How to Verify the Submersible Pump Speed During Factory Acceptance Test?

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Submersible pump assembles as a closed coupled design and is fully immersed in the water. Commonly, the shop pump curve gives the pump speed at a particular duty point.

How do we validate the submersible pump speed during factory test vs the guaranteed pump speed?

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8 Answers

  1. I agree. When a VSD is not used, the final performance of the coupled pumpset is all you need to measure. Please note that pump performance from a bulk manufacturing process will differ slightly (up or down) and performance will also deteriorate as the mechanical clearances wear. Therefore consider what is your actual requirement and how this can be achieved over time.

    If your question is to get a fair tender process and ensure the salespeople are not 'exaggerating the truth', then base penalties upon your most important requirement, as I have done previously with efficiency and whole life energy cost of operation the determining factor. 

  2. It's not really necessary to verify the pump speed.  You are testing an integrated pump and driver unit (pumpset), so the key performance parameters to verify are the head, flow and power consumption curves, which must be within factory-stated tolerances, assuming that your power supply is also within specified tolerances.

    On your table, I believe "motor data" just means reading that number off the pump curve, e.g. if you have a 50 Hz power supply, the pumpset will run at a nominal 1,450 rpm (or whatever speed is stated - this will just be the motor speed at the rated load) and it would be 20% faster for a 60 Hz power supply.  I think that "vibration data" refers to measuring vibration at the motor bearings and analysing the frequency - there will be a vibration at the vane passing frequency (for conventional vaned impellers, not vortex pumps), so the rotating frequency can be calculated by dividing this frequency by the number of impeller vanes.  However, as I said, it is not really important to know the pumpset speed because what it is guaranteed to deliver is the stated hydraulic and electrical performance for a given power supply.

    If you are using variable speed control (VSD/VVVF drives), test using 100% speed.  In any case, factory data for reduced speed operation or reduced impeller diameter is often simply calculated using pump affinity laws.

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    I've realized that I might have made an incorrect assumption:  I interpreted your comment about close-coupled design as referring to single stage submersible pumpsets with motors sharing the same shaft as the pump, as per submersible sewage pumps.  For multi-stage submersible borehole pumps, you are not necessarily purchasing an integrated pump and driver, so the motor design is not the pump manufacturer's, and it will also probably be almost impossible to derive motor speed from vibration data.  However, speed is again not critical to measure because correctly sized/rated motors of the same basic design (e.g. 2 pole or 4 pole) and efficiency will operate at similar speeds (certainly within the 5% tolerance typically quoted for flow performance data), and some pump manufacturers even simply denote the operating speed on the performance curves as either 50 Hz or 60 Hz.  

  3. It is not possible to measure the speed of the impeller once it is submerged in water. You can only check the desired output by fixing the flow meter & pressure gauge on the delivery line.  The values can be confirmed with the duty points given by the manufacturer

    Prof. Rajendrakumar V Saraf

  4. If we look at the attached table for submersible pump under RPM measurement column where it mentioned by motor or vibration whereas other type of pump using tachometer for RPM measurement. How exactly by motor or vibration measurement or  calculations to obtain the submersible pump RPM or speed can be done at plant testing facility. 

  5. I have a lots of submersible pump which be 0.75, 1.5, 3.75, 5.5, 7.5 kW and using in waste water treatment (heavy duty works). And I always fix them but after fixing they run smoothly only 3 months. you can test only coil, Flow, Pressure which be link with head and performance of the pump and leak in term of electric. Finally we buy the new pump is the best way and for the fixed pump we use for spare.

  6.  to measure the submersible pump speed, just in order to be sure that the pump running with the ​guaranteed speed you can measure the impeller speed from the suction side (this tip you can do it before the factory test and before you put the pump in the water) i did this test before in our lap to be sure that the pump rotating with its ​guaranteed speed.

  7. Submersible Motors coupled to pumps are squirrel cage type motors most likely 2 Poles with slip in the range of 2- 4% slip (running about 2900rpm).

    To accurately measure the slip of the motor you would require  an induction coil (about 1000 turns coil of suitable diameter of water proof  the motor inserted in that. The coil induces a pulse on every slip and that may be counted to calculate slip and actual speed may be ascertained.