A distinction is made according to the movement type of the displacer. The types are rotary and reciprocating positive displacement pumps.Oscillating positive displacement pumps include
- Piston pump
- Diaphragm pump
The following constructions are counted among the rotating positive displacement pumps:
- Screw pump
- Progressing cavity pumps (eccentric screw pumps)
- Rotary lobe pump
- Gear pump
- Screw pump
- Peristaltic pump
In opposition to the centrifugal pumps the positive displacement pumps are suitable for a very high viscosity of the pumped fluid. Furthermore the reciprocating pumps can be suitable for metering and dosing applications.
They are used especially in the transport of plastic masses and dispersions.Like the eccentric screw pumps, they are suitable for the highest viscosities.
A single-start conveying spindle rotates in a double-start worm housing made of elastic plastic.The eccentrically rotating screw conveyor conveys the medium in the free screw channel of the housing from the suction side to the discharge side in a continuous flow.Eccentric screw pumps are particularly suitable for the transport of highly viscous fluids, mushy, slurry or paste-like media. Like screw pumps, they are suitable for highest viscosities where the use of centrifugal pumps is not possible.
