Flanged PSV versus threaded

[SrChemE]

I need to install a PSV in Nitrogen line. A different model relief valve was received (27EA34-120 is flanged) instead of 27EA34-M20, which is threaded.
Would it be okay to install a flanged PSV in nitrogen service?

 

[pennpiper]

What size piping are you talking about?

Sometimes its possible to do all the right things and still get bad results

 

[mk3223]

IMO, it's fine for the flanged PSV in the N2 system.
The question is why the "threaded" PSV allowed for the N2 system in your plant.

 

[zdas04]

My question is since flanged PSV have a different exhaust size than inlet size and threaded have the same, how are you going to adapt the piping?

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[SrChemE]

This will be a 1"X1.5" relief valve on a 0.5" nitrogen line.
Our piping spec allows thredded piping for 1.5" diameter pipe or smaller.

 

[pennpiper]

SrChemE,
You have answered your own question.
You say your piping specs call for piping 1-1/2" and smaller to be threaded, then you can use a threaded PSV.

Sometimes its possible to do all the right things and still get bad results

 

[SrChemE]

The pipe spec was just recently updated to include threaded smaller pipes, it was going through approval process. I was working off an old pipe spec and was wondering if there were any specific rules.
Thanks for your input.

 

[mk3223]

IMO, the thread piping should be limited to the Cat.D fluid only. The seal welded piping should be used for the Nitrogen.
Is the added threaded piping in the spec for the N2 specifically? Was the fitting designed for using in the certain process fluid?