Safety first. Isolate the motor and close and drain the pump before you open it. Hot product and cleaning chemicals can remain in the casing.
Symptoms
- Rattling or crackling noise from the pump.
- Flow or pressure lower than normal, or unstable.
- Pitting on the impeller or casing.
- Shaft seal failing more often than before.
Likely causes
- Low level or restricted suction. A low tank level, a partly closed valve, a blocked filter or a long, narrow suction line reduces the pressure at the pump inlet.
- Hot or volatile liquid. Liquid close to its boiling point turns to vapour at a small pressure drop.
- Air entering. A leaking suction joint, a vortex in the tank or air from mixing gives similar noise and low flow.
- Flow outside the pump's range. Running far to the right of the pump curve, at high flow, raises the pump's suction demand.
- Viscosity. A thicker product than the pump was selected for increases suction losses.
What to check, in order
- Check tank level, suction valves and filters while the noise is present.
- Compare product temperature and viscosity with normal production.
- Look for a vortex at the tank outlet and for leaking suction joints.
- Check the pump's operating point against its curve in your service documentation.
- Check that the motor speed or frequency drive setting has not changed.
When to call a TPS engineer
Call a TPS engineer if the noise continues with correct suction conditions, if you need a new duty point, or if the impeller shows pitting.
Ask LiveAccess
Ask with the pump nameplate photo, product temperature and the flow you expect. In the app you can also find a liquid processing expert in the Expert Network and chat or call them.
This guide gives general checks. Settings, limits and procedures differ between machines: always use the values in your service documentation and your site procedures.
