Method for monitoring the drift of a leak detector and associated equipment

Abstract

The invention relates to a method for monitoring the drift of measurements of a leak detector (1) of a tracer gas of a piece of equipment (100), capable of implementing a cycle for testing the tightness of a part to be tested (A) placed in a measurement chamber (101). The method comprises the following steps: injecting tracer gas with a predefined concentration value into a pipe communicating with the detector, the detector reading an internal concentration of tracer gas, comparing the read value with the predefined concentration value and, if they are different, determining a correction coefficient, and applying the correction coefficient to the measured value of the tracer gas concentration in the chamber during the test cycle. The invention also relates to the equipment used to carry out the method.

Description

Description Title of the invention: Method for controlling the drift of a leak detector and associated equipment technical field

[0001] The present invention relates to a method for drift control of a leak detector. The present invention also relates to associated equipment for implementing the control method. Technical background

[0002] Production lines in industries such as pharmaceuticals or automotive may require leak testing of objects and parts. In production, leak testing is generally performed automatically and repeatedly on a very large number of objects or parts to be tested. The goal is to ensure the absence of leaks at a target operating pressure.

[0003] A well-known method for verifying the airtightness of a part under test involves performing a leak test using a tracer gas, particularly helium. This method relies on the detection of helium passing through leaks more easily than other gases, due to the small size of the helium atom.

[0004] The leak detector can be integrated into the production line. In one embodiment, the part to be tested is charged with tracer gas and placed in a measuring chamber connected to the leak detector, which, in one example, can be evacuated. The leak detector can then measure the flow or concentration of the tracer gas in the measuring chamber and is configured to provide a measurement signal representative of the flow or concentration of the tracer gas.

[0005] The amplitude of the measurement signal representing the tracer gas flow or concentration is compared to a rejection threshold. Depending on the result, the part under test is either rejected, sent to the quality control department for analysis, or its leak-tightness is certified. The sole criterion for determining whether a part is leak-tight is therefore exceeding the rejection threshold of the measured tracer gas flow or concentration. The measurement value is critical, and it is essential that the resulting measurement (or metrological value) be as reliable and stable as possible.

[0006] However, leak detection equipment, such as mass spectrometers or optical emission spectrometers, can be subject to drift. This drift can be caused by organic contamination (for example, in the chamber, pumps, or other components). It can also be caused by wear, which can be premature due to repetitive cycles with pressure variations associated with use on production lines.

[0007] However, for certain industries, particularly pharmaceuticals, adherence to standards is crucial, and it is necessary to regularly verify, for example every two to three weeks, that the measurements are correct by adding a leak to a sample known to be leak-free. This ensures that the parts tested between the last two checks are indeed leak-proof. However, this generally requires shutting down the equipment and involving maintenance experts, which is costly and causes delays in the production line.

[0008] One aim of the present invention is to overcome these drawbacks, at least partially, by providing a method for controlling the drift of the leak detector to ensure the integrity of the leak test. The invention also aims to provide equipment for controlling the drift of the leak detector. Summary of the invention

[0009] To this end, the invention relates to a method for monitoring the drift of measurements from a tracer gas leak detector in a piece of equipment. The equipment is configured to perform at least one leak test cycle on at least one part to be tested, placed in a measurement chamber of the equipment. The part may be charged with tracer gas. The leak test cycle comprises: a step of establishing fluid communication between the leak detector and the measurement chamber, via at least one valve; and, while the leak detector is in fluid communication with the measurement chamber, a step of measuring the concentration of the tracer gas in the measurement chamber, performed by the leak detector, so as to test the leak tightness of the part by comparing the measured concentration to a predefined rejection threshold.

[0010] According to the invention, the drift control method further comprises the following steps: injection of tracer gas with a predefined concentration value into a pipe in fluidic communication with the leak detector, the predefined concentration value being less than the predefined rejection threshold, outside of a measurement step of the leak test cycle, the leak detector records an internal concentration of tracer gas, comparison of the recorded value of the internal concentration with the predefined concentration value, in case of difference, determination of at least one correction coefficient so that the measured value of the internal concentration corresponds to the predefined concentration value and application of the correction coefficient to the measured value of the tracer gas concentration in the measurement chamber during the leak test cycle.

[0011] Thus, a known reference leak of the tracer gas (also called a calibrated leak or "background noise") is injected into the leak detector, which allows the "background noise" to be fixed at a controlled value. In case of drift, a mathematical compensation is applied, thus avoiding the need to recalibrate the leak detector.

[0012] The invention also relates to equipment for implementing such a method for monitoring the drift of measurements from a gas leak detector. The equipment comprises: a measuring chamber in which a part to be tested, for example, one loaded with tracer gas, is intended to be placed; a tracer gas leak detector configured to measure a concentration of the tracer gas in the measuring chamber and to record an internal concentration of tracer gas in the leak detector; at least one valve configured to fluidically connect or fluidically isolate the leak detector and the measuring chamber; and a tracer gas injection element configured to inject tracer gas with a predefined concentration value into a pipe in fluidic communication with the leak detector. at least one element for comparing the measured value of the internal concentration with the predefined concentration value, and at least one element for determining, based on the comparison results, at least one correction coefficient to be applied to the measured value of the tracer gas concentration in the measuring chamber.

[0013] The control method and equipment may also include one or more of the following characteristics described below, taken separately or in combination.

[0014] The tracer gas with the predefined concentration value can be injected during a leak test cycle and / or outside of the leak test cycle.

[0015] The tracer gas with the predefined concentration value can be injected continuously.

[0016] In particular, the tracer gas can be injected continuously with the predefined concentration value, during the leak test cycle, regardless of the implementation stage of the leak test cycle.

[0017] The injection element is configured to continuously inject the tracer gas with the predefined concentration value during the leak test cycle, regardless of the implementation stage of the leak test cycle.

[0018] The control process may include a fluidic isolation step between the leak detector and the measuring chamber via at least one valve.

[0019] The leak detector can measure the internal concentration of tracer gas when the leak detector is fluidly isolated from the measuring chamber.

[0020] The control process may include at least one step of detecting the open or closed position of at least one valve.

[0021] For example, when at least one valve is in a closed position to fluidly isolate the leak detector from the measuring chamber, the steps of comparing the measured value of the internal concentration with the predefined concentration value, and of determining at least one correction coefficient, can be implemented.

[0022] As an alternative or in addition, the control process may include at least one step of measuring the pressure in the measuring chamber.

[0023] If the pressure measured in the measuring chamber is greater than a predefined pressure threshold, the steps of comparing the measured value of the internal concentration with the predefined concentration value, and of determining at least one correction coefficient, can be implemented.

[0024] According to yet another variant or in addition, the control process may include at least one step of measuring the pressure of the leak detector over a predetermined period.

[0025] If a pressure variation exceeding a predefined pressure variation threshold is detected over this predetermined period, the steps of comparing the measured value of the internal concentration with the predefined concentration value, and of determining at least one correction coefficient, can be stopped.

[0026] The step of determining at least one correction coefficient can be implemented by a leak detector processing unit or a central unit of the equipment.

[0027] The correction coefficient is, for example, a multiplying coefficient.

[0028] The tracer gas with a predefined concentration value is, for example, injected between the leak detector and at least one valve.

[0029] The predefined concentration value is, for example, lower than the predefined rejection threshold, by at least 10% of the predefined rejection threshold.

[0030] For example, the predefined rejection threshold can be less than 10' 3 mbar.l / s (10' 4 Pa.m 3 / s), including between 10' 3 mbar.l / s and 10' 7 mbar.l / s (between 10' 4 Pa.m 3 / s and 10' 8 Pa.m 3 / s), preferably 10' 5 mbar.l / s (10' 6 Pa.m 3 / s).

[0031] According to this example, the predefined concentration value can be between 10' 6 mbar.l / s and 10' 10 mbar.l / s (between 10' 7 Pa.m 3 / s and 10' 11 Pa.m 3 / s), preferably 10' 8 mbar.l / s (10' 9 Pa.m 3 / s).

[0032] The control process may include a step of calculating the average of the recorded value of the internal concentration over a predefined period of less than 60 s, preferably between 1 s and 10 s, in particular on the order of 5 s.

[0033] The control procedure may include a step of calculating the derivative of the measured value of the internal concentration over the period. The calculated derivative can be used to determine if the measured leak value is sufficiently stable to apply the correction coefficient.

[0034] The control process may include a step of measuring the ambient temperature of a tracer gas injection point with the predefined concentration value using at least one temperature sensor.

[0035] The control process may include at least one step to define at least one compensation formula linking a temperature variation and a variation in the value of the injected tracer gas via a predefined factor.

[0036] The control process may include an adjustment step by applying an additional correction coefficient to the measured value of the tracer gas concentration in the measuring chamber during the leak test cycle.

[0037] This additional correction coefficient can be determined from a user-specific reference leak, and allows for even further adjustment of the measured value.

[0038] The leak detector can be chosen from a mass spectrometer or an optical emission spectrometer.

[0039] The control process may include a step of evacuating said spectrometer, by means of an associated pumping unit, when said spectrometer is fluidly isolated from the measuring chamber.

[0040] The control process may include a step of evacuating the measuring chamber with a pressure compatible with the leak detector, by means of at least one pumping unit connected to the measuring chamber and at least one valve.

[0041] The step of evacuating the pressure of the measuring chamber can be implemented by a first primary pumping group from atmospheric pressure to an intermediate pressure, and then by at least one other pumping group from the intermediate pressure to said compatible pressure.

[0042] The tracer gas can be chosen from helium, hydrogen, argon, nitrogen, propane, carbon dioxide.

[0043] The equipment may include at least one pumping unit connected to the measuring chamber.

[0044] The equipment may include at least one control and / or communication device configured to regulate the gas leak detector and / or exchange information with at least one other device of the equipment. Brief description of the drawings

[0045] Other advantages and features of the invention will become clearer upon reading the following description, given by way of illustrative and non-limiting example, and the accompanying drawings, among which:

[0046] [Fig. 1] is a schematic view of an example of the implementation of equipment including at least one leak detector.

[0047] [Fig. 2] is a graph showing a measurement signal, provided by a leak detector, of a leak rate of a tracer gas in a measurement chamber containing a part to be tested as a function of time during a leak test cycle.

[0048] [Fig. 3] is a graph showing a measurement signal, provided by a leak detector with a calibrated internal leak, of a leak rate of a tracer gas in a measurement chamber containing a part to be tested as a function of time during a leak test cycle.

[0049] In these figures, identical elements bear the same reference numbers.

[0050] Only the elements necessary for understanding the invention are represented.

[0051] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined or interchanged to provide other embodiments, without departing from the scope of the invention as defined by the claims.

[0052] In the description, certain elements can be indexed, for example, "first element" or "second element." In this case, it is simply indexing to differentiate and name similar but not identical elements. This indexing does not imply any priority of one element over another, and such designations can easily be interchanged without departing from the scope of the present invention. Nor does this indexing imply any chronological order.

[0053] In this context, "upstream" refers to an element that is positioned before another element in relation to the direction of flow of the pumped gases. Conversely, "downstream" refers to an element positioned after another element in relation to the direction of flow of the pumped gases. Detailed description

[0054] Equipment

[0055] Figure 1 shows an example of equipment 100 for leak testing objects or parts to be tested A. An object or part to be tested A therefore corresponds to an object or part whose leak testing is to be carried out. Equipment 100 can be used to test several parts to be tested A repeatedly and, for example, automatically.

[0056] The parts to be tested A can be loaded with tracer gas. In other words, these parts to be tested A contain in their internal volume (which is not under vacuum) a tracer gas, detectable by a tracer gas leak detector 1, of the equipment 100.

[0057] The tracer gas is, for example, helium. Alternatively, the tracer gas can be chosen from hydrogen, argon, propane, carbon dioxide or nitrogen.

[0058] Equipment 100 includes a measuring chamber 101 for receiving the parts to be tested A.

[0059] The measuring chamber 101 is intended to be fluidly connected to the leak detector 1, via at least one valve VI, V2, V3 arranged to fluidly communicate or fluidly isolate the leak detector 1 and the measuring chamber 101. This may be, for example, at least one controllable valve VI, V2, V3, such as a solenoid valve.

[0060] Equipment 100 may include at least one pumping unit PI, P2, P3 connected to the measuring chamber 101. Pumping units PI, P2, P3 may include one or more vacuum pumps. For example, this could include at least one primary vacuum pump and / or at least one turbomolecular vacuum pump.

[0061] According to the particular embodiment illustrated, four valves VI, V2, V3, V4 are provided on parallel gas pipelines or flow lines to which the measuring chamber 101 is connected. This is an illustrative example of equipment 100, and this example is in no way limiting.

[0062] A first pumping unit P1 can be installed on a first pipeline, referred to as the pumping pipeline, which includes a first valve VI. A second pumping unit P2 can be installed on a second pipeline, referred to as the pumping pipeline, which includes a second valve V2. The second pumping unit P2 comprises, for example, a vacuum pump, such as a turbomolecular vacuum pump 2A, and a primary vacuum pump 2B connected in series, with the turbomolecular vacuum pump 2A positioned upstream of the primary vacuum pump 2B in the direction of gas flow (see arrows F). A third pumping unit P3 can be installed on a third pipeline, referred to as the pumping pipeline, which includes a third valve V3.

[0063] The equipment 100 may further include a ventilation duct communicating with the measuring chamber 101, optionally including a filter, and at least one controllable valve, such as a solenoid valve, to allow the chamber to be recharged with clean, particle-filtered air and to increase the pressure in the measuring chamber 101 to atmospheric pressure. According to the illustrated embodiment, a fourth duct including a fourth valve V4 performs this ventilation function.

[0064] At least one pumping unit can be connected to the leak detector 1 in such a way as to allow the sampling of gases that pass at least partially through the leak detector 1. In the particular example shown, the third pumping unit P3 is connected to the leak detector 1. More specifically, the leak detector 1 is, for example, connected to the suction of a vacuum pump of the third pumping unit P3. The third valve V3 is, for example, fluidically connected to a pipe communicating with the inlet of the leak detector 1. The third valve V3 can, in particular, be fluidly interposed between the measuring chamber 101 and the leak detector 1.

[0065] At least one valve or set of valves VI, V2, V3, for example controllable, allow the measuring chamber 101 to be put into fluidic communication with at least one pumping group PI, P2, P3 to lower the pressure in the measuring chamber 101 initially at atmospheric pressure, down to a pressure compatible for the use of the leak detector 1.

[0066] Valves VI, V2, V3 can successively put measuring chamber 101 into fluidic communication with the first pumping group PI, then the second pumping group P2, then the third pumping group P3. The pumping groups Pl, P2 can allow the pressure around the part to be tested to be gradually lowered, preferably as quickly as possible, down to the pressure compatible with the use of the leak detector 1.

[0067] Equipment 100 may include a pressure sensor or gauge 3 connected to the measuring chamber 101, so as to measure the pressure in the measuring chamber 101. The measured pressure can be compared to a pressure threshold to define when to open or close at least one valve VI, V2, V3, until the pressure compatible for the operation of the leak detector 1 is reached.

[0068] According to one method, an inlet of the leak detector 1 is connected to the internal volume of the measuring chamber 101, intended to be evacuated, containing a test piece A, and the test piece A is filled with tracer gas, for example beforehand (for example a sealed product).

[0069] The leak detector 1 is configured to measure a flow or concentration of tracer gas in the measuring chamber 101.

[0070] The leak detector 1 includes, for example, a mass spectrometer. The mass spectrometer can be pre-calibrated. The pumping unit, for example the third pumping unit P3, connected to the leak detector 1, can achieve a vacuum of less than 10⁻¹⁰ ... 3 mbar (0.1 Pa) at the mass spectrometer.

[0071] As an alternative, leak detector 1 includes, for example, an optical emission spectrometer.

[0072] The leak detector 1 can provide a measurement signal representative of the tracer gas concentration in the measurement chamber 101.

[0073] Leak detector 1 is also configured to detect an internal concentration of tracer gas in leak detector 1.

[0074] A tracer gas injection element 4 is provided to inject tracer gas with a predefined concentration value C into a pipe in fluidic communication with the leak detector 1. The injected tracer gas chosen is preferably predominant over the other gases usually present in background noise.

[0075] Leak detector 1 can in particular provide a measurement signal representative of its internal concentration of tracer gas.

[0076] The equipment 100 may further include at least one sensor for measuring the temperature (not shown) of the environment surrounding, or near, the leak of injected tracer gas. Such a temperature sensor may, for example, be positioned as close as possible to a nozzle of the tracer gas injection element 4. It may also be positioned within the environment of the injected tracer gas leak.

[0077] At least one additional valve (not shown) may optionally be arranged between the leak detector 1 and the tracer gas injection element 4, in order to achieve finer adjustment of the leak detector 1, in particular to check that the leak detector 1 has no internal leak or that it is within the usual specifications.

[0078] Equipment 100 may include a control and / or communication device configured to adjust leak detector 1 and / or to ensure the operation of leak detector 1 and / or to exchange information with at least one other device of equipment 100.

[0079] For example, but not limited to, the control and / or communication unit can manage valve sequences, retrieve signal values ​​(leakage value, pressure value, temperature value).

[0080] Equipment 100 may include a central processing unit (not shown), such as a computer or electronic board, comprising one or more controllers or microcontrollers or processors and memory.

[0081] The central unit of equipment 100 may include the control and / or communication unit.

[0082] The central unit of equipment 100 can be configured to control, among other things, the reception of the parts to be tested A in the measurement chamber 101. The central unit of equipment 100 can specifically be configured to control the flow of injected tracer gas. This central unit of equipment 100 can also be configured to control the opening and closing of valves VI, V2, V3, and V4.

[0083] The central unit of equipment 100 can be connected to the pressure gauge 3 to receive measurement signals and to one or more valves VI, V2, V3, to control their opening / closing based on the pressure measured by the gauge. pressure 3. The opening of at least one valve VI, V2, V3 can be programmed to be allowed when the measured pressure crosses a certain pressure threshold.

[0084] The leak detector 1 may further include a control unit or processing unit (not shown), such as an electronic board, comprising a controller, computer, or processor and memory, and including, for example, an input / output interface. The control unit of the leak detector 1 may or may not be separate from the central unit of the equipment 100. If the units are separate, the central unit may control the control unit of the leak detector 1. This control unit of the leak detector 1 may be connected to the central unit of the equipment 100 to communicate, in particular, measurements.

[0085] Equipment 100, in particular the central unit of equipment 100, may include at least one processing means or element for comparing measured and received values ​​to reference values. For example, the processing means may be configured to compare a measured value of the internal tracer gas concentration of the leak detector 1 with the predefined concentration value C of the injected tracer gas.

[0086] Equipment 100, in particular the central unit of equipment 100, may also include at least one element for determining, based on comparison results, at least one correction coefficient to be applied to the measured value of tracer gas concentration in the measuring chamber.

[0087] This equipment 100 can implement at least one leak test cycle of at least one part to be tested A, as described below.

[0088] Leak test cycle

[0089] Figure 2 shows a graph of the tracer gas concentration Q (or leak rate) measured by the leak detector 1 of equipment 100 (also referring to Figure 1), in mbar.l / s (Pa.m 3 / s in SI units), as a function of time t (in seconds) during an example of a sealing cycle.

[0090] The test piece A, which may be pre-charged with tracer gas, is placed in the measuring chamber 101 initially at atmospheric pressure. This can be controlled by the central unit of the equipment 100.

[0091] When using a spectrometer, for example a mass spectrometer or an optical emission spectrometer, the measuring chamber 101 is placed under vacuum. The pressure can be gradually reduced.

[0092] During the leak test cycle, the internal atmosphere of the measuring chamber 101 is depressurized by at least one primary vacuum pump of a pumping unit PI, alone or in parallel with at least one other auxiliary pumping unit P2, P3. The measuring chamber 101 can thus be evacuated to a pressure compatible with the leak detector 1 comprising a spectrometer, by means of at least one pumping unit PI, P2, P3 connected to the measuring chamber 101 and at least one valve VI, V2, V3.

[0093] According to the particular embodiment illustrated in Figure 1, the first valve VI can be in the open position to allow the flow of gas through the first pipeline and to evacuate the measuring chamber 101 first by the primary vacuum pump of the first pumping group PI which makes it possible to achieve a primary vacuum rapidly around the part to be tested A, from atmospheric pressure to an intermediate pressure.

[0094] By means of the pressure gauge 3, as soon as the intermediate pressure falls below a certain threshold, the first valve VI can be closed and the second valve V2 in the open position to allow in this example the turbomolecular vacuum pump 2A coupled to the primary vacuum pump 2B, to continue to lower the pressure in the measuring chamber 101 until the pressure compatible with the leak detector 1.

[0095] Then, when the pressure measured by the pressure gauge 3 reaches the compatible pressure, the measuring chamber 101 containing the part to be tested A is brought into fluidic communication with the leak detector 1, notably by opening at least one valve. In the example described, this is achieved by closing the second valve V2 and opening the third valve V3.

[0096] The opening and closing sequence of valves VI, V2, V3 can be controlled by the control and / or communication unit, or the central unit, of equipment 100.

[0097] If there is a leak, the tracer gas escapes from the inside to the outside of the part being tested A. At least some of the gas collected by the pumping unit P3, possibly containing the tracer gas, then flows towards the leak detector 1, which measures a concentration of the tracer gas (or leak rate) in the measuring chamber 101. The measurement signal can be provided to the processing unit and / or the central unit of the equipment 100 for comparison with a predefined rejection threshold S (Figure 2), so as to test the leak tightness of the part to be tested A.

[0098] For example, the predefined rejection threshold S can be less than 10' 3 mbar.l / s (10' 4 Pa.m 3 / s), including between 10' 3 mbar.l / s and 10' 7 mbar.l / s (between 10' 4 Pa.m 3 / s and 10' 8 Pa.m 3 / s), preferably 10' 5 mbar.l / s (10' 6 Pa.m 3 / s).

[0099] The measuring chamber 101 is then ventilated and the tested part is removed from the measuring chamber 101. This can be controlled by the central unit of the equipment 100.

[0100] For example, after the elapsed time of a predetermined period, the central unit of the equipment 100 can control the fluidic isolation of the leak detector 1 from the measuring chamber 101, in particular by closing the valve V3.

[0101] Then, the central unit of the equipment 100 controls the ventilation, specifically by controlling the opening of valve V4. As a non-limiting illustrative example, the entire cycle lasts, for example, around 10 or 15 seconds, and the period during which the leak detector 1 is in fluidic communication with the part to be tested A can be very short, for example, around 2 seconds. The remainder of the cycle can consist of vacuuming and ventilation.

[0102] A new part to be tested A can be introduced into the measuring chamber 101 and the cycle restarts.

[0103] In addition, the equipment 100 (figure 1) can implement one or more steps of a drift control process for measurements of a tracer gas leak detector, described below.

[0104] Drift control method

[0105] According to the drift control procedure, tracer gas is injected at a predefined concentration C into a pipe in fluidic communication with the leak detector 1. This is implemented by the tracer gas injection element 4. This therefore represents a known, calibrated, or controlled leak of the tracer gas at the leak detector 1 (e.g., from the mass spectrometer or optical emission spectrometer).

[0106] The tracer gas with the predefined concentration value C (or calibrated leak) can be injected between the leak detector 1 and at least one valve, for example the third valve V3, allowing fluidic communication or fluidic isolation between the leak detector 1 and the measuring chamber 101.

[0107] As shown schematically in Figure 2, the predefined concentration value C of the tracer gas (or calibrated leak) is lower than the predefined rejection threshold S for the part being tested A, or even negligible. Furthermore, the value for this calibrated leak is chosen to be higher than the minimum detectable by the leak detector 1.

[0108] The predefined concentration value C is, for example, less than the predefined rejection threshold S for the parts to be tested A, by at least 10% of the predefined rejection threshold S.

[0109] For example, for a predefined rejection threshold S less than 10' 3 mbar.l / s (10' 4 Pa.m 3 / s), including between 10' 3 mbar.l / s and 10' 7 mbar.l / s (between 10' 4 Pa.m 3 / s and 10' 8 Pa.m3 / s), preferably 10' 5 mbar.l / s (10' 6 Pa.m 3 / s), the predefined concentration value can be between 10' 6 mbar.l / s and 10' 10 mbar.l / s (between 10' 7 Pa.m 3 / s and 10' 11 Pa.m 3 / s), preferably 10' 8 mbar.l / s (10' 9 Pa.m 3 / s).

[0110] The calibrated leak can be injected during a leak test cycle and / or outside the leak test cycle as described previously.

[0111] Since the calibrated leak value is below the rejection threshold S, a leak in the test part A can be detected even if tracer gas is injected into the leak detector 1 during a tracer gas concentration measurement step in the measuring chamber 101 of a leak test cycle. Thus, as illustrated in Figure 3, during measurements to test the leak tightness of a test part A (as previously described with reference to Figures 1 and 2), the tracer gas concentration Q in the test part A is added to the predefined tracer gas concentration value C, which constitutes the calibrated leak. This still allows the leak tightness of the test part A to be verified with the desired accuracy.

[0112] In particular, the calibrated leak can be injected continuously, i.e. both during a leak test cycle and outside of the leak test cycle, in order to avoid accumulation and stabilization times.

[0113] For example, the injection step can be performed continuously during a leak test cycle, regardless of the specific step, particularly the measurement step, within the leak test cycle that is implemented. This makes it very easy to generate a stable and controlled background noise.

[0114] According to one embodiment, the injection step can be implemented at least when the leak detector 1 is fluidically isolated from the measuring chamber 101.

[0115] If the calibrated leak is continuously injected during a leak test cycle of a part under test A, the leak detector 1 can be in fluidic communication with the measuring chamber 101 during the injection.

[0116] In a subsequent step of the drift control process, the leak detector 1 detects an internal concentration of tracer gas from the leak detector 1.

[0117] However, for drift control of leak detector 1, this step to record the internal concentration must not be carried out during a measurement in progress during a leak test cycle of a test part A. The equipment 100 is preferably in standby or standby mode. Otherwise, the recorded concentration results must not be taken into account for the drift control procedure of leak detector 1.

[0118] There are different ways to ensure that a measurement of a leak test cycle is not in progress, and that the leak detector 1 is used to measure its internal concentration of tracer gas and not a leak from a part to be tested A which would be in the measuring chamber 101.

[0119] According to a first example of implementation, the step to measure the internal concentration of tracer gas is carried out when the leak detector 1 is fluidically isolated from the measuring chamber 101.

[0120] For this purpose, the control method includes a fluidic isolation step between the leak detector 1 and the measuring chamber 101 via at least one valve, for example at least the third valve V3. Such a fluidic isolation step is implemented if the leak detector 1 and the measuring chamber 101 were previously in fluidic communication.

[0121] The fluidic isolation of the leak detector 1 can be controlled by the central unit of the equipment 100, in particular by controlling at least one valve V3.

[0122] Thus, the leak detector 1 is isolated from any test part A that may be present in the measuring chamber 101 and could leak. This eliminates any potential uncontrolled external influence that could disrupt the measurement.

[0123] When the leak detector 1 is fluidically isolated from the measuring chamber 101, the leak detector 1 can be evacuated using an associated pumping unit, the third pumping unit P3, as described in the equipment example 100. This pumping unit P3 is also fluidly isolated from the measuring chamber 101. The vacuum achieved at the leak detector 1, particularly at the spectrometer, is, for example, less than 10⁻¹⁰ m. 3 mbar (10' 4 Pa.m 3 / s).

[0124] The control process may include at least one step for detecting the open or closed position of at least one valve, the third valve V3 in the example of equipment 100 described. This detection step may be controlled by the central processing unit of equipment 100.

[0125] When valve V3 is in the closed position, fluidically isolating the leak detector 1 from the measuring chamber 101, the concentration value(s) measured by the leak detector 1 can be used for the subsequent control procedure. Specifically, the steps of comparing the measured internal concentration value with the predefined concentration value C, and determining at least one correction factor, which will be described later, can be implemented.

[0126] Conversely, if valve V3 is in an open position, establishing fluidic communication between the leak detector 1 and the measuring chamber 101, the measured / recorded concentration value(s) are not taken into account for the subsequent control procedure. Specifically, the steps of comparing the recorded internal concentration value with the predefined concentration value C, and of determining at least one correction factor, described later, are either not carried out or are stopped.

[0127] Alternatively, it may be envisaged that the measuring chamber 101, which would be free of part to be tested A, be connected to the leak detector 1, during the step to record the internal concentration of tracer gas of the leak detector 1.

[0128] According to a second embodiment, which can be applied as an alternative or in addition to the first embodiment, a pressure measured in the measuring chamber 101 can be monitored.

[0129] The control process then includes at least one step of measuring the pressure in the measuring chamber 101, for example using the pressure gauge 3.

[0130] The measured pressure can then be compared to a predefined pressure threshold. The predefined pressure threshold is preferably greater than or equal to 1 mbar (100 Pa).

[0131] If the pressure measured in the measuring chamber 101 is greater than the predefined pressure threshold, the concentration value(s) measured by the leak detector 1 may be taken into account for the rest of the control process, in particular for the steps of comparing the measured value of the internal concentration with the predefined concentration value C, and of determining at least one correction coefficient described later, which may be implemented.

[0132] The central unit of equipment 100 (or the control and / or communication unit) can receive the pressure values, perform the comparison to the predefined pressure threshold, and control the subsequent steps of the control process accordingly.

[0133] According to yet a third embodiment example, which can be applied as an alternative or in addition to one or both of the previous embodiment examples, a pressure variation at the level of the leak detector 1 can be monitored.

[0134] The control procedure then includes at least one step of measuring the pressure of the leak detector 1 over a predetermined period. The variation in pressure measured over this predetermined period can be observed and compared to a predefined pressure variation threshold.

[0135] According to a non-limiting example, the predefined pressure variation threshold can be around 0.1 mbar (10 Pa).

[0136] If an abnormal pressure variation is detected, particularly if it exceeds the predefined pressure variation threshold, the measured tracer gas concentration value(s) are not taken into account for the remainder of the control procedure. Specifically, the steps of comparing the measured internal concentration value with the predefined concentration value C, and of determining at least one correction factor, described later, are not implemented or are stopped.

[0137] Conversely, as long as the pressure variation measured at the leak detector remains within a given range, the measured tracer gas concentration value(s) can be used for the subsequent control procedure. The steps of comparing the measured internal concentration value with the predefined concentration value C, and determining at least one correction factor, can then be implemented or continued.

[0138] The central unit of equipment 100 (or the control and / or communication unit) can receive the pressure values, perform the comparison to the predefined pressure variation threshold, and control the subsequent steps of the control process accordingly.

[0139] Subsequently, after recording the internal concentration of tracer gas in the leak detector 1, the recorded value of the internal concentration is compared to the predefined concentration value C (for injection).

[0140] In case of difference, at least one correction coefficient, in particular a multiplier coefficient, is determined / calculated so that the measured value of the internal concentration corresponds to the predefined concentration value C (calibrated leak).

[0141] The control procedure may include at least one step of calculating the average of the measured internal concentration value over a predefined period. This predefined period is, for example, less than 60 seconds, preferably between 1 and 10 seconds, and in particular on the order of 5 seconds. This average can then be used to determine the correction factor.

[0142] The control procedure may also include at least one step for calculating the derivative of the measured internal concentration value. The derivative of the internal concentration measured over a predefined period (for example, on the order of 3 or 5 seconds) is calculated to ensure that the measured leak value is sufficiently stable to allow confidence in the determined correction. Conversely, if the derivative shows that the leak is not stable, the calculations to determine the correction factor may not be performed.

[0143] Furthermore, the temperature of the injected tracer gas is a parameter that can influence the leak value, and in particular, cause the leak value to vary over time. A higher temperature can generate a larger leak, while a lower temperature can generate a smaller leak. Taking into account the influence of the temperature representative of the atmosphere / environment around the leak allows for greater accuracy in the compensation.

[0144] In this case, the control procedure may still include at least one step of measuring the ambient temperature of the tracer gas injection point with a predefined concentration value, in particular by means of at least one sensor of Temperature. Temperature variation can be monitored over a predefined period.

[0145] At least one compensation formula can link a temperature variation and a variation in the value of the injected tracer gas via a predefined factor. As a specific, non-limiting example, the predefined factor could be on the order of 0.2% / °C.

[0146] This factor can be taken into account in compensation calculations, to determine the correction coefficient.

[0147] The central unit of equipment 100 (or the control and / or communication unit) can receive the recorded or measured values ​​of internal concentration and / or temperature, and / or perform the steps of comparison, and / or calculation, and determination of the correction coefficient.

[0148] The determined correction coefficient can then be applied to the measured value of the tracer gas concentration in the measuring chamber 101 during a leak test cycle.

[0149] Thus, the calibrated leak is used to automatically compensate, mathematically correct, any drift of the leak detector 1, thanks to the correction coefficient, without interfering with a leak test cycle, without requiring a production stoppage, or the intervention of an expert for maintenance and recalibration of the leak detector 1.

[0150] In parallel, one or more metrological verification steps for equipment 100 can be implemented by a user using a different, user-specific reference leakage, based on a non-leaking reference part. For even more precise compensation, the leakage detected by leak detector 1 can be adjusted to match the user's other reference leakage using an additional correction factor.

[0151] More specifically, a leak test cycle can be implemented with the known reference part that does not leak and is placed in the measuring chamber 101. The reference part is similar to the parts to be tested A but certified leak-proof.

[0152] At least one V5 valve allows the introduction of tracer gas with a reference leak into the measuring chamber 101, thus simulating a leak in the non-leaking reference part. The leak test cycle steps are then implemented. as previously described. The tracer gas concentration measurement taken by the leak detector 1 is compared with the reference leak in order to verify if the leak detector 1 in the equipment 100 is still capable of verifying the tightness of the parts to be tested A according to the user's criteria.

[0153] Based on the comparison results, during an adjustment step, an additional correction coefficient is applied to the measured value of the tracer gas concentration in the measuring chamber during the leak test cycle.

[0154] Thus, the presence of a calibrated, continuous and known leak, which does not need to be stabilized, allows the internal concentration values ​​of tracer gas recorded by the leak detector 1 to be constantly adjusted mathematically, outside of an actual leak test cycle of a part to be tested A, in order to compensate for any drift and provide an accurate measurement signal, via the use of a correction coefficient, regardless of the aging of the leak detector 1, or even the loss of sensitivity.

[0155] In addition, a temperature sensor can allow for a more precise estimation of the actual loss of leak detector 1 and improve compensation.

[0156] User reference leakage thresholds can be taken into account during an adjustment step using an additional correction coefficient.

[0157] Mathematical compensation ensures a correct metrological value for as long as possible. This mathematical compensation does not require equipment 100 to be stopped for maintenance, nor does it require human intervention, nor does it require a dedicated recalibration step for the leak detector 1, thus reducing the required maintenance frequency and improving efficiency, while allowing for operation at the highest possible rate.

Claims

22 Demands

1. A method for controlling the drift of measurements of a leak detector (1) of a tracer gas in equipment (100), the equipment (100) being configured to perform at least one leak test cycle on at least one test part (A) placed in a measuring chamber (101) of the equipment (100), the leak test cycle comprising: a step of establishing fluid communication between the leak detector (1) and the measuring chamber (101), via at least one valve (V1, V2, V3), and when the leak detector (1) is in fluid communication with the measuring chamber (101), a step of measuring a concentration of the tracer gas in the measuring chamber (101), performed by the leak detector (1), so as to test the leak tightness of the part (A) by comparing the measured concentration to a predefined rejection threshold (S), characterized in that the drift control method includes the following steps: • injection of the tracer gas with a predefined concentration value (C) into a pipe in fluidic communication with the leak detector (1), the predefined concentration value (C) being lower than the predefined discharge threshold (S), • apart from a measurement step in the leak test cycle, the leak detector (1) records an internal concentration of tracer gas from the leak detector (1), • comparison of the measured value of the internal concentration with the predefined concentration value (C), • in case of a difference, determination of at least one correction coefficient so that the measured value of the internal concentration corresponds to the predefined concentration value (C), and • application of the correction coefficient to the measured value of the tracer gas concentration in the measuring chamber (101) during the leak test cycle.

2. A drift control method according to the preceding claim, wherein the tracer gas is continuously injected with the predefined concentration value, during the leak test cycle, regardless of the step implemented in the leak test cycle.

3. A drift control method according to any one of the preceding claims, comprising a fluidic isolation step between the leak detector (1) and the measuring chamber (101) via at least one valve (VI, V2, V3), and wherein the leak detector (1) measures the internal concentration of tracer gas when the leak detector (1) is fluidically isolated from the measuring chamber (101).

4. A drift control method according to any one of the preceding claims, comprising at least one step of measuring the pressure in the measuring chamber (101), and wherein if the pressure measured in the measuring chamber (101) is greater than a predefined pressure threshold, the steps of comparing the measured value of the internal concentration with the predefined concentration value (C), and of determining at least one correction coefficient are implemented.

5. A drift control method according to any one of the preceding claims, comprising at least one step of measuring the pressure of the leak detector (1) over a predetermined period, and wherein if a pressure variation greater than a predetermined pressure variation threshold is detected over the predetermined period, the steps of comparing the measured value of the internal concentration with the predetermined concentration value (C), and of determining at least one correction coefficient are stopped.

6. A drift control method according to any one of the preceding claims, wherein the correction coefficient is a multiplying coefficient.

7. A drift control method according to any one of the preceding claims, wherein the tracer gas with the predefined concentration (C) is injected between the leak detector (1) and at least one valve (V3).

8. A drift control method according to any one of the preceding claims, comprising a step of calculating the average of the measured value of the internal concentration over a predefined period of less than 60s, preferably between 1s and 10s, in particular on the order of 5s.

9. A drift control method according to any one of the preceding claims, comprising a step of measuring an ambient temperature of a tracer gas injection point with the predefined concentration value (C) by means of at least one temperature sensor and at least one step for defining at least one compensation formula linking a temperature variation and a variation in the value of the injected tracer gas via a predefined factor.

10. A drift control method according to any one of the preceding claims, comprising an adjustment step by applying an additional correction coefficient to the measured value of the tracer gas concentration in the measuring chamber (101) during the leak test cycle.

11. A drift control method according to any one of the preceding claims, wherein the leak detector (1) is selected from a mass spectrometer, optical emission spectrometer, the control method comprising a step of evacuating said spectrometer, by means of an associated pumping group (P3), when said spectrometer is fluidly isolated from the measuring chamber (law).

12. A drift control method according to any one of the preceding claims, comprising a step of evacuating the measuring chamber (101) with a pressure compatible with the leak detector (1), by means of at least one pumping unit (Pl, P2) connected to the measuring chamber (101) and at least one valve (VI, V2). 25

13. A drift control method according to the preceding claim, wherein the step of evacuating the pressure of the measuring chamber (101) is carried out by a first primary pumping group (PI) from atmospheric pressure to an intermediate pressure, and then by at least one other pumping group (P2) from the intermediate pressure to said compatible pressure.

14. A drift control method according to any one of the preceding claims, wherein the tracer gas is selected from helium, hydrogen, argon, nitrogen, propane, carbon dioxide.

15. Equipment (100) for implementing a method for monitoring the drift of measurements of a tracer gas leak detector (1) according to any one of the preceding claims, the equipment (100) comprising: a measuring chamber (101) in which a part to be tested (A) is intended to be placed, a tracer gas leak detector (1) configured to measure a concentration of the tracer gas in the measuring chamber (101) and to record an internal concentration of tracer gas in the leak detector (1), at least one valve (VI, V2, V3) configured to fluidically connect or fluidically isolate the leak detector (1) and the measuring chamber (101), a tracer gas injection element (4) configured to inject tracer gas with a predefined concentration value (C) into a pipe in fluidic communication with the leak detector (1),at least one element for comparing the measured value of the internal concentration with the predefined concentration value (C), and at least one element for determining, based on the comparison results, at least one correction coefficient to be applied to the measured value of the tracer gas concentration in the measuring chamber (101).

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