Method and device for estimating wall thinning of piping components

Abstract

To provide a non-destructive inspection method which allows for easily and inexpensively estimating thinning and installation states of synthetic resin piping members.SOLUTION: A deterioration estimation method provided herein uses a measurement device comprising a striking hammer 13 and an acceleration sensor 17 attached to the striking hammer 13 and comprises striking a surface of a synthetic resin piping member P using the striking hammer 13, temporally measuring acceleration of the striking hammer 13 using the acceleration sensor 17, and estimating whether the thickness of the piping member P is less than a predetermined value or not on the basis of the measured acceleration of the striking hammer 13 to estimate thinning of the piping member P.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for estimating wall-thinning of a piping member, which estimate wall-thinning of a piping member made of synthetic resin. [Background technology]

[0002] As a non-destructive inspection method for piping components of a piping system, various methods according to purpose have been known so far, such as visual inspection (visual inspection, visual method) and percussion inspection (percussion inspection, percussion method). Visual inspection is a method to visually check the surface condition and defects of piping components, such as cracks, peeling, and connection failures. Changes such as discoloration that appear on the surface of piping components may indicate abnormalities during use, and phenomena that occur on the surface of piping components can be detected with high sensitivity. However, visual inspection only observes changes on the surface of piping components, and cannot observe defects such as connection failures and thinning (reduction in wall thickness) inside piping components in a non-destructive manner. In addition, percussion inspection is a method in which an operator strikes the object to be inspected with a hammer and judges the presence or absence of defects such as deterioration and thinning based on the sound and vibration at that time. However, the operator needs experience to make a judgment, and since it depends on the operator's sense, there are problems in that quantification is difficult and objectivity is lacking.

[0003] In order to solve the above problems, ultrasonic thickness measurement, radiographic testing, and the like have been conventionally used as non-destructive testing methods for inspecting defects such as thinning (reduction in wall thickness) of piping components and poor connections between piping components. These methods aim to know the existence, location, and approximate size of defects inside piping components. In addition, as described in Patent Documents 1, 2, and 3, in impact investigations, there have been proposed inspection devices, diagnostic devices, and diagnostic methods that measure the results of impacts with a hammer and quantify them as objective data. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-280779 [Patent Document 2] JP 2002-257700 A [Patent Document 3] JP 2000-131292 A Summary of the Invention [Problem to be solved by the invention]

[0005] The ultrasonic thickness measurement and radiography test described above are not problematic when the thinned parts of the piping components, the parts with poor construction, etc. are known in advance. However, when inspecting the entire piping system to identify the diagnosis parts, ultrasonic thickness measurement not only requires a long inspection time, but also requires a lot of inspection costs. Furthermore, radiography tests have the problem that the inspection equipment is expensive, there is a risk of radiation, and it is difficult to inspect for a long time.

[0006] In addition, in the impact investigation, Patent Document 1, which discloses a non-destructive inspection device, specifies only the exterior wall of a building as the object to be inspected, and Patent Document 2 relates to a wood deterioration diagnostic device and a wood deterioration diagnostic method. Furthermore, Patent Document 3 discloses a pipe inspection device that inspects the corrosion state of pipes that use metal pipes. Thus, none of Patent Documents 1 to 3 discloses the inspection of thinning or poor construction of synthetic resin pipes.

[0007] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a non-destructive inspection method capable of easily and inexpensively estimating the thinning and installation state of synthetic resin piping components in order to solve the problems present in the prior art. [Means for solving the problem]

[0008] In view of the above object, the present invention provides, as a first aspect, a method for estimating wall thinning of a synthetic resin piping component, using a measuring device including an impact hammer and an acceleration sensor attached to the impact hammer, the method comprising: striking a surface of the synthetic resin piping component with the impact hammer; measuring the acceleration of the impact hammer over time with the acceleration sensor; and and calculating at least one of a mechanical impedance ZR during the rebound process in which the impact hammer rebounds from the surface of the piping component in the opposite direction to the direction in which the impact hammer impacts the surface of the piping component, and an index I which is a ratio between a collision speed Va when the impact hammer impacts the surface of the piping component and a rebound speed Vr when the impact hammer rebounds from the surface of the piping component, and based on at least one of the calculated mechanical impedance ZR and index I, Estimating whether the wall thickness of the piping member is below a predetermined value The impact velocity Va is calculated by integrating the measured acceleration over time from 0 to a maximum value, the rebound velocity Vr is calculated by integrating the measured acceleration over time from the maximum value to a time from the maximum value to a time from the maximum value to a time from the maximum value to the maximum value to the maximum value to the maximum value to the maximum value max When the acceleration sensor is used to measure the mass of the impact hammer, F max is calculated, and the mechanical impedance ZR is expressed by the formula ZR=F max / Vr, and the index I is calculated by the formula I=Va / Vr. Threshold values ​​are respectively set in advance for the mechanical impedance ZR and the index I. When at least one of the mechanical impedance ZR and the index I obtained by measurement is lower than the respective predetermined threshold values ​​of the mechanical impedance ZR and the index I, it is estimated that the thickness of the piping member is lower than the predetermined value. A method for estimating thinning of a piping component is provided.

[0009] In the method for estimating wall-thinning of a piping member, an impact hammer equipped with an acceleration sensor is used to strike the surface of a piping member made of synthetic resin with the impact hammer, thereby estimating whether the wall thickness of the piping member is below a predetermined value. The impact of the impact hammer on the surface of the piping member is roughly divided into a penetration process in which the impact hammer collides with the surface of the piping member and the piping member is deformed by the force from the impact hammer, and a repulsion process in which the impact hammer is pushed out in the opposite direction to the striking direction by the repulsive force from the piping member accompanying the restoration from the deformation when the deformation of the piping member is maximized, and is separated from the surface of the piping member. The present inventor has found that the wall thickness of the piping member affects the acceleration of the impact hammer when the piping member is restored from the deformation after being struck by the impact hammer, i.e., in the repulsion process. Using this knowledge, the method for estimating wall-thinning of a piping member estimates the reduction in the wall thickness of the piping member, i.e., the wall-thinning (specifically, the amount of wall-thinning or the wall-thinning rate) (i.e., the wall-thinning amount or the wall-thinning rate) (i.e., the wall-thinning amount or the wall-thinning rate) (i.e., the wall-thinning rate ... Here, the thickness of the piping member means the thickness of the peripheral wall of the piping member, and in the joint of two piping members where one piping member is inserted into the other piping member, it means the sum of the thickness of the peripheral wall of one piping member in the region where the two piping members overlap and are integrated and the thickness of the peripheral wall of the other piping member. In the case of a joint failure such as when a gap is formed between the two piping members at the joint, it means the thickness of the peripheral wall of only the piping member on the side where the impact is applied. Therefore, in addition to the thinning of the piping member due to wear and erosion, the above-mentioned method for estimating the thinning of the piping member can also find a connection failure where a gap is formed between the two piping members at the joint where one piping member is inserted into the other piping member and the two piping members are not integrated. In addition, the amount of thinning means the amount of thinning compared to the thickness of an unused product, and the thinning rate means the ratio of the amount of thinning to the thickness of an unused product.

[0011] The impact velocity Va is calculated by integrating the acceleration of the impact hammer during the penetration process from 0 to the maximum value, and the rebound acceleration Vr is calculated by integrating the acceleration of the impact hammer during the rebound process from the maximum value to 0. The maximum impact force F generated when the impact hammer collides with the surface of the piping component is calculated by integrating the acceleration of the impact hammer during the rebound process from the maximum value to 0. maxis the mass force m and maximum acceleration a of the striking hammer max It is calculated as the product of ZR and F. max If the value obtained by / Vr is the mechanical impedance ZR in the rebound process, and the ratio of the impact speed Va to the rebound speed Vr is the index I, then both the mechanical impedance ZR and the index I include the rebound speed Vr, and the reduction in the wall thickness of the piping component should be reflected in the mechanical impedance ZR and the index I. From this prediction, the inventor has found that the thinning of the piping component whose wall thickness falls below a predetermined value or the defective connection can be estimated based on the mechanical impedance ZR in the rebound process and the index I. Using this knowledge, the above-mentioned method for estimating wall thickness reduction of a piping component estimates whether the wall thickness of the piping component falls below a predetermined value based on at least one of the mechanical impedance ZR in the rebound process and the index I.

[0013] before When both the mechanical impedance ZR and the index I obtained by measurement are lower than their respective predetermined threshold values, it may be estimated that there is a higher probability that the thickness of the piping component is lower than a predetermined value.

[0014] It is preferable that thresholds are previously determined for the mechanical impedance ZR and the index I for each nominal diameter and material of the synthetic resin piping member, and that the previously determined thresholds for the mechanical impedance ZR and the index I corresponding to the nominal diameter and material of the piping member to be measured are compared with the mechanical impedance ZR and the index I determined by measurement to estimate whether the wall thickness of the piping member is below a previously determined value. By determining thresholds for the mechanical impedance ZR and the index I for each nominal diameter and material of the piping member, it is possible to further increase the accuracy of estimating the reduction in the wall thickness of the piping member, i.e., the thinning.

[0015] The thickness of the piping member is the sum of the thickness of the first piping member and the thickness of the second piping member at the joint where the second piping member is inserted into the first piping member, and it can be estimated that a gap is formed between the first piping member and the second piping member when at least one of the mechanical impedance ZR and the index I obtained by measurement is lower than a predetermined threshold value for each of the mechanical impedance ZR and the index I.

[0016] Furthermore, it is preferable to previously determine a correlation between temperature and the mechanical impedance ZR and the index I, temperature-compensate the mechanical impedance ZR and the index I determined by measurement based on the previously determined correlation and the temperature at the time of measurement, and estimate whether the wall thickness of the piping member is below a predetermined value based on at least one of the temperature-compensated mechanical impedance ZR' and the index I'. By taking into account the effect of the temperature at the time of measurement, it is possible to further improve the accuracy of estimating the reduction in the wall thickness of the piping member, i.e., the thinning.

[0017] In addition, as a second aspect, the present invention provides a piping component wall-thinning estimation device for estimating wall-thinning of a synthetic resin piping component, the device including: an impact hammer for striking a surface of a synthetic resin piping component; an acceleration sensor attached to the impact hammer; a measurement value storage unit that stores, over time, accelerations of the impact hammer measured by the acceleration sensor; and a wall-thinning estimation unit that estimates whether or not the wall-thinning of the piping component is below a predetermined value based on the accelerations stored in the measurement value storage unit. a threshold value storage unit that stores predetermined threshold values ​​for the mechanical impedance ZR and the index I for each nominal diameter and material of the piping member; Equipped with The wall-thinning estimation unit obtains, from the acceleration stored in the measurement value storage unit, at least one of a mechanical impedance ZR during a rebound process in which the impact hammer rebounds from the surface of the piping component in a direction opposite to the direction in which the impact hammer impacts the surface of the piping component, and an index I calculated by the equation I=Va / Vr from the impact velocity Va when the impact hammer impacts the surface of the piping component and the rebound velocity Vr when the impact hammer rebounds from the surface of the piping component, and obtains predetermined threshold values ​​for each of the mechanical impedance ZR and the index I corresponding to the nominal diameter and material of the piping component to be measured. When at least one of the mechanical impedance ZR and the index I obtained by measurement falls below a predetermined value, it is estimated that the thickness of the piping component falls below a predetermined value, the collision velocity Va is calculated by integrating the acceleration stored in the measurement value storage unit over a time period from 0 to a maximum value, the rebound velocity Vr is calculated by integrating the acceleration stored in the measurement value storage unit over a time period from the maximum value to a time period from the maximum value to 0 again, and the maximum value of the impact force generated when the striking hammer collides with the surface of the piping component is determined as F. max When the mass of the impact hammer and the acceleration of the impact hammer stored in the measurement value storage unit are used, F max is calculated, and the mechanical impedance ZR is calculated according to the formula ZR=F max / Vr A piping component thinning estimation device is provided.

[0018] As with the above-mentioned piping component wall-thinning estimation method, the above-mentioned piping component wall-thinning estimation device can estimate whether the wall thickness of the piping component is below a predetermined value based on the acceleration of the striking hammer when striking the surface of the piping component.

[0021] before The wall-thinning estimation unit may be configured to estimate that there is a higher probability that the wall thickness of the piping component is below a predetermined value when both the mechanical impedance ZR and the index I obtained by measurement are lower than predetermined threshold values ​​for the mechanical impedance ZR and the index I, respectively, corresponding to the nominal diameter and material of the piping component being measured.

[0022] The thickness of the piping member is the sum of the thickness of the first piping member and the thickness of the second piping member at a joint where the second piping member is inserted into the first piping member, and the wall-thinning estimation unit can be configured to estimate that a gap has been formed between the first piping member and the second piping member when one or both of the mechanical impedance ZR and the index I obtained by measurement are lower than predetermined threshold values ​​for the mechanical impedance ZR and the index I, respectively, corresponding to the nominal diameter and material of the piping member to be measured.

[0023] In addition, it is preferable that the above-mentioned piping component wall thinning estimation device further includes a temperature measurement unit and a correction data storage unit that stores correlation data between temperature, the mechanical impedance ZR, and the index I for each nominal diameter and material, and the wall thinning estimation unit temperature-compensates the mechanical impedance ZR and the index I obtained by measurement based on the correlation data stored in the correction data storage unit, the nominal diameter and material of the piping component, and the temperature at the time of measurement, and estimates whether the wall thickness of the piping component is below a predetermined value based on the temperature-compensated mechanical impedance ZR' and index I'. Effect of the Invention

[0024] According to the present invention, by simply striking the surface of a piping component with an impact hammer and measuring the acceleration of the impact hammer, it is possible to estimate whether the wall thickness of the piping component is below a predetermined value, i.e., whether the amount of reduction (thinning amount) or the amount of reduction (thinning rate) of the wall thickness of the piping component exceeds a predetermined value, based on the measured acceleration of the impact hammer. Therefore, thinning and construction state can be estimated by a simple and inexpensive non-destructive test. In addition, since the presence or absence of thinning and connection failure can be diagnosed by performing non-destructive or destructive testing only on the piping component estimated to have thinning, it is possible to reduce the cost for accurate diagnosis. [Brief description of the drawings]

[0025] [Figure 1] 1 is an overall configuration diagram of a piping component wall thinning estimation device according to the present invention; [Diagram 2] 2 is a functional block diagram of the piping component wall-thinning estimation device shown in FIG. 1. [Diagram 3] 2 is an acceleration waveform diagram when a piping component is struck by an impact hammer of the piping component wall-thinning estimation device shown in FIG. 1. FIG. [Figure 4] This is a correlation diagram showing the relationship between the outer diameter and mechanical impedance ZR for sound and thinned straight pipes of the same material (pipe type), with the line segments that represent the threshold values ​​of mechanical impedance ZR that distinguish between sound and thinned pipes being superimposed. [Diagram 5] This is a correlation diagram showing the relationship between the outer diameter and the wall-thinning index INDEX for straight pipes of the same material (pipe type), with the line segment that is the threshold value of the wall-thinning index INDEX that distinguishes between sound and thinned products superimposed. [Figure 6] This is a correlation diagram showing the relationship between the wall-thinning rate and mechanical impedance ZR when the wall-thinning is caused on the inner circumferential surface side of straight pipes of the same material (pipe type) and outer diameter. [Figure 7] FIG. 1 is a correlation diagram showing the relationship between the wall-thinning rate and the wall-thinning index INDEX when the wall-thinning is caused on the inner peripheral surface side for straight pipes of the same material (pipe type) and outer diameter. [Figure 8]This is a correlation diagram showing the relationship between temperature and mechanical impedance ZR when the nominal diameter is changed for the same material (pipe type). [Figure 9] This is a correlation diagram showing the relationship between temperature and metal loss index INDEX when the nominal diameter is changed for the same material (pipe type). [Figure 10] This is a correlation diagram showing the relationship between temperature and mechanical impedance ZR when the material (pipe type) is changed while keeping the nominal diameter the same. [Figure 11] This is a correlation diagram showing the relationship between temperature and metal loss index INDEX when the material (pipe type) is changed while keeping the nominal diameter the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method and an apparatus for estimating wall-thinning in a piping component according to the present invention will be described with reference to the drawings.

[0027] First, with reference to Figs. 1 and 2, the overall configuration of a piping component wall-thinning estimation device 11 that uses a wall-thinning estimation method for a piping component P according to the present invention will be described.

[0028] The piping component wall-thinning estimation device (hereinafter simply referred to as the "wall-thinning estimation device") 11 strikes the surface of a synthetic resin piping component P such as a pipe, joint, elbow, cross, socket, union, valve, etc., and estimates the wall-thinning (i.e. the amount of wall-thinning or wall-thinning rate) based on a judgment of whether the product is sound with a wall thickness equal to or greater than a predetermined value, or has wall-thinness below the predetermined value. The wall-thinning estimation device 11 includes an impact hammer 13 for striking the surface of the synthetic resin piping component P to apply an impact, and a measurement and analysis device 15 for analyzing the measured value of the acceleration of the impact hammer 13.

[0029] The striking hammer 13 includes a striking part 13a for striking the surface of the piping component P, a grip part 13b connected to the striking part 13a so as to be held by an operator, and an acceleration sensor 17 attached to the surface of the striking part 13a opposite to the striking surface, so that an operator can hold the grip part 13b and strike the surface of the piping component P with the striking part 13a to measure the acceleration of the striking part 13a during striking. The acceleration sensor 17 is connected to the measurement and analysis device 15 via a cable 19 that passes through the grip part 13b and extends to the outside, and the measurement signal measured by the acceleration sensor 17 (i.e., the acceleration of the striking part 13a) can be transmitted to the measurement and analysis device 15.

[0030] The striking portion 13a may have any suitable shape as long as it has a certain mass m and can strike the surface of the piping member P. The acceleration sensor 17 may be any suitable type of acceleration sensor, such as a piezoelectric element type, a semiconductor gauge type, or a resistance wire strain type.

[0031] As shown in detail in Figure 2, the measurement analysis device 15 includes a measurement value memory unit 15a that stores the measurement signal (acceleration of the impact portion 13a) transmitted from the acceleration sensor 17 via the cable 19, a threshold value memory unit 15b that stores predetermined threshold values ​​for the mechanical impedance ZR and the wall thinning index INDEX described below, a correction data memory unit 15c that stores data for temperature correction of the mechanical impedance ZR and the wall thinning index INDEX, a wall thinning estimation unit 15d that estimates the wall thinning of the piping component P, i.e., the amount of wall thinning or the wall thinning rate, based on the measurement value by the acceleration sensor 17, a display unit 15e for displaying the results estimated by the wall thinning estimation unit 15d, and a temperature measurement unit 15f for measuring the temperature of the measurement environment.

[0032] When the surface of the piping component P is struck by the striking hammer 13, the surface of the piping component P undergoes elastic deformation or in addition slight plastic deformation due to the impact of the striking hammer 13, and at the same time the striking hammer 13 receives a reaction force due to the deformation from the surface of the piping component P. As a result, after the striking hammer 13 collides with the striking part 13a of the striking hammer 13 at time t = T1, the striking hammer 13 is decelerated by the reaction force from the surface of the piping component P from the initial collision velocity Va (hereinafter also simply referred to as the "collision velocity") at the moment the striking part 13a collides with the surface of the piping component P at an acceleration a(t) to a velocity of 0 at time t = T2, and is further accelerated by the acceleration a(t) in the opposite direction to the velocity direction at the time of collision, and at time t = T3 the striking part 13a separates from the surface of the piping component P, at which moment the acceleration a(t) becomes 0 and the rebound velocity becomes the maximum rebound velocity (hereinafter also simply referred to as the "rebound velocity") Vr. Here, t means time, and acceleration a(t) means the acceleration of the striking hammer 13 at time t. Therefore, the collision velocity Va is calculated by integrating the acceleration a(t) from time t = T1 to time t = T2, and the repulsion velocity Vr is calculated by integrating the acceleration a(t) from time t = T2 to time t = T3. In addition, the striking force F(t) generated on the surface of the piping component P by the striking hammer 13 can be calculated by the formula F(t) = m a(t), where m is the mass of the striking hammer 13.

[0033] Assuming that most of the deformation of the piping component P is elastic deformation, the repulsive force from the surface of the piping component P becomes maximum when the velocity V of the striking hammer 13 becomes 0, and the acceleration a(t) becomes maximum when the velocity V of the striking hammer 13 becomes 0. Therefore, as shown in FIG 3, the acceleration a(t) at time t becomes 0 at time t=T1 when the striking part 13a of the striking hammer 13 collides with the surface of the piping component P, and at time t=T3 when the striking part 13a of the striking hammer 13 separates from the surface of the piping component P, and reaches the maximum value a(t) at time t=T2 when the velocity V of the striking hammer 13 becomes 0. max In addition, the impact force F reaches a maximum value F at time t = T2. max and F max is the formula F max =m·a maxIn the following explanation, the period from time t=T1 to time t=T2 is referred to as the penetration process, and the period from time t=T2 to time t=T3 is referred to as the repulsion process.

[0034] On the other hand, if the thickness of the piping component P is reduced, the repulsive force when the piping component P is struck also decreases, and the maximum acceleration a max That is, the maximum impact force F max , and the maximum rebound velocity Vr. From this, the inventors have concluded that the amount or rate of reduction in the wall thickness of the piping member P (i.e., the amount or rate of reduction in wall thickness) affects the acceleration of the striking hammer 13 when the piping member P is restored from deformation after being struck by the striking hammer 13, i.e., during the rebound process. max The mechanical impedance of the rebound process is ZR=F, which is the value obtained by dividing by the maximum rebound velocity Vr. max It has been found that the thinning (reduction in thickness) of the piping component P, specifically, the thinning amount or thinning rate of the piping component P, can be estimated based on the thinning index INDEX=Va / Vr, which is the ratio of the collision speed Va to the rebound speed Vr. It goes without saying that the thinning index INDEX may be Vr / Va.

[0035] The mechanical impedance ZR of the repulsion process depends on the impact velocity Va. max is obtained by dividing by Vr, which depends on the impact speed Va, so it is a value that is not affected by the impact speed Va, and the thinning index INDEX is also a value that is not affected by the impact speed Va, because it is the ratio of the impact speed Va to the rebound speed Vr. Therefore, it is not affected by the strength of the impact. In addition, the effect of the reduction in the wall thickness of the piping component P appears in the rebound process, so the mechanical impedance ZA of the penetration process is F max / Va, but the mechanical impedance of the repulsion process ZR=F max / Vr is used as an index for estimating the reduction in wall thickness (i.e., thinning).

[0036] Furthermore, the present inventors have found that the mechanical impedance ZR and the thinning index INDEX during the rebound process of the synthetic resin piping member P depend on temperature. Therefore, the temperature during measurement for estimating the thickness reduction (i.e., thinning) is measured by the temperature measuring unit 15f based on the temperature during measurement for determining a threshold value described later, and the mechanical impedance ZR and the thinning index INDEX during the rebound process obtained from the measured acceleration value are temperature-compensated based on the measured temperature, thereby making it possible to more accurately estimate the thickness reduction (i.e., thinning) of the piping member P.

[0037] Based on the above-mentioned findings of the inventor, the wall-thinning estimation unit 15d estimates whether the wall thickness of the piping component P falls below a predetermined value based on the mechanical impedance ZR in the rebound process and the wall-thinning index INDEX obtained from the measurement value by the acceleration sensor 17. Below, a detailed explanation will be given of an example of a method in which the wall-thinning estimation unit 15d of the illustrated piping component wall-thinning estimation device 11 estimates a decrease in the wall thickness (i.e., wall-thinning) of the piping component P based on the measurement value of the acceleration of the striking hammer 13 by the acceleration sensor 17.

[0038] First, for each pipe type and nominal diameter of the piping member P, a plurality of piping members P are divided into sound products below a reference value and sound products with thinning exceeding the reference value based on a predetermined amount of thinning or thinning rate, and for each of them, a mechanical impedance ZR in the rebound process and a thinning index INDEX are calculated from the measured value of acceleration a(t) obtained by striking with the striking hammer 13, and thresholds for the mechanical impedance ZR and the thinning index INDEX between sound products and thin products are determined in advance and stored in the threshold storage unit 15b. As will be described later, when the pipe type and nominal diameter of the piping member P are specified, it is known that the thinning rate and the mechanical impedance ZR in the rebound process and the thinning index INDEX are approximated by a linear function with a negative gradient. Therefore, for example, under the condition that the pipe type and nominal diameter are fixed, for example, for a piping member P whose wall-thinning rate is changed by cutting the inner diameter, the mechanical impedance ZR and wall-thinning index INDEX in the rebound process are calculated from the measured value of the acceleration a(t) obtained by striking with the striking hammer 13, a linear function that approximates the relationship between the wall-thinning rate and the mechanical impedance ZR and wall-thinning index INDEX in the rebound process is obtained, and threshold values ​​of the mechanical impedance ZR and wall-thinning index INDEX corresponding to the wall-thinning rate that distinguishes between a sound product and a wall-thinned product are determined based on the linear function that is approximated, and stored in the threshold value storage unit 15b. It is preferable that the measurement for determining the threshold value is performed under a specific temperature condition. The material of the piping member P is determined by the pipe type. In addition, since the nominal diameter of the piping member P is generally determined according to a standard, when the nominal diameter is specified, the outer diameter and thickness (i.e., the inner diameter) are specified based on the standard. Therefore, determining threshold values ​​for the mechanical impedance ZR and the thinning index INDEX between healthy and thin products for each pipe type and nominal diameter of the piping component P is equivalent to determining threshold values ​​for the mechanical impedance ZR and the thinning index INDEX between healthy and thin products for each material, outer diameter, and thickness (i.e., inner diameter) of the piping component P.

[0039] It is also preferable to measure the acceleration a(t) by performing tapping with the striking hammer 13 while changing the temperature conditions for each pipe type and nominal diameter of the piping member P, calculate the mechanical impedance ZR and the wall thinning index INDEX in the rebound process from the measured value of the acceleration a(t), and obtain a correlation between the temperature and the mechanical impedance ZR and the wall thinning index INDEX in advance and store it in the correction data storage unit 15c in advance. When the pipe type and nominal diameter of the piping member P are determined, the temperature, the mechanical impedance ZR, and the wall thinning index INDEX can be approximated by a linear function, so that, for example, the approximated linear function may be stored in the correction data storage unit 15c. Also, a temperature correction coefficient for each temperature may be determined based on the temperature conditions at the time of measurement for determining the threshold value, and the temperature correction coefficient may be stored in the correction data storage unit 15c.

[0040] Next, the impact hammer 13 strikes the surface of the synthetic resin piping member P to be diagnosed, and the acceleration a(t) of the impact hammer 13 measured by the acceleration sensor 17 is measured over time and stored in the measurement value storage unit 15a. max It is preferable to determine upper and lower limits of the acceleration a(t) and use only the measured value when the maximum impact force falls within the range between the upper and lower limits. max and the time T2 at which this value was observed are known. In wall-thinning estimation unit 15d, collision velocity Va is calculated by time-integrating acceleration a(t) from the measured values ​​over time of acceleration a(t) stored in measurement value storage unit 15a over the time period from 0 to the maximum value (i.e., from time T1 to time T2), and rebound velocity Vr is calculated by time-integrating acceleration a(t) from the measured values ​​over time of acceleration a(t) stored in measurement value storage unit 15a over the time period from the maximum value to the time when it decreases back to 0 (i.e., from time T2 to time T3). In addition, maximum acceleration a(t) is calculated from the measured values ​​over time of acceleration a(t) stored in measurement value storage unit 15a. max Since the mass m of the striking hammer 13, which is known in advance, and the measured value of the acceleration a(t) over time stored in the measured value storage unit 15a are used, the formula F max =m·a maxThe maximum impact force F generated when the impact part 13a of the impact hammer 13 impacts the surface of the piping member P is max The collision speed Va, the rebound speed Vr, and the maximum impact force F are calculated in this way. max Therefore, the wall-thinning estimation unit 15d uses the formula ZR=F max Based on / Vr and the formula INDEX=Va / Vr, the mechanical impedance ZR and the metal loss index INDEX during the rebound process are calculated.

[0041] After obtaining the mechanical impedance ZR and the metal-thinning index INDEX in the rebound process, the metal-thinning estimation unit 15d preferably measures the temperature at the time of measurement for estimating the metal-thinning by the temperature measurement unit 15f, and performs temperature correction on the mechanical impedance ZR and the metal-thinning index INDEX obtained as described above, according to the temperature conditions at the time of measurement, based on the temperature correction data stored in the correction data storage unit 15c. As described above, the temperature correction may be performed, for example, by storing an approximation function of the mechanical impedance ZR and the metal-thinning index INDEX with respect to temperature in the correction data storage unit 15c and using the approximation function stored in the correction data storage unit 15c, or by storing a correction coefficient for the mechanical impedance ZR and the metal-thinning index INDEX at each temperature based on the temperature conditions at the time of measurement for determining the threshold value in the correction data storage unit 15c and using the correction coefficient stored in the correction data storage unit 15c, and the correction method is not limited. By performing the temperature correction in this manner, it is possible to estimate the metal-thinning more accurately.

[0042] When temperature correction is performed, the wall-thinning estimation unit 15d uses the values ​​of the mechanical impedance ZR' and the wall-thinning index INDEX' obtained by temperature-correcting the mechanical impedance ZR and the wall-thinning index INDEX obtained from the measured value of the acceleration due to tapping of the piping component P to be diagnosed using the method described above.When temperature correction is not performed, the wall-thinning estimation unit 15d uses the values ​​of the mechanical impedance ZR and the wall-thinning index INDEX obtained from the measured value of the acceleration due to tapping of the piping component P to be diagnosed and compares them with the threshold values ​​corresponding to the pipe type and nominal diameter of the piping component P to be diagnosed among the threshold values ​​of the mechanical impedance ZR and the wall-thinning index INDEX pre-stored in the threshold memory unit 15b. If at least one of the values ​​of the mechanical impedance ZR and the wall thinning index INDEX of the piping component P to be diagnosed, or at least one of the values ​​of the mechanical impedance ZR' and the wall thinning index INDEX' after temperature correction, falls below the threshold values ​​of the mechanical impedance ZR and the wall thinning index INDEX pre-stored in the threshold memory unit 15b corresponding to the pipe type and nominal diameter of the piping component P to be diagnosed, the wall thinning estimation unit 15d estimates that the wall thickness of the piping component P to be diagnosed is below a predetermined value, i.e., that the amount of wall thinning or the wall thinning rate exceeds a predetermined value, and displays the estimation result on the display unit 15e. On the other hand, if both the values ​​of the mechanical impedance ZR and the wall thinning index INDEX of the piping component P to be diagnosed, or both the values ​​of the mechanical impedance ZR' and the wall thinning index INDEX' after temperature correction, are greater than or equal to the threshold values ​​of the mechanical impedance ZR and the wall thinning index INDEX pre-stored in the threshold memory unit 15b corresponding to the pipe type and nominal diameter of the piping component P to be diagnosed, respectively, the wall thinning estimation unit 15d estimates that the wall thickness of the piping component P to be diagnosed is greater than or equal to a predetermined value, i.e., that the amount of wall thinning or the wall thinning rate is less than or equal to a predetermined value, and displays the estimation result on the display unit 15e.In addition, if both the values ​​of the mechanical impedance ZR and the wall-thinning index INDEX of the piping component P to be diagnosed and both the values ​​of the temperature-corrected mechanical impedance ZR' and the wall-thinning index INDEX' fall below the threshold values ​​of the mechanical impedance ZR and the wall-thinning index INDEX pre-stored in the threshold memory unit 15b corresponding to the pipe type and nominal diameter of the piping component P to be diagnosed, the wall-thinning estimation unit 15d may estimate that there is a higher probability that the wall thickness of the piping component P to be diagnosed is below a predetermined value, i.e., that there is a higher probability that it is a product with thinning, and display this fact on the display unit 15e.

[0043] In this way, by using the piping component wall-thinning estimation device 11, the wall-thinning estimation method of the present invention can be implemented, and the reduction in the wall thickness of the piping component P, i.e., wall-thinning, can be estimated by simply measuring the acceleration of the striking hammer 13 when striking the piping component P to be diagnosed. Therefore, even if the entire piping system is inspected, it is possible to estimate the location of the wall-thinned portion in a short time and at low cost. In addition, if a more accurate diagnosis is required, the piping component P estimated to be a wall-thinned product may be subjected to ultrasonic flaw detection testing, radiographic testing, or destructive testing, which have been conventionally performed as non-destructive testing methods. If the conventional non-destructive testing is performed only on the piping component P estimated to be a wall-thinned product by the piping component wall-thinning estimation device 11 and the wall-thinning estimation method of the present invention, the inspection time can be significantly shortened and the cost can be significantly reduced compared to the case of performing conventional non-destructive testing on the entire piping system. In addition, by using the piping component wall-thinning estimation device 11 and the wall-thinning estimation method for a piping component P according to the present invention, it is possible to narrow down the locations where the wall thickness of the piping component P is likely to have decreased (i.e., locations where wall-thinning is likely to have occurred), making it easier to apply radiographic testing. Furthermore, by performing destructive testing only on the piping components P estimated to have thinning by the piping component wall-thinning estimation device 11 and the wall-thinning estimation method for a piping component P according to the present invention, it becomes possible to shorten the operation downtime because only the minimum number of parts need to be replaced. EXAMPLES

[0044] Figure 4 shows a correlation diagram showing the relationship between the outer diameter and the mechanical impedance ZR for sound and thinned specimens obtained from the experimental results. The experiment was conducted by using straight rigid polyvinyl chloride pipes (manufactured by Asahi Yukizai, pipe type: VP) of various nominal diameters conforming to the JIS K6741:2016 standard as test specimens, and measuring the mechanical impedance ZR during the rebound process from the acceleration a(t) of the striking hammer 13 when striking each test specimen consisting of sound and thinned specimens of each outer diameter. In the experiment, the inner circumferential side of the unused specimen was cut to artificially thin the thickness of each specimen, and the amount or rate of thinning was measured in advance. Those with a thinning rate of 15% or less were classified as sound and those with a thinning rate of 15% or more were classified as thinned. In Figure 4, the results obtained from sound specimens are indicated by "○" and the results obtained from thinned specimens are indicated by "×". Like the line segment shown in Figure 4, it is possible to determine threshold values ​​for the mechanical impedance ZR for each outer diameter that separates healthy products from those with thinning, and it is possible to estimate whether the thinning rate is 15% or less, i.e., whether the product is healthy or thinning, depending on whether the mechanical impedance ZR measured in the piping component P to be diagnosed is below each threshold value. Note that if the standard is followed, the outer diameter, inner diameter, thickness, etc. can be specified once the nominal diameter is determined.

[0045] Figure 5 shows a correlation diagram showing the relationship between the outer diameter and the thinning index INDEX for sound and thinned specimens obtained from the experimental results. The experiment was conducted by using straight rigid polyvinyl chloride pipes (manufactured by Asahi Yukizai, pipe type: VP) of various nominal diameters conforming to the JIS K6741:2016 standard as test specimens, and measuring the acceleration a(t) of the striking hammer 13 when striking each specimen consisting of sound and thinned specimens of each outer diameter. In the experiment, the inner circumferential surface side of each specimen was cut to artificially thin the thickness and the thinning amount or thinning rate was measured in advance. Those with a thinning rate of 15% or less were classified as sound and those with a thinning rate of 15% or more were classified as thinned. In Figure 5, as in Figure 4, the results obtained from sound specimens are indicated by "○" and the results obtained from thinned specimens are indicated by "×". As shown in the line in Figure 5, a threshold value for the thinning index INDEX for each outer diameter that separates healthy products from thinned products can be set, and it can be seen that depending on whether the thinning index INDEX measured in the piping component P to be diagnosed falls below the respective threshold value, it is possible to estimate whether the thinning rate is 15% or less, i.e., whether the product is healthy or thinned.

[0046] Figure 6 shows a correlation diagram showing the relationship between the thinning rate and the mechanical impedance ZR obtained from the experimental results. The thinning rate was calculated by cutting the inner circumferential side of an unused straight polyvinyl chloride pipe (manufactured by Asahi Organic Chemicals, pipe type: VP300A) conforming to the JIS K6741:2016 standard, artificially thinning the pipe while changing the amount of thinning, and then measuring the acceleration a(t) of the striking hammer 13 when hitting each specimen with the striking hammer 13. Figure 6 shows that there is a correlation between the thinning rate and the mechanical impedance ZR, and that the mechanical impedance ZR in the rebound process can be approximated by a linear function with a negative gradient with respect to the thinning rate, that is, the mechanical impedance ZR decreases almost linearly as the thinning rate increases, and the thinning rate of the piping component P can be estimated from the mechanical impedance ZR measured in the piping component P to be diagnosed.

[0047] Figure 7 shows a correlation diagram showing the relationship between the wall-thinning rate and wall-thinning index INDEX obtained from the experimental results. The test specimens were made of rigid polyvinyl chloride straight pipes (manufactured by Asahi Yukizai, pipe type: VP300A) with a nominal diameter of 300 mm conforming to the JIS K6741:2016 standard, and the wall-thinning rate was calculated by cutting the inner circumferential side of the unused pipes and artificially reducing the wall-thinning rate while changing the amount of wall-thinning. Each test specimen was then struck by the striking hammer 13, and the wall-thinning index INDEX was calculated from the acceleration a(t) of the striking hammer 13. Figure 7 shows that there is a correlation between the wall-thinning rate and the wall-thinning index INDEX, and that the wall-thinning index INDEX can be approximated by a linear function with a negative gradient with respect to the wall-thinning rate, that is, the wall-thinning index INDEX decreases almost linearly as the wall-thinning rate increases, and the wall-thinning rate of the piping component P to be diagnosed can be estimated from the wall-thinning index INDEX measured in the piping component P to be diagnosed.

[0048] From the results shown in Figures 4 to 7, it can be seen that by predetermining threshold values ​​for the mechanical impedance ZR and the thinning index INDEX in the rebound process for each material (pipe type) and nominal diameter (outer diameter, inner diameter or thickness), it is possible to estimate the thinning (more specifically, the amount of thinning or the thinning rate) of the piping component P to be diagnosed, if the material (pipe type) and nominal diameter (outer diameter, inner diameter or thickness) are identified.

[0049] 8 and 9 are correlation diagrams showing the relationship between temperature and mechanical impedance ZR and thinning index INDEX obtained from the experimental results. The experiment was conducted by using straight pipes made of hard polyvinyl chloride (manufactured by Asahi Yukizai Co., Ltd., pipe type VP) with different nominal diameters as test specimens, changing the temperature conditions, and measuring the acceleration a(t) of the striking hammer 13 when striking each test specimen with the striking hammer 13 under each temperature condition. FIG. 8 shows the correlation between temperature and mechanical impedance ZR in the rebound process, and FIG. 9 shows the correlation between temperature and thinning index INDEX. In the experiment, an unused straight pipe was used as the test specimen. In FIG. 8 and FIG. 9, the results obtained from a straight pipe with a nominal diameter of 25 mm are shown as "○", the results obtained from a straight pipe with a nominal diameter of 100 mm are shown as "×", the results obtained from a straight pipe with a nominal diameter of 150 mm are shown as "△", and the results obtained from a straight pipe with a nominal diameter of 200 mm are shown as "□". From Fig. 8, it can be seen that if the pipe type, i.e., material, is specified, for straight pipes of each nominal diameter, the mechanical impedance ZR in the rebound process decreases almost linearly with increasing temperature and can be approximated by a linear function with a negative gradient with respect to temperature. Similarly, from Fig. 9, it can be seen that if the pipe type, i.e., material, is specified, for straight pipes of each nominal diameter, the wall thinning index INDEX decreases almost linearly with increasing temperature and can be approximated by a linear function with a negative gradient with respect to temperature.

[0050] Figures 10 and 11 show correlation diagrams showing the relationship between temperature and mechanical impedance ZR and thinning index INDEX obtained from the experimental results. Test specimens were straight pipes (manufactured by Asahi Yukizai Co., Ltd., pipe types VP, HI, and HT) with the same nominal diameter. The test specimens were struck by the striking hammer 13 under different temperature conditions. The mechanical impedance ZR and thinning index INDEX were obtained from the acceleration a(t) of the striking hammer 13 measured during the rebound process. The material of the VP pipe type was hard polyvinyl chloride, the material of the HI pipe was impact-resistant hard polyvinyl chloride, and the material of the HT pipe was heat-resistant hard polyvinyl chloride. Figure 10 shows the correlation between temperature and mechanical impedance ZR during the rebound process, and Figure 11 shows the correlation between temperature and thinning index INDEX. In the experiment, an unused straight pipe was used as the test specimen. In Figures 10 and 11, the results obtained from a 100mm nominal diameter straight pipe made of rigid polyvinyl chloride are indicated by "x", the results obtained from a 100mm nominal diameter straight pipe made of impact-resistant rigid polyvinyl chloride are indicated by "△", and the results obtained from a 100mm nominal diameter straight pipe made of heat-resistant rigid polyvinyl chloride are indicated by "□". From Figure 10, it can be seen that if the nominal diameter is specified, for a straight pipe of a certain material, the mechanical impedance ZR in the rebound process decreases almost linearly with increasing temperature and can be approximated by a linear function with a negative gradient with respect to temperature. Similarly, from Figure 9, it can be seen that if the type of pipe, i.e., the material, is specified, for straight pipes of each nominal diameter, the wall thinning index INDEX decreases almost linearly with increasing temperature and can be approximated by a linear function with a negative gradient with respect to temperature.

[0051] From the results shown in Figures 8 to 11, it can be seen that if the material (pipe type) and nominal diameter (outer diameter, inner diameter or thickness) are specified, the mechanical impedance ZR and the metal loss index INDEX in the rebound process change approximately according to a linear function with respect to temperature for each material (pipe type) and outer diameter (outer diameter, inner diameter or thickness). Therefore, if a linear function that approximates the change in the mechanical impedance ZR and the metal loss index INDEX in the rebound process with respect to temperature is obtained in advance for each material (pipe type) and outer diameter (outer diameter, inner diameter or thickness), and the mechanical impedance ZR and the metal loss index INDEX in the rebound process obtained from the measurement are temperature-compensated based on the temperature at the time of measurement, it becomes possible to suppress the influence of temperature. It goes without saying that the same effect can be obtained by determining in advance from the above linear function the correction coefficients for the mechanical impedance ZR and the wall-thinning index INDEX at each temperature based on the temperature at the time of measurement to determine the threshold values ​​of the mechanical impedance ZR and the wall-thinning index INDEX in the rebound process for each material (pipe type) and outer diameter (outer diameter, inner diameter or thickness), and temperature-correcting the mechanical impedance ZR and the wall-thinning index INDEX in the rebound process obtained from the measurement using the correction coefficients based on the temperature at the time of measurement. If the above-mentioned method for estimating wall-thinning of the piping member P is performed based on the temperature-corrected mechanical impedance ZR' and wall-thinning index INDEX', the effect of temperature can be suppressed and the reduction in the wall thickness of the piping member P, i.e., the wall-thinning can be estimated more accurately.

[0052] The method and device for estimating wall-thinning of a piping component P according to the present invention have been described above with reference to the illustrated embodiment, but the present invention is not limited to the illustrated embodiment. For example, in the illustrated embodiment of the piping component wall-thinning estimation device 11, the measurement and analysis device 15 is provided with a display unit 15e, and the estimation result regarding wall-thinning is displayed on the display unit 15e, but it is also possible for the measurement and analysis device 15 to be provided with an alarm unit, and for the alarm unit to emit an alarm sound when it is estimated that the wall-thinning amount or wall-thinning rate exceeds a predetermined value. In the illustrated piping component wall-thinning estimation device 11, the impact hammer 13 and the measurement and analysis device 15 are configured as separate bodies, but the measurement and analysis device 15 may be formed integrally with the impact hammer 13. [Explanation of symbols]

[0053] 11. Piping component thinning estimation device 13 Impact hammer 13a Striking section 13b Grip part 15 Measurement and analysis equipment 15a Measurement value memory section 15b Threshold memory unit 15c Correction data storage section 15d Thickness reduction estimation section 15e Display section 17 Acceleration Sensor 19 Cable

Claims

1. A method for estimating wall thinning of a synthetic resin piping member using a measuring device including an impact hammer and an acceleration sensor attached to the impact hammer, comprising: The impact hammer strikes a surface of a synthetic resin piping member, and the acceleration sensor measures the acceleration of the impact hammer over time. From the measured acceleration of the impact hammer, at least one of a mechanical impedance ZR during the rebound process in which the impact hammer rebounds from the surface of the piping component in the direction opposite to when the impact hammer impacted the surface of the piping component, and an index I calculated from the collision speed Va when the impact hammer collides with the surface of the piping component and the rebound speed Vr when the impact hammer rebounds from the surface of the piping component using the equation I = Va / Vr, and based on at least one of the obtained mechanical impedance ZR and index I, it is estimated whether or not the thickness of the piping component is below a predetermined value; The crash velocity Va is calculated by integrating the measured acceleration over a time period from 0 to a maximum value; The rebound velocity Vr is calculated by integrating the measured acceleration over time from a maximum value until it decreases back to zero; When the maximum value of the impact force generated when the impact hammer collides with the surface of the piping component is F max , F max is calculated from the mass of the impact hammer and the acceleration of the impact hammer measured by the acceleration sensor; The mechanical impedance ZR is calculated by the formula ZR=F max / Vr, A threshold value is previously determined for each of the mechanical impedance ZR and the index I; A method for estimating thinning of a piping component, comprising estimating that the thickness of the piping component is below a predetermined value when at least one of the mechanical impedance ZR and the index I obtained by measurement falls below a predetermined threshold value for each of the mechanical impedance ZR and the index I.

2. 2. The method for estimating thinning of a piping component according to claim 1, wherein when both the mechanical impedance ZR and the index I obtained by measurement are lower than respective predetermined threshold values ​​for the mechanical impedance ZR and the index I, it is estimated that there is a higher probability that the thickness of the piping component is below a predetermined value.

3. 3. The method for estimating wall-thickness reduction according to claim 1 or 2, wherein threshold values ​​are predefined for the mechanical impedance ZR and the index I for each nominal diameter and material of a synthetic resin piping component, and the method estimates whether the wall thickness of the piping component is below a predefined value by comparing the predefined threshold values ​​for the mechanical impedance ZR and the index I corresponding to the nominal diameter and material of the piping component to be measured with the mechanical impedance ZR and the index I obtained by measurement.

4. 4. The method for estimating thinning according to claim 1, wherein a thickness of the piping member is a sum of a thickness of the first piping member and a thickness of the second piping member at a joint where the second piping member is inserted into the first piping member, and when at least one of the mechanical impedance ZR and the index I obtained by measurement is lower than a predetermined threshold value for each of the mechanical impedance ZR and the index I, it is estimated that a gap is formed between the first piping member and the second piping member.

5. 5. The method for estimating thinning of a piping component according to claim 1, further comprising: determining in advance a correlation between temperature and the mechanical impedance ZR and the index I; temperature-compensating the mechanical impedance ZR and the index I determined by measurement based on the correlation determined in advance and the temperature at the time of measurement; and estimating whether the thickness of the piping component is below a predetermined value based on at least one of the temperature-compensated mechanical impedance ZR' and the index I'.

6. A pipe member wall thinning estimation device for estimating wall thinning of a synthetic resin pipe member, A striking hammer for striking a surface of a synthetic resin piping component; An acceleration sensor attached to the striking hammer; a measurement value storage unit that stores the acceleration of the striking hammer measured by the acceleration sensor over time; a wall-thickness reduction estimation unit that estimates whether or not a wall thickness of the piping member is below a predetermined value based on the acceleration stored in the measurement value storage unit; a threshold value storage unit that stores predetermined threshold values ​​for the mechanical impedance ZR and the index I for each nominal diameter and material of the piping member; Equipped with The wall-thinning estimation unit calculates, from the acceleration stored in the measurement value storage unit, at least one of a mechanical impedance ZR during the rebound process in which the impact hammer rebounds from the surface of the piping component in a direction opposite to that at which the impact hammer impacts the surface of the piping component, and an index I calculated by the equation I=Va / Vr from the impact velocity Va when the impact hammer impacts the surface of the piping component and the rebound velocity Vr when the impact hammer rebounds from the surface of the piping component; and estimates that the wall thickness of the piping component is below a predetermined value when at least one of the mechanical impedance ZR and the index I calculated by measurement is lower than predetermined threshold values ​​for the mechanical impedance ZR and the index I corresponding to the nominal diameter and material of the piping component to be measured; The collision velocity Va is calculated by integrating the acceleration stored in the measurement value storage unit over a time period during which the acceleration increases from 0 to a maximum value, The rebound velocity Vr is calculated by integrating the acceleration stored in the measurement value storage unit over a time period from a maximum value until the acceleration decreases to 0 again, When the maximum value of the impact force generated when the impact hammer collides with the surface of the piping component is F max , F max is calculated from the mass of the impact hammer and the acceleration of the impact hammer stored in the measurement value storage unit, The piping component wall thinning estimation device is characterized in that the mechanical impedance ZR is calculated by an equation: ZR=F max / Vr.

7. 7. The piping component wall-thinning estimation device according to claim 6, wherein the wall-thinning estimation unit estimates that there is a higher probability that the wall thickness of the piping component is below a predetermined value when both the mechanical impedance ZR and the index I obtained by measurement are lower than respective predetermined threshold values ​​for the mechanical impedance ZR and the index I corresponding to the nominal diameter and material of the piping component to be measured.

8. 8. The piping component wall-thinning estimation device according to claim 6 or claim 7, wherein the wall thickness of the piping component is the sum of the wall thickness of the first piping component and the wall thickness of the second piping component at a joint where the second piping component is inserted into the first piping component, and the wall-thinning estimation unit estimates that a gap is formed between the first piping component and the second piping component when one or both of the mechanical impedance ZR and the index I obtained by measurement are lower than predetermined threshold values ​​for the mechanical impedance ZR and the index I, respectively, corresponding to the nominal diameter and material of the piping component to be measured.

9. 9. The piping component wall-thinning estimation device according to claim 6, further comprising a temperature measuring unit and a correction data storage unit that stores correlation data between temperature, the mechanical impedance ZR, and the index I for each nominal diameter and material, wherein the wall-thinning estimation unit temperature-compensates the mechanical impedance ZR and the index I determined by measurement based on the correlation data stored in the correction data storage unit, the nominal diameter and material of the piping component, and the temperature at the time of measurement, and estimates whether the wall thickness of the piping component is below a predetermined value based on the temperature-compensated mechanical impedance ZR' and index I'.

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