A progressing cavity pump is a type of positive displacement pump and is also known as a progressive cavity pump, progg cavity pump, eccentric screw pump or cavity pump. It transfers fluid by means of the progress, through the pump, of a sequence of small, fixed shape, discrete cavities, as its rotor is turned. This leads to the volumetric flow rate being proportional to the rotation rate (bidirectionally) and to low levels of shearing being applied to the pumped fluid.
These pumps have application in fluid metering and pumping of viscous or shear-sensitive materials. The cavities taper down toward their ends and overlap. As one cavity diminishes another increases, the net flow amount has minimal variation as the total displacement is equal. This design results in a flow with little to no pulse.
It is common for equipment to be referred to by the specific manufacturer or product names. Hence names can vary from industry to industry and even regionally; examples include: Moineau (after the inventor, René Moineau). The original 4 Manufacturing licenses were issued to; MOYNO pump [Americas], Mono pump [UK, Europe], Gardier [Belgium] and PCM.
A progressing cavity rotor and stator can also act as a motor (mud motor) when fluid is pumped through its interior. Applications include directional well drilling.