Dead Head Suction Pressure 1

[SpetsnazCyclist]

All,

My question is based on the case where the flow of a centrifugal pump is blocked at the output and you end up with a no-flow situation. I would assume that since there is no flow, the suction pressure of the pump would be equal to the upstream pressure, and the discharge pressure is equal to the suction + head. Is this the case?

Best regards,

Andrew

 

[pmover]

Should be . . .

-pmover

 

[micalbrch]

Not really. At zero flow your centrifugal pump has its max. head. If the suction pressure was the same as the discharge presse, the differential pressure would be zero. Zero flow and zero head would mean no power consumption. But that is not the case.

Just assume you have a multistage centrifugal pump for higher pressure and you close the discharge line. Will your suction side pipework with valves then see the high discharge pressure?

 

[rmw]

Since the head is the highest at shut off, the differential pressure across the wear (or seal) rings is the highest and the recirculation is the highest. This will raise the suction pressure somewhat from what it normally is, but not nearly to discharge pressure. As the pressure of the suction rises, the flow would try to reverse and flow back into the suction piping. If it ever reached discharge pressure, you would have full flow in the reverse direction - not going to happen.

rmw

 

[123engr]

I agreed with rmw.
The suction pressure will not be equivalent as the discharge pressure. From the pump safety perspective, the pump would trip off when it exceeds it maximum pressure switch set point. Therefore, the envisaged scenario would not occur.

 

[SpetsnazCyclist]

All,

Thank you for the responses! Do any of you know a good text where I can read up on the physics behind this potential situation? For reference, I am trying to configure a simulation that is able to model these conditions.

 

[Pumpsonly]

With the exception of pmover, I think the others has miss read the OP's question.
"the suction pressure of the pump would be equal to the upstream pressure, and the discharge pressure is equal to the suction + head. Is this the case?"

He did not said the discharge pressure is equal to the discharge pressure.

 

[Pumpsonly]

correction
He did not say the suction pressure is equal to the discharge pressure.