JPH0813174A - Corrosion preventive method for rear of bottom plate of tank - Google Patents

Abstract

PURPOSE:To provide a method for preventing the rear of the bottom plate of a tank for storing crude oil, petroleum, or the like from being corroded. CONSTITUTION:A nonelectrolyte water absorbing material such as silica gel is mixed with tank foundation earth 5 by 10-30%. In this way, since the entering water is absorbed by the water absorbing material, the water content ratio of the foundation earth is controlled low to prevent the corrosion of the rear of the bottom surface of a tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion method for preventing corrosion of the bottom surface of a bottom plate of an oil storage tank for crude oil, petroleum, etc.

[0002]

2. Description of the Related Art Oil storage tanks such as crude oil and oil tanks are
Generally, it is installed directly on a foundation soil such as mountain sand and used for a long period of time, but the back surface (steel plate) of the tank bottom plate may undergo severe corrosion. In extreme cases, it is very important to prevent this corrosion, as corrosion holes can lead to the destruction of the tank. It is considered that the reason why the bottom surface of the tank bottom plate is corroded is that the bottom plate directly contacts with the wet foundation soil to cause the air flow difference corrosion like general soil corrosion. Soil corrosion is greater in moist soil and less in dry soil. Therefore, in a conventional tank installed directly on the foundation soil, for example, as shown in FIG. 1, construction for preventing intrusion of water from the outside, for example, a gap between the tank bottom plate and the foundation is sealed with a sealing material 4 such as resin. The water content ratio was prevented from rising by creating a closed structure, such as covering and preventing water from entering, and preventing the water from entering due to rising groundwater by making the basic structure 3 a structure with a concrete bottom. However, there is a possibility that water may enter through the gap between the foundation and the tank or through the concrete bottom due to poor construction or deterioration of the material after a long time, and the water content ratio of the foundation soil may increase. In that case, there is a drawback that this cannot be detected easily, and the repair requires a large amount of work and is very expensive.

[0003]

No reliable, practical, and relatively low-cost method for controlling the water content of the foundation soil at the bottom of the tank to be low for a long time has been developed. From this point of view, the present invention provides a method for controlling the water content of the tank foundation soil to be low for a long period of time to prevent corrosion of the back surface of the tank bottom plate.

[0004]

Means for Solving the Problems The gist of the present invention for solving the above problems is to add a non-electrolyte water-absorbing material to the foundation soil embanked on the tank foundation to control the water content of the tank foundation soil to a low level. This is a method of preventing corrosion on the back surface of the tank bottom plate, which is characterized by mixing. Silica gel is suitable as the non-electrolyte water-absorbing material. In FIG. 1, 3 is a tank base concrete, 2 is a steel tank side plate, 1 is a tank bottom plate, and 4 is a sealing material provided over the inner and outer circumferences of the tank bottom plate 1 and the tank base concrete 3.
In the present invention, the non-electrolyte water absorbing material is mixed in the tank foundation soil 5. Examples of the non-electrolyte water-absorbing material include silica gel. By mixing the non-electrolyte water-absorbing material into the tank foundation soil 5, the invading water is absorbed by the water-absorbing material, so that the water content ratio of the foundation soil 5 is controlled to be low and corrosion of the tank bottom can be suppressed. it can. The higher the mixing ratio of the water-absorbent material is, the larger the water absorption capacity is, which is preferable. This water-absorbing material has 1
It may be mixed in the range of 0 to 30% by weight. If the mixing ratio is too low, the water absorption effect cannot be obtained, so 10% by weight or more is necessary. However, even if it is mixed in too much, the function as the basic soil cannot be obtained, so it is preferable to set the upper limit to 30%.

[0005]

The present invention will be described with reference to the following examples. (Example 1) 30% by weight of silica gel was added to sand having a water content adjusted to 10%. 20 × 50 in this mountain sand
× 3tmm ordinary steel was embedded, left at room temperature, and the water content of the sand after 2 months was measured. The water content was 5%.
Met. No corrosion was found in the embedded ordinary steel. As a comparison, when the same test was performed on the sand without adding silica gel, severe corrosion was observed.

(Example 2) A concrete foundation with a bottom having a diameter of 1000 mm (concrete thickness 50 m
m) was made, and sand with a water content of 6% mixed with 10% by weight of silica gel was placed as a foundation soil. On top of this, ordinary steel with a diameter of 900 mm x 6 tmm was installed. The gap was covered with a silicon-based sealing material having a thickness of 3 mm. In order to reproduce defective construction and deterioration of the sealing material, the sealing material was provided with 4 flaws, and the concrete foundation was also provided with 1 mm thick crack at the center of the bottom. Also, to reproduce the effect of water intrusion from the outside, 1
Watered twice a day. One year later, the water content of the sand was measured and found to be 5%. No corrosion was found on ordinary steel. As a comparison, the same test was carried out on sand sand to which silica gel was not added. As a result, the water content of sand sand increased to 7%, and ordinary steel was corroded at several places.

[0007]

As described above, in the present invention,
By mixing the non-electrolyte water-absorbing material in the tank foundation soil 5, the invading water is absorbed by the water-absorbing material,
The water content of the foundation soil is controlled to be low, and the backside of the tank bottom plate can be accurately protected for a long period of time.

[Brief description of drawings]

1 is a schematic cross-sectional view of the foundation of the tank of the present invention.

[Explanation of symbols]

 1 Tank bottom plate 2 Tank side plate 3 Tank foundation 4 Sealing material 5 Tank foundation soil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Nishida 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.Technical Development Division (72) Inventor Kenmasa Yuasa 20-1 Shintomi, Futtsu City, Chiba Prefecture Iron & Steel Co., Ltd.

Claims (3)

[Claims] 1. An anticorrosion method for the back surface of a tank bottom plate, characterized in that, in an oil storage tank installed on a foundation soil 5 such as sand and sand, a non-electrolyte water-absorbing material is mixed into the foundation soil 5 at the tank bottom. 2. A non-electrolyte water-absorbing material is added to the basic soil 5 in an amount of 10
The anticorrosion method for the bottom surface of the tank bottom plate, characterized in that the content is -30% by weight. 3. The method for preventing corrosion of the back surface of the tank bottom plate according to claim 1, wherein the non-electrolytic water-absorbing material is silica gel.