Pump Trip

[JamalS]

This a question about a water system. There a centrifugal pump to pump water 20 km in 24 inch pipeline. Does the cavity developed d/s of a pump (after a pump trips) travel along the pipeline to other end? is this a real phenomenon?

 

[LittleInch]

When you suddenly stop a pipeline you can, under certain circumstances get very low pressure at the pump end. This can either vapourise the liquid, create a vacuum or draw air into the pipeline through seals which are designed to hold pressure in.

It is difficult to see how this small bubble would then travel along a20 km pipeline to the far end, but not impossible.

A bit more of a description, profile, flow velocity operating experience etc would help....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

The magnitude of the water hammer and the time duration of the transient condition depends on the flow-rate velocity, pipeline material and the system boundary conditions such as tanks, pumps, air valves, control valves, and changes in pipeline diameter. The pressure wave travels down the pipe at the speed of sound in the liquid. If the liquid is water, rigid pipe and ambient temperature, the wave velocity is 4,720 ft/sec.

The water hammer effects diminish over the distance. The attached paper shows that the water hammer traveled over 6 miles.

 

[georgeverghese]

If you have water vapor bubbles forming in the pipeline on pump stop, then the end of this pipeline is most likely at a much lower elevation relative to the source. These bubbles collapse and recondense back into liquid water some where along the pipeline on pump restart as flow and line pressure build up. This can cause water hammer - dont know how this particular kind of hammer effect is eliminated though.