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Pump Shut Off Pressure At Pump Suction Block Valve

pump shut off pressure suction block valve

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#1 S J

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Posted 26 September 2016 - 04:31 AM

Dear Sirs,

 

I'm process engineer.

I would like to ask about pump shut off pressure at pump suction block valve.

 

In case of installing one running pump and one standby pump,

because pump discharge lines are connected each other, pump discharge pressure could be transferred to suction block valve of standby pump. Refer to case A in attahced file.

 

In case of installing only one running pump,

I'm not sure if pump shut off pressure should be applied to suction block valve. Please refer to case B in attached drawing.

Is it possible that shut off pressure could be transferred to all blocked section ?

Shut off pressure means maximum pressure in restriced section when flow is blocked.

I'm wondering whether all blocked section will have maximum pressure during pump shut off running.

 

Please share any experience regarding application of pump shut off pressure to pump suction block valve.

Attached Files


Edited by S J, 26 September 2016 - 04:36 AM.


#2 breizh

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Posted 26 September 2016 - 04:43 AM

S.J,

You may consider 1 common recirculation line after the block valves and  to add check valves  to your sketches.

 

Breizh


Edited by breizh, 26 September 2016 - 05:37 AM.


#3 fallah

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Posted 26 September 2016 - 04:49 AM


 

S J,

 

In case A the suction block valve of the stand by pump which is normally closed, can be subjected to pump shut off pressure; hence the design pressure of the suction lines of parallel pumps should be same as the design pressure of the relevant common discharge line.

 

In case B the suction block valve of the running single pump which is normally open cannot be subject to pump shut off pressure.



#4 S J

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Posted 26 September 2016 - 07:08 PM

breizh

You are correct. Installing common recycle line is general practice and check valve is required at each pump discharge.

In my current project, client prefers installing individual recycle line for each pump. That's all.

To ask about the range of shut off pressure application , I simplified the drawing.

 

fallah

For determining design pressure, considering each block valve closing case is required.

If pump suction and discharge block valves are closed and pump runs in case B, should we apply pump shut off pressure to pump suction block valve ?



#5 fallah

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Posted 27 September 2016 - 01:30 AM

 

fallah

 

If pump suction and discharge block valves are closed and pump runs in case B, should we apply pump shut off pressure to pump suction block valve ?

 

S.J,

 

Yes, we should apply; but I believe simultaneous inadvertent closing of both suction and discharge block valves of a running pump has to be considered as a very rare situation hence a double jeopardy...!
 



#6 S J

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Posted 27 September 2016 - 04:49 AM

fallah
 
Thank you for your response.

 

In my head, I can imagine that shutoff force is transferred to suction and discharge when pump suction and discharge valves are closed.

Could we explain this with technical or scientific terms ?



#7 fallah

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Posted 27 September 2016 - 05:24 AM   Best Answer

 

In my head, I can imagine that shutoff force is transferred to suction and discharge when pump suction and discharge valves are closed.

Could we explain this with technical or scientific terms ?

 

S.J,

 

If mentioned situation actually be happened; at the first moments suction side might be subject to a relative vacuum but then due to temperature increment and fluid recirculation the suction side will be subject to the same pressure of the discharge side and finally due to high temperature and pressure (fluid vaporization) pump seal will be damaged and leaks till total seal/pump failure...



#8 S J

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Posted 04 October 2016 - 12:18 AM

Thank you, fallah






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