JPH06100198B2 - Pump life prediction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for predicting the life of a pump, and more particularly to a method for predicting the life of an inducer or impeller by measuring the vibration acceleration and the number of vibrations of the pump. The present invention relates to a life prediction method.

[Prior Art] When cavitation occurs in a pump that sucks liquid from a tank or the like, the lift, shaft power, efficiency, etc. are drastically reduced, resulting in noise and vibration. In addition, surrounding materials such as the inducer and impeller are invaded by erosion.

Therefore, a technique has been developed in which an acceleration sensor or an ultrasonic sensor is provided in the casing of the pump, the vibration of the casing and the sound of bubbles in the casing are monitored by these sensors, and cavitation is avoided (JP-A-61-244896).
JP-A-61-244897, etc.).

According to these techniques, it is determined that cavitation occurs when vibration or bubble noise suddenly increases, and the inflow valve of the pump is opened or the rotation speed of the impeller is reduced. As a result, even if cavitation occurs once, it can be quickly returned to the normal operating state.

[Problems to be Solved by the Invention] However, these prior arts prevent the cavitation from occurring singly, and are accumulated in the inducer and the impeller by the erosion generated in the inducer and the impeller for each cavitation. It is not possible to grasp the state of the erosion that is formed.

Therefore, if the inducer or impeller is cumulatively eroded by erosion during past cavitation and reaches the limit of mechanical strength, it will be suddenly damaged by the next cavitation, making it difficult to predict the pump life. It was

An object of the present invention devised in view of the above circumstances is to provide a pump life predicting method capable of accurately predicting the life of an inducer or impeller.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an acceleration sensor in the vicinity of a portion of a pump where cavitation is likely to occur, and sets the intensity and the number of times of cavitation due to acceleration detected by the acceleration sensor. This is a method of predicting the life of a pump, in which it is determined that the pump has reached the end of its life when the integrated value exceeds a predetermined value.

[Operation] When cavitation occurs in the pump, the inducer and impeller are eroded by erosion. The present inventor has found that the amount of erosion due to this erosion (erosion depth and area) is correlated with the integrated value of the cavitation intensity and the number of times.

This is because each time cavitation occurs, the inducer or impeller undergoes erosion according to its cavitation intensity, and the inducer or impeller is cumulatively eroded every number of times of erosion, that is, every cavitation.

The present invention has been made paying attention to this point, and integrates the intensity and the number of times of cavitation due to acceleration, and when the integrated value exceeds a predetermined value, the inducer or impeller has reached the end of its life. This is to determine that the pump has reached the end of its life.

[Embodiment] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, first, an acceleration sensor 1 that can detect the occurrence of cavitation is attached in the vicinity of a portion of the data acquisition pump 2 where cavitation is likely to occur. In this embodiment, the acceleration sensor 1 is attached to the casing 4 near the suction port 3 of the pump 2.

Cavitation occurs when, for example, the liquid level of a fluid source such as a tank (not shown) decreases or the flow rate introduced into the pump 2 decreases. This is shown in FIGS. 2 and 3. As shown in FIG. 2, the vibration acceleration v increases when the liquid level 1 decreases. Further, as shown in FIG. 3, when the flow rate f decreases, the vibration acceleration v also increases. Therefore, the strength of cavitation that occurs when the liquid level 1 and the flow rate f decrease can be grasped by the degree of increase in the vibration acceleration v detected by the acceleration sensor 1.

The vibration acceleration v detected by the acceleration sensor 1 can be expressed as shown in FIG. 4 in relation to the driving time t. As shown, the vibration acceleration v of cavitation appears as a peak of a wave. The height h of the peak of this wave is the intensity of cavitation. In addition, the number of times the vibration acceleration increases in a predetermined operation time t, that is, the number of times the wave peak appears is the number of cavitation times n.
Is.

Then, the data acquisition pump 2 is actually operated, and the product of the intensity h of the vibration acceleration v and the number of times n when the cavitation detected by the sensor 1 occurs is cumulatively integrated. In parallel with this, the erosion amount (erosion depth and area) due to the erosion actually generated in the inducer 5 and the impeller 6 of the data acquisition pump 2 at arbitrary integrated values is measured at a plurality of points.

This erosion amount is preferably measured until the inducer 5 and the impeller 6 are mechanically damaged, but it is not always necessary to measure until the inducer 5 or the like is damaged, and even if it is stopped by several measurements, it is damaged. You may stop before. In that case,
The plot points are connected by a straight line or a curved line, and the tip end thereof is extended to an erosion amount at which the inducer 5 and the impeller 6 will be mechanically damaged.

The integrated value and the erosion amount (erosion depth and area) have a correlation. Because every time cavitation occurs,
This is because erosion occurs in the inducer 5 and the impeller 6 according to the cavitation strength, and the inducer 5 and the impeller 6 are cumulatively eroded for each number of erosion, that is, for each cavitation.

In consideration of this fact, correlation data in which the integrated value obtained by the data collecting pump 2 and the erosion amount are associated with each other is created in advance. Specifically, as this correlation data, for example, the integrated value is taken on the horizontal axis and the erosion depth or erosion area is taken on the vertical axis. This correlation data becomes a curve on the upper right, and is broken when the inducer 5 and the impeller 6 are damaged.

On the other hand, similarly to the pump 2 for data acquisition shown in FIG. 1, an acceleration sensor 1 capable of detecting the occurrence of cavitation is attached to a casing 4 near the suction port 3 of the pump 2 in the pump 2 whose life is to be measured. ing. It goes without saying that the pump 2 whose life is to be measured is of the same type as the data acquisition pump 2. Therefore, those drawings are
Share in the figure. The acceleration sensor 1 attached to the pump 2 whose life is to be measured cumulatively integrates the product of the intensity h of the vibration acceleration v when cavitation occurs and the number of times n.

The pump 2 whose life is to be measured is the data acquisition pump 2 described above.
It may be a new pump other than the above, or may be the data acquisition pump 2 itself. That is, when the erosion amount is measured by the data collecting pump 2 until the inducer 5 and the impeller 6 are mechanically damaged, the data collecting pump 2 and the pump 2 whose life is to be measured are different from each other. Become a pump. On the other hand, the measurement of the erosion amount is stopped before the data acquisition pump 2 is broken, the past measurement points are connected by a straight line or a curved line, and the tip of the measurement point may mechanically damage the inducer 5 or the impeller 6. In the case of extension to the above, the data acquisition pump 2 itself may be used as the pump 2 whose life is to be measured thereafter.

Next, the operation of the above embodiment will be described.

Since the acceleration sensor 1 attached to the pump 2 whose life is to be measured is located in the casing 4 in the vicinity of the suction port 3 of the pump 2, it does not detect other vibrations such as a shake of the bearing, and the cavitation Accurately detect inception.

The acceleration sensor 1 cumulatively integrates the product of the intensity h of the vibration acceleration v when cavitation occurs and the number n. Then, the integrated value is applied to the horizontal axis of the above-mentioned correlation data obtained by the data acquisition pump 2, and the erosion caused by the erosion that may occur in the inducer 5 or the impeller 6 of the pump 2 whose life should be measured. Estimate depth and area. Thus, the life of the inducer 5 and the impeller 6 can be accurately predicted, and the life of the pump 2 whose life should be measured can be determined.

When it is predicted that the integrated value will increase and the erosion depth and area due to erosion will increase,
There are three possibilities: First, when the cavitation strength h is large and the number of times n is large, the second cavitation strength h is very large, and when the number of times n is slightly small, third, the cavitation strength h is slightly small, This is the case when the number of times n is very large. Therefore, the present embodiment estimates the life of the pump in consideration of these points.

By the way, when predicting the service life based on the above correlation data, if the data acquisition pump 2 and the pump 2 whose service life is to be predicted are different pumps, the vibration acceleration v in the initial state of each pump 2 whose service life is to be predicted is It is necessary to measure. This is because the strength of the vibration acceleration v in the initial state of each pump 2 differs depending on the operating condition thereof, and therefore it is necessary to determine the reference plane that is the rise of the cavitation strength h shown in FIG.

[Effects of the Invention] In short, according to the present invention, it is possible to exert an excellent effect that the life of the inducer of the pump and the life of the impeller can be accurately predicted.

[Brief description of drawings]

FIG. 1 is a side sectional view of a main part of a pump adopted for carrying out the method of the present invention, FIG. 2 is a graph showing a relationship between acceleration and liquid level, and FIG. 3 is a graph showing a relationship between acceleration and flow rate. FIG. 4 is a graph showing the relationship between acceleration and driving time. In the figure, 1 is an acceleration sensor, 2 is a pump, 5 is an inducer, 6 is an impeller, h is the strength of cavitation, and n is the number of times of cavitation.

Claims (1)

[Claims] 1. When an acceleration sensor is attached in the vicinity of a portion of a pump where cavitation is likely to occur, the cavitation intensity and the number of times of acceleration detected by the acceleration sensor are integrated, and the integrated value exceeds a predetermined value. In addition, a method of predicting the life of a pump that determines that the pump has reached the end of its life.