JPS5854270B2 - Method for detecting erosion position by cavitation in hydraulic machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the position of erosion due to cavitation in a hydraulic machine.

Conventionally, this type of method includes a direct detection method and an indirect detection method.

Direct detection methods include (I) a method in which an actual machine or a model machine made of the same material as the actual machine is operated for a long period of time to investigate the state of erosion occurrence;

(It) A method of operating a model machine made of materials that are more susceptible to erosion than the actual machine for a relatively short period of time to investigate the occurrence of erosion.

(A method in which paint is applied to the metal surface of an actual IIO machine or a model machine, the machine is operated for a very short period of time, and the state of corrosion is investigated from the peeling of the paint.

and so on.

However, although method (I) is the most accurate testing method, it requires an extremely long time and is extremely expensive.

Further, in the method (If) above, although the time required for the test is short, it is necessary to manufacture test specimens made of different materials, and the cost required for the test is considerable.

Furthermore, in the method (ml) above, the above (I)
This is a simple method that requires much less time and expense than method (II), but in order to improve test accuracy, it is necessary to keep coating conditions such as coating thickness and hardness constant. However, it is particularly difficult to apply paint on actual machines.

Further, as indirect detection methods, there are detection methods using ultrasonic waves, vibration acceleration, etc., but the accuracy is not sufficient and it is necessary to verify by a direct detection method.

The purpose of this invention is to eliminate the above-mentioned drawbacks of the prior art, and it involves attaching a film that develops or changes color due to pressure changes to the metal surface of a hydraulic machine, thereby preventing damage caused by cavitation caused by the operation of the hydraulic machine. The present invention is characterized in that the eclipse position is detected based on the state of color development or discoloration of the film.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

In FIGS. 1 and 2, a film 1 is composed of a carbon paper or a film 2 soaked in a coloring material, a white thin paper 3 placed on top of the film 2, and a base film 4 and a cover film 5 covering the film 2.

The base film 4 and the cover film 5 are made of a water-resistant material such as polyvinyl chloride, and their joint surfaces are adhered by pressurization or the like.

Further, it is desirable that the cover film 5 is transparent.

As shown in FIG. 2, the film 1 constructed as described above has
When a local pressure P acts on the film 2, the film 2 is locally distorted and the beam material contained therein stains the white thin paper 3 on the upper layer.

As shown in FIG. 3, the film 1 is pasted on the surface of the blades 7 of the pump impeller 6, and the pump is operated to generate cavitation 8.
When the film 2 collapses, colored pressure marks are created on the white thin paper 3 at the locations exposed to the collapse pressure due to dyeing from the film 2.

Normally, the impact pressure when cavitation collapses is several thousand to
It is said that the pressure reaches several hundred atmospheres, and other pressure changes due to changes in water flow are about several tens of atmospheres, so the film 2 should be adjusted so that it is sensitive only to pressures of several hundred atmospheres or more. , pressure marks caused by the water flow do not appear, and only pressure marks caused by the impact pressure at the time of cavitation collapse can be detected.

Note that the magnitude of the pressure can be estimated by verifying the degree of staining of the beam material with respect to the pressure acting on the film 2.

Further, instead of the coloring means using the film 2 and the white thin paper 3, pressure sensitive paper can also be used.

As explained above, according to the present invention, the following remarkable effects can be obtained.

(I) The location and strength of erosion caused by cavitation can be detected, and preventive measures can be considered.

(II) The test is extremely simple and can be conducted in a short time.

(Curved film is extremely easy to produce and can be made to have a uniform thickness, which improves test accuracy.

Films after sub-operation can be saved as test results.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional front view of the film, Figure 2 is a cross-sectional front view explaining the case where pressure is applied to the film, and Figure 3 is a film attached to a pump blade to detect the location of erosion caused by cavitation. FIG. 2...Film, 3...White thin paper, 4
...Base film, 5...Cover film.

Claims (1)

[Claims] 1. A film that develops or changes color due to pressure changes is attached to the metal surface of the hydraulic machine, and the location of erosion due to cavitation caused by the operation of the hydraulic machine is detected based on the state of color development or discoloration of the film. Method for detecting erosion position by cavitation in hydraulic machinery.