Hydraulic Testing of Pumps

Your RPM could have been slow- check that!

The impeller may have been skimmed. size reduced to obtain a specific lower duty.

inquire at the supplier!

I have also seen incorrect pedestal and pumps assembled together.

Long ago the quality control was lacking and a 10% deviation was possible.

check with the supplier.

Your measuring equipment may be faulty.

Or a air leak on the suction side.

The pressure on the curves represent the total. Including suction height an friction and delivery head.

Are the gauges installed at the correct location?

Also check temperature and type of fluid. Or anything not to specks of the manufacturer.

thanks for answering me but could you tell me the effect of the size of the impeller on the performance of the pump

There is a 1,2,3 relationship. Pump suppliers usually provides curves showing the effect of reduced impellers.

It has been some time ago that I used it and I seem to have forgotten the unthinkable.

Other commenter's please correct me if I am wrong.

For skimming the impeller slightly the parameters will change relative to the reduced diameter according to the following relationship.

Fact = new diam / old diam

flow = old flow x fact

Head = old head * square of fact.

Power = old power * cube of factor

You could check out API 610

thanks for answering but could you please tell me what is API 610

Time to Google it!

If you need Api 610, just let me know. I have it in pdf format.

Best regards,

Abel

hey thank you ,

please send me the pdf

Hello Heba

• May be the pump under hydraulic testing is out of specifications.

• API 610 is an American Petroleum Institute standard for Centrifugal Pumps for Petroleum, Heavy Duty Chemical, and Gas Industry Services.

API 610 reaches 194 pages, and I think all pump specialists must have a copy of that standard, and I can help you.

What sort of pump?

the type of our pumps centrifugal pumps and seweage pumps

Also check the clearance between the impeller & efficiency rings - worn efficiency rings will affect pump performance.

Centrifugal pumps do not pump at "desired head and discharge of the best efficiency", they pump at the intersection of the pump curve and the system curve. What you need to check is whether the pump is running on the curve by plotting recorded differential head against flow on the original curve. To confirm that the pump is performing correctly also calculate the power from the amperage of the motor during the test. Once you know where it is running on the curve at various operating points it should become clearer what your problems are.

(Flow varies as the diameter, head varies as the diameter squared and power as the diameter cubed -- approximately.)

Quite.

Is this an old pump? If so then check the wear plate/impeller clearance. I had one pump ( made by Desmi) which had been run dry, heated up and impeller touched the wear plate. When the pump had cooled off and properly primed the result was a reduction of about 40% in quantity to the same head. Couple of shims is all it took to fix but if it is an old pump then you don't know what has been done to it before you got it so check out the easy things first.

Air leaking into the suction side is something I've seen too and this can give reduced pumping.

On one pump the non return valve on the suction side jammed only partly open.

What about the NPSHa. I take it you are giving the pump a chance to do it's job properly and not asking the impossible.

Don't want to insult your intellegence but if the pump uses a 3 phase motor then I hope you have checked the motor is spinning the right way.

I am late in this forum but, first thing I check in the pulp mills is spin direction of the pump, as above friend said.

2nd. Work with the curves provided by the manufacturer and take measures of the motor load.

Those 2 steps can resolve or at least gikve clear indication of the source of the problem most of the times.

3rd. Pressure drops of the line. Check the piping it has been done according design, and no modification it has been added after the calculations for pump and motor.

Best regards,

Abel

....is spin direction of the pump....

Of course! It's running sdrawkcab!

Been there. Done it. Secondhand T-shirt available on eBay.

Dear heba

where did you test the pump was it in a lab. or in a project site and what kind of instrumentation you used to have that results,also pump type ,please explan is Q,H and effeciency those which was stated on pump label or you have it's charecterstik curves ,name of the company that manufactured the pump, I hope that we can help you to solve this problem.

khaldoon kareem selman

consultant engineer

stockholm,Sweden