Method for measuring ambient concentration of light gas using mass spectrometry type counterflow leak detector
Patent Information
- Application Number
- JP2024573578
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-06-22
- Filing Date
- 2023-05-25
- Publication Date
- 2025-12-15
AI Technical Summary
Existing mass spectrometry type counterflow leak detectors face challenges in determining the concentration of light gas components, such as helium, outside the detector without interrupting the leak detection process or turning off the roughing pump.
The method involves using a gas ballast valve in the roughing pump to allow outside air to enter, enabling light gas components to flow backward through the pump and into the mass spectrometer for analysis, without stopping the roughing pump or high vacuum pump.
This approach allows for continuous leak detection and simultaneous analysis of outside air for light gas concentrations, eliminating the need for pump restarts and reducing measurement time.
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for detecting a light gas component outside a mass spectrometry type counterflow (countercurrent) leak detector.
Background Art
[0002] Typically, a mass spectrometry type counterflow leak detection device includes a port to a test object to be investigated or a port to a test chamber in which the test object to be investigated is disposed inside, a gas detector in the form of a mass spectrometer connected to the port, and a high-vacuum pump, usually in the form of a turbomolecular pump, having an inlet connected to the mass spectrometer and an outlet connected to the inlet of a roughing pump. The outlet of the roughing pump sends the evacuated gas into the surrounding outside air. Further, the high-vacuum pump typically has an intermediate gas inlet connected to the test object port or the test chamber port described above. Furthermore, the roughing pump may be directly connected to the mass spectrometer by a bypass line that bypasses the high-vacuum pump for detecting a large leak. The test object port or the test chamber port may be connected to the inlet of the roughing pump via an additional booster pump. This booster pump may be connected to the intermediate gas inlet of the high-vacuum pump.
[0003] For leak detection, the test chamber port and the test chamber connected to the test chamber port are first evacuated by the roughing pump, and further by the booster pump if there is a booster pump. Then, the roughing pump creates the necessary rough vacuum at the outlet of the high-vacuum pump. Thus, the high-vacuum pump evacuates the mass spectrometer. As soon as the inlet of the high-vacuum pump reaches the vacuum necessary to operate the mass spectrometer, a connection valve at the connection between the test chamber port and the high-vacuum pump is opened, and gas flows from the test chamber into the high-vacuum pump and counterflows through the high-vacuum pump to the vacuum analyzer for analysis. If there is a leak in the test object, gas enters the test chamber from inside the test object, counterflows from there into the mass spectrometer, and can be detected there.
[0004] For mass spectrometry type counterflow leak detection, it is often important to grasp the concentration of some light gas components in the outside air. The light gas (lightweight gas) component refers to a gas component in the mixed gas derived from the outside air that is lighter than air. One such light gas component can be, for example, helium.
[0005] Conventionally, the ambient concentration (external concentration, outside air concentration) of helium is determined using a separate gas analyzer. Additionally, in a mass spectrometry type counterflow leak detector, it is possible to take in helium by turning off the roughing pump and opening the gas ballast valve of the roughing pump, but this reduces the speed. When the roughing pump is stopped, gas can enter the mass spectrometer through a bypass line for detecting large leaks and a gas ballast valve across the high vacuum pump, and measurements can be performed there. This bypass line is a direct connection line between the inlet of the roughing pump and the mass spectrometer. Typically, an additional throttle for detecting large leaks is provided in such a bypass line. Summary of the Invention Problems to be Solved by the Invention
[0006] An object of the present invention is to provide an improvement in a method for determining the concentration of a light gas component outside a mass spectrometry type counterflow leak detector. Means for Solving the Problems
[0007] The method according to the present invention is defined by the configuration of claim 1.
[0008] Claim 1 relates to a mass spectrometry counterflow leak detection device comprising a roughing pump, a high vacuum pump, and a mass spectrometry type gas detector. The outlet of the roughing pump can be open to the outside air or can be connected, for example, to an exhaust line that discharges the exhausted gas to the outside air. The inlet of the roughing pump is connected to the outlet of the high vacuum pump. The inlet of the high vacuum pump is connected to the mass spectrometer. The intermediate gas inlet of the high vacuum pump is connected to the outlet via a separate connection line to the test vacuum chamber and / or the test object. In addition to this, a port for the test chamber or the test object may be connected to the inlet of the roughing pump via an additional booster pump. However, the booster pump is not necessarily essential. A configuration in which the intermediate gas outlet of the booster pump is connected to the intermediate gas inlet of the high vacuum pump is also conceivable.
[0009] The high vacuum pump is typically a turbomolecular pump. The roughing pump is provided with a gas ballast that is open to the external outside air or that opens into a fresh air line. The gas ballast may comprise a valve that can be selectively switched, that is, it may be selectively opened and closed.
[0010] For mass spectrometry counterflow leak detection, the roughing pump is conventionally used to generate a roughing pressure at the outlet of the high vacuum pump. This enables the high vacuum pump to generate the necessary high vacuum inside the mass spectrometer. Gas from the test chamber or the test object flows back through the high vacuum pump via the intermediate gas inlet of the high vacuum pump and is taken into the mass spectrometer where it is analyzed. By doing so, it is determined whether the gas to be analyzed contains gas components that indicate a leak in the test object.
[0011] At the same time, in order to detect or analyze lightweight gas components lighter than air from outside the roughing pump, the valve of the gas ballast can be opened, or air from outside the roughing pump can be taken into the roughing pump through the opened gas ballast. As a result, at least one lightweight gas component such as helium flows backward from the roughing pump through the inlet of the roughing pump and out to the mass spectrometer, while the remaining gas components are sent out to the outside through the outlet of the roughing pump. Alternatively or in addition to this, an air inlet may be directly opened in the roughing region of the roughing pump, that is, for example, in the connection line between the roughing pump and the high-vacuum pump and / or in a bypass line described later that bypasses the high-vacuum pump.
[0012] That is, the present invention has the advantage that during actual leak detection, it is possible to analyze the outside air with a mass spectrometer, particularly to measure the concentration of lightweight gas components in the outside air, without interrupting the leak detection and / or without turning off the roughing pump. In this regard, the lightweight gas components to be measured can flow backward and enter from the inlet of the roughing pump through the high-vacuum pump to the inlet of the high-vacuum pump and then to the mass spectrometer. Alternatively or in addition to this, the lightweight gas components to be measured can enter the mass spectrometer through a bypass line for detecting a large leak that connects the inlet of the roughing pump to the mass spectrometer across the high-vacuum pump. An additional throttle can be provided in the bypass line. The presence of such a bypass line makes it possible to detect extremely large leaks before the necessary high-vacuum pressure is generated in the mass spectrometer by the high-vacuum pump.
[0013] Therefore, the light gas component flows in a direction opposite to the exhaust direction from the gas ballast, through the roughing pump, and to the mass spectrometry type gas detector. The pressure at the outlet of the high vacuum pump does not depend on the ratio of the light gas component (e.g., helium, etc.) to be measured in the outside air, but only depends on the speed of the roughing pump. The measurement deviation in the leak rate signal and the pre-ion current signal of the mass spectrometer depends on the ambient concentration of helium or the concentration of the light gas component in the outside air.
[0014] Light gases such as helium flow in the direction of the mass spectrometer against the actual exhaust direction. The lower the speed of the roughing pump, the more helium flows back in a reverse flow from the inlet of the roughing pump through the roughing pump to the mass spectrometer. The increase in the light gas component is larger than the total pressure increase of the mass spectrometer due to the difference in compression. Therefore, by changing or adjusting the speed of the roughing pump, the ambient concentration of light gases such as helium can be obtained without operating the valve.
[0015] The ambient concentration of the light gas component can be obtained without the need to turn off the pump during actual leak detection or after leak detection of the test object. Since the roughing pump and the high vacuum pump continue to be driven, the time required to stop and restart these vacuum pumps is eliminated.
[0016] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.
Brief Description of the Drawings
[0017]
Figure 1
Figure 2
Modes for Carrying Out the Invention
[0018] A mass spectrometry type counterflow leak detection device 10 equipped with a gas detector 12 in the form of a mass spectrometer is illustrated. The gas detector 12 is gas-tightly connected to an inlet portion 14 of a high-vacuum pump 16 in the form of a turbomolecular pump. An outlet portion 18 of the high-vacuum pump 16 is gas-tightly connected to an inlet portion 22 of a roughing pump 24 by a connection line provided with a selectively controllable valve 20. An outlet portion 26 of the roughing pump 24 is open to the outside air or opens into an exhaust line.
[0019] The inlet portion 22 of the roughing pump 24 is also connected to the mass spectrometer 12 by an individual bypass line 28. The bypass line 28 straddles the high-vacuum pump 16 and the controllable valve 20 and is provided with a throttle 30. This enables detection of large leaks.
[0020] The leak detection device 10 is further provided with a port 32 for a test chamber or a test object. In the illustrated exemplary embodiment, a test chamber 35 is vacuum-connected to the port 32. After the test chamber 35 contains a test object to be investigated for leaks, it is evacuated. For this purpose, the port 32 is gas-tightly connected to a booster pump 34. In this regard, an inlet portion 36 of the booster pump is gas-tightly connected to the port 32, and an outlet portion 38 of the booster pump is connected to the inlet portion 22 of the roughing pump by a gas line 42 provided with a further valve 40.
[0021] The booster pump 34 is not essential for the present invention. FIG. 2 shows an exemplary embodiment without a booster pump. The exemplary embodiment of FIG. 2 is consistent with the exemplary embodiment of FIG. 1 except that there is no booster pump 34 and an air inlet portion 53.
[0022] An intermediate gas line 46 equipped with a further selectively operable valve 44 connects an intermediate gas outlet portion 48 of the booster pump 34 and an intermediate gas inlet portion 50 of the high-vacuum pump 16.
[0023] The rough vacuum pump 24 is also provided with a gas ballast valve 52 formed separately from the inlet portion 22 and the outlet portion 26. The gas ballast valve 52 connects the inside of the rough vacuum pump 24 to the outside 54 of the rough vacuum pump 24 and the leak detection device 10. The gas ballast valve 52 can be selectively operated and opened and closed.
[0024] A throttle point 51 for determining the gas flow rate taken into the rough vacuum pump 24 through the gas ballast is provided between the gas ballast valve 52 and the rough vacuum pump 24. In the present invention, the gas ballast valve 52 may be omitted. In this case, only the throttle point 51 is provided at the inlet portion forming the gas ballast of the rough vacuum pump 24. The throttle point 51 can be realized, for example, by appropriately selecting the cross-section of the inlet portion of the gas ballast.
[0025] Instead of or in addition to the inlet portion of air from the outside 54 through the gas ballast of the rough vacuum pump 24, it is also possible to take in outside air into the rough vacuum region of the rough vacuum pump 24 through the air inlet portion 53 shown in FIG. 2. In FIG. 2, as an exemplary embodiment, an air inlet portion 53 is provided. The air inlet portion 53 can be opened to the outside air or connected to a fresh air line, and opens into the connection line between the inlet portion 22 and the valve 20, that is, the connection line connecting the rough vacuum pump 24 and the high vacuum pump 16. In FIG. 2, the air inlet portion 53 is depicted in addition to the inlet portion through the gas ballast of the rough vacuum pump 24. As a variant, the air inlet portion 53 may be provided without a gas ballast. In this case, the gas ballast of the rough vacuum pump 24 is omitted. A throttle similar to the throttle point 51 of the gas ballast is also provided in the air inlet portion 53. A similar configuration is also possible in the exemplary embodiment of FIG. 1.
[0026] During operation, the test chamber 35 is evacuated by the roughing pump 24 and the booster pump 34. The roughing pump 24 generates the necessary rough vacuum at the outlet of the high vacuum pump 16. There, the high vacuum pump 16 evacuates the contents of the mass spectrometer 12. At the same time, the roughing pump 24 also directly evacuates the mass spectrometer 12 via the bypass line 28.
[0027] As soon as the vacuum pressure required for the operation of the mass spectrometer 12 is reached, the valve 44 is opened and the valve 40 is closed, so that the test gas and / or leakage gas from the inside of the test chamber 35 can flow back through the booster pump 34, the intermediate gas line 46, and further through the high vacuum pump 16 into the mass spectrometer 12 and be analyzed there.
[0028] In order to quickly and easily determine the gas concentration of helium in the air of the outside 54, the gas ballast valve 52 is opened while the roughing pump 24 is still operating. In an exemplary embodiment without a gas ballast valve, the gas ballast 52 can be permanently open and connected to a fresh air line. In the simplest case, the gas ballast 52 can be open to the outside air.
[0029] To determine the gas concentration of helium in the outside air, the speed of the vacuum pump is adjusted or at least changed between two different operating states, for example, reciprocated between the final speed and the deceleration speed of the roughing pump 24. Due to the change in the pump speed, the partial pressure of helium and the total pressure at the inlet 22 of the roughing pump 24 change. And since helium flows back from the roughing pump 24 into the mass spectrometer 12 via the bypass 28 or through the high vacuum pump 16, it becomes possible to measure a change or signal deviation corresponding to the helium component in the measurement signal of the mass spectrometer 12. For the air flowing from the outside 54 into the roughing pump 24, in the case of the gas ballast valve 52, its supply can be affected by opening and closing the gas ballast valve 52.
[0030] Among the outside air, the gas components lighter than the average value of the gas components of the outside air flow backward from the inlet portion 22 to the outside of the roughing pump, and from there flow backward to the high vacuum of the mass spectrometer 12 through the high vacuum pump 16 and / or through the bypass line 28, where they can be measured. On the other hand, among the outside air, the gas components heavier than the outside air are sent back from the outlet portion 26 of the roughing pump 24 to the outside 54. In this way, helium from the outside air 54 enters the mass spectrometer 12, and analysis can be performed there without the need to stop the roughing pump 24 and / or the high vacuum pump 16 and / or the booster pump 34.
[0031] Instead of or in addition to the gas ballast of the roughing pump 24, an air inlet for directly supplying outside air to the roughing region of the roughing pump 24 may be provided, for example, as an air inlet 53 to the connection line between the roughing pump 24 and the high vacuum pump 16 and / or between the inlet portion 22 and the valve 20 and / or to the bypass line 28.
Claims
1. 1. A method for determining ambient concentrations of light gases by a mass spectrometric counterflow leak detection system (10) comprising a mass spectrometric gas detector (12), a high vacuum pump (16) connected to the gas detector (12), and a pre-vacuum pump (24) connected to the high vacuum pump (16), wherein the pre-vacuum pump (24) has a gas outlet port open to the atmosphere, and the pre-vacuum pump (24) is used to evacuate the high vacuum pump (16) and / or the gas detector (12), 1. A method for detecting a gas mixture containing air from outside the pre-vacuum pump (24) in operation, wherein air from outside the pre-vacuum pump (24) is introduced into the pre-vacuum region on the inlet side of the pre-vacuum pump (24) while the pre-vacuum pump (24) is running, and gas components lighter than air in the introduced air / gas mixture flow back into the gas detector (12) and are detected therein, while the remaining gas components of the introduced gas mixture are sent out through the outlet of the pre-vacuum pump (24) to the surrounding atmosphere (54).
2. 2. The method of claim 1, wherein the lighter-than-air gas component is neon, helium, hydrogen, or deuterium.
3. 3. The method of claim 1 or 2, wherein the light gas components flow back into the gas detector (12) through the high vacuum pump (16) or through a bulk leak detection bypass line (28) that crosses the high vacuum pump (16) and connects the pre-vacuum pump (24) to the gas detector (12).
4. 2. The method of claim 1, wherein the pre-vacuum pump (24) has an open gas ballast that introduces air from outside (54) of the pre-vacuum pump (24) into the pre-vacuum pump (24) while it is running.
5. 2. The method of claim 1, wherein the pre-vacuum region upstream of the inlet of the pre-vacuum pump is provided with a separate air inlet for drawing air from outside the pre-vacuum pump into the pre-vacuum region of the pre-vacuum pump.
6. 2. The method of claim 1, wherein the speed of the pre-vacuum pump is varied to determine the ambient concentration of the light gas components of the intake air / gas mixture, and the ratio of the light gas components is determined from the resulting change in the measurement signal of the gas detector (12).
7. 2. The method of claim 1, wherein the speed of the pre-vacuum pump is varied from a first speed value to at least a second speed value different from the first speed value, and a response of a measurement signal representative of the partial pressure of the gas component is evaluated.
8. 2. The method of claim 1, wherein the pre-vacuum pump (24) is a Roots pump and / or a claw pump.
9. 2. The method of claim 1, wherein during the analysis of the gas in the test chamber, an analysis of the gas composition from outside the pre-vacuum pump (24) is carried out using the gas detector (12).
10. 2. The method of claim 1, wherein the pre-vacuum pump (24) is not stopped during the measurement of the light gas components from outside the pre-vacuum pump (24).