JPH04270932A - Leakage inspection apparatus - Google Patents

Abstract

PURPOSE:To rapidly inspect leakage with high sensitivity without masking a test part. CONSTITUTION:A leakage inspection apparatus 11 is constituted of a probe nozzle 12 sucking the gas to be inspected of the test part of an object A to be tested, a helium leak detector 13 detecting helium in the gas sucked from the probe nozzle 12, the flexible fine pipe 14 and connection conduit 15 connecting the probe nozzle 12 and the helium leak detector 13, the branch pipe 16 branched from the connection conduit 16, the high vacuum exhaust system 17 connected to the branch pipe 16 and the flow rate control valve 18 provided to the connection conduit 15 on the downstream side of the branch pipe 16.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a leak detection device.
In particular, the present invention relates to a device for detecting leaks in containers and pipes that require extremely high airtightness, such as vacuum devices such as nuclear fusion devices and accelerators, and shrouds of space chambers.

0002

BACKGROUND OF THE INVENTION Conventionally, a pressure sniffer method has been known as a method for detecting leakage from joints in the above-mentioned vacuum equipment, etc. As shown in Figure 3, this pressurized sniffer method involves introducing helium into the test object A from cylinder No. 1, pressurizing the inside to 1 atm or more, and leaking helium to the outside through minute gaps such as pinholes and cracks. A probe nozzle (sniffer) 2 sucks up a small amount of helium that leaks out, and a helium leak detector 3 detects this helium to detect a leak.

In the conventional pressurized sniffer method, the helium leak detector 3 alone takes in and exhausts gas, and the degree of vacuum inside the helium leak detector 3 is set to 10.
Since it was necessary to maintain the level at -4 Torr, the amount of suction gas was as small as 10-4 to 10-3 Torr·l/sec. For this reason, the helium released from the leak location could not be efficiently sucked in, and the time required to test one location was also long. Furthermore, if the probe is long, a realistic test time cannot be obtained, so it is necessary to perform the test by sampling with a syringe or the like.

[0004] On the other hand, Japanese Patent Application Laid-Open No. 60-133340
In the leak detection device described in the publication, a sorption pump cooled to below the liquid air temperature is arranged in series on the suction side of the helium leak detector to improve the performance of the device.

[0005] The above method uses a absorption pump to adsorb and remove nitrogen, oxygen, etc. in the gas sucked in from the probe nozzle, thereby increasing the suction amount at the probe nozzle, and also reducing the amount of gas actually sucked by the helium leak detector. is decreasing. Therefore, it is possible to significantly increase the suction amount at the probe nozzle, and it is possible to improve the helium detection sensitivity and shorten the detection time.

[0006]

However, in the method described in the above-mentioned publication, about 5 ppm of helium contained in the atmosphere passes through the sorption pump, is concentrated, and is sucked into the helium leak detector. In order to avoid exceeding the detection limit, it is necessary to mask the test part of the container with a polyethylene sheet, etc., and replace the inside of the polyethylene sheet with nitrogen gas to prevent the above-mentioned helium from being drawn into the atmosphere. Ta. Also, when moving the probe nozzle, it was necessary to take measures to prevent helium from being drawn into the atmosphere.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a leak detection device that can perform leak detection quickly and with high sensitivity without masking the test section.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the leak detection device of the present invention includes a probe nozzle for sucking a test gas, and a helium probe nozzle for detecting helium in the gas sucked from the probe nozzle. leak detector and
In a leak detection device equipped with a connecting conduit that communicates a probe nozzle and a helium leak detector, the probe nozzle is connected to the connecting conduit via a flexible thin tube,
Further, the connecting conduit is provided with a branch pipe, and the branch pipe is connected to a high vacuum exhaust pipe.

[0009]

[Operation] With the above configuration, the amount of gas suctioned from the probe nozzle can be increased by suctioning the gas from the test section using the helium leak detector and the high vacuum exhaust system. Furthermore, since helium concentration does not occur, leak detection can be performed without masking the test area.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below based on embodiments shown in the drawings. First, FIG. 1 shows a first embodiment of the present invention. This leak detection device 11 includes a probe nozzle 12 that sucks a gas to be detected in a test section of a test object A, a helium leak detector 13 that detects helium in the gas sucked from the probe nozzle 12, and a helium leak detector 13 that detects helium in the gas sucked from the probe nozzle 12. and the helium leak detector 13, a branch pipe 16 branching from the connection pipe 15, a high vacuum exhaust system 17 connected to the branch pipe 16, The flow rate regulating valve 18 is provided in the connecting conduit 15 on the downstream side of the pipe 16.

That is, the helium leak detector 13 and the high vacuum evacuation system 17 are arranged in parallel and configured so that they both suck the gas from the test section, increasing the amount of gas sucked from the probe nozzle 12 and The suction speed at step 12 is significantly increased compared to the conventional method shown in FIG.

The high vacuum evacuation system 17 is composed of a high vacuum evacuation pump 17a and a backup oil rotary pump 17b, and has a greater suction capacity than the helium leak detector 13. As this high vacuum exhaust pump 17a, various types can be used as long as they can efficiently suck air in a high vacuum state of 10-4 Torr or less, but in particular, a turbo molecular pump, an oil diffusion pump, etc. can be used. Accordingly, the probe nozzle 12
Even if the amount of gas sucked from the helium leak detector 13 is increased, it is possible to maintain the vacuum that operates the helium leak detector 13 and search for leaks.

A connecting conduit 15 downstream from the branch pipe 16
The flow rate adjustment valve 18 provided in the helium leak detector 13 further adjusts the intake gas amount of the helium leak detector 13, and a valve capable of adjusting the flow rate, such as a general needle valve, can be used. By providing the flow rate adjustment valve 18 in this way,
The suction pressure of the helium leak detector 13 can be adjusted to an optimal range, and the detection ability of the helium leak detector 13 can be maximized. Note that an orifice or a sintered metal leak may be provided in place of the flow rate control valve 18 to adjust the flow rate to an appropriate level. Furthermore, a high vacuum exhaust pump 17a is provided on the suction side of the high vacuum exhaust pump 17a.
A suction valve 19 is provided that can adjust the amount of suction.
This suction valve 19 is provided as appropriate depending on the suction capacity or operability of the high vacuum pump 17a and the helium leak detector 13, and may be omitted.

The flexible thin tube 14 connecting the probe nozzle 12 and the connecting conduit 15 improves operability and reduces S/N due to pulsation generated when sample gas is sucked from the pore of the probe nozzle 12. It is provided to improve the detection ability by improving the ratio, and can be formed from a flexible pipe, for example, a stainless steel pipe with an inner diameter of 1 mm or less and a length of several meters to several tens of meters. can. In addition, if the test object A is a large-scale device and high workability is required, the flexible thin tube 14 is made longer. This flexible thin tube 1
The inner diameter and length of 4 can be set as appropriate depending on the capacity of the high vacuum exhaust system 17, and the suction pressure of the high vacuum exhaust system 17 is 10
It is desirable to select it so that it is -2 Torr or less.

By configuring the leakage detection device 11 in this way, the suction speed of gas from the probe nozzle 12 can be greatly increased, and trace amounts of gas leaking out from the minute gaps in the test object A can be greatly increased. Helium can be efficiently sucked in by the probe nozzle 12. In addition, by branching the gas sucked from the probe nozzle 12 and sucking it in the high vacuum exhaust system 17 installed in parallel with the helium leak detector 13, it is possible to make the helium leak detector 13 suck the optimal amount of gas. Therefore, the exploration time can be shortened without impairing the detection sensitivity. Moreover, since no concentration of helium in the atmosphere occurs, there is no need to mask the test area, and the time required for masking is no longer required, resulting in improved workability.

[0016] Also in this embodiment, when exploring a very minute gap within a somewhat limited test area, the area around the test area is masked and the inside is replaced with nitrogen gas or the like. , background due to helium contained in the atmosphere can be completely removed, and detection sensitivity can be further improved.

Next, FIG. 2 shows a second embodiment of the present invention, in which a sorption pump 20 is disposed immediately before the helium leak detector 13 in the configuration of the first embodiment.

This sorption pump 20 is substantially the same as the one described in the publication cited in the conventional example and is used for the same purpose, but has the structure of the first embodiment.
By combining it with the leak detection device 11, it is possible to further improve the sensitivity.

That is, the high vacuum exhaust system 17 and the absorption pump 20 can suck a large amount of gas, and the helium can be concentrated by removing nitrogen, etc. from the gas sucked into the helium leak detector 13. It is also possible to detect very small amounts of helium leaking from the test section. However, in this second embodiment, in order to remove the background due to helium in the atmosphere as described above, it is preferable to apply masking 21 around the test section when performing high-sensitivity detection.

[0020] Therefore, by performing leakage detection using the apparatus according to the first embodiment of the present invention, the leakage portion can be quickly identified, although the sensitivity is somewhat sacrificed compared to the conventional apparatus. Normally, it is possible to identify most of the leak parts with this leak detection, but by further masking the test part and further using the device of the second embodiment, it is possible to perform leak detection with even higher sensitivity. This makes it possible to identify even the smallest pinholes and cracks.

[0021]Here, the results of an experiment conducted by the pressure sniffer method using the apparatus of the first embodiment will be explained. Using a sniffer with an inner diameter of 0.58 mm and a length of 30 m (consisting of a probe nozzle and a flexible thin tube), a vacuum pump with a suction capacity of 500 l/sec is connected in parallel with the helium leak detector, and the vacuum inside the helium leak detector 4 is degree 1
The temperature was set at 0-4 Torr.

The results of the blank test (atmospheric suction) showed that approximately 5 ppm of helium present in the atmosphere was detected.
There were 35 scales in 3 ranges. Then standard leak (2
．． As a result of suctioning 2×10-7 Torr・l/sec), 3
It reached 40 marks in the microwave. From this, if we consider that it is possible to detect a deviation of one scale in three ranges for a leakage point that is continuously released into the atmosphere, then from the following formula 1, It was confirmed that it was possible to continuously detect leaks.

[0023]

[Formula 1]

[0024]

[0025] Also, 6 kg/cm of helium was added inside the test body.
2 G and masking the test area with a polyethylene sheet for leak detection, the minimum detection sensitivity can be set to 1 x 10-9 Torr·l/sec or less. From this, it can be seen that by using the device of the second embodiment, it is possible to further lower the minimum detection sensitivity.

[0026]

[Effects of the Invention] As explained above, the leak detection device of the present invention uses a sniffer nozzle and a flexible By using a thin tube and installing a high vacuum exhaust system in parallel with the helium leak detector, it is possible to efficiently suck the gas from the test area, and it is also possible to suck the optimal amount of gas into the helium leak detector. Although the detection sensitivity is somewhat sacrificed due to the fewer concentration steps compared to the conventional method, the detection time can be significantly shortened, and the workability can be significantly improved in leak detection in large equipment, etc. Furthermore, since there is no concentration of helium in the atmosphere, there is no need to mask the test area, and workability is also good. Also,
By interposing a sorption pump before introduction into the helium leak detector, inspection can be performed with detection sensitivity as high as that of conventional methods.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a first embodiment of a leak detection device of the present invention.

FIG. 2 is an explanatory diagram similarly showing a second embodiment.

FIG. 3 is an explanatory diagram of the pressurized sniffer method.

[Explanation of symbols]

Claims (3)

[Claims] 1. A leak detection system comprising a probe nozzle that sucks a test gas, a helium leak detector that detects helium in the gas sucked from the probe nozzle, and a connecting conduit that communicates the probe nozzle and the helium leak detector. A leak detection device characterized in that the probe nozzle is connected to the connecting conduit through a flexible thin tube, a branch pipe is provided in the connecting conduit, and the branch pipe is connected to a high vacuum exhaust pipe. . 2. The leak detection device according to claim 1, wherein a sorption pump is interposed in the connecting conduit downstream of the branch pipe. 3. The leak detection device according to claim 1, further comprising a flow rate regulating valve for adjusting the amount of gas sucked into the helium leak detector in the connecting conduit downstream of the branch pipe.