8 replies to this topic

[PYG]

how to calculate relieving temperature in blocked discharge case for psv?

[Bobby Strain]

You must have all the process details. Heating, cooling, condensing, evaporating, compressing, expanding, phase, etc.

 

Bobby

[PYG]

i have the stream properties at normal operating conditions. i am not able to figure out how to calculate relieving temperature. i have the relieving pressure at blocked discharge conditions. 

[navneet2109]

Saturation temperature of fluid at relief pressure would be the relieving temperature. You can find out in perry's book and search for vapor pressure table. Or if you have any software like unisim, chemcad etc. 

[mattb]

as said by other members it depends from your application,

for mixtures in some cases you can solve a volume-pressure flash operation, see for example

http://prodesoftware...conditions.html

Edited by mattb, 26 April 2017 - 01:09 AM.

[Fakhri]

For conservative purpose, you can flash from operating pressure and temperature to relief pressure at constant vapor mass fraction. Or you can flash acrobatically from operating pressure and temperature to relief pressure.

[spchauhan12]

Yes, I do agree with  navneet2109.

You may take help from hysis. Just put Relieving pressure for your Inlet stream of PSV & then run & get the corresponding Relieving Pressure for your blocked discharge condition. You may also find out whether your fluid gets flashed in two phase from hysis. I have already done such type of activity in my previous project.

 

Regards,

 

SP

[spchauhan12]

Hi one small correction in above post.

 

Please consider " get the corresponding Relieving Temp." in place of " get the corresponding Relieving Pressure."

 

Regards,

 

SP

[serra]

PYG,

can you provide more information about the problem (see also Bobby Strain comments) ?

Take care about the numbers, for wide boiling mixtures (a common case)

there is a large difference between bubble point and dew point temperatures,

a large amount of liquid can evaporate before the PSV opens,

for vessels, the  Volume-Pressure flash suggested in post #5 is a good alternative

to more complex methods...