JPH03132702A - Tube failure point search method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for searching for a failure point in a tube, and is capable of accurately inspecting a failure point in a tube used for transporting pressurized fluid or objects. It is. It is particularly useful when the tube except for its terminal end is inside an underground conduit or structure.

<Prior Art> Tubes are generally used to transport fluids. For example, liquids such as water and oil.

Powder and gas are sent through it.

Furthermore, as a unique embodiment, objects (solids) may be passed through the tube. For example, when installing an optical fiber, the optical fiber may be passed through a tube (Japanese Patent Laid-Open No. 5
9-104607 (“Optical fiber cable installation method and device”). This technique will now be explained with reference to FIG. In the figure, a tube 1 has been installed in advance inside an underground conduit or structure while being towed by a tow rope.

A hollow feed head 2 is connected to the tube 1,
Compressed air is supplied into the feed head 2 by a compressor 3.

The opening of the inlet 2a of the feed head 2 is narrow, and the opening of the outlet 2a is narrow.
Since the opening b is wide, compressed air flows inside the tube 1 as shown by the arrow in the figure. For this reason, the reel (
The optical fiber 4 fed out from the feed head (not shown) and inserted into the feed head 2 is exposed to a flow of compressed air, receives a carrying force from the air flow, and is sent into the tube 1 according to this air flow. . At this time, the feeding speed of the optical fiber 4 is controlled by the rotation of drive wheels 5a and 5b that feed the optical fiber 4 while holding it therebetween. Of course, the flow rate of the compressed air is faster than the feed rate of the optical fiber 4. In this way, the optical fiber 4 can be installed inside the existing tube 1 using compressed air.

<Problems to be solved by the invention> In tubes used for transporting fluids and objects,
It is required that there be no pinholes or "squashing". Therefore, inspection is performed for the presence of defects and deformations such as pinholes and crushing.

If the entire length of the tube is exposed to the outside, it is possible to detect failures (pinholes or collapses) using compressed air or ultrasound. In other words, if compressed air is sent in from one end of the tube and the air pressure is tested at the other end, the presence of a pinhole will be detected because the tested air pressure will drop if there is a pinhole.

Furthermore, if a liquid with high surface viscosity is applied to the surface of the tube, compressed air will come out of the pinhole and the liquid will become bubbles and expand, making it possible to pinpoint the location of the pinhole.

On the other hand, if ultrasonic receiving probes are attached to the tube at multiple locations along its length, it is possible to detect the ultrasonic waves generated when the air pressure changes due to air leaks and to identify the location of the failure.

If the entire length of the tube is exposed, tube failure can be detected using the method described above, but in reality, tube failure cannot be inspected when most of the tube, except for both ends, cannot be observed from the outside.

For example, in the technique shown in Fig. 4, tube 1 is laid first as described above, but before the optical fiber 4 is inserted, unreasonable stress is applied to tube 1 in the laying route, resulting in pinholes. If this happens, the optical fiber 4 cannot be pneumatically transported (or it will become too thin). Therefore, it is required to search for failures in the tube 1 before pneumatically feeding the optical fiber 4, but there is currently no technology for conducting a preliminary inspection.

In view of the above-mentioned prior art, the present invention provides a tube failure point search method that can search for a failure point in a transportation tube.

Means for Solving the Problems〉 The method of the present invention for solving the above problems is a method for searching for a failure point in a tube through which objects to be transported, such as fluids or objects, are transported. From the response characteristics of the signal received by the receiver outside the tube,
It is characterized by searching for failure points in tubes.

Function and Principle There are various methods for transporting the radio transmitter within the tube, but the principle and function of the present invention will be explained based on the case of transport using compressed air.

If a wireless signal is received at a predetermined position while a wireless 4M generator is sent into the tube using compressed air from the end of the tube, a time response characteristic in which the level of the received signal changes over time is obtained. At this time, once the installation route of the tube, the length of the tube, the shape of the wireless transmitter, the pressure of the compressed air, and the material of the tube are determined, the time response characteristics of a certain pattern are determined.

Therefore, if there is a leak due to a collapse or pinhole in the middle of the tube, the running condition of the wireless transmitter, which is fed into the tube and is driven by the flow of compressed air, will be
Since the condition is different from running in a tube without failure, receiving =
The time response characteristics of the signal become different from the normal characteristics. Based on this difference in response characteristics, it is possible to determine whether or not there is a tube failure and to identify the location of the failure.

If the receiver is installed close to the side of the tube where the radio transmitter is sent, the radio transmitter will gradually move away from the receiver as it moves through the tube, making it difficult to receive it. The signal level will gradually become weaker as time passes. Therefore, by comparing the time response characteristics of the received signal level when the tube is normal and the time response characteristics obtained when the tube is suspected of being collapsed or leaking, we find that the characteristics are different and we are searching for failures based on these characteristics. Be able to do it. In other words, in the event of a failure, the transfer speed suddenly slows midway due to leakage, or the transmitter becomes unable to move due to tube collapse, and the received signal level does not attenuate over time. In this way, the failure point of the tube can be identified from the time at which a phenomenon different from the normal state occurs.

To identify the degree of tube bulge, the size and shape of the transmitter can be changed as appropriate. Also, the degree of tube leakage can be identified from the degree of change in the attenuation coefficient of the received signal.

Conversely, if this method is used in a normal tube system, changes in the inner diameter of the tube can also be detected. Alternatively, the tube installation route can also be specified from the time response characteristics of the received signal.

Example of implementation Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. A tube 1 shown in both figures (in which an optical fiber will be installed later).The radio transmitter 10 has a cylindrical shape and has an antenna at its tail, and emits an R-free signal.Radio transmitter The container 10 is inserted into one end of the tube 1 (the left end in the figure), and the compressor 20 sends compressed air into the tube 1.For this reason, the device 10 is pushed by compressed air and moves inside the tube 1 at the other end. (the right end in the figure).The receiver 30 is installed near the compressor 20.

When the tube 1 is laid along a straight route as shown in FIG.
As shown in the figure (bl), it decays linearly over time.

Next, if there is a crushed part 1a in the middle of the tube 1 as shown in Figure 2 (al), the wireless transmitter 10 will hit the crushed part and will not be able to proceed beyond it, so see Figure 2 tb) A phenomenon was observed in which the level of the received signal at the receiver 30 no longer attenuates after a certain time, as shown in FIG.

Since the speed at which the wireless transmitter 10 moves inside the tube 1 as it is pushed by the compressed air has been determined in advance through experiments and theoretical formulas, the time t until the phenomenon in which the received signal level no longer attenuates occurs is detected. By doing so, the position of the crushed portion 1a can be specified.

In this embodiment, the tube 1 is a polyethylene tube with an outer diameter of 10 mm and an inner diameter of 8 mm, and a length of 300 m, and the wireless transmitter 10 has an outer diameter of 6 mm and a length of 30 mm.
It is cylindrical in shape and has a 20mm long antenna on its tail.

On the other hand, the compressed air C sent into tube 1 on three sides is 3k
g/c i. FIG.
It took 25 minutes to open the door to the far right. Also the second
In the case shown in Figure (bl): The time t until the phenomenon t'' in which the received signal level no longer attenuates occurs was 5 minutes.

From this, it was possible to identify the collapse at a position I° of the collapsed portion IX of the tube 1, 100 m from the left end of the tube 1.

Next, a second embodiment of the present invention will be explained with reference to FIG. As shown in Figure 3, the C-tube 1 has a hole 1b due to trauma, and air leaks from this hole 1b; the compressor 20 sends compressed air into the tube 1, and radio transmission is performed. When the device 10 is moved within the tube 1, the time response characteristic of the signal received by the received signal 30 is as shown in FIG. As can be seen from Fig. 3 (bl), the attenuation rate of the received signal level becomes small from the middle. This is because the moving speed of the wireless transmitter 10 becomes slower when it passes through the hole 1b. It was possible to identify the position of the hole 1b where the air leak occurred from the time at which the level attenuation rate changed.In this case, the signal level attenuation rate changed 5 minutes after the wireless transmitter 10 started moving. It was possible to estimate that the hole 1b was located 100 m ahead from the left end of the tube 1.

Furthermore, even if the tube route has bends or vertical sections, if the time response characteristic pattern of the received signal in a non-fault condition is clarified in advance experimentally or logically, the same result as above can be achieved. In principle, it is possible to search for tube failure points and pinpoint the failure location.

In order to determine the degree of collapse of the collapsed portion formed in the middle of the tube, the size and shape of the transmitter may be changed as appropriate for inspection.

The method of the present invention can be used even if the middle of the tube is not exposed.
Inspection work can be done using only the end of the tube.

In each of the embodiments described above, the wireless transmitter is sent by compressed air, but it may be sent by other means. Tubes used to convey fluids or objects can also be inspected by the method of the present invention.

<Effects of the Invention> As described above, according to the present invention, it is possible to search for a failure point in a tube from the time response characteristics of the signal level received by a receiver while moving a wireless transmitter within a tube. Therefore, the following effects are achieved.

(1) Even if the middle part of the tube is not exposed to the outside at all, as long as the terminal end is exposed, it is possible to identify the failure point or location of the tube, which could not be determined.

(2) The inspection method is simple and can be carried out easily, and the inspection cost is low.

(3) If the size and shape of the wireless transmitter are appropriately selected, the degree of bulge can be detected.

[Brief explanation of the drawing]

Figures (a) and 2 (al are block diagrams showing the first embodiment; Figures 1 (b) and 2 (fbl) are characteristics showing the time response of the received signal level in the first embodiment. Figure 3 (al is a configuration diagram showing the second embodiment, Figure 3 (bl is a characteristic diagram showing the time response of the received signal level in the second embodiment), Figure 4 is an optical fiber connected to a tube. It is a configuration diagram showing a feeding device. In the drawing, 1 is a tube, 10 is a wireless transmitter, 20 is a compressor, and 30 is a receiver. b) Receiving (b) (b) Receiving time

Claims (2)

[Claims] (1) A method of searching for a failure point in a tube through which a fluid or object is passed through, in which a wireless transmitter is moved within the tube from one end of the tube to the other while transmitting a wireless signal, A method for searching for a failure point in a tube, comprising: receiving a wireless signal transmitted from a wireless transmitter with a receiver provided outside the tube, and searching for a failure point in the tube from the response characteristics of the received signal. (2) A method of searching for a failure point in a tube in which compressed air is sent and circulated inside, and an optical fiber is sent inside by being exposed to this air flow and receiving a carrying force from the air flow. , a wireless transmitter while transmitting a wireless signal,
The radio signal is transmitted from one end of the tube to the other by compressed air, and the radio signal sent from the radio transmitter is received by a receiver installed outside the tube, and the response characteristics of the received signal are measured. A tube failure point search method characterized by searching for a tube failure point from.