PD pump speed

[dbday]

Hi,

For a fixed speed plunger pump operating at say 300rpm will the pump actually operate at 300 rpm exactly, or will there be some small minor variation in the speed due to variations in the motor, drive/gear train etc and if such variations exist, will they get worse over time (I assume they will not get better, but perhaps they do).

I am not aksing about variations in speed that may be caused by process variation as I recognise that changes in the suction and discharge conditions may cause a variation in the speed of the pump.

This is more of a question of experience (which I don't have) and about what to think if I look at the speed of the pump and it is not 300rpm, I might see 302rpm, and this might be considered OK (I dont know), whereas if I see say 305rpm then perhaps I should get concerned.

I realise that there are other indicators of problems with pumps, but I am not asking about those.

Thanks for any input

 

[micalbrch]

The speed might be indicated in the documents and on the nameplate with 300 rpm althoug it is 299 or 302 due to the availability or gear ratios, v-belt ratios and because of the motor speed. Some manufacturers round the speed up or down to the next common value.

Apart from that the speed can indeed vary after xxxx operating hours. A reason can be slipping v-belts (if the pump has any). Also wear in the gear or motor slip can be a reason but all that is negliable and you should hear it, espacially v-belt slipping.

A change in the suction and discharge conditions cannot change the speed of a plunger pump unless there is a sensor and a control unit which increases or decreases the speed in dependence upon any parameter.