JP2813833B2 - Corrosion prevention structure of storage tank bottom plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an anticorrosion technology for various storage tanks such as petroleum, LNG, and LPG, and more particularly to an anticorrosion structure for a storage tank bottom plate.

<Prior Art> As a method of preventing corrosion of an oil tank bottom plate, it is known to form an anticorrosion layer such as asphalt sand on a tank installation surface.

In addition, the Fire and Disaster Management Agency has instructed the tank bottom plate to be separated from the groundwater surface by at least 2 m to avoid soil corrosion of the tank bottom plate due to capillary action.

For this reason, in order to eliminate the capillary phenomenon in asphalt, conventionally, asphalt sand containing asphalt with a construction limit of 9% was used, and the entire area of the tank installation surface was thickened.
The anticorrosion layer is constructed by rolling to about 10cm.

As a countermeasure against rainwater, an expensive sealing material is linearly installed between the annular and the anticorrosion layer to prevent rainwater from entering.

<Problems to be Solved by the Present Invention> The conventional anti-corrosion technology for the storage tank bottom plate described above has the following problems.

<A> The piping of the tank and the scaffold that lifts the heating coil obstruct the work conditions.

For this reason, a machine having a large rolling capacity cannot be carried in, and the asphalt mortar cannot be sufficiently compacted.

Therefore, it is impossible to produce asphalt mortar having a porosity of 0%.

<B> It has been found that the corrosion of the tank bottom plate is not the so-called soil corrosion due to capillary water but the condensation corrosion.

However, since dew condensation countermeasures have not been appropriately performed, dew condensation corrosion cannot be effectively prevented.

<C> Even if an expensive sealing material is used, the corrosion of oxygen and water vapor diffuses through asphalt below the sealing material, so that macrocell corrosion by the oxygen concentration battery cannot be prevented.

<Object of the present invention> The present invention has been made in order to solve the above problems, and its purpose is to reliably prevent the intrusion of air and water vapor, and to achieve economical and effective corrosion protection. I can plan,
An object of the present invention is to provide an anticorrosion structure for a storage tank bottom plate.

<Means for Solving the Problems> That is, the present invention relates to a corrosion protection structure of a storage bottom plate in which an anticorrosion layer composed of an asphalt mortar layer is provided on the lower surface of a storage tank bottom plate. The anti-corrosion structure of the storage tank bottom plate is characterized by having been formed.

Furthermore, the present invention provides that the seal coat has an outer wall of the storage tank of 5 m to 10 m.
And a corrosion prevention structure of the storage tank bottom plate characterized by being continuous along the outer wall in a donut shape in the range of (1).

<Example> Hereinafter, an example will be described with reference to the drawings.

<A> Overall Structure of Tank FIG. 1 is a cross-sectional view of an installation portion of the tank 1.

2 is a rubble, 3 is an asphalt mortar layer rolled over the rubble 2 in the installation area of the tank 1, and 4 is a seal coat interposed between the asphalt mortar 3 and the bottom plate of the tank 1 in a certain area. .

<B> Asphalt mortar layer In the present invention, the anticorrosion layer is constituted by a laminate of the asphalt mortar layer 3 and the seal coat 4.

Therefore, in the present invention, the asphalt mortar layer 3 in which the asphalt content is about 5%, which is 9% or more, can be used.

The thickness of the asphalt mortar layer 3 is 10 cm as before.
It is about.

<C> Seal coat FIG. 2 is a plan view of the seal coat 4, and FIG.

The seal coat 4 may be made of, for example, rubber asphalt having excellent water blocking and heat resistance and an additive added to blown asphalt.

The seal coat 4 is applied in the form of a thin film (for example, 6 mm thick) so as not to form a gap between the asphalt mortar layer 3 and the bottom plate 5 of the tank 1.

Although the seal coat 4 may be applied to the entire surface of the bottom plate 5,
It is constructed in a donut shape over a range of a distance L from the outer wall 6 of the sunk 1.

The distance L is preferably in the range of 5 m to 10 m regardless of the diameter D of the tank 1.

Also, as shown in FIG. 3, the peripheral portion of the bottom plate 5 and the joint portion of the dog running 7 are continuously sealed with a sealing material 8 such as a compound.
Cover with.

<D> Reason for limiting the application range of seal coat Various corrosion tests and investigations of the actual corroded tank revealed that the range of corrosion was 5m to 10m from the outer wall of the tank, regardless of the size of tank 1. Turned out to be.

This is presumably because the diffusion range of the amount of oxygen that causes corrosion is in the range of 5 m to 10 m from the outer periphery of the tank 1.

The present invention pays attention to this point, and provides the seal coat 4 limited to the range of occurrence of corrosion.

By setting the range of application of the seal coat 4 to the minimum necessary in this way, it is more economical than the case where the seal coat 4 is applied to the entire bottom surface of the tank 1.

<Action><A> Water Vapor The seal coat 4 is applied over the expected corrosion range.

Therefore, as shown by the broken line in FIG. 3, the water vapor that passes through the asphalt mortar layer 3 and rises is reliably blocked by the seal coat 4.

 Therefore, corrosion due to water vapor does not occur.

<B> Condensation Since the seal coat 4 is in close contact with the bottom plate 5 of the tank 1, no gap is formed between the bottom plate 5 and the seal coat 4 even if the bottom plate undulates vertically due to the change in the amount of oil.

Therefore, the surrounding warm air does not enter between the bottom plate 5 and the seal coat 4, and no dew condensation occurs on the entire back surface of the bottom plate 5.

 As a result, corrosion caused by condensation can be effectively prevented.

<C> About the bottom plate in the non-coated range The back surface of the bottom plate 5 where the seal coat 4 is not applied is
It comes into contact with the water vapor that has passed through the asphalt mortar layer 3.

However, the area where seal coat 4 is not applied
Corrosion does not occur because it is outside the range of diffusion of the amount of oxygen that originally causes corrosion.

<Other Examples> A lateral tensile force may act on the bottom plate 5 of the repaired tank 1 in some cases.

In order to cope with such a case, the seal coat 4 may be provided in the middle of the asphalt mortar 3 as shown in FIG.

That is, the first asphalt mortar
3a, the second asphalt mortar 3b is laminated, and the second
The seal coat 4 is laminated on the upper surface of the asphalt mortar 3b.

Finally, the third asphalt mortar 3c is laminated on the upper surface of the seal coat 4 to form an anticorrosion layer.

Alternatively, as shown in FIG. 5, a waterproofing layer 3d may be formed by applying an emulsion-type waterproofing agent to the upper surface of the third asphalt mortar 3c and then spraying an organic polyamine powder or the like.

Thereby, these comprehensive anticorrosion effects can be expected.

In FIG. 4, a seal coat 4 may be added between the first and second asphalt mortars 3a and 3b, and a plurality of seal coats 4 may be interposed.

In this embodiment, the conditions for the application range of the seal coat 4 are the same as those in the above embodiment.

<Effects of the Present Invention> The present invention is as described above, and the following effects can be obtained.

<B> The gap was eliminated by interposing a seal coat between the tank bottom plate and the asphalt mortar.

Therefore, invasion of air or water vapor can be prevented, and corrosion of the tank bottom plate can be prevented.

<B> The construction range of the seal coat was limited to a range of 5m to 10m from the outer wall regardless of the diameter of the tank 1.

Compared with the case where the construction is performed on the entire bottom plate, not only the material cost can be reduced, but also the construction becomes easier.

<C> Asphalt mortar with a lower blending ratio than before can be used.

Moreover, since the seal coat is an inexpensive material, the construction cost of the anticorrosion layer is reduced.

<D> Since the seal coat has excellent heat resistance, there is no problem even when the bottom plate surface is welded.

[Brief description of the drawings]

 Fig. 1: Overall view of tank Fig. 2: Plan view of seal coat Fig. 3: Enlarged sectional view of peripheral portion of tank Fig. 4 and 5: Explanatory diagram of other embodiments

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuru Shiozuki 1000 Hamashima-cho, Hatsushima-cho, Arita-shi, Wakayama Tonen Wakayama Plant (72) Inventor Isamu Yano 1-25-1 Nishishinjuku, Shinjuku-ku, Tokyo Large (72) Inventor Yoshito Uekihara 1-25-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo Daisei Construction Co., Ltd. (72) Shinichi Katsumura 1-1-25-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Large (56) References JP-B-61-52075 (JP, B2) JP-B-57-60237 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02D 27 / 38

Claims (2)

(57) [Claims] An anticorrosion structure for a storage tank bottom plate provided with an anticorrosion layer made of an asphalt mortar layer on a lower surface of the storage tank bottom plate, wherein a seal coat made of asphalt or hard asphalt is formed on the surface or in the middle of the asphalt mortar. Anti-corrosion structure on the bottom plate. 2. The anti-corrosion structure for a storage tank bottom plate according to claim 1, wherein the seal coat is continuous along the outer wall in a donut shape in a range of 5 m to 10 m of the outer wall of the storage tank.