27.02 What is fluid hammer and how is it avoided?

Fluid Hammer is a pressure wave within a piping system that can cause excessive vibration of the piping and other system components. Fluid hammer occurs when the fluid in a piping system is rapidly pressurized, most commonly from a pump starting or a valve closing, particularly when refilling generator day tanks.

The easiest way to avoid water hammer in fluid systems is through the control programming that (a) allows a pump to start only after a valve is day tank inlet valve is opened, and (b) allowing a day tank inlet valve (or the last open valve in a multi-day tank system) to close only after the pump has stopped.

An alternative is to slow the start and stop of pumps using VFD drives, and to use actuated valves rather than fast closing solenoids at tank inlets.

Other alternatives are (a) the use of hydraulic actuated valves to slow the pressure builup in piping systems, (b) the use of accumulators or bladder tanks to absorb and dissipate pressure waves.