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Relief valve for Liquid Nitrogen
The standard for Relief valve sizing for liquid nitrogen service

Hi All,

I need a relief valve in my liquid nitrogen 3" pipe line, process conditions are -175 degC, Set pressure 8.4 barg, Blocked Discharge case.

The relief valve is venting to atmosphere at safe distance. My process engineer has given me his data sheet where the inlet side is showing as liquid and outlet side he has given me only gas flow.
(I dont believe him :-))

I need to know the following:
1. Is the relief flow will be two phased?

2. If it is two phased flow, I believe I will not get an ASME capacity certified relief valve?

3. By the way, is there any other standard for sizing such application other than API 520?

2. My piping engineer is not specific about end connection, what should be the preffered end connection for relief valve for such application?

Please help me out.