JPH09145525A - Leak detector and detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect leakage of liquid from a container by a structure wherein an enclosed container containing a liquid communicated with a perfectly enclosed container containing a liquid and a gas through a U-tube containing a liquid for detecting pressure variation and the level of liquid for detecting pressure variation is detected. SOLUTION: When the inner pressure of an enclosed container 1 is equal to that of an enclosed container 2, the liquid 6 in a U-tube for detecting pressure variation has same liquid level on the left and right. This pressure state is sustained for a predetermined time before inspecting leakage of fluid from the container 1. When the fluid leaks from the container 1, inner pressure of the container 1 decreases to cause level difference of the liquid 6. Since the container 2 has perfectly enclosed structure, inner pressure thereof is not varied but a reference pressure is sustained. Consequently, the level of liquid 6 varied immediately upon lowering of pressure in the container 1, and the leakage of fluid from the container 1 can be detected with high sensitivity. It can be detected with higher sensitivity by decreasing the inside diameter of U-tube 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak detecting method and a leak detecting device for detecting a liquid leak in a closed container containing a liquid.

[0002]

2. Description of the Related Art Conventionally, in the case of detecting a liquid leak from a closed container containing a liquid, a visual method, a method of detecting a change in internal pressure with a pressure gauge, or JP-A-3-21044 is used.
This is based on the liquid leak test method by pressure detection with a calibrator, which is disclosed in Japanese Patent Publication No.

The visual method is a method in which an inspection operator visually confirms the presence or absence of liquid leakage. The method of detecting a change in internal pressure with a pressure gauge is a method of detecting a small amount of liquid leakage based on a decrease in pressure using a pressure gauge having high sensitivity. On the other hand, in the liquid leak test method, after the pressure inside the inspection system circuit to which the inspection target is connected is raised to a predetermined pressure, the inspection system circuit is closed and immediately after that, the internal volume of the inspection system circuit is reduced by a predetermined volume. To raise the pressure in the inspection system circuit slightly, then leave it for a certain detection time, and judge whether the sealing property of the inspection target is good or not based on the degree of pressure drop in the inspection system circuit during the detection time. Is the way to do it.

[0004]

In such a leak detection method using visual inspection or a pressure gauge, when the leak amount of the liquid is small or the volume of the residual air in the closed container is large,
Liquid leakage may be overlooked. In addition, with the method using a pressure gauge and the liquid leak test method, even if a high-sensitivity pressure gauge is used, even if a very small amount of leak is detected, the leak detection limit will be exceeded and the liquid leak in the sealed container will be reliably detected. However, there is a problem that it is difficult to automate the leak inspection of the closed container. In view of such a problem, the present invention is a leak detection method and a leak detection device capable of reliably detecting a liquid leak with high sensitivity even when the liquid leak is very small and residual air is present in the closed container. The purpose is to provide.

[0005]

A leak detecting method according to a first aspect of the present invention is a leak detecting method for detecting the presence or absence of a leak in a first closed container containing a liquid, wherein a gas and a first liquid are filled at a predetermined pressure. The completely closed second closed container and the first closed container were made to communicate with each other through a U-shaped tube containing the second liquid, and the internal pressures of the first closed container and the second closed container were set to the same pressure. After that, the liquid leakage of the first closed container is detected by detecting the change in the liquid level of the second liquid.

A leak detecting device according to a second aspect of the present invention is a leak detecting device for detecting whether or not there is a leak in a first closed container containing a liquid, wherein the gas and the first liquid are completely sealed at a predetermined pressure. Two closed containers, a U-shaped tube for containing the second liquid for communicating the second closed container and the first closed container, and a first interposed between the first closed container and the second closed container A valve, a second valve interposed between the first closed container and one side of the U-tube, and a third valve interposed between the second closed container and the other side of the U-tube. It is characterized by

In the present invention, as shown in FIG. 3, the second liquid 6
The U-shaped tube 4 containing the
It is interposed between the closed container 2. A large amount of the liquid W is put in the first closed container 1 and a small amount of the first liquid W is put in the second closed container 2 by an appropriate means. Then, a small amount of liquid W for pressurizing is put in the first closed container 1 and a gas A is put in the second closed container 2 to increase the internal pressure of the first closed container 1 and the second closed container 2 to the same pressure. Then, the liquid level of the second liquid 6 becomes the same level as shown in FIG.

When the liquid W leaks from the first closed container 1 after maintaining the closed state, the internal pressure thereof decreases. Since the second closed container 2 is completely closed, the gas A and the first liquid W do not leak and the internal pressure does not change. Therefore, as shown in FIG. 3 (b), the liquid level of the second liquid 6 on the side connected to the first closed container 1 rises, and the liquid level of the side connected to the second closed container drops to the liquid level. Level difference occurs. This liquid level difference depends on the amount of liquid leakage of the first closed container 1. Accordingly, when the liquid level difference of the second liquid in the U-shaped tube is detected, the presence or absence of liquid leakage in the first closed container can be determined.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing an embodiment of the invention. 1 is a first embodiment of a leak detection device for carrying out the leak detection method according to the first invention.
FIG.

Embodiment 1 A closed container 1 which is a leak inspection target filled with a liquid W at a predetermined pressure, and this closed container 1
And a liquid W and air A, which are the same pressure as the internal pressure of, and are connected to a completely closed airtight container 2 that holds a reference pressure, via a U-shaped pipe 4 connecting a pipe line 5. ing.
The U-shaped tube 4 has the curved portion 4a located on the lower side, and in the U-shaped tube 4, a change in internal pressure of colored aniline, oil, mercury or the like is detected over a length portion slightly longer than the curved portion 4a. The working liquid 6 is contained in the liquid W so that it is not mixed with the liquid W so that the liquid level can be clearly detected. Closed container 1
And a U-shaped pipe 4 are in communication with each other. A pipe line 5 is in communication with the pressure pump 3. The inner diameter of the U-shaped tube 4 is selected to be smaller than the inner diameter of the conduit 5.

Next, the operation of this leak detection device will be described.
When the internal pressure of the closed container 1 and the internal pressure of the closed container 2 are the same, the left and right liquid levels of the internal pressure change detection liquid 6 in the U-shaped tube 4 are at the same height. The sealed container 1 is held under such a pressure condition for a predetermined time, and the liquid leakage of the closed container 1 is inspected. Here, if the liquid leaks in the closed container 1, the internal pressure of the closed container 1 decreases, and a difference occurs in the liquid level of the internal pressure change detection liquid 6. That is, the liquid level on the side connected to the closed container 1 rises, and the liquid level on the side connected to the closed container 2 drops accordingly.

Since the closed container 2 has a completely closed structure, the internal pressure of the closed container 2 does not change and holds the reference pressure. Therefore, when the internal pressure of the closed container 1 decreases, the liquid level of the internal pressure change detection liquid 6 immediately changes, and the liquid leakage of the closed container 1 can be detected with high sensitivity. Further, by making the inner diameter of the U-shaped tube 4 smaller, liquid leakage can be detected with higher sensitivity.

Further, by multiplying the inner diameter of the U-shaped tube 4 by 1/2 of the length of the liquid level difference of the internal pressure change detecting liquid 6, the liquid leakage amount of the closed container 1 can be calculated from the multiplication result. Can be detected. Therefore, when residual air exists outside the liquid in the closed container 1, liquid leakage occurs, and a liquid level difference occurs in the internal pressure change detection liquid 6 even if the internal pressure change is slight. Liquid leakage can be detected with high sensitivity. Then, by grasping the change of the liquid surface level in the U-shaped tube 4 by using the light source and the CCD or the phototransistor, it is possible to determine the presence or absence of the liquid leakage in the electric signal, and the automation can be achieved.

In the case where the sealed container 1 to be leak-checked is replaced and a new sealed container 1 is leak-checked, after the conduit 5 connecting the sealed container 1 and the U-shaped pipe 4 is closed by an appropriate means. , The closed container 1 is replaced, and the internal pressure is changed to the closed container 2.
After adjusting the internal pressure to the same, the closed container 1 and the U-shaped tube 4 again.
By communicating with, the internal pressures of the closed containers 1 and 2 can be balanced and the liquid leakage can be inspected as described above.

Embodiment 2 FIG. 2 is a schematic diagram of a second embodiment of a leak detection device for carrying out the leak detection method according to the first invention. A closed container 1 that is a liquid leakage inspection target filled with the liquid W at a predetermined pressure and a completely closed structure closed container 2 that is filled with the liquid W and the air A at a predetermined pressure and holds the predetermined pressure are The passage 5 and the valve 7, which is the first valve, communicate with each other. A pressure gauge 9 is connected to a pipe line 5 that connects the closed container 1 and the valve 7. Further, the closed container 1 and the closed container 2 are connected to each other through a pipe line 5, a valve 8 as a second valve, a U-shaped pipe 4, and a valve 10 as a third valve in series.

The conduit 5 communicating with the closed container 1 and the valve 8 is communicated with the pressure pump 3 via a valve 11 which is a fourth valve. The U-shaped tube 4 has its curved portion 4a located on the lower side, and in the U-shaped tube 4, changes in the internal pressure of colored aniline, oil, mercury, etc. over a length portion slightly longer than the length of the curved portion 4a. The detection liquid 6 is put in so that the liquid level of the internal pressure change detection liquid 6 can be clearly detected in the same manner as described above. The inner diameter of the U-shaped tube 4 is selected to be smaller than the inner diameter of the conduit 5.

Next, the operation of this leak detection device will be described.
First, the valves 8 and 10 are closed, and the valves 11 and 7 are opened.
Then, the pressure pump 3 is driven to supply the liquid W into the closed containers 1 and 2, and the pressure gauge 9 is monitored to raise the pressure to a predetermined pressure. Thereby, the internal pressures of the closed container 1 and the closed container 2 become the same pressure. Here, the valve 11 and the valve 7 are closed. Then, when the valves 8 and 10 are opened, the same pressure is applied to one side and the other side of the U-shaped tube 4, and the liquid level of the internal pressure change detection liquid 6 becomes the same level. This state is maintained for a predetermined time to inspect the closed container 1 for liquid leakage. Here, if liquid leaks in the closed container 1, the internal pressure of the closed container 1 decreases, and a difference occurs in the liquid level of the internal pressure change detection liquid 6. That is, the liquid level on the side connected to the closed container 1 rises, and accordingly the liquid level on the side connected to the closed container 2 drops. By detecting this liquid level difference, liquid leakage in the closed container 1 can be detected.

When the inner diameter of the U-shaped tube 4 is multiplied by ½ of the length of the liquid level difference of the internal pressure change detecting liquid 6,
The liquid leakage amount of the closed container 1 can be detected from the multiplication result. As described above, since the closed container 2 has the completely closed structure, the internal pressure thereof does not change, and the reference pressure can be maintained. Therefore, when liquid leaks in the closed container 1, even if the leak amount is very small, a difference occurs in the liquid level of the internal pressure change detecting liquid 6 by making the inner diameter of the U-shaped pipe 4 small. Thus, liquid leakage can be detected with high sensitivity.

Further, when the closed container 1 is replaced and a liquid leak of a new closed container 1 is inspected, the valves 7, 8, 11 are used.
After closing the container and replacing the closed container 1, the valve 1
1, 7 are opened, and the internal pressure of the closed container 1 and the closed container 2 is set to a predetermined pressure by the pressure pump 3. Then, by closing the valves 7 and 11 and opening the valves 8 and 10, it is possible to detect the liquid leakage of the new closed container 1 as described above.

In the first and second embodiments, the U-shaped tube 4
When using oils having a smaller specific gravity than the liquid to be placed in the closed containers 1 and 2 as the internal pressure change detecting liquid 6 to be put in
The curved portion 4a of the character tube 4 is located on the upper side. That is, reverse U
Liquid leakage can be detected by detecting the liquid surface level in the same manner as when the colored aniline or mercury is put in by raising the U-shaped tube 4 so as to have a character shape.

In order to confirm the effect of the present invention, a sluice valve for water supply (JISB2026 150) is used instead of the closed container 1.
When the water pressure test of the valve box pressure resistance test and the valve seat leak test was performed using A) with the internal pressure set to a predetermined pressure, even if residual air was present in the sluice valve, the rate 1 specified in ISO 5280 , It was confirmed that the evaluation of rate 2 can be distinguished.

[0022]

As described above in detail, according to the present invention, there are provided a first closed container containing a liquid to be leak-checked and a second closed container having a completely closed structure containing the first liquid and gas. A U-shaped tube containing the second liquid is interposed between them to detect the liquid level of the second liquid after the inner pressures of the both closed containers have been made the same, and to detect the liquid leakage of the first closed container. Since it detects the presence or absence,
Liquid leakage of the first closed container can be detected with high sensitivity without using a pressure gauge as in the conventional case. Therefore, it is possible to provide a leak detection method and a leak detection device capable of automating the liquid leak test of the first closed container using a signal obtained by electrically detecting the liquid level.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a first embodiment showing a configuration of a leak detection device according to the present invention.

FIG. 2 is a schematic diagram of a second embodiment showing a configuration of a leak detection device according to the present invention.

FIG. 3 is an explanatory diagram of a principle of leak detection.

[Explanation of symbols]

 1, 2 Closed container 4 U-shaped pipe 6 Liquid for detecting internal pressure change 7, 8, 10, 11 valve

Claims (2)

[Claims] 1. A leak detection method for detecting whether or not there is a leak in a first closed container containing a liquid, comprising: a completely closed second filled with gas and a first liquid at a predetermined pressure.
The closed container and the first closed container are filled with a second liquid U
After making the internal pressures of the first closed container and the second closed container equal to each other by communicating through the character tube, the liquid in the first closed container is detected by detecting the change in the liquid level of the second liquid. A leak detection method characterized by detecting a leak. 2. A leak detection device for detecting the presence or absence of a leak in a first closed container containing a liquid, comprising a completely closed second closed container to be filled with gas and the first liquid at a predetermined pressure, and the second closed container. A U-shaped tube for containing a second liquid for communicating the airtight container and the first airtight container;
A first valve interposed between the closed container and the second closed container;
A second valve interposed between the first closed container and one side of the U-tube, and a third valve interposed between the second closed container and the other side of the U-tube. Leak detection device.