Troubleshooting
78
216 Series
Twin-Screw Pump -
Installation, Operation, and Maintenance Manual
Troubleshooting
Operation troubleshooting
Symptom
Cause
Remedy
The pump is not delivering
liquid.
The pump is not primed.
Re-prime the pump and check that the pump and
suction line are full of liquid.
The suction lift is too high.
Shorten the suction pipe and/or increase the
diameter and/or reduce the number of “lossy”
fittings.
The pump is rotating in the wrong direction.
Change the rotation. The rotation must match the
rotation arrow on the pump.
The foot valve or suction pipe opening is not
submerged enough.
Increase the submersion depth.
Use a baffle in order to eliminate vortices.
Air leaks into the suction line or pump
Locate the source of the air leak and rectify.
Typical locations are single mechanical seals
(without quench), flange gaskets and valve stem
packings.
The suction pipe is clogged.
Remove the obstruction from the suction pipe.
Relief valve is incorrectly set.
Adjust relief valve to open at the set pressure
indicated on the pump nameplate.
The pump is not producing
the rated flow.
The operating speed is too low (when a VFD
or gearbox is used)
Verify the VFD settings and correct as required.
Verify the motor and/or gearbox nameplate
speeds and change out if necessary.
The foot valve or suction pipe has high
losses.
Shorten the suction pipe and/or increase the
diameter and/or reduce the number of “lossy”
fittings.
Air leaks into the suction line or pump
Locate the source of the air leak and rectify.
Typical locations are single mechanical seals
(without quench), flange gaskets and valve stem
packings.
The suction pipe is partly clogged.
Remove the obstruction from the suction pipe.
Relief valve is incorrectly set.
Adjust relief valve to open at the set pressure
indicated on the pump nameplate.
The suction lift is too high.
Make sure that the suction-line shutoff valve is
fully open and that the line is unobstructed.
Verify the minimum suction pressure or liquid
level is within specification.
Verify the fluid vapor pressure is within
specification
The liquid is less viscous than specified
Bring the liquid viscosity to within specification or
have the pump rerated for the new condition.
The discharge pressure is too high
Bring the discharge pressure to within
specification or have the pump rerated for the
new condition.
The pump is worn or damaged.
Inspect and replace the pump if necessary.
