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Blocked Discharge Case Psv Relief Rate

psv relief

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#1 erwinfs

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Posted 19 April 2018 - 11:16 PM

Dear All,

 

I want to size a PSV based on blocked discharge case. My protected equipment has 120 MMSCFD as maximum expected flowrate. The fluid is natural gas.

 

If I want to size this  PSV, should I set 120 MMSCFD as the relieving rate? Can I get reduced relieving rate?

 

Because API 521 state the following:

 

"Consideration can be given to the reduction of the relief rate as the result of the relieving pressure being above operating pressure."

 

And if so, how do I calculate the reduced relieving rate?



#2 Bobby Strain

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Posted 19 April 2018 - 11:26 PM

 

When you look here for answers to questions such as this, that is not a good thing. You should seek advice within your organization for such situations.

 

Bobby



#3 fallah

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Posted 20 April 2018 - 12:18 AM

Dear All,

 

I want to size a PSV based on blocked discharge case. My protected equipment has 120 MMSCFD as maximum expected flowrate. The fluid is natural gas.

 

If I want to size this  PSV, should I set 120 MMSCFD as the relieving rate? Can I get reduced relieving rate?

 

Because API 521 state the following:

 

"Consideration can be given to the reduction of the relief rate as the result of the relieving pressure being above operating pressure."

 

And if so, how do I calculate the reduced relieving rate?

 

erwinfs,

 

If you apply mass flow rate you would have no concern about the pressure variation...



#4 latexman

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Posted 20 April 2018 - 08:11 AM

It is common for compressor manufacturers to give flow capacity at several delivery pressures.



#5 Saml

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Posted 22 April 2018 - 10:14 PM

You should consider the flow rate at 110% of MAWP or 116% MAWP if multiple valves are used.

 

i.e. if your equipment is downstream a centrifugal compressor you can expect a reduction in the relieving rate when the discharge pressure is higher. The compressor will not deliver as much flow at 110% pressure that it does at normal operating pressure.



#6 erwinfs

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Posted 24 April 2018 - 01:07 AM

Thanks All, for the answers  :)






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