36
No flow
Under capacity
Irregular discharge
Low discharge pressure
Pump will not prime
Prime lost after starting
Pump stalls when starting
Pump overheats
Motor overheats
Excessive power absorbed
Noise and vibration
Pump element wear
Syphoning
Seizure
Mechanical seal leakage
Packed gland leakage
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9 Incorrect direction of rotation. Reverse motor.
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9 Pump not primed. Expel gas from suction line and pumping chamber and
introduce fluid.
Increase suction line diameter.
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9 Insufficient NPSH available. Increase suction head.
Simplify suction line configuration and reduce length.
Reduce pump speed.
Increase suction line diameter.
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9 Fluid vaporising in suction line. Increase suction head.
Simplify suction line configuration and reduce length.
Reduce pump speed.
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9 Air entering suction line. Remake pipework joints.
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9 Strainer or filter blocked. Service fittings.
Increase fluid temperature.
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9 Fluid viscosity above rated figure. Decrease pump speed.
Check seal face viscosity limitations.
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9 Fluid viscosity below rated figure. Decrease fluid temperature.
Increase pump speed.
Cool the pump casing.
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9 Fluid temp. above rated figure. Reduce fluid temperature.
Check seal face and elastomer temp. limitations.
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9 Fluid temp. below rated figure. Heat the pump casing.
Increase fluid temperature.
Clean the system.
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9 Unexpected solids in fluid. Fit strainer to suction line.
If solids cannot be eliminated, consider fitting double
mechanical seals.
Discharge pressure above rated Check for obstructions i.e. closed valve.
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9 figure Service system and change to prevent problem recurring.
Simplify discharge line to decrease pressure.
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9 Gland over-tightened Slacken and re-adjust gland packing.
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9 Gland under-tightened Adjust gland packing.
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9 Seal flushing inadequate. Increase flush flow rate.
Check that flush fluid flows freely into seal area.
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9 Pump speed above rated figure. Decrease pump speed.
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9 Pump speed below rated figure. Increase pump speed.
Pump casing strained by Check alignment of pipes.
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9 pipework. Fit flexible pipes or expansion fittings.
Support pipework.
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9 Flexible coupling misaligned. Check alignment and adjust mountings accordingly.
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9 Insecure pump driver mountings. Fit lock washers to slack fasteners and re-tighten.
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9 Shaft bearing wear or failure. Refer to pump maker for advice and replacement parts.
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9 Insufficient gearcase lubrication. Refer to pump maker’s instructions.
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9 Metal to metal contact of Check rated and duty pressures.
pumping element. Refer to pump maker.
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9 Worn pumping element. Fit new components.
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9 Rotorcase cover relief valve Check pressure setting and re-adjust if necessary.
leakage. Examine and clean seating surfaces.
Replace worn parts.
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9 Rotorcase cover relief valve Check for wear on sealing surfaces, guides etc. -
chatter. Replace if necessary.
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9 Rotorcase cover relief valve Re-adjust spring compression - valve should lift approx.
incorrectly set. 10% above duty pressure.
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9 Suction lift too high. Lower pump or raise liquid level.
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9 Fluid pumped not compatible Use optional materials.
with materials used.
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9 No barrier in system to prevent Ensure discharge pipework higher than suction tank.
flow passing.
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9 Pump allowed to run dry. Ensure system operation prevents this.
Fit single or double flushed mechanical seals.
Fit flushed packed gland.
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9 Faulty motor. Check and replace motor bearings.
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9 Pumping element missing Fit pumping element.
4. Maintenance 4.7 Troubleshooting
Problem
Probable Causes Solutions
