Leak detection device and leak detection method for detecting gas leaks in test specimen

Abstract

An improved leak detection device and an improved method for detecting gas leaks in a test specimen are provided. A leak detection device for detecting a gas leak in a test specimen includes a port 20 for a test specimen or a test chamber for accommodating the test specimen, and a gas conduit 22 connected to the port 20. The gas conduit 22 includes a valve 27 for selectively closing the gas conduit 22. The gas conduit 22 includes a compression pump 32 such that an inlet of the compression pump 32 is connected to the port 20 via the gas conduit 22 and an outlet of the compression pump 32 is connected to the valve 27 via the gas conduit 22, and the gas conduit 22 is connected to a pressurized volume 34 located between the outlet of the compression pump 32 and the valve 27 such that the compression pump 32 compresses gas from the port 20 into the pressurized volume 34 when the valve 27 is closed, and the pressurized volume 34 is connected to a gas pressure sensor 24 for measuring the pressure inside the pressurized volume 34.

Description

[Technical field]

[0001] The present invention relates to a leak detection device and a leak detection method for detecting a gas leak in a test specimen. [Background technology]

[0002] Integral leak detection checks for the presence or absence of gas leakage from a test specimen without locating the location of the gas leak. The test specimen may be contained in a test chamber connected to a gas detector. The test specimen is pressurized with the test gas while the test chamber is evacuated or at least the pressure inside the test chamber is lower than the pressure inside the test specimen. Alternatively, the test specimen contained in the test chamber or in the test enclosure may be connected to a gas detector and evacuated while the test chamber or the test enclosure is pressurized with the test gas, e.g. room air. Integral leak detection can determine the presence or absence of a leak without locating the leak.

[0003] Typically, integral leak testing is performed using a mass spectrometer, where the test chamber is evacuated by a pre-vacuum pump and / or turbomolecular pump, and the amount of test gas in the gas mixture to be analyzed is measured in vacuum by a mass spectrometer. Measuring the amount of test gas in this way is also called partial pressure measurement. The amount of test gas is a measure of the leak rate of the test specimen. In principle, an increase in the measured partial pressure of the test gas can be an indication of a leak. An increase in the measured value of the test gas or the amount of increase (partial pressure increase per unit time) above a certain threshold value is an indication of a leak. Alternatively, a decrease in the amount of test gas (e.g. the amount of test gas inside the test specimen) can be detected and evaluated.

[0004] The accumulation principle consists in measuring the total pressure rise, i.e. the absolute pressure rise or rise rate (total pressure rise per unit time) within a measurement volume, i.e. the test chamber containing the pressurized test object, over a certain period of time. The test chamber is then closed. Alternatively, it is conceivable to detect, for example, a drop in the total pressure by observing the pressure in the pressurized test object as an indication of a leak. As soon as the change in pressure (i.e. the rise or fall in the total pressure) exceeds a certain threshold, this is taken as an indication of a leak. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide an improved leak detection apparatus and an improved method for detecting gas leaks in a test specimen. [Means for solving the problem]

[0006] A device according to the invention is defined by the features of claim 1. A method according to the invention is defined by the features of claim 12.

[0007] According to the invention, the gas conduit is provided with a port for a test specimen or a test chamber for accommodating the test specimen. The gas conduit is provided with a valve closing the downstream part of the gas conduit, i.e. the part of the gas conduit opposite the port. The direction of gas flow is considered to be from the port towards the valve. In this respect, the port is located along the gas conduit upstream of the valve and the valve downstream of the port. A compression pump is provided in the gas conduit between the valve and the port, between which a pressurized volume is formed, the inlet of the compression pump being connected to the port and the outlet of the compression pump being connected to the pressurized volume. As a result, gas flows from the port along the gas conduit through the compression pump into the pressurized volume. The closed valve prevents gas from continuing to flow downstream of the gas conduit from the pressurized volume in the downstream direction. The compression pump compresses gas flowing from the specimen or test chamber through the port, the gas conduit, and into the pressurized volume, so that the pressure of the gas inside the pressurized volume is higher than the pressure inside the port and the gas conduit upstream of the compression pump. The pressurized volume is formed separately from the gas conduit and is fluidly connected to the gas conduit. Typically, the pressurized volume has an inlet connected to an outlet of the compression pump and an outlet connected to the valve.

[0008] In the accumulation phase, the gas flowing through the port is compressed into the pressurized volume by the compression pump. This causes the change in gas pressure, i.e., the increase in gas pressure, to be multiplied by a factor that is due to the ratio of the pressurized volume to the volume of the test specimen or the volume of the test chamber. In particular, when the pressurized volume is made smaller than the volume of the test specimen or the volume of the test chamber connected to the port, the increase in pressure is greater than in the conventional method of measuring the increase in pressure within the volume of the test specimen.

[0009] Instead of measuring the time evolution of the total pressure in the pressurized volume, the time evolution of the partial pressure characteristic of the leaking gas may be measured. For example, if the test body is pressurized with a particular test gas for leak detection, the proportion of this test gas in the gas mixture under investigation can be detected in terms of its partial pressure. If possible, the test gas should be different from the gas components, especially water vapor, that are emitted from or through the inner walls of the test chamber and the test body.

[0010] Very preferably, the temperature of the pressurized volume is stabilized, for example by a heating device for heating the pressurized volume and / or a cooling device for cooling the pressurized volume and / or an insulating device for thermally insulating the pressurized volume from its environment, preferably where only the pressurized volume is thermally stabilized.

[0011] Preferably, the pressurized volume is greater than the volume of the gas conduit piping, meaning that a section of the gas conduit or a cross section of the piping that is the same length as the pressurized volume is smaller than the pressurized volume, i.e., the pressurized volume is greater than the internal volume of a section of the gas conduit that is the same length, and preferably, the pressurized volume is smaller than the volume of the specimen inside the test chamber.

[0012] The compression pump may be a vacuum pump, but is not necessarily a turbomolecular pump. For example, the compression pump may be a diaphragm pump, a roots pump or a turbomolecular pump.

[0013] Advantageously, the test gas component is selectively measured, for example by applying an absorber, getter, etc. in the region along the gas conduit between the port and the pressurized volume to separate the test gas component to be detected from other gas components that may be present. Preferably, at least one gas component other than the test gas component is prevented from entering the pressurized volume, if possible. Alternatively, the gas component may be selectively bound / adsorbed in the pressurized volume.

[0014] Of critical importance to the present invention is that a gas pressure sensor is connected to the pressurized volume to measure the pressure within the pressurized volume, which determines the change in pressure within the pressurized volume over time, which is then evaluated to determine a leak.

[0015] The gas pressure sensor may be a pressure gauge that measures the total pressure rise inside the test chamber or inside the test specimen according to the pressure rise method. Alternatively or additionally, the gas pressure sensor may be designed as a gas-selective partial pressure sensor that measures the partial pressure rise of a test gas, the partial pressure being defined as the relative proportion of the test gas in the gas mixture under investigation. The measurement of the partial pressure rise may be performed according to the accumulation method, where the vacuum pump is stopped and the partial pressure rise of the gas that accumulates in the measurement range is measured.

[0016] Specifically, the gas pressure sensor may be a mass spectrometer, a membrane window sensor, an absorption spectroscopy sensor such as an infrared absorption sensor, an optical emission spectroscopy sensor such as an OES sensor, a semiconductor gas sensor, a chemical gas sensor, or an optical gas detector. In particular, the gas pressure sensor is not necessarily a pressure gauge. In the case of a total pressure rise type, the gas pressure sensor measures the rise in the total pressure of a mixed gas containing the test gas. In the case of a partial pressure rise type, the gas pressure sensor measures the rise in at least the partial pressure ratio of the test gas.

[0017] In an exemplary embodiment of the gas pressure sensor, optical spectrum analysis can be performed to very quickly evaluate the total and / or partial pressure according to the pressure rise or accumulation principle.

[0018] Two exemplary embodiments of the present invention will now be described in detail with reference to the drawings. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of a first exemplary embodiment. [Diagram 2] FIG. 4 is a schematic diagram of a second exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] In FIG. 1, an object 11 is depicted. The object 11 may be a test specimen connected to a port 20 and surrounded by a test gas, such as air. The port 20 opens into a gas conduit 22. The gas conduit 22 comprises, in a downstream direction from the port 20, a compression pump 32, a pressurized volume 34, a valve 27 and a vacuum pump 16. First, the valve 27 is opened and the test specimen is evacuated by the vacuum pump 16. During evacuation, the compression pump 32 may already be used as an auxiliary. As soon as the pressure in the test specimen falls below a threshold value, the valve 27 is closed. The compression pump 32 compresses the gas coming from the test specimen into the pressurized volume 34. In the process, the test specimen may be at a negative pressure with respect to the environment outside the test specimen, so that gas from the environment outside the test specimen can enter the inside of the test specimen through a leak in the test specimen and be discharged and compressed from the test specimen through the port 20 into the pressurized volume 34 by the compression pump 32. At this time, the valve 27 is closed.

[0021] Alternatively, the object 11 may be in the form of a conventional vacuum chamber containing a test specimen pressurized with a test gas, in which case the internal pressure of the test specimen is made higher than the internal pressure in the test chamber 11, and the test gas passes from the test specimen through a leak into the test chamber 11, from where it is compressed by the compression pump 32 through port 20 into the pressurized volume 34, with the valve 27 closed.

[0022] A second valve 29, which is provided in the exemplary embodiment shown in Figure 2 but is not depicted in Figure 1, may be provided in the gas conducting passage 22 between the compression pump 32 and the port 20 or between the pressurized volume 34 and the compression pump 32. The valve 29 allows the compression pump 32 to be isolated from the port 20 when changing specimens or test chambers. The valves 25, 27, 29 may be used to close the pressurized volume.

[0023] The gas pressure sensor 24 is connected to the pressurized volume and measures the pressure of the gas inside the pressurized volume. The gas pressure sensor 24 can be a total pressure sensor or a sensor that measures the partial pressure rise of the test gas inside the pressurized volume 34 according to the accumulation principle by integration. The gas pressure sensor 24 can be an optical sensor.

[0024] The gas pressure sensor 24 may be a total pressure sensor and / or a gas-selective partial pressure sensor 24, such as in the form of a solid-state optical emission spectroscopy sensor (OES). The valve 27 may be a single valve or a multi-part isolator with additional valves, such as isolator 26 in FIG. 2, or may be designed as an isolator to isolate the pressurized volume 34 from the vacuum system.

[0025] A temperature stabilization device 36 surrounds the pressurized volume 34 in the form of an insulating housing that provides cooling and heating to the pressurized volume 34 .

[0026] The pressurized volume 34 consists of a housing having an inlet and an outlet each connected to a portion of the gas conduit 22. The cross section of the housing of the pressurized volume 34 can be larger than the piping of the gas conduit 22 such that the pressurized volume 34 is larger than the portion of the piping of the gas conduit 22 of the same length. Furthermore, the pressurized volume 34 is smaller than the port 20 portion of the specimen or test chamber 11.

[0027] The same applies to the exemplary embodiment of FIG. 2. Here, in addition to a gas pressure sensor 24, which performs an integral measurement according to the accumulation principle, a mass spectrometric gas detector 12 is provided, which is evacuated by a turbomolecular pump 18 and a vacuum pump 16 designed as a forepump. The turbomolecular pump 18 and the vacuum pump 16 form a vacuum pumping system 14. The outlet of the vacuum pump 16 is open to the outside air. At its end opposite the port 20, the gas conducting channel 22 opens into a gas line 30 connecting the vacuum pump 16 and the turbomolecular pump 18. A further gas conducting channel 28 connects the intermediate port of the turbomolecular pump 18 to the part of the gas conducting channel 22, which is located between the pressurized volume 34 and the valve 27. The gas conducting channel 28 comprises a further controllable valve 25. The controllable valve 27 and the controllable valve 25 form a shut-off device 26, by means of which the pressurized volume 34 can be shut off from the vacuum pumping system 14.

[0028] The basic principle of the present invention is that the compression pump 32 located between the test specimen or test chamber 11 and the pressurized volume 34 compresses the gas from the test specimen or test chamber not inside the test chamber or the test body but inside a separate pressurized volume 34, and measures the gas pressure by leak detection using the integral method according to the accumulation principle. This causes the increase in gas pressure to increase by a factor of the volume ratio between the pressurized volume and the volume inside the test specimen or the test chamber. The smaller the volume of the pressurized volume and the higher the gas compression efficiency or compression strength by the compression pump 32, the stronger the pressure increase will be in the pressurized volume.

[0029] In this case, it is also possible to measure the time change in partial pressure of the test gas instead of the time change in total pressure in the pressurized volume 34, so that it is possible to distinguish between gas components, particularly water vapor, that are released from or within the walls of the test chamber or test specimen. This allows the gas to accumulate in a significantly shorter time than when it is accumulated inside the test chamber or test specimen, making it possible to perform leak detection quickly and accurately by the leak detection method according to the present invention, and also suppressing the effects of released gas components.

Claims

1. A leak detection device for detecting a gas leak in a test specimen, a port (20) for the test specimen or a test chamber containing the test specimen; a gas conducting passage (22) connected to the port (20); the gas conduit (22) is provided with a valve (27) for selectively closing the gas conduit (22); the gas conduit (22) is provided with a compression pump (32) such that an inlet of the compression pump (32) is connected to the port (20) via the gas conduit (22) and an outlet of the compression pump (32) is connected to the valve (27) via the gas conduit (22); the gas conduit (22) is connected to a pressurized volume (34) located between the outlet of the compression pump (32) and the valve (27) such that, when the valve (27) is closed, the compression pump (32) compresses gas from the port (20) into the pressurized volume (34); The leak detection device, wherein the pressurized volume (34) is connected to a gas pressure sensor (24) that measures the pressure inside the pressurized volume (34).

2. 2. The leak detection device according to claim 1, wherein the gas pressure sensor (24) is configured to measure the total pressure change by an integral method according to a pressure rise method or a pressure fall method and / or to measure the partial pressure change of at least one test gas according to a partial pressure rise method or a partial pressure fall method.

3. 2. The leak detection device according to claim 1, wherein the pressurized volume is smaller than a test chamber volume of a test chamber connected to the port (20) or a test object volume of a test object connected to the port (20).

4. 4. The leak detection device according to claim 3, wherein the pressurized volume is equal to or less than half the volume of the test chamber or the volume of the test specimen.

5. 2. The leak detection device of claim 1, wherein the pressurized volume (34) has a cross section larger in the longitudinal direction of the gas conduit (22) than the gas conduit (22) so that the pressurized volume (34) is larger than the volume of a portion of the gas conduit (22) having the same length as the pressurized volume (34).

6. 2. The leak detection device of claim 1, wherein the pressurized volume (34) is provided with a temperature stabilization device (36) configured to stabilize the temperature within the pressurized volume (34).

7. 7. The leak detection device of claim 6, wherein the temperature stabilization device includes a heating device for heating the pressurized volume, a cooling device for cooling the pressurized volume, and / or an insulating device for insulating the pressurized volume from an environment external to the pressurized volume.

8. 2. The leak detection device of claim 1, wherein the compression pump (32) is a vacuum pump, a diaphragm pump, a roots pump, or a turbomolecular pump.

9. 2. The leak detection device according to claim 1, wherein the gas conducting passage is connected to a vacuum pump (16) on the side of the valve (27) opposite the compression pump (32).

10. 2. The leak detection device of claim 1, wherein the pressurized volume (34) includes an absorber or getter as a filter that allows a test gas to be detected by the gas pressure sensor (24) into the pressurized volume (34) but blocks or binds gases other than the test gas.

11. 2. The leak detection device of claim 1, wherein the compression pump (32) or a further pump different from the compression pump exhibits gas selectivity between the pressurized volume (34) and the port (20) such that a test gas to be detected by the gas pressure sensor (24) is pumped into the pressurized volume (34) and at least one gas different from the test gas is blocked or compressed less efficiently.

12. A method for detecting a gas leak in a test specimen using the leak detection device according to any one of claims 1 to 11, comprising: pumping gas from a test chamber connected to the port (20) or from a test body connected to the port (20) along the gas conduit (22) from the port (20) into the pressurized volume (34) with the compression pump (32) so that the pressure of the gas in the pressurized volume (34) is higher than that in the test body or the test chamber, with the valve (27) closed; measuring the pressure of the gas within the pressurized volume (34); determining a measurement of the change in pressure of the gas within the pressurized volume (34) over time; assessing whether the test body has a leak based on the determined change in gas pressure; A method comprising:

13. 13. The method of claim 12, wherein the measured gas pressure is an absolute gas pressure in the form of a total pressure inside the pressurized volume (34) or a partial pressure of a test gas component in a gas mixture contained within the pressurized volume (34), and the determined change in gas pressure is an increase in pressure.

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