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How to Check Efficiency and Performance of Progressive Cavity Pumps

January 31, 2019

To test progressive cavity pump efficiency, we'll need to collect the following flow regulating parameters. There's the power consumption, the energy delivered by a prime mover to monitor. While this measurement is under scrutiny, a test technician measures flow rate and pump pressure. Attenuating pump performance, there are several unique forces that hamper helical rotors as they go about their everyday duties. Interference fit issues top the efficiency attenuating list.

Offsetting Interference Fit Issues

The stator material can hamper rotor kinematics, with the screw slowing slightly as the elastomer stretches. Then there's the finite quantity of rubbing force to offset, with negative interference hampering the screws freedom of movement. Even fluid dynamics, the study of fluid behaviour, impacts pump efficiency. If the liquid in question is non-compressible, it widens the gap between the stator and rotor, thus minimizing abrasive contact, and restores the rotor's freedom of movement. Essentially, there are mechanical and fluid energies that negatively impact pump performance. We need to measure those pump attenuating forces so that they can be dealt with before they gather into a single efficiency dampening cluster.

Measuring the Performance Hampering Energies

The viscosity of the flow medium is measured. Elsewhere, someone needs to measure the flow rate and pressure. Now, the oil industry uses a set of performance measuring instruments, including viscosity testing rheometers, but this approach isn't typically required in most industrial and commercial applications. Pressure gauges and flow meters record those two easy to record metrics, then the viscosity of a known fluid is plugged into a performance determining formula. Water has a known viscosity, as do the syrups and jams used in the food sector. In waste disposal applications, a sector rife with semisolid obstacles, flow approximations are assumed. Meanwhile, in oil processing, the viscosity of a petroleum-based stream isn't always easily predicted, which is why engineers recruit those special viscosity-measuring rheometers.

If a quoted fluid type is mentioned in a pump's manual, it'll be followed by a list of pump capabilities, which would include expected fluid velocities. Of course, there's no such thing as a 100% efficient machine, but progressive cavity pumps are designed to be impressively efficient. Conducting a field test, a handful of gauges is enough to record the flow rate and line pressures. From here, a performance evaluating equation soon tells us whether the measured electrical input power is producing a loss-free output. Again, should heavy losses occur, there are ways of dealing with the negative energies. They include interference fit adjustments and the addition of a mastication or filtration stage, which helps reduce heavier semisolid obstacles.

Contact Alpha Pumps:

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

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