LEAK DETECTION SYSTEM USING SYNCHRONIZED DIRECT AND INDIRECT METHODS
A synchronized leak detection system using differential pressure sensors addresses the challenge of distinguishing leaks from wall expansions in flexible objects, improving sensitivity and repeatability in leak detection.
Patent Information
- Application Number
- FR2024000828
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2024-01-29
- Publication Date
- 2025-12-26
- Estimated Expiration
- 2044-01-29
AI Technical Summary
Existing leak detection methods struggle to accurately measure small leaks in objects with flexible walls due to pressure variations caused by wall deformation, making it difficult to distinguish between leaks and wall expansions.
A synchronized leak detection system that combines direct and indirect pressure measurements at different pressures to differentiate between actual leaks and wall expansions, using differential pressure sensors to calculate the actual leakage level.
The system enhances leak detection sensitivity and repeatability by accurately distinguishing between leaks and wall expansions, allowing for faster and more reliable detection of small leaks in flexible objects.
Abstract
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 checking the tightness of an object, more particularly based on the measurement of a physical quantity, such as a pressure or a flow rate, relative to a level of leakage.
[0002] There are different systems and methods for detecting leaks.
[0003] When leak detection is desired by pressure variation, the object to be tested, whose level of sealing is to be checked, undergoes a controlled pressure variation. This means that a known pressure variation is applied to an internal volume of the object (the so-called direct method) or to a closed volume surrounding the object (the so-called indirect method). Then, after a predetermined time, the pressure is measured again in the volume that underwent the pressure variation. 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 allow the determination of a leakage level relative to the object. Indeed, the pressure variation per unit of time can be related to a leakage level by the following mathematical relationship:
[0005] where 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 is the time interval (in seconds) of the measured pressure variation AP, V is the relevant volume to be considered (for example the internal volume of the object) generally expressed in cubic centimeters (cm3), and k is a multiplicative constant (in Pa1). Thus, regardless of the object or sub-element of the object, it is possible to check if it has leaks and to determine its level of sealing.
[0006] It should be noted that the leak can be expressed in a different way than by pressure variation over a given period of time, for example in the form of a mass flow rate.
[0007] The formula that links the leakage 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 if 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 considerably depending on the object being tested, its volume, shape, function, etc.
[0010] However, when the level of leakage that one seeks to determine is relatively small in relation to the volume of the object to be tested, the intrinsic parameters of the object to be tested may make it difficult to measure the variation in pressure (or flow rate) and / or its repeatability. Indeed, in the case of objects to be tested with flexible walls, the deformations of the wall when a pressure variation is made on the internal volume of the object, for example, can lead to pressure variations of an order of magnitude roughly equal to the level of the leaks that we are trying to detect.
[0011] It is therefore particularly difficult to obtain reliable leakage measurements and to distinguish a pressure variation related to a leak in the part from a variation related to an expansion of the part.
[0012] Research and tests were therefore carried out by the holder to propose a method and a leak detection system with improved sensitivity and allowing better repeatability in leak detection, while improving the level of detectability of said leaks.
[0013] The invention is thus a new leak detection system for checking 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 internal volume of the test chamber to a second test pressure value, distinct from the first pressure value; - a first sensor to measure a first level of leakage in the object to be tested, this determination being carried out by measuring a physical quantity such as pressure or flow rate, as a function of time;
[0016] - a second sensor for measuring a second level of leakage in the chamber of 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 leakage F in the object to be tested based 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, using pressure change or air flow measurement, to check the tightness of an object to be tested, including at less a wall is flexible and expandable, the system being configured to pressurize, in a synchronized manner and at distinct pressures, an internal volume of the object to be tested (called direct method) and the test chamber surrounding said object (called 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 with 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 one 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 at test based on the first and second test pressure values, the pressure variations in the pressurized internal volume of the object to be tested, and the pressure variations in the pressurized internal 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 testing in a synchronized manner the inside of the part being tested and the sealed chamber outside the part being tested 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 embodiment:
[0028] - the first measuring sensor is a flow meter configured to measure the variations in mass flow rate 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 variations in mass flow rate 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 at test based on the first and second test pressure values, the mass flow rate variations in the pressurized internal volume of the object to be tested, and the mass flow rate variations in the pressurized internal 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, one can measure a flow rate corresponding to a leak. The leak test then consists of synchronously testing the inside of the part being tested and the sealed chamber outside the part being tested 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 one possible characteristic, the test pressure values are absolute pressures.
[0033] According to another possible characteristic, the ratio between the absolute pressure test values is at least equal to 1.1.
[0034] In one example of 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 one 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 feature, 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 side of the lowest pressure, i.e. in the part to be tested or in the test chamber, and the leakage level measured on the side of the lowest pressure, i.e. in the test chamber or in the part to be tested respectively.
[0037] According to one possible characteristic, the first measuring sensor and / or the second measuring sensor are differential measuring sensors.
[0038] The use of differential pressure sensors has the advantages of being able to measure smaller pressure variations and of eliminating measurement errors related to the mechanical and / or thermal behavior of the object being tested.
[0039] According to another possible feature, the electronic entity is configured to control the pressure difference between the internal volume of the object to be tested and the outside of the object to be tested so that this pressure difference does not exceed a predetermined threshold value.
[0040] The invention also relates to a leak detection method implemented within a leak detection system as described above, said method comprising the following steps:
[0041] - establish a first test pressure in the test chamber by means of a device pressurization during a pressurization period;
[0042] - to establish, synchronously and during the same period of time, a second test pressure, different from the first pressure, in the object to be tested by a pressurization device;
[0043] - determine over a test time interval a first level of leakage 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] - to determine synchronously and over the same test time interval a second level of leakage 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 as a function of the first and
[0046] second leakage 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 testing times.
[0049] According to one possible feature, the steps of pressurizing the test chamber and the object to be tested each include a filling phase up to the desired test pressure and a stabilization phase.
[0050] According to another possible feature, the pressure difference between the inside of the object to be tested and the outside 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 objects, details, features and advantages thereof will become more apparent from the following description of particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings, in which:
[0052] - the [Fig.1], referenced [Fig.1], is a very schematic representation of a system leak detection according to an embodiment of the invention;
[0053] - Figure 2, referenced as [Fig.2], is a graph representing in the form of curves two examples of variations in mass flow rate of leakage 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] - the [Fig.3], referenced [Fig.3], is a flowchart representing the steps of the leak detection method according to the invention.
[0055] Figure 1 is a highly schematic representation of a leak detection system according to an embodiment of the invention in a particular application, in which the object to be tested is a package having a flexible and expandable wall. The hermetically sealed object can therefore expand under internal pressure, the deformation being illustrated very schematically by a dashed line.
[0056] Said leak detection system 1 comprises as follows:
[0057] - an enclosure 10 delimiting a test chamber 101 suitable for housing an element or object to be tested 20, here the flexible packaging (very schematically represented);
[0058] - a first pressurization device 102 capable of varying the pressure in test chamber 101;
[0059] - a second pressurization device 202 capable of varying the pressure in the object to be tested 20;
[0060] - a first measurement module for at least one physical quantity related to a leakage level, said first measuring module comprising in this embodiment a first pressure sensor 103 and a first air connection linking said enclosure 10 to said first pressure sensor 103,
[0061] - a second measurement module for at least one physical quantity relating to a leakage level, said second measuring module comprising here a second pressure sensor 203 and a second air connection linking 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 able to detect a leak in the object to be tested based on the measurements of the first and second pressures.
[0064] The air leak test method for this type of part consists of synchronously testing the inside of the part being tested and the sealed chamber outside the part being tested in order to identify a real leak, and to differentiate it from the effects of expansion of the part, by using two different absolute pressures inside and outside the flexible part.
[0065] Alternatively or in addition, the leak test can be performed by measuring air flow. In this case, the measuring sensors can each be a flow meter. Thus, the first measuring module can include a first flow sensor, or mass flow sensor, 103' connecting to the first pressurization device 102 capable of varying the pressure in the test chamber 101, and the second measuring module can include a second flow sensor, or mass flow sensor, 203' connecting the second pressurization device 202 and the object to be tested 20. The electronic entity 30 is connected to the various flow sensors 103, 203 and configured to retrieve the mass flow values measured by these sensors.
[0066] The leak detection system 1 is thus able to detect a leak in the object to be tested based on the measurements of the first and second mass flow rates.
[0067] The electronic unit 30 is configured to trigger, synchronously and within a defined time period, the pressurization of 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 synchronously over the same test time interval ttest, respectively by the first and second pressure sensors 103, 203 or the first and second flow sensors 103', 203'.
[0069] The first pressurization device 102, via an air connection, allows the pressure in the chamber 101 to be varied and a test pressure Pi to be established there (indirect method). This first pressurization device 102 can be an air compressor that pressurizes the chamber 101 or an air reservoir in which the pressure is identical to the pressure in the chamber 101.
[0070] The second pressurization device 202, via an air connection, allows the pressure in the internal volume 201 of the test element 20 to be varied and a test pressure P2 to be established there (direct method). This second pressurization device 202 can be an air compressor that pressurizes the internal volume 201 or an air reservoir in which the pressure is identical to the pressure of the internal volume 201.
[0071] The first and second pressurization devices 102, 202 are devices configured to pressurize or depressurize (or "vacuum") the internal volumes of the test chamber and of the object whose leak-tightness is to be tested.
[0072] The first and second pressurization devices 102, 202 may include a pneumatic circuit comprising, in particular, a pump (or compressor), filling and / or emptying valves, a connection with a pressurized air supply, pressure sensors, etc. The elements of the pneumatic circuit are connected to each other by means of suitable conduits.
[0073] The first and second pressurization 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 application...
[0074] The test pressure values are distinct and depend on the object being 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 one embodiment, 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 ducts.
[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 flowmeters.
[0083] It should 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) allowing the pressure difference to be measured on each side of the membrane.
[0084] In one embodiment, the pressure sensors are absolute pressure sensors.
[0085] The electronic unit 30 can be configured to monitor, during the test phases, particularly 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 under test 20 does not exceed a maximum threshold value. This monitoring can be implemented when the parts under test are fragile and are likely to be damaged by excessive differential pressure.
[0086] When this difference exceeds the maximum threshold value, the electronic unit 30 can be configured to restore a pressure difference below the maximum threshold value and / or issue an alarm (visual and / or audible, for example). The electronic unit 30 manages the opening and closing of various valves accordingly. Filling and emptying can thus be carried out via 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 performs 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 pressurization device 102 during a pressurization time period; the test chamber 101 is subjected to an absolute test pressure Pi, which is for example equal to 45 mbars;
[0091] - in a synchronized manner, and during the same pressurization time period, a pressurization or pressurization (step S'i) of the internal volume 201 of the object to be tested 20 by means of the pressurization device 202; the internal volume 201 is subjected to an absolute test pressure P2 which is for example equal to 10 mbars, 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 pressurization device 202 (taking the form of a chamber) 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 pressurization device 102 (taking the form of a chamber) 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 through the first flow sensor 103' between the first pressurization device 102 and the test chamber 101, and through the second flow sensor 203' between the second pressurization device 202 and the object to be tested 20.
[0093] A first level of leakage Fidans in the test chamber 101 is then determined during a test period, this determination being carried out by measuring a physical quantity as a function of time, such as a variation in 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 period, a second leakage level F2 in the object to be tested 20 is also determined. As Previously, this determination was carried out by measuring a physical quantity as a function of time, such as a variation in pressure in the object to be tested 20 via the second pressure sensor 203 or the second flow sensor 203'.
[0095] A real leakage level F is then determined on the object to be tested 20 as a function of the first and second leakage levels FB F2 measured, and the first and second test pressures Pb P2.
[0096] This determination is based on the observation that a change in the shape of the part creates a pressure change that differs 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 Boyle's Law, at constant temperature and for a given quantity of gas, the product of the pressure P and 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] We consider the absolute test pressure Pabshi in the cavity under high pressure (the test chamber or the internal volume of the part to be tested), and the absolute test pressure Pybsio in the cavity under low pressure (the internal volume of the part to be tested or the test chamber respectively).
[0099] We also consider the value of the leak Fio measured on the low pressure side and the value of the leak Fhim measured on the high pressure side.
[0100] Fexp is considered 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 actual leakage Freai and the "false leakage" 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)). Pablo
[0104] From these two equations, we extract the actual leakage level Freai between the internal volume of the object to be tested and the internal volume of the chamber, which is calculated as follows by the electronic entity 30:
[0105] ^F^Fhi Freal - — Pabshi * Pablo ~
[0106] It is therefore understood 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 leakage and according to the required threshold, the electronic entity 30 determines whether the part to be tested has a defect or an opening, and indicates whether or not the tested object conforms.
[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 related to the expansion of the object to be tested.
[0109] The electronic entity 30 is therefore configured to detect a possible leak that is no longer influenced by the volume expansion of the flexible object to be tested, which, it should be recalled, creates a pressure change that is not a leak and which hinders the leak test by pressure change or air flow measurement.
[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 faster in a given production time.
[0112] The table below summarizes the measured leakage values (in cm3 / min) and the calculated actual leakage value (in cm3 / min) during a leak test, according to the proposed method, of an object known to be perfectly sealed.
[0113] During this test, the absolute high pressure is 1500 mbars and the absolute low pressure is 500 mbars. High-pressure side leakage value Low-pressure side leakage value Calculated leakage 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 leak value does indeed approach zero. It should be noted that the calculated leak is always smaller than the leak value on both the high-pressure and low-pressure sides (expansion eliminated). The initial calculated leak value of -0.307 sccm shows that other stabilizing effects, such as adiabatic decompression, were not eliminated or intentionally reduced.
[0115] The table below summarizes the measured leakage values (in cm3 / min) and the calculated actual leakage value (in cm3 / min) during a leak test according to the proposed method of an object with a leak that was quantified before the test and which has a value of 23.2 cm3 / min.
[0116] During this test, the absolute high pressure is 1013 mbars and the absolute low pressure is 500 mbars. High-pressure side leakage value 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 has a value that is indeed different from zero, around 23.2 cm3 / min.
[0118] These two tests made it possible to validate the formula for calculating the actual leakage 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 mass flow rates of leakage (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 in leakage rates on the high-pressure side Pabshi and the low-pressure side Pabsio when the object to be tested presents a leak. In this scenario, the leakage rates on the side of the object being tested and on the side of the enclosure tend to converge towards the same non-zero value after a certain testing time. In other words, in the presence of a leak, a flow rate persists and has a value approximately equal to 23 cm³ / min.
[0121] The two lower curves of the graph illustrate the variations in leakage rates on the high-pressure side (Pabshi) and the low-pressure side (Pabsio) in the absence of a leak in the object under test. These variations are solely due to the deformations of the flexible object under test. In this scenario, the leakage rates on the side of the object under test and on the side of the enclosure tend to converge much more rapidly towards the same zero value after a certain test time. In other words, in the absence of a leak, the flow rate measurement decreases until it becomes zero.
[0122] It should be noted that some of the steps of method 100 are part of an air handling method for leak detection which can be divided 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 up to a desired test pressure value Piet P2 respectively; a stabilization step, after pressurizing the two volumes, we wait for them to return to thermal equilibrium and almost to mechanical equilibrium (there may still be some mechanical expansion), so that phenomena do not disrupt the leak measurement (it should be noted that the filling and stabilization phases correspond to the pressurization steps Si, S'i;a test or control phase, during which pressure (or flow rate) variations are measured in the pressurized volumes for a predetermined test time, and the possible presence of a leak F between the object's internal volume and the chamber is determined based on 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 unit; a depressurization phase, during which the pressurized volumes are returned to atmospheric pressure. At the end of this phase, the test is complete.
[0123] The method according to the invention synchronizes the two direct and indirect tests with equal filling and stabilization times, and equal testing times.
[0124] The various steps and phases described above are controlled by the electronic entity 30 which manages the opening and closing of different valves accordingly.
Claims
Demands
1. Leak detection system (1) for checking the tightness of an object (20) having at least one expandable flexible wall, said system comprising: - a leak-proof test chamber (101) configured to receive / accommodate the object (20) to be tested; - a device for pressurizing the internal volume of the test chamber (101) to a first test pressure value PI; - a device for pressurizing the internal 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 for measuring (103) 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 synchronously over the same test time interval ttest, respectively by the first and second measuring sensors (103, 203; 103', 203').
2. The 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 under test; - 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 unit being configured to determine an actual leakage Freaidans in the object under test as a function of the first and second test pressure values Pb P2, the pressure variations AP2 in the pressurized internal volume of the object under test, and the pressure variations APi in the pressurized internal volume. pressure of the test chamber, said variations APi, AP2 being measured synchronously 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 flowmeter configured to measure the mass flow rate variations representative of the leak level of the pressurized volume of the object to be tested; - the second measuring sensor is a flowmeter configured to measure the mass flow rate variations representative of the leak level of the pressurized volume of the test chamber; - the electronic entity being configured to determine an actual leak Freaidans 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 internal volume of the object to be tested, and the mass flow rate variations in the pressurized internal 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 any one of claims 1 to 3, characterized in that the test pressure values (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 any one of claims 4 to 6, characterized in that the electronic entity (30) determines the actual leakage level Freaientre 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 leakage level Fio measured on the side of the lowest pressure, i.e. in the part to be tested or in the test chamber, and the leakage level Fhi measured on the side of the lowest pressure, 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 internal volume of the object to be tested and the outside of the object to be tested so that this pressure difference does not exceed a predetermined threshold value.
10. A leak detection method (100) implemented within a leak detection system (1) according to any one of claims 1 to 9, said method (100) comprising the following steps: - establishing a first test pressure (Si) in the test chamber by means of a pressurization device during a pressurization time period; - establishing synchronously and during the same time period a second test pressure (S'i), different from the first pressure, in the object to be tested by means of a pressurization device; - determining over a test time interval a first leakage 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;- to determine, synchronously 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 using a second measuring sensor, such as a pressure sensor; - to determine 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 the first and second test pressure values.
11. Leak detection method (100) according to claim 10, characterized in that the pressurization steps (SI, S' 1) of the test chamber and the object to be tested each include a filling phase up to the desired test pressure and a stabilization phase.
12. A leak detection method (100) according to claim 10 or 11, characterized in that the pressure difference between the inside of the object to be tested and the outside of the object to be tested is controlled so as not to exceed a predetermined threshold value.