieve a bubble tight seal reliably with PEEK seats in a gas test. My experience is we can sometimes achieve a seal, but cycle the valve 2-3 times is all it takes to get some minute scratches in the ball and/or seat and small leaks can occur. Are we chasing our tail trying to achieve a level of sealing that no one in the industry really expects or even requires?

Boru (Mechanical) · Answer 1 · 2004-06-11 10:38:22

Our experience as a quartet turn valve manufacturer is similar. We have started to tell clients that PEEKs sealing propertie is more like a metals than a Teflon seated valve. Therefore we offer Class IV shutoff with PEEK instead of Class VI.

bcd (Mechanical) · Answer 2 · 2004-06-11 16:37:17

We also build quarter-turn trunnion and floating ball valves with PEEK seats. Bubble-tight shut-off is possible at low (50 psi) and high pressure (ANSI 150, 300, and 600 max.). Not bragging, honestly, we have had some initial challenges, but have made it work.

bcd

zztop (Mechanical) · Answer 3 · 2004-06-30 01:45:33

Personally, I suggest Peek for low pressure and high temperature to achieve a good sealing. Peek behaves then in a "smooth" way. That is what I have always heard.

scalleke (Mechanical) · Answer 4 · 2004-08-21 23:03:26

What Peek material though? Arlon 1550, 1330 or ????

What about metal seated valves.

Best regards.

Scalleke

PSVEngineer (Mechanical) · Answer 5 · 2004-08-26 09:44:44

We use Peek exclusively in PSVs above 1200-PSI, and achieve API-527 with it. High attention to detail in the mating surface with the valve is critical. Peek machines like a soft metal, and with force (of the valve action), seals like rubber, plus no closure deformation (critical when you have 700-lbs of compressed spring above it!).

Engineering Note #1: Amateurs built the Ark, Professionals built the Titanic - unknown

PSVEngineer

zztop (Mechanical) · Answer 6 · 2004-09-06 04:44:23

PSVengineer,

So you mean that you leave PEEK seat act like a spring...?
That is the way I always heard.

David

Come Join Us!

Posting Guidelines

PEEK Seated Ball Valve Sealing