Cryogenic Valve Seat 1

[FFV5]

Has anybody tried Vespel for Cryogenic valve seats? Any comments on the performance is most welcome.

 

[NGiLuzzu]

As far as I can understand, FFV5 question is not about cryogenic extension bonnets (meant to take the valve stem sealing system away from the cold fluid), but about the internal, main sealing system (seat and obturator) of the valve.

Regards,
'NGL

 

[abscott]

FFV5,
I have used Vespel for valve seats but only in nuclear applications where the cost could be justified. These applications were typical power plant valves at water and steam temperatures.

We have made thousands of globe cold box valves and the typical valve soft seat material is Kel-F PCTFE (PolyChloroTriFluoroEthylene). The characteristics are very similar to PTFE but there is some marginal flexability at cryogenic temperatures.

Kel-F was developed by 3M but the only remaining source is Daikin Industries in Japan.
Hope this helps,
ABScott

 

[FFV5]

Yup Thanks abscott for your comments. I was choosing between Vespel and Kel-F. Our internal tests has revealed that the coefficient of thermal expansion of Kel-F is more unpredictable as compared to Vespel. In addition, Vespel seems to be able to take a higher pressure. I thought it might be sutable to be use for high pressure cryogenic valve seats but I would like to gather some reviews.

 

[HDS]

Arkema also makes PCTFE in the EU.

http://www.arkema-inc.com/index.cfm?pag=110

The crystalinity of PCTFE can vary. That maybe the source of the variation in CTE.

What do you consider high pressure?

 

[bogiedreamer]

Meldin is the same as Vespel at half the cost.