JP2017142096A - Leakage inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage inspection method which improves accuracy of leakage detection without a reduction in recovery rate of helium gas.SOLUTION: In a leakage inspection method, an inspection object member 30 is arranged in a chamber 15, gas is filled inside the inspection object member 30, and an amount of leakage of the gas to the inside of the chamber 15 is measured. The leakage inspection method includes steps of: measuring the amount of the leakage from a leakage master 13; calculating the concentration of the gas on the basis of the amount of the leakage from the leakage master 13; and correcting the amount of the leakage from the inspection object member 30 on the basis of the measured concentration of the gas.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a leak inspection method.

  As a container leak inspection method, a member to be inspected such as a container is accommodated in a chamber, the inside of the member to be inspected is evacuated, and then the member to be inspected is filled with helium gas to leak helium gas into the chamber. Methods for measuring quantities are known.

  For example, Patent Document 1 describes that helium gas used in a leak inspection method is recovered and reused.

Japanese Patent Laid-Open No. 10-311770

  However, since a small amount of air remains in the inspection target member that has been evacuated, the purity of the recovered helium gas is low when the pressure of the helium gas used for the leak inspection is low. FIG. 1 is a diagram comparing the ratio of helium gas to air. As shown in FIG. 1, while the amount of air remaining in the inspection target member is the same, the amount (number of moles) of helium gas varies depending on the pressure. Therefore, when the pressure of the helium gas decreases, the helium gas The ratio also decreases.

  As a result, if helium gas with low purity is reused for leak inspection, the ratio of helium gas in the leaking gas also decreases, so there is a large gap between the amount of leaked gas and the amount of helium gas detected by the detector. Therefore, there is a problem that the accuracy of the leak inspection is lowered. Further, when the helium gas used for the leak inspection is low, if the helium gas is discarded, there is a problem that the recovery rate of the helium gas is lowered. These problems are problems of not only helium gas but all gases used for leak inspection.

  A leak inspection method according to the present invention is a leak inspection method in which a member to be inspected is disposed in a chamber, a gas is filled in the member to be inspected, and a leak amount of the gas into the chamber is measured. The leak amount of the gas was measured, the concentration of the gas was calculated based on the leak amount of the leak master, and the leak amount of the inspection target member was corrected based on the measured gas concentration.

  According to the leak inspection method of the present invention, the leak amount of the leak master is measured, the gas concentration is calculated based on the leak amount of the leak master, and the leak amount of the inspection target member is corrected based on the measured gas concentration By doing so, a more accurate leak amount can be obtained in consideration of the amount of gas impurities used in the leak test, so that the accuracy of the leak test can be improved.

  Preferably, the leak inspection method of the present invention may purify the gas using a separation membrane when the measured concentration of the gas is less than a predetermined reference value.

  According to the leak inspection method of the present invention, when the measured gas concentration is less than a predetermined reference value, the gas concentration to be reused is improved by refining the gas using the separation membrane. The amount of gas impurities used in the process can be reduced, and the accuracy of leak inspection can be improved.

  The leak inspection method of the present invention can improve the accuracy of the leak inspection without reducing the recovery rate of helium gas.

It is a figure which compares the ratio of helium gas and air. 1 is a diagram illustrating a schematic configuration of a leak inspection apparatus according to a first embodiment; 3 is a flowchart showing a procedure of a leak inspection method according to the first embodiment; It is a graph which shows the relationship between the density | concentration of helium gas, and the amount of apparent leaks. It is a figure which shows schematic structure of the leak test | inspection apparatus concerning Embodiment 2. FIG. 10 is a flowchart illustrating a procedure of a leak inspection method according to the second embodiment;

(Embodiment 1)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram illustrating a schematic configuration of the leak inspection apparatus according to the first embodiment. In FIG. 2, lines connecting the components mean piping. In FIG. 2, the leak inspection apparatus 10 includes a cylinder 11, a return tank 12, a leak master 13, a chamber 14, a chamber 15, a detector 16, a vacuum tank 17, a vacuum pump 18, a compressor 19, And valves 20 to 26.

  The cylinder 11 is a cylinder filled with helium gas used for leak inspection. The cylinder 11 is connected to the return tank 12 by piping.

  The return tank 12 is a tank for recovering and storing the helium gas used for the leak inspection. The return tank 12 is connected to the leak master 13 via a valve 21 by piping, and is connected to the inspection target member 30 via a valve 23 by piping.

  The leak master 13 is a minute leak generator that leaks a certain amount of helium gas. The leak master 13 is disposed in the chamber 14.

  The chamber 14 is a container that houses the leak master 13. The chamber 14 stores helium gas leaked from the leak master 13. The chamber 14 is connected to the detector 16 through a valve 22 by piping.

  The chamber 15 is a container that accommodates the inspection target member 30 therein. The chamber 15 stores helium gas leaked from the inspection target member 30. Further, the chamber 15 is connected to the detector 16 via a valve 24 by piping, and is connected to the vacuum tank 17 via a valve 25 by piping.

  The detector 16 is an analyzer that measures the amount of helium gas. The detector 16 measures the amount of helium gas in the leak master 13 by measuring the amount of helium gas in the chamber 14. Further, the detector 16 measures the amount of helium gas in the inspection target member 30 by measuring the amount of helium gas in the chamber 15.

  The vacuum tank 17 is a tank that stores gas in the inspection target member 30 when the inspection target member 30 is evacuated. The vacuum tank 17 is connected to the vacuum pump 18 by piping.

  The vacuum pump 18 is a pump that evacuates the inspection target member 30 via the vacuum tank 17. For example, the vacuum pump 18 is preferably configured by combining a roughing pump and a dry pump. The vacuum pump 18 is connected to the compressor 19 by piping on the exhaust side.

  The compressor 19 is a compressor that pressurizes the helium gas sucked from the inspection target member 30 by a vacuum pump and sends it to the return tank 12. The compressor 19 is connected to the return tank 12 on the boosting side by piping.

  The valves 20 to 28 are valves that respectively circulate or close the piping.

  With the above configuration, the leak inspection apparatus 10 inspects the inspection target member 30 for leaks. Next, a procedure of a leak inspection method using the leak inspection apparatus 10 will be described. FIG. 3 is a flowchart of a procedure of the leak inspection method according to the first embodiment.

  In step S101, helium gas is supplied from the cylinder 11 to the return tank 12. After the return tank 12 is filled with helium gas, the valve is closed and the process proceeds to step S102. The pressure of the helium gas filled in the return tank 12 is at least equal to or higher than the pressure of the helium gas necessary for the leak inspection.

  In step S102, helium gas is supplied from the return tank 12 to the leak master 13 by opening the valve 21, and the process proceeds to step S103.

  In step S <b> 103, the helium gas leaked from the leak master 13 into the chamber 14 is led to the detector 16 by opening the valve 22. The apparent leak amount (helium gas amount) leaked from the leak master 13 is measured using the detector 16. Then, the concentration of helium gas used for the inspection is calculated from the apparent leak amount of the leak master 13. After the measurement, the valves 21 and 22 are closed, and the process proceeds to step S104.

  In step S104, helium gas is supplied from the return tank 12 to the inspection target member 30 by opening the valve 23, and the process proceeds to step S105.

  In step S <b> 105, the helium gas leaked from the inspection target member 30 into the chamber 15 is led to the detector 16 by opening the valve 24. The apparent amount of leak (amount of helium gas) leaking from the inspection target member 30 is measured using the detector 16. After the measurement, the valve 24 is closed and the process proceeds to step S106.

  In step S106, the amount of leakage from the inspection target member 30 is obtained by correcting the apparent leakage amount of the inspection target member 30 based on the concentration of the helium gas calculated in step S103. A specific leak amount calculation method will be described later. After obtaining the amount of leakage from the inspection target member 30, the process proceeds to step S107.

  In step S107, it is determined whether or not the leak amount from the inspection target member 30 is equal to or less than a predetermined value. If the amount of leak from the inspection target member 30 is equal to or less than the predetermined value, the process proceeds to step S108. If the amount of leak from the inspection target member 30 is larger than the predetermined value, the process proceeds to step S109.

  In step S108, it is determined that the airtightness of the inspection target member 30 is sufficiently maintained, and the process proceeds to step S110.

  In step S109, it is determined that the airtightness of the inspection target member 30 is not sufficiently maintained, and the process proceeds to step S110.

  In step S <b> 110, the valve 25 is opened, and the helium gas in the inspection target member 30 is collected in the vacuum tank 17. After collecting the helium gas, the valve 25 is closed and the process proceeds to step S111.

  In step S111, the valve 26 is opened and the vacuum pump 18 and the compressor 19 are operated, so that the helium gas in the vacuum tank 17 is filled in the return tank. After filling with helium gas, the valve 26 is closed and the process returns to step S101.

  By the above procedure, leak inspection and helium gas recovery are performed. Next, calculation of the leak amount will be described. FIG. 4 is a graph showing the relationship between the concentration of helium gas and the apparent leak amount. In FIG. 4, the vertical axis indicates the apparent helium gas leak amount (mL / min), and the horizontal axis indicates the helium gas concentration (vol%). As shown in FIG. 4, when the concentration of helium gas is 100%, the detector 16 of FIG. 1 can measure the total amount of leak, so that the apparent amount of leak of helium gas and the amount of leak of original helium gas are Match. on the other hand,

  When the concentration of helium gas is 50%, the detector 16 in FIG. 1 can measure 50% of the leak amount, and thus the apparent leak amount of helium gas is 50% of the original leak amount of helium gas.

  Thus, the concentration of helium gas and the apparent leak amount of helium gas are in a proportional relationship. Therefore, when applied to the leak master, the relationship of helium gas concentration (vol%) = apparent leak amount of the leak master / (when the helium concentration is 100 vol%) is established. Since the leak amount of the leak master is known, the concentration of helium gas can be calculated by measuring the apparent leak amount of the leak master.

  Furthermore, when the above relationship is applied to the inspection target member 30, the relationship of leakage amount of the inspection target member = apparent leakage amount of the inspection target member 30 / helium gas concentration (vol%) is established.

  Accordingly, the apparent leak amount of the leak master is divided by the leak amount of the leak master to calculate the concentration of helium gas, and the apparent leak amount of the inspection target member 30 is divided by the concentration of helium gas, so that the inspection target is obtained. The amount of leakage of the member 30 can be obtained.

  As described above, according to the leak inspection method of the first embodiment, the leak amount of the leak master is measured, the gas concentration is calculated based on the leak amount of the leak master, and the inspection target member is based on the measured gas concentration. By correcting the leak amount, a more accurate leak amount can be obtained in consideration of the amount of gas impurities used in the leak inspection, so that the accuracy of the leak inspection can be improved.

(Embodiment 2)
In the second embodiment, an example will be described in which helium gas with reduced purity is used for leak inspection. FIG. 5 is a diagram illustrating a schematic configuration of the leak inspection apparatus according to the second embodiment. In FIG. 5, the same components as those in FIG.
In FIG. 5, the leak inspection device 40 includes a cylinder 11, a return tank 12, a leak master 13, a chamber 14, a chamber 15, a detector 16, a vacuum tank 17, a vacuum pump 18, a compressor 19, Valves 20 to 26, a separation membrane 41, and valves 42 and 43 are provided.

  The separation membrane 41 is a separation membrane that separates helium in the gas from other molecules. As the separation membrane, a carbon membrane, a silica membrane, a polymer membrane and the like are suitable. The separation membrane 41 is connected to the exhaust side of the compressor 19 through a valve 42 by piping. The separation membrane 41 has a helium separation side connected to the vacuum tank 17 by piping, and a permeate gas side connected to the exhaust port by piping.

  The valves 42 and 43 are valves for circulating or closing the pipe. The compressor 19 is connected to the return tank 12 through a valve 43 by piping.

  With the above configuration, the leak inspection apparatus 40 inspects the inspection target member 30 for leaks, and further collects the helium used for the leak inspection in the return tank 12. Next, a procedure of a leak inspection method using the leak inspection apparatus 40 will be described. FIG. 6 is a flowchart of a procedure of the leak inspection method according to the second embodiment. In FIG. 6, the same steps as those in FIG.

  In step S <b> 103, the helium gas leaked from the leak master 13 into the chamber 14 is led to the detector 16 by opening the valve 22. The apparent leak amount (helium gas amount) leaked from the leak master 13 is measured using the detector 16. Then, the concentration of helium gas used for the inspection is calculated from the apparent leak amount of the leak master 13. After the measurement, the valves 21 and 22 are closed, and the process proceeds to step S201.

  In step S201, it is determined whether or not the calculated helium gas concentration is a sufficient helium concentration for a leak test. Specifically, in step S201, it is determined whether or not the calculated concentration of helium gas is equal to or higher than a predetermined concentration. If the calculated concentration of helium gas is equal to or higher than the predetermined concentration, the process proceeds to step S104. If the calculated concentration of helium gas is less than the predetermined concentration, the process proceeds to step S202.

  In step S104, helium gas is supplied from the return tank 12 to the inspection target member 30 by opening the valve 23, and the process proceeds to step S105.

  In step S202, the valves 42 and 43 are opened to increase the pressure of the helium gas in the return tank 12, supply the helium gas to the separation membrane 41, and the process proceeds to step S203.

  In step S203, the helium gas separated from the other gas in the separation membrane 41 is collected in the vacuum tank 17, and the process proceeds to step S111.

  In step S111, the valve 26 is opened and the vacuum pump 18 and the compressor 19 are operated, so that the helium gas in the vacuum tank 17 is filled in the return tank. After filling with helium gas, the valve 26 is closed and the process returns to step S101.

  As described above, according to the leak inspection method of the second embodiment, when the measured gas concentration is less than the predetermined reference value, the concentration of the gas to be reused is improved by purifying the gas using the separation membrane. Therefore, the amount of gas impurities used for leak inspection can be reduced and the accuracy of leak inspection can be improved.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, a configuration for calculating the concentration of helium gas used for inspection from the apparent leak amount of the leak master 13 and correcting the apparent leak amount of the inspection target member 30 based on the calculated concentration of helium gas. Thus, the configuration for calculating the leak amount from the inspection target member 30 may be realized by an electronic circuit using a CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit). Each valve may be opened and closed manually or automatically by a control circuit. In the above embodiment, helium gas is used for leak inspection, but leak inspection may be performed using other gases. For example, by using the flammable gas concentration outside the flammable range, the leak inspection apparatus can be applied without an explosion-proof structure.

20-28 Valve 20-26 Valve 10, 40 Leak Inspection Device 11 Cylinder 12 Return Tank 13 Leak Master 14, 15 Chamber 16 Detector 17 Vacuum Tank 18 Vacuum Pump 19 Compressors 21-26, 42, 43 Valve 30 Inspected Member 41 Separation film

Claims (2)

Place the inspection target member in the chamber,
Fill the inside of the inspection target member with gas,
A leak inspection method for measuring a leak amount of the gas into a chamber,
Measure the leak amount of the leak master,
Calculate the concentration of the gas based on the leak amount of the leak master,
A leak inspection method for correcting a leak amount of a member to be inspected based on the measured gas concentration.   The leak inspection method according to claim 1, wherein when the measured concentration of the gas is less than a predetermined reference value, the gas is purified using a separation membrane.

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