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Relation between inlet and outlet piping

Relation between inlet and outlet piping

Relation between inlet and outlet piping

Good morning everyone!

When validating PSV sizes I normally tend to recommend that the outlet line has to be bigger than the inlet line, but haven't found the API recommendation, si am I asking if the outlet must be bigger than the inlet or not.

For example, if I have a 2J3 valve, could I install an inlet of 6" and an outlet of 4"? Or should I have than an outlet of minimum 6"?

Any response will help a lot or maybe the API says something about it but I haven't been able to find it.
Thank you,

RE: Relation between inlet and outlet piping

To my knowledge, no standard says the outlet piping must be bigger than the inlet piping.

Good Luck,

RE: Relation between inlet and outlet piping

Typically Inlet x Outlet Pressure Relief Valve sizes are established and governed by API STD 526.

They have larger outlet sizes to effect a pressure drop, thus lower rating class flanges are used on the outlet.

There are some smaller size nin-API STD 526 PRV's made with same inlet x outlet sizes, but these are limited to liquid service and lower pressures.

The golden rule is that any inlet and outlet piping should never be smaller than these sizes.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

RE: Relation between inlet and outlet piping

Thanks to both of you! I will stop recommending it then, just in case they ask me from where I took the guideline.

PSV huge,

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