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Troubleshooting
No fluid is delivered
• Power is not on
• Net positive suction head available (NPSHa) is
lower than required for the vapor pressure of the
liquid pumped
• You should calculate NPSHa and redesign piping,
if necessary
• There are leaks in suction line
• Direction of shaft rotation is incorrect
• Relief valve setting is too low (if the pump is
equipped with a relief valve). Liquid is discharging
through the by-pass port
Capacity is too low
• There are air leaks in suction line
• Suction losses are too high. The suction lift is too
great or the suction line is too small or too long
• This can be detected by installing a vacuum gauge
directly at the pump suction
• The maximum vacuum at the pump suction
should never exceed 15” of mercury
• Vaporization caused by higher vacuums will
generally result in capacity drop-off
• Redesign suction conditions
• Pump speed is too slow
• Strainer is too small or obstructed
• Suction pipe or port is not immersed in liquid
deep enough
• Piping is improperly installed permitting an air
pocket to form in the pump
• Increased clearances or wear in the pump
will sometimes cause the pump to deliver an
insufficient supply of liquid.
Pump works spasmodically.
• Leaky suction lines
• Suction conditions vary
• Air or vapor is in the liquid
• Problem: Excessive power draw
• Pressure is too high
• Liquid is more viscous than originally expected
• Suction or discharge line is obstructed
•
There is insufficient horsepower
• There are mechanical defects
• Drive shaft and pump are misaligned
• Pump is binding due to incorrect clearance setting
• Pump shaft is bent
• Misalignment due to bad piping/poor installation
causing strain or distortion
Pump is noisy
• Pump is cavitating due to inadequate suction
conditions
• There is misalignment of coupling
• Coupling is set too close to pump
• There is vibration of the pump due to a worn or
bent shaft
• There are air leaks on suction side of pump or air
entrainment in the fluid
Pump leaks
• Bolts need tightening, allowing gaskets or O-rings
to leak
• Gaskets or O-rings are damaged
Note:
Packings are designed to leak. Leakage should be at
a rate that will prevent excessive heating on the bracket at the
packing area.
