PCTFE and RPTFE
PCTFE and RPTFE
(OP)
Can someone explain the suitability of RPTFE and PCTFE for ball valve seating?
Can we say that PEEk is the best seat material?
Can we say that PEEk is the best seat material?
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RE: PCTFE and RPTFE
RTFE is reinforced (typically glass) seating. It is better and will be suitable to valves with higher pressures but may still be limiting in Class 900 and 1500 valves which might not be able to have full flange rating. Again, immune to most environments.
PEEK is good to all ASME pressure classes and is highly resistant to most environments. Great seat material but extremely expensive. It is also unlikely to pass a low pressure valve test (such as in API 598) as the material is so tough.
Nylon is a commonly specified seat material for valves up to Class 1500 as it allows higher ratings than teflon and is relatively inexpensive. There is conflicting data available with regards to the suitability of Nylon in sour service.
RE: PCTFE and RPTFE
RE: PCTFE and RPTFE
Heather Smith
My interests: Alloy valves, duplex valves, super duplex valves, 6Moly valves, inconel valves, incoloy valves, alloy 20 valves and titanium valves.
RE: PCTFE and RPTFE
In addition, you have to look carefully at how the PEEK is manufactured. It can affect the properties tremendously. At about 6 inch and smaller diameter bar, it is typically injection molded. Elongation is around 20%, so the seat will be somewhat flexible. Once you get larger than 6 inch, it is typically compression molded from powder. The elongation drops to 2%. It doesn't flex very much until it breaks.
Just mentioning because you have to be very careful when working with PEEK.
RE: PCTFE and RPTFE
Heather's advise is sound. Without knowing the application, the question really can't be answered.
Regards,
donf
RE: PCTFE and RPTFE
I can add that I used Kel-F material on Cryogenic PRV's & PEEK for high temps.
http://www.boedeker.com/pctfe_p.htm
Ciao,