SCREW PUMPS

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Screw Pumps

Several different types of screw pumps exist. The differences between the various types are the number of intermeshing screws and the pitch of the screws

Screw type pumps usually have either two or three screws, they can operate at high speeds and give a smooth discharge with almost no pulsations.

In the screw pump, liquid is trapped and forced through the pump by the action of rotating screws. As the rotor turns, the liquid flows in between the threads at the outer end of each pair of screws. The threads carry the liquid along within the housing to the centre of the pump where it is discharged.

Single screw pumps are commonly called progressive cavity pumps.  They have a rotor with external threads and a stator with internal threads.  The rotor threads are eccentric to the axis of rotation.

The stator has an internal helix of different pitch to the rotor. The geometry means that the rotor moves vertically whilst turning and so the meshing of the rotor and stator causes the cavity to progress to the discharge.

The screw is an interference fit in the stator and so this pump must always have liquid present to prevent overheating and failure