A progressive cavity pump is a kind of pump which moves fluid by means of a cavity which progresses along the body of the pump. As the cavity moves, fluid is sucked in to fill the cavity, further rotation of the pump causes the fluid to flow and be delivered from the pump.
The rotor of the pump is a steel helix which has been coated in a smooth hard surface, normally chromium. The rotor fits inside a pump body (the stator) which normally is a rubber lined steel tube. The rubber core of the stator has a helical cavity, the wavelength of each helix in the rotor is exactly half that of the rotor; in other words, the rotor turns inside the tube in such a way that one point along the helix is at the edge of the cavity, and the opposite point is at its center. Rotation of the rotor inside the stator causes the cavity to progress along the pump thus inducing fluid flow. Compare to a Archimedes' screw and a helical pump.
Whilst progressive cavity pumps offer long life and reliable service, abrasive fluids will significantly shorten the life of the stator. A unique feature of the progressive cavity pump is the design of its stator. Common designs are the "Equal-walled" stator and the "Unequaled walled" stator. The latter, being unequal in wall-thickness allows for larger sized-solids to pass through because of its ability to compress under pressure. The interface between rotor and stator is lubricated by the fluid being pumped, however if the pump is allowed to 'run dry' rapid deteriotation of the stator results. The term "run dry" is loosely related to the pump's self-priming capabilities. This means the pump is able to run dry for a given period of time while it draws in the pumped medium.
Typical applications[]
- Small sewage pumps
- Sewage sludge pumps
- Slurry pumping
- Cement pumps
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