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Monday, February 7, 2011

Water Hammer On Centrifugal Pump

Pumping problem that often facing is water hammer, and issue of wrong pump and pipe designer that sometime can’t be handle by new operators. Water hammer often happened on a big centrifugal pump when wrong operate.

How it can happen?
Water hammer practically cannot detect if the increasing pressure accelerated or retarded pump by pump condition and valve changes can be normalize automatically. Usually this pressure changes just small, the rate of changes also gradual. If the pressure changes may ten times bar, and the forces on pump support can many tones till exceeding the support limitation, the pipe can be rupture or damage. Other case of lower level water hammer can cause chronic deterioration, and leading to the gasket leaks over time.

Water hammer can happen if the valve open or closed to fast, this action can cause pressure changes too quickly. The big pressure changes can cause the force to the pipe or to the pipe support out of balance. The force like this can shift the pipe even move from the pipe support.

How to avoid water hammer?
Water hammer can be avoided by many kind depend on each situation’s and circumstance. The following may be some conclusion as your consideration to apply.

  • Eliminating of problem source like from vibrating pressure of relief valve, fast emergency shutdown valve closure, change of the automatic close time like on the butterfly valve and many others.
  • Reduce the pumping velocity, this can be modified on the pump like to install expansion pipe to reduce pressure.
  • Install surge tanks
  • Use surge alleviators that commonly just fit for positive displacement pump.
  • Use air inlet valves.
  • Create a by pass pipe that passing the valve when closed.