Hi Guys,
I am checking a piping isometric from our detailed designer. The line is a PSV discharge to atmosphere. there are 2 PSVs; one is spare. The discharge line has a block valve (one locked open and one is spare) and it was placed in the vertical. The line is going up the structure which means the valve is a low point and is a pocket. My question is, is this kind of configuration allowed or good practice? I am working on a modular unit and space is limited. I believe this is the reason why the designer kept it at the vertical.

As always, thank you for sharing your knowledge.

Adam