Liquid Relief Kit requirement

[Ash-]

Hello all,
I have a DIB1 valve (10") that is used on a propane line; Propane's operating temperature is 150F and Operating pressure is 220 psia. At normal operating condition, propane is in vapor phase; However, in case of the valve closer, the temperature inside the valve cavity can fall below 110F (due to heat loss) and become liquid.

API 6D states:
"The manufacturer shall determine if the valve design could result in liquid being trapped in the body cavity in the open- and/or closed-valve position.

If liquid trapping is possible, the valve shall be provided with automatic cavity relief."

Now my question is that for described situation, is Liquid Relief Kit required or not?

A reference to a standard or code is preferred.
Thanks,

 

[shvet]

Not required. The cavity relief is related to liquid expansion caused by heating, not vapor condensation caused by cooling.
Make sure that liquid trapped inside the cavity can't be heated up, expand and overpressurize the valve body. This case is not relevant if the liquid in cavity has any vapor space.

 

[LittleInch]

That clause is intended for where you have liquid flow.

If you can get liquid propane 100% when you close the valve then the answer is yes.

Only you know what your process is and whether you could get 100% liquid propane.

Propane is quite bad in terms of liquid expansion so be careful.