JPH11332045A - Method for pulling out cable laid in duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pull out a cable easily from a duct, even if a swollen, expanded or softened part is present in the corrosion-proof layer of a cable laid in a duct by hardening the corrosion-proof layer previously and then pulling the cable, while sustaining the hardened state of the corrosion-proof layer. SOLUTION: Cooling agent in a coolant container 4 is fed into the spiral tubes 7a, 7b, 7c of a cable 1 by means of a pressure pump 3. Then, the chloroprene rubber corrosion-proof layer 9 of the cable 1 is cooled below ice point in the presence of cooling agent in the cable and is hardened through freezing over the entire length including swollen, expanded or softened parts. Subsequently, the cable 1 is pulled out from one end of the duct 2. Since the corrosion- proof layer 9 is frozen and hardened, swollen parts thereof are not dragged into dumpling shapes in the duct 2 and the cable 1 can be pulled out smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pulling a cable laid in a pipeline out of the pipeline.

[0002]

2. Description of the Related Art Past cables laid in a pipeline are:
As they age, they become obsolete and need to be replaced with new cables. In this case, in order to secure an empty pipeline or reuse resources, it is necessary to once pull out the old cable laid in the pipeline out of the pipeline and remove it.

Conventionally, to pull out a cable laid in a conduit, the cable is simply pulled out from one end of the conduit (the conduit opening).

[0004]

However, there is a problem that the above-described simple cable pulling method of the prior art cannot be applied to the following cable laid in a pipeline. In other words, cables that have been laid for many years in underground pipelines have a cable corrosion protection layer (in the case of lead-covered OF cables that were laid from 1955 to the early 40s, a chloroprene rubber corrosion protection layer was used).
Is swollen by rainwater or the like that has flowed into or entered the pipeline;
It is expanded and softened, and even if the cable containing this swollen part is simply pulled out from one end of the pipeline (channel opening),
Due to friction at the time of pulling out between the cable outer surface and the conduit inner surface,
The swollen portion is dragged in the longitudinal direction of the cable to form a portion deformed in a dumpling shape, and even if the cable is further pulled out from such a state, the dumpling-shaped cable portion is caught in the middle of the conduit, and However, if there is a deformation of the duct itself, which is likely to occur in the old duct, the catch of the cable-bundle-like portion becomes remarkable, so that the cable cannot be pulled out from the time when the cable-bundle-like portion is formed. , Could not complete cable pulling.

Therefore, the problems to be solved by the present invention (objects)
The present invention provides a method for pulling out an in-pipe cable, which can be easily pulled out from the pipe even if the cable anticorrosive layer has a swollen; softened portion in the in-pipe cable. It is in.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of pulling out a cable laid in a pipeline, wherein the corrosion protection layer of the cable laid in the pipeline is cured in advance, and the cured state of the cable corrosion protection layer is maintained. While pulling out the cable.

As described above, since the anticorrosion layer of the cable is pre-cured, the cable anticorrosion layer swells. Even if there is an expanded or softened portion, this portion does not become a dumpling when the cable is pulled out, and the cable can be pulled out. It can be performed smoothly.

As a specific means for curing the cable anticorrosion layer, a method of sending a coolant into the cable to freeze-harden the cable anticorrosion layer, flowing an electric current inside the cable, and heating the cable anticorrosion layer by Joule heat at that time. A method of curing is provided.

It is preferable to use a cryogenic refrigerant such as liquid nitrogen as the coolant. The refrigerant is fed into the cable by using a fluid passage or a gap in the cable, so that the temperature of the cable anticorrosion layer can be sufficiently increased. It can be lowered to allow freezing and hardening of the expanded and softened parts. In addition, as a current supply unit, a closed circuit including a plurality of conductors included in a cable is formed, or a closed circuit including a conductor and a metal sheath (shield) is formed, and a current is caused to flow through the closed circuit. By increasing the temperature of the anticorrosion layer by Joule heat generated by the electric resistance of the conductor (metal sheath), it is possible to heat and cure the expanded and softened portion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a cable structure which is an object of a method for pulling out an in-pipe cable according to the present invention, which is composed of a chloroprene rubber anticorrosive lead-coated OF cable. In the figure, 6a, 6b, 6c are conductors, 7a, 7
Reference numerals b and 7c denote spiral pipes serving as oil passages, 8 denotes a lead sheath, and 9 denotes a chloroprene rubber anticorrosion layer. That is, in this cable, three cores each having a conductor 6a, 6b, 6c coated with an insulator are connected to three spiral tubes 7a.
a, 7b, and 7c are twisted through each other, these are covered with a lead sheath 8 so as to obtain an oil-tight state, and a chloroprene rubber anticorrosion layer 9 is provided as an outermost layer.

This chloroprene rubber anticorrosion lead covered OF cable was laid in a pipeline from 1955 to the early 1960s. Since the cable is an old cable that has passed 37 years, the chloroprene rubber anticorrosion layer 9 has swelled; expanded and softened due to infiltration of rainwater or the like into the pipeline.

The chloroprene rubber anticorrosive lead coating O
An embodiment of a method for extracting an F cable will be described with reference to FIG.

Example 1 As shown in FIG. 2, a coolant container 4 storing a cryogenic refrigerant such as liquid nitrogen and a pressure pump 3 are prepared, and one end of a pipe; an end of a cable disassembled at a pipe mouth. Then, the ends of the spiral tubes 7a, 7b, 7c on the cable side are connected to the pressure pump 3 by piping. The end of the cable is preferably closed with a suitable treatment material.

The coolant in the coolant container 4 is supplied by the pressure pump 3 to the spiral tubes 7a, 7b, 7 of the cable 1.
Send into c. This operation is performed until the coolant is fed over the entire length of the cable 1. Then, the chloroprene rubber anticorrosion layer 9 of the cable 1 is cooled below freezing in the presence of the coolant in the cable, and freeze-hardens over the entire length including the swelled; expanded and softened portions. In this case, if the vacuum is drawn from the cable end to the cable end opposite to the coolant sending end of the cable, the coolant injection time can be shortened, and the freeze hardening time can be shortened.

When the chloroprene rubber anticorrosion layer 9 of the cable 1 is freeze-hardened over the entire length in this manner, the cable 1 is pulled out from one end of the conduit; the conduit opening. At this time, since the chloroprene rubber anticorrosion layer 9 is in a freeze-cured state, the swollen portion of the chloroprene rubber anticorrosion layer 9 does not drag in the pipe 2 to form a dumpling, and the cable is smoothly caught without being caught in the pipe. You can now complete the withdrawal.

Embodiment 2 As shown in FIG. 3, a portable power source 5
At one end of the conduit; at the end of the cable disassembled at the conduit opening, any two conductors of the conductors 6a, 6b, 6c or one conductor selected from the conductors 6a, 6b, 6c And the end of the lead sheath 8 to the power supply 5. Also,
At the conduit opening opposite to the power supply connection side, a closed circuit is formed by connecting the selected two conductors to each other or connecting the conductors to the lead sheath 8. And 2 which is part of the closed circuit
An electric current is passed through the conductor or the conductor and the lead sheath, and the cable 1 is heated from the inside by Joule heat at that time. Then, the chloroprene rubber anticorrosion layer 9 is also heated.
Swelling; the chloroprene rubber anticorrosion layer 9 including the expanded and softened portions is hardened over the entire length.

When the chloroprene rubber anticorrosion layer 9 of the cable 1 is hardened over the entire length in this manner, the cable 1 is pulled out from one end of the conduit; the conduit opening. At this time, since the chloroprene rubber anticorrosion layer 9 has already been cured, the swollen portion of the chloroprene rubber anticorrosion layer 9 is not dragged in the pipe 2 to form a dumpling, and the cable is smoothly connected without being caught in the pipe. You can now complete the withdrawal.

[0018]

According to the present invention as described above, in a cable laid in a pipeline, even if the cable anticorrosion layer has a swelling; expansion and softening portion, it can be easily pulled out from the pipeline. It is possible to achieve an intended problem (object) of providing a possible method of pulling out a cable laid in a pipeline.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a chloroprene rubber anticorrosion lead-coated OF cable targeted for a method of pulling out an in-pipe cable according to the present invention.

FIG. 2 is a view showing a first embodiment of a method of pulling out a cable laid in a conduit according to the present invention, and is an explanatory diagram of a method of pulling out the chloroprene rubber anticorrosion lead-coated OF cable of FIG. 1 by freeze-hardening.

FIG. 3 is a view showing a second embodiment of the method of pulling out the cable laid in the conduit according to the present invention, and is an explanatory view of the method of pulling out the chloroprene rubber anticorrosion lead-coated OF cable of FIG. 1 by heating and curing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable; chloroprene rubber anticorrosion lead-coated OF cable 2 conduit 3 pressure pump 4 coolant container 5 power supply 6a, 6b, 6c conductor 7a, 7b, 7c spiral tube 8 lead sheath 9 chloroprene rubber anticorrosion layer

Claims (3)

[Claims] 1. A method of pulling out a cable laid in a conduit, wherein the corrosion prevention layer of the cable laid in the conduit is cured in advance, and the cable is pulled out while maintaining the cured state of the cable corrosion prevention layer. 2. The method according to claim 1, wherein a cooling agent is fed into the cable to freeze-harden the anticorrosive layer. 3. The cable anticorrosion layer is heated and cured by Joule heat at that time when an electric current is applied to the inside of the cable.
The method for pulling out the cable laid in the pipeline as described in the above.