Cavity type valves in LPG service 3

[HariAugustine]

Ball valves or plug valves (cavity type valves) are sometimes used in LPG service. with reference to thermal expansion and closimg the valve effectively blocking LPG in the cavity. What would you specify for valves in such a service?

 

[dcasto]

If the valve has two seals and a cavity, then a check valve in a line from the body volume to the line is required.

 

[BenThayer]

some valves have a hole in the ball to relief pressure.

also, some ball valves such as Jamesbury relief to the upstream (high pressure) side. this is due to the ball floating slightly to one side and the seal on the opposite side relieves.

check with the manufacturers.

 

[gerhardl]

Some manufacturers produce ball valves especially for this service, adapted to temperature and relief of pressure, and materials, sealings (including stem sealings and long neck)to suit the media.

Stick to theese, and ask or demand references on previous similar service.

 

[djack77494]

Hari,
You've gotten some good advise. This is not a job for an "off the shelf" valve. Better to use one specifically designed for liquified gases. Ball valves with a floating ball or valves with a hole drilled from one side into the cavity essentially eliminate one of the two seals. As dcasto says, you could run a seperate line with check valve to drain the cavity, but I think it's far better to go with the made for purpose valve.
Doug

 

[dcasto]

We always use off the shelf WKM, Gator, and TK valves.