Water hammer is the pressure surge that races through a pipe when the flow of liquid is stopped or started too quickly. The moving column of liquid has momentum, and when a valve slams shut or a pump trips, that momentum converts into a sharp spike of pressure that can burst pipes, crack fittings and wreck pumps and check valves.
Liquid is nearly incompressible, so a column of it moving down a pipe behaves like a heavy, fast train with no brakes. Stop it suddenly and its kinetic energy has nowhere to go but into pressure. The size of the surge depends on how fast the flow is stopped and how fast the pressure wave travels: the Joukowsky relationship shows the peak pressure rise equals the fluid density times the speed of the pressure wave times the change in velocity. A rapid stop of a fast flow produces a very large spike.
The core fix is to slow the change in velocity. Close valves slowly, use actuated valves with controlled closing times, and fit correctly sized, fast-acting or spring-assisted check valves. On the pump side, controlled start and stop with a soft starter or VFD ramps the flow instead of switching it. Surge protection such as air chambers, accumulators and surge tanks gives the pressure wave somewhere to go.
The same fast transients that cause water hammer can also drop suction pressure enough to trigger cavitation, and repeated surges fatigue joints, supports and pump internals. Running a system smoothly, near the pump's efficient point and with adequate NPSH, keeps both problems away.
Pressure spikes and the vibration they cause are exactly what a monitoring platform can trend. Repeated surges show up as pressure and vibration events, and flagging them turns a slow-fatigue failure into planned work. Fabrico reads that signal and routes the job. Book a Fabrico demo to see it.
A sudden change in flow velocity: a valve closing too quickly, a pump tripping, or a check valve slamming as flow reverses. The liquid's momentum converts into a pressure surge.
Slow the velocity change: close valves slowly, use controlled pump start and stop, fit fast-acting check valves, and add surge protection such as air chambers or surge tanks.
Yes. The pressure surge and reverse flow can slam check valves, crack casings and fittings, and the repeated shock fatigues pump internals and pipe supports.
They are different, but the same fast transients that cause water hammer can drop suction pressure and trigger cavitation, so a smoothly run system avoids both.
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