Pressure Relief Valve Sizing

[ruwl]

I am trying to size some PSV's that have properties (hydrocarbons) with MW < 40 and Relief Pressure above 2000 psig. The API curve has a minimum of MW = 40 and a max pressure at 1000 psig.

For Fire case, how do I obtain the Latent Heat of Vaporization and Relief Temperature at the conditions mentioned above?

Can I be conservative and use Latent Heat of 50 btu/# anf relief temperature = (oper. temp./op. press.) x relief pressure?

I would appreciate any suggestion. Thanks.

 

[Latexman]

You may want to take this to the Safety Relief Valve engineering forum.

Good luck,
Latexman

 

[MortenA]

If you really want to know then you could use simulation software - thats what i usually do.

Best regards

Morten

 

[ruwl]

Latexman,

Thanks. I started another thread per your suggestion.

MortenA,

Thanks, but usually for the basic design package, the simulated process package is done for normal unit operation and the relieving conditions are not part of it.

 

[MortenA]

No but:

You make a copy of the inlet stream and set the P at the RP and the vapour fraction to 0 (at something similar this is how its done in e.g. hysys).

Then HYSYS will calculate the flash temp.

You then run the stream through a HX with a fairly low duty (at leat compared to the vol. stream in the dummy stream. Downstream the HX the stream should have a low vapour frac e.g. 0.01-0.001. If you want to know latent heat by weight then all you have to is that the duty of the HX e.g kJ/sec vapour mass stream in e.g. kg/sec and divide these values and you get latent heat in kJ/kg

Best regards

Morten