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Psv Relief Rate To Avoid Pressure Surge


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#1 Anup87

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Posted 21 July 2014 - 06:51 AM

Dear All,

 

Please guide me on how to calculate the relief rate for relief device used to protect pipeline from pressure surge during the blocked outlet event.  We have to provide a relief device at the end of pump discharge where pump maximum shut off pressure does not exceed the pipeline design pressure.  However, per surge calculations done in AFT Fathom, shows that surge wave may exceed the design pressure and it can cause the fatigue or damage.  So, we have finalized to provide relief device at the end of line near block valve.  For this case first and foremost option I can think of is to provide relief device with pump capacity at relief.  However, it doesn't seems correct to me.  Please give your guidance and thoughts on how to calculate relief rate required in this case.

 

Thanks!

Anup.



#2 fallah

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Posted 21 July 2014 - 07:18 AM

Anup87,

 

At first, please specify if the surge source is pump shut down or discharge valve closing... Also a simple sketch may help to submit a better response...



#3 Lowflo

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Posted 22 July 2014 - 01:38 PM

Anup: For hydraulic surge you need to use a special device - one that's designed for that service. You'll find hydraulic surge valves on the market. Common spring loaded or pilot operated relief valves can'r protect from liquid surge because they don't open fast enough.



#4 Anup87

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Posted 31 July 2014 - 06:10 AM

Fallah and Lowflo, sorry for late response and thanks for inputs.

 

Fallah, surge is due to closing of valve while pump is still running.  

 

Lowflo, thank for the inputs.  Actually its client requirement for which I am just new in all terms.  Have never done surge analysis also. So just gathering information so that I can face the client.  Client is rigid upon giving relief device.  It will be helpful if you can provide more insight to this subject.



#5 fallah

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Posted 31 July 2014 - 07:05 AM

Anup87,

 

You failed to specify the type of the pump you are discussing about; even though seems the pump is centrifugal type. If so, it certainly has a minimum flow protection might be activated during discharge blocked outlet. Nevertheless, no need the relief drvice capacity to be equal to pump capacity and appears the required relief rate of such device equal to pump's minimum flow rate would be adequate...Due to pressure flactuation at relief device inlet during the surge, the type of the device should be modulating pilot operated which opens quick enough at the surge conditions...



#6 Rajan selvaraj

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Posted 29 January 2015 - 01:50 AM

please post surge relief valve calibration procedure or method 






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