JP3061793B1 - Electric corrosion prevention structure for underground tank - Google Patents

Abstract

To provide an underground tank anti-corrosion structure capable of preventing stray current leaking into the basement to prevent electric corrosion of the underground tank and facilitating manufacturing and construction work. . SOLUTION: An insulating support layer 12 made of asphalt is provided on an upper surface of a support plate 11 made of concrete. An underground tank 13 is provided on the upper surface of the insulating support layer 12. The tank body 14 constituting the underground tank 13 is made of an iron bottom plate 15.
And a cylindrical tube 16, and a corrosion-resistant layer 20 is formed on the outer peripheral surface of the tube 17. Also, the tank body 14
A wire net 25 as a shield member is concentrically disposed at a position separated from the outer peripheral surface by a predetermined distance. The stray current flowing underground is captured by the wire mesh 25, and electric corrosion due to the stray current of the tank body 14 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for preventing electric corrosion of an underground tank.

[0002]

2. Description of the Related Art Generally, an underground tank is used to store drinking water or water for fire extinguishing. This underground tank is composed of a tank main body formed in a cylindrical shape with a bottom, and a lid plate closing an upper end opening of the main body. or,
The tank body has a mechanical strength of, for example, SS400.
And an insulating layer made of an insulating resin or tar applied to the outer peripheral surface of the main body, and a stainless steel (SUS304) or the like joined to the inner peripheral surface of the tank main body. And a lining layer made of a corrosion-resistant metal material.

The insulating layer prevents underground stray current from entering a tank body buried underground, thereby preventing corrosion of the tank body.

[0004]

However, in the above-mentioned conventional structure for preventing corrosion by stray current of an underground tank, an insulating layer is formed on the outer peripheral surface of the tank body, and the insulating layer is formed by various components contained in the ground. If the insulating layer is deteriorated and cracks occur in the insulating layer, stray currents enter the tank body from the cracks, so that it is difficult to prevent electrolytic corrosion of the tank body.

In addition, the operation of applying the insulating layer to the entire outer periphery of the tank body is not completed in one application operation but is repeated several times, so that the operation is very troublesome and causes an increase in cost. was there. For example, the cost of painting tar and epoxy resin is about 10,000 yen per square meter, so if you try to prevent electrical corrosion by painting the entire surface with an insulating layer, several hundred thousand ~
It is expensive, over a million.

The soil in the soil in which the underground tank is buried corrodes due to soil quality, chlorine in the soil, leakage current near the substation along the railway, groundwater, and concrete from the built concrete. Electric current, oxygen in the soil, etc. can be considered. The degree of corrosion of the soil varies depending on the soil quality, the concentration of chlorine and oxygen, the leakage current value, and the like. In any case, in an underground tank buried in unstable soil, there is a problem that it is very difficult to prevent the electrolytic corrosion of the tank due to the stray current at a low cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to prevent a stray current from entering the outer peripheral surface of an underground tank, thereby preventing electrolytic corrosion due to the stray current of the underground tank. It is an object of the present invention to provide an anti-corrosion structure for an underground tank.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a tank buried underground is coated with an insulating agent on its outer peripheral surface.
Form a corrosion-resistant layer and penetrate the tank through the corrosion-resistant layer
In order to cut off stray currents to be, the shield member is disposed so that the outer peripheral surface of the tank cover at a predetermined interval.

[0009]

[0010] In the invention according to claim 2, in claim 1, wherein the shield member is made of metal mesh by the vertical wires and horizontal wires Ru is formed in a grid pattern, the size of one mass of the metal mesh is vertically and It is formed to be 120 mm × 120 mm or less, and the distance between the wire mesh and the outer peripheral surface of the underground tank is set to be much larger than the size of one square of the wire mesh.

According to the third aspect of the present invention, the first aspect or the
In 2 , the porous shield member is disposed at substantially the same distance from the outer peripheral surface of the tank body. According to a fourth aspect of the present invention, in the first or second aspect , the porous shield member is formed so as to be bent so that the periphery of the lower end thereof is deflected to the underground tank side.

[0012]

According to the fifth aspect of the present invention, the first or the second aspect is provided.
In 2 , the properties of the soil filled between the shield member and the outer peripheral surface of the tank body are substantially uniform. In the invention according to claim 6 , in claim 1, the shield member is formed of a metal thin film.

[0014] In the invention described in claim 7, claim 1 or
In 2 , the collector electrode is connected to the shield member. In the invention according to claim 8 , according to claim 7 , as a material of the current collecting electrode, a metal or an alloy having a conductivity lower than that of a shield member made of carbon steel having a corrosion potential in soil, magnesium, It is selected from the group consisting of magnesium alloy, zinc, zinc alloy, aluminum and aluminum alloy.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. A bottomed cylindrical hole H for burying a tank formed at a predetermined depth from the ground E
A concrete support plate 11 is provided at the bottom of the substrate, and an asphalt insulating support layer 12 is formed on the upper surface thereof. An underground tank 13 is provided on the upper surface of the insulating support layer 12.
Is placed. The underground tank 13 includes a cylindrical tank body 14 having a bottom and a cover plate 15 that covers an upper end opening of the tank body 14.

The tank body 14 is made of, for example, iron (SS4).
00) horizontal disk-shaped bottom plate 16 made of a high-strength metal material.
And a cylindrical body 17 made of the same high-strength metal material welded to the upper peripheral edge of the bottom plate 16. Lining layers 18 and 19 made of a corrosion-resistant metal material such as stainless steel (SUS304) are fixed to the upper surface of the bottom plate 16 and the inner peripheral surface of the cylindrical body 17. An insulating agent such as resin or tar is applied to the outer peripheral surface of the cylindrical body 17, and a relatively thin corrosion-resistant layer 20 is formed to withstand corrosion other than electric corrosion.

The cover plate 15 has a horizontal disk-shaped main body 21 made of a high-strength metal material, and lining layers 22, 23 made of a corrosion-resistant metal material joined to the upper and lower surfaces of the main body 21.
It is composed of

A wire mesh 25 as a porous shield member is concentrically provided outside the tank body 14 at a predetermined distance from the outer peripheral surface of the tank body 14. The wire mesh 25 is accommodated in contact with the inner peripheral surface of the hole H formed in the ground. Between the outer peripheral surface of the tank body 14 and the wire mesh 25, soil E1 of uniform soil is filled.
As the uniform soil E1, it is desirable to use, for example, sand having low water retention.

The wire mesh 25 is made of a combination of conductive metal wires, such as carbon steel, which are vertically and horizontally welded in a grid pattern, and each of the grids has a square shape. The size of this one cell is 100mm x 1
Although it may be about 00 mm, it is set in the range of 50 mm to 120 mm square. The distance between the wire mesh 25 and the outer peripheral surface of the underground tank 13 is much larger than the size of one square of the wire mesh 25,
For example, it is set to several times to ten and several times.

In the vicinity of the lower side of the wire mesh 25, a current collecting electrode 26 made of a sacrificial and corrosion-resistant material having conductivity, such as zinc or a zinc alloy, is embedded.
Is electrically connected to

Next, the operation of the anti-corrosion structure of the underground tank configured as described above will be described. For example, an underground tank 13 buried near a substation or the like is susceptible to the underground stray current leaking from the substation. Since this stray current flows in the lateral direction from the ground E using soil having a predetermined depth as a medium, the stray current is captured by the wire mesh 25, and the stray current flows from the lead wire 27 to the current collecting electrode 26. For this reason, it does not flow to the tank main body 14 or the lid 15, and corrosion due to stray current of the tank main body 14 can be prevented.

The effects of the anti-corrosion structure of the underground tank of the above embodiment are listed together with the configuration. (1) Since the wire mesh 25 is used as the porous sealing member, the production can be easily performed, and the work of disposing the underground tank 13 at the buried portion can be easily performed.

(2) Since the wire mesh 25 is buried concentrically so as to cover the entire circumference of the underground tank 13, it is possible to reliably capture the stray current that has entered from any direction. (3) Since the wire mesh 25 having a uniform mesh is used, stray current can be stably captured at any part.

(4) Since the wire mesh 25 is provided concentrically at a predetermined distance from the tank body 14, the effect of blocking stray current can be exerted uniformly. (5) An insulating support layer 12 is provided on the upper surface of the support plate 11,
Since the tank main body 14 is supported by the support layer 12, it is possible to cut off a stray current from entering from below.

The above embodiment can be embodied with the following modifications. As shown in FIG. 3, a shield member 30 in the form of a vertical lattice may be used instead of the wire mesh 25. The shield member 30 is formed by connecting a large number of conductive shield wires 33 to 33 at equal pitches between a pair of upper and lower conductive metal rings 31 and 32.

In this alternative example, the shield member 30 can be manufactured more easily than a shield member made of a wire mesh. The shape of the mesh 25a of the wire mesh 25 may be hexagonal as shown in FIG. 4, or may be triangular, pentagonal, or heptagon or more polygonal (not shown).

As shown in FIG. 5, a portion 25b may be provided which bends laterally with respect to the periphery of the lower end of the wire mesh 25. In this alternative example, it is possible to reliably block a stray current that attempts to enter from between the lower ends between the tank body 14 and the wire mesh 25.

As shown in FIG. 6 , in the existing underground buried tank 13 or a newly installed underground buried tank, a shield rod 41 constituting the shield member 40 is inserted into the soil near the tank body 14, and as a whole, A number of shield rods 41 to 41 may be embedded so as to surround the tank body 14, and the upper ends of the rods 41 to 41 may be connected by the lead wires 42.

In this alternative example, the existing underground tank 1
3 can be easily provided with a shield member for preventing electric corrosion. -As a porous shield member, a shield plate formed by press-forming a metal plate having conductivity and punching it out into a wire mesh shape can be used.

In this alternative example, the manufacture of the shield member can be easily performed. -The said shield member may be formed with a metal thin film. This metal is, for example, carbon steel, and its thickness is selected in the range of several μm to several mm.

As the material of the current collecting electrode 26, as a metal or alloy having a conductivity lower than the corrosion potential of the shielding member made of carbon steel in the soil, other than zinc and zinc alloy described above, for example, magnesium, There is a magnesium alloy, aluminum or an aluminum alloy.

[0032]

As described in detail above, the present invention has the following effects. In the first aspect of the present invention, the stray current to be entering the underground tanks to capture the shielding member it is possible to prevent electrolytic corrosion of underground tanks, attempts to prevent the electrolytic corrosion by applying an insulating layer Follow
Compared with the structure of the prior art, manufacturing and construction work can be performed easily and cost can be reduced.

[0033]

According to the second aspect of the present invention, the shield portion
Since wood is formed by a cross-cut wire mesh, weight and manufacturing
Construction and construction work can be facilitated,
The stray current can be captured almost uniformly and stably over the entire circumference. The vertical and horizontal 12 size of one mass of wire mesh
Since it is formed into a square of 0 mm or less, stray current can be reliably captured by setting the distance between the outer peripheral surface of the underground tank main body and the wire net to a predetermined value or more.

According to the third aspect of the present invention, since the shield member is disposed substantially concentrically with respect to the outer peripheral surface of the underground tank, the stray current capturing action can be stabilized.
According to the fourth aspect of the present invention, the shield member is formed on the periphery of the lower end of the shield member so as to face inward in the horizontal direction.
The stray current can be more reliably cut off.

[0036] Claim5In the described invention, the shield member and the
The properties of the soil filled between the outer surface of the
Control the corrosion of the outer surface of the underground tank.
Can be.

According to the sixth aspect of the present invention, since the shield member is formed of a metal thin film, it is possible to more reliably prevent electrolytic corrosion. According to the seventh aspect of the present invention, since the current collecting electrode is connected to the shield member, the potential of the shield member can be lowered so that stray current can be captured smoothly.

[0038] In the invention of claim 8, since the corrosion potential of the soil as the material of the collecting electrode was lower material than the corrosion potential of the shield member, the stray current flowing through the shield member smoothly to the collector electrode It can be guided, and corrosion of the shield member can be suppressed, and durability can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an electric corrosion preventing structure of an underground tank embodying the present invention.

FIG. 2 is a horizontal sectional view of the underground tank of FIG.

FIG. 3 is a perspective view of only a shield member showing another embodiment of the present invention.

FIG. 4 is a front view showing a mesh of a shield member according to another embodiment.

FIG. 5 is a schematic view showing an anti-corrosion structure according to another embodiment.

FIG. 6 is a schematic perspective view showing an anti-corrosion structure according to another embodiment.

[Explanation of symbols]

11 ... support plate, 12 ... insulating support layer, 13 ... underground tank,
14: tank body, 25: wire mesh as shield member,
26 ... current collecting electrode, 30 ... shield member, 31, 32 ... conductive annular ring, 33 ... shield wire, 40 ... shield member, 41 ... shield rod, 42 ... lead wire.

Continuation of the front page (56) References JP-A-8-193282 (JP, A) JP-A-56-106772 (JP, A) Utility model registration 2552002 (JP, Y2) Jiko 59-32593 (JP, Y2) U.S. Pat. No. 5,065,983 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65D 88/76 B65D 90/22-90/46 C23F 13/00-13/22

Claims (8)

(57) [Claims] 1. The outer surface of a tank buried underground
A corrosion-resistant layer is formed by applying an insulating agent to the
Stray currents that attempt to penetrate the tank through the corrosion-resistant layer
In order to shut off the flow, electrolytic corrosion prevention structure of the underground tank, wherein a shielding member to the outer peripheral surface of the tank cover at a predetermined interval are arranged. 2. The shield member according to claim 1 , wherein
Is formed in a grid pattern with vertical and horizontal wires.
Consists that wire mesh, the size of one mass of the metal mesh vertical and horizontal 1
An anti-corrosion structure for an underground tank, which is formed to have a size of 20 mm × 120 mm or less, and a distance between the wire mesh and the outer peripheral surface of the underground tank is set to be much larger than a size of one grid of the wire mesh. 3. The method of claim 1 or 2, the porous shielding member, electrolytic corrosion prevention structure of the underground tank are disposed at a substantially equal distance from the outer peripheral surface of the tank body. 4. The method of claim 1 or 2, the porous shielding member, electrolytic corrosion prevention structure of the underground tank its lower periphery is formed by bending so as to deflection underground tank. 5. A method according to claim 1 or 2, electrolytic corrosion prevention structure of underground tanks properties of the filled soil is substantially uniform between the outer circumferential surface of the shield member and the tank body. 6. The structure according to claim 1, wherein said shield member is formed of a metal thin film. 7. The claim 1 or 2, electrolytic corrosion prevention structure of the underground tank to the shield member being connected to the collector electrode. 8. The method of claim 7, in metal or alloy corrosion potential of the soil has a lower conductivity than the corrosion potential of the shield member made of carbon steel as the material of the collector electrode, magnesium, magnesium alloys, zinc Anti-corrosion structure for underground tanks selected from the group consisting of aluminum, zinc alloys, aluminum and aluminum alloys.