JPS6219693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the presence or absence of a leak in a conduit for transporting various fluids such as city gas, natural gas, oil, or water and sewage.

More specifically, with both ends of the inspection target section of the conduit closed, a device for detecting the concentration of gas flowing into the inspection target section from the leakage point is inserted into the inspection target section, and the detection device detects the concentration of gas flowing into the inspection target section from the leak point. This invention relates to improvements in methods for detecting the presence or absence of leakage based on information.

Conventionally, a sealed part is formed by attaching a case to the outside of the part to be inspected, a detection gas is supplied under pressure to the sealed part, and the detection gas flowing into the part to be inspected from the leakage point is introduced into the part to be inspected. [For example, see Japanese Patent Application Laid-Open No. 50-99188].

However, since it is necessary to form a sealed part, it requires an extremely large amount of labor and time to inspect the entire length of a long inspection target part, for example, several tens of meters or more, making it practically unapplicable. However, there were drawbacks in terms of workability, cost, and scope of application.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improvement that allows accurate leakage testing to be performed without much effort or time, even if the part to be tested is long.

The characteristic means of the present invention is to reduce the pressure inside the pipe of the part to be inspected, to cause air that naturally exists outside the part to be inspected to flow into the part to be inspected from the leakage point, and to move the detection device into the part to be inspected. While moving the device, the concentration of gas components in the air is detected by the detection device, and the presence or absence of leakage is detected based on the presence or absence of air flowing in from the outside.The operation and effect are as follows.

In other words, air that naturally exists outside the pipe is caused to flow into the area to be inspected from the leak point due to a decrease in the pressure inside the pipe.
Since the detection device is moved within the part to be inspected to detect the presence or absence of incoming air, regardless of the length of the part to be inspected, the aforementioned Leak testing can be performed with much less effort and time than conventional techniques.

In addition, by reducing the internal pressure of the part to be inspected, the gas that was originally present in the part to be inspected can be sufficiently exhausted, so when the concentration of gas components in the air is detected by the detection device, the gas that was originally present in the part to be inspected can be removed. Accurate detection can be performed without any adverse effects caused by

As a result, even if the part to be inspected is long, the work can be done with extremely little effort and time, and the presence or absence of leakage can be detected accurately, resulting in conduit leaks that are excellent in terms of workability, cost, application range, and detection accuracy. A detection method was obtained.

Next, examples will be shown.

As shown in Fig. 1A, a portion of the existing conduit 1 for city gas transportation is cut out at both ends of the inspection target section 1a, and temporary bypass piping 1b is installed as necessary to allow fluid transportation to continue. The wire passing object 2 inserted from one end side of the inspection target part 1a
is moved to the other end by supplying pressurized air from a compressor 4 connected to a launcher 3 attached to one end of the part to be inspected 1a, and the reel 5
A tow rope 6 such as a wire that is let out from the inspection target portion 1a is passed through the inspection target portion 1a.

Next, as shown in FIG. 1B, a trolley-equipped oxygen gas detection device 7 connected to the tow rope 6 instead of the object 2 is inserted from one end side of the inspection target portion 1a,
Then, a pressure reducing device 9 is connected to the launcher 3 in place of the compressor 4, a cup 11 is connected to the inspection device 7 insertion side of the inspection target portion 1a, and a nitrogen gas supply device 8 is connected to the cup 11. Then, by cooperation of the pressure reducing device 9 and the nitrogen gas supply device 8, city gas is discharged and nitrogen gas is filled into the inspection target area 1a, and then,
The nitrogen gas supply is stopped to reduce the pressure inside the tube of the inspection target portion 1a, and maintain the reduced pressure state. Furthermore, while the oxygen gas detection device 7 is moved toward the other end side of the inspection target portion 1a by the action of the winding device 5 in the pressure-reduced state, oxygen is sent from the detection device 7 by wired method or wireless method. The detected concentration value is recorded manually or automatically and in correspondence with the moving distance of the detection device 7.

Note that the recorder may be built into the detection device 7.

As a result, if a leak exists, as shown in Figure 2, when the detection device 7 reaches the leak, the oxygen concentration begins to increase due to the inflow of air, and from this fact it is possible to know the presence or absence and location of the leak. This is possible. When a leakage point is found in this way, the leakage detection work is temporarily interrupted, the leakage point is repaired, and the leakage detection work is resumed after the repair. Once the repair is completed, the existing conduit 1 is reconnected as before, and all work is completed.

The method of the present invention can be applied to conduits for various fluids such as city gas, natural gas, petroleum, water and sewage.

In place of the oxygen gas detection device 7, for example, gas chromatography or a moisture meter that detects nitrogen gas can be used. Any device 7 may be used as long as it detects the concentration of . Of course, if nitrogen gas is to be detected, it is sufficient to simply reduce the pressure inside the pipe of the part 1a to be inspected, even if other specific substances are to be detected without filling with nitrogen gas as described above. be.

Furthermore, when it is desired to detect only the presence or absence of leakage, such as when it is desired to know whether or not a conduit needs to be replaced, there is no need to check the moving distance of the detection device 7.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the conduit leak detection method according to the present invention, and FIG. 1A and B are explanatory diagrams showing the work procedure, and FIG. 2 is a graph showing the detection results. 1... Conduit, 1a... Part to be inspected, 7... Detection device.

Claims (1)

[Scope of Claims] 1. With both ends of the inspection target section 1a of the conduit 1 closed, a device 7 for detecting the concentration of gas flowing into the inspection target section 1a from the leakage point is installed inside the inspection target section 1a. This is a method of detecting the presence or absence of leakage based on information from the detection device 7, in which the pressure inside the pipe of the inspection target section 1a is lowered to leak air that naturally exists outside the inspection target section 1a. The concentration of gas components in the air is detected by the detection device 7 while moving the detection device 7 within the inspection target portion 1a, and the concentration of gas components in the air is detected. A conduit leak detection method that detects the presence or absence of a leak based on its presence or absence. 2. The leakage position is detected based on the relationship between the position of the detection device 7 with respect to the inspection target portion 1a and changes in information from the detection device 7. Method.