6 replies to this topic

[nmh]

Dear Experts,

 

I have a question regarding relief valve calculation. My relief valve is set at 200 barg for hydrogen service and relief valve outlet pressure is 1.5 bara.  I want to calculate the flow through the valve, for flow calculations I would like to know which pressure (for corresponding hydrogen density) should I consider to calculate the flow in case of relief scenario.

 

 

Many thanks.

 

nmh  

[paulhorth]

This question shows a depth of ignorance which is rather scary.

Please can you first tell us what equation you are intending to use to calculate your relief valve flowrate?

 But first I would advise that you make some effort to read up about the subject of compressible flow and critical flow.

 

Paul

[satendra.deshmukh]

it depends on which scenario you are performing on that relief device..

[latexman]

In the sizing equations I am familiar with, the upstream density (i.e. upstream pressure) is used, however the flow is also dependent on the pressure drop (i.e. upstream pressure - nozzle exit pressure), so you must consider both upstream and downstream pressure to determine the type of flow (non-compressible, compressible, sonic, etc.) and the rate of flow.

[nmh]

Latexman,

 

Thank you for your reply.

 

 

Regards,

nmh

[breizh]

nmh .

It may be good for you to read these documents .

Hope this helps you out .

Breizh

Edited by breizh, 16 March 2013 - 02:38 AM.

[fallah]

nmh,

You are faced with a critical flow, then you should just consider 220 barg (for fire case 1.21*220 barg) as upstream relieving pressure to calculate the flow through the PSV...