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Rotors and Stators for Progressive Cavity Pumps: How They Work

March 29, 2018

Some confusion surrounds rotor and stator talk. First of all, standard synchronous motors employ these two essential prime mover components, but they're both constructed from electrical windings. On the other hand, progressive cavity pumps utilize mechanically interlocking components. They just don't conform to that standard electrically-powered model. Apart from performing similar roles, they're very different devices. If mutual inductance is a familiar topic, you'll know just what we're talking about.

Mechanical VS. Electrical Relationships

There's no point in spending too much time on this subject, not when it doesn't apply to progressive cavity pumps. Briefly, then, electrical motors use magnetic poles and conductive windings. On the stator, the fixed outer housing, those windings generate an electromagnetic field. Subsequently, the windings on the mounted rotor create a second magnetic field. Through mutual inductance, the rotor uses these interlinking magnetic fields to generate rotating movement. Progressive cavity pumps ditch electromagnetic fields in favour of a mechanical relationship. This time around, a hardened helical rotor creates an interference fit, a relationship that's set up between the screw-like shaft and the fixed-in-place elastomeric stator.

Using Geometry as a Fluid Conveyance Mechanism

The tough rubber tube of the stator enfolds the durable metal rotor. They're both loaded with spiralling geometry, a build that adds a predetermined number of lobes to the rotor. By the way, that chrome or nickel-coated shaft is the only moving part inside the pumping mechanism. Anyway, as that rotor turns it interacts with the stationary housing, which is the elastomeric tube we've labelled the stator. Wavelength is a key pumping attribute here, for these two pumping elements are shaped with peaks and troughs, just like a sinusoidal waveform. Essentially, the wavelength of the stator is twice the length of the waveform employed on the rotor. Connected to a universal joint, and possibly one of those previously mentioned electrical motors, that eccentrically mounted screw mechanism now produces a series of discrete packets. Each cavity conveys a single packet of fluid, be it a near solid lump of jam or a fluid globule full of wastewater.

Like a stretched out piston pump, progressive cavity pumps use that special interference fit as a sealed package transportation vehicle. The positive displacement principle dominates the process, but it's a version of that principle that has been uniquely adapted to manage fluids in a discrete manner. As such, the machinery is longer and more space-consuming than traditional pumping solutions. However, the design more than makes up for that drawback by providing a bundle of singular features, including an aptitude for delivering mix-sensitive fluid, as seen in many food-based facilities.

Contact Alpha Pumps:

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

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