A Quick Guide To Progressive Cavity Pumps And How To Make Them Last Longer
Progressive cavity pumps (PC pumps) are highly accurate metering pumps that are part of the rotating positive displacement pump family. With a wide range of possible applications, they’re used in all types of industry.
Why use a progressive cavity pump?
PC pumps are an excellent choice for tough pumping applications, like fluids with a higher viscosity or thickness than water, as these are usually beyond the range of centrifugal pumps.
It’s also suited for applications where the fluid is abrasive or toxic, and in agricultural applications where the fluid is shear-sensitive, such as when moving fruits or berries.
How do progressive cavity pumps work?
A PC pump has a rotor (usually made of solid metal) shaped as a single helix inside a flexible or rigid elastomer stator. It has a double helix cavity to pump viscous liquids at high pressures. As the rotor turns, cavities are opened and closed, allowing the fluid to be transferred from one cavity to the next, and ultimately, to discharge the fluid at the required system pressure.
A progressive cavity pump will have roughly the same flow, regardless of the liquid’s viscosity. This makes the PC pump a smart choice for pumping applications that need constant flow even as the liquid’s viscosity changes. It’s also suited for varied flow applications because you can regulate the flow by regulating the pump speed, either manually or with variable frequency drives (VFD’s).
When suction conditions aren’t great, a progressive cavity pump needs a much lower Net Positive Suction Head (NPSH) to a centrifugal pump. This is because its internal pump velocity is lower. As the internal velocity of the liquid as it travels through the pump is much lower than other types of pumps, the PC pump is designed to last longer on abrasive applications.
Of course, with any pros come cons, and we’ve written another article on the various reasons why a PC pump could be the right solution for you, or not.
Here’s how to keep progressive cavity pumps running smoothly and reduce maintenance costs:
- As stators are the part that usually wears out first, you can save on replacement costs by reversing and reusing them. However, they must be replaced if worn or gouged in any way
- For every two stators replaced on the pump; make sure you replace the rotor
- Check wear at proper intervals (as specified in the manufacturer instructions) and you can save the cost of a new rotor
- If you see rotor wear before the chrome plating is removed, this can be re-chromed. However, if they’re worn past the chrome plating, you’ll need to replace the rotor
- Use a lubricant when installing the rotors into the stators to avoid swelling. Castor oil is an inexpensive solution. Note: If the pump is food- or pharmaceutical-grade, check for restrictive and special requirements for lubricants, especially those that contact the fluid
- Flush the pump while its in place for easier maintenance
- Cover the suction and discharge opening to keep out foreign objects
- Make notes and take pictures of connections and orientations
- Place protective caps on the ends of spare stators to prevent deterioration
- Purchase your spare and replacement rotors and stators from the same place as every manufacturer has different specifications, dimensions, and tolerances. This will ensure the best possible performance.
If you want advice on keeping your progressive cavity pump running smoothly for longer, or you’re trying to decide if the PC pump is the right buy for your application, call our toll-free number 1-800-367-4180. We have experts on hand to help you choose, install, and maintain a variety of equipment. And to answer questions about things you’ve previously tried gone wrong.