how to calculate the reliefing capacity

[lomli]

hi,

Please I have to design a pressure reliefing system for a natural gas metering station, and a segment pf pipeline, API standard(521,520)give a formula in which the reliefing capacity is given as a known data but I don't now how i can estimate this value (the quantity of NG to be vented in order to establish the pressure).

 

[MortenA]

?

 

[ChEMatt]

What's the maximum flow going into the station?

If it were me, I'd determine what the max flow is going into the station, and use that as the capacity for the PSV. The pressure rating of the pipeline (and therefore the metering station, assumed) will dictate the set pressure of the PSV.

Onwards,

Matt

 

[lomli]

thank you matt
but I think if all the flowrate will be vented to atm the plant upstream (our costumer)will shuttdown every time the pressure increase in the station, the reliefing capacity is to evacuate just a defined quantity on NG to reach the normal operating pressure.

what do you say?

 

[MortenA]

This is confusing - you mention API 520 and thats pressure relief. But normally its for PSV's (and bursting discs). A PSV does not blow down the system - only prevents pressure from getting too high.

My initial ? was due to me not getting a vauge hint of what you are saying. That may, however, due to my poor English.

Maybe you should try to explain your problem without assuming that we know anyting about your system?

Best regards

Morten