API 610 centrifugal pumps

[richissa]

Hi everyone,

Existing centrifugal pump is rated at 800 gpm.

The problem is that this pump have to go long distances to reach the tank and the measured flow rate is measured to be 25 - 400 gpm due to frictional losses in the fittings.

No datasheets or pump curve available - thus the question is what kind of calculations required to verify the flow?

Thanks,

 

[LittleInch]

If you know the manufacturer and pump type you should be able to find a pump curve.

If you can't set up a test rig yourself and increase flow through the pump by sending some back to the inlet or inlet tank.

I hope you meant 250 to 400 gpm. At 25gpm for an 800 rated unit you wouldn't have much of a pump left...

You need to calculate your system curve - all frictional losses and head losses /gains versus flowrate.

Many more details required to make any more sense of your issue.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[richissa]

Thanks LittleInch for the quick reply! Can you advise the difference between the pump curve and the system curve?

 

[LittleInch]

Richard, As drawn in the sketch with Q and H on the other axes, the system curve is your growing resistance with flow. If the end point is higher than the start point then at 0 flow you will always need some head to get any flow. After that it is basically a partabolic curve as friction increases proportional to velocity squared.

Pump curve come from the pump vendor and is normally a downward curve from zero flow with a fairly long flat bit. Where the two intersect is your flow rate achievable for your system and pump combined.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[LittleInch]

Where did the sketch go?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Artisi]

LittleInch, the curve has returned just like the Elusive Pimpernel only this time the H,Q are notated correctly.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[TD2K]

Pump curve and system curve

http://www.engineeringtoolbox.com/pump-system-curves-d_635.html