JPH0261103B2 - - Google Patents

Description

[Detailed description of the invention]

In order to detect a synthetic resin pipe buried underground from the outside, the present invention provides an electric wire close to the underground pipe, supplies a high frequency current to this electric wire, and detects the underground underground pipe from the outside. This invention relates to a connection structure for underground pipe electric wires used to detect the position of pipes. Electric wires are laid along the underground pipes, which are made of synthetic resin such as polyethylene, so that the locations of the pipes for transporting fluid can be detected from the ground surface. Conventional electric wires used for this purpose have an electrically insulating synthetic resin coating layer formed on the core wire, and the core wire is attached to a steel pipe or metal pipe joint connected to a polyethylene pipe, etc. by thermite welding, etc. connected by.
In such prior art, the core wire corrodes and breaks at the connection point between the core wire and the steel pipe or metal pipe joint. In particular, since the core wire is generally made of copper, the connection points tend to corrode due to the formation of microcells made of dissimilar metals.
In addition, if the resistance at the connection point is low, and therefore a minute DC current flows between the steel pipe or iron pipe joint and the core wire, and the coating layer of the wire is damaged, the damage will occur at the damaged point. Current flows from the core wire into the ground at a high current density, and as a result, the core wire tends to break at locations where the coating layer is damaged. An object of the present invention is to provide a wire connection structure that ensures electrical connection over a long period of time. In the present invention, an electric wire 7 is arranged along a synthetic resin underground pipe 2, a metal pipe member 3 is connected to the underground pipe 2, an electric wire is wound around the pipe member 3, The outer periphery of the wound electric wire 7 is elastically wrapped and pressed with a belt 10 made of an organic polymer material, and the electric wire 7 is composed of a core wire 12 coated with an organic polymer material. This electrical wire connection structure for synthetic resin tubes is characterized in that the specific resistance of the organic polymer material of the electrical wire 10 and the electrical wire 7 is approximately 10 Ω·cm or more and approximately 50,000 Ω·cm or less. Further, in the present invention, an electric wire 7 is arranged along a synthetic resin underground pipe 2, a metal pipe member 3 is connected to the underground pipe 2, and the electric wire 7 is wound around the pipe member 3. A paste made of an organic polymer material is attached to the electric wire 7 and the tube member 3 in the vicinity of the coiled electric wire 7, and the volume resistivity of this paste is 10 ^-1 to ^{10 2} Ωcm. is composed of a core wire 12 coated with an organic polymer material, and the specific resistance of this organic polymer material is approximately
This is a connection structure for electrical wires for underground pipes, characterized by a resistance of 10Ω・cm or more and approximately 50000Ω・cm or less. FIG. 1 is a simplified cross-sectional view of one embodiment of the invention. Polyethylene pipes 1 and 2 made of synthetic resin, such as polyethylene, are buried underground and are connected to a steel pipe 4 by a pipe joint 3 made of metal, such as steel. The steel pipe 4 is connected by a steel pipe joint 5 to a steel pipe 15 for connecting a meter (not shown). Fluid such as city gas from the polyethylene pipe 1 is made available for use via a polyethylene pipe 2, a pipe fitting 3, a steel pipe 4, and a pipe fitting 5, and a gas meter. The polyethylene pipes 1, 2 are fitted with electrical wires 6, 7, the ends of which are connected at a connection point 8 to a pipe fitting 3 in accordance with the concept of the invention. When high frequency power is supplied between the electric wire 6 and the steel pipe 15 by the high frequency power supply 9, the electromagnetic field generated by the electric wires 6 and 7 is detected at the earth's surface. Thereby, the positions of the polyethylene pipes 1 and 2 buried along the electric wires 6 and 7 can be detected from the ground surface. FIG. 2 is a front view of the vicinity of the connection point 8, and FIG. 3 is a sectional view taken from the cutting area - in FIG. The end of the electric wire 7 is wound around the outer periphery of the pipe fitting 3 multiple times (for example, five times). The outer periphery of the wound portion 7a of the electric wire 7 is elastically pressed by a belt 10 made of a conductive organic polymer material. Both ends of the belt 10 are connected by a connecting means 11. FIG. 4 is a cross section of the electric wire 7 at right angles to the axis. The electric wire 7 is constructed by covering a core wire 12, which is made up of a plurality of twisted single wires made of copper, iron, etc., with a coating layer 13 made of a conductive organic polymer material. The electric wire 7 is flexible. The compositions of the belt 10 and the coating layer 13 may be the same, and may be made of, for example, a material in which carbon powder or metal powder is mixed into synthetic or natural rubber such as polyethylene. The specific resistance of this coating layer 13 is approximately 10
It is Ω·cm or more and about 50,000 Ω·cm or less, preferably 100 Ω·cm. The belt 10 and coating layer 13 having specific resistance in such a range are made of 100 parts by weight of chloroprene rubber or natural rubber, etc.
This can be achieved by adding 50 to 60 parts by weight of acetylene carbon. If the specific resistance of the coating layer 13 is less than about 10 Ωcm, the mixing ratio of carbon powder or metal powder will be too large compared to the amount of synthetic resin or rubber, resulting in poor flexibility and Manufacturing becomes difficult. Further, if the specific resistance of the coating layer 13 exceeds about 50,000 Ω·cm and the insulation becomes high, it becomes impossible to detect the electric wire 7 if it is cut. The core wire 12 is not connected to the pipe fitting 3 by welding or the like.Since the core wire 12 is not connected to the pipe joint 3 by welding or the like, a minute direct current flows through the core wire 12.
Therefore, even if the coating layer 13 is partially damaged, current is prevented from flowing from the core wire 12 into the ground at a high current density, and the current is prevented from flowing into the ground from the core wire 12.
2 breakage can be avoided. Since the electric wire portion 7a wound around the pipe joint 3 is elastically pressed by the belt 10, its coating layer 1
3 is crushed. Therefore, the coating layer 13 is in surface contact with the outer peripheral surface of the pipe fitting 3, and the coating layer 1
3 is pressed, the resistance decreases.
The reduced resistance value can be set to a preferable resistance value that allows the high frequency power from the high frequency power supply 9 to pass therethrough and prevents a minute direct current from passing therethrough. FIG. 5 is a front view of the vicinity of the connection point 8 of another embodiment of the present invention. In this embodiment, the electric wire 7 is wound around the pipe fitting 3 in the same manner as in the previous embodiment, but what should be noted is that near the wound portion 7a, the electric wire 7a and the pipe fitting 3 are A paste 14 consisting of a conductive organic polymeric material is applied. As yet another embodiment of the present invention, the outer periphery of the paste 14 shown in FIG.
The elastic pressing may be performed using a belt having a configuration similar to the belt 10 shown in the figure. The experimental results of the inventor of the present invention will be described. The outer diameter of the pipe joint 3 is 58 mmφ. The core wire 12 has a nominal cross-sectional area of 2 mm ²
The outer diameter of the coating layer 13 is 4.4 mm.
The electric wire 7 having a diameter of φ is wound around the pipe joint 3 five times as shown in FIGS. 2 and 3, and the core wire 12 and the pipe joint 3 are not connected. The length of wire 7 is 80cm
The resistance between the core wire 12 and the pipe joint 3 was 60Ω in the initial state of tightening with the belt 10, and then changed to 32Ω and stabilized. In the example shown in Figure 5, in which only 50 g of Paste 14 was used, the experimental results shown in Table 1 were obtained.

[Table] Here, the electric wire 7 is 80 cm long, and the resistance is the resistance between the core wire 12 of the electric wire 7 and the pipe joint 3. The resistance value depending on the amount of sample paste No. 1 used was as shown in Table 2.

[Table] As described above, according to the present invention, corrosion between electric wires and conductors can be avoided underground, and a reliable connection can be achieved over a long period of time. In particular, in the present invention, the electric wire 7 is arranged along the underground pipe 2 made of synthetic resin, and the underground pipe 2 is connected to a pipe member such as a metal pipe joint or a steel pipe. An electric wire 7 is wound around the outer periphery of this tube member 3, and the outer periphery of the wound electric wire 7 is elastically wrapped and pressed with a belt 10 made of an organic polymer material.
The organic polymer material that is the material of the belt 10 and the organic polymer material that coats the core wire 12 of the electric wire 7 have a specific resistance of about 10 Ω·cm or more and about 50000 Ω·cm or less. Therefore, the electric wire 7 and the pipe member 3 can generate a high-frequency electromagnetic field sufficient to detect the position of the underground pipe on the ground, and the core wire 12 of the electric wire 7 can be connected to the pipe member 3. Since it is not connected by welding etc., the core wire 1
Even if the coating layer 13 of the organic polymer material covering the core wire 2 is partially damaged, current is prevented from flowing into the ground from the core wire 12 at a high current density, and the core wire 12 is prevented from being cut. It can be avoided. Furthermore, according to the present invention, a paste made of an organic polymer material is adhered to the electric wire 7 and the tube member 3 in the vicinity where the electric wire 7 is wound, and the volume resistivity of this paste is 10. ^-1 to ¹⁰² Ωcm, it is possible to form a high-frequency electromagnetic field sufficient to detect the position of the underground pipe on the ground, and in this case, the electric wire 7 is also Since it is not connected to the tube member 3 by welding or the like, the core wire 12 is prevented from being disconnected.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a state in which an embodiment of the present invention is applied, FIG. 2 is a front view of the vicinity of the connection point 8 in FIG. 1, and FIG. 4 is a sectional view taken at right angles to the axis of the electric wire 7, and FIG. 5 is a front view of another embodiment of the present invention. 1... Polyethylene pipe, 6, 7... Electric wire, 10
... Belt, 12 ... Core wire, 13 ... Covering layer, 1
4...Paste.

Claims (1)

[Claims] 1. An electric wire 7 is arranged along a synthetic resin underground pipe 2, a metal pipe member 3 is connected to the underground pipe 2, and the electric wire is wound around the pipe member 3. The outer periphery of the wound electric wire 7 is elastically wrapped and pressed with a belt 10 made of an organic polymer material, and the electric wire 7 is composed of a core wire 12 coated with an organic polymer material. A connection structure for a synthetic resin pipe electric wire, characterized in that the specific resistance of the organic polymer material between the belt 10 and the electric wire 7 is about 10 Ω·cm or more and about 50000 Ω·cm or less. 2 An electric wire 7 is arranged along a synthetic resin underground pipe 2, a metal pipe member 3 is connected to the underground pipe 2, the electric wire 7 is wound around the pipe member 3, and the electric wire 7 is wound around the pipe member 3. A paste made of an organic polymer material is attached to the wound electric wire 7 and the tube member 3, and the volume resistivity of this paste is 10 ^-1 to ^{10 2} Ωcm, and the electric wire 7 is attached to the core wire 12. is coated with an organic polymer material, and the resistivity of this organic polymer material is approximately
A connection structure for electrical wires for underground pipes, characterized by a resistance of 10Ω・cm or more and approximately 50000Ω・cm or less.