JPH034917Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a leakage inspection device for underground tanks.
In particular, the present invention relates to an underground tank leakage testing device that tests for the presence or absence of leakage based on changes in the atmospheric pressure inside the underground tank.

(Prior art) Conventionally, this type of underground tank leakage inspection device removes the liquid stored in the underground tank, pressurizes the tank with nitrogen gas, and then detects pressure fluctuations in the underground tank. A device was used to measure and record it on a recorder as a curve or numerical value.

(Problem that the invention aims to solve) However, with such underground tank leakage testing equipment, the stored liquid must be removed from the underground tank for inspection and stored, which is time consuming and costly. In the past, there was a problem in that safety was poor, and the accuracy of the test was also poor because it was impossible to detect subtle changes in atmospheric pressure using only recorder records.

Therefore, the main purpose of this invention is to provide an underground tank leakage testing device that does not require removing stored liquid from the underground tank and has high testing accuracy.

(Means for solving the problem) This invention is an inspection device that depressurizes the inside of an underground tank and inspects for leakage. An ejector that depressurizes the inside of an underground tank, a connecting pipe that has one end connected to the ejector and the other end connected to a through hole in the underground tank, and that has a spouting part in a part, and a spout of a connecting pipe. a first pressure gauge that measures over time the atmospheric pressure in the underground tank that is connected to the depressurized underground tank; a self-recording means that records the value of the first pressure gauge; a second pressure gauge for measuring the atmospheric pressure in the underground tank over time, and an image recording means for recording an image of at least a display section of the second pressure gauge;
This is a leak inspection device for underground tanks.

(Operation) The pressure inside the underground tank is reduced by the ejector using an inert gas without removing the stored liquid. Meanwhile, changes in the atmospheric pressure inside the underground tank during measurement are recorded using images and a self-recorder.

(Effects of the invention) According to this invention, the inside of the underground tank is depressurized by the ejector using inert gas without removing the stored liquid, so the inspection can be completed in a shorter time than before. Moreover, even if the liquid stored in the underground tank is easily combustible, there is no risk of ignition or explosion.

In addition, since the atmospheric pressure inside the underground tank is recorded by image recording means and self-recording means, even subtle changes in atmospheric pressure can be accurately measured.
The accuracy of the test will be higher.

The above-mentioned objects, other objects, features and advantages of the present invention will become clearer from the following detailed description of embodiments with reference to the drawings.

(Embodiment) FIG. 1 is an illustrative diagram showing an embodiment of this invention. The underground tank leak testing device 10 includes an ejector 12 having three openings. The first opening 12a of the openings of this ejector 12 is
It is connected to the first valve 14 and, via a flexible pipe 16, to a pressure reducing device 18.
This pressure reducing device 18 is connected to, for example, a nitrogen gas cylinder 20 which serves as a supply source of inert gas, and these act as means for introducing the inert gas. Note that the pressure reducing device is provided because the atmospheric pressure inside the nitrogen gas cylinder 20 is too high, so this pressure is reduced to about 5 atmospheres, for example, and then sent to the ejector 12.

A connecting pipe 26 is connected to the second opening 12b formed at a right angle to the first opening 12a. This connecting pipe 26 is connected to the metering hole 24a of the underground tank 24 via the backflow prevention part 22, for example, by being screwed. In addition, connecting pipe 2
6, as shown in FIGS. 2A and 2B,
It is formed so that it can also be connected to the injection hole 25 of the underground tank 24 or the ventilation pipe 27.

Furthermore, an exhaust port fitting 28 is formed in the third opening 12c located at a position facing the first opening 12a. As shown in FIGS. 3A and 3B, this exhaust port fitting 28 has a dome shape, and a wire mesh 28a is stretched on the bottom surface of the exhaust port fitting 28.
Nitrogen gas and gas flowing out from inside the underground tank 24 are released through this wire mesh 28a in a direction opposite to the direction inside the ejector 12. This wire mesh 28a
is a wire mesh for fire prevention that is unlikely to catch fire even if combustible gas is released, and is made of a metal that does not easily corrode, such as copper or stainless steel, and is made of, for example, 40 mesh. Note that the exhaust port fitting 28 may be formed into a semi-ellipsoidal shape, as shown in FIGS. 4A and 4B, for example, in order to adjust the exhaust amount. Therefore, by sending nitrogen gas from the pressure reducing device 18, the pressure inside the underground tank 24 can be reduced by the action of the ejector 12.

The connecting pipe 26 is further provided with a spouting portion, in which a second valve 30 is formed. This second valve 20 is connected to one connection part of a U-shaped differential pressure gauge 34, which serves as a second pressure gauge, through one end of a rubber tube 32 that splits into two from the middle.

In the vicinity of this U-shaped differential pressure gauge 34, a recorder 36, which has a Bourdon tube or the like as a first pressure gauge and serves as a self-recording means for recording changes in the atmospheric pressure inside the underground tank 24, is provided. and,
The recorder 36 is connected to the other of the forked rubber tubes 32, so changes in the atmospheric pressure inside the underground tank 24 can be measured using the U-shaped differential pressure gauge 34 and the recorder 3.
6 can be measured simultaneously.

On the other hand, the display section of the U-shaped differential pressure gauge 34 and the recorder 3
A small video camera device 38, which serves as an image recording means, is installed at a position where both images and images can be captured in the same image.

Furthermore, a microphone 40 extends into the underground tank from this small video camera device 38, and in parallel with image capture, sounds generated within the tank (for example, the sound of dripping underground water, injection pipes blowing outside air into the tank, etc.) It is now possible to record.

Next, an underground tank leakage testing device using this underground tank leakage testing device 10 will be described in detail.

First, prior to the inspection, all openings in the underground tank 24 that communicate with the outside air are closed. Next, the first valve 14 and the nitrogen gas cylinder 20 are opened, the pressure of the nitrogen gas is lowered by the pressure reducing device 18, and the nitrogen gas is caused to flow into the ejector 12, thereby reducing the pressure inside the underground tank 24.

When the difference between the atmospheric pressure inside the underground tank 24 and the outside atmospheric pressure reaches, for example, 250 to 500 mmH ₂ O, the first valve 14 and the nitrogen gas cylinder 20 are closed, and the pressure reducing device 18 is stopped. Note that this underground tank leakage testing device can perform sufficiently accurate testing when the difference between the atmospheric pressure inside the underground tank and the outside pressure is 1000 mmH ₂ O or less.

The atmospheric pressure of the underground tank 24, which has been depressurized in this way, is
The U-shaped differential pressure gauge 34 and a first pressure gauge provided in the recorder 36 measure the pressure over time.

In parallel with this, the small video camera 38 is operated to record the display of the U-shaped differential pressure gauge 34 as an image over time. At this time, the recorder 36 may be placed within the same image. In this embodiment, since the U-shaped differential pressure gauge 34 and the recorder 36 are included in the same image, more subtle changes in atmospheric pressure can be captured. The measurement and recording time is, for example,
It takes about 30 minutes to 1 hour.

In the depressurized underground tank 24, the gas concentration becomes low, so the liquid stored in the underground tank 24 gradually vaporizes until the inside of the underground tank 24 reaches a saturated vapor pressure. Therefore, the atmospheric pressure inside the underground tank 24 increases for a while after starting measurement. However, as the vapor pressure approaches the saturated vapor pressure, the increase in atmospheric pressure slows down and eventually reaches an equilibrium state where it takes a nearly constant value. However, if there is a leak in the underground tank 24, outside air will be injected through the crack or hole that causes the leak, so the pressure inside the underground tank 24 will continue to increase until it becomes almost the same as the outside pressure. Therefore, in the recording by the recorder 36 and the image recording by the U-shaped differential pressure gauge 34, if the atmospheric pressure in the underground tank 24 is in an equilibrium state,
It can be determined that there is no leakage, and conversely, if the atmospheric pressure continues to increase in these records, it can be determined that there is a leakage. In addition, in this invention, if the inspection is performed through the underground tank 24 and its piping section, the underground tank 24 and its piping section can be inspected at one time.

Additionally, if the temperature rises within the underground tank 24,
The stored liquid evaporates and the atmospheric pressure increases even if there is no leakage. For this reason, it is desirable to measure the temperature inside the underground tank 24 before and after the inspection.

In addition, in this embodiment, since the sound inside the underground tank 24 is recorded in parallel with the measurement of the atmospheric pressure, it is possible to not only determine whether there is a leak but also to estimate the location of the leak. In other words, if there are cracks or holes in the underground tank 24, the pressure inside the underground tank 24 is reduced, so outside air or groundwater will be injected. Since the sound of bubbles generated when bubbles are generated or the sound of dripping underground water, etc. can be heard, the location of the leak can be estimated from this data, for example, as follows.

(1) No leakage when there is no increase in atmospheric pressure and no abnormal sounds.

(2) When there is an increase in atmospheric pressure and the sound of outside air being injected, there is a leak above the level of the stored liquid in the underground tank.

(3) If there is an increase in atmospheric pressure and there is no abnormal noise, there is a high possibility that there is a leak in the piping.

(4) When there is an increase in air pressure and the sound of bubbling, there is a leak below the liquid level in the underground tank.

(5) When there is no significant increase in atmospheric pressure and there is a dripping sound There is a leak in the upper part of the underground tank or in the piping.

Note that the mutual relationship between these data changes depending on the shape of the underground tank, the location of the underground tank, the location of the piping, etc., so the judgment must be made according to each condition. Furthermore, if it is determined that there is a leak, it goes without saying that the leak location is inspected in detail using, for example, a fiberscope.

Furthermore, since this invention uses an image recording means, it is possible to prove which underground tank was inspected by capturing an image of the surrounding area of the underground tank at the same time as recording the atmospheric pressure.

In this embodiment, a small video camera device 38 is used as the image recording means, but a camera may also be used instead. Furthermore, although nitrogen gas was used as the inert gas in this example, carbon dioxide may also be used. Further, in this embodiment, the test was performed by connecting the connecting pipe 26 to the metering hole 24a of the underground tank 24, but the test may be performed by connecting it to, for example, a ventilation pipe or an injection hole.

Note that if the pressure inside the underground tank 24 is reduced, buckling may occur due to negative pressure, but this is because the difference between the atmospheric pressure inside the underground tank and the outside pressure is 0.9 Kg/cm ² (9000 mmH ₂ O).
Accidents occur due to the above, and in this invention, the difference is at most 0.1Kg/cm ² (1000mmH ₂ O), so
Such accidents do not occur.

[Brief explanation of the drawing]

FIG. 1 is an illustrative diagram showing an example of a device for carrying out this invention. Figures 2A and 2B are illustrative diagrams showing the state in which the connecting pipe is connected to the through hole of the underground tank, Figure 2A shows the state in which it is connected to the ventilation hole, and Figure 2B is the connection to the injection hole. Indicates the condition.
3A and 3B show the exhaust port fitting of this embodiment, FIG. 3A is a sectional view thereof, and FIG.
The figure is a plan view showing the back side thereof. 4A and 4B show other exhaust port fittings, FIG. 4A is a sectional view thereof, and FIG. 4B is a plan view showing the back side thereof. In the figure, 10 is an underground tank leak inspection device, 12 is an ejector, 24 is an underground tank, 34 is a U-shaped differential pressure gauge, 36 is a recorder, and 38 is a small video camera device.

Claims (1)

[Claims for Utility Model Registration] 1. An inspection device for inspecting the presence or absence of leakage by reducing the pressure inside an underground tank, comprising means for introducing an inert gas into the underground tank by introducing the inert gas into the underground tank. an ejector for reducing pressure inside the underground tank, one end of which is connected to the ejector and the other end of which is connected to a through hole of the underground tank;
Furthermore, a connecting pipe having a spouting part in a part thereof, a first pressure gauge connected to the spouting part of the connecting pipe and measuring the atmospheric pressure in the depressurized underground tank over time; a self-recording means for recording the value of the pressure gauge; a second pressure gauge connected to the outlet of the connecting pipe and measuring the atmospheric pressure in the depressurized underground tank over time; and at least the second pressure A leakage inspection device for an underground tank, including an image recording means for recording the display part of the meter as an image. 2. A request for registration of a utility model that includes a sound collector placed in the underground tank and for recording the sound inside the underground tank while the atmospheric pressure is being measured, and a recording device for recording the sound collected by the sound collector. Leakage testing equipment for underground tanks as described in item 1. 3. The image recording means includes a video camera device, as claimed in claim 1 or 2 of the utility model registration claim.
Leakage testing equipment for underground tanks as described in Section 1. 4. The underground tank leakage inspection device according to any one of claims 1 to 3, wherein the image recording means includes a camera. 5. The underground tank leakage inspection device according to any one of claims 1 to 4, wherein the inert gas includes nitrogen gas. 6. The underground tank leakage inspection device according to any one of claims 1 to 5, wherein the inert gas includes carbon dioxide.