What Is a Progressive Cavity Pump?
A progressive cavity pump is a type of positive displacement pump that is adaptable to some of the toughest pumping applications and most difficult fluids. While it is a versatile pump that can handle a variety of jobs, it is perfectly designed for fluid metering and pumping viscous, abrasive or shear-sensitive materials.
Other terms for progressive cavity pumps include: progressing cavity pumps, PC pumps, cavity pumps, and progg cavity pumps.
How does a progressive cavity pump work?
Like all positive displacement pumps, PC pumps are flow-creating devices. They move fluid at the same speed regardless of the pressure on the inlet end.
PC pumps draw fluid in through a suction inlet which feeds into an elongated casing. Within the casing is a helical rotor and stator assembly. The rotor helix is offset to the stator. As the rotor turns and contacts the surface of the stator, a series of small cavities form. The fluid “progresses” through these cavities until it is expelled through a discharge outlet.
PC pumps can’t be run dry. The heat generated by the rotor and stator can cause pump failure. Most PC pumps have accessory options as a safeguard against this.
When to use progressive cavity pumps?
Dosing & Metering Applications
The cavities inside a PC pump taper at their ends and overlap, so there is no flow pulsing other than that caused by compression of the pump components or fluid. It is this smooth, low pulsation pumping that makes PC pumps so well-suited to metering applications.
The flow rate of PC pumps are proportional to their speed, so they can be used to dose viscous fluids such as additives and chemicals.
Pumping Shear-Sensitive Materials
The volumetric flow rate of a PC pump is proportional to its rotation rate. This applies very little shear to the pumped fluid. This feature, along with a lower internal velocity, makes PC pumps ideal for pumping shear-sensitive materials like fluids with fragile solids.
Pumping Materials with Abrasive Particles
In other pump designs, fluids travel around the inside walls of the casing at high speed. When the pumped material contains abrasive solids, this in effect “scours” the pump’s surfaces and causes it to wear out before its useful lifespan.
A progressive cavity pump, on the other hand, takes the fluid through a long casing. The abrasive particles travel parallel to the internal surfaces at a lower speed, rather than hitting them centrifugally at high speed. This makes PC pumps much more abrasion-resistant and long-lasting than other pump types for these applications.
Pumping Heavy or Viscous Fluids
Progressive cavity pumps are ideal when pumping fluids with higher viscosities. With a centrifugal pump, flow rate goes down as fluid viscosity goes up. This is less efficient as the pump must then increase its energy consumption in order to keep up. PC pumps, like other types of positive displacement pumps, create flow. A PC pump is actually more efficient as viscosity increases, and will have approximately the same flow rate no matter the weight of the pumped material.
Applications That Involve Varied Flow
PC pumps produce a precise flow per revolution, making it easy to manage the pump flow by simply regulating the pump speed. They pair well with variable frequency drives for managing flow rates. Likewise, PC pumps can be used when you need a steady flow but the viscosity of the pumped fluid is variable.
What are progressive cavity pumps used for?
Typical applications and uses of PC pumps include:
- Metering and dosing
- Chemical manufacturing
- Oil pumping/petroleum production
- Food and beverage processing
- Pulp and paper
- Environmental technology
- Sewage, sludge and slurry pumping
- Grout or cement pumping
- Limited energy well water pumping
- Lubrication oil pumping
What are some other advantages of progressive cavity pumps?
Progressive cavity pumps are self-priming, have higher discharge pressure than many other positive displacement pumps, and have high suction lift.