JP2009025277A - Method of inspecting leakage from underground tank by leaked water flow detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein 80-180 minutes or more of inspection time is required per one tank container in a conventional technique, and wherein a time of stopping business in a gasoline station until finishing the inspection of a plurality of underground tanks is required to be shortened at an early time, as a reason for solving early the problem, since a simple method realized early of about 40 minutes of inspection time is required in its initial stage, even when either of water or air exists in the periphery of a storage tank buried underground. <P>SOLUTION: The water continuously intrudes into an underside of an oil liquid stored in the tank container, as a slow water flow, when the water continuously intrudes from a leakage hole by depressurization. This method of the present invention uses a leaked water flow detector having a function capable of detecting the intrusion moving and the water flow of the slow water. The water flow detector is provided in a short period, in case of a simple method, and is advanced successively to high performance one capable of shortening further the inspection time, by complicating a little accompanying mechanical structure or the like. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a leakage inspection method stipulated by law of a dangerous goods storage tank container buried underground in a gas station.

Japanese Patent Publication No. 2005-265469 discloses a method in which an acceleration sensor detects vibrations that occur when bubbles burst when air enters the oil contained in the container by reducing the pressure inside the container. However, there is a drawback that the direct relationship between the magnitude of the vibration that bursts the bubble and the size of the leak hole is thin, and in order to solve the disadvantage, in Japanese Patent Publication No. 2006-29835, air vibration is detected by an acoustic sensor. The detection method is adopted.
However, when rainwater or groundwater stays around the leak hole of a tank container buried in the ground, water enters from the leak hole. This method is also impossible, and there is still a problem that measurement and inspection are impossible because bursting due to bubbles cannot occur.

Therefore, in the leak inspection stipulated by law, only one of the above methods and only a method that obligates the method of detecting the rise in the water level in the tank container are approved.
However, the method of detecting the rise in the water level requires an inspection time of 80 to 180 minutes per tank container, and the time until the inspection of a plurality of underground tanks is further increased. There is a problem that requires the stand to be closed.
For this reason, there is a need for a leak inspection method for underground tank containers at gas stations that can be inspected in a short time.
Japanese Laid-Open Patent Publication No. 2005-265469 Japanese Laid-Open Patent Publication No. 2006-29835

If rainwater or groundwater stays in the vicinity of the leak hole of a tank container buried in the ground, vibrations such as inflow sound when water enters the container and propagation are difficult. In the acceleration sensor method and the acoustic sensor method based on the principle of detecting vibration, it is impossible to detect leak holes, so only the method used in combination with the method for detecting the rise in the water level in the tank container is approved.
However, in order to detect the rise in water level, an inspection time of 80 to 180 minutes is required for each tank container, and the time at which the operation of the gas station is stopped until the inspection of multiple underground tanks is completed can be shortened. Is urgently required.
Therefore, it is possible to use a method that can be realized quickly even with a simple and low-performance inspection time of about 40 minutes, and it is better if the method can be expected to further shorten the inspection time if the mechanism is somewhat complicated in the future.

Even if the gas phase part where the air above the tank container exists is decompressed, if there is no leak hole, water flow can occur in the liquid contained in the large tank container that is buried underground and sealed. In other words, the liquid is stationary, there is no pressure difference in the liquid, and it is in a very stable state.
On the other hand, when water continues to enter from the leak hole by reducing the pressure to a certain value, the water continues to move while entering as a gentle water flow under the oil liquid such as gasoline inside the tank container.
The problem can be solved by a method using a gentle water intrusion movement and a water flow detector having a function of detecting a gentle water flow.
There is a need for a simple and low-performance method that can be quickly implemented, so even if it is initially low-performance, it can be easily converted into a high-performance product by adding some complexity to the mechanical mechanism associated with the water flow detector. The inspection time can be further shortened sequentially.

Even if there is water or air around the storage tank buried in the ground, the method of leak inspection of the gas tank underground tank container that can be inspected is initially simple and low performance even for about 40 minutes There is a need for a method that can be realized quickly, so it can be realized from the method that can be realized as soon as possible. In turn, the inspection time can be further shortened.
The immediate reason is that an inspection time of 80 to 180 minutes or more is required for each tank container, and it is urgently requested to shorten the time at which gas station operations are stopped until the inspection of multiple underground tanks is completed. Because it is.

Even when the gas phase part where the air above the tank container is present is decompressed to a certain value, if there is no leakage hole, water flows into the liquid contained in the large tank container buried underground and sealed. Cannot occur, the liquid is stationary, there is no pressure difference in the liquid, and it is in a very stable state.
On the other hand, when water continues to enter from the leak hole, water heavier than oil such as gasoline stored in the tank container continues to move as a gentle water flow below the oil.
This is a leakage inspection method for determining the presence or absence of leakage holes in an underground tank using the leakage water flow detector 1 having a function of detecting a gentle movement of water and a gentle water flow. FIG. 1 is the best in the embodiment. It is a form.

Hereinafter, the operation of the leaked water flow detector and an embodiment will be described.
The details of how water enters the oil liquid is that the pressure inside the tank container is reduced to a constant value, so that the water that continues to enter from the minute leak holes initially had pressure oscillations as dense waves. Although it is a water flow, it gradually becomes a dense wave flow with gentle pressure oscillation, and water that is heavier than oil such as gasoline inside the tank vessel penetrates as a gentle water flow below the oil, pushing the oil Keep moving while spreading.

The details of the state of pressure change at this time are such that the water that is the front in the direction of the water flow and the oil liquid on the rear surface are spread with a slight pressure difference (weight difference, gravity difference). , Water slowly enters the oil liquid.
At the same time, water entering from the leak hole is accompanied by gentle pressure vibration as a sparse and dense wave, so that the front surface of the water flow has a high pressure value and a slight vibration, and the rear surface has a low pressure value and little vibration.

  If the decompressor is stopped and opened to atmospheric pressure, water intrusion from the leak hole stops, and the pressure values of all sensors remain the same and have the same pressure value output. There is nothing.

FIG. 2 is a top view of an example of a leaky water flow detector arranged radially using a plurality of high-sensitivity pressure sensors 9, and by calculating the difference in pressure obtained at each position, Even with a moving and gentle water flow, the presence or absence of a leak hole can be detected by the principle described above.
Further, the leaked air vibration detector 2 of the prior art is used in combination for the case where air enters, but there is no problem because the inspection time of about several minutes is sufficient for detection of air vibration.

  At first, a simple and low-performance method that can be quickly implemented is required. Therefore, FIG. 3 shows leakage water flow detection in which high-sensitivity pressure sensors 9 are radially arranged around the outer shell 1 of the tubular water flow detector. It is a side view of an example of a vessel, and the measurement of the pressure value distribution of each sensor when the pressure reduction is stopped and stabilized at atmospheric pressure, and the pressure value distribution when stabilized at a predetermined pressure reduction is repeated several times. The presence or absence of a leak hole can be detected by comparing the pressure value distribution of each sensor in each state.

  In the future, the distance between radial sensors will be improved by developing more sensitive pressure sensors and putting a pressure sensor at the tip of the frame structure of an umbrella, for example, to install more pressure sensors. The inspection time can be further shortened sequentially, for example, the pressure difference is improved due to the increase in the interval.

  FIG. 4 shows an embodiment in which the water level rise detecting means 10 of the prior art is added to the method of the present invention in order to adapt to the method approved by the current statutory law. The period until the product is approved is for the purpose of inspecting by the conventional method and deepening the performance evaluation and performance of the method of the present invention.

In the best mode of the embodiment, this is an inspection method for determining the presence or absence of leakage holes in an underground tank using a leakage water flow detector. It is a top view of an example of a leak water flow detector which has arranged a plurality of highly sensitive pressure sensors radially. It is a side view of the example of the simple leak water flow detector which has arrange | positioned the highly sensitive pressure sensor radially around the outer periphery of a cylindrical water flow detector. This is an embodiment in which a water level rise detection means of the prior art is temporarily added to the method of the present invention for the purpose of adapting to a method approved by the current statutory law.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Leakage water flow detector 2 Leakage air vibration detector 3 Electric processing part (Including leak signal calculation processing, measurement data display, and output function)
4 Depressurization means 5 Underground tank container to be measured 6 Outer shell of underground tank container 7 Leakage hole 8 Water flow 9 High sensitivity pressure sensor 10 Water level rise detection means

Claims (2)

  As shown in FIG. 1, a leaked water flow having a function of detecting a water flow 8 flowing into the tank container from a leak hole 7 existing in the outer shell 6 of the underground tank container 5, which is an object to be measured embedded in a gas station. A feature that uses the detector 1 and a feature that completes the measurement and inspection time of the leak hole within 60 minutes, and that does not require the installation of a water level rise measuring function inside the tank vessel 5 Leaked air vibration detector 2 having a function of detecting vibration when air flows in from the hole, an electrical processing unit 3 including a leak signal calculation process, measurement data display and output function, and a decompression means 4 are attached. Leak inspection machine for underground tank container of gas station by method.   4. A leak inspection machine for an underground tank container of a gas station to which a water level rise detection means 10 is temporarily added as shown in FIG.

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