JPH06330937A - Bearing wear monitoring device of multi-step submerged pump - Google Patents

Abstract

PURPOSE:To certainly judge chiefly the wear of a rolling bearing of a multi-step submerged motor pump in service which handles a low temp. liquid. CONSTITUTION:A displacement sensor 60 is supported on a bearing housing 18 for a bearing 15 of a multi-step submerged motor pump, and the sensitive surface 61 of this sensor 60 is located as mating with a part of the outside surface of the shaft 13 while a minor gap (e) is reserved in between, and thereupon the gap to the shaft is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a device for monitoring wear of rolling bearings of a multi-stage submerged motor pump used for pressurizing low-temperature liquids such as LNG, LPG, ethylene, propylene and ammonia. Regarding

[0002]

2. Description of the Related Art A pump of this type has, for example, an upper portion formed in a motor portion and a lower portion formed in a pump portion, and is used while being wholly immersed in a handling liquid. The motor portion is provided with a stator, a rotor, a shaft coupled to the rotor, an upper bearing (radial ball bearing) and a lower bearing (radial ball bearing) for supporting the shaft, a pressurized liquid passage, etc. in a motor housing. The motor section is cooled and the bearing is lubricated by a part of the handled liquid pressurized by the pump section. The shaft extends downward as a pump shaft and reaches the lower end of a pump casing connected to the lower end of the motor housing. The pump portion has an impeller in the middle of the pump shaft and a suction port at the lower end of the pump casing. The pump shaft is supported in the pump casing on the casing side via a bush.

Generally, rolling bearings have almost no problem if they are replaced within the calculated life, but ball bearings of this type of pump have a low operating environment,
Since the liquid to be handled is used for lubrication, it is significantly different from the case where a high-performance lubricant is used at room temperature, and it may wear faster than expected, so the life cannot always be calculated accurately. If the wear of the ball bearing is not noticed, the pump may be damaged. For this reason, it is necessary to monitor the ball bearing in this type of pump. Conventionally, in the ball bearing monitoring of this type of pump, a sensor of an acceleration vibrometer is attached to a bearing portion or a pump casing, and the condition of the ball bearing is monitored by the magnitude of the acceleration amplitude. For example, it is determined that there is no abnormality until the detected acceleration is X (a certain value) times the gravitational acceleration, and if it exceeds this, it is determined that there is abnormality, and for example, the work is stopped and the ball bearing is replaced.

[0004]

Since the conventional ball bearing monitoring by the acceleration type vibrometer is designed to detect the vibration of the casing or the bearing portion, the vibration due to the relationship between the bearing and the shaft is not necessarily detected. It does not mean that we are only monitoring the condition of the ball bearings. There are various causes of the detected vibration, and not all the causes are clear. For this reason, there is a problem that it is difficult to determine the difference between the vibration exceeding a certain limit, which is generated due to the progress of wear of the bearing, and the vibration, which is caused by causes other than the wear of the bearing. That is, even when it is determined that the wear of the bearing has reached the limit or more, the wear of the bearing may not be recognized at all. It is an object of the present invention to provide a wear monitoring device capable of more reliably determining wear of a rolling bearing of a multi-stage submerged motor pump as described above.

[0005]

[Means for Solving the Problems] When considering a vertical multi-stage submerged motor pump, a mechanism for balancing the axial thrust generated by the pump is provided. Almost no force is applied. Therefore, since the ball bearing is operated in a state in which only the force in the direction perpendicular to the axis due to the unbalanced force is applied, a large load is not applied in a normal state. Further, although it is expected that a part of the handled liquid will pass through the bearing portion to have a lubricating action, this type of liquid has almost no lubricating action. It is reasonable to think that a ball bearing that operates under such circumstances will follow a different course than the life of a normal ball bearing.

In the normal life of a ball bearing, since the surface pressure at the rolling contact portion is considerably high, fatigue fracture occurs near the surface when operation is continued and peeling occurs, so-called peeling due to rolling fatigue occurs. Considering the total number of revolutions or the operating time. However, the ball bearing of the pump as described above seems to be worn out due to microscopic damage at the contact portion and reach the end of its life.
This is convincing in the fact that no examples of damage due to rolling fatigue are found from the actual usage record of this type of pump.
Therefore, in order to monitor the wear of the rolling bearing of the multi-stage submerged motor pump used for pressurizing such low temperature liquid, it is preferable to mainly monitor the wear condition of the rolling bearing during pump operation. .

According to the means of the present invention, the displacement detector is supported on the bearing housing of the bearing of the multistage submerged motor pump or a portion corresponding to the bearing housing, and the sensing surface thereof is separated from a part of the outer peripheral surface of the shaft with a small gap. It is characterized in that the gap between the shaft and the shaft is measured by facing each other.

[0008]

According to the above-mentioned means, the displacement of the shaft with respect to the bearing housing increases with the progress of wear of the bearing, that is, the amount of whirling of the shaft increases, so that the pump operation measured by the displacement detector is increased. The gap between the predetermined position outside the inner shaft and the shaft surface has a larger maximum value and a smaller minimum value. If the limit value of wear is appropriately determined in advance with respect to the maximum value or the minimum value of the gap size, it will be within the wear limit until it exceeds a certain maximum value or the minimum value, and when it exceeds that value. It can be determined that the bearing life has been reached.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.
FIG. 2 shows a multi-stage submerged motor pump provided with the rolling bearing wear monitoring device of this embodiment. In the figure,
1 is a motor part, 2 is a pump part. The motor unit 1 includes a stator 11, a rotor 12, a shaft 13 coupled to the rotor, and an upper bearing 1 supporting the shaft 13 in a motor housing 10.
4, the lower bearing 15, the pressurized liquid passage 16 and the like are provided. The motor unit 1 cools the motor unit by a part of the handling liquid pressurized by the pump unit 2 and the bearing 1
Lubrication 4 and 15 are performed. Bearing 1
Reference numerals 4 and 15 are radial ball bearings. 5 in the figure
Reference numeral 1 is a power supply line, 17 is a balance drum, and 18 is a lower bearing housing.

The pump portion 2 is a pump casing 20 connected to the lower end of the motor housing 10, and the casing 2 thereof.
Zero diffuser 21, impeller 22, above shaft 13
Shaft 2 extending downward from the casing 2, casing 2
It has a suction port 24 formed at the lower end of 0, an inducer 25 provided at the suction port 24, and the like. The impeller 22 is attached to the pump shaft 23,
The inducer 25 is an axial flow impeller attached to the lower end of the pump shaft, and the pump shaft 23 is supported on the casing 20 side via a bush 26. The outlet 27 of the pump unit 2 is connected to the lower end of the liquid passage 16 of the motor unit 1.

This multistage submerged motor pump is
For example, as shown in the figure, it is installed in the vicinity of the tank in combination with the pot 40 and is used when the low temperature liquid in the tank is transferred to another place. This pot 40
Is installed in a pit and is filled with a heat insulating material on the outside thereof, and the inside is connected to a tank containing the liquid to be handled through an inlet 41 and a gas vent 42.
It is designed to flow into 0. Therefore, the motor unit 1
And the pump part 2 is used in a state where the whole is immersed in the handling liquid. Reference numeral 50 in FIG. 1 is a discharge port that communicates with the liquid passage 16, and is connected with a transfer pipe. 43 is a pot support leg, 44 is a drain. The arrow in the figure indicates the moving direction of the handled liquid.

When the pump shaft 23 is rotationally driven by the motor unit 1, the liquid to be handled flowing into the pot 40 is pressurized while passing through the suction port 24 to the outlet 27 of the pump unit 2 and the passage 16 Through the discharge port 50. Bearing wear monitoring devices are provided for the ball bearings 14 and 15 of this pump. FIG. 1 shows a state in which the displacement detector 60 of the bearing wear monitoring device is attached to the bearing housing 18. The displacement detector 60 is of the inductance bridge type, and the gap dimension between the sensing surface 60a and the outer peripheral surface of the shaft 18 is shown. e can be detected in the range of 0 to 1.3 mm. In the figure, reference numeral 61 denotes a detector cable, which is insulated and coated with fluororesin. Although the drawing shows one provided for the lower bearing 15, a displacement detector 60 is similarly provided for the upper bearing 14. The amount of displacement detected by processing the signal obtained from the displacement detector 60 with a microcomputer is continuously displayed on an appropriate display device, and an appropriate limit value is set by paying attention to the maximum value or the minimum value thereof. When the limit value is exceeded, a warning sound is emitted and the warning lamp is turned on.

According to this bearing monitoring device, as the wear of the ball bearings 14 or 15 progresses during use of the pump, the whirling amount of the shaft 3 increases, so that the maximum value of the gap dimension e continuously detected is When the value becomes larger and the minimum value becomes smaller, and the value exceeds a preset limit value, an alarm sound is emitted and the alarm lamp lights up. This alarm allows the worker to reliably determine that the bearing 14 or 15 is worn and take appropriate action.

In the above embodiment, the bearings 14 and 15 are ball bearings, but in the case of a metal bearing other than the rolling bearing, the progress of wear can be known even when applied to the bush 26 in FIG. Further, in the embodiment, one bearing is provided with one displacement detector, but the shaft may swing around in an elliptical shape depending on the wear condition of the bearing. Two detectors may be provided so that the displacement of the shaft in the x-axis direction and the displacement of the shaft in the y-axis direction can be separately detected in correspondence with the x-y axes, and in some cases, two bearings are provided. On the other hand, the upper bearing may be provided with one detector for detecting the displacement in the x-axis direction, and the lower bearing may be provided with one detector for detecting the displacement in the y-axis direction. Good. As a result, it becomes possible to more surely grasp the wear condition of the bearing.

[0015]

According to the present invention, the wear condition of a rolling bearing, which is a multi-stage submerged motor pump that handles low-temperature liquids and is used under special circumstances, is compared with the conventional one in which wear is detected by simple vibration. A bearing monitoring device that can be grasped more accurately can be provided. Therefore, there is an effect that the pump of this kind can be efficiently operated without stopping the pump due to an erroneous determination.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a main part of an embodiment of the present invention.

FIG. 2 is a vertical sectional front view of a pump to which the embodiment is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor part 2 Pump part 13 Motor shaft (shaft) 14 Bearing (ball bearing) 15 Bearing (ball bearing) 18 Bearing housing 22 Impeller 23 Pump shaft (shaft) 60 Displacement detector 60a Sensing surface e Gap

Claims (1)

[Claims] 1. A displacement detector is supported on a bearing housing of a bearing of a multi-stage submerged motor pump or a portion corresponding to the bearing housing, and a sensing surface thereof is opposed to a part of an outer peripheral surface of a shaft with a small gap. A bearing wear monitoring device for a multi-stage submerged pump, characterized in that a gap between the shaft and the shaft is measured.