JP6829534B1 - Non-destructive inspection equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-destructive inspection method applicable to a buried water pipe. SOLUTION: A speaker 202 and a sensor 204 are installed on a platform 201 that can be installed at a discharge port 112 of a fire hydrant 110 of an underground fire hydrant 100. The "system" is vibrated by the sound output from the speaker in one inspection, and the sensor 204 detects the detected resonance frequency. If there is no variation in the inspection environment, the tube thickness will become thinner with the passage of time, so if the detected resonance frequencies are arranged on the time axis, the resonance frequency will be lower as the time elapses. Look at this frequency and plan to dig out a certain range of water pipes. [Selection diagram] Fig. 6

Description

The present invention relates to a method for inspecting aged pipes, particularly non-destructive inspection.

The aging of water pipes that have been laid in the past has become a problem in recent years. Conventionally, it is common that a water leak in a water pipe is discovered after it actually occurs, and the water manager responds to the leak.

In addition to such symptomatic treatment, non-destructive inspection is also considered. A method using an in-plane bending deformation vibration mode of a pipe (Takada, Inoue, Shinoda; JSME Proceedings Vol. 84 (2018) No. 861: hereinafter Non-Patent Document 1) has been proposed. According to this document, it is pointed out that the local corrosion of the pipe reduces the average pipe pressure when the water pipe is regarded as a uniform cylinder. The method described in Non-Patent Document 1 is to quantify the aging condition due to corrosion of the pipe by measuring the natural frequency of the in-plane bending deformation vibration mode proportional to the thickness of the water pipe. .. In the method described in Non-Patent Document 1, since the natural frequency of the in-plane bending deformation vibration mode exists in the audible frequency band, it is said that an inexpensive inspection can be performed.

Further, a non-destructive inspection of a water pipe by vibration is also disclosed in Japanese Patent Application Laid-Open No. 2019-164613 (Patent Document 1). This prior art document presents field test results using an impulse hammer and an accelerometer.

Japanese Patent Application Laid-Open No. 2019-164613

Takada, Inoue, Shinoda; JSME Proceedings Vol. 84 (2018) No. 861

However, planned work is difficult to deal with after a water leak occurs.
Further, the invention described in Non-Patent Document 1 cannot be applied to a buried water pipe. This is because it is difficult to hit the water pipe. In addition, in a method similar to a tapping sound inspection, vibration with an impulse hammer must be performed manually, which is highly personal. Further, there is a problem that the work takes time.

On the contrary, in order to realize the invention described in Non-Patent Document 1 without using an impulse hammer, a method using an electrokinetic exciter can be considered. However, the electrodynamic exciter has problems such as the equipment itself is expensive, the equipment becomes heavy, and the equipment configuration becomes complicated due to the need for a power amplifier.

Further, in the method described in Patent Document 1, the deterioration cannot be determined until after the water leakage of the water pipe has occurred. This is because the present invention makes a determination based on the sound generated from the leaked portion.

An object of the present invention is to provide a method of non-destructive inspection applicable to a buried water pipe.

Specifically, it is a non-destructive inspection method performed by sounding an inspection speaker from a predetermined location of an underground fire hydrant.

A typical non-destructive inspection device according to the present invention includes a platform that can be fitted to the discharge port of a fire hydrant, and a speaker and a sensor mounted on the platform. The speaker vibrates the system and the sensor resonates. A non-destructive inspection device characterized by detecting frequency.

The non-destructive inspection device may be characterized in that the inspection target is the thickness of the water pipe.

The present invention makes it possible to perform non-destructive inspection on water pipes that have already been buried. This makes it possible to check for water leaks without digging out water pipes buried 60 cm to 30 cm below the surface of the earth, and as a result, it is possible to maintain the water network at low cost.

It is a figure which shows the area around the underground fire hydrant when confirming the aging state of the water pipe buried underground by the non-destructive inspection method which concerns on this invention. It is a figure which shows the periphery of the discharge port at the time of mounting the inspection apparatus which concerns on this invention. It is a system block diagram which shows the overview of the system (non-destructive inspection system) used in the non-destructive inspection method which concerns on this invention. It is a flowchart about the procedure to use a non-destructive inspection system. It is a flowchart about the measurement procedure per measurement of this invention. It is a graph which shows the result of having measured and compared the resonance frequency of a normal tube and an aging tube.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The present invention is characterized in that a vibrating speaker for acoustic applications is used for vibration of piping.

(First Embodiment)
FIG. 1 is a diagram showing the vicinity of an underground fire hydrant when confirming the aging condition of a water pipe buried underground by the non-destructive inspection method according to the present invention.

The area around the underground fire hydrant of FIG. 1 includes a water pipe 100, a fire hydrant 110, a storage pit 120, and a fire hydrant lid 130. The fire hydrant 110 includes a fire hydrant valve 111 and a discharge port 112.

The water pipe 100 is a water pipe to be inspected for non-destructive inspection. Both metal pipes and resin pipes can be measured, and in some cases, other materials can be applied.

The fire hydrant 110 is a fire hydrant installed for the purpose of serving as a fire hydrant in the event of a fire. In this specification, an underground fire hydrant is assumed. However, it goes without saying that it can also be applied to ground-based fire hydrants if the standards are slightly changed.

The storage pit 120 is a recess provided in a road or the like for storing the fire hydrant 110. If necessary, a drainage port or the like may be provided in the storage pit 120.

The fire hydrant valve 111 is a valve for water that enables water to be discharged by inserting a key handle (not shown) and turning the valve.

The discharge port 112 is a water discharge port for connecting a hose to extinguish a fire. Since the fire hydrant valve 111 is normally closed, water does not leak from the discharge port 112.

The discharge port 112 has a screw on the outer circumference, and the hose is screwed into this screw to withstand the water pressure at the time of discharge. In the present invention, a desired device (specifically, platform 201) is attached by screwing into this screw.

The fire hydrant lid 130 is a lid for closing the storage pit 120.

FIG. 2 is a diagram showing the periphery of the discharge port 112 when the inspection device 200 according to the present invention is mounted.

The inspection device 200 according to the present invention includes a platform 201, a speaker 202, an air vent valve 203, and a sensor 204.

The platform 201 is a platform for mounting the speaker 202 and the like. The lower surface of the platform 201 is threaded inward to fit the screw cut on the outer circumference of the discharge port 112. The designer should design by fitting this screw so that water does not leak when the fire hydrant valve 111 is opened.

The speaker 202 is a vibrating speaker for outputting measurement sound to the water pipe 100 to be measured and peripheral parts thereof. In the present specification, the speaker 202 includes a vibration speaker 202a, an axial force generating jig 202b, and an axial force adjusting mechanism 202c.

The vibration speaker 202a is a conductive speaker for audio use. The vibrating speaker may be an inexpensive and commercially available one.

The axial force generating jig 202b is a jig that applies an axial force in the excitation direction of the vibration speaker 202a. As a specific method of applying the axial force, there is a method of sandwiching the vibration speaker 202a with a parallel flat plate and fixing it by bolting, but this is not the case.

The axial force adjusting mechanism 202c has a function of adjusting the axial force of the axial force generating jig 202b and adjusting the resonance frequency of the vibration system composed of the vibration speaker 202a and the axial force generating jig 202b. As a specific adjustment function, there is a tightening torque adjustment wrench when the axial force generating jig 202b is composed of bolt tightening, but it is not a matter of concern.

The air bleeding valve 203 is an air bleeding valve for bleeding the air accumulated in the discharge port 112. Air collects at the joint between the platform 201 and the discharge port 112 when the platform 201 is attached or when the fire hydrant valve 111 is opened. Even if the speaker 202 is output with this air as it is, an appropriate measurement result may not be obtained. Therefore, it should be designed so that the accumulated air can be discharged to the outside by opening the air vent valve 203.

The sensor 204 is a vibration inspection unit for listening to the reflected sound of the sound output from the speaker 202. The direct sound from the speaker 202 can be excluded by designing it so that it can be shut out through a filter, but this cannot be confirmed in this figure because it is realized by processing the sound picked up by the sensor 204.

FIG. 3 is a system configuration diagram showing an overview of the system (non-destructive inspection system 300) used in the non-destructive inspection method according to the present invention.

The non-destructive inspection system 300 according to the present invention includes a vibration speaker control unit 301, a resonance frequency detection unit 302, and a storage unit 304.

The vibration speaker control unit 301 is a controller for controlling the vibration speaker 202a of the speaker 202. The vibration speaker control unit 301 includes a sound source file generation unit 301a, a sound source reproduction unit 301b, and a communication unit 301c.

The sound source file generation unit 301a generates an audio file including the resonance frequency component of the water pipe 100 to be measured.

The sound source reproduction unit 301b is a control unit for reproducing the audio file generated by the sound source file generation unit 301a from the vibration speaker 202a.

The communication unit 301c is a communication unit for transmitting the signal of the audio file reproduced by the sound source reproduction unit 301b to the vibration speaker 202a. Specifically, wired communication by USB and wireless communication by Bluetooth (registered trademark) are exemplified.

The resonance frequency detection unit 302 is a detector that extracts the resonance frequency of the water pipe 100 from the vibration signal measured by the sensor 204.

The storage unit 304 is an HDD, a non-volatile memory, or the like for storing the extracted resonance frequency.

Next, the procedure up to the use of the non-destructive inspection system 300 will be described with reference to FIG. FIG. 4 is a flowchart of the procedure up to the use of the non-destructive inspection system 300.

First, the operator opens the fire hydrant lid 130 and accesses the fire hydrant 110 (step S1001).

Next, the operator properly screwes the platform 201 into the discharge port 112 (step S1002) to prevent water from being discharged from the discharge port 112 and leaking when the fire hydrant valve 111 is opened.

When the installation of the platform 201 is completed, the operator opens the fire hydrant valve 111 (step S1003). As a result, the water level rises to the vicinity of platform 201.

When the operator determines that the water level has risen sufficiently after a lapse of a certain period of time, the operator opens the air vent valve 203 (step S1004). By discharging water for a certain period of time in this state (step S1005), the air remaining in the vicinity of the platform 201 is discharged. As a result, the conditions when measured a plurality of times can be kept uniform.

When the operator determines that the air has been sufficiently discharged, the operator closes the air vent valve 203 (step S1006). After that, the fire hydrant valve 111 is also closed (step S1007).

The operator then attaches the non-destructive inspection system 300 to the speakers 202 and sensors 204 on the platform 201 (step S1008). At this time, it goes without saying that the operator should remove the water leaked to the surroundings as much as possible.

As described above, by adjusting the measurement environment by the operator, the measurement conditions when multiple measurements are taken are kept constant, and the comparison for each measurement is significantly improved.

Next, how to measure in the environment prepared in FIG. 4 will be described.
FIG. 5 is a flowchart of the measurement procedure for each measurement of the present invention.

Basically, the processing on the speaker 202 side and the processing on the sensor 204 side are processed independently, but it goes without saying that there is no point unless the speaker 202 is started first. Therefore, the operator operates the vibration speaker control unit 301 to reproduce the sound source file (step S2001). After that, the operator activates the process on the sensor 204 side. Of course, if efficiency is ignored, the operator may start the processing on the sensor 204 side first.

When the operator reproduces the sound source file, the speaker 202 vibrates the system (step S2002). Here, the "system" refers to a fire hydrant and a water pipe. The fire hydrant is also vibrated for convenience of installation, but the information necessary for diagnosis can be obtained only by vibrating the water pipe.

Once the sound source file is played back, it is output from the speaker 202 until the end of the inspection.

On the other hand, the sensor 204 side is activated by the operator after the playback of the sound source file is started. Then, the vibration inspection by the sensor 204 is started (step S2003). The inspection result is input to the resonance frequency detection unit 302 as analog information, and after removing unnecessary information such as vibration directly transmitted from the speaker 202, the resonance frequency detection unit 302 performs analog-to-digital conversion (A / D conversion). (Step S2004).

After that, the resonance frequency detection unit 302 detects the resonance frequency to be detected and records it in the storage unit 204 (step S2005).

If the resonance frequency is detected and recorded in the storage unit 204, one measurement is completed. After that, the operator will try to restore the current state by removing the non-destructive inspection system 300.

Next, the handling of the resonance frequency recorded in the storage unit 204 will be described.
As described in FIG. 5, one resonance frequency is recorded in the storage unit for each measurement by the operator. Let's arrange the recorded resonance frequency data in order of recording time.

As water pipes age, the average pipe thickness becomes thinner than normal products. Therefore, the resonance frequency becomes low. Therefore, when the resonance frequency becomes lower than the frequency of the normal product by a certain amount or more, the operator can determine that it is necessary to prepare for replacement.

FIG. 6 is a graph showing the results of measuring and comparing the resonance frequencies of a normal tube and an aged tube. The horizontal axis means frequency and the vertical axis means amplitude. The curve obtained as a result of the actual measurement is called the self-frequency response function. In this figure, the self-frequency response function is measured and recorded, but originally, only the resonance frequency needs to be recorded. The vertical line in the center of the graph means 1000 Hz.

The "mountain" above the graph (= the side with the higher amplitude) is the resonance frequency. In FIG. 6, since the "mountain" exists in the vicinity of 800 Hz to 900 Hz, this 800 Hz to 900 Hz exists. The resonance frequency detection unit 302 records the frequency of this apex.

And, in the figure, it can be read that the resonance frequency of the old product is lower than that of the normal product. Based on the rate of this decrease, the operator estimates the pipe thickness and decides to replace it.

In this specification, it is assumed that the measurement is 20 m on one side and 40 m on the front and back from the measurement point. However, it goes without saying that there is a certain range in the output of the speaker 202, the type of pipe to be measured (water pipe, water distribution pipe, water supply pipe, etc.) and the output of the speaker 202.

As described above, by using the non-destructive inspection method of the present invention described in the present specification, by using the fire hydrant 110 of the underground fire hydrant, it is possible to perform the measurement without digging out the buried part.

Although the invention made by the present inventor has been specifically described above based on the embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof. Needless to say, there is.

For example, in the above, only the resonance frequency is recorded in the storage unit 304. However, the resonance frequency detection unit 302 may record the self-frequency response function in the storage unit 304.

Further, in the above, the operator makes a judgment. However, it is a quantitative judgment to say that the resonance frequency falls below a certain value at the start of measurement. Therefore, it should be considered that the resonance frequency accumulated in the storage unit 304 is analyzed in time series by a computer or the like (not shown) and the replacement is automatically determined.

The present invention has been conceived for the purpose of inspecting that the thickness of a water pipe becomes thin, but the present invention is not necessarily limited to its use. Needless to say, it can be applied to, for example, checking the thickness of a pipeline.

100: Water pipe,
110: Fire hydrant,
111: Fire hydrant valve,
112: Discharge port,
120: Storage pit,
130: Fire hydrant lid,
200: Inspection device,
201: Platform,
202: Speaker,
203: Air vent valve,
204: Sensor,
300: Non-destructive inspection system,
301: Vibration speaker control unit,
302: Resonant frequency detection unit,
304: Storage unit.

Claims (5)

A platform that can be fitted to the outlet of a fire hydrant,
A non-destructive inspection device including a speaker and a sensor mounted on the platform.
The speaker vibrates the system
The sensor is a non-destructive inspection device characterized by detecting the resonance frequency of an inspection target . In the non-destructive inspection apparatus according to claim 1,
A non-destructive inspection device characterized in that the sensor detects the resonance frequency based on the output of the speaker. In the non-destructive inspection apparatus according to claim 1 or 2.
A non-destructive inspection device characterized in that the inspection target is a water pipe. In the non-destructive inspection apparatus according to any one of claims 1 to 3.
Further, a non-destructive inspection apparatus including a recording unit that records the resonance frequency at the time of the initial inspection. In the non-destructive inspection apparatus according to claim 4,
A non-destructive inspection apparatus including a control unit that compares the resonance frequency at the time of the initial inspection with the resonance frequency measured by the sensor.

Images