Pump Testing

Hi rabat

"Do we have to test the two together?"

The pump curve of the supplier is mostly sufficient enough to select the pump for duty without testing.

The motor RPM is also are rather on target.

It is always good practice to design a pumping system with some reserve. Allow for wear which will reduce capacity. Allow for increased friction caused by sediment deposit in the pipes. etc.

Note that allowing for too much reserve may also be counter productive. (a centrifugal working against a too low head will pump more water and consume more power)

"Note that allowing for too much reserve may also be counter productive."

Yes, then you have to throttle the pump back to control flow. If you throttle the pump back too much the pump will overheat and possibly fail.

Pump can be tested using a shop motor, so you can verify the pump performance before shipping to site. Motor can be tested separately - no problem.

This is common practice for most cases.

I would never buy a process pump without testing.

Nothing more to add.

We as a purchaser for different pumps and motors rarely get them two together (some cases we do get them as a single skid mounted unit but they are rare) Our procurement is on the shop test at rated RPM and that also with not rated oil. These are corrected for viscosity as per the standard. And you definitely do not expect pumps like Boiler feed, Cooling water etc to be tested with the actual motor as an unit.

Hi rabat

The Prof is right - If this is not the non critical pump used to transfer water from one chanel to the next of your previous post you should test it.

If you are the supplier you should consider the requirements of your clients.

This testing is called String Test and it all depends upon the client or customer what has been specified.The string test does cost loads of money.Recently we had purchased 4 Nos LV motors from Finland and Pumps from UK,but due to customer requirement we had to ship motors and LV Drives to UK in order to test 1 set of Pump and Motor.The pump manufacturer do have similation lake bays consisting of water.

I deal with this a lot and I have a few problems with testing anything other than an off the shelf pump and motor unit without the pair truly mated.

Inherent vibration, friction, true compatibility tweaking before a FAT, possible inefficiencies in the motor and/or pump require, by all of my interpretations the mating of the 2 field units before the fat and shipping.

I have seen too many FATs pass with a shop motor and then have to have the units reworked in the field.

Even mounts were wrong because of the concept of just in time delivery.

Mated units should be specified.

I agree, especially if its a critical application.

This depends upon the availbaility of calbrated motor and the rating.In normal cases it is in order to test the pump with calibrated motor and and motor separately tested in motor factory and assemble at site.However when it comes to larger sizes where a pump factory may not have that kind of motor or where efficiecies at duty point are commited and guranteed with penalties for drop in efficiency as per contract then the motor is tested in motor factory and efficiency apart from the normal 25,50,75 and 100% load duty point efficiency is determined.If there are more pump sets of similar capacity one tested motor is sent to pump manufacturers works where using it all pumps are tested .What I have never understood is the pump manufacturer ushually supplies the motor as a package when a customer directly order the motor and save money.but that's another subject.

You DO understand it! It's called sales! Did you ever hear the American (I think) expression "everything is in the packaging"?

It is good engineering practice to have a single point of responsibility for a machine train. In other words the supplier of the driven equipment should always be responsible for the driver. In this way there is reduced risk of a mismatch.

I have seen too much time, effort and money wasted trying to save a few bucks by buying the motor separately.

If only driven equipment manufacturer should give the package why in DG Sets its the otherway?Engine manufacturer gives the DG set not the Generator manufacturer