JP2986964B2 - Piping member damage detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting damage to various piping members existing in a primary cooling system, a main steam system, etc. of a light water reactor, for example.

[0002]

2. Description of the Related Art In general, a conventional piping system is designed by connecting a container and a specialty device as a piping member by piping, a nozzle, an elbow, or the like.
Usually, there are many cases in which these devices are constituted by welding in addition to mechanical connection such as fitting and screwing. These parts are subjected to various inspections based on the inspection method determined at the time of periodic inspections, etc., and are to be repaired or replaced when deterioration or functional deterioration is recognized.

[0003]

SUMMARY OF THE INVENTION In a conventional structure,
Visual inspection, ultrasonic wave, radiation inspection, and the like around the welded portion are performed, but the conventional technology does not always have sufficient detection accuracy. In addition, piping members in such a high-temperature plant are generally used in an environment that is considerably severer than the use conditions in the air, such as high temperature, corrosion, abrasion, and water.
Taking fatigue damage as an example of failure in such a place,
Conventional technology makes it difficult to detect clear signs from the beginning, and is a part that needs further development from the viewpoint of preventive maintenance.
Further, at present, there is a problem that the inspection itself is difficult for small-diameter pipes.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. At the same time, the present invention adopts a method of manufacturing a piping member in operation of a plant in consideration of the detection of damage from the time of manufacture to a period of common use. An object of the present invention is to provide a method for detecting damage to a piping member, which can be used as a system capable of evaluating damage accumulated in the piping member.

[0005]

According to the present invention, a small marker capable of detecting a change in the relative position of each point by an optical detecting means at the time of manufacture is periodically attached to a pipe member at several locations in a circumferential direction. After the piping member is installed in the plant and during plant operation, the change in the position of the marker is processed by the optical detection means to detect locally generated distortion, and based on a plurality of measured values, It is characterized by measuring the overall deformation and the applied load and calculating the measured values to detect the accumulated fatigue damage due to the variable load.

[0006]

A minute marker capable of detecting local distortion of each part is arranged by using a method which does not affect the basic strength when manufacturing various piping members. At this time, between these markers, (1) a triangular arrangement for calculating the local minute strain from the displacement of each point is performed. (2) orthogonal 2 for each marker group
A marker arrangement for measuring directional distortion is used. (3) Markers are arranged at least at intervals of 90 ° in the circumferential direction in order to analyze the entire deformation. These three requirements must be met. By measuring the relative positions of these markers with a detection device such as an image fiber, it is possible to determine the minute strain on the surface and the load applied to the entire member. The minute markers arranged at equal intervals installed at the time of manufacture change their intervals according to the loads applied to the members during plant installation and plant operation. By measuring the relative position of the marker with the changed interval, the direction component of the locally generated surface distortion is detected. Thereafter, based on the measured values of the strains at several points in the circumferential direction, the moment component acting on the entire pipe or the axial direction can be converted. Based on this load value, the distribution of stress / strain generated in the piping member is calculated, and it is possible to estimate a location where the damage value is large in the entire structure. Also,
Accumulation of fatigue damage can be detected by taking into account the calculated fluctuating stress and strain.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for detecting damage to a piping member according to the present invention will be described with reference to the drawings.

FIG. 1 shows the structure of a piping member used in the present invention and a diagram of a detection system. The present invention is an example in which four sets of markers 2 are installed in the vertical and 90 ° directions at the same axial position of the pipe member 1. These markers need to be arranged at a very precise precision at the time of manufacture. Further, as a sensor for detecting and calculating these markers 2, an optical detection device 11 usually composed of a TV camera or an image fiber is required. Further, an image processing device 12 for digitizing the obtained image and an arithmetic device 13 for processing the obtained numerical data to detect the damage applied are required. FIG. 2 shows an example in which an indentation type marker 3 is used as an example of the marker group. The indentation type markers 3 arranged in a triangle are arranged in four directions around the center, and the distortion in each direction can be calculated. Since each indentation type marker 3 having a size of about the Vickers indenter and a depth and an interval of about 100 microns is sufficient, the strength originally possessed by the pipe member 1 is hardly affected. FIG. 3 shows the top surface and cross section of each indentation type marker 3. When such a manufacturing marker 20 that is regularly installed is deformed by applying a load from outside during installation and operation, the interval between the markers 21 during use changes as shown by a dotted line in FIG. At that time, from the relative displacements of the three points detected by optical means, applying the principle of triangulation, the averaged surface distortion in this area was calculated using the interpolation function used in the finite element method, etc. Can be detected. However, if this is the only case, it becomes impossible to detect when a peak of damage occurs in a portion where there is no indentation type marker 3. Therefore, by continuously collecting strains in the two orthogonal directions at each marker group obtained in this manner, the strain distribution at each point arranged in the circumferential direction of the pipe member is measured. Further, by disposing these indentation type markers 3 at appropriate intervals in the axial direction, it is possible to obtain a strain distribution in the axial direction. By combining these values and using some powerful calculation results,
It is possible to know what kind of load is applied locally as piping. As a result, the peak position and the magnitude of the stress / strain of the pipe member 1 can be calculated. By performing this measurement continuously, the fluctuation range of the displacement of the indentation type marker can be measured, and thus, fatigue damage accumulated in the material due to stress fluctuation can be detected at any place, and the piping member can be detected. It is possible to detect strength deterioration.

The present invention is not limited to the above embodiment, but can be applied not only to piping but also to nozzles and elbows. Further, in addition to mechanical markers such as Vickers indentations used in this embodiment as marker types, chemical markers such as photoresist etching and ion implantation of colored elements used in semiconductors are used. Things can also be used.

[0010]

According to the present invention, deterioration damage during the operation of a high-temperature plant can be detected relatively easily and early with respect to the entire piping system of a nuclear reactor system. Effective for improvement.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing a structure of a piping member applied to an embodiment of the present invention and a detection system thereof.

FIG. 2 is a configuration diagram showing an indentation type marker group used in the embodiment in FIG.

FIG. 3 is a conceptual diagram showing an upper surface and a cross section of an indentation type marker in FIG. 2;

FIG. 4 is a deformed state comparison diagram showing a marker under load of the embodiment in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piping member, 2 ... Detection marker, 3 ... Indentation type marker,
11: Optical detection device, 12: Image processing device, 20: Manufacturing marker, 21: Load-loaded marker.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/88 G01B 11/16 G01S 11/12 G01N 3/00

Claims (1)

(57) [Claims] 1. A small marker capable of detecting a relative position change of each point by an optical detection means at the time of manufacture is periodically attached to a pipe member at several locations in a circumferential direction, and after the pipe member is installed in a plant. And processing the change in the position of the marker by optical detection means during plant operation to detect locally generated distortion, and measure the overall deformation and applied load of the piping member based on a plurality of measurement values. A method for detecting damage to a pipe member, comprising calculating a measured value to detect cumulative fatigue damage due to a fluctuating load.