Reduced flow when outlet valve of pump higher than 50% open

[Okui]

Need your guys expertise...

Had a water stripping pump. We had problem with water in our tank thus we tried to strip as much as possible. However, whenever the valve opening of the pump higher than 50%, the there will be reduced flow..trying to figure out why...

 

[BigInch]

Not much information to go on there Okui.

Possibly: the higher flow is drawing down suction pressure and entering cavitation range. Do you have any indication of cavitation?

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[SeanB]

I agree not much to go on. Are you measuring the flow rate? How does it compare to the rated flow of the pump? What is the pressure downstream of the valve? Perhaps your pump is limited by the head that it can produce, so even going to 100% on the valve won't give you any more flow. Without more details it's a crap shoot.

 

[BigInch]

impeller head limit probably would not reduce flow.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[fatgit]

Okui
I think Biginch has a point.
If you are able to find the pumping curves for the pump you are using you may find that you have insufficient head at the supply to keep up with the pumping delivery I.E. the water can't get through to the pump fast enough with the valve open beyond half way, the pressure falls away and you get less flow and maybe cavitation which will create pitting in your impeller and sound lousy during running Try to find out whay the Net positive suction head is meant to be (google this) calculate your net positive suction head and you may find that you need to either drop the pump/ raise the delivery tank or make the delivery pipework larger and take out any bends in the delivery line.

 

[IFRs]

You may be increasing the flow rate such that there is a vortex at the inlet of the pipe inside the tank.

 

[SeanB]

The point I was trying to make is the flow actually reducing, or is it not able to increase beyond a certain point? The problem description sucks so any answers at this point are just a guess.

 

[BigInch]

reduced flow is one of the few symptoms he did mention.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[rcooper]

My money is on a vortex at the pipe inlet, like what IFR said.

 

[BigInch]

Yes that certainly could be.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic (Note: Make that 99.99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Artisi]

Maybe we should all wait on the OP for additional info' - enough crystal-ball gazing so far.

 

[Okui]

the operation tech just told me through the phone and i yet to go and verify at site. will gather the necessary info. anywy thx for the kickstart idea on what would contribute to it..