Possible Cause

Remedy

Shaft misalignment.

Check and realign.

Worn coupling.

Replace and realign.

Worn pump/motor bearings

Replace bearings; lubricate.

Check and realign shafts.

Improper foundation or installation.

Check for proper grouting.

Check possible shifting because of piping expansion/contraction.

Realign shafts.

Pipe vibration and/or strain.

Inspect, alter or add hangers and expansion provision to eliminate strain on pump(s).

Water velocity.

Check pump performance against specified and reduce impeller diameter as required.

Check for excessive throttling by balance valves or control valves.

Pump operating close to or beyond performance curve.

Check actual pump performance against specified and reduce impeller diameter.

Entrained air or low suction pressure.

Check expansion tank connection.

Check the line size if applicable.

Checks pump ability against requirements.

Check for entraining air into suction line.