JPS6315334Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piping structure, and an object of the present invention is to prevent corrosion of the underground piping due to macro cells formed between the underground piping and building reinforcing bars.

Pipes such as water pipes in buildings are usually made of steel, and corrosion and leakage accidents frequently occur in the parts buried in the soil. The main cause of this is macrocell corrosion between building reinforcing bars and underground piping, and although insulation coatings are applied to the outer surfaces of steel piping, this is not sufficient to prevent corrosion.

In Figure 1, 1 is a pipe, 2 is a building wall, 3 is a reinforcing bar, 4 is a foundation concrete, and 3' is a reinforcing bar in the concrete 4, and the reinforcing bars 3 and 3' are electrically connected. do. Further, the pipe 1 is made of steel and has an insulating coating applied to its surface. Since the PH value of concrete is about 12, this reinforcing bar 3' has an open circuit potential of about 0 to 200 mV (SEC). On the other hand, since the underground pipe 1' buried in the soil has an open circuit potential of about -500 to -700 mV (SEC), there is
This results in a potential difference of as much as 500mV. In such a state, in the case of a structure in which the pipe 1 comes into contact with the reinforcing bars 3 by penetrating the wall 2, etc., a battery is formed due to this potential difference, and if there is a coating defect 6 in the coating of the pipe 1', the reinforcing bars 3' → Rebar 3 → Contact point 5
The current flows through the following path: → above-ground pipe 1 → buried pipe 1' → soil → reinforcing steel 3'. This current flows into the soil from the paint film defects etc. 6 of the buried pipe 1' toward the reinforcing bars 3', and at this time, the pipe body in the paint film defects etc. 6 is severely corroded by this current.

This corrosion rate is only 1 to 2% for a 3.5mm thick pipe.
It is so large that it can penetrate through the pipes in a year, and it is believed that many of the corrosion leakage accidents in small diameter buried pipes around buildings are due to this cause.

As a means of preventing such macrocell corrosion, a method has been adopted in which an insulating joint 7 is interposed in the above-ground piping 1 between the contact point 5 and the buried piping 1', and the current is interrupted here, as shown in FIG. It is being

Most commonly, this insulating joint 7 has an insulating packing 71 made of synthetic resin or the like interposed between the flanges 70, 70, as shown in FIG.
70 is fastened with a bolt/nut 74, an insulating sleeve 72, and an insulating washer 73. The thickness of the insulation packing 71 is usually 1~
It is about 5mm.

However, even if such an insulating joint 7 is used, if the fluid flowing in the pipe is tap water or other conductive fluid, the insulating packing 71 is thin, so the current generated by the macro cell is not completely blocked. Some of the current flows out to the liquid side before the flange insulation and flows beyond the insulation into the tube body. Now, assuming that the inside of the pipe is filled with tap water and the diameter of the pipe is 50mmφ, this insulation joint 7
The resistance is only about 500Ω, and although this level of resistance reduces the magnitude of the current flowing through the pipe to some extent, a considerable amount of current still flows out from defective parts of the coating 6, so corrosion is not sufficiently prevented. .
Therefore, depending on the type of fluid inside, the insulating joint 7 having the above structure alone may not provide a fundamental solution.

Therefore, in order to further improve the insulation, an elongated insulating joint 9 shown in FIG. 4 is used. As shown in FIG. 5, this long type insulating joint 9 is made of a steel pipe having an appropriate length of about 10 times the inner diameter of the pipe 1.
Its inner surface is insulated and lined with synthetic resin 10, and a screw socket 12' is attached to one end of the tube through an insulating bush 11, and a screw socket 12 is attached to the other end. ′ to connect. In the elongated insulating joint 9 having such a configuration, the resistance of water corresponding to the length of the inner lining becomes the electrical resistance between the pipes 1 and 1', and for example, when tap water flows through a joint with a diameter of 50 mmφ, it is approximately 50,000Ω. The second
This is considerably more effective than the insulating joint 7 shown in FIGS.

However, the long insulating joint 9 needs to be approximately 10 times the pipe diameter even when the fluid inside the pipe is tap water.
Piping with a diameter of 50 mmφ is 50 cm long, and piping with a diameter of 150 mmφ is as long as 150 cm, which limits the installation location, makes installation work more difficult than conventional fittings, and makes the fittings themselves more expensive. There are many problems.

Furthermore, in the case of cooling water or the like where the fluid in the pipe is circulated, the electrical conductivity is higher than that of tap water, so a longer joint is required, and in such a case, it is virtually impossible to prevent corrosion only with insulating joints.

The present invention has been made to improve the drawbacks of the prior art, and is intended to provide a piping structure that can effectively prevent macrocell corrosion.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 6, the pipe 20 penetrates the wall 2 of the building, contacts the reinforcing bars 3 at a contact portion 21, and is buried in the soil around the building. Above ground piping 20 between contact portion 21 and buried piping 20' buried in soil
An insulating joint 22 is interposed at a. Details of this insulating joint 22 will be described later. A conductor 23 is buried in the soil, and this conductor 23 is connected to a lead wire 24.
It is electrically connected to above-ground piping 20b between insulating joint 22 and buried piping 20' via.

The conductor 23 is preferably made of steel, preferably carbon steel, so as not to create a potential difference between it and the pipe 20'. In addition, a steel pipe is particularly suitable from the viewpoint of handling or ease of acquisition, but any material such as a plate material, a prismatic material, a round bar, etc. may be used as long as it has a sufficient area and volume. It is desirable that the conductor 23 be buried as close to the reinforcing bars 3' as possible.

The conductor 23 and the lead wire 24 are joined by thermite welding, and the joint 240 is covered with a corrosion-proofing material 241 to prevent corrosion and falling off. Further, the outer surface of the lead wire 24 is coated with a coating material so as to have an effective anti-corrosion effect. The above-ground pipe 20 and the lead wire 24 may be connected at any position between the insulating part of the above-ground pipe 20 and the soil, but in this embodiment, they are connected to a flange 30' of the soil.

In addition, in consideration of workability on site, insulated joint 2
2, the conductor 23, and the lead wire 24 may be made in advance and installed on site, and the conductor 23 may be buried.

It is also possible to use a backfill material to facilitate current flow from the conductor 23.

In the above configuration, the current flowing through the pipe 20 from the reinforcing bar 3' passes through the fluid inside the pipe at the insulating joint 22, and then flows out from the defective coating film 25 of the soil pipe 20' and the conductor 23 with low ground resistance.
At this time, the current passing through the joint 22 increases, but
Since the surface area of the conductor 23 is much larger than the area of the defective portion 25, the current density of the current flowing out from the defective portion 25 is much smaller than in the case where the conductor 23 is not present. As a result, the corrosion rate is reduced and a corrosion prevention effect can be obtained.

At this time, the inner surface of the pipe 20a on the contact portion 21 side of the insulating joint 22 corrodes due to the current jump in the insulating joint 22. Therefore, it is desirable to take measures to prevent the formation of through holes due to corrosion, such as increasing the thickness of the pipe, but in the present invention, in order to reduce corrosion of the pipe due to this current jump, the insulating joint 22 is constructed with a special structure. It is said that FIG. 7 is a front view thereof. 20a and 20b are pipes, and arrows indicate the direction of flow of corrosion current.

The piping 20a, 20b has flanges 30, 3, respectively.
0' are integrally formed, and this flange 30,
A conductor 31 and an insulating material 32 are interposed between 30'. The conductor 31 is connected to the flange 3 on the upstream side of the corrosion current.
It is in contact with this via the 0 side. An insulating material 32 is interposed between the conductor 31 and the flange 30' on the downstream side of the corrosion current.

The conductor 31 is made of steel or a metal whose natural potential is less noble than steel, and has an annular shape that matches the shape of the flanges 30, 30'. Since the contact between the conductor 31 and the flange 30 is between metal bodies, the sealing performance is poor and leakage is likely to occur. Therefore, in this embodiment, the flange 30 of the conductor 31 is
A large number of protrusions 310 are formed on the side, and a viscoelastic body 311 for sealing is provided between the conductor 31 and the flange 30.
It's through. According to such a configuration, when the flanges 30, 30' are fastened with bolts and nuts, which will be described later, the viscoelastic body 31 as shown in FIG. 8b.
The protrusion 310 in which 1 is crushed comes into contact with the flange 30, and electrical continuity is achieved. At the same time, the viscoelastic body 31
1 seals the internal fluid.

The insulating material 32 interposed between the conductor 31 and the flange 30' is insulating packing made of synthetic resin or the like in this embodiment.
It has an annular shape that matches the shape of 0'.

After interposing the conductor 31 and the insulating material 32 as described above, bolt holes are formed in the flanges 30 and 30',
Here, both flanges are fastened together with bolts and nuts 33 via an insulating sleeve 330 and an insulating washer 331.

According to the above configuration, the corrosion current flows through the pipe 2.
0a→flange 30→protrusion 310→conductor 31, and from there, the fluid in the pipe jumps to pipe 20b. Therefore, the conductor 31 is the pipe 20
Corrosion occurs instead of a, and corrosion of the pipe 20a can be prevented. The corroded conductor 31 may be replaced as appropriate.

It should be noted that the shape of the conductor can be in various forms.
In the embodiment shown, flanges 340, 3 are provided at both ends.
A short tube-shaped conductor 34 having a diameter of 40' is employed. In this embodiment, a protrusion 310 is provided on the flange 340.
A viscoelastic body 311 is interposed therebetween and brought into contact with the flange 30, while an insulating material 32 is interposed between the flanges 340' and 30'. Then, the flanges 340 and 30 are directly fastened with bolts and nuts 33', and the flanges 340' and 30' are respectively connected to the insulating sleeve 33'.
30 and an insulating washer 331, and are fastened with bolts and nuts 33.

According to this configuration, since the conductor 34 is similarly corroded, corrosion of the pipe 20a itself is prevented.

As explained above, the piping structure according to the present invention can effectively prevent macrocell corrosion, and has advantages such as no restrictions on installation locations and low cost.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of a conventional piping structure, Figure 3 is a cross-sectional view of an insulated joint, Figure 4 is an explanatory diagram of a conventional piping structure using a long type insulated joint, and Figure 5
The figure is a sectional view of a long type insulated joint, Figure 6 is an explanatory diagram showing an example of the piping structure according to the present invention, and Figure 7 is an insulated joint for preventing corrosion of the piping in front of the insulated joint due to current jump. A front sectional view of an embodiment of
FIG. 8 is a partially enlarged view thereof, and FIG. 9 is a front sectional view of another embodiment of the insulating joint. In the figure, 20 is a pipe, 21 is a contact part, 22 is an insulated joint, 23 is a conductor, 24 is a lead wire, 30 is a flange, 31 is a conductor, 32 is an insulating material, 33 is a bolt/nut, and 34 is a conductor. show.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a piping structure having a steel insulation-coated buried pipe that electrically contacts reinforcing bars etc. that contact the concrete foundation of a building and is buried in the soil around the building, An electrically insulating part is formed in the above-ground piping between the contact part with the underground pipe and the buried pipe, and a steel conductor is buried in the soil, and the conductor is connected to the above-ground pipe between the insulating part and the buried pipe. A piping structure comprising: a conductor that is electrically connected and the insulating portion contacts the piping on the contact portion side; and an insulating material interposed between the conductor and the buried portion side. 2. The piping structure according to claim 1 of the utility model registration claim, in which the conductor and above-ground piping are electrically connected by a lead wire, and the lead wire and the joint between the conductor and the lead wire are covered with a corrosion-preventing coating material. .