Psuedo Cryogenic Floating Ball Valve

[aggieengineerrmb]

We are considering modifying one of our standard, API 6D flanged floating ball valves for use in a cryogenic application with the potential for temperatures as low as -150F. It's a shutdown valve going in front of a relief valve. Normal operating temperature is literally ambient, however in the event the relief valve blows, it's possible that the valve might see -150F. The valve is always open, and would only be closed if there is an event. This valve does not have extended bonnets, and customer understands that the valve might ice over and he would not be able to operate it until it warms up.

Our normal low temperature for this particular valve has historically been -50F due to the limitations of the o-rings used to seal the stem and between the body and the adapters. I can see no reason that we should not be able to rate this valve down to -150F for this service if we replace the o-rings with special spring energized PTFE lip seals. The materials for the body/adapter/ball are 316SS and the seats are Devlon, which both appear to easily handle these temperatures.

Does anyone know of something I might be overlooking that would cause problems?

 

[asukid99]

Actually, if I were the customer I would worry about the valve leaking throught packing if it sees liquids when the safety lifts. If their process can only be vapor phase then your are OK, but if there is anyway liquid can get into that line then extended bonnet is a must. (Unless you don't mind souring the relationshipo with your customer.)

 

[NGiLuzzu]

aggieengineerrmb,
I think you've considered the cost for this valve "retrofitting" (seals and packing replacement, work hours, etc.) compared to the one of a new valve, of course: but is the difference between the two worth of the possible risks?

In any case, I would suggest to contact the valve Manufacturer and/or to duplicate this post within the Valve Engineering Forum (forum408).

Hope this helps, 'NGL

 

[Burdy]

Proving the design is going to be difficult and expensive for you if you have no Low Temp testing facility. whilst you may solve the customers problem with your valve now, what are the risks that the valve will actually have a very short life? What are the risks for failure?
Why not as NGL says go to another manufacturer who has got this experience(unless it is an area/product range you want to get into)and badge it up accordingly?
I have spent considerable time in developing and testing cryogenic valves, the costs involved can be quite considerable.
Best of luck
Berni