Viscous flow leak detection
Patent Information
- Application Number
- JP2024518613
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2021-10-04
- Filing Date
- 2022-09-12
- Publication Date
- 2025-02-20
- Estimated Expiration
- 2042-09-12
AI Technical Summary
Existing vacuum leak detection systems are inefficient and costly, requiring high-vacuum pumps and being sensitive to leak position within the test chamber, leading to delayed gas detection and high operational costs.
A test chamber with multiple uniformly distributed vacuum connections connected to a common pump space, using simpler and less expensive pumps like diaphragm or rotary vane pumps, reduces gas travel distance and accelerates gas flow to detectors, independent of leak position.
Facilitates rapid, reproducible, and cost-effective vacuum leak detection by minimizing gas travel time to detectors and reducing dependence on leak position, using simpler and cheaper pumps.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a method and apparatus for leak detection of an analyte, including a test gas. [Background technology]
[0002] It is known to test the hermeticity of a test object, such as a hollow body containing a test gas, such as a food package or a heat exchanger, by placing the test object in a test chamber and evacuating the test chamber space with a vacuum pump. When the pressure in the test chamber outside the test object becomes lower than the pressure inside the test object, any leaks in the test object will cause the test gas to leak out and be evacuated by the vacuum pump. The gas flow evacuated by the vacuum pump is analyzed by a gas detector that detects the test gas.
[0003] In classical helium leak detection, the test chamber is filled with helium and set to atmospheric pressure or higher. Typically, the test chamber is first pre-evacuated with a forepump, and then the test chamber is evacuated to a pressure of a few millibars or less with a turbomolecular pump when the leak is measured. If the test gas leaks from the leak in the test chamber, the concentration of the test gas in the gas exhausted outside the test chamber is detected by a detector. This test gas concentration or test gas partial pressure is a measure of the amount of leakage from the test chamber. When the operating pressure in the test chamber is less than 1 mbar, the gas diffusion speed is sufficiently high that the test gas leaking from the test chamber reaches the sensor system of the gas detector without significant delay. Summary of the Invention [Problem to be solved by the invention]
[0004] The present invention is based on the objective of providing a more cost-effective vacuum leak detection system and a more cost-effective vacuum leak detection method that can detect a test gas quickly and with high reproducibility by moving the gas quickly and uniformly. [Means for solving the problem]
[0005] In the present invention, a test chamber provided with a number of vacuum connections is connected to a vacuum pump, and a test gas in the exhausted gas stream is detected by a gas detector. A vacuum connection in this case is understood to mean an opening in the wall and / or bottom and / or lid of the test chamber, through which gas can pass from the inside of the test chamber into a target space connected to the vacuum connections.
[0006] At least the vacuum connections, preferably all of them, are connected to and open into a common pump space, which is connected to the vacuum pump via a pump line. The gas detector may be connected to the pump line. The vacuum connections are formed in at least one wall and / or bottom and / or lid of the chamber bounding the chamber and are distributed as evenly as possible. The vacuum connections are designed such that, in operation, when the chamber is evacuated by the vacuum pump, a lower vacuum pressure is formed in the pump space than in the chamber. The flow rate of the evacuated gas is higher in the common pump space than in the chamber. This means that the gas leaking from the analyte contained in the chamber through the leak of the analyte moves slower in the chamber than it moves after passing through any of the vacuum connections from the chamber. As the test gas passes from the test chamber through the vacuum connection, the tracer gas accelerates and is delivered to the detector at an increased speed. Because there are multiple vacuum connections, the distance between the analyte leak and the nearest vacuum connection is shorter than in the conventional system with only one vacuum connection. This means that the test gas has to travel a shorter distance within the test chamber before passing from the test chamber through the vacuum connection. This also shortens the travel time of the test gas from the leak to the gas detector.
[0007] Furthermore, the time it takes for the leaking gas to reach the detector from the leak is less dependent on the location of the analyte leak in the test chamber, i.e., less dependent on the location of the analyte itself in the chamber, and the signal strength measured by the test system at any given time in the event of a leak in the analyte is less dependent on the location of the analyte in the test chamber.
[0008] Unlike conventional classical vacuum leak detection methods, the vacuum leak detection method according to the present invention does not require high vacuum pumps or turbomolecular vacuum pumps, but can instead be operated with technically simpler and less expensive vacuum pumps such as diaphragm pumps, scroll pumps, rotary vane pumps, etc. As a result, the vacuum leak detection according to the present invention is technically simpler and more cost-effective.
[0009] The vacuum connections may be arranged evenly, e.g. uniformly distributed, over at least one wall and / or bottom and / or lid defining the space within the test chamber. Preferably, a plurality of vacuum connections are provided on each of a plurality of walls and / or the bottom and / or the lid. The vacuum connections may be arranged, e.g., in a grid pattern. The space of the test chamber may be defined, for example, by a double bottom, double wall, etc., forming the pump space in at least one test chamber wall and / or test chamber bottom and / or test chamber lid.
[0010] The vacuum connections may be connected to the pump volume by lines of approximately the same length, meaning that the difference in length between the vacuum lines is less than 10% of the total length of any one vacuum line.
[0011] According to the invention, a technically relatively simple and relatively inexpensive vacuum pumping system allows for a fast and uniform movement of the pumped gas, enabling a rapid vacuum leak detection. This is achieved by the pump volume connected to the vacuum connection, which makes the difference between the pressure at any point in the test chamber and the pressure at any point in the pump volume greater than the difference between the pressures at two separate points in the test chamber. That is, the gas pressure gradient over the distance from any point in the test chamber to any point in the pump volume is greater, preferably significantly greater, than the pressure gradient between any points in the test chamber.
[0012] In the present invention, the pressure distribution in the test chamber is as uniform as possible, i.e. the pressure difference between different points in the test chamber in the area outside the subject is less than 1%, while the gas pressure at any point in the pump space is significantly lower than the pressure at any point in the test chamber. Preferably, the pressure at any point in the pump space is more than 10% lower than the pressure at any point in the test chamber. The pressure in the test chamber is preferably less than 80 mbar, more preferably less than 40 mbar, and very preferably less than 20 mbar, while the pressure in the pump space is preferably less than 72 mbar, more preferably less than 36 mbar, and very preferably less than 18 mbar. [Brief description of the drawings]
[0013] [Figure 1] FIG. 1 is a schematic diagram of a first embodiment. [Diagram 2] FIG. 4 is a schematic diagram of a second embodiment. [Diagram 3] FIG. 13 is a schematic diagram of a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0015] In each embodiment, the test chamber 12 is connected to a vacuum pump 18 via a pump line 14. A gas detector 16 is connected to the pump line 14. The vacuum pump 18 can be a diaphragm pump, a scroll pump, or a rotary vane pump. Typically, the test chamber is formed of a lid 22, a bottom 24, and a number of walls 20. Although the test chamber 12 is shown in an open state in Figs. 1 and 2, the lid 22 can be hermetically closed in the direction of the arrows shown in the drawings.
[0016] The lid 22 of each embodiment shown in Figures 1 and 2 is provided with a number of vacuum connections 26. The vacuum connections 26 are arranged in a grid and are uniformly distributed over the entire inside of the lid 22. The vacuum connections 26 are formed as holes and are depicted as dots in the figures. In Figures 1 and 2, the vacuum connections 26 open into a shared pump space 28. The pump space 28 is formed as a cavity in the lid 22 and is connected to the vacuum pump 18 via the pump line 14.
[0017] The embodiment shown in Figure 3 differs from the embodiments shown in Figures 1 and 2 in that a number of vacuum connections 26 are provided on both the lid 22 and the bottom 24 of the chamber to be examined, as well as on all walls 20. Here again, the vacuum connections 26 are simply drawn as dots. The vacuum connections 26 are each connected by a separate vacuum line 30 to a pump space 28 which opens into the pump line 14. In the simplest case, the pump space 28 may be part of the pump line 14.
[0018] After a specimen (not shown) is placed in the chamber 12 and the chamber 12 is closed, the pressure in the chamber 12 is reduced by the vacuum pump 18 to less than 80 mbar, preferably less than 40 mbar, and most preferably less than 20 mbar. The pressure in the chamber is preferably less than 72 mbar, more preferably less than 36 mbar, and most preferably less than 18 mbar.
[0019] If there is a leak in the test specimen, the test gas leaks from inside the test specimen through the leak into the test chamber 12, and is sucked into the pump space 28 through at least one vacuum connection 26. Since there are multiple vacuum connections 26, the distance that the test gas must travel in the test chamber from the nearest vacuum connection 26 to the pump space 28 is relatively short. Since there are multiple vacuum connections 26 in the present invention, the relative distance from any point in the test chamber to the nearest vacuum connection 26 is shorter than the conventional principle in which there is only one vacuum connection. As a result, the difference in the elapsed time from the leaking gas leaking out to the gas reaching the detector due to the difference in the location of the leak in the test chamber is smaller than when there is only one vacuum connection. In other words, such a time difference due to the difference in the location of the leak in the test chamber is smaller than when there is only one vacuum connection.
[0020] As the test gas flows through the vacuum connection 26, it accelerates due to the lower pressure and gas concentration in the pump space 28. The diffusion rate and flow rate of the exhausted gas is greater in the pump space 28 and pump line 14 than in the test chamber 12.
[0021] The gas pressure gradient formed during operation along a path between any separate points within the test chamber 12 will be smaller than the gas pressure gradient formed along a path from any point within the test chamber 12 to any point within the pump space 28.
Claims
1. An apparatus for leak detection, comprising: A vacuum pump (18); an examination chamber (12) configured to accommodate an examination subject and configured to be evacuated by the vacuum pump (18); a gas detector (16) for detecting gas exhausted from the test chamber (12) by the vacuum pump (18); the chamber (12) is provided with a plurality of vacuum connections (26) for evacuating the chamber (12), the vacuum connections being connected to the vacuum pump (18), a shared pump space (28) connected to said vacuum connection (26) is provided between said vacuum connection (26) and said vacuum pump (18) along the flow direction, said pump space being evacuated by said vacuum pump (18).
2. 2. The device according to claim 1, wherein the vacuum connection (26) opens into the pump space (28).
3. 2. The device according to claim 1, wherein the pump space (28) is formed in a wall, a bottom (24) or a lid (22) of the test chamber (12).
4. 2. The apparatus of claim 1, wherein said plurality of vacuum connections (26) are each connected to said pump space (28) by separate vacuum lines, the vacuum lines being approximately the same length.
5. 2. The apparatus of claim 1, wherein the pump space (28) is connected to the vacuum pump (18) via a shared pump line (14).
6. 2. The device according to claim 1, wherein the vacuum connections (26) are formed as holes and are distributed over at least one housing wall (20) of the test chamber (12) that defines the space of the test chamber.
7. 2. The device according to claim 1, wherein the vacuum connections (26) are distributed in a grid over at least one wall and / or lid (22) and / or bottom (24) of the chamber (12) to be examined.
8. 2. The apparatus of claim 1, wherein the vacuum connections (26) are uniformly distributed.
9. A method for detecting a vacuum leak using a vacuum leak detection device, comprising: The vacuum leak detection device includes a vacuum pump (18), a gas detector (16) and a test chamber (12); The vacuum pump (18) evacuates the test chamber (12); The gas detector (16) detects a test gas in the gas exhausted from the test chamber (12) by the vacuum pump (18); the test chamber (12) having a plurality of vacuum connections (26) connected to a common pump space (28); The pump space (28) is formed between the test chamber (12) and the vacuum pump (18) along a flow direction, and the method includes: placing a specimen in the specimen chamber (12); evacuating the pump space (28) and the test chamber (12) such that a gas pressure gradient extending from the test chamber (12) into the pump space (28) is greater than any gas pressure gradient within the test chamber (12) across the test chamber (12); A method comprising:
10. 10. The method of claim 9, wherein the flow rate of gas evacuated from the test chamber (12) is higher in the pump volume (28) than in the test chamber (12).
11. 10. The method of claim 9, wherein a difference in gas pressure between two separate locations in the test chamber (12) during vacuum leak detection is negligibly small.
12. 10. The method according to claim 9, wherein the vacuum pressure generated at the inlet of the vacuum pump (18) and / or in the pump space (28) is less than 72 mbar.
13. 10. The method according to claim 9, wherein the vacuum pressure created in the test chamber (12) is higher than the vacuum pressure created in the pump space (28) and is less than 80 mbar.