Centrifugal Pump Troubleshooting Guide

Zero Flow after   Startup

Air in Pump or Suction   Pipework

Ensure Pump and   Pipework are Completely Filled with Liquid. Pump can not prime with air in   suction line.

Suction Lift Too High

Check Inlet for   obstruction. If there is not an obstruction calculate friction losses. If   static lift is too high the liquid in the suction tank must be raised or pump   lowered

Insufficient   Manometric Head

Actual head with   friction losses is higher than pump design. Calculate head and friction   losses in discharge. Check all valves are open. To correct increase pipe   diameter, or increase impeller diameter, motor power or pump.

Operation is Reversed

Check motor direction   of rotation is in the direction of arrow on pump casing

Speed Incorrect

Check supply voltage and   frequency. Motor may also have open phase

Impeller, strainer or   check valve clogged

Clean impeller, valve   and strainer

Flow Decreases or None at All

Air ingress through   shaft seal, suction piping, suction port. Pump lifts liquid with air.

Check suction pipework   for leaks, including all joints and fittings. Check shaft seal and if   necessary, increase pressure of sealing liquid. Check depth of suction   pipework or valve in liquid and deepen if required. Check inlet tank for vortexing.

Air pocket in suction   pipe

Check angle of suction   line and ensure there is no possibility for an air pocket and if so ensure   air eliminator valves are fitted

Increase of Manometric   Head

Check valves are fully   open and there are no obstructions in discharge pipe

Impeller, strainer or   check valve clogged

Clean impeller, valve   and strainer

Driver Overloaded

Pump operating at   lower manometric head

The actual head is   lower than originally specified. Reduce impeller size to diameter advised by   supplier or utilise an inverter to reduce pump speed

Speed too high

Decrease pump   rotational speed or trim impeller to required size

Mechanical Friction   inside pump

Check pump rotor for   any obstruction or deflection

Packing wound too   tight

Loosen nuts on packing   gland

Coupling Alignment

Check coupling rubber   and realign pump and coupling

Density or viscosity   of the liquid pumped is higher than originally advised

Increase motor size

Motor Defects

Check for motor   defects. May not be ventilated correctly and be in a poor location

Bearings   Overheating

Poor Coupling   Alignment

Check coupling rubber   and realign pump and coupling

Bearing Covers too   tight

Check and loosen if   necessary, bearing cover

Pumped flow is less   than minimum safe continuous flow

Increase flow. If   necessary, use by-pass recirculating valve or line

Too much grease

Remove excess grease

Insufficient lubrication   or lubricating oil / grease dirty or contaminated

Check the amount of   oil/grease. Clean the bearings, bearing housing and lubricate

Vibration

Partially clogged   impeller

Clean Impeller

Worn or defective   impeller

Replace impeller

Poor Coupling   Alignment

Check coupling rubber   and realign pump and coupling

Oblique Shaft

Check shaft and   replace if required

Unbalanced parts

Check and rebalance   parts if required

Noise level high

Air in liquid

Suction pipe needs to   be submerged to ensure vortexes are not created on the surface of the liquid.

Check liquid level in   suction pipe or increase depth of suction pipe.

Pump working in   cavitation area

NPSH is too low. Check   liquid level in suction tank, check suction losses. Check valve in suction   line and ensure fully open. Increase suction head by lowering pump.

Pump operating outside   of duty range

Check duty point