Lobe Pump Troubleshooting Guide

Motor Operational but No Fluid Delivery

Direction of Rotation

Check direction of rotation is in line with arrow on casing and   nameplate

Air pocket in suction line

Ensure suction line filled with fluid, pipework slopes upwards, no   kinks in suction line and pipework is as straight as possible.

Relief Valve Failure

Clean Relief Valve. Check pressure setting. Recalibrate

Check Valve Jammed

Clean check valve. Check operation

Air Ingress through Seal

Check seals for air ingress, all pipework, and connected gaskets.   Check pump O Rings. Replace pump seal if necessary.

Insufficient Capacity

Relief Valve Opening or Jammed

Check relief valve settings. Recalibrate. Check and clean as a plug   may have formed or solid entered jamming open.

Air Ingress

Check seals for air ingress, all pipework, and connected gaskets.   Check pump O Rings. Replace pump seal if necessary.

Low NPSH

Shorten and enlarge suction line diameter. Deepen suction pipe,   increase tank contents, reduce pump speed and check fluid viscosity against   pump design

Pump Worn

Check internal lobe spacing. Replace lobes

Check Valve Jammed

Clean check valve. Check operation

Pump Noisy

Pump Cavitating

Increase pipework diameter. Reduce suction head. Check fluid   viscosity. Clean filters. Reduce pump speed. Increase fluid level in tank.

Lobe / Rotor Damage

Check lobes and replace if necessary

Misalignment

Realign Pump. Check coupling and rubber

Vibration in safety valve

Increase pressure setting or replace