Increase flow and pressure??

[kmg1983]

How can you increase flow and discharge pressure on a multi-stage vertical pump while holding the suction pressure constant?

We have this exact scenario happening and the flow is measured downstream of the check valve and the pressure is measure upstream of the check valve? Any input is appreciated. Thanks

 

[BRIS]

I understand that you are recording an increase in flow and pressure without any change in suction pressure.

(You are not attempting to increase flow and pressure which is what your question appears to ask)

Air binding is a possibility - air in the riser pipe will restrict flow - as the air is entrained and transported downstream you will see an increase in discharge pressure downstream of the air pocket and a corresponding increase in flow.

Solutions are an air valve at the top of the riser and a foot valve on the pump:

 

[kmg1983]

That is correct...we are recording a measurable increase in flow and corresponding increase in pressure on a vertical pump having crude oil as the pumping fluid. I must also add, the pump shutdown on high temperature alarm at the top motor bearing??

 

[djack77494]

I have never seen a pump curve that would result in such performance. I have always seen the pressure go down as the flow went up, though sometimes near/below minimum flow the pump curve does hit a maximum. In any case, if it's real, then you are probably in a bad area of the curve.

 

[dickon17]

Is dissolved gas in the crude oil vaporizing in the pump?

 

[25362]

On drooping pump characteristic curves see:

thread407-108195
thread407-108876
thread407-101056

 

[HEC]

If suction pressure is remaining constant, look to the pump inlet configuration. I presume that you have a flooded suction. Further the suction line and flow losses are possibly less than the total head on the pump suction, hence you will not see any drop in suction pressure. You would expect a drop in suction pressure if there were significant losses in suction line and/or the source tank level droped significantly.

Mark Hutton

 

[zdas04]

What is your measurement technology? I've seen turbine meters significantly increase their reading (with a constant stroke speed on a plunger pump) when gas was entrained in the liquid. In this case the gas makes the liquid "fluffier" and it spins the turbine faster. What I'm saying is that it could easily be that your mass flow rate is decreasing with an increasing volume flow rate (i.e. lower density). Pressure increases could easily be multiphase flow downstream.

In short it is pretty rare for something to go "wrong" that increases the performance of a pump.

David