JPH0210036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for maintaining and inspecting buried tanks at gas stations and the like.

[Conventional technology]

After buried tanks and their attached piping in gas stations and the like are buried underground, it is not easy to inspect their condition from above ground.

Therefore, in order to check for oil leakage from buried tanks, pipes, etc., the following pressurization tests or depressurization tests are used.

(1) A method to check the presence or absence of a liquid phase part.

As shown in Fig. 4, a float C is floated in a tank B buried below the ground A, and this is connected to a leak recorder installed at the measuring port D to record the liquid level in the tank B. Measure the presence or absence of fluctuation over a period of 10 hours or more to confirm that no fluctuation occurs.

(2) Method of conducting a decompression test.

The openings of the tank B shown in FIG. 4, such as the suction pipe E and the oil supply pipe F, are closed with valves, and the ventilation pipe G or metering port D is closed with a blind plate or the like.

Next, the amount of hazardous materials in tank B is measured, the space volume is calculated, and the amount of hazardous materials necessary to achieve a predetermined reduced pressure value is extracted.

A manometer and a pressure recorder (both not shown) are attached to measure pressure fluctuations over a certain period of time.

(3) Method to check for leaks in underground piping, etc.

Close the opening of each pipe with a valve or blind plate, and attach a pressurizing device (thermometer), pressure gauge, and pressure recorder.

Next, water or nitrogen gas is filled in, and the pressure inside the pipe is increased to normal pressure using a pressurizing device.
Measure pressure fluctuations.

[Problem that the invention seeks to solve]

All of the above-mentioned test methods have been tried experimentally, but they have problems when used as leakage tests for underground tanks already buried in gas stations.

That is, it is difficult to carry out because the workability is poor and the inspection jig must be manufactured to match the metal fittings of the underground tank.

Therefore, there is a need for a better method for internal inspection and maintenance management of underground tanks themselves.

[Means for solving problems]

The present invention makes it possible to easily perform maintenance and inspection of a buried tank by digging a hole in the ground and installing a manhole communicating with an existing tank in the hole.

The method for maintenance and inspection of a buried tank according to the present invention involves draining the oil in the tank buried underground, injecting water instead to remove the gas, and then digging a hole in the ground that reaches the top of the tank. A manhole is inserted into the hole, its lower end is brought into contact with the upper surface of the tank, and a hole is bored in the upper surface of the tank on the inner surface of the manhole, thereby communicating the inside of the tank with the manhole. This method is characterized by draining water from the tank, entering the tank through a manhole, and inspecting the tank and its attached piping.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on FIGS. 1 to 3.

As shown in Fig. 1, residual oil in a tank 2 for gasoline at a gas station, for example, which is buried approximately 1 m or less below the concrete layer 1a of the ground 1, is extracted with a suction pipe 3, and fresh water H is supplied instead. It is sent from the fuel supply pipe 4 to fill the tank 2.

In order to completely remove residual oil or gas from the tank 2, after putting dry ice into the tank 2 through the metering port 5, a gas detector ( Confirm by measuring with an oxygen concentration meter).

Next, the concrete layer 1a is cut with a concrete cutter at a key point of the tank 2, that is, above a location where a manhole 7 with a flange, which will be described later, is to be attached, over a length of about 1 m square.

Next, dig down to the top of the tank 2 and make the concave hole 9.
A metal pipe 9 is properly fitted into the inner surface of this recessed hole 9, and then earth is secured.

After removing the asphalt anticorrosive agent on the upper surface 2a of the tank 2 exposed in the recessed hole 9, in the example, a manhole 7 with a diameter of 45 cm is placed, and its lower end surface is welded to the upper surface 2a of the tank 2. During this welding work, the interior of the metal tube 8 is filled with a sufficient amount of carbon dioxide gas (CO ₂ ) to prevent any accidental ignition caused by residual gas or the like. Instead of welding, bonding, bolting, etc. may be used.

A hole 20 is bored at a location corresponding to the bottom surface of the manhole 7 on the upper surface 2a of the tank 2, and the manhole 7 and the inside of the tank 2 are communicated with each other.

This drilling operation will be explained with reference to FIG. 2.

10 is a drilling machine, a motor 13 is attached to the upper end of a vertical cylindrical main body 12 attached to a horizontal base plate 11;
Further, a downwardly directed cylindrical blade body 15 with a bottom is protruded below the main body 12 via a vertical cylinder 14.

A blade is cut on the lower edge of the blade body 15, and the blade body 15
A piston 16 provided in the middle of a rotating shaft 15a standing upright from the center of the upper surface of the cylinder 14 rotates within the cylinder 14 and moves up and down. Rotating axis 1
The upper end portion of 5a is linked to the output shaft of the motor 13.

17 is a hose that connects the cylinder 14 to an air pressure source, and 18 is an operation panel of the drilling machine 10.

The board 11 is airtightly attached to the flange 7a at the upper end of the manhole 7. A water pipe 19 for injecting water into the manhole 7 is provided through the substrate 11 .

The blade body 15 is injected into the manhole 7 through the water pipe 19, and the motor 13 is driven to rotate the blade body 15, and pressurized air is sent above the piston 16 to lower the rotating shaft 15a. A hole 20 is made in the upper surface of the tank 2.

After drilling the hole 20 in the tank 2, the drilling machine 10 is removed.

Next, the water in the tank 2 is drained, the air in the tank 2 is replaced, and the inside is cleaned.

Finally, an inspector enters the tank 2 through the manhole 7 and performs various inspections such as a visual inspection of the interior, measurement of the tank and piping thickness, and the presence or absence of leaks in the tank piping.

As a result of the inspection, if necessary, we will paint the inside of the tank or repair the underground pipes, and if it is determined that the tank is not durable, we will replace the tank with a new one.

After completing the inspection and repair, the manhole 7 is sealed with a cover plate 21 and the metal pipe 8 is closed, as shown in FIG.
The empty space is filled with soil 22 and its surface is covered with a concrete plate 23.

If maintenance and inspection become necessary again several years later, by removing the concrete plate 23 and soil 22 and removing the cover plate 21, the tank 2 can be maintained and inspected again using the manhole 7. Can be done.

〔Effect of the invention〕

According to the present invention, by simply attaching a manhole directly to a buried tank, a worker can directly enter the tank to perform maintenance and inspection.

Therefore, leakage tests on buried tanks and their piping, which have conventionally been left unattended for many years, can be quickly and reliably carried out, contributing to the safety management of tanks and the safe operation of gas stations, etc.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of a buried tank with a manhole attached according to the present invention, FIG. 2 is a longitudinal sectional side view showing the procedure for drilling holes in the tank, and FIG. FIG. 4 is a longitudinal sectional front view of the buried tank for explaining a conventional tank leakage test method. 1...ground, 1a...concrete layer, 2...
Tank, 2a...Top surface, 3...Suction pipe, 4...Refueling pipe, 5...Measuring port, 6...Vent pipe, 7...Manhole, 7a...Flange, 8...Metal pipe, 9...
...Concave hole, 10...Drilling machine, 11...Substrate, 12...
...Body, 13...Motor, 14...Cylinder, 1
5... Blade body, 15a... Rotating shaft, 16... Piston, 17... Hose, 18... Operation panel, 19...
Water pipe, 20...hole, 21...cover plate, 22...
Earth, 23... Concrete board.

Claims (1)

[Claims] 1 After draining the oil in the tank buried underground and injecting water in its place to release the gas, dig a hole in the ground that reaches the top of the tank, then insert a manhole into the hole and open the bottom end of the hole. by contacting and fixing the tank to the top surface of the tank, making a hole in the top surface of the tank on the inner surface of the manhole to communicate the inside of the tank with the manhole, and then draining the water in the tank, A method for maintenance and inspection of a buried tank, characterized by entering the tank through a manhole and inspecting the tank and its attached piping.