When a centrifugal pump is not appropriate for the pumping purpose, a Progressing Cavity Pump is employed. When the liquid has a higher viscosity—or thickness—than water, this is one of the most obvious indications that a progressive cavity pump should be used. When the viscosity of the liquid increases, centrifugal pumps become very mechanical and volumetrically inefficient, which causes the flow to decrease and the power consumption to rise. The opposite is true for progressive cavity pumps; as viscosity rises, mechanical efficiency and volumetric efficiency increase, resulting in reduced power requirements and increased flow.
A Progressing Cavity Pump is also the best option when the application needs a variable flow. A progressive cavity pump produces a precise flow for each pump revolution. Therefore, controlling the pump speed alone makes it very simple to control the pump flow. Progressive cavity pumps can be utilised with modern pump speed controllers such variable frequency drives (VFDs) for altering pump speed and flow control.
