Corrosion prevention measures for underground tanks, including piping, that store fuels such as organic solvents.

Abstract

This invention provides a corrosion-preventive structure for underground fuel storage tanks that store biomass fuels and ethanol-blended gasoline. [Solution] A corrosion prevention structure for the contact portion between an underground fuel storage tank and piping inside the underground tank, characterized in that an underground fuel storage tank 1 for storing fuel such as mixed gasoline or biomass fuel agents, an injection pipe 2 or suction pipe disposed in the underground fuel storage tank and extending from the underground fuel storage tank to the outside, and when welding the injection pipe or suction pipe to the underground fuel storage tank, the injection pipe or suction pipe is fitted into an opening made in the underground fuel storage tank, and the welded portions 13a, 15 of the injection pipe or suction pipe are fitted with fluorine packing to prevent corrosion.

Description

Technical Field

[0001] The present invention relates to a method for preventing corrosion of an underground fuel storage tank including pipes for storing organic solvents such as biomass fuel and ethanol.

Background Art

[0002] Today, underground fuel storage tanks are widely used at gas stations and the like. Conventionally, such underground fuel storage tanks have stored fuels such as gasoline and light oil, but today, various fuels such as blended gasoline and biomass fuel are used, and it has become necessary to store such fuels in underground fuel storage tanks as well.

[0003] Such underground fuel storage tanks have a high corrosion rate during use, resulting in corrosion and pitting, and problems such as soil contamination may occur if there is fuel leakage or the like. Therefore, it is necessary to prevent corrosion of underground fuel storage tanks. Conventionally, it has been necessary to protect the inside of the solvent tank with a solvent-resistant material. For example, Patent Document 1 proposes a method for modifying an existing fuel tank in such a case. In particular, trace amounts of acetic acid are present in the manufacturing process of bioethanol, and the absorption of water and solvent enzymes during storage contribute to increasing its corrosiveness.

[0004] On the other hand, injection pipes for injecting bioethanol and biodiesel fuel into the tank and suction pipes for sucking fuel from the underground tank are provided in the underground fuel storage tank, and these pipes are also corroded by the fuel.

[0005] Furthermore, underground fuel storage tanks are made of iron (steel), while the piping welded to the underground tanks is made of a different metal material such as stainless steel. When the piping is welded to the underground tanks, iron and stainless steel come into contact, and galvanic corrosion occurs, where the iron side corrodes preferentially due to the potential difference. In other words, when metals with a potential difference come into contact, the iron loses electrons as the anode, and corrosion progresses. The rate of this corrosion changes depending on the magnitude of the potential difference, temperature, water quality, and the presence or absence of gaps, and corrosion progresses accordingly. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-211685 [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, as described above, underground tanks storing various fuels such as modern blended gasoline and biomass fuels require different corrosion prevention measures than conventional underground storage tanks. In particular, corrosion progresses at the connection points between the tank body and piping due to the corrosion mechanism caused by contact between dissimilar metals, leading to major problems such as cracks and pipe detachment at the connection points. This invention aims to solve the above problems. [Means for solving the problem]

[0008] The above problem is solved by the present invention, which provides an underground fuel storage tank for storing fuels such as mixed gasoline or biodiesel fuel, an injection pipe (drop pipe) or suction pipe (suction pipe) disposed in the underground fuel storage tank and extending outward from the underground fuel storage tank, with a fluorine packing or the like applied to the contact portion, and when welding the injection pipe or suction pipe to the underground fuel storage tank, the injection pipe or suction pipe is fitted into an opening made in the underground fuel storage tank, and the welded portion of the injection pipe or suction pipe uses piping with the above-mentioned fluorine packing, thereby preventing corrosion of the piping at the contact portion and preventing the occurrence of corrosion at the contact portion.

[0009] Furthermore, when connecting the injection pipe or suction pipe to the flange, the contact portion of the injection pipe or suction pipe is fitted with the fluorine packing, thereby preventing corrosion at the contact portion with the flange. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows the basic configuration of an underground fuel storage tank illustrating this embodiment. [Figure 2] This diagram shows the cross-sectional configuration of an underground fuel storage tank. [Figure 3] This diagram shows the welded joint between the underground tank and the injection pipe (drop pipe). [Figure 4] This is a cross-sectional view illustrating the configuration near the connection point between the underground tank and the injection pipe. [Modes for carrying out the invention]

[0011] The embodiments of this invention will be described below with reference to the drawings. Figure 1 is a diagram illustrating the configuration of the underground fuel storage tank in this embodiment. In the figure, the underground fuel storage tank (hereinafter simply referred to as the underground tank) 1 stores fuel oil such as mixed gasoline or biomass fuel. The underground tank 1 is equipped with, for example, an injection pipe 2 for injecting fuel oil, a suction pipe 3 for drawing fuel oil from the underground tank 1, a vent pipe 4 for ventilating the underground tank 1, and a liquid level gauge 5 for measuring the liquid level of the fuel oil stored in the underground tank 1. The underground tank 1 is buried to a predetermined depth from the ground surface, and concrete (not shown) is installed on top of the underground tank 1.

[0012] An inlet 6 is provided on the surface of the injection pipe 2, and fuel oil is injected from the inlet 6 by a tank truck. In addition, equipment such as meters and pumps 7 are provided on the surface to draw fuel oil from the underground tank 1 via the suction pipe 3 and measure the amount of fuel oil being drawn in. A valve 8 is provided on the injection pipe 2, and a valve 9 is provided on the suction pipe 3. A vent 10 is provided on the vent pipe 4 at a height of several meters above ground to discharge gas generated in the underground tank 1.

[0013] Figure 2 shows the cross-sectional configuration of the underground tank 1 with the above configuration. As shown in the figure, the injection pipe 2 (drop pipe) and the suction pipe 3 are fitted inside the underground tank 1, and the tip of the injection pipe 2 extends to near the bottom of the underground tank 1 to reduce the load on the liquid level during fuel injection. In addition, the suction pipe 3 extends to a position slightly above the bottom of the underground tank 1 to prevent the suction of slag and other substances inside the underground tank 1 and to safely suction the fuel oil inside the underground tank 1. Furthermore, the 11 shown in the figure indicates an opening used for maintenance of the underground tank 1.

[0014] Furthermore, in Figure 2, dotted circles A and B indicate the connection points where the injection pipe (drop pipe) 2 and suction pipe 3 are welded to and attached to the underground tank 1. Dotted circle A represents the part where the injection pipe 2 is welded to the underground tank 1, and dotted circle B represents the part where the suction pipe 3 is welded to the underground tank 1; both have essentially the same configuration. For example, FIG. 3 is a view showing a welded portion between the underground tank 1 and the injection pipe (drip pipe) 2.

[0015] Furthermore, FIG. 4 is a cross-sectional view for explaining the configuration near the connection portion between the underground tank 1 and the injection pipe 2. The injection pipe 2 is further provided with an upper flange 13. The tip of the injection pipe 2 is attached to this flange 13 by welding 13a. A plurality of tightening holes 13b are formed at equal intervals in the circumferential direction on this flange 13, and they are tightened in conformity with the tightening holes 14b formed in the flange 14 located above.

[0016] In addition, the flange 14 extends to a pipe joined to a lateral draw-off pipe (not shown). For example, the fuel oil to be injected is supplied to the injection pipe 2 through the lateral draw-off pipe.

[0017] As shown in FIG. 4, the injection pipe (drip pipe) 2 is attached to the steel plate of the underground tank 1 by welding 15. As described in the conventional example, the steel plate (iron) and another metal material are joined. Usually, due to the potential difference caused by the contact of dissimilar metals, the iron side corrodes, iron rust occurs, which causes cracks at the joint portion.

[0018] However, in the utility model registration of the present invention, for example, the above fluorine packing is interposed between the underground tank 1 and the injection pipe (drip pipe) 2 and they are connected (welded). Therefore, even when using an injection pipe 2 made of a material different from the steel plate (iron) of the underground tank 1, the injection pipe 2 does not directly contact the underground tank 1, and corrosion does not occur due to the corrosion mechanism caused by the contact of dissimilar metals, preventing corrosion of the welded portion and solving problems such as cracks and disconnection of the pipe.

[0019] In addition, in the description of this example, the injection pipe 2 has been described. The same applies to the suction pipe 3. When welding the suction pipe 3 to the underground tank 1, even when using a metal with a material different from the steel plate (iron) of the underground tank 1, the suction pipe 3 and the steel plate of the underground tank 1 do not directly contact, and corrosion does not occur due to the corrosion mechanism caused by the contact of dissimilar metals, solving problems such as cracks and disconnection at the connection portion.

Explanation of Reference Numerals

[0020] 1 ··· Underground tank for fuel storage 2 ··· Injection pipe 3 ··· Suction pipe 4 ··· Vent pipe 5 ··· Liquid level gauge 6 ··· Inlet 7 ··· Equipment such as gauges, pumps, etc. 8, 9 ··· Valves 10 ··· Vent 11 ··· Opening 13 ··· Flange 13a ··· Welded part 13b ··· Tightening hole 14 ··· Flange 14b ··· Tightening hole 15 ··· Welded part

Claims

1. Underground fuel storage tanks for storing fuels such as mixed gasoline and biomass fuel, An injection pipe is installed in the underground fuel storage tank and extends from the underground fuel storage tank to the outside, When welding the injection pipe to the underground fuel storage tank, the injection pipe is inserted into an opening made in the underground fuel storage tank, and the welded portion of the injection pipe is fitted with a fluorine packing. An underground tank for storing fuels such as organic solvents, including piping, and a means for preventing corrosion at the contact points with the piping inside the underground tank.

2. Underground fuel storage tanks for storing fuels such as mixed gasoline and biomass fuel, A suction pipe is installed in the underground fuel storage tank and extends from the underground fuel storage tank to the outside, When welding the suction pipe to the underground fuel storage tank, the suction pipe is inserted into an opening made in the underground fuel storage tank, and the welded portion of the suction pipe is fitted with a fluorine packing. An underground tank for storing fuel, including piping, and a means for preventing corrosion at the contact point with the piping inside the underground tank, characterized by these features.

3. The underground tank for storing bioethanol-blended gasoline and biodiesel fuel, and means for preventing corrosion of each pipe inside the underground tank, including the piping according to claim 1, characterized in that when the injection pipe is connected to the flange, the contact portion of the injection pipe is fitted with the fluorine packing.

4. The underground tank for storing bioethanol-mixed gasoline and biodiesel fuel, and means for preventing corrosion of each pipe inside the underground tank, including the piping according to claim 2, characterized in that when the suction pipe is connected to the flange, the contact portion of the suction pipe is fitted with the fluorine packing.

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