How do I determine relief temperatures in PSV calculations?

[ruwl]

Is there a general rule to determine what is the relief temperature for blocked outlet, thermal expansion, loss of liquid seal, thermal expansion at suction of pump, pump discharge blocked in, etc.?

Is it safe to use Relief temperature = (oper. temp./op. press.) x relief pressure for these cases.

Thanks!

 

[MortenA]

I would normally in all cases but fire assume that the temperature was equal tro the normal operating temperature.

Best regards

Morten

 

[ruwl]

MortenA,

Could you tell me more about your exception with Fire Case?

Thanks

 

[MortenA]

well in the fire case you calculate the temperature where the vapour pressure of the liquid is the same as the SP +21% - thats your relief temperature.

The required valve capacity is then determined as described in API 521 and required valve size determined using API 520.

Best regards

Morten