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Causes of Drive Shaft Failure in Pumps

January 29, 2018

Power flows through a drive shaft. The kinetic energy rotates a universal joint, it arrives at a pump housing, and an impeller rotates. It's a simple enough sequence, one that relies on this vital bridging rod. Unfortunately, drive shaft failures do occur. Subsequently, when that coupling breaks, the pumping mechanism is isolated from the power source. All things considered, maybe we should determine the causes of these failures.

Modeling Impeller Attenuation

A finely fabricated impeller can take many forms. There's the classic disc-shaped format, a type that revolves inside a system volute. At the other end of the pumping spectrum, advanced pumping mechanisms employ long rotors. These progressive cavity units convey shear-free material, perhaps in a food processing plant. Whatever the shape, these impellers are damage-prone. The damage either entirely clogs the rotating component, or it impacts the part in such a way that it starts to vibrate. Logically, that completely stoppered impeller will damage the prime mover. A circuit breaker trips or the electromagnetic windings burn out. Arguably, that clog in the volute could cause a drive shaft failure. However, it's usually the loosely vibrating component that really places unmanageable stress on this important drive coupling. The power transmission imbalance, left uncorrected, quickly undermines the drive shaft. As a result of this imbalance, the pump bearings and drive shaft incur damage.

Rotor-Based Drive Failure Incidents

Fluid conveyance characteristics being what they are, at least in this specialized pumping configuration, there are more risk factors in play here. An elastomeric stator swells because of the heat load carried in the water. If the temperature isn't responsible for the swelling, some corrosive chemical is responsible. The stator can't expand outwards, so it swells towards the rotor. The carefully established gap, held between the stator and rotor as a pocket sealing intermediary, closes rapidly. Instead of that fluid seal, abrasive motion takes over. Experienced at its worst, this scenario brings everything to a screeching halt. But what if the abrasion fluctuates? Well, the pump will continue operating, but that coupling rod will likely fail. The universal joints simply can't endure this load forever.

Drive shafts rely on a linear operating plane. Granted, there are flexible drive couplings available, but that solution can only be implemented when the angular irregularity is known. Otherwise, the bearings and pump components must be properly aligned. Furthermore, if vibrational damage is an issue here, the cause of the propagating system noise must be addressed. By the way, semi-solid fluid mediums also engender clogs and unsustainable vibrational events, so do correct this coarse flow problem before it impacts the drive components.

Contact Alpha Pumps:

Phone:    (03) 9311 7188
Fax:          (03) 9364 9554
Mobile:    0403 030 830
Email:      alphapumps@optusnet.com.au

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