Leak detection method and associated leak detector

Abstract

The invention relates to a method for detecting a leak from an object to be tested (3), the method comprising the following steps: placing a predefined volume inside or around the object to be tested under vacuum; measuring at least one parameter representative of the pressure in the predefined volume over time by means of a first pressure sensor (13) independent of the nature of at least one gaseous species, and a second pressure sensor (15) dependent on the nature of the at least one gaseous species; determining a pressure variation from the parameters measured by the first sensor (13); comparing the representative pressure parameters measured by the sensors in order to determine a correction coefficient; correcting the determined pressure variation by means of the determined correction coefficient in order to infer therefrom the presence of a leak. The invention further relates to an associated leak detector.

Description

Leak detection method and associated leak detector

[0001] The present invention relates to a leak detection method and a corresponding leak detector for checking the tightness of an object to be tested, based on monitoring the evolution of pressure in a predefined volume inside or surrounding the object to be tested. Technical background

[0002] Leak detectors and corresponding leak detection methods are used to verify that the leakage rate of objects does not exceed a predetermined threshold.

[0003] Leak detection methods based on monitoring pressure changes, enabling the detection of large leaks, are known.

[0004] The object to be tested is usually placed under vacuum and then isolated from the pumping, and the evolution of the pressure in the object to be tested is monitored to determine how the pressure rises in the object to be tested.

[0005] However, the pressure can rise not because of a leak but because of outgassing, which can become predominant at low pressures. Existing solutions cannot distinguish between a pressure increase due to a leak and one due to outgassing, which can lead to diagnostic errors.

[0006] Another well-known, more effective, and more sensitive method for verifying the airtightness of an object under test involves performing a leak test using a tracer gas, particularly helium or hydrogen. This method relies on the tracer gas's ability to detect leaks more easily than other gases due to their smaller size. This method allows for the detection of even small leaks.

[0007] However, in the case of large leaks, the use of tracer gas, for example helium, may prove unsuitable because it leads to a large consumption of helium which is expensive and the presence of a large quantity of tracer gas can impair the quality of subsequent detections.

[0008] One aim of the present invention is to overcome these drawbacks, at least partially, by providing an improved leak detection method. Another aim of the invention is to find a solution that limits the amount of tracer gas used, thereby reducing the cost of detection tests while maintaining the same detection performance. A further aim of the invention is to reduce the cost of the equipment required for the detection process.

[0009] To this end, the invention relates to a method for detecting a leak in an object under test, implemented by a leak detector comprising at least one valve configured to fluidly isolate or fluidically connect a pumping unit and a predefined volume inside or surrounding the object under test. The method comprises the following steps: evacuating the predefined volume; measuring at least one parameter representative of the pressure in the predefined volume over time, using a first pressure sensor of the leak detector, the first pressure sensor being independent of the nature of at least one gaseous species in the predefined volume; determining a pressure variation from the representative pressure parameters measured over time by the first pressure sensor; and measuring at least one parameter representative of the pressure in the predefined volume over time, using a second pressure sensor.of the leak detector, the second pressure sensor being dependent on the nature of at least one gaseous species, comparison of the representative pressure parameters measured by said first sensor and by said second sensor, determination of a correction coefficient representative of the presence of outgassing, based on the comparison results, correction of the pressure variation determined by means of the determined correction coefficient, the presence of a leak being deduced from the corrected pressure variation.

[0010] Thus, using the two pressure sensors separately makes it easy to distinguish whether the pressure increase is due to a leak and / or degassing.

[0011] The invention also relates to a leak detector, configured to implement at least partially a method for detecting a leak from an object under test as defined above. The leak detector comprises: at least one valve configured to connect a pumping unit and a predefined volume within or surrounding the object under test; a first pressure sensor configured to measure at least one parameter representative of the pressure in the predefined volume, the first pressure sensor being independent of the nature of at least one gaseous species in the predefined volume; a second pressure sensor configured to measure at least one parameter representative of the pressure or at least one other parameter representative of the pressure in the predefined volume, the second pressure sensor being dependent on the nature of at least one gaseous species; and a processing unit.

[0012] The processing unit may include at least one processing means configured: to receive and analyze representative pressure parameter measurements transmitted by each pressure sensor, so as to determine pressure values; to determine a pressure variation from the representative pressure parameters measured over time by the first pressure sensor; to compare the pressure values ​​determined from said measurements transmitted by each pressure sensor; and to determine a correction coefficient representative of the presence of outgassing, based on the comparison results; to correct the pressure variation determined by means of the correction coefficient determined; and to deduce the presence of a leak from the corrected pressure variation.

[0013] The said detection method and / or leak detector may further include one or more of the following characteristics described below, taken separately or in combination.

[0014] The leakage rate can be calculated using the following formula (1): (1): with Q corresponding to the leakage rate, ΔP corresponding to the determined pressure variation, Δt corresponding to the predetermined time interval, V corresponding to the predetermined volume, eta corresponding to the correction coefficient.

[0015] During the correction step, the determined pressure variation can be multiplied by the determined correction coefficient.

[0016] The detection process may include at least a preliminary step of calibrating the two pressure sensors.

[0017] At least one gaseous species can be chosen from water vapor, oil vapor, alcohol vapor, solvent vapor.

[0018] The first sensor in question is, for example, a capacitive sensor.

[0019] The said first sensor may include a first fixed electrode and a second electrode formed by a membrane configured to be deflected according to the pressure.

[0020] The pressure value can be deduced from the distance between the first electrode and the membrane of said first sensor.

[0021] The second sensor in question is, for example, a humidity sensor.

[0022] The second sensor in question is, for example, a partial pressure sensor for water vapor.

[0023] The second sensor is, for example, a Piran gauge, in which a filament is configured to be heated.

[0024] The pressure value can be deduced from the amount of heat given off by the filament by thermal conduction into the environment.

[0025] The detection process may include the following steps: determining a leak rate from the corrected pressure variation, and comparing the leak rate with a predefined threshold associated with the presence of a leak.

[0026] The detection process may include a leak detection phase on the object to be tested based on tracer gas detection, comprising the following steps: aspirating gas from the predefined volume, establishing fluidic communication of the predefined volume with a tracer gas analyzer of the leak detector, introducing tracer gas into or around the object to be tested, and analyzing the aspirated gases from the predefined volume to detect the presence of tracer gas in these gases.

[0027] The tracer gas is, for example, helium.

[0028] The tracer gas is, for example, hydrogen.

[0029] The detection of the presence of tracer gas can be carried out by mass spectrometry.

[0030] The presence of tracer gas can be detected by optical spectrometry.

[0031] The leak detection phase on the object to be tested, based on tracer gas detection, can be implemented when the leak rate is below a predetermined threshold.

[0032] The leak detector may include: a device for introducing tracer gas into or around the object to be tested, a tracer gas analyzer configured to detect the presence of tracer gas in the predefined volume, and at least one additional valve configured to connect the tracer gas analyzer and the predefined volume in fluidic communication.

[0033] 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:

[0034] shows a schematic view of a leak detector according to an example implementation.

[0035] shows a schematic view of a leak detector according to another embodiment example.

[0036] is a graph representing the evolution over time of the pressure recorded by a first pressure sensor and by a second pressure sensor of the leak detector of the laou of the.

[0037] In these figures, identical elements bear the same reference numbers.

[0038] 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.

[0039] 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. Detailed description

[0040] The present invention relates to a leak detector 1 (Figures 1 and 2) for leak testing of test objects 3. The invention also relates to a corresponding method for detecting leaks in a test object 3. A "test object" is an object whose leak tightness is to be checked. The internal volume of the test object 3 can be fluidly connected to the leak detector 1, either directly or optionally via a conduit.

[0041] Leak detector 1 allows, in particular, the detection of large leaks, for example greater than 10 -3 mbar.Ls -1 (10 -4 Pa.m 3 .s -1 ). Leak detector 1 can also detect small leaks, for example less than 10 -3 mbar.Ls -1 (10 -4 Pa.m 3 .s -1 ), without the use of tracer gas, or by limiting the amount of tracer gas.

[0042] The object to be tested 3 may optionally be received in a test chamber 5. The test chamber 5 may be external to the leak detector 1.

[0043] Leak detector

[0044] General description

[0045] In general, the leak detector 1 may include at least one valve 11 or a set of valves 11, at least two pressure sensors 13, 15, a processing unit 21, and optionally a tracer gas analyzer 17 and a tracer gas introduction device 19.

[0046] The leak detector 1 is fluidically connected to a predefined volume. The predefined volume may correspond to the interior of the object to be tested 3. Alternatively (not shown), the predefined volume may correspond to the internal volume of the test chamber 5, surrounding the object to be tested 3.

[0047] Valve 11 or valve set 11 can be controlled, such as a solenoid valve or a set of solenoid valves.

[0048] The pressure sensors comprise at least a first sensor 13 and a second sensor 15. The two pressure sensors 13, 15 are fluidly connected to the predefined volume.

[0049] Pressure sensors 13 and 15 are advantageously suited for measurement under vacuum. Preferably, pressure sensors 13 and 15 can operate with short response times, particularly on the order of a second.

[0050] A first pressure sensor 13 is configured to measure a pressure or a parameter representative of the pressure in the predefined volume, being independent of the nature of at least one gaseous species, in particular outgassing, in the predefined volume whose pressure is measured.

[0051] Preferably, the first pressure sensor 13 is a capacitive sensor.

[0052] In particular, it can be a capacitive diaphragm sensor (also called a capacitive diaphragm gauge), forming a plate capacitor with a first fixed electrode and a second electrode formed by the diaphragm. The diaphragm deflects according to the pressure. During operation, the diaphragm deflection as a function of the change in capacitance can be measured. When the diaphragm is deflected, the distance between the electrodes, and therefore the capacitance of the capacitor, changes. The pressure value can be deduced from the distance between the electrode and the diaphragm. This property allows the first pressure sensor 13 to be completely independent of the gas species in the predefined volume whose pressure is being measured. The diaphragm can be metallic or ceramic. The diaphragm thickness can be adapted according to the pressure range in which the capacitive sensor is intended to be used.

[0053] The second pressure sensor 15 is configured to measure a pressure or a parameter representative of the pressure of the predefined volume. This can be the same pressure parameter measured by the first pressure sensor 13 or another pressure-representative parameter. The second pressure sensor 15's function depends on the nature of the gas(s) in the predefined volume whose pressure is being measured.

[0054] The second pressure sensor 15 is, for example, a Pirani gauge in which a filament is configured to be heated. The pressure value can be deduced from the amount of heat given off by the filament through thermal conduction into the environment.

[0055] According to another example, the second pressure sensor 15 can be a humidity or partial pressure sensor for water vapor. The invention also applies to other gaseous species, in particular other outgassing compounds, such as oil vapor, alcohol vapor, and solvent vapor.

[0056] Regarding the processing unit 21, it includes one or more processing means, such as an electronic card, a controller or computer or processor, a memory.

[0057] The processing unit 21 can be connected to one or more elements of the leak detector 1 to communicate with and / or control these elements. Alternatively, the leak detector 1 can include several interconnected processing units to communicate with and / or control different elements of the leak detector 1.

[0058] The tracer gas analyzer 17 and the tracer gas introduction device 19 are described in more detail later.

[0059] Figures 1 and 2 show two embodiments of leak detector 1, the differences of which are explained.

[0060] First method of implementation

[0061] According to a first embodiment shown in the figure, the leak detector 1 includes pressure sensors 13, 15, a valve 11, and the processing unit 21.

[0062] The processing unit 21 can be connected to the pressure sensors 13, 15 to receive their respective pressure measurements or representative pressure parameters.

[0063] The treatment unit 21 can be connected to the valve 11, particularly when it is a solenoid valve, to control its opening / closing operation.

[0064] Valve 11 can be configured to fluidly isolate or fluidically connect a pumping unit 9 and the predefined volume.

[0065] The pumping unit 9 can be configured to evacuate the predefined volume fluidly connected to the pumping unit 9.

[0066] When the predefined volume corresponds to the interior of the object under test 3, the internal volume of the object under test 3 can be fluidly connected to the pumping unit 9, as in the example shown in Figure 1. According to the alternative (not shown), where the predefined volume corresponds to the internal volume of the test chamber surrounding the object under test 3, the test chamber can then be fluidly connected to the pumping unit 9.

[0067] The pumping unit 9 includes, for example, a primary vacuum pump such as a diaphragm pump or a dry pump.

[0068] Second embodiment

[0069] A second embodiment, shown in Figure 1, differs from the first embodiment in that the leak detector 1 also allows for leak detection based on the detection of a tracer gas. Only the differences compared to the first embodiment are explained below.

[0070] The detection device 7 includes, in addition to the pressure sensors 13, 15 and the processing unit 21, a set 11 of valves, including at least two, for example four, valves 11a-11d, a tracer gas analyzer 17 and a tracer gas introduction device 19.

[0071] The predefined volume, which corresponds to the internal volume of the object to be tested 3 or of the test chamber 5, is fluidically connected to the tracer gas analyzer 17.

[0072] At least one additional valve compared to the first embodiment is provided; in the example described, three additional valves are provided. Valves 11a-11d are configured to fluidly isolate or fluidically connect the predefined volume to the pumping unit 9 and / or the tracer gas analyzer 17. They allow or prevent the passage of gas between an inlet of the leak detector 1 and the tracer gas analyzer 17 and / or the pumping unit 9. These may be controllable valves 11a-11d, such as solenoid valves.

[0073] For example, at least one valve 11a, 11b allows the pumping unit 9 to be fluidly isolated or connected to the leak detector 1. In particular, a first valve 11a can be arranged between the pumping unit 9 and the tracer gas analyzer 17, specifically between the pumping unit 9 and the secondary vacuum pump when one is provided, so as to allow the primary and secondary vacuum pumps to be fluidly isolated or connected to each other. A second valve 11b can be arranged between the inlet of the leak detector 1 and the pumping unit 9.

[0074] At least one other valve 11c, 11d, referred to as a test valve, is arranged, for example, to allow or prevent the passage of gas between the inlet of the leak detector 1 and an inlet of the tracer gas analyzer 17. This allows the tracer gas analyzer 17 to be fluidically isolated or fluidically connected to the predefined volume.

[0075] The processing unit 21 can be connected to the valves 11a-11d, particularly when they are solenoid valves, to control their opening / closing operation.

[0076] The tracer gas introduction device 19 can be either an injection device or a tracer gas spraying device 19. The tracer gas is, for example, helium or hydrogen. The tracer gas can be introduced by, for example, injecting it into the object to be tested 3 or spraying it around the object to be tested 3.

[0077] When the predefined volume corresponds to the inside of the object to be tested 3, the tracer gas introduction device 19 is configured to introduce the tracer gas into the internal volume of the test chamber 5 (around the object to be tested 3), as shown in the figure, for example by spraying tracer gas around the object to be tested 3.

[0078] Alternatively, the tracer gas introduction device 19 can be configured to introduce the tracer gas inside the object to be tested 3. In this case, the predefined volume corresponds to the internal volume of the test chamber 5 surrounding the object to be tested 3.

[0079] The tracer gas analyzer 17 is configured to measure the flow rate or concentration of at least one gaseous species used as a tracer gas. The tracer gas analyzer 17 is, for example, a mass spectrometer or an optical spectrometer. The tracer gas analyzer 17 includes, for example, a secondary vacuum pump, such as a turbomolecular pump. Alternatively, it can be fluidically connected to such a pump, particularly at the suction end.

[0080] The tracer gas analyzer 17 is configured to detect the presence of tracer gas among pumped gases from the predefined volume or even to determine the concentration of tracer gas among the pumped gases.

[0081] The tracer gas analyzer 17 is configured to provide a measurement signal representative of a tracer gas flow or concentration in the object to be tested 3, placed in the test chamber 5 exposed to the tracer gas, or, in the test chamber 5 surrounding the object to be tested 3 filled with tracer gas.

[0082] The use of tracer gas detection makes it possible to detect very small leaks, for example with flow rates of up to 10 -8 mbar.Ls -1 (10 -9 Pa.m 3 .s -1 ).

[0083] The leak detector 1 can implement at least in part a leak detection process, the different stages of which are described below.

[0084] Leak detection method

[0085] Calibration

[0086] The leak detection process may include at least one preliminary calibration step or calibration of the two pressure sensors 13, 15.

[0087] For calibration, the two pressure sensors 13 and 15 can each measure a predefined number of reference pressures or parameters representative of the reference pressure, within a sealed volume containing only air and exhibiting negligible outgassing. The output measurements of the two pressure sensors 13 and 15 for each pressure or parameter can be analyzed. A minimum difference between the output measurements of the two pressure sensors 13 and 15 can be defined. A calibration relationship can be established to ensure that the pressure values ​​measured or determined from the representative pressure parameters obtained from the two pressure sensors 13 and 15 are consistent.

[0088] During calibration, it is also possible for the two pressure sensors 13 and 15 to measure a predefined number of reference pressures or parameters representative of the reference pressure, respectively, in a sealed volume where the outgassing rate (e.g., humidity) is 100%. The output measurements of the two pressure sensors 13 and 15 for each pressure or parameter can be analyzed to define a maximum deviation, particularly as a percentage, between the output measurements of the two pressure sensors 13 and 15.

[0089] Detection phase by monitoring for a pressure increase (or major leak detection phase)

[0090] A detection phase can be implemented during a control / test cycle of the leak tightness of an object to be tested 3.

[0091] One step involves evacuating the predefined volume, such as the internal volume of the object to be tested 3 or the internal volume of the chamber to be tested 5.

[0092] To achieve this, the treatment unit 21 can control valve 11 or valves 11a-11d, in the case of controllable valve(s) 11 and 11a-11d, to establish fluid communication between the pumping unit 9 and the predefined volume. Pumping allows the predefined volume to be evacuated until a predefined pressure level is reached. Valves 11a, 11c, and 11d can be in the closed position, and valve 11b can be in the open position.

[0093] When the predefined pressure level is reached, the pumping unit 9 can be fluidically isolated. The treatment unit 21 can control valve 11 or valves 11a-11d to fluidly isolate the pumping unit 9 and the predefined volume. Valve 11 or 11b can be in the closed position. The pressure level (or a parameter representative of the pressure level) can be transmitted to the treatment unit 21 by at least one pressure sensor 13, 15.

[0094] A subsequent step involves monitoring the evolution, more specifically the increase, of the pressure, or a representative pressure parameter, within the predefined volume over time, at least for a predetermined time interval. This predetermined time interval may depend on the size of the predetermined volume, for example, a few seconds for a small volume to several tens of minutes for a larger one.

[0095] To do this, the pressure or a parameter representative of the pressure in the predefined volume is measured over time by the first pressure sensor 13.

[0096] A variation, in particular an increase, in the pressure within the predefined volume, can be estimated or determined based on pressure values ​​measured or determined from measurements of representative pressure parameters, transmitted by the first pressure sensor 13. The processing unit 21 can be configured to determine the variation such as the pressure increase over the predetermined time interval.

[0097] If the pressure / the pressure representative parameter rises too quickly, this may indicate a leak, and this leak can be quantified from the variation (the increase) determined over a predetermined time interval.

[0098] Furthermore, the pressure or parameter (or another parameter) representative of the pressure in the predefined volume is measured over time by the second pressure sensor 15.

[0099] Lamontre presents a graph with a first curve C13 representing an example of the evolution over time t (in seconds) of the pressure P measured in millibars by the first pressure sensor 13 (or a parameter representative of the pressure), and a second curve C15 representing an example of the evolution over time t of the pressure P measured by the second pressure sensor 15 (or a parameter representative of the pressure). Each curve C13, C15 may contain a series of points, for example, separated by a predetermined measurement interval. The values ​​of pressure P and time T on the graph are given for illustrative purposes only and are in no way limiting.

[0100] The pressure sensors 13, 15 transmit their respective measurements over time, for example to the processing unit 21 configured to receive them.

[0101] The processing unit 21 can, when it receives measurements of representative pressure parameters from a pressure sensor 13 or 15, analyze or process the received measurements in order to determine the corresponding pressure values.

[0102] The processing unit 21 can possibly make the measurements transmitted by the two sensors 13, 15 comparable when it comes to quantities which cannot be directly compared with each other.

[0103] During a comparison step, pressure measurements over time from the first pressure sensor 13 (curve C13) can be compared to pressure measurements over time from the second pressure sensor 15 (curve C15). When pressure sensors 13 and 15 each measure a representative pressure parameter, the pressure values ​​determined from these representative pressure parameters received from each sensor 13 and 15 are compared. The processing unit 21 can implement the comparison step(s).

[0104] The presence of degassing can be deduced (for example by the processing unit 21) from the measurements of the second pressure sensor 15 compared with those of the first pressure sensor 13.

[0105] Indeed, in the event of degassing, humidity for example increases which affects the pressure value / of the parameter representing the pressure measured by the second pressure sensor 15, such as a Pirani gauge, (which is sensitive to the nature of the gaseous species) unlike the first pressure sensor 13, such as a capacitive sensor.

[0106] When the pressure values ​​determined from the representative pressure parameters transmitted by the two pressure sensors 13, 15 agree, the absence of significant outgassing can be deduced.

[0107] On the contrary, if there is a difference in the pressure values ​​determined from the representative pressure parameters measured and transmitted by the two pressure sensors 13, 15, this indicates degassing.

[0108] A correction coefficient that is representative of the presence or absence of degassing can be determined from the comparison results, in particular by the processing unit 21, between the measurements at the output of the first pressure sensor 13 and the second pressure sensor 15.

[0109] The correction coefficient can be defined by also taking into account the results of comparison between the output measurements of the first pressure sensor 13 and the second pressure sensor 15 during calibration, in particular concerning the minimum deviation and the maximum deviation.

[0110] Alternatively or in addition, the correction coefficient can be defined by learning, based on experience.

[0111] The correction coefficient may optionally be expressed as a percentage.

[0112] In the example of the, the two curves C13, C15 correspond to different pressure measurements (or the representative pressure parameter) coming respectively from the first pressure sensor 13 and the second pressure sensor 15.

[0113] The correction coefficient is determined by the difference between the two curves C13, C15. The difference between the two curves C13, C15 is of a roughly constant nature in the illustrated example.

[0114] The greater the difference, the more significant the outgassing. The difference is greatest when the pressure increase is solely due to outgassing, for example, of water vapor. Conversely, the closer the two curves C13 and C15 are, the more the pressure increase indicates an air leak.

[0115] The pressure variation previously determined from the measurements of the first pressure sensor 13 can be corrected using the correction coefficient, in particular by multiplying the pressure variation by the correction coefficient.

[0116] For example, if the difference is at its maximum, the correction factor is 0%. The pressure variation (pressure rise) representative of a leak is then reduced to zero, as this corresponds solely to the degassing of the walls.

[0117] Conversely, if the two curves C13 and C15 are in agreement, meaning the difference is 0%, then the correction factor is, for example, 100%. The determined pressure variation (pressure rise) is taken into account as is, because it corresponds solely to air entering the predefined volume, and not to the degassing of the walls.

[0118] According to one option, the correction coefficient can be defined as a linear function of the difference between the two curves C13, C15, taking into account the extreme positions and differences previously defined, and possibly with a margin of error, for example, of 0.01% to 5%.

[0119] Thus, for example, if the second curve C15 lies between the two extreme positions (i.e., the position with a minimum deviation of 0% and the position with a maximum deviation of 100% from the first curve C13), for instance in the middle or approximately in the middle, the correction factor is 50%. As another example, if the second curve C15 lies with a deviation of approximately 20% to 30% from the first curve C13, the correction factor is approximately 70% to 80%.

[0120] According to another option, an intermediate position can be defined, particularly during calibration, to allow for a more precise determination of the correction factor. In this case, during a leak test cycle of an object under test 3, the correction factor can be determined based on the difference between the two curves C13 and C15 by extrapolation, which can be linear, using the extreme positions and the intermediate position defined during calibration. As before, a margin of error, for example, of 0.01% to 5%, can be taken into account.

[0121] It is also possible to define the correction coefficient in a non-linear way from the data resulting from the calibration and the position of the curves C13, C15.

[0122] The leakage rate of the object can be deduced from the corrected pressure variation over time, that is, from the determined pressure variation and the correction factor. The predetermined time interval and predetermined volume are also taken into account.

[0123] Processing unit 21 can determine this leakage rate.

[0124] The leakage rate can be calculated using the following formula (1): (1): with Q corresponding to the leakage rate, ΔP corresponding to the determined pressure variation, Δt corresponding to the predetermined time interval, V corresponding to the predetermined volume, eta corresponding to the correction coefficient.

[0125] The processing unit 21 can compare this leak rate with a predefined threshold associated with the presence of a leak. For example, if the leak rate exceeds the predefined threshold, then a leak is detected.

[0126] If a leak is detected, the leak detection process may stop and the object under test 3 is considered defective. A signal indicating the extent of the leak may also be emitted.

[0127] Distinguishing between a pressure increase (or an increase in a pressure-representative parameter) due to degassing or a leak improves sensitivity and allows for the detection of leaks with flow rates up to 10 -3 or even 10 -4 mbar.Ls -1 (10 -4 at 10 -5 Pa.m 3 .s -1 ) without necessarily requiring the use of tracer gas, unlike prior art leak detectors based on pressure variation detection, which only allow the detection of very large leaks, for example, with a flow rate greater than 10 -2 mbar.Ls -1 (10 -3 Pa.m 3 .s -1 ).

[0128] Detection phase based on tracer gas detection (or small leak detection phase)

[0129] The detection process may optionally include a small leak detection phase on the object to be tested 3, based on the detection of a tracer gas, such as helium.

[0130] This can be the case when a large leak is not detected by monitoring the increase in pressure (or a parameter representative of the pressure), for example when the leak rate is below the predetermined threshold.

[0131] The predefined volume, inside or around the object to be tested 3, can be put into fluidic communication with the pumping unit 9, as previously described, to be put under vacuum.

[0132] The tracer gas can be introduced around the object to be tested 3, in particular in the test chamber 5, as in the configuration of the, or alternatively in the object to be tested 3 according to a configuration not shown.

[0133] The introduction of tracer gas can be carried out during a vacuuming of the predefined volume.

[0134] The pumping unit 9 can draw in or extract gases from the predefined volume.

[0135] The predefined volume can be made to communicate fluidically with the tracer gas analyzer 17, in particular by opening at least one of the test valves 11c-11d. The processing unit 21, for example, can control this opening.

[0136] During the test, the second valve 11b, located between the inlet of the leak detector 1 and the pumping unit 9, is closed. Once at least one test valve 11c or 11d is opened, a portion of the gas from the predefined volume, drawn in by the pumping unit 9 and the secondary vacuum pump, possibly containing the tracer gas, then flows towards the tracer gas analyzer 17. The tracer gas can flow back up the secondary vacuum pump.

[0137] The tracer gas analyzer 17 can analyze aspirated gases from a predefined volume to detect the presence of tracer gas. Tracer gas detection is performed, for example, by mass spectrometry or optical spectrometry. The tracer gas analyzer 17 can provide a measurement of the tracer gas flow, for example, to the processing unit 21.

[0138] If a leak is detected, its extent can be determined based on the tracer gas concentration measured by the tracer gas analyzer 17, and a signal can be emitted to indicate the leak's magnitude. If no leak is detected, the procedure can then be repeated with another object to be tested 3.

[0139] Implementing the leak detection phase using tracer gas detection, in the absence of a leak, using a method that monitors pressure increases or a parameter representative of pressure, limits tracer gas consumption while allowing the detection of small leaks (up to 10 -8 mbar.Ls -1 that is 10 -9 Pa.m 3 .s -1 ).

[0140] Thus, the leak detector 1 according to one or the other of the embodiments described allows the detection of a leak, using a sensor dependent on the nature of the gas (second pressure sensor 15), in addition to a sensor independent of the nature of the gas (first pressure sensor 13), in order to be able to distinguish a leak from a degassing.

[0141] The presence of a leak can be deduced (for example, by the processing unit 21) from the pressure variation corrected by means of the correction coefficient. In other words, the pressure rise curve derived from the measurements of the first sensor 13 is corrected to account for outgassing using the measurement from the second sensor 15.

[0142] The leak detector 1 can also combine the use of the two pressure sensors 13, 15 with an analyzer 17 of a tracer gas, such as helium, in order to further improve sensitivity.

Claims

A method for detecting a leak from an object under test (3), implemented by a leak detector (1) comprising at least one valve (11; 11b) configured to fluidly isolate or fluidically connect a pumping unit (9) and a predefined volume inside or surrounding the object under test (3), said method comprising the following steps: evacuating the predefined volume, measuring at least one representative pressure parameter in the predefined volume over time, by means of a first pressure sensor (13) of the leak detector (1), the first pressure sensor (13) being independent of the nature of at least one gaseous species in the predefined volume, determining a pressure variation from the representative pressure parameters measured over time by the first pressure sensor (13),characterized in that said method further comprises the following steps: measurements of at least one parameter representative of the pressure in the predefined volume over time, by means of a second pressure sensor (15), of the leak detector (1), the second pressure sensor (15) being dependent on the nature of at least one gaseous species, comparison of the representative pressure parameters measured by said first sensor (13) and by said second sensor (15), determination of a correction coefficient representative of the presence of outgassing, based on the comparison results, correction of the pressure variation determined by means of the determined correction coefficient, the presence of a leak being deduced from the corrected pressure variation. A detection method according to the preceding claim, wherein during the correction step, the determined pressure variation is multiplied by the determined correction coefficient. A detection method according to any one of the preceding claims, comprising at least one preliminary calibration step of the two pressure sensors. A detection method according to any one of the preceding claims, wherein at least one gaseous species is selected from water vapor, oil vapor, alcohol vapor, solvent vapor. A detection method according to any one of the preceding claims, wherein said first sensor (13) is a capacitive sensor, in particular comprising a first fixed electrode and a second electrode formed by a membrane configured to be deflected according to the pressure, and the pressure value is deduced from the distance between the first electrode and the membrane. A detection method according to any one of the preceding claims, wherein said second sensor (15) is a humidity or partial pressure water vapor sensor. A detection method according to any one of the preceding claims, wherein said second sensor (15) is a Pirani gauge in which a filament is configured to be heated and the pressure value is deduced from the amount of heat given off by the filament by thermal conduction into the environment. A detection method according to any one of the preceding claims, comprising the following steps: determining a leak rate from the corrected pressure variation, and comparing the leak rate with a predefined threshold associated with the presence of a leak. A detection method according to any one of the preceding claims, comprising a leak detection phase on the object to be tested (3) based on tracer gas detection, comprising the following steps: aspirating gas from the predefined volume, fluidic communication of the predefined volume with a tracer gas analyzer (17) of the leak detector (1), introduction of tracer gas, such as helium, inside the object to be tested (3) or around the object to be tested (3), analysis of the aspirated gases from the predefined volume to detect the presence of tracer gas in these gases. A method according to the preceding claim, wherein the detection of the presence of tracer gas is carried out by mass spectrometry or optical spectrometry. A method according to any one of claims 9 or 10, wherein the leak detection phase on the object to be tested based on tracer gas detection is implemented when the leak rate is below a predetermined threshold. Leak detector (1), configured to implement at least in part a method for detecting a leak from an object to be tested according to any one of the preceding claims, the leak detector (1) comprising: at least one valve (11; 11b) configured to establish fluidic communication between a pumping unit (9) and a predefined volume inside or surrounding the object to be tested (3), a first pressure sensor (13) configured to measure at least one parameter representative of the pressure in the predefined volume, the first pressure sensor (13) being independent of the nature of at least one gaseous species in the predefined volume, a second pressure sensor (15) configured to measure at least one parameter representative of the pressure or at least one other parameter representative of the pressure in the predefined volume, the second pressure sensor (15) being dependent on the nature of at least one gaseous species,and a processing unit (21) comprising at least one processing means configured: to receive and analyze the representative pressure parameter measurements transmitted by each pressure sensor (13, 15), so as to determine pressure values; to determine a pressure variation from the representative pressure parameters measured over time by the first pressure sensor (13); to compare the pressure values ​​determined from said measurements transmitted by each pressure sensor (13, 15); and to determine a correction coefficient representative of the presence of outgassing, based on the comparison results; to correct the determined pressure variation by means of the determined correction coefficient; and to deduce the presence of a leak from the corrected pressure variation. Leak detector (1) according to the preceding claim, further comprising: a device for introducing tracer gas (19) into or around the object to be tested, a tracer gas analyzer (17) configured to detect the presence of tracer gas in the predefined volume, and at least one additional valve (11c, 11d) configured to connect the tracer gas analyzer and the predefined volume in fluidic communication.

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