INTRODUCTION:- Faults in a pump installation can have various causes. The fault may not be in the pump, it may also be caused by the pipe system or the operating conditions. Firstly, always check that installation has been executed in accordance with the instructions in this manual and that the operating conditions still correspond with the specifications for which the pump was purchased.
Faults
The pump, of which you want to determine the fault, may be hot or under pressure. Take the Appropriate precautions first and protect yourself with the proper safety devices (safety goggles, gloves, protective clothing)!
To determine the source of the malfunctioning of the pump, proceed as follows:
1 .Switch off the current supply to the pump unit. Block the working switch with a lock or remove the fuse. In case of a combustion engine: switch off the engine and close the fuel supply to the engine. 2 .Close the stop valves. 3 .Let the pump cool down, if necessary. 4 .Determine the nature of the fault. 5 .Try to determine the cause of the fault and take the appropriate measures,
In general, breakdowns in a pump installation are attributable to the following causes:
1 .Faults with the pump. 2 .Breakdowns or faults in the pipe system. 3 .Faults due to incorrect installation or commissioning. 4. Faults due to incorrect choice of pump.
TROUBLESHOOTING:-
In case of abnormal operation or when troubles occur the pump must be taken out of service immediately. Inform all responsible personnel, prior to restarting the pump the cause of the problem must be determined and the problem to be solved.
Failure to deliver liquid Possible causes a) Wrong direction of rotation b) Pump not filled with liquid c) Inlet or suction pipe insufficient submerged d) NPSH available too low e) pump not up to rated speed g) Air leaks in suction line
Pump does not deliver rated capacity a) Wrong direction of rotation b) Inlet or suction pipe insufficient submerged c) NPSH available too low d) pump not up to rated speed e) Total head greater than design f) Air leaks in suction line. g) Viscosity greater than rated. h) Impeller blocked or damaged
Pump does not develop rated pressure a) Wrong direction of rotation b) pump not up to rated speed c) Viscosity greater than rated d) Gas or vapor in liquid e) Total head lower than rated f) Impeller blocked or damaged
Pumps overloads driver
a) Viscosity greater than rated b) Seep too high. c) Total head lower than rated. d) Total head higher than rated. e) Viscosity and/or specific gravity higher than rated. f) Impeller blocked or damaged. g) Pipes exert forces on pump
Vibration a) Inlet or suction pipe insufficient submerged. b) NPSH available too low c) Gas or vapor in liquid. d) Starved suction. e) Misalignment. f) Worn or loose bearings. g) Impeller blocked or damaged. h) Bent shaft. i) Improper location of discharge valve. j) Foundation not rigid. k) Bearing badly installed
Bearings wear rapidly a) Misalignment. b) Bent shaft. c) Bearing badly installed. d) Pipes exert forces on pump. e) Vibration
Motor heating up
a) Viscosity greater than rated. b) Viscosity and/or specific gravity higher than rated. c) Speed too high, check motor name plate.
Seized pump
a) Pump not filled with liquid. b) Total head greater than design. c) Impeller blocked or damaged. d) Pipes exert forces on pump.
Irregular delivery
a) NPSH available too low b) Air leaks in suction line. c) Gas or vapor in liquid. d) Starved suction.
Pump does not prime a) Wrong direction of rotation b) Pump not filled with liquid c) Total head greater than design. d) Air leaks in suction line.
Noisy pump
a) Inlet or suction pipe insufficient submerged. b) NPSH available too low. c) Air leaks in suction line. d) Viscosity greater than rated. e) Starved suction. f) Misalignment. g) Worn or loose bearings. h) Bent shaft. i) Improper location of discharge valve. j) Foundation not rigid. k) Pipes exert forces on pump. l) Vibration.
Precautionary measures:-
Take adequate measures to avoid that the motor is started while you are working on the pump. This is especially important for electric motors with remote control: • Switch the operating switch near the pump (if available) to “off”. • Switch off the pump switch on the switchboard. • If necessary remove the fuses. • Hang a danger board near the switchboard cabinet. • Insufficient wrong and/or irregular maintenance can lead to malfunctions in the pump, high repair costs and long-term inoperability. Therefore you should carefully follow the guidelines given in this chapter during maintenance operations on the pump.non compliance with prescription or warning may be dangerous for the user and/or seriously damage the pump/pump group. • All work should be carried out by suitable trained personnel. • Pump and piping may contain high pressure liquids, high temperature liquids or/and hazardous chemical fluids even when the unit has been shut down. Before dismantling, always allow the pump to cool (20ºC) and allow it to drain completely. • Ensure that the working area is clean, because certain parts such as the mechanical shaft seals are extremely vulnerable and others have very close tolerances. • Incase of storage: • The pump must be operated briefly once a week or alternatively one manually makes a full revolution of the pump shaft. • This ensures a proper circulation of the protective oil.