JPS5972014A - Measuring method of length of buried piping - Google Patents

Abstract

PURPOSE:To measure the length of buried piping accurately by sending a sound wave into the buried piping from an entrance end and measuring the arrival time of the sound wave from the entrance end to the exit end. CONSTITUTION:A speaker 5 is connected to the entrance end 1a of the buried piping 1 and an oscillator 3 and an amplifier 4 are operated to send the sound wave into the piping from the speaker 5. Further, microphones 6 and 7 are installed at the entrance end 1a and exit end 1b and variation in sound pressure is detected and inputted to a time difference meter 10 through amplifiers 8 and 9 to knot the arrival time difference of the sound wave by the time difference meter 10. This time difference corresponds to the propagation time of the sound wave from the entrance end 1a to the exit end 1b and this time is multiplied by a sound velocity to find thelength of the piping. Even if there is a corrosion hole, different-diameter part, etc., in the middle of the buried piping 1, a secure, disturbance-free length measurement is taken with an about 1% error.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a buried pipe length measuring method for measuring the length of a buried pipe using the arrival time of sound waves.

Conventionally, when measuring the length of a buried pipe that has a bent part, it is difficult to directly insert a tape measure or the like to measure the length, and the length is measured indirectly using a metal detector or the like that uses a magnetic field. However, measurements using metal detectors have large errors and cannot be used for non-metallic piping. Furthermore, the method of measuring the length of buried piping by excavating part or all of the buried part requires large construction costs and labor (1).

The present invention is proposed in order to eliminate such conventional deficiencies, and it is possible to accurately know the length of piping buried in the ground or in building structures, which is useful for industrial purposes. The field of application is wide, for example, when painting and lining the inside of buried gas piping while the pipe is buried, knowing the length of the piping is an essential condition. If the present invention is applied to the lining method, the effect will be great.

Gas pipes are made of metal or other materials that can be considered rigid bodies, and when sound is generated inside the pipe, if the wavelength of the sound is larger than the pipe diameter, the pipe can be seen as a sound bud pipe.
Even if there is a bend, sound propagates inside the pipe as a plane wave that travels in the axial direction of the pipe at the speed of sound O. Time taken for sound to reach from the inlet end 11L to the outlet end 1b of the piping 1 shown in Figure 1 is t.
Then, the length l of the pipe 1 is expressed by the following formula.

/ -c

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG.

A speaker 5 is connected to the inlet end 1tL of the buried pipe 1, and the oscillator 3 and amplifier 4 are operated to generate sound waves from the speaker 5 into the pipe.

Further, four microphones 6 and 7 are installed at the entrance end 1a and the exit end 1b to detect changes in sound pressure and input their outputs to a time difference meter 10 via amplifiers 8 and 9. Time difference meter 1
0 to know the arrival time difference of the sound waves. This arrival time difference is,
This is the time for sound to propagate from the inlet end 1a to the outlet D@1b, and the length of the bud can be found by multiplying the speed of sound by this time. In this way, the length of the buried pipe 1 can be determined indirectly from the ends 1a and 1b of the pipe. Furthermore, the present invention provides a reliable system with almost no disturbance by measuring the sound propagation time even under conditions that are worse for an acoustic tube, such as a corroded hole or a portion with a different diameter. Length measurements can be made with an error of about 1%.

In addition, in the case of buried piping that has a main pipe and branch pipes, such as gas pipes and water pipes, as shown in Figure 3, if you measure the length by increasing the number of routes, you can measure not only the length between the ends of the pipe, but also the length of the branch pipes. The length of only the part can also be determined by calculation. For example, the length from the end of the engineer 12 to the ends of the branch pipes 13 and 14,
By measuring a total of three lengths between the ends of the branch pipes 13 and 14, the length of only the branch l1f13 can be calculated.

As described above, the present invention can safely, reliably, and accurately measure the length of various types of buried pipes indirectly from the ends of the pipes, regardless of whether they are metal or non-metallic. For measuring the length of pipes when painting and lining the inner surface of pipes, measuring the length of individual pipes buried in building structures, measuring the length of pipes whose shape is rough and difficult to measure directly, etc. It can be used and has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a model diagram of a buried pipe, FIG. 2 is an overall view of an embodiment of the present invention (4), and FIG. 3 is an example of a buried pipe having a main pipe and a branch pipe. 1. Butterfly piping, 2. Soil, 3. Transducer, 4.8
゜9...Amplifier, 5--Speaker, 6; 7"/0 Microphone 4-phone, 10...Time difference meter, 11...Main, 12-3
．． 14.15.16°...branch pipe (5)

Claims (1)

[Claims] The method is characterized in that a sound wave is generated from the inlet gs11L in the buried pipe 1, the arrival time of the sound wave from the inlet end 1a to the outlet end 1b is measured, and the length of the buried pipe is determined from the sound velocity and the arrival time. Buried piping length measurement method.