LEAK DETECTION DEVICE

Description

[0001] The invention relates to a leak detection device with a gas analyzer, a vacuum pump, a first gas inlet and a second gas inlet, in particular for sniffer leak detection.

[0002] When detecting gas leaks, gas is sucked in through a gas inlet using a vacuum pump and fed to a gas analyzer for analysis. The aim is to detect any test gas flowing through a leak. A special variant of gas leak detection is sniffer leak detection, in which a constant air stream is sucked in through the gas inlet of a sniffer probe. The sniffer probe is moved over the test object while the sucked-in gas is analyzed. This allows a leak in the test object to be not only detected but also located. If the gas inlet of the sniffer probe is located near a gas leak, the test gas escaping through the leak is absorbed along with the air stream. To ensure that the leak gas is sucked in reliably and as completely as possible, the largest possible sniffer gas flow is used.The sniffer gas flow is the flow rate of the gas stream drawn in through the gas inlet of the sniffer probe. The flow rate of the air stream is typically several times higher than the flow rate of the measured leakage gas, the test gas escaping from a leak.

[0003] The concentration of the leak gas in the gas stream drawn through the gas inlet is determined by the ratio of the leak rate to the sniffer gas flow. As a result, the concentration of the leak gas in the gas stream drawn by the sniffer probe is typically comparatively low. Therefore, the sniffer gas flow cannot be chosen arbitrarily large.

[0004] The atmosphere surrounding the test object often contains gas components that produce measurement signals similar or identical to those of the test gas in the gas detector or gas analyzer. These gas components are therefore referred to as interfering gases or background gases. They cause interference signals that cannot be easily distinguished from the measurement signals of actual leakage gases.

[0005] A known method for suppressing such interference signals involves alternately sampling sample gas from the test area of ​​the test specimen and reference gas from the atmosphere surrounding the specimen. The reference gas serves as a reference for determining the proportion of the interfering gas in the sampled gas mixture (reference measurement).

[0006] Such solutions are described, for example, in EP 1 342 070 B1 and EP 1 819 998 B1. The gas is sucked in by a compact sensor unit in the form of an infrared absorption sensor in the handle of a sniffer probe. In WO 2007 / 031386 A1, a mass spectrometer is used as the gas analyzer. The sucked-in gas must be fed to the analyzer via a sniffer line.

[0007] In other sniffer leak detection methods, several, typically two, separate sniffer probes are connected independently to the same gas analyzer and operated alternately to evaluate the signal from one sniffer probe and the other. In these so-called multiplexer systems, leak detection is performed with a gas detection system with multiple sniffer lines at multiple locations by serially switching from one line to another.

[0008] When switching between two gas inlets of a leak detection device that are connected to the same gas analyzer, a pressure surge occurs in the sniffer line, which influences the measurement signal and leads to signal fluctuations.

[0009] CN 205748829 U describes a mass spectrometric helium gas leak detector.

[0010] DE 19853049 A1 describes a gas leak detection device for detecting a leak in a test object.

[0011] The invention is based on the object of providing an improved leak detection device with two different gas inlets, each connected to the same gas analyzer, and a corresponding leak detection method.

[0012] The leak detection device according to the invention is defined by the features of patent claim 1. Accordingly, two multi-way valves are provided, each having a first inlet and at least one first and one second outlet. The multi-way valves can, for example, be three-two-way valves with one inlet and two outlets. The first outlet of each of the two multi-way valves is connected to a first gas inlet of the leak detection device, while the second outlet of each of the two multi-way valves is connected to a separate vacuum pump. The two multi-way valves simplify the switching and assignment of the two gas inlets to the gas analyzer. While the gas sucked in through the first gas inlet with one multi-way valve is supplied to the gas analyzer, the gas sucked in through the second gas inlet is sucked in by the vacuum pump without being supplied to the gas analyzer.By simply switching the multi-way valves, pressure surges can be avoided or reduced because a gas stream is drawn in through both gas inlets, while one or the other gas stream can be analyzed alternately with the gas analyzer.

[0013] The two gas inlets can be located on different sniffer probes, each connected to the two multi-way valves via separate sniffer lines. The vacuum pump can be a separate auxiliary pump, not connected to the gas analyzer. The gas analyzer can be a mass spectrometric leak detector with a multi-stage high-vacuum pump. The vacuum pump connected to the two second outlets is preferably open to the atmosphere.

[0014] Alternatively, the two gas inlets can be the sample gas inlet and a reference gas inlet of one and the same sniffer probe. The vacuum pump can form a pumping stage, for example, a backing pump stage, of a multi-stage high-vacuum pump of a mass spectrometric gas analyzer. In this case, the first two outlets of the multi-way valves are connected to the mass spectrometer, while the second two outlets of the multi-way valves are connected via a separate connecting line to a connecting branch that connects the vacuum pump to the other pumping stages of the high-vacuum pump and to the mass spectrometer. Throttle valves are provided in both connecting lines to adjust the required and desired gas flow. Alternatively, the connecting line itself can be designed to act as a throttle for the gas flow.The first two outlets can be connected to the second two outlets so that only a branched partial flow is fed to the gas analyzer, while the remaining part of the gas flow is conveyed to the atmosphere via the vacuum pump.

[0015] In the following, two embodiments of the invention are explained in more detail with reference to the figures.

[0016] They show: Fig. 1 shows a first embodiment and Fig. 2 shows a second embodiment.

[0017] In both leak detection devices 10 shown in the figures, a first gas inlet 12 is connected to a mass spectrometric gas analyzer 16 and a vacuum pump 18 via a first multi-way valve 14 in the form of a three-two-way valve, while a second gas inlet 20 is also connected to the gas analyzer 16 and the vacuum pump 18 via a second multi-way valve 22 in the form of a three-two-way valve.

[0018] In the first embodiment according to Fig. 1 the two gas inlets 12, 20 are provided on a common sniffer probe 24 such that the first gas inlet 12 is directed in the direction of a test area to be examined, in which a gas leak on a test object is suspected, while the second gas inlet 20 forms a reference gas inlet with which gas can be sucked in from the atmosphere surrounding the test object.

[0019] The first gas inlet 12 is connected to a first inlet 28 of the first multi-way valve 14 via a first connecting line 26. The second gas inlet 20 is connected to a first inlet 32 ​​of the second multi-way valve 22 via a separate connecting line 30.

[0020] Furthermore, in both embodiments, a first outlet 34 of the first multi-way valve 14 is connected to the first outlet 36 of the second multi-way valve 22 and the gas analyzer 16, while a second outlet 38 of the first multi-way valve 14 is connected to a second outlet 40 of the second multi-way valve 22 and is gas-conductingly connected to the vacuum pump 18.

[0021] In the Fig. 2 In the embodiment shown, the two gas inlets 12, 20 are provided on different sniffer probes, which are connected to the two multi-way valves 14, 22 via separate connecting lines and can be guided and moved independently of each other.

[0022] In the first embodiment according to Fig. 1 The first two outlets 34, 36 open into a common connecting line 42, which is connected at a junction 44 to a connecting line 46 connected to the second gas outlet 38 of the first multi-way valve 14, and to another connecting line 48 connected to the second outlet 40 of the second multi-way valve 22. The common connecting line 42 is connected via the junction 44 to a connecting branch 50, which connects the vacuum pump 18 to a second vacuum pump 52. The second vacuum pump 52 is connected to a turbomolecular pump 54, the inlet of which is in turn connected to the gas analyzer 16 in the form of a mass spectrometer. The vacuum pump 18 thus forms a first pumping stage of a three-stage high vacuum pump of the mass spectrometric leak detector 56, which consists of the vacuum pump 18, the second vacuum pump 52, the turbomolecular pump 54 and the gas analyzer 16 (mass spectrometer).The second vacuum pump 52 thus forms the second pumping stage and the turbomolecular pump 54 forms the third pumping stage of the multi-stage high vacuum pump 60.

[0023] Between the first two gas outlets 34, 36 and the junction point 44, a line 64 throttled by a throttle 62 branches off from the connecting line 42. This line 64 is connected to the gas analyzer 16 and branches off a partial flow from the gas flowing through the line 42 and feeds it to the gas analyzer 16, while the remaining gas flow is fed via the junction point 44 to the vacuum pump 18 and from the vacuum pump 18 to the atmosphere. The connecting line 42 has a second throttle 66 between the junction point 44 and the connecting branch 50, which is used to block the gas flow. Due to the blocked flow, a pressure surge on the downstream side of the throttle, e.g. caused by the pump, does not have a disruptive effect in the form of pressure fluctuations on the upstream side.

[0024] In the second embodiment, however, the connecting line 42 from the two outlets 38, 40 to the vacuum pump 18 and the connecting line 64 from the two outlets 34, 36 to the gas analyzer 16 are separated from each other and are therefore not connected to each other in a gas-conducting manner.

[0025] In both embodiments, the vacuum pump 18 remains switched on during the gas analysis with the gas analyzer 16 and delivers gas from the one of the two gas inlets 12, 20 that is not connected to the gas analyzer 16 via the multi-way valves 14, 22. Thus, in the Fig. 2 In the illustrated embodiment and switching state, the gas from the first gas inlet 12 is fed via the first multi-way valve 14 from its first inlet 28 via its first outlet 34 and the connecting line 64 to the gas analyzer 16 for gas analysis, while at the same time gas flowing in through the second gas inlet 20 is passed via the second multi-way valve 22 from its first inlet 32 ​​to its second outlet 40 and from there via the connecting line 42 via the pump 18 to the atmosphere. Thus, while the gas from the first gas inlet 12 is being analyzed by the gas analyzer 16, the gas from the second gas inlet 20 is pumped by the pump 18 to the atmosphere.

[0026] In the Fig. 1In the exemplary embodiment shown, in which the first gas inlet 12 forms a measuring gas inlet and the second gas inlet 20 forms a reference gas inlet of the same sniffer probe 24, the gas from the first gas inlet 12 is fed via line 26 to the first inlet 28 of the first multi-way valve 14, while at the same time the vacuum pump 18 sucks in gas through the second gas inlet 20, which is fed via line 30 to the inlet 32 ​​of the second multi-way valve 22. In a first switching state, the first multi-way valve 14 connects the first inlet 28 to the first outlet 34, so that the gas sucked in through the first gas inlet 12 is fed via the first outlet 34 to the connecting line 42.A portion of this gas stream is diverted via the throttled line 64 and fed to the mass spectrometric gas analyzer 16, while the remaining gas stream is added to the atmosphere via the junction point 44 through the second throttle 66 and the vacuum pump 18. At the same time, the second multi-way valve 22 directs the gas drawn from the second gas inlet 20 from the inlet 32 ​​to the second outlet 40, from where the gas is fed via the line 48 and via the junction point 44 into the common connecting line 42. From there, the gas is conveyed to the atmosphere via the vacuum pump 18.

[0027] Subsequently, both multi-way valves 14, 22 are synchronously switched from the first switching state to a second switching state. In the second switching state, the first multi-way valve 14 directs the gas from the first gas inlet 12 via the second gas outlet 38 to the vacuum pump 18, without this gas entering the gas analyzer 16. Meanwhile, the second multi-way valve 22 directs the gas from the second gas inlet 20 via the first gas outlet 36 into the common connecting line 42, from which a partial flow is fed to the gas analyzer 16 for analysis via the throttled line 64.

[0028] By synchronously and simultaneously switching the two multi-way valves 14, 22, gas from only one of the two gas inlets 12, 20 enters the gas analyzer 16, where it can be analyzed, while the gas from the other gas inlet is pumped to atmosphere via the vacuum pump 18. By simply switching the two multi-way valves 14, 22 synchronously, the two gas inlets 12, 20 can be alternately connected to the gas analyzer without significant delays and / or pressure surges occurring during switching. The continuously pumped flow through both lines 26, 30 maintains the pressure gradient in the line, thus avoiding a pressure surge at the inlet to the detection system during switching.

[0029] A further advantage of the continuous gas flow through the two lines 26, 30 is that gas taken in through the two inlet openings 12, 20 also reaches the switching valves 14, 22 simultaneously. The passage time of the gas front through the lines 26, 30 can be several seconds. If the line not connected to the gas analyzer 16 or the leak detector 56 were not continuously pumped, this would result in a delay in the response time of several seconds.

Claims

1. Leak detection device (10) comprising a gas analyzer (16), a vacuum pump (18), a first gas inlet (12), and a second gas inlet (20), a first multi-way valve (14) having a first inlet (28) and at least a first and a second outlet (34, 38), wherein the inlet (28) of the first multi-way valve (14) is connected to the first gas inlet (12), characterized in that the leak detection device (10) further comprises a second multi-way valve (22) having a first inlet (32) and at least a first and a second outlet (36, 40), wherein the inlet (32) of the second multi-way valve (22) is connected to the second gas inlet (20), wherein the two first outlets of the two multi-way valves (14, 22) are connected to the gas analyzer (16), and the two second outlets of the two multi-way valves (14, 22) are connected to the vacuum pump (18), wherein the multi-way valves (14, 22) are configured and controlled by a valve control device such that the inlet (28) of the first multi-way valve (14) is connected to its first outlet (34) if the inlet (32) of the second multi-way valve (22) is connected to its second outlet (40) and the two multi-way valves (14, 22) are synchronously switched.

2. The leak detection device (10) according to claim 1, characterized in that the two gas inlets (12, 20) are arranged on different sniffer probes.

3. The leak detection device (10) according to any one of the preceding claims, characterized in that the gas analyzer (16) is a mass spectrometric leak detector (56) having a multi-stage high vacuum pump (60).

4. The leak detection device (10) according to claim 3, characterized in that the vacuum pump (18) is a separate auxiliary pump that is not connected to the leak detector (56).

5. The leak detection device (10) according to claim 3, characterized in that the vacuum pump (18) forms a pump stage of the multi-stage high vacuum pump (60).

6. The leak detection device (10) according to any one of the preceding claims, characterized in that the two first outlets (34, 36) are connected to the gas analyzer (16) via a common connecting branch (64), while the two second outlets (38, 40) are connected to the vacuum pump (18) via a common connecting line (42).

7. The leak detection device (10) according to any one of the preceding claims, characterized in that the two first outlets are connected to the two second outlets, and are connected to the gas analyzer (16) via a throttled line (64) and to a connecting branch connecting the vacuum pump (18) to the high vacuum pump (60) via a throttled further line (42).

8. A method for sniffer leak detection with a leak detection device (10) according to any one of the preceding claims, characterized by the following steps: switching on the vacuum pump (18), connecting the inlet (28) of the first multi-way valve (14) with its first outlet (34), and connecting the inlet (32) of the second multi-way valve (22) with its second outlet (40), analyzing the gas drawn in through the first gas inlet (12) by means of the gas analyzer (16), while gas is drawn in through the second gas inlet (20) by means of the vacuum pump (18), synchronously switching the two multi-way valves (14, 22), while the vacuum pump (18) remains on, and analyzing the gas drawn in through the second gas inlet (20) by means of the gas analyzer (16), while gas is drawn in through the first gas inlet (12) by means of the vacuum pump (18).