5 replies to this topic

[J_Leo]

Hello there,

 

Suppose the upstream pressure remains the same, the control valve down stream is blocked (for example, a block valve is closed). What will be the control valve downstream pressure? Will it keep at the set pressure or rise to the same as upstream?

 

I talked to two instrument engineers and they have different answers.

 

Thank you.

 

Regards,

Leo

[fallah]

 

Suppose the upstream pressure remains the same, the control valve down stream is blocked (for example, a block valve is closed). What will be the control valve downstream pressure? Will it keep at the set pressure or rise to the same as upstream?

 

 

Leo,

 

Appears it's a pressure control valve (PCV) is applied to keep its downstream pressure at the set value...

 

Then, following to PCV downstream blockage, at first the PCV will go to be completely closed to keep downstream at set pressure but finally after a while it will rise to the same pressure as upstream due to valve leakage...

[J_Leo]

Fallah,

 

Thank you very much for the explanation. It sound very reasonable to me.

 

Leo

[Bobby Strain]

And there are several more (different) reasonable answers. Which would make both of your instrument engineers correct. There is insufficient information to be very specific.

 

Bobby

[S.AHMAD]

In agreement with Bobby that you have not provided sufficient and clear information. However, if the CV ia a flow control valve, under this scenario, the control valve shall be fully open and hence the pressure immediately will be the shut-off pressure of the pump down to the upstream of the closed valve. The pressure downstream of the closed valve shall be the system downstream pressure plus elevation head. Under the scenario that the control valve is shut then the downstream pressure shall be the system pressure only the pressure upstream the CV is subjected to shut-off pressure of the pump.

 

It is more clearer if you attached the sketch of the system.

 

Hope this brief explanation is clear enough.

 

s.ahmad

[J_Leo]

Bobby and Ahmad,

 

Thank you for your responses. Please see the sketches I prepared.

 

For (1), assume all outlets are blocked.

 

For (2), the two angle valves run in parallel and split the flow during normal operation. Does each one needs to be sized to handle the total capacity in case one fails?

 

 

Attached Files

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