Sealed pump

Abstract

A subsea pump, distinctive in that it comprises a pressure housing divided into two compartments; a compartment with pump or impellers arranged on a shaft and a compartment with motor or a stator; a diaphragm arranged sealingly between the compartments, a magnetic coupling between the compartments, through the diaphragm; and a pressure compensation system for balancing the pressure on the diaphragm of the motor or stator compartment side to the pressure on the diaphragm of the pump or impeller compartment side.

Claims

1. A subsea pump, comprising: a pressure housing divided into a first compartment and a hermetically-sealed second compartment; the first compartment having disposed therein at least one of a pump and an impeller, the at least one of a pump and an impeller being arranged on a first shaft for pumping of a process fluid; the hermetically-sealed second compartment having disposed therein one of a motor and a stator of a motor, the motor comprising a rotor arranged on a second shaft; a wall arranged sealingly between the first compartment and the second compartment with the first shaft and the second shaft on opposite sides of the wall; a magnetic coupling between the first compartment and the second compartment, coupling the first shaft and the second shaft through the wall; a pressure balancing system arranged between the first compartment and the hermetically-sealed second compartment for balancing pressure over the wall between the first compartment and the second compartment; a cooling fluid pump arranged on one of the second shaft and the rotor; a hermetically-sealed cooling circuit coupled to and from the second compartment; a combined liquid for flushing, lubrication and cooling, and filling the hermetically sealed second compartment, the combined liquid being pumped by the cooling fluid pump through the hermetically sealed cooling circuit and at least one bearing positioned within the hermetically-sealed second compartment, the combined liquid for cooling, flushing and lubricating the at least one bearing; wherein the subsea pump is without an external barrier fluid supply.

2. The subsea pump according to claim 1, wherein the pressure balancing system controls a pressure differential over the wall to be less than 5 bar by balancing the pressures on either side of the wall.

3. The subsea pump according to claim 1, wherein the second compartment is filled with one of water/glycol and oil as the combined liquid for flushing, lubrication, and cooling, said combined liquid flows in a closed circuit including at least one filter.

4. The subsea pump according to claim 1, wherein the subsea pump is vertically oriented and the wall has a shape like a hat, wherein the rotor is cooled by the combined liquid through of radial conduits that are disposed in a bottom portion of the rotor, and wherein conduits for the combined liquid are also arranged through a radial bearing adjacent the rotor.

5. The subsea pump according to claim 1, wherein the subsea pump is vertically oriented and the wall has a shape like a cup, wherein the rotor is cooled by the combined liquid through conduits arranged inside the rotor and radially out through the rotor.

6. The subsea pump according to claim 1, wherein the at least one bearing is arranged axially apart from the magnetic coupling.

7. The subsea pump according to claim 1, wherein the subsea pump comprises a port so that the combined liquid in the second compartment can be filled or exchanged subsea by a Remotely Operated Vehicle.

Description

FIGURES

(1) The invention is illustrated with three figures, namely:

(2) FIG. 1 illustrating an embodiment of a pump of the invention,

(3) FIG. 2 illustrating another embodiment of a pump of the invention, and

(4) FIG. 3 illustrating a variation of the embodiment illustrated in FIG. 2.

DETAILED DESCRIPTION

(5) Reference is made to FIG. 1, illustrating an embodiment of a pump 1 of the invention, arranged vertically standing. The pump 1 comprises a pressure housing 2 divided into two compartments; namely a compartment 3 with pump or impellers arranged on a shaft and a compartment 4 with motor or a stator. A diaphragm 5 separates the compartments sealingly, a magnetic coupling 6 provides coupling between the compartments, radially through a part the diaphragm 5 having shape and orientation as a cup 5C. A pressure compensation system 7 provides balancing of the pressure on either side of the diaphragm, which means pressure balancing of the motor or stator compartment side of the diaphragm to the pump or impeller compartment side of the diaphragm. Bearings 8 arranged outside the magnetic coupling, supports a motor shaft 9 in the motor compartment and a pump shaft 10 in the pump compartment, respectively. A coupling-rotor 11 arranged inside the cup is cooled and flushed by circulating cooling fluid through an inside the shaft coolant conduit out along the inside magnetically coupled rotor and along and out of the cup. The rotor 11 is the driving part of the magnetic coupling. For simplicity, the cooling and flushing arrangement of the rotor 11 and cup 5C is not illustrated since it would be difficult to see the details in the figure. However, a hollow shaft, or conduits in the shaft, with radial openings out from the shaft, are required for providing said cooling and flushing. A filter in the circulation loop in the motor compartment removes any particles that are flushed out in the closed motor cavity.

(6) FIG. 2 illustrates another pump embodiment of a vertically oriented pump, but where a part of the diaphragm 5 has shape like a hat 5H. In addition to the diaphragm, this embodiment is different from the embodiment illustrated in FIG. 1 with respect to the cooling and flushing. More specifically a rotor 12, the driving part of the magnetic coupling and arranged outside the hat 5H, is cooled and flushed by circulating cooling fluid through coolant conduits arranged inside and outside of the rotor. Conduits for coolant and flushing are also arranged radial inwards in order to cool and flush the hat part of the diaphragm, and through a radial bearing adjacent the external rotor. The circulation system is also used to remove any gas collected in the hat since such gas can come with the pumped process fluid. For simplicity, the cooling and flushing arrangement is not illustrated, since it would be difficult to see the details in the figure, and equipment items similar or identical to the embodiment illustrated in FIG. 1 have no assigned reference numericals, for which reason further reference is made to FIG. 1.

(7) Reference is made to FIG. 3 illustrating a variation of the embodiment illustrated in FIG. 2. More specifically, the hat 5H has been extended to cover also the rotor 13 of the motor, and the cooling and flushing arrangement has been modified, and also the bearing arrangement has been modified. The extended hat 5H provides a canned motor, with a stator compartment 4S on one side of the diaphragm 5 and a rotor on the pump shaft in on the other side of the diaphragm, in a pump compartment 3. The rotor on the pump side is preferably arranged with permanent magnets. A separate rotor 14 in the stator chamber, driven by the stator 15, drives a coolant circulation pump CFP providing cooling and flushing onto and around the hat and for the bearings in the stator compartment.

(8) The illustrated embodiments have an effective cooling and flushing of critical equipment items and volumes, providing cooling, lubrication and flushing out of gas, sand, metal particles and other contamination from critical components in order to avoid the typical problems mentioned earlier, resulting in an extended service life over prior art subsea sealed pumps. Also, the sealed motor or stator compartment requires no barrier fluid feed, eliminating umbilical feed and topsides hydraulic power unit. The effective pressure compensation, allowing purely mechanical, local pressure compensation without remote supply, allows fast response times with respect to pressure compensation, allowing use of a thin walled high strength diaphragm, allowing reduced distance and hence improved magnetic coupling between the driving and driven parts of the magnetic coupling. The diaphragm can be made of any non-ferromagnetic high strength tough material, such as Monell or composite material. The pump of the invention can comprise any feature as here described or illustrated, in any operative combination, each such operative combination is an embodiment of the present invention.