Modified PTFE Seat Suitability for CL150/300 Valves

[aggieengineerrmb]

Does anyone have any experience using valves with modified PTFE seats in typical oilfield services that may have some abrasives like sand present? The molecularly enhanced PTFE is simply PTFE that has a small amount (less that 1%)perfluoropropylvinylether (PPVE) added, which has no affect on chemical compatibilty or temperature capability, but does make it a stronger and more durable material than straight PTFE.

I'm looking at this only for lower pressure, CL150 and CL300 valves. We'd really like to use this material for the universal chemical resistance it provides, but there are some on our staff that fear that even the modified PTFE is not durable enough to resist cuts and wear when exposed to sand and other debris that will often be present in common oilfield fluids. The alternatives are some of the special nylons, however we would really have to pay close attention to the process fluid.

Any thoughts or experience from users would be helpful.

 

[unclesyd]

The problem we had with soft seated valves (teflon of all types) is that the teflon held the abrasive particles and abraded the ball or disk.

 

[within]

Sand and PTFE do not go together and should be avoided if possible. If the valve type is a globe (rising stem) then it is possible to protect the PTFE by building it into the plug and flowing over the plug head. In this way the PTFE does not see the highest pressure drop and the area of high velocity. This will extend the life slightly but not a great deal.

 

[aggieengineerrmb]

I should have mentioned this in the original message thread, but my question strictly involves suitability of the modified PTFE seats when used on floating ball valves.

 

[bcd]

The wear rate of modified PTFE is significantly better than PTFE, so in general, there is a substantial increase in cycle life. However, the addition of sand, weld slag, etc. is a different situation. You are dealing with abrasion and cutting, and the debris is significantly harder than the seat and ball. Modified PTFE or PTFE does not really matter, both will suffer equally. You will not observe much of a difference in cycle life. One benefit of PTFE is that it is much "softer" than metal, so debris easily embeds and limits the amount of damage to the ball. Going to a harder seat material without increasing the hardness of the ball only means deeper scratches in the ball. Some things that will help is hard coating the ball. Probably the lowest cost option. Then the choice to use Modifited PTFE versus PTFE is cycle life versus product cost evaulation. Another solution I have seen used is to put a hard seat material downstream like Nylon or PEEK, and then use a PTFE seat on the upstream side. In this case, the upstream seat is the primary seal, and the downstream seat, which suffers most of the damage from debris, acts as a bearing and keeps the ball in contact with the upstream seat. Still, hard coat the ball. Either option is much less expensive than going to metal seats.

 

[RXH]

PTFE (or any other "soft" material) and sand don't go together. Metal seated valves are recommended. I dont know what your application is, but if you are looking for zero or low leakage, you might try lubricated plug valves or the triple eccentric HPBV.

 

[AESINC]

american energy services makes valves for the dod and the space program. the valves are very reasonably priced.

try

http://www.aesvalves.com

 

[valvesrus]

Aggie, you might look at the offerings by Cameron,Mogus, and others. For produced fluids, metal seats are the standard for good reason.