JPH0360059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the state of damage to the coating layer of a coated metal pipe that is buried underground and is constructed by covering the metal pipe with an electrically insulating coating layer, Concerning a method for detecting corrosion areas.

In the prior art, in order to detect a corroded area of a coated metal pipe buried underground, vertical holes are drilled at multiple locations along the pipe axis of the coated metal pipe to expose the coated metal pipe.
It detects the current flowing through the metal tube. Such prior art requires a great deal of labor to excavate a vertical hole, resulting in poor workability.

An object of the present invention is to provide a method that allows easy detection of corrosion areas in coated metal pipes.

FIG. 1 is a sectional view of one embodiment of the present invention.
A covered metal pipe 51 for transporting fluid such as gas fuel is buried in the ground 50. The coated metal tube 51 is constructed by covering the outer periphery of a steel tube, which is a metal tube, with a coating layer made of an electrically insulating material, such as a synthetic resin. In order to use the gas fuel transported in the coated metal pipe 51 in each house, the coated metal pipe 51 is provided with branch pipes 52a to 52e spaced apart from each other in the tube axis direction. Branch pipe 52a
~52e may be electrically isolated from the steel pipe of the coated metal pipe 51 by an electrically insulating pipe joint or other structure. These branch pipes 52a to 52e
Intra-pipe wire passing tools 53 and 54 are inserted into two adjacent branch pipes 52a and 52b. The tip portions 53a, 54a of the pipe wire passing tools 53, 54 can come into contact with the inner peripheral surface of the steel pipe of the coated metal pipe 51. An ammeter 55 is connected to the pipe wire passing tools 53 and 54. This ammeter 55 measures the current value and direction of the current. Note that when detecting this corrosion area, if a galvanic anode such as magnesium or a DC power source is connected to the coated metal tube 51 to flow a corrosion protection current, the galvanic anode and the DC power source are connected to the coated metal tube 51. It is cut off from the steel pipe of pipe 51.

After the measurement by the ammeter 55 is completed in this way, the pipe wire passing tools 53 and 54 are inserted into the branch pipes 52b and 52c, respectively, and the measurement is performed by the ammeter 56 in the same manner. Similarly, for the branch pipes 52c, 52d; 52d, 52e, ammeters indicated by reference numerals 57, 58 are arranged in the same manner, and measurements are carried out using the in-pipe wire passing tools 53, 54.

When the coating layer of the coated metal pipe 51 is damaged and the outer circumferential surface of the steel pipe is in contact with the ground 50 at a damaged location 59, as shown in FIG.
The current value at the measurement position by the ammeters 55 to 58 along the tube axis direction of No. 1 and the direction of the current change. The coated metal tube 5 approaches the damaged location 59.
The corrosion current flowing through the steel pipe 1 increases, and the direction of the current is opposite on both sides of the damaged location 59. In this way, from the current measurement results by ammeters 55 to 58,
The damage location 59 can be known.

FIG. 3 shows an in-pipe wire passing tool 53 according to an embodiment of the present invention.
FIG. The main wire 1 has a relatively large elastic force, is made of piano wire, etc., and is configured by winding the piano wire in a spiral shape, and in its natural state
It may have a length of 20 meters or more. The end of the auxiliary wire 2 is fixed to the end of the main wire 1. A guiding member 3 is fixed to the other end of the auxiliary wire 2 . The auxiliary wire rod 2 can be bent by the weight of the guiding member 3 and has a smaller elastic force than the main wire rod 1. The auxiliary wire 2 is also made of piano wire or the like, and is wound spirally. The length of this auxiliary wire 2 may be, for example, about 10 cm.

FIG. 4 is a perspective view of the vicinity of the guide member 3. This guide member 3 has a square surface 4 when viewed from the free end side (left side in FIG. 4), that is, from the front, and is partially formed into a prismatic shape. The proximal end portion 21 of the guiding member 3 has a tapered shape and is fixed to the auxiliary wire 2 as described above. This guide member 3 is made of a material such as steel. By applying a rotational force to the main wire 1, stress against twisting is accumulated in the pipe, and when the load drops below a certain level, it can rotate and vibrate due to the reaction.
Can withstand reuse.

Referring to FIG. 5, in the upper part of the underground pipe 5,
Chi 6 is connected. An above-ground standpipe 8 is connected to this chi 6 from a service pipe 7, and gas is supplied to a house 9. A valve 10, an elbow 11, a pipe joint 12, and the like are interposed between the lead-in pipe 7 and the standpipe 8. In-pipe wire passing device 5 according to the present invention
According to No. 3, the guide member 3 can enter the pipe 5 from the standpipe 8 through the lead-in pipe 7.

FIG. 6 shows the state in which the pipe wire passing tool enters the chi 6 from the lead-in pipe 7. The auxiliary wire 2 is deflected by the gravity of the guide member 3, so that the guide member 3 is easily allowed to advance from the chi 6 into the tube 5. When the auxiliary wire 2 hangs down due to the gravity of the guide member 3, by pushing the main wire 1 while rotating the main wire 1 around its axis, the guide member 3 rotates and vibrates. Tsutsu tube 5
can enter inside.

Further, as shown in FIG. 7, the end of the tube 14 is closed with a plug 15.
Even when the branched pipe 16 is connected to the vicinity of the pipe 5, the intra-pipe wire passing device 53 according to the present invention can be introduced from the pipe 14 to the pipe 16 as shown by the arrow 17, and vice versa. From tube 16, tube 14 can be entered as indicated by arrow 18.

The free end surface 4 of the guiding member 3 is square, and therefore, the corner portion 4a of the free end surface 4 is likely to get caught in a step at an elbow, a tee, a pipe joint, etc. When this corner portion 4a hits a step inside the pipe, it jumps due to the elastic force of the auxiliary wire 2 and the main wire 1. This allows the guide member 3 to enter the pipe while overcoming the step.

According to experiments conducted by the inventor of the present invention, when wires were threaded into pipes of various structures using the pipe wire threading tool 53 of the illustrated embodiment, wires could be threaded with approximately 92 to 93% probability. It was confirmed that the success rate was extremely high, and the time required to install the line was relatively short.

The in-pipe wiring tool 53 having the above-described configuration is capable of passing not only underground gas pipes, but also pipes installed in other building walls and other sealed areas.
Alternatively, it may also be an exposed tube. The main wire 1 may be constituted by a coil spring having an inner and outer dual structure wound in opposite directions.

In order to ensure that only the tip 53a (see FIG. 1) of the in-pipe wire passing tool 53 comes into contact with the inner circumferential surface of the steel pipe of the coated metal tube 51 to accurately detect the corrosion current, as shown in FIG. The main wire 1 and the like may be covered with an insulating tube 60 made of a flexible and electrically insulating material such as synthetic resin at a portion other than the vicinity of the guide member 3, which is the tip 53a, so that the main wire 1 and the like can be covered.

The pipe wire passing tool 54 has the same configuration as the pipe wire threading tool 53.

According to the present invention, the pipe wire passing tools 53 and 54 are not limited to the configurations described in connection with FIGS. 3 to 7;
It may have other configurations.

As described above, according to the present invention, a corroded area can be detected based on the value and direction of the current by inserting an intra-pipe wiring tool into a coated metal pipe buried underground, thereby improving work efficiency. is improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a graph showing measurement results by ammeters 55 to 58, and FIG. 3 is a pipe wire passing device 53 of an embodiment of the present invention.
4 is a perspective view of the vicinity of the guiding member 3, FIG. 5 is a piping diagram for explaining the wiring work, FIG. 6 is a sectional view showing the wiring state near the chi 6, and FIG. 7 2 is a sectional view for explaining the operation of passing wires into the tubes 14 and 16. FIG. 51...Coated metal pipe, 52a-52e...Branch pipe, 53, 54...In-pipe wire passing tool, 55-58...
Ammeter.

Claims (1)

[Claims] 1. Insert a pair of electrically conductive wire-through devices into a coated metal tube that is buried underground and has an electrically insulating coating layer, and insert each tube wire-passing device into the tube axis of the inner circumferential surface of the coated metal tube. A method for detecting a corroded position in a coated metal pipe, the method comprising: contacting different positions in different directions, connecting an ammeter to a wire passing through the pipe, and detecting a current value and a direction in which the current flows.