Troubleshooting of pump
Excessive power consumption
Excessive power consumption can be caused by either mechanical or hydraulic problems. Mechanical causes include imminent bearing failure, pumping elements rubbing which can lead to a pump seizure and poor shaft alignments. Too high viscosity can result in the motor overloading.
Other reason for excessive power consumptions are given below:
Rotating element binding from misalignment
Specific gravity or viscosity of liquid pumped is too high
Discharge pressure higher than calculated
Electrical or mechanical defect in submerged motor
Higher fluid viscosity than specified
Improperly adjusted packing gland (too tight) causing drag
Incorrect lubrication of driver
Mechanical defects (shaft bent, rotating element binds) on shaft
Pump running too fast
Stuffing boxes too tight, wearing rings worn
For a rotary lobe pump too high discharge pressure can cause the motor to overload.
For a centrifugal pump too high capacity (too low discharge pressure) can cause the motor to overload.
Insufficient Pressure
Cavitation is caused by insufficient system inlet pressure to the pump. This can be caused by an inlet system restriction, excessive fluid viscosity or excessive pump speed. Inlet restrictions can include dirty or clogged inlet strainers, debris floating in the fluid supply that covers the inlet piping intake, or rags. If the fluid is cooler than design temperature, its viscosity may be too high causing excessive friction in the inlet piping system. Cavitation is frequently accompanied by noise, vibration and significant increase in discharge pressure pulsation. If a pump is allowed to cavitate over long periods this will cause damage to the pump components.
Reasons for insufficient pressure are given below:
Impeller installed backwards
Impeller speed too low
Leaking joints (well application)
Mechanical defects: wearing rings worn;
Impeller diameter too small
Air or gas in liquid
Excessive lift on rotor element
System head lower than anticipated
Fluid supply exhausted
Fluid vaporizes in inlet line, fluid may be overheated
Wrong direction of rotation
Loss of Prime
Air leaks developed in suction line
Insufficient Discharge
Insufficient/Low discharge pressure can only be caused by loss of flow. Pump discharge pressure is caused only by the system’s resistance to the flow provided by the pump. Either the pump is not providing the flow expected or the system is not offering the expected resistance to that flow. It is possible that flow is being restricted into the pump (cavitation), usually accompanied by noise and vibration, the pump is not producing its rated flow (pump worn or damaged), or the pump flow is bypassing rather than being delivered into the system as intended.
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