JPH0488179A - Method for protecting electrolytic corrosion of existing buried pipe - Google Patents

Abstract

PURPOSE:To protect the electrolytic corrosion of an existing buried pipe in a short time without widely digging a road by inserting an electrode having a lower standard electrode voltage than the pipe from a work hole and fixing the electrode to the pipe with a lead wire. CONSTITUTION:A work hole H having about 11 cm diameter is bored in a road Rd directly above an existing buried pipe 10 orthogonally to the pipe 10. The distance between the holes H is controlled to about 20 m, and the ground is dug deeper than the pipe 10. An electrode hole h is slightly obliquely formed at the bottom of the hole H. When the pipe 10 is made of iron, an electrode 11 made of a material having a lower standard electrode potential than iron, e.g. magnesium, is placed in the hole h, and a mount 13 connected to one end of the lead wire 12 with the other end connected to the electrode 11 is put in the hole H. The mount 13 is operated from on the ground, fixed and electrically connected to the pipe 10.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for preventing electrolytic corrosion of existing buried pipes, and more specifically, to a method for preventing electrical corrosion of existing buried pipes, and more specifically, for accommodating underground gas pipes, 9 petroleum transport pipes, and 1 water pipes, 1 communication cables. This invention relates to an electrolytic corrosion prevention method for preventing electrolytic corrosion of cable pipes, etc.

[Conventional technology]

Iron pipes buried underground, such as gas pipes, petroleum transport pipes, and cable pipes that house water pipes and communication cables, are in contact with moisture in the soil for many years, and the water, although weak, will weaken. Since it is also an electrolyte, ionization occurs, albeit in a very small amount.

Most buried pipes are made of iron, and iron (Fe) is hydrogen (H
2) Iron ions (pc
++) and elutes in water.

At this time, if oxygen exists in the moisture, iron, so-called red rust (Fe203.H2O), corrodes the buried pipe.

This is called contact corrosion due to metal ionization, but there is also galvanic corrosion that occurs when current flows into the iron pipe from the outside and escapes to the outside in places with low resistance, such as moisture in the soil. This galvanic corrosion, so-called galvanic corrosion, occurs in places where current escapes, and when there are buried pipes installed close to single-track overhead contact lines, the current that should return via the track leaks from the joints of the track. One of the reasons for this could be the passage through iron pipes.

To prevent the former of the two factors that cause underground pipes to corrode,
To prevent the latter, it is known to apply an anticorrosive paint to the buried pipe to break the contact state, and to form an electrical insulating layer on the surface of the buried pipe to block current from the outside.

Recently, it has also been proposed to connect the buried pipe to an electrode that has a greater ionization tendency than the current flowing through the buried pipe, and to utilize the anodic current to prevent electrolytic corrosion.

For example, as shown in FIGS. 6 and 7, a magnesium electrode 2 is electrically connected to a pipe 1 to be anti-corrosioned by a lead wire 3, and the road surface Rd is at least 1 m long x 1 m wide. As described above, after excavating to a depth of 1 m or more to form a working hole H and housing the electrode 2 and lead wire 3 in the underground space, the end of the lead wire 3 is thermite welded to the target pipe 1.

A concrete precedent example of this type of anti-corrosion method is JP-A No. 6
0-36680 can be mentioned.

[Problem to be solved by the invention]

In the above-mentioned anti-corrosion method, it is necessary to excavate the road surface prior to the anti-corrosion work, and if the road on which the work is being performed is a main road, if the excavated area is large, vehicle traffic will have to be restricted, and vehicles will be forced to sit for a long time. This poses problems such as not only hindering the smooth passage of traffic, but also exposing workers to danger.

Therefore, the present invention aims to provide a method for preventing electrolytic corrosion that requires extremely short working time and does not require extensive excavation work on roads.

[Means to solve the problem]

In order to achieve the above-mentioned objects, the present invention provides a method for preventing electrolytic corrosion of existing underground pipes, in which an existing underground pipe made of iron and a metal electrode having a lower standard electrode potential are connected to each other. A working hole is drilled in the road surface toward the target pipe for corrosion prevention, an electrode housing hole is continuously drilled in this working hole, and an electrode having a lower standard electrode voltage than the target pipe made of iron is inserted through the working hole, The device is characterized in that the attachment device connected to the end of the lead wire connected to the electrode is configured to attach the tool to the pipe to be prevented from electrolytic corrosion for electrical connection.

[For production]

A work hole with a small diameter that does not require full-scale restoration of road surface pavement is formed on the road, and a fixing device for the end of the lead wire is inserted along with the anode electrode toward the target pipe through this work hole, and the fixing device for the lead wire end is inserted into the road surface. It can be installed without welding by using a fixing tool from the opening of the working hole.

〔Example〕

Hereinafter, Figure 1 of the drawings accompanying the embodiments of this invention will be described.
′! This will be explained along the diagram J5. First, in these figures, the symbol IO indicates an existing pipe buried underground that is to be subjected to cathodic protection.
A working hole H having a diameter of approximately 11 cIn is excavated on the road surface Rd directly above the existing pipe 10 in a state perpendicular to the existing pipe 10. The interval between these working holes H is approximately 20 m,
Excavate to a deeper position than the existing pipe IO.

The excavation work for this work hole H is shown in Figures 3 (A) and (B).
compressor or water pump 2 as shown in
From zero, high-pressure fluid is injected from the tip of the thin tube 21 to improve the road surface R.
d, and then use a suction device 30 such as a vacuum pump to suction and discharge the earth and sand in the working hole H through the discharge pipe 3I, and continue to the working hole H as shown in FIG. In this way, slightly oblique electrode housing holes are excavated and formed.

If the existing pipe 10 in this electrode housing hole is made of iron, a material 1 having a lower standard electrode potential than iron, such as magnesium (Mg)
A mounting tool 13 is housed in the working hole H, and the other end of the lead wire 12 connected to the electrode 11 in advance is connected.

The mounting tool 13 is made of an elastic conductive material and is formed into an Ω shape, and the opening width of the opening L3A is set to be smaller than the diameter of the existing pipe 10. A shaped sponge ring 14 is applied and contains butyl rubber therein so that the attachment tool 13 can come into contact with the existing pipe 10.

For installation, use a screw receiver 15 with a female screw hole on the outside of the top of the tool 13.
is fixed, and a bolt 15A is screwed into this screw receiver 15, and its lower end is placed in a relationship such that it can penetrate the sponge ring 14 and come into contact with the existing pipe 10 (the fourth
Figure 5).

To attach the tool 13 to the existing pipe 10, insert the box wrench R from the upper opening of the work hole H, open the opening 13A of the tool 13, and use elastic force to wrap around the existing pipe IO. Then, the bolt 15A is turned to feed the screw, and the tip of the bolt 15A bites into the surface of the existing pipe 10 due to the elastic force of the tool 13.
are integrated. The butyl rubber in the sponge ring 14 prevents corrosion of the damage caused by the tip of the bolt 15A into the existing pipe 10.

By removing the box wrench R from the bolt 15A, the electrolytic corrosion countermeasure for the existing pipe 10 is completed, and the mounting tool 13 is left in the working hole H.

In addition, in the above embodiment, the mounting tool 13 has a different shape 9.
It may be made functional; in short, it is sufficient to enclose the existing pipe and feed the bolt to provide electrical continuity to the existing pipe.

〔Effect of the invention〕

As is clear from the above explanation, according to the method for preventing electrolytic corrosion of existing buried pipes of the present invention, a work hole with a small diameter that does not require full-scale restoration of road surface pavement is formed on the road surface. The positive electrode can be attached to the existing pipe from above the road surface by simply forming a hole large enough to accommodate the electrode, so the excavation work before and after construction is extremely small, and the area is small. Backfilling can be done easily in a small area, and traffic regulations are small-scale, and even if regulations are implemented, they only take a very short time.

[Brief explanation of drawings]

Figure 1 is a sectional view of a road to which this invention is applied, Figure 2 is a sectional view taken along the line Figure 5 is a front view, Figure 5 is a slope view of the same, Figure 6 is a plan view of the road surface explaining the conventional construction method, Figure 7 is a plan view of the road surface explaining the conventional construction method.
The figure is a sectional view taken along the line ■-■ in FIG. 6. lO... Existing pipe, 11... Electrode, 12... Lead wire, 13... Installation tool, 13A... Opening, 14...
...Sponge ring, 15...Screw holder, 15A...
bolt. Figure 1: ■ Figure 2: Figure 2

Claims (1)

[Claims] (1) In a construction method for preventing electrolytic corrosion of existing underground pipes, in which an existing buried steel pipe is connected to a metal electrode with a standard electrode potential lower than that of the existing underground pipe, a work hole is placed on the road surface toward the pipe to be prevented from electrolytic corrosion. An electrode receiving hole is continuously drilled in this working hole, and an electrode with a standard electrode voltage lower than that of the iron target tube is inserted through the working hole, and the end of the lead wire connected to the electrode is inserted into the working hole. 1. A method for preventing electrolytic corrosion of existing buried pipes, characterized in that a fixture connected to a pipe is attached to a pipe to be prevented from electrolytic corrosion for electrical connection.