JPH06249182A - Canned motor-type pump - Google Patents

Abstract

PURPOSE:To improve corrosion resistance and life by connecting a motor and an auxiliary impeller for circulating bearing cooling water to a shaft to which an impeller is connected in a motor casing and arranging the clearance between a motor stator and a motor rotor on the downstream side of discharge liquid of the auxiliary impeller. CONSTITUTION:An impeller 6 is attached to a shaft 3 by an impeller nut 16, and a hollow shaft 4 is arranged on the outer periphery of the shaft 3, moreover the shaft 3 and the hollow shaft 4 are connected and fixed to each other by a connecting rod 5. Journal bearings 7a, 7b are arranged on the upper part and the lower part of the hollow shaft 4 so as to support it, moreover a motor stator 1, a motor rotor 2, a motor stator can 10 and a motor rotor can 11 are provided A thrust disc 9 is connected to the lowermost part of the connecting rod 5, so as to be taken as a receiving part of weight of a rotor part and unbalanced shaft thrust in stopping of pump and also to serve the function as an auxiliary imperller. Thus, the clearance between the motor stator can and the rotor can is provided on the downstream side where discharge liquid of the auxiliary impeller in the motor casing, and pressure of cooling water passing the clearance between two cans is raised, thereby no pressure drop is generated, and also no cavitation and erosion is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a canned motor type pump.

[0002]

2. Description of the Related Art A conventional pump structure of this type is shown in FIG. This pump is used in a nuclear power plant and has the highest radiation level in the power plant, so a non-seal type canned motor is used. An upper journal bearing 7a, a lower journal bearing 7b, and a thrust bearing 8 in which the impeller 6 and the motor rotor 2 are connected to the rear surface of the pump casing 12, and the thrust disk 9 is connected to project the shaft 3 in the liquid.
Pump casing 12, back cover 1 supported by a and 8b
3 is further housed in a casing composed of the motor casing 14. A motor stator can 10 and a motor rotor can 11 are provided to insulate the motor stator 1 and the motor rotor 2 from the pumping liquid.
Clear cooling water is injected from the outside of the motor casing 14 from the lowermost part of the rotor chamber in order to prevent the pumped liquid of highly radioactive and contaminated dust from entering the inside of the motor. The injected cooling water cools the upper thrust bearing 8a, the lower thrust bearing 8b, the upper journal bearing 7a, and the lower journal bearing 7b and flows into the rotor upper chamber, and then the auxiliary impeller 15
Due to this, the structure is forcibly arranged outside the casing and circulated to the heat exchanger 17 having a cooling pipe.

With such a structure, the auxiliary impeller 15
Is installed above the motor stator 1 and the motor rotor 2 and the suction port is directed to the lower side of the rotor chamber, so that the cooling water passing through the two can gap portions of the motor stator 10 and the rotor 11 is Since the suction pressure was low, the structure had a high potential for cavitation.

A related example of this type is JP-A-2-82296.

[0005]

In the prior art described above, the auxiliary impeller 15 is installed above the motor stator 1 and the motor rotor 2 and the suction port is directed to the lower side of the rotor chamber. Two can gap portions, that is, the motor stator 10 and the rotor 11, are arranged in the space.

Therefore, since the cooling water passing through the two can gap portions of the motor stator 10 and the rotor 11 is low in the suction pressure state, cavitation is likely to occur and the erosion causes the motor stator can 10 and the motor rotation. Child can 1
1 had a high potential for damage.

An object of the present invention is to improve the corrosion resistance of the motor stator can and the motor rotor can and to prolong the service life thereof, thereby extending the frequency of regular inspections of the pump and facilitating maintenance and high reliability. To provide a motor type pump.

[0008]

The above object is to mount a rear cover, which has a suction port opened on the upper surface and a shaft to which an impeller is connected, projectingly penetrates to the lower side of the pump casing, and to mount two upper and lower journal bearings. In a canned motor type pump that accommodates a supported canned motor, a motor stator and a motor rotation are achieved by connecting a motor and an auxiliary impeller for circulating bearing cooling water inside a motor casing to a shaft to which the impeller is connected. This is achieved by arranging the gap formed by the child on the downstream side where the discharge liquid of the auxiliary impeller flows.

[0009]

The cooling water injected from the lowermost direction of the rotor chamber or the uppermost direction of the rotor chamber is pressurized by the auxiliary impeller, and after cooling the sliding portions of the upper thrust bearing and the lower journal bearing, the motor stator can is cooled. And through the motor rotor can gap while generating a uniform pressure distribution. Therefore, unlike the conventional structure, by installing the auxiliary impeller on the upstream side of the cooling water flowing in the gap between the motor stator can and the motor rotor can, the cooling water flowing in the gap will not be lowered to the suction pressure state. Moreover, since the pressure drop close to the negative pressure does not occur, cavitation does not occur and the motor stator can and the motor rotor can are not damaged by erosion.

[0010]

1 is a longitudinal sectional view showing an embodiment of the present invention, which will be described below with reference to the drawings.

The pump is a vertical canned motor type pump, and 12 is a pump casing having a suction port opened on the front surface, which is fixed to the foundation. A rear cover 13 is attached to the lower side of the pump casing 12, and the rear cover 13
A shaft 3 to which an impeller 6 is connected is projectingly passed through. The impeller 6 is attached to the shaft 3 by an impeller nut 16.
A hollow shaft 4 is provided on the outer periphery of the shaft 3. The shaft 3 and the hollow shaft 4 are fixed by a connecting rod 5. The hollow shaft 4 has journal bearings 7a and 7b arranged above and below to support it. A motor stator 1 and a motor rotor 2 that transmit power to the impeller 6 are installed on the hollow shaft 4. A motor stator can 10 and a motor rotor can 11 are provided to insulate the motor stator 1 and the motor rotor 2 from the pumped liquid.

In order to receive the weight and unbalanced axial thrust of the rotor parts when the pump is stopped and started, the thrust disk 9 is connected to the lowermost end of the connecting rod 5, and the upper thrust bearing 8a and the lower thrust bearing 8a having a plurality of moving pads are arranged. It is supported by the thrust bearing 8b.

With the above structure, it is not necessary to install the auxiliary impeller 15 having the conventional structure, and the disk-shaped thrust disk 9 which is a component of the thrust bearing can be substituted for the function, so that the motor stator 10 and the rotor 11 can be replaced. Since the pressure drop does not occur by increasing the pressure of the cooling water that passes through the gap between the two cans, cavitation does not occur and the motor stator can 10 and the motor rotor can 11 are not damaged by erosion. is there. The structure of the thrust disk 9 is shown in FIGS.

In this embodiment, the thrust disk 9 has a structure in which the function of the auxiliary impeller 15 is replaced, but the thrust disk 9 and the auxiliary impeller 15 may be separately installed.

FIG. 2 is a longitudinal sectional view of another embodiment, in which a disk-shaped thrust disk 9 which is a thrust bearing component is arranged above the gap between the motor stator can 10 and the motor rotor can 11. In some cases, the suction ports of through holes provided at several circumferential positions in the radial passage are directed toward the back side of the gap. That is, the flow direction of the cooling water pressurized by the thrust disk 9 is arranged on the upstream side of the gap portion, and the same effect as that described in FIG. 1 can be obtained.

FIG. 3 is a longitudinal sectional view of still another embodiment,
A disk-shaped thrust disk 9 which is a component of a thrust bearing is provided with a motor stator can 10 and a motor rotor can 11.
Of the cooling water flowing from the heat exchanger 17 in the case where the suction ports of the through holes which are arranged in the upper part of the gap part and are provided at several circumferential positions in the radial flow path are directed to the lower side of the gap part. Is provided to the suction port of the through hole of the thrust disk 9, and cooling water is directly introduced from there. As a result, the flow direction of the cooling water, which has passed through the through hole of the thrust disk 9 and is pressurized, flows from the upstream side of the gap portion, and the same effect as that described in FIG. 1 can be obtained.

[0017]

The function of the auxiliary impeller is replaced by the auxiliary impeller or a disk-shaped thrust disk which is a component of the thrust bearing, and the motor stator is provided in the motor casing downstream of the auxiliary impeller. Since the can and motor rotor can are arranged so that the cooling water passing through the gap between the two cans is pressurized so that no pressure drop occurs, cavitation does not occur and the motor stator can and the motor rotor The can 11 is not damaged by erosion.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a canned motor type pump of the present invention.

FIG. 2 is a vertical cross-sectional view showing another embodiment of the canned motor type pump of the present invention.

FIG. 3 is a vertical sectional view showing still another embodiment of the canned motor type pump of the present invention.

FIG. 4 is a sectional view of a thrust disk according to the present invention.

5 is a plan view of the thrust disc of FIG. 5. FIG.

FIG. 6 is a vertical sectional view of an example of a conventional canned motor type pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Motor stator, 2 ... Motor rotor, 3 ... Shaft, 4 ... Hollow shaft, 5 ... Connecting rod, 6 ... Impeller, 7a ... Upper journal bearing, 7b ... Lower journal bearing, 8a ... Upper thrust bearing,
8b ... Lower thrust bearing, 9 ... Thrust disk, 10 ...
Motor stator can, 11 ... Motor rotor can, 12
... pump casing, 13 ... rear cover, 14 ... motor casing, 15 ... auxiliary impeller, 16 ... impeller nut,
17 ... Heat exchanger

Claims (1)

[Claims] 1. A cand housing a canned motor which has a suction port opened on the upper surface thereof and a shaft to which an impeller is connected is projectingly penetrated to a lower side of a pump casing, and a canned motor supported by two upper and lower journal bearings. In a motor type pump, an auxiliary impeller for circulating a motor and bearing cooling water is connected inside a motor casing with respect to a shaft to which the impeller is connected, and a gap formed by a motor stator and a motor rotor is formed in the auxiliary vane. A canned motor type pump characterized in that it is arranged on the downstream side where the liquid discharged from the vehicle flows.