3 replies to this topic

[SyedAhmed]

Dear All

 

I have a question that during the design if I use the check valve (NRV) in relief header where different Pressure safety valve (PSV) reliefs lines are connecting so does the codes allow me to do so. I spend some time to find out in API 520 Part II & 521 but not very helpful in this regard. So if you guys have some idea or experience so please share.

 

Secondly what is the criteria of using spectacle blind at with the isolation valve at PSV discharge and inlet pipe?

 

Wait for your response!!!!

[fallah]

Hi,

 

You aren't allowed using spectacle blind along PSV inlet/discharge lines.

 

Also per the attached from a valid reference it's not possible using check valve in pressure relieving path such as flare header and sub headers.

Attached Files

•  Check valve in pressure relieving path.pdf   62.87KB   41 downloads

[SyedAhmed]

Thanks Fallah

 

Can you just tell me the attach reference that which pressure safety design practice is this so proper reference will be valid and helpful.

 

However as per your statement about not to use spectacle blind at the in/outlet line of PSV. The attach reference doesn't show that. Please need more clarification with reference. 

[fallah]

Hi,

 

It's from following book by Nicholas P.Cheremisinoff:

 

"Pressure Safety Design Practices for Refinery and Chemical Operations"

 

Indeed, when you are not allowed using check valve at the inlet/outlet of a PSV; needles and it's not logical saying you're not allowed using spectacle blind as well...!