JPS6257230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the position of a branch pipe connection opening in a gas pipe buried underground.

In gas pipe piping work, after connecting branch pipes to the main pipe buried underground and completing the piping work, the entire inner surface of the main pipe is coated with thermosetting resin to prevent gas leakage. administered.
Therefore, the openings that serve as connections between the branch pipes are closed by this coating film. Therefore, it is necessary to remove the coating film that blocks this opening later. However, since the branch pipe is connected to other branch pipes, the coating cannot be removed from the branch pipe, and must be removed from within the main pipe. However, since the main pipe is buried underground, it is difficult to accurately detect the position of the opening from inside the main pipe.

An object of the present invention is to provide a detection device that solves the above problems.

According to the present invention, there is provided a bogie that runs within a steel pipe whose inner surface is coated with resin, and a
one electrode, a power source that applies an electric field between the electrode and the steel pipe, and two electrodes between the two electrodes and the steel pipe.
An apparatus for detecting an opening in a buried pipe is obtained, which includes a circuit that measures two capacitances and an indicator that operates based on the difference between the two measured capacitances.

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

In FIG. 1, 1 is a main pipe such as a gas pipe buried underground, and is made of a conductor.
An opening 2 is provided in a part of the upper peripheral surface of this main pipe 1, and a branch pipe 3 is connected to this opening 2. Further, a thermosetting resin coating 4 is applied to the entire inner circumferential surface of the main pipe 1, and the opening 2 is covered with the coating 4.

Inside this main pipe 1, a trolley 6 is pulled by a cable 5.
is inserted and advanced along the axis of the main pipe 1. Two electrodes 7 are provided on the trolley 6.

An AC power source 9 is provided to apply an electric field between the electrode 7 and the main pipe 1, and a circuit 8 is provided to measure the capacitance between the main pipe and the two electrodes 7 using this. Figure 2 shows the electrode connections. That is, the main pipe 1 and one electrode 7 are placed on one side of the bridge circuit.
_{A resistor R 1 is} connected to the side opposite to the capacitor C ₁ . Also, on the other side of the bridge circuit, there is a capacitance between main pipe 1 and another electrode.
C ₂ is connected, and a resistor R ₂ is connected to the side opposite to the capacitor C ₂ .
and variable resistor _R3 are connected. 9 is main 1
This is a power source that applies an electric field between the electrode 7 and the two electrodes 7. An amplifier 11 is installed at the output terminals a and b of the bridge circuit.
is connected, and an indicator 12 is connected to its output through a rectifier circuit 10.

In the embodiment, an electric field is applied between the main pipe 1 and the two electrodes 7, the resistor _R3 is adjusted to balance the bridge circuit, and the outputs of the output terminals a and b are set to 0, and the trolley 6 is connected to the main pipe 1. progress inside.

When the trolley 6 advances and comes directly under the opening 2, the capacitance _C1 changes, causing the bridge circuit to become unbalanced and outputs to output terminals a and b. The cart 6 is stopped at this position, and the coating 4 blocking the opening 2 is removed using a drill or heater (both not shown) provided on the cart 6, and the main pipe 1 and the branch pipe 3 are communicated with each other. . A similar operation is performed at each opening 2 while the cart 6 is sequentially advanced to remove the coating 4 blocking each opening 2 and make a hole.

In the above embodiment, the capacitance between the main pipe 1 and the electrode 7 is
Although the position of the opening 2 is detected using the fact that the bridge circuit is unbalanced due to a change in C ₁ , the change in capacitance C ₁ does not necessarily need to be detected by the bridge circuit. For example, if you configure a resonant circuit using _capacitance C ₁ ,
It is also possible to detect the position of the aperture from the change in the resonant frequency accompanying the change in the aperture. That is, the capacity
Any circuit may be used as long as it can detect changes in C ₁ .

As described above, the present invention runs a cart equipped with electrodes inside a steel pipe made of a conductor, and detects the position of an opening by using changes in the capacitance of a capacitor made of the steel pipe and electrodes. If the position can be detected and the cart is equipped with a drill or heater,
In addition to detecting the opening position, coating removal work can be performed efficiently.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main pipe showing the situation when an opening is detected, and FIG. 2 is an electrical wiring diagram. 1... Main pipe (steel pipe), 2... Opening, 3... Branch pipe, 4
...Coating, 5...Cable, 6...Dolly, 7...
Electrode, 8... Circuit, 9... Power supply, 10... Rectifier circuit, 1
1...Amplifier, 12...Indicator.

Claims (1)

[Claims] 1. A truck that runs inside a steel pipe whose inner surface is coated with resin, and two electrodes provided on the truck,
a power source that applies an electric field between the electrode and the steel pipe;
An opening detection device for a buried pipe, comprising a circuit that measures two capacitances between each of the two electrodes and the steel pipe, and an indicator that operates based on the difference between the two measured capacitances. .