Eccentric screw pump with a rotor of a drive shaft circulating essentially about a fixed axis in relation to the stator in a bearing block, a power train and a screw conveyor, which revolves in a rotating-oscillating manner in a screw flight of the stator, wherein the power train provides the screw conveyor with its drive torque and the power train adjusts the differences of the motion sequences of the screw conveyor and of the drive shaft, wherein the power train consists essentially of a one-piece rotational body, which has multiple weakening recesses, which interrupt its outer circumferential jacket surface more than only insignificantly and which provide it with that reversible elasticity, which it requires in order to rotate about an axis of rotation, which curves in a periodically recurring manner at least in sections.

A shaft coupling for coupling a prime mover shaft to a power input shaft of a progressive cavity pump can include a first half shell and a second half shell. Each of the half shells can include a first end and a second end along a longitudinal center axis, the first end can include an inner contour which can be configured to match an outer contour of the prime mover shaft and the second end can include an inner contour which can be configured to match an outer contour of the power input shaft. The shaft coupling can include a fastening mechanism, which can be configured for applying a force on the first half shell and the second half shell that can be in a radially inward direction, where the force can be applied through the longitudinal center axis.

A system includes an electric submersible progressive cavity pump (ESPCP). The ESPCP includes a stator having an internal bore, and a hollow rotor disposed in the internal bore of the stator, where the hollow rotor is configured to rotate within the internal bore to pump a fluid via a plurality of progressive cavities.

Eccentric screw pump with a rotor of a drive shaft circulating essentially about a fixed axis in relation to the stator in a bearing block, a power train and a screw conveyor, which revolves in a rotating-oscillating manner in a screw flight of the stator, wherein the power train provides the screw conveyor with its drive torque and the power train adjusts the differences of the motion sequences of the screw conveyor and of the drive shaft, wherein the power train consists essentially of a one-piece rotational body, which has multiple weakening recesses, which interrupt its outer circumferential jacket surface more than only insignificantly and which provide it with that reversible elasticity, which it requires in order to rotate about an axis of rotation, which curves in a periodically recurring manner at least in sections.

A system includes an electric submersible progressive cavity pump (ESPCP). The ESPCP includes a stator having an internal bore, and a hollow rotor disposed in the internal bore of the stator, where the hollow rotor is configured to rotate within the internal bore to pump a fluid via a plurality of progressive cavities.

A method for determining or monitoring the effective delivery flow of an eccentric screw pump that has a rotor rotating eccentrically in a stator at a pump frequency. The effective delivery flow is determined from the difference between an ideal delivery flow and a backflow, which backflow is dependent on at least one gap in the sealing line between rotor and stator. An operating parameter of the pump representing the gap is measured which pulses periodically with the pump frequency, the pulsation amplitude of which is dependent on the state of wear of the rotor and/or of the stator and is related to a tilting of the rotor in the stator. The backflow is calculated repeatedly using a mathematical model in dependence on the measured values for the operating parameter and on predetermined characteristic values of the pump and/or of the medium to be delivered.