Rotary positive displacement pump with magnetic coupling having integrated cooling system

1. A pump for liquid medium, comprising:

a pump casing containing:

a forward pumping section having an inlet and an outlet, and

a rearward magnetic coupling section having an inner magnetic rotor and outer magnetic rotor separated by a separation can, which outer magnetic rotor transmits rotation via magnetic coupling to the inner magnetic rotor,

a main pump in the pumping section that is a rotarty positive displacement pump that provides suction through the inlet and discharges through the outlet,

whereby the main pump is mechanically connected to a rotor shaft mounted in a plane bearing, which shaft is connected to the inner magnetic rotor,

a circulation pump in the pumping section configured to cool the plane bearing and magnetic coupling, wherein the circulation pump is a rotary positive displacement pump mechanically connected to said rotor shaft;

a rearward annular passageway, RAP, concentrically arranged over a rearward end of the plane bearing and whereby

a forward face of the hub of the inner magnetic rotor forms a boundary surface of the RAP,

a concentric ring chamber connects the RAP with the rearward end of the plane bearing,

a longitudinal supply passage in the casing running from outlet of the circulation pump towards said hub, whereby the longitudinal supply passage opens into said (RAP); and

a plurality of apertures in said hub running in a longitudinal direction from the forward to the rearward face of the hub, said arrangement allowing medium from the outlet of the circulation pump to flow across the plane bearing and across a gap between the separation can and inner magnetic rotor.

2. The pump according to claim 1 , wherein the circulation pump comprises an inlet port connected to the outlet of the main pump via a liquid-conducting passage.

3. The pump according to claim 1 , wherein the casing comprises a plurality of liquid-conducting passages for conducting medium to the plane bearing and inner magnetic rotor, and whereby an outlet of the circulation pump is connected to said conducting passages.

4. The pump according to claim 1 , wherein the main pump and the circulation pumps are gear pumps.

5. The pump according to claim 4 , wherein the main gear pump comprises a rotor and an idler, whereby the rotor is mechanically connected to the rotor shaft.

6. The pump according to claim 4 , wherein the circulation gear pump comprises a rotor and a drive gear, whereby the drive gear is mechanically connected to the rotor shaft.

7. The pump according to claim 4 , wherein the axes of rotation of the main pump rotor, the circulation pump drive gear, the inner magnetic coupling, and the rotor shaft are coaxial.

8. The pump according to claim 1 , wherein

the plane bearing comprises a shaft sleeve in connection with the shaft, supported buy two bearing bushes flanked by two axial bearing rings,

the concentric ring chamber connects the RAP with the interface between a rearward bearing bush and a rearward axial bearing ring.

9. The pump according to claim 1 , further comprising,

a forward annular passageway, FAP, concentrically arranged over a central section of the plane bearing and whereby

a front end of the inner magnetic rotor forms a boundary surface of the FAP, and

one or more radial passages connect the FAP with the central section of the plane bearing,

a longitudinal exit passage in the casing running from the FAP to the inlet of the main pump, said arrangement allowing medium returning from the plane bearing and from the gap between the separation can and inner magnetic rotor to exit via the inlet of the main pump.

10. The pump according to claim 9 , further comprising a diversion passage in the casing that connects the outlet port of the main pump with the forward end of the plane bearing, said passage allowing medium to flow from the outlet port of the main pump to flow across the from the plane bearing and to exit via the FAP.

11. The pump according to claim 10 , further comprising a forward concentric ring chamber that connects the diversion passage with the forward end of the plane bearing.

12. The pump according to claim 11 , wherein

the plane bearing comprises a shaft sleeve in connection with the shaft, supported by two bearing bushes flanked by two axial bearing rings,

the concentric ring chamber connects the diversion passage with the interface between a forward bearing bush and a forward axial bearing ring.