Sizing Discharge pipe 1

[OliverSudden]

We have just had a new plant installed, and are having trouble with a pump. The pump should be capable of 20 tonee/hour, but is doing almost mothing. I think the discharge pipe work may be too small, and is therefore restricting the flow.

Discharge pipework is 1 1/4" with a run of about 15.0 metres. What sort of head will this generate? Is there any reason we can't increase the pipe diameter?

 

[katmar]

1 1/4" pipe does sound small for that duty. The head would be about 18 m (assuming you are pumping water) and the velocity would be close to 6 m/s.

But it may have been designed that way deliberately. If you make the discharge pipe larger to decrease the head and increase the flow you may need more power than the motor can deliver - this is called the "run off" condition. You should get hold of the pump curve and see where your operating points (current and desired) are relative to the Best Efficiency Point on the curve. The pump supplier should be able to advise you.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[pennpiper]

Is the "Check Valve" installed backwards?

 

[hydtools]

Is the pump running backwards? That would produce very little flow.

Ted

 

[maddocks]

Check your suction strainer - it may be plugged....and as hydtools said, I'd check rotation right away. Your pump may also be vapour locked...bleed the discharge to remove casing vapour.

 

[chief]

With 1.1/4 ins discharge you should be flowing 45 GPM if you are pumping water, which equates to approx 10 ton /hr at velocity 10fps with sch 40 pipe.

Offshore Engineering&Design