JP2518486Y2 - Double-shell tank grounding device - Google Patents

Description

[Detailed Description of the Invention] (Industrial application field) The present invention relates to a grounding device for a double-shell tank that stores a combustible liquefied gas such as LPG or LNG, and in particular, an external device having a concrete peripheral wall with low electrical conductivity. In the metal inner tank inside the tank, static electricity generated by receipt and payment of the stored liquid, or lightning that strikes the outer tank metal roof is safely guided to the outside of the tank and discharged.
The present invention relates to a grounding device that prevents electrostatic charge in a tank.

(Problems to be solved by the prior art and the invention) The combustible liquefied gas of LPG and LNG is a metal made of steel for low temperature, which is provided inside the outer tank having a concrete peripheral wall that also acts as a liquid barrier through a cold insulation layer. It is stored in the inner tank. For this double-shell tank consisting of an inner tank and an outer tank, static electricity generated by receiving and discharging combustible liquefied gas and lightning strike electricity received on the outer tank metal roof part can cause fire and explosion. It is necessary to keep the inside of the container always in an antistatic state.

In particular, it is extremely important from a safety point of view to prevent electrification of a metal inner tank that stores flammable liquefied gas installed inside an outer tank made of a concrete material with low electrical conductivity and a cold insulation layer that is easy to electrically insulate. It's important.

In the conventional grounding device for double-shell tank, a lightning rod is installed in the upper part of the tank and a grounding plate embedded in the ground is connected by a grounding wire such as a copper wire to discharge lightning electricity into the ground and generate it in the inner tank. The static electricity was passed through the outer tank bottom and the outer tank peripheral wall between the inner tank of the electric conductor and the buried earth plate, or was connected to the ground wire via the outer tank roof part and discharged underground. It was preventing the charge inside the tank.

However, if a long ground wire is used for grounding, the path is likely to be hindered, and curing and protecting the elongated ground wire has been a difficult task. Further, in order to obtain the discharge effect of the buried ground plate, it was necessary to dig the ground plate to a certain depth of groundwater and bury it, or improve the soil around the ground plate to reduce the ground resistance.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the grounding device of the double-shell tank of the present invention uses an inner metal roof of a metal inner tank and an outer metal roof of a concrete outer tank to be electrically connected. An inner / outer tank connection that connects to the conductor is provided, and the upper part of the metal pipe standing upright on the outer wall of the outer tank concrete wall is electrically connected to the outer metal roof, and rainwater that falls on the outer metal roof is grounded. It is formed by electrically connecting the discharge electrode buried in the ground below the lower end of the rain gutter that guides to the lower part of the metal pipe.

(Effect) Lightning strike electricity received on the outer metal roof of the concrete outer tank where lightning strikes easily flows from the outer metal roof to the metal pipe standing upright on the outer concrete wall of the outer tank, and from the metal pipe to the lower end of the rain gutter. Is discharged to the ground via the discharge electrode buried in the ground below. In addition, static electricity generated by taking in and out of the storage liquid flows from the metal inner tank to the outer metal roof part through the inner and outer tank connection parts, and discharges to the ground from the outer metal roof part through the aforementioned metal pipes and discharge electrodes. To be done. In this way, lightning strike electricity and static electricity are discharged underground, so the double-shell tank is always in an antistatic state.

In addition, the soil around the discharge electrode buried in the ground below the rain gutter receives rainwater and is always in a wet state, so ground resistance is reduced, and electrical connection to the groundwater route is facilitated. Since it reduces the ground resistance, it increases the discharge effect in the ground.

(Example) An example of a grounding device for a double-shell tank according to the present invention will be described with reference to the drawings.

The double shell tank (1) for storing combustible liquefied gas is a spherical outer tank metal roof part on the outer concrete wall (9) of the outer tank that is erected on the outer peripheral edge of the concrete base that also serves as the foundation and bottom slab. It is formed by a concrete outer tank (2) provided with (4) and a metal inner tank (3) made of a low temperature steel material provided inside the outer tank (2) via a cold insulation layer and a maintenance space.

The flammable liquefied gas such as LPG and LNG is stored in the inner metal tank (3), and the outer concrete tank (2) is equipped with a cold insulation layer to store the flammable liquefied gas stored in the inner metal tank (3) outside. In addition to protecting against further heat intrusion, it also functions as a liquid barrier for preventing the outflow of the stored liquid from the metal inner tank (3) by the outer tank concrete peripheral wall (9) of the prestressed concrete.

The grounding device provided in this double-shell tank is first provided with an inner / outer tank connecting portion (6) for coupling the inner tank metal roof portion (5) and the outer tank metal roof portion (4) to electric conduction, Static electricity generated by receipt and payment of the storage liquid in the tank (3) is conducted to the outer tank metal roof part (4) of the concrete outer tank (2). The inner / outer tank connecting portion (6) has connecting terminals attached to the outer surface of the inner tank metal roof portion (5) and the inner surface of the outer tank metal roof portion (4), and a copper wire or the like between the connecting terminals via a heat insulating electric conductor. Although it is not shown in the drawing, the metal pipes from the concrete outer tank (2) connected to the inner metal tank (3) with a heat insulating material, for example, the outer tank metal roof part (4) are formed. ) And an inner tank metal roof (5) penetrating the storage liquid receiving and delivering pipe connected to electric conduction to form heat insulation and electric conduction by cutting off heat conduction. To form.

Next, a metal pipe (1) in which a rain gutter (7) that guides rainwater that has fallen on the outer tank metal roof (4) to the ground is formed with an electrical conductor.
1) Or, although not shown, the upper part of the metal pipe (11) such as the rising pipe of the sprinkler for sprinkling the outer tank metal roof part (4) and the outer tank concrete peripheral wall (9) and the outer tank metal roof part (4) ) Attach the connection terminals to the outer surface and connect the connection terminals with an electric conductor such as copper wire.

The rain gutter (7) is a drainage pit (10) partially buried in the ground from a water collecting part that acts as a corridor above the outer concrete wall of the outer tank (9) that collects rainwater that has fallen on the outer metal roof (4) of the outer tank. A metal pipe (11) in the shape of a cylinder or a prism that guides rainwater up to the outside of the outer circumferential concrete wall (9) is vertically supported and supported.

Furthermore, the metal body forming the discharge electrode (8) embedded in the ground below the lower end of the rain gutter (7), that is, the metal inner tank (3), the outer tank metal roof (4), and the metal pipe (11). A flat plate or rod formed more electrically of a base metal such as aluminum material is connected to a connection terminal attached to the lower end of the metal pipe (11) by an electric conductor such as a copper wire.

The discharge electrode (8) is located in the lower part of the rainwater drainage pit (10) below the rain gutter (7) in the middle of the flow path where rainwater becomes groundwater.
It is buried in a position where the soil around the discharge electrode (8) tends to be always in a wet state.

When the plurality of discharge electrodes (8) are connected to each other by an electric conductor, the ground resistance is further reduced and the underground discharge effect is increased.

For connection with all electric conductors, select a cross-sectional area and material that can conduct sufficiently even if high-voltage electricity such as lightning strikes flows.

As described above, the lightning strike electricity is applied to the outer tank metal roof (4).
Through the metal pipe (11) and the discharge electrode (8) buried under the rain gutter (7) into the ground, and the static electricity generated in the metal inner tank (3) is transferred to the metal inner tank (3). 3) Discharge to the ground through the inner / outer tank connection part (6), the outer tank metal roof part (4), the metal pipe (11) and the discharge electrode (8) under the rain gutter (7). Formed on the grounding device of heavy shell tank.

(Effect) As described above, the grounding device of the double shell tank is provided with the inner / outer tank connecting portion between the inner tank metal roof portion and the outer tank metal roof portion, and the outer tank metal roof portion and the metal pipe, and the metal pipe. The grounding device for the double-shell tank according to the present invention is excellent in the discharging effect in the ground and has less failure in the grounding path, by forming the discharge electrode in the ground below the rain gutter electrically. In addition, it has effects such as not lowering the low temperature cooling effect.

[Brief description of drawings]

FIG. 1 is a partially cutaway sectional view showing an embodiment of a double shell tank grounding device according to the present invention. 1 …… Double-shell tank 2 …… Concrete outer tank 3 …… Metal inner tank 4 …… Outer tank metal roof 5 …… Inner tank metal roof 6 …… Inner / outer tank connection 7 …… Rain gutter 8 …… Discharge electrode 9 …… Outer tank concrete peripheral wall 10 …… Drainage pit 11 …… Metal piping

Claims (1)

(57) [Scope of utility model registration request] 1. A grounding device for a double-shell tank for storing flammable liquefied gas, wherein a metal inner tank having an inner tank metal roof portion is provided inside a concrete outer tank having an outer tank concrete peripheral wall and an outer tank metal roof portion. In, an inner / outer tank connecting portion for connecting the inner tank metal roof portion and the outer tank metal roof portion to electric conduction is provided, and the upper portion of the metal pipe standing upright on the outer peripheral of the outer tank concrete peripheral wall and the outer tank metal roof portion are electrically connected. In addition, it is formed by electrically connecting the discharge electrode embedded in the ground below the lower end of the rain gutter that guides rainwater that has fallen on the outer metal roof part to the ground and the lower part of the metal pipe. A double-shell tank grounding device.