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Life Expectancy of Pump Rotors

August 27 2018

On paper, pump rotors are uncomplicated components. They rest on bearings, rotate within stators, and there's very little that can go wrong. In the real world, however, there's so much that can and often does go astray. Accumulating over time, these faults impact the shaft's performance. Essentially, the life expectancy of pump rotors is influenced by many factors.

Three-Phase Synchronous Pumps

There are numerous examples of rotating pumps. They work flat-out in HVAC rooms and who knows where else, but this is probably the most common configuration. What could possibly shorten the lifespan of this ever-popular equipment? Well, think about the bearings. Uneven shafting arrangements and unpredictable loads place stress on bearings. Then there's the coupling between the motor and the pump. If this is a belt-driven device, its life expectancy will drop significantly. Geared models and stronger coupling solutions last longer. Even the motor, again stressed, has an inbuilt lifespan. Overstressed, a stink of electrical windings varnish wafts free as the electrics short out.

Progressive Cavity Pumps

The rotating pump is failing. Its impeller and volute chamber are both damaged, which means its days are numbered. Elsewhere, a nickel or chrome coated helical screw is pumping waste or some other thick fluid. The life-shortening factors here are mechanical wear and fluid abrasion. In here, velocity isn't a typically relevant parameter, but smooth load commutation is essential. Abrasive materials scour away protective coatings, high temperatures bake elastomeric stators, and cavitation effects trigger tiny little turbulence-actuated detonations. Meanwhile, the prime mover coupling assembly is beginning to feel the mechanical stress.

Extending Mechanical Life Cycles

Fortunately, design engineers do know how to address such longevity skewing issues. Stronger alloys work well, as do thicker layers of protective coatings. If off-centre loading issues are a problem, flexible couplers can absorb misalignment errors and ease bearing stress. Even commonplace rotary pumps have access to life expectancy aids, which come in the form of metal impellers and more durable coupling interfaces. As ever, each pumping scenario needs a case-by-case approach.

The life expectancy of pump rotors is a curiously counterintuitive subject. After all, pump components naturally generate vibration and radial stress. It's up to the engineer in charge to find a wear nullifying mechanism. Flexible couplers, gearing mechanisms and thrust-capable bearings provide amicable solutions here, but there's more to be done. The fluid medium and its abrasive or output choking properties require assessment. Add dampening pads to motor and pump housings. Separate noise propagating waves by separating different pump stages, and then install cable-carrying hoses. Use mechanical noise and fluid turbulence reduction technology to maximize pump life expectancies.

Contact Alpha Pumps:

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

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