Patent Application
20210048365
This disclosure pertains to determine the integrity of closed containers by exposing the container to a decreased pressure and performing optical measurements of gas leakage from the inside of the container. The measurements include placing the container in an environment where the pressure is lower than inside the container so that gas from the inside of the container flows out through any potential leak. An optical gas measurement is performed outside the container, for detection of gas leakage. Especially, the disclosure relates to non-destructive leak testing of containers such as packages, bags, trays, bottles, jars, vials.
Sealed containers are used in many fields of, e.g., packaging of food, pharmaceuticals, chemicals, etc. Tight containers are important to, e.g., prevent the content from leaking out; to prevent atmospheric gases or moisture to enter the container; and to prevent any pre-filled gas composition inside the container from changing. Further, the integrity of sealed containers may be important to ensure that biological agents such as viruses or bacteria do not enter and affect the product. The integrity of sealed containers may be insufficient, e.g. by faults in, or a non-optimal sealing process, deficiencies in the barrier materials, damage during the handling, and contents or other objects trapped in welding. Verification and validation of the integrity of sealed containers is thus important in many industrial situations. Verification and validation of the integrity of sealed container may often be referred to as leak-testing or similar, and many methods for this are known in the art.
Examples of leak-testing methods include manual inspection, which can be visual inspection of seams etc, listening after sounds indicating leaks, feeling the resistance of bags, smelling etc. Manual methods are, however, time consuming and can generally not identify small leaks.
Other known methods include automated vision systems to detect anomalies, but again this may not detect small leaks, and the method is limited to certain kinds of containers.
Mechanical force testing is also used where the resistance from, e.g., a flexible bag is automatically measured. However, this method is typically not suitable for detection of small leaks, and carries the risk of damaging the container.
Another common method is to submerge a container in water or another liquid and searching for bubbles escaping the container. This is often referred to as “bubble-test”. Also this method may be relatively time consuming and cannot detect very small leaks. The method is also to some extent intrusive as some containers may be damaged by the liquid. Some container types are also not suited for this type of test, as for example carton, as gas will escape the container material itself and thus hide true leaks.
Small leaks can be detected by penetration tests using dyes. The container may then, either as a whole, or cut out sections of it, be stained with dye on one side, and dye penetrating through the container material is indicating leaks. This method is, however, destructive and time consuming. In a similar manner, trace gases such as helium or hydrogen, may be used. The container may then be pre-filled with the trace gas and sealed, where after, e.g., a mass spectrometer is used to detect escaping trace gas. Using trace gases can provide a very sensitive detection finding small leaks, but it is relatively slow, and require filling of trace gases in special test containers, meaning that it can only be used on a small sub-sample of produced containers.
Another method is to subject the container to external variations in the outside atmosphere, e.g., by placing it in a (partial) vacuum chamber, or exerting overpressure on the container with atmospheric air or other gases, or combinations of these techniques. With this method, some additional means to detect a leak of a container is required, i.e., by controlling or measuring one or more parameters that may change as consequence of the variation in outside pressure or gas composition, if a leak is present. Several such techniques are known in the art. For example, transient pressure variation in the chamber may be recorded, and its behaviour may be indicative of a leak in the sample. Examples of such techniques can be referred to as “vacuum decay”, “pressure decay”, or similar. Examples of related methods can include placing the container in a vacuum chamber and observing any leakage of product substance (e.g. EP2989435B1).
Non-intrusive optical detection of gases inside packages for quality control is disclosed in patent EP 10720151.9 (Svanberg et al.). The principle of optical detection of the gas in the headspace of packages for the purpose of indicating leaks is known in the art. This method is based on that the gas inside the package may deviate from an assumed gas composition due to interaction with the surrounding atmosphere through the leak. However, in normal atmosphere, for small leaks, it may take a very long time before there is a detectable deviation of the gas composition inside a package, which makes the method impractical in many situations.
A faster determination of container integrity, based on optical measurements of the gas composition/pressure inside a sealed container, is covered by WO 2016/156622. Here the container is subjected to a surrounding with a forced change in gas concentration/pressure, thereby inducing a faster change inside the container if a leak is present, compared to the natural alternations observed in EP 10720151.9.
Another example is where a container with significant amounts of CO2 is placed in a vacuum chamber where a CO2 sensor of type NDIR (non-dispersive infra-red) is placed. A drawback of NDIR sensors is that they are relatively slow in detecting fast concentration changes.
There are situations where none of the methods previously described in the art are suitable for detecting a leak. One such example is for inline measurements where a fast detection of small leaks is essential, hence new improved apparatus and methods for detecting leaks in such containers would be advantageous.
Accordingly, embodiments of the present disclosure preferably seek to mitigate, alleviate or eliminate one or more deficiencies, disadvantages or issues in the art, such as the above-identified, singly or in any combination by providing a system or method according to the appended patent claims for non-destructively determining the integrity of sealed containers by detection of gas leakage into an environment with lower pressure than inside the container. The sensor may be an optical sensor. The optical sensor may be based on detecting an absorption in spectra in a transmitted light signal, for example by using Tunable diode laser absorption spectroscopy (TDLAS) technology.
A method of determining the integrity of a closed container including at least one gas detectable with an optical sensor is described. The method may include placing the container in an environment with a lower absolute pressure than inside the container, for example placing a pressurized bottle in an environment at ambient pressure, or placing a container with 1 atm internal pressure in an environment, such as a chamber, with partial vacuum (<1 atm). At least one optical sensor is used to determine if the level of the at least one gas may be altered in the environment outside the container and thereby determining if the at least one gas that may potentially be leaking out from the container. The optical sensor may be based on spectroscopy, such as TDLAS.
In one aspect of the invention the container containing the at least one gas may be pressurized and the surrounding environment may be an open space at ambient pressure where at least one optical sensor may detect if the level of the at least one gas is altered and thereby determine if the container may be leaking.
In another aspect of the invention the container may be placed in an environment, such as a chamber where a partial vacuum may be applied, thereby inducing a flow of the at least one gas through potential leaks. An optical sensor, based on for example TDLAS, is in this case transmitting a light beam, such as a laser beam, through the environment, such as a chamber or through a connected volume. In some aspects of the invention different means for ensuring that the leaked gas reaches the laser beam, to be detected by the optical sensor, may be applied. These means may include, but are not limited to, fans, circulation pumps or special designs of the pressure cycle created by the vacuum pump.
Some advantages of the disclosed systems and methods compared to known systems or methods, may be that the disclosed systems and methods could be faster and more sensitive in detecting leaks, due to the fast response time and high sensitivity of the TDLAS technique. The possibility of TDLAS to transmit a free beam through an open space close to the container is also superior in order to enable a fast detection, compared to, for example, NDIR which is used in an internal semi-enclosed gas cell which may have a slow response time. Another advantage with the enclosed systems and methods may be that the fast and sensitive detection of TDLAS can enable a detection of the position of the leak on the container, either through the timing of the detected alternation of the level of the at least one gas, or by using multiple detectors and/or transmitters placed at different positions around the container.
Other advantages of the disclosed systems and methods may be related to that the technique can be non-intrusive and fast, compared to for example “bubble tests” where the container is submerged in liquid, or mass spectrometer detection which is sensitive but slow and generally require specially filling the container with trace gases, for example hydrogen or helium. TDLAS has the advantage of being able to detect gases that are commonly used or present in container headspaces, for example carbon dioxide, oxygen, water vapor or methane. The non-intrusiveness of the disclosed systems and methods is further reducing waste and enabling testing of more containers.
The fast response time of TDLAS may also enable implementation of the enclosed systems and methods in inline production situations.
These and other aspects, features and advantages of which examples of the disclosure are capable of will be apparent and elucidated from the following description of examples of the present disclosure, reference being made to the accompanying drawings, in which:
Specific examples of the disclosure will now be described with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The following disclosure focuses on examples of the present disclosure applicable to determining the integrity of containers by placing a container with at least one gas in an environment with a lower absolute pressure than that inside the container, and measuring an alternated level of the at least one gas in the environment. The environment may be a closed enclosure, such as a closed chamber or closed holder. In some examples, the environment may be an at least partial open enclosure, such as a chamber or a holder with at least one open side. In some further examples, the environment may be an open area. Additionally, in some examples, the container may be a pressurized container, such as a bottle, for example a bottle with carbonated beverage such as soda, or sparkling wine or beer. The container may also be a tray or a bag with at least one added gas with an absolute pressure higher than 1 atm. Alternatively, in some examples, the container may also be non-pressurized, for example a food tray, a non-pressurized beverage bottle or can, a bag, a carton-based container, a metal can, or a plastic based container etc. The container may even have an internal absolute gas pressure less than 1 atm. The headspace in the container contains the at least one gas detectable using an optical sensor. The optical sensor may be using spectroscopy technology, such as TDLAS, to detect the at least one gas. The at least one gas may be, for example carbon dioxide or oxygen. Both these gases are common in modified atmosphere packaging (MAP) which is used to prolong the shelf-life of, for example, food products. The at least one gas may also be, for example, water vapor, carbon monoxide or methane—gases which are also suitable to detect using an optical sensor, such as TDLAS. The amount of alternation of the level of at least one gas in said environment may be used to determine the size of the leak in the container.
The detected light may be analysed in a control unit for determining an alternated level of the at least one gas in the environment. The control unit may be a computer, a microprocessor or an electronic circuit that could run code or a software configured for analysing the light detected by the detector.
In this example the transmitter (5) and detector (3) are placed on the outside of the environment, but they may also be placed inside the environment or elsewhere. In some examples wave guides, such as optical fibers, may be used to guide the light from the transmitter (5) and/or to the detector (3). In this example the environment (2) contains a fan (7) which is used to create a circulation of the gas inside the environment (2) to ensure that the leaked gas from any position of the container (1) reaches the light beam (4). When using an enclosure such as a chamber, it may be advantageous to have an as small volume as possible of the enclosure to make the alternation of the level (concentration) of the at least one gas larger for a certain leak flow.
The detected light may be analysed in a control unit for determining an alternated level of the at least one gas in the environment. The control unit may be a computer, a microprocessor or an electronic circuit that could run code or a software configured for analysing the light detected by the detector.
One example of such a pressure cycle is shown in
The examples illustrated in
In this example, a circulation through the measurement volume (6) and back into the environment (2) is made possible. A pump (7) which may be used for decreasing the pressure and/or circulating the gas is ensuring the gas leaking out from the container (1) reaches the light beam (4).
The detected light may be analysed using a control unit for determining an alternated level of the at least one gas in the environment. The control unit may be a computer, a microprocessor or an electronic circuit that could run code or a software configured for analysing the light detected by the detector.
The detected light may be analysed using a control unit for determining an alternated level of the at least one gas in the environment. The control unit may be a computer, a microprocessor or an electronic circuit that could run code or a software configured for analysing the light detected by the detector.
The above described systems and methods may be implemented as a stand-alone unit for manual bench-top measurements on single containers. Alternatively, may the above described systems and methods be implemented in-line for example in a filling machine after the contained has been sealed. The machine may be configured so that all containers passes through the environment where the measurement is performed. Alternatively, in some examples samples are selected and measured on.
In the described systems and methods, the light source may be a white light source, for example transmitting a collimated light beam, or at least one laser source, such as a diode laser, a semiconductor laser. The wavelengths or wavelength range used for the light source is selected to match the absorption spectra of at least one species of the gas inside the container. The detector may be, for example, a photodiode, a photomultiplier, a CCD detector, a CMOS detector, a Si detector, an InGaAs detector, selected to be able to detect the wavelengths or wavelength range of the light source.
It should be noted that in the examples described above, it is not necessary to measure the gas concentration in absolute values. In some examples, it is sufficient to measure a signal that is related to the gas concentration. In some examples, the spectroscopic signal is related to the gas pressure.
The present invention has been described above with reference to specific examples. However, other examples than the above described are equally possible within the scope of the disclosure. Different method steps than those described above, performing the method by hardware or software, may be provided within the scope of the invention. The different features and steps of the invention may be combined in other combinations than those described. The scope of the disclosure is only limited by the appended patent claims.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1850241-9 | Mar 2018 | SE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/055625 | 3/6/2019 | WO | 00 |
