LEAK DETECTION SYSTEM BY SYNCHRONIZED DIRECT AND INDIRECT METHODS

Abstract

The invention relates to a leak detection system (1) for checking the tightness of an object (20) having at least one expandable flexible wall, said system comprising: – a sealed test chamber (101) configured to receive / accommodate the object (20) to be tested; – a device for pressurizing the interior volume of the test chamber (101) to a first test pressure value P1; – a device for pressurizing the interior volume of the object to be tested (20) to a second test pressure value P2, distinct from the first test pressure value P1; – a first sensor (103) for measuring a first leak level F1 in the test chamber (101), this determination being carried out by measuring a physical quantity representative of the leak level as a function of time;– a second measuring sensor (203) of a second leak level F2 of the object to be tested (20), this determination being carried out by measuring a physical quantity representative of the leak level as a function of time; – an electronic entity (30) configured to determine an actual leak Freal in the object to be tested (20) as a function of the first and second test pressure values P1, P2, and the first and second leak levels F1, F2 measured in a synchronized manner over the same test time interval ttest, respectively by the first and second measuring sensors (103, 203; 103', 203'). Figure for the abstract: [Fig. 1];

Description

Title of the invention: LEAK DETECTION SYSTEM USING SYNCHRONIZED DIRECT AND INDIRECT METHODS

[0001] The present invention relates to the field of leak detection systems and methods for monitoring the leaktightness of an object, more particularly based on the measurement of a physical quantity, such as a pressure or a flow rate, relative to a leak level.

[0002] There are different systems and methods for detecting leaks.

[0003] When it is desired to detect a leak by pressure variation, the object to be tested, the level of sealing of which is to be checked, undergoes a controlled pressure variation, that is to say that a known pressure variation is applied to a volume internal to the object (called the direct method) or to a closed volume surrounding said object (called the indirect method). Then, after a determined time, the pressure in the volume having undergone said pressure variation is measured again. If the object has a leak, then the measured pressure is different from the initial pressure.

[0004] A pressure variation is generally measured over a given time to enable the determination of a leak level relative to the object. Indeed, the pressure variation per unit of time can be linked to a leak level by the following mathematical relationship:

[0005] p yin which, F is the leakage generally expressed in cubic centimeters per minute (or cm3 / min), AP is the pressure variation in Pascal (Pa) measured in the volume, At the time interval (in seconds) of the measured pressure variation AP, V the relevant volume to be considered (for example the internal volume of the object) generally expressed in cubic centimeters (cm3), and k a multiplicative constant (in Pa1). Thus, regardless of the object or a sub-element of the object, it is possible to check whether it has leaks and to determine its level of sealing.

[0006] It will be noted that the leak can be expressed in a manner other than by pressure variation over a given period of time, for example in the form of a mass flow rate.

[0007] The formula which links the leak to a physical quantity can take different forms depending on the measurement method used and the physical quantity studied.

[0008] Thus, whatever the object or sub-element of the object to be tested, it is possible to check whether it has leaks and determine its level of sealing.

[0009] The object to be tested may be an electronic device, packaging, a container, etc. The tolerances on the level of sealing can therefore vary greatly depending on the object to be tested, its volume, its shape, its function, etc.

[0010] However, when the leak level that one seeks to determine is relatively small compared to the volume of the object to be tested, the parameters intrinsic to the object to be tested can make it difficult to measure the variation in pressure (or flow rate) and / or its repeatability. Indeed, in the case of test objects with flexible walls, the deformations of the wall when the internal volume of the object is subjected to a pressure variation, for example, can lead to pressure variations of an order of magnitude substantially equal to the level of the leaks that we are seeking to detect.

[0011] It is therefore particularly difficult to obtain reliable leak measurements and to distinguish a pressure variation linked to a leak in the part from a variation linked to an expansion of the part.

[0012] Research and tests have therefore been carried out by the holder to propose a method and a system for detecting leaks having improved sensitivity and allowing better repeatability in the detection of leaks, while improving the level of detectability of said leaks.

[0013] The invention is thus a new leak detection system for monitoring the tightness of an object having at least one expandable flexible wall, said system comprising:

[0014] - a sealed test chamber configured to receive / accommodate the object to be tested; - a device for pressurizing the internal volume of the object to be tested to a first test pressure value;

[0015] - a device for pressurizing the interior volume of the test chamber to a second test pressure value, distinct from the first pressure value; - a first sensor for measuring a first leak level in the object to be tested, this determination being carried out by measuring a physical quantity such as a pressure or a flow rate, as a function of time;

[0016] - a second sensor for measuring a second leak level in the chamber test, this determination being carried out by measuring a physical quantity such as pressure or flow rate, as a function of time;

[0017] - an electronic entity configured to determine a leak F in the object to be tested depending on the first and second test pressure values, and the first and second leak levels measured over a predetermined test time interval ttest, respectively by the first and second measuring sensors.

[0018] A leak detection system is therefore proposed by pressure change or by air flow measurement to check the tightness of an object to be tested, at least at least one wall is flexible and expandable, the system being configured to pressurize, in a synchronized manner and at distinct pressures, a volume internal to the object to be tested (called the direct method) and the test chamber surrounding said object (called the indirect method).

[0019] In this way, leak detection is not impacted by a variation in the volume of the part to be tested which creates a change in pressure (although it is not a leak) and which hinders the leak test.

[0020] The proposed system therefore makes it possible to test flexible parts, or at least parts having a flexible wall, by the synchronized combination of a direct test and an indirect test on the same part to be tested and a mathematical formula for predicting the measurement based on the difference in effect of the same change in volume of the part between two different absolute pressures inside the part to be tested and in a sealed chamber outside the part to be tested.

[0021] This new approach makes it possible, in the same cycle time required for testing a leak, to measure a smaller leak, and to improve the quality and repeatability of leak detection.

[0022] According to a possible implementation:

[0023] - the first measuring sensor is a pressure sensor configured to measure the pressure variations representative of the leakage level of the pressurized volume of the object to be tested;

[0024] - the second measuring sensor is a pressure sensor configured to measure pressure variations representative of the leakage level of the pressurized volume of the test chamber;

[0025] - the electronic entity being configured to determine an actual leak in the object to testing as a function of the first and second test pressure values, variations in the pressure in the pressurized interior volume of the object to be tested, and variations in the pressure in the pressurized interior volume of the test chamber, said variations being measured synchronously, over the same test time interval, respectively by the first and second pressure sensors.

[0026] The leak test can thus consist of synchronously testing the interior of the tested part and the sealed chamber outside the tested part in order to identify a real leak, and to differentiate it from the effects of expansion of the part, based on pressure variations measured by pressure sensors.

[0027] According to another possible implementation:

[0028] - the first measuring sensor is a flow meter configured to measure the mass flow variations representative of the leakage level of the pressurized volume of the object to be tested;

[0029] - the second measuring sensor is a flow meter configured to measure the mass flow variations representative of the leakage level of the pressurized volume of the test chamber;

[0030] - the electronic entity being configured to determine an actual leak in the object to testing as a function of the first and second test pressure values, the mass flow rate variations in the pressurized interior volume of the object to be tested, and the mass flow rate variations in the pressurized interior volume of the test chamber, said mass flow rate variations being measured over a test time interval, respectively by the first and second measuring sensors.

[0031] Instead of measuring a pressure drop, a flow rate corresponding to a leak can be measured. The leak test then consists of synchronously testing the interior of the tested part and the sealed chamber outside the tested part in order to identify a real leak, and to differentiate it from the effects of expansion of the part, based on variations in mass flow rate measured by flow meters.

[0032] According to a possible characteristic, the values of the test pressures are absolute pressures.

[0033] According to another possible characteristic, the ratio between the absolute test pressure values is at least equal to 1.1.

[0034] In an exemplary implementation, the absolute pressure inside the part to be tested is 10 mbar absolute and that in the test chamber is 45 mbar absolute, i.e. a ratio of 4.5.

[0035] According to a possible characteristic, the difference between the values of the absolute test pressures is at least equal to 0.005 bar.

[0036] According to another possible characteristic, the electronic entity determines the actual leakage level between the internal volume of the object to be tested and the internal volume of the test chamber as a function of the highest absolute test pressure and the lowest absolute test pressure, the leakage level measured on the lower pressure side, i.e. in the part to be tested or in the test chamber, and the leakage level measured on the lower pressure side, i.e. in the test chamber or in the part to be tested respectively.

[0037] According to a possible characteristic, the first measuring sensor and / or the second measuring sensor are differential measuring sensors.

[0038] Using differential pressure sensors has the advantages of being able to measure smaller pressure variations and of eliminating measurement errors linked to the mechanical and / or thermal behavior of the object being tested.

[0039] According to another possible characteristic, the electronic entity is configured to control the pressure difference between the interior volume of the object to be tested and outside the object to be tested so that this pressure difference does not exceed a predetermined threshold value.

[0040] The invention also relates to a method for detecting leaks implemented within a leak detection system as described previously, said method comprising the following steps:

[0041] - establishing a first test pressure in the test chamber by a device of pressurization for a period of time under pressure;

[0042] - establish in a synchronized manner and during the same period of time a second test pressure, different from the first pressure, in the object to be tested by a pressurizing device;

[0043] - determine over a test time interval a first leakage level in the test chamber by measuring a physical quantity as a function of time by means of a first measuring sensor, such as a pressure sensor;

[0044] - determine in a synchronized manner and over the same test time interval a second leakage level in the object to be tested by measuring a physical quantity as a function of time by means of a second measuring sensor, such as a pressure sensor;

[0045] - determine the actual leakage level of the object to be tested based on the first and

[0046] second leak levels measured over a predetermined test time interval

[0047] ttest, and first and second test pressure values.

[0048] The method according to the invention synchronizes the two direct and indirect tests with equal filling and stabilization times, and equal test times.

[0049] According to a possible characteristic, the steps of pressurizing the test chamber and the object to be tested each comprise a filling phase up to the desired test pressure and a stabilization phase.

[0050] According to another possible characteristic, the pressure difference between the interior of the object to be tested and the exterior of the object to be tested is controlled so as not to exceed a predetermined threshold value.

[0051] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the following description of particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the appended drawings, in which:

[0052] - [Fig.l], referenced [Fig.l], is a very schematic representation of a system leak detection according to one embodiment of the invention;

[0053] - [Fig.2], referenced [Fig.2], is a graph representing in the form of curves two examples of variations in leakage mass flow rate in a volume relative to the object to be tested and to the test chamber during a leak test of an object according to the proposed method;

[0054] - [Fig.3], referenced [Fig.3], is a flowchart representing the steps of the leak detection method according to the invention.

[0055] [Fig.l] is a very schematic representation of a leak detection system according to an embodiment of the invention in a particular example of application, in which the object to be tested is a package having a flexible (soft) and expandable wall. The object which is hermetically sealed can therefore expand under internal pressure, the deformation being illustrated very schematically by a broken line.

[0056] Said leak detection system 1 thus comprises:

[0057] - an enclosure 10 delimiting a test chamber 101 capable of accommodating an element or object to be tested 20, here the flexible packaging (very schematically represented);

[0058] - a first pressurizing device 102 capable of varying the pressure in test chamber 101;

[0059] - a second pressurizing device 202 capable of varying the pressure in the object to be tested 20;

[0060] - a first module for measuring at least one physical quantity relating to a leak level, said first measurement module comprising in this embodiment a first pressure sensor 103 and a first air connection connecting said enclosure 10 to said first pressure sensor 103,

[0061] - a second module for measuring at least one physical quantity relating to a leak level, said second measuring module here comprising a second pressure sensor 203 and a second air connection connecting the internal volume 201 of the element to be tested 20 to said second pressure sensor 203, and

[0062] - an electronic entity 30, such as an electronic circuit, connected to the different pressure sensors 103, 203 and configured to retrieve the pressure values measured by these sensors.

[0063] The leak detection system 1 is thus capable of detecting a leak in the object to be tested based on the measurements of the first and second pressures.

[0064] The air leak testing method for this type of part involves synchronously testing the interior of the part under test and the sealed chamber outside the part under test in order to identify a true leak, and differentiate it from the effects of expansion of the part, through the use of two different absolute pressures inside and outside the flexible part.

[0065] Alternatively or additionally, the leak test may be performed by measuring air flow rate. In this case, the measurement sensors may each be a flow meter. Thus, said first measurement module may comprise a first flow rate, or mass flow rate, sensor 103' connecting the first pressurizing device 102 capable of varying the pressure in the test chamber 101, and the second measurement module may comprise a second flow rate, or mass flow rate, sensor 203' connecting the second pressurizing device 202 and the object to be tested 20. The electronic entity 30 is connected to the different flow sensors 103, 203 and configured to recover the mass flow values measured by these sensors.

[0066] The leak detection system 1 is thus capable of detecting a leak in the object to be tested based on the measurements of the first and second mass flow rates.

[0067] The electronic entity 30 is configured to trigger, in a synchronized manner and for a defined period of time, the pressurization in the test chamber 101 and the internal volume 201 of the object to be tested. In other words, the pressurization time of the test chamber 101 is equal to the pressurization time of the object to be tested 102.

[0068] During a test or control phase, the electronic entity is configured to process first and second leak levels Fh F2 measured in a synchronized manner over the same test time interval ttest, respectively by the first and second pressure sensors 103, 203 or the first and second flow rate sensors 103', 203'.

[0069] The first pressurizing device 102 via an air connection makes it possible to vary the pressure in the enclosure 101 and to establish a test pressure Pi there (indirect method). This first pressurizing device 102 may be an air compressor which pressurizes the enclosure 101 or an air reserve in which the pressure is identical to the pressure in the enclosure 101.

[0070] The second pressurizing device 202, via an air connection, makes it possible to vary the pressure in the internal volume 201 of the element to be tested 20 and to establish a test pressure P2 there (direct method). This second pressurizing device 202 may be an air compressor which pressurizes the internal volume 201 or an air reserve in which the pressure is identical to the pressure of the internal volume 201.

[0071] First and second pressurizing devices 102, 202 are devices configured to pressurize or depressurize (or “vacuumize”) the internal volumes of the test chamber and of the object whose leaktightness is to be tested.

[0072] The first and second pressurizing devices 102, 202 may comprise a pneumatic circuit comprising in particular a pump (or a compressor), filling and / or emptying valves, a connection with a pressurized air inlet, pressure sensors, etc. The elements of the pneumatic circuit are connected to each other via suitable conduits.

[0073] The first and second pressurizing devices 102, 202 are configured to generate a relative pressure ranging from -x to y bars, or an absolute pressure ranging from 0 mbar absolute to 500 bars absolute depending on the applications...

[0074] The values of the test pressures are distinct and depend on the object to be tested. The test pressure P2 can be equal to 0 mbar (i.e. absolute vacuum) and the test pressure Pi can be equal to 1 mbar absolute, for example.

[0075] Other values are possible.

[0076] In the example described, the test pressure P2 is greater than the test pressure P2.

[0077] However, in a variant, the test pressure Pi may be greater than the pressure P2 test.

[0078] The ratio between the test pressure Pi and the test pressure P2, or vice versa, is preferably greater than or equal to 2.

[0079] The pressure difference between the test pressure Pi and the test pressure P2, or vice versa, is preferably greater than or equal to 0.01 bar.

[0080] The air connections of the leak detection system 1 take the form of conduits.

[0081] The first and second pressure sensors 103, 203 are preferably differential pressure sensors.

[0082] The first and second flow sensors 103', 203' are preferably flow meters.

[0083] It will be noted that a differential pressure sensor is, for example, a sensor comprising a membrane where each face of the membrane is exposed to a pressure, the displacement of the membrane (measured, for example, by capacitive effect) making it possible to measure the pressure difference on each side of the membrane.

[0084] In a variant, the pressure sensors are absolute pressure sensors.

[0085] The electronic entity 30 can be configured to check during the test phases, in particular the filling and emptying of the test chamber 101 and the internal volume 201, that the pressure difference between the two sides of the object to be tested 20 does not exceed a maximum threshold value. This check can be implemented when the parts to be tested are fragile and are likely to be damaged by excessively high differential pressure.

[0086] When this difference exceeds the maximum threshold value, said electronic entity 30 can be configured to reestablish a pressure difference lower than the maximum threshold value and / or emit an alarm (visual and / or audible for example). The electronic entity 30 manages the opening and closing of different valves accordingly. Filling and emptying can thus be carried out by ramps

[0087] In order to limit environmental influences during leak detection, said enclosure 10 may be made of a material having thermal conductivity less than 0.05 Wm '.K 'at 20°C, preferably less than 0.03 Wm '.K 'at 20°C, and even more advantageously less than 0.01 Wm *.K1 at 20°C.

[0088] Said leak detection system 1 makes it possible to test an object to be tested 20 positioned in the hermetically sealed (watertight) test chamber 101 in order to detect whether the object has an opening or a hole, i.e. a leak.

[0089] Thus, when it is desired to check the tightness of an object, such as packaging, said leak detection system 1 carries out the following method 100, the main steps of which are illustrated in [Fig. 3] within the leak detection system 1:

[0090] - pressurization or pressurization (step Si) of the volume of the test chamber 101 via the pressurizing device 102 during a pressurizing time period; the test chamber 101 is subjected to an absolute test pressure Pi, which is for example equal to 45 mbar;

[0091] - in a synchronized manner, and during the same pressurization time period, a pressurization or pressurization (step S'i) of the interior volume 201 of the object to be tested 20 via the pressurization device 202; the interior volume 201 is subjected to an absolute test pressure P2 which is for example equal to 10 mbar, i.e. a ratio of 4.5 between absolute test pressure Pi and absolute test pressure P2.

[0092] In the particular embodiment where flow sensors 103', 203' are implemented in the system of the invention, when the test pressure P2 in the object to be tested 20 is reached, the air supply is cut off and the pressure is the same in the second pressurizing device 202 (taking the form of an enclosure) and the object to be tested 20. In parallel, when the test pressure Pi in the test chamber 101 is reached, the air supply is cut off and the pressure is the same in the first pressurizing device 102 (taking the form of an enclosure) and the test chamber 101.A leak on the object to be tested or a deformation of its flexible wall creates a pressure variation and consequently a leakage flow rate through the first flow sensor 103' between the first pressurizing device 102 and the test chamber 101, and through the second flow sensor 203' between the second pressurizing device 202 and the object to be tested 20.

[0093] A first leak level Fi is then determined during a test period in the test chamber 101, this determination being carried out by measuring a physical quantity as a function of time, such as a variation in the pressure in the test chamber via the first pressure sensor 103 or the first flow sensor 103'.

[0094] Synchronously and during the same predetermined test time period, a second leakage level F2 is further determined in the test object 20. As previously, this determination is carried out by measuring a physical quantity as a function of time, such as a variation in the pressure in the object to be tested 20 via the second pressure sensor 203 or the second flow sensor 203'.

[0095] A real leak level F is then determined on the object to be tested 20 as a function of the first and second measured leak levels FB F2, and of the first and second test pressures Pb P2.

[0096] This determination is based on the observation that the change in shape of the part creates a pressure change which is different inside and outside the tested part if the absolute pressures are different in the two cavities, the difference in pressure changes being directly proportional to the absolute pressures in each volume. Indeed, according to the Boyle-Mariotte law, at constant temperature and for a given quantity of gas, the product of the pressure P by the volume V is constant.

[0097] In a particular implementation, said electronic entity 30 determines the actual leakage value F between the object to be tested and the test chamber in the following manner.

[0098] The absolute test pressure Pabshi is considered in the high pressure cavity (the test chamber or the interior volume of the part to be tested), and the absolute test pressure Pybsio in the low pressure cavity (the interior volume of the part to be tested or the test chamber respectively).

[0099] The value of the leak Fio measured on the low pressure side and the value of the leak Fhimeased on the high pressure side are also considered.

[0100] Fexp is considered to be the “false leak” due to the expansion of the object to be tested on the low pressure side.

[0101] By measuring the pressure changes on each side, we obtain a system of two equations with two unknowns, the two unknowns being the real leak Freai and the "false leak" Fexp due to expansion, namely:

[0102] Fio = Freai + Fexp and Fhi = Freai + ((£«^i) Fexp), the leakage values being in Pabslo value absolute.

[0103] Now, since Fexp = Fio - Freai, then Fhi= Freai + ( (£2^ ) (Fio - Freai)). Pabslo

[0104] From these two equations we extract the real leakage level Freai between the internal volume of the object to be tested and the internal volume of the chamber which is calculated in the following way by the electronic entity 30:

[0105] ^F^Fhi Freal - — Pabshi * Pabslo ~

[0106] We therefore understand that if there is no leak in the object to be tested then Freai is equal to 0.

[0107] Depending on the value of the Freab leak and according to the required threshold, the electronic entity 30 determines whether or not the part to be tested has a defect or an opening, and indicates the conformity or not of the tested object.

[0108] This approach makes it possible to differentiate the measurement of the actual leakage level F between the internal volume of the object and the test chamber from the effects linked to the expansion of the object to be tested.

[0109] The electronic entity 30 is therefore configured to detect a possible leak which is no longer influenced by the volume expansion of the flexible object to be tested, which, it will be recalled, creates a change in pressure which is not a leak and which hinders the leak test by change in pressure or measurement of air flow rate.

[0110] The advantage of this method is that it can reliably distinguish a pressure variation linked to a leak, even a very small one, in the part from a variation linked to an expansion of the part.

[0111] It is therefore possible to detect very small defects or openings in flexible parts or parts having at least one flexible wall or to detect defects more quickly in a given production time.

[0112] The table below summarizes the leak values (in cm3 / min) measured and the actual leak value calculated (in cm3 / min) during a leak test, according to the proposed method, of an object that is known to be perfectly leaktight.

[0113] During this test, the absolute high pressure is 1500 mbar and the absolute low pressure is 500 mbar. High pressure side leak value Read low pressure side leak value Calculated leak 3.5 0.962 -0.307 2.1 0.504 -0.294 2.01 0.497 -0.2595 1.97 0.427 -0.3445 1.92 0.427 -0.3195 1.88 0.714 0.131 1.7 0.675 0.1625 1.7 0.605 0.0575 1.7 0.551 -0.0235 1.44 0.489 0.0135

[0114] After a predetermined test time, it appears that the calculated actual leakage value is indeed approaching zero. It should be noted that the calculated leakage is always smaller than the leakage value on the high pressure and low pressure side (expansion eliminated). The initial calculated leakage value of -0.307 sccm shows that other stabilizing effects such as adiabatic decompression were not eliminated or deliberately reduced.

[0115] The table below summarizes the leak values (in cm3 / min) measured and the actual leak value calculated (in cm3 / min) during a leak test according to the proposed method of an object presenting a leak which was quantified before the test and which presents a value of 23.2 cm3 / min.

[0116] During this test, the absolute high pressure is 1013 mbar and the absolute low pressure is 500 mbar. High pressure side leakage value Read low pressure side leakage value Calculated leakage 28.76 25.76 22.83602339 29.72 26.01 22.39401559 28.46 25.42 22.45703704 28.06 25.32 22.6494347 27.54 25.06 22.642846 27.28 24.96 22.69879142 26.97 24.94 22.9614425 26.71 24.92 23.17536062 26.58 24.88 23.22307992 26.45 24.79 23.17206628

[0117] It appears that the calculated actual leak value actually has a value different from zero, around 23.2 cm3 / min.

[0118] These two tests made it possible to validate the formula for calculating the actual leak presented above and the measurement method of the invention.

[0119] [Fig.2] is a graph representing in the form of curves these two examples of variations in leak mass flow rates (in "standard cubic centimeters per minute" or "sccm" in English, i.e. in cm3 / min) in a volume relative to the object to be tested and to the test chamber during a leak test of an object according to the proposed method.

[0120] The two upper curves of the graph illustrate the variations of the leakage rates on the high pressure Pabshi and low pressure Pabsio sides when the test object has a leak. In this case, the leak rates on the side of the object to be tested and on the side of the enclosure tend to converge towards the same non-zero value after a given test time. In other words, in the presence of a leak, a flow rate persists and has a value substantially equal to 23 cm3 / min.

[0121] The two lower curves of the graph illustrate the variations in the leak rates on the Pabshi high pressure side and the Pabsio low pressure side in the absence of leakage in the object to be tested, these variations being solely due to the deformations of the flexible object to be tested. In this case, the leak rates on the side of the object to be tested and on the side of the enclosure tend to converge much more quickly towards the same zero value after a given test time. In other words, in the absence of leakage, the flow rate measurement is reduced until it becomes zero.

[0122] It will be noted that some of the steps of the method 100 are part of an airflow management method for leak detection which can be split into four phases: a phase of filling or pressurizing the volume of the test chamber and the object to be tested with compressed air, the pressure increases to a desired test pressure value Piet P2 respectively; a stabilization step, after having put the two volumes under pressure, it is waited for them to return to thermal equilibrium and almost to mechanical equilibrium (there may still be mechanical expansion), so that phenomena do not disturb the measurement of the leak (it will be noted that the filling and stabilization phases correspond to the pressurization steps Si, S'i;a test or control phase, during which the pressure (or flow rate) variations in the pressurized volumes are measured for a predetermined test time ttest and the possible presence of a leak F between the interior volume of the object and the chamber is determined on the basis of the pressure (or flow rate) variations in the volumes measured by the first and second sensors and the test pressures (the test phase therefore corresponds to steps S2, S'2 and S3 above) - the test result is given at the end of this phase by the electronic entity; an emptying phase, during which the pressurized volumes are brought back to atmospheric pressure. At the end of this phase, the test is finished. ;

[0123] The method according to the invention synchronizes the two direct and indirect tests with equal filling and stabilization times, and equal test times.

[0124] The different steps and phases described above are controlled by the electronic entity 30 which manages the opening and closing of different valves accordingly.

Claims

Claims

1. Leak detection system (1) for checking the tightness of an object (20) having at least one expandable flexible wall, said system comprising: - a sealed test chamber (101) configured to receive / accommodate the object (20) to be tested; - a device for pressurizing the interior volume of the test chamber (101) to a first test pressure value PI; - a device for pressurizing the interior volume of the object to be tested (20) to a second test pressure value P2, distinct from the first test pressure value Pi; - a first sensor (103) for measuring a first leak level Fi in the test chamber (101), this determination being carried out by measuring a physical quantity representative of the leak level as a function of time;- a second measuring sensor (203) of a second leak level F2 of the object to be tested (20), this determination being carried out by measuring a physical quantity representative of the leak level as a function of time; - an electronic entity (30) configured to determine an actual leak Freai in the object to be tested (20) as a function of the first and second test pressure values PH P2, and the first and second leak levels FB F2 measured in a synchronized manner over the same test time interval ttest, respectively by the first and second measuring sensors (103, 203; 103', 203').;

2. System according to claim 1, characterized in that: - the first measuring sensor (103) is a pressure sensor configured to measure pressure variations representative of the leakage level of the pressurized volume of the object to be tested; - the second measuring sensor (203) is a pressure sensor configured to measure pressure variations representative of the leakage level of the pressurized volume of the test chamber; - the electronic entity being configured to determine an actual leak Freai in the object to be tested as a function of the first and second test pressure values Pb P2, the pressure variations AP2 in the pressurized interior volume of the object to be tested, and the pressure variations APi in the pressurized interior volume pressure of the test chamber, said variations APi, AP2 being measured in a synchronized manner over the same test time interval ttest, respectively by the first and second pressure sensors.

3. System according to claim 1, characterized in that: - the first measuring sensor (103') is a flow meter configured to measure the mass flow rate variations representative of the leakage level of the pressurized volume of the object to be tested; - the second measuring sensor is a flow meter configured to measure the mass flow rate variations representative of the leakage level of the pressurized volume of the test chamber; - the electronic entity being configured to determine an actual leak Freai in the object to be tested as a function of the first and second test pressure values Pb P2, the mass flow rate variations in the pressurized interior volume of the object to be tested, and the mass flow rate variations in the pressurized interior volume of the test chamber, said mass flow rate variations being measured over a test time interval ttest, respectively by the first and second measuring sensors.

4. System according to one of claims 1 to 3, characterized in that the values of the test pressures (Pb P2) are absolute pressures.

5. System according to claim 4, characterized in that the ratio between the absolute test pressure values (Pb P2) is at least equal to 1.

1.

6. System according to claim 5, characterized in that the difference between the values of the absolute test pressures (PB P2) is at least equal to 0.005 bar.

7. System according to one of claims 4 to 6, characterized in that the electronic entity (30) determines the actual leak level Freaitre the internal volume of the object to be tested and the internal volume of the test chamber as a function of the highest absolute test pressure (Pabshi ) and the lowest absolute test pressure (Pabsio) between Pi and P2, the leak level Fio measured on the lower pressure side, i.e. in the part to be tested or in the test chamber, and the leak level Fhi measured on the lower pressure side, i.e. in the test chamber or in the part to be tested respectively.

8. System according to any one of the preceding claims, characterized in that the first measuring sensor and / or the second measuring sensor are differential measuring sensors.

9. System according to any one of the preceding claims, characterized in that the electronic entity (30) is configured to control the pressure difference between the interior volume of the object to be tested and the exterior of the object to be tested so that this pressure difference does not exceed a predetermined threshold value.

10. Method (100) for leak detection implemented within a leak detection system (1) according to one of claims 1 to 9, said method (100) comprising the following steps: - establishing a first test pressure (Si) in the test chamber by a pressurizing device during a pressurizing time period; - establishing in a synchronized manner and during the same time period a second test pressure (S'i), different from the first pressure, in the object to be tested by a pressurizing device; - determining over a test time interval a first leak level (S2) in the test chamber by measuring a physical quantity as a function of time by means of a first measuring sensor, such as a pressure sensor;- determining in a synchronized manner and over the same test time interval a second leak level (S'2) in the object to be tested by measuring a physical quantity as a function of time by means of a second measuring sensor, such as a pressure sensor; - determining the actual leak level of the object to be tested (S3) as a function of the first and second leak levels measured over a predetermined test time interval ttest, and of the first and second test pressure values.;

11. Method (100) for detecting leaks according to claim 10, characterized in that the steps of pressurizing (SI, S' 1) the test chamber and the object to be tested each comprise a filling phase up to the desired test pressure and a stabilization phase.

12. A method (100) for detecting leaks according to claim 10 or 11, characterized in that the pressure difference between the interior of the object to be tested and the exterior of the object to be tested is controlled so as not to exceed a predetermined threshold value.