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28
C.
NOT ENOUGH PRESSURE ON PRESSURE GAUGE
Possible Causes
Corrective Action
1. No Restriction on Pump Discharge.
Close valve on discharge side at start up.
2. Speed Too Low.
Slipping drive belts – check belt tension. Check driver
sheave and verify correct size for required speed.
Check whether motor is directly across-the-line and
receiving full voltage. Frequency may be incorrect,
motor may have an open phase.
3. Wrong rotation.
Check motor rotation with required pump rotation.
Pump rotation is clockwise viewed from manifold end of
pump.
4. Obstruction in Liquid Passages.
Dismantle pump and inspect passages of pick-up tube,
rotor cover and manifold. Remove obstruction.
5. Air Leak in Suction Line.
Suction line can be tested by shutting off or plugging
inlet and putting line under pressure. A gauge will
indicate a leak with a drop of pressure.
6. Air or Gases in Liquid.
May be possible to over rate pump to point where it will
provide adequate pressure despite condition. Better to
provide gas separation chamber on suction line near
pump.
7. Head Lower Than Rating, Pumps Too Much Liquid
Pump may be operating at a higher flow rate than
suspected. Throttle pump at discharge to reduce flow.
8. Pick-up Tube Damaged.
Dismantle pump and inspect pick-up tube for erosion or
damage.
9. Inlet Cavitation.
Insufficient NPSH (Net Positive Suction Head)
available. Available NPSH must always equal or
exceed the required NPSH of the pump. Depending on
installation:
A.
Increase inlet pressure to pump.
B. Reduce inlet pipe friction losses.
C. Increase height of suction vessel.
D. Pressurize suction vessel.
E. Lower the pump.