JPH039037B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to underground tanks for gas stations. As is well known, at a gas station there are tanks buried underground that store the oil to be refueled. Therefore, the underground tank is connected to a plurality of pipes extending from the ground to the underground tank. The piping includes an oil supply pipe that supplies oil to an underground tank, a fuel supply pipe that supplies oil from the underground tank to a refueling machine, and an air vent pipe.

The underground tank is buried underground, and the surface above it is hardened with concrete. In addition, piping may crack or be damaged due to vibrations such as earthquakes. If such pipes crack or break, water will leak into underground tanks in the event of a flood or high groundwater level.

Cracks or damage to pipes can be repaired by replacing the pipes, but repairing them is relatively easy.
In order to take out the water that has flowed into the underground tank, the tank must be emptied, and oil contaminated with water or dirt cannot be used. The process is extremely difficult.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an underground tank for refueling in which the amount of water flowing into the tank from the outside when cracks or damage occur in the piping is minimized.

According to the underground tank for a gas service station of the present invention, a valve is provided in the pipe connected to the underground tank, and the pipe is connected to a riser pipe from the underground tank close to the underground tank, and the valve is installed in the underground tank. The valve is closed by a water detection signal from the water inflow detection means.

Generally, valves are installed via a risepipe because it is difficult to install them directly into an underground tank.
Since this riser pipe is short, the valve can be installed relatively firmly in the underground tank. Since this riser pipe is short, it is almost never damaged. Therefore, in the event that the piping on the upstream side (anti-tank side) cracks or breaks due to an earthquake, etc.,
Rainwater enters the underground tank through the pipes, but
Immediately, a water detection signal is output from the water inflow detection means in the underground tank, and the valve is closed in response to the signal. Therefore, water flowing into the pipe is blocked at the valve and does not flow into the underground tank.

In implementing the present invention, a liquid level gauge can be used as the water inflow detection means. That is, the liquid level in the underground tank should not change substantially except during or during refueling operations. Therefore, the liquid level is measured every fixed period of time, for example, 30 seconds, and if the liquid level rises even though no lubrication or refueling is performed, it is determined that water has flowed into the tank.
However, slight changes in measured values may occur due to temperature changes or other measurement errors, for example, so an error range is determined in advance, and an accident is assumed to have occurred when the liquid level changes beyond the error range. However, other optional water inflow sensing means may be utilized.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a gas station in which the present invention is implemented. In the figure, the site S of the gas station is paved with concrete C, and an underground tank 1 is buried underground. In the illustrated example, three pipes are connected to this underground tank 1. That is, the oil supply pipe 2 is for sending the oil O in the underground tank 1 to the oil supply machine 3 installed on the ground, and the oil supply pipe 4 is for supplying oil from the lorry (not shown) to the underground tank 1. And, in the opening 5 there is a lubricant switch.
SW ₁ is installed to detect when lubrication work is in progress. Furthermore, an air vent pipe 6 is provided.

These pipes 2, 4 and 6 are respectively connected to riser pipes R 1 _{and 6} installed in the underground tank 1, as shown in the figure.
Connected to installed valves V ₁ , V ₂ and V ₃ via R ₂ and R ₃ . The length from the underground tank 1 to each valve is short, so each valve V ₁ , V ₂ and V ₃ is provided close to the underground tank 1 . As will be described later, these valves V ₁ , V ₂ and V ₃ all prevent water from flowing in, so it is preferable to install them as close to the underground tank 1 as possible in the middle of the piping.

The nozzle hook 7 of the refueling machine 3 is provided with a nozzle switch SW ₂ for detecting that refueling work is in progress.

An office F is installed at the gas station, and an operating device 8 is installed inside the office F. This operating device 8 is a liquid level detector 9 installed in the underground tank 1.
An analog liquid level signal is converted into a digital liquid level signal by an A-D converter 10, which is then controlled by a control device (to be described later), displayed by a display meter 11, and printed by a printer 12. There is. In the figure, 13 is a keyboard. As the liquid level detector 9, it is preferable to use a capacitive liquid level measuring electrode. In the case of this capacitance type, the A-D converter 10
In this case, a device that converts capacitance into frequency is used.

However, in carrying out the present invention, a water detection means is provided at the bottom of the tank instead of a liquid level detector, and since oil is an insulator and water is a conductor, the water detection means is connected to an electrode by water. It is possible to use a device that detects water by short-circuiting.

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 2, components corresponding to those in FIG. 1 are given the same reference numerals.

The analog liquid level signal from the liquid level detector 9 is A-
It is converted into a digital liquid level signal by the D converter 10 and sent to the control device 20 via the AND gate 21. In the control device 20 , the relationship between the liquid level and the liquid amount is converted into a liquid amount by a calculation formula storage circuit 22 , and the liquid amount is displayed on the display 11 . It is ready for printing. The AND gate 21 is opened at predetermined time intervals, for example, every 30 seconds, by a signal from the control device 20, so that a liquid level signal is input to the control device at predetermined time intervals. Whether or not the gas station is performing refueling work or lubricating work can be known by the nozzle switch _SW2 or the refueling port switch _SW1 . That is, when the cover of the oil filler port is open, a signal is generated from the oil filler switch _SW1 , and this signal is sent to the control device 2 via the flip-flop circuit 23.
0 and it is detected that lubrication work is in progress. This flip-flop circuit 23 is also reset by a reset signal sent from the control circuit 20 at regular intervals after the lid is closed. When the nozzle is removed, the nozzle switch SW ₂ generates a signal indicating that the nozzle is being refueled, and this signal is sent to the controller via the flip-flop circuit 24 to detect that the nozzle is being refueled. This flip-flop circuit 24 is also reset by a reset signal from the control device. While signals are being output from these switches SW ₁ and SW ₂ , the liquid level comparison operation is not performed as will be described later. The liquid level signal from the liquid level detector 9 is calculated based on the calculation formula stored in the calculation formula storage circuit 22 as described above, converted into a liquid volume signal, and updated and stored in the liquid volume storage circuit 25. And the liquid volume is
It is displayed on the display meter 11.

When there is no signal from the switches SW ₁ and SW ₂ , that is, when lubrication work and refueling work are not performed, the liquid level signal from the liquid level detector 9 is determined by the calculation formula stored in the calculation formula storage circuit 22. is calculated based on and converted into a liquid volume signal, and this liquid volume signal is stored in the flow rate storage circuit 25. Next, when the AND gate 21 is opened by a signal from the control device 20, the liquid amount signal calculated from the input liquid level signal and the previous liquid amount signal are compared in the control device 20. If this comparison value exceeds a certain error range α, the control device 20 issues a valve closing signal to the valves V ₁ , V ₂ , V ₃ to close each valve V ₁ , V ₂ , V ₃ . At the same time, an alarm 26 is used to notify of an abnormality. In other words, if an abnormality is notified by the alarm 26, water will flow into the tank,
It is understood that oil spilled due to tank damage or theft. If the alarm indicates an abnormality, check for the abnormality and then open valves V ₁ , V ₂ , and V ₃ .

Next, the operation of the present invention will be explained with reference to FIG.

When the detection work of the control device 20 is started (step S ₁ ). From the control device 20 at regular intervals (for example,
30 seconds), a gate open signal is transmitted to the AND gate 21 (step S ₂ ). When the AND gate 21 is opened, the signal from the liquid level detector converted into a digital signal by the A/D converter 10 is input to the control device 20 via the AND gate 21 (step S ₃ ).
This liquid level signal is calculated using the calculation formula stored in the calculation formula storage circuit 22 to calculate the liquid amount (step S ₄ ). The previous (30 seconds ago) storage liquid volume is input from the liquid volume storage circuit 25 to the control device 20, and in the control device 20, “memory liquid volume + α”, which takes an error α into the storage liquid volume, is determined as the current liquid volume. (step _S5 ). If the current fluid volume is larger than "memory fluid volume + α", that is, if the oil in the tank has increased, then the oil is being refilled, and the lid of the opening 5 of the oil filling pipe 4 is opened and the oil is refilled. A signal indicating that the lubrication is in progress is transmitted from the lubrication switch _SW1 to the flip-flop circuit 23, and it is determined whether the signal is transmitted from the circuit 23 to the control device 20 (step _S6 ). If lubrication is not in progress, water or the like has flowed in from the outside, so the control device 20 generates a valve close signal, closes the valves _V1 to _V3 , and operates the alarm 26 (step _S7 ). If the alarm 26 is activated, immediately inspect it, find the cause of the abnormality, and repair it.

If lubricating work is in progress in step _S6 ,
A signal from the control device 20 resets the flip-flop circuit 23 (step S ₈ ), and the stored value in the liquid volume storage circuit 25 is updated to the currently calculated liquid volume value (step S ₉ ). Then return to step _S2 again. Note that in step _S8 , the reset signal of the flip-flop circuit 23 is sent to the AND gate circuit 21.
Similar to the open signal, it is sent at regular intervals, so
When oiling is in progress or if oiling ends slightly earlier than the specified time, a signal is input indicating that oiling is in progress, that is, replenishment is in progress.

Now, if it is not larger than "storage liquid amount +α" in step _S5 , it is determined whether or not it is smaller than "storage liquid amount - α" (step _S10 ). If it is not smaller than "memory fluid volume - α", that is, step S ₅
In step _S10 , the fact that it is not larger than "storage fluid amount +α" and not smaller than "storage fluid amount - α" means that there is no abnormality, and the process returns to step _S2 .

If it is smaller than "memory fluid amount - α" in step _S10 , refueling is in progress, and a signal indicating that refueling is in progress is transmitted from the nozzle switch SW ₂ of the refueling machine 3 to the flip-flop circuit 24. From there, it is determined whether the signal is being transmitted to the control device 20 (step S ₁₁ ). If refueling is not in progress, it means that there is an abnormality and the amount of oil in the tank has decreased, so activate the alarm 26 (step
_S12 ). If refueling is in progress, the flip-flop circuit 24 is reset (step _S13 ), and the liquid amount stored in the liquid amount storage circuit 25 is updated to the current calculated value (step _S14 ). Similar to step _S8 , in step _S13 , if refueling is in progress or if the refueling operation has just been completed, a signal indicating that refueling is in progress is inputted via the flip-flop circuit 24. Step S ₁₄ while refueling
Return to step _S2 . Note that a microcomputer can be used as the control device 20.

This cycle is repeated, for example, every 30 seconds.

As described above, according to the present invention, since a control device is provided that closes the valve based on the water detection signal from the water inflow detection means, when water flows into the underground tank due to a crack or breakage of the pipe due to vibration, the control device closes the valve immediately. The valve can be closed to prevent water from entering. Therefore, in the past, inspections were performed at most once every week, and oiling and refueling operations were carried out without knowing that water had entered, but by implementing the present invention, it is possible to immediately prevent abnormalities. can.

In carrying out the present invention, the alarm may be installed at a security company or at the home of the owner of the gas station, which is located far from the gas station, so that abnormalities can be immediately known after the store is closed for the night.

[Brief explanation of the drawing]

FIG. 1 is a side view of a gas station implementing the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG.
The figure is a flowchart showing one embodiment of the present invention. SW ₁ ...Oil filling port switch, SW ₂ ...Nozzle switch, 2, 4, 6...Piping, 9...Liquid level detector, 20...
Control device, V ₁ , V ₂ , V ₃ ...valve.

Claims (1)

[Claims] 1. A valve is installed in the pipe connected to the underground tank, and the valve is connected to the riser pipe from the underground tank close to the underground tank, and the water detection signal from the water inflow detection means installed in the underground tank is detected. An underground tank for a gas filling station, characterized in that the valve is closed when the valve is closed.