FR2777956A1 - BEARING ASSEMBLY FOR AN ELECTRIC PUMP, IN PARTICULAR A MAIN REFRIGERANT ELECTRIC PUMP FOR A PRESSURIZED WATER NUCLEAR REACTOR - Google Patents

Abstract

The present invention relates to a set of bearings for an electric pump (1), in particular a main refrigerant electric pump for a pressurized water nuclear reactor, comprising at least three radial bearings. This assembly is characterized in that a bearing module (19), comprising an axial bearing (6, 6 ') and a radial bearing (8), is provided between a pump proper (3) and a drive motor (2).

Description

The present invention relates to a set of bearings for a

  electric pump, in particular a main refrigerant electric pump, comprising at least three

radial bearings.

  As regards the main refrigerant electropumps used in the primary circuit of pressurized water nuclear reactors, two main construction modes are already known and used. In a construction mode, the pump and the

  motor are two individual machines and they are coupled by a flexible element.

  The pump and the motor therefore have two radial bearings and one axial bearing each. In this case, we then speak of a provision with four radial bearings. In the second mode of construction or an arrangement with three radial bearings, the pump and the motor have a common shaft which eliminates the aforementioned flexible coupling. The resulting combined device then has a common axial bearing which is located above the

motor, and three radial bearings.

  The pumps circulate water (in normal operation at a temperature of 16 MPa and a temperature of 290 C) in the primary circuit of pressurized water reactors from the steam generator in the reactor core. The shaft is sealed against the atmosphere, against internal pressure

  high prevailing in the primary circuit, by means of multi-stage seals.

  The pump body is closed by means of a sealing housing, a pump body cover and main connection screws. On the cover of the pump body is supported the motor cage and on this the drive motor. Inside the motor cage the shaft is provided with a disassembly fitting which, if necessary, allows

  to have relatively quick access to the sealing system.

  The dismounting connector constitutes, in the assembled state, a rigid shaft coupling. The axial bearing, the upper radial bearing and the intermediate radial bearing are generally lubricated with oil while the lower radial bearing is lubricated with water. The oil-lubricated bearings are supplied either at

  by means of an external power supply unit or a unit integrated in the construction.

  This also applies to the lubricating oil cooler.

  This embodiment requires that the entire pump-motor device is always assembled. As a result, however, significant drawbacks and high costs arise when testing the pump, and in particular a

main refrigerant pump.

  The object of the invention is to obtain that the motor and the pump can be driven in rotation even separate from each other and that an oil supply thereafter

  common for all bearing locations is possible.

  To this end the invention is characterized in that between the pump and the drive motor is provided a bearing module comprising axial and radial bearings. This

  The bearing module can thus be added on one side to the pump and on the other side to the motor.

  Therefore, the motor and the pump can be rotated while also being

separated from each other.

  An advantageous embodiment of the invention is characterized in that the lubricating oil supply device is integrated in the bearing module so that the lubricating oil supply device can supply oil

  the whole apparatus comprising the pump and the motor.

  An advantageous embodiment of the invention is characterized in that the bearing module can be associated, as desired, with the part of the pump or with the part of the motor, by being separate from the other part. Therefore, on the one hand the motor associated with the coupled bearing module can be subjected to a test, for example on a test bench of the motor manufacturer and, on the other hand, one can use, for the examination pump operation, a noticeably smaller motor, which keeps it very

down the bench test fees.

  Another advantageous embodiment of the invention is characterized in that all the necessary auxiliary pumps and the lubricating oil cooler

  are integrated in the bearing module.

  Another advantageous embodiment of the invention is characterized in that the bearing module can be used, with slight modifications, on the cage.

  motor of a type arrangement with four radial bearings.

  Various embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the appended drawings in which: FIG. 1 is a schematic axial section view of a refrigerant pump

  main of the type with three bearings according to the prior art.

  Figure 2 is an axial sectional view of a main refrigerant pump

according to the present invention.

  Figure 3 is a partial sectional view of a bearing module according to the

present invention.

  Figure 4 is a partial axial sectional view of an alternative embodiment of

the invention.

  Figure 5 is a partial axial sectional view of an alternative arrangement of the

four-tier type.

  FIG. 1 represents an electropump with main refrigerant 1 according to the prior art. We see in this figure a motor 2 at the top and a pump 3 at the bottom. A pump wheel 4 is integral with a shaft 5 which is common both to the motor 2 and to the pump 3. In the part of the motor 2 this shaft 5 is supported by an axial bearing 6. To this bearing is connected a upper radial bearing 7. On the other side of the motor 2 there is an intermediate radial bearing 8. In its lower end, in the region of the pump, the shaft 5 is held by a lower radial bearing 9. At the the upper end of the shaft is fitted with a flywheel 10. In order to be able to easily separate the motor from the body 16 of the pump and carry out overhaul work on the pump 3, the shaft 5 has a disassembly fitting 11 which provides a rigid coupling between an upper part 17 of the shaft which passes through the motor 2, and a lower part 18 of the shaft which belongs to the pump 3. The seal is ensured by means of shaft bushings 12 housed in a sealing case 13. This sealing case 13 is connected to u pump body 16 by means of a cover 15 of the pump body and main connection screws 14. On the cover 15 of the pump body is supported a cage 23 of the motor and therefore the drive motor 2. The assembly of the electric pump 1 thus comprises an axial bearing 6 which is situated above the motor 2 and three radial bearings 7,8,9. Pump 3 circulates water (in operation

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  normal at a pressure of 16 MPa and a temperature of 290 C) in the primary circuit of pressurized water reactors, this water coming from the steam generator in the reactor core. The shaft 5 is sealed against the atmosphere, against the high internal pressure, by means of multi-stage seals 12. The body 16 of the pump is closed by means of the sealing housing 13, the cover 15 of the body

  pump and main connection screws 14.

  Figure 2 shows an embodiment of the present invention. In this figure the same reference numbers as those in Figure I are used. Again, this is a three-stage type electropump without coupling between the pump and the motor. Unlike the electric pump represented in FIG. 1, the electric pump illustrated in FIG. 2 comprises a bearing module 19 for the shaft 5 which is located between the motor 2 and the pump 3. In this bearing module 19 there is the intermediate radial bearing 8 as well as the axial bearing 6. The axial bearing 6 can be located just below or just above the intermediate radial bearing 8. Additionally, an oil cooler 20 and auxiliary pumps 21 for the oil supply to the entire electric pump are incorporated in this bearing module 19. The flywheel 10 is disposed

  now between the motor 2 and the intermediate radial bearing 8, in the part of the motor.

  Thanks to this arrangement, it is possible to test the motor 2, with the bearing module 19 coupled, once these are mechanically separated from the pump 3 proper. The mechanical separation is carried out by means of the dismantling connector 11. The combination of the motor 2 and the bearing module 19 now comprises two radial bearings 7,8 as well as an axial bearing 6 and in this combination are also integrated all the devices provided for oil cooling. The actual pump test 3 takes place in conjunction with the bearing module 19. In this bearing module 19 is incorporated a shaft section 22 which replaces the corresponding end part of the upper part 17 of the shaft. The combination of the actual pump 3 and the bearing module 19 comprises two radial bearings 8, 9 as well

  than an axial bearing 6. The oil supply can also be ensured.

  Figure 3 shows in more detail the bearing module 19 with its individual elements. The high axial force, resulting from the pressure in the primary circuit (about 160 bar), which is exerted on the impeller 4 of the pump and which in normal operating conditions is directed upwards, is transmitted by the through the axial bearing 6 and the cage 23 of the motor and then through the cover 15 of the pump body and the main connection screws 14, to the body 16 of the pump. This means that the rotor and the stator of the motor 2 are no longer subjected to the high axial force and that the deformations generated by the axial force are smaller, as are the

  application paths of these forces.

  Due to the high temperature of the water to be pumped (290 C) in operation, it is necessary to take into account thermal deformations and thanks to small paths of application of the forces, the axial differential expansions between the fixed parts and the rotating parts are also small. Therefore, it is possible to maintain relatively small the intervals which are provided, to take account of the axial differential expansions, between the fixed and rotary parts in the hot zone of the pump 3, and possibly the adjustment measures which normally occur during assembly. machines, can be deleted. This also has a positive effect on the exchange possibilities

pieces.

  The lubrication device 24 which is located on the shaft 5 at the lowest point of the oil circuit, supplies all the lubrication points with fresh oil. This lubrication is advantageously provided through holes when this is not possible or not

  possible through pipes (for example for the upper radial bearing).

  This means that the motor 2 with the associated bearing module 19, the shaft 5 having been separated at the location of the disassembly fitting 11, can be transported individually, for example to the test bench of the motor manufacturer. The manufacturers

  pumps and motors are generally not the same.

  The actual pump 3 can also be transported itself to a test bench when the bearing module 19 is associated with the pump 3 and the part of the shaft between the flywheel 10 and the disassembly fitting 11 is replaced by an independent shaft section. During such a bench test, not only the hydraulic characteristics of the pump but also all the other mechanical properties of the electric pump are checked. To this end, the original pump wheel is replaced by a wheel with a significantly smaller power consumption (order of magnitude of 5 to 10% of the original power). Therefore, it is possible to use, for the examination of pump 3, a substantially smaller motor and consequently the costs of examination on the pump bench.

  can be kept correlatively at a very low level.

  FIG. 4 represents an alternative embodiment of the bearing module 19 in which the intermediate radial bearing 8 is arranged above the axial bearing 6 '. However, it is also possible to arrange the intermediate radial bearing 8 below the axial bearing 6 '. The position of the intermediate radial bearing 8 can also be used to

  influence the natural frequency in bending of the rotary assembly.

  FIG. 5 represents an alternative embodiment of the type with four radial bearings.

  It differs from the embodiment shown in FIG. 4 by the provision of additional free space for a flexible coupling 25 and a lubrication device

  additional 26 for coupling 25.

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Claims (6)

  1. Set of bearings for an electric pump (1), in particular a main refrigerant electric pump, comprising at least three radial bearings characterized in that a bearing module (19), comprising an axial bearing (6,6 ') and a radial bearing (8) is provided between a pump proper (3) and a motor drive (2).   2 set of bearings according to claim 1 characterized in that a lubricating oil supply device (20,21) is integrated in the module bearings (19).   3. Set of bearings according to one of claims 1 or 2 characterized in   that a lubricating oil supply device (20,21) supplies the entire electric pump (1) consisting of the actual pump (3) and the motor drive (2).   4. Set of bearings according to one of claims 1 to 3 characterized in that   that the bearing module (19) can operate as desired by being associated with the part of the   pump (3,15,16,18) or to the motor part (2,17), being separated from the other part.   5. Set of bearings according to one of claims 1 to 4 characterized in   that necessary auxiliary pumps (21) and an oil cooler (20) are integrated in the bearing module (19).   6. Set of bearings according to one of claims 1 to 5 characterized in that   that the bearing module (19) is used in an arrangement of the type with four radial bearings.