DE102014202596A1 - Method and device for leak testing a closed container - Google Patents

Abstract

The present invention relates to a leakproofing method of a sealed container (20) having a first inner sealed volume (21) filled with a first gaseous substance having a first pressure (p1). In this case, a second pressure (p2), which is greater than the first pressure (p1), is generated in a second volume (81) surrounding the container (20). To generate the second pressure (p2) in the second volume (81) surrounding the container (20), a second gaseous substance which has a Raman spectral band lying in a different wavelength range than the Raman spectral bands of the first gaseous substance, filled. After lapse of a predetermined time, the concentration of the second gaseous substance molecules in the first volume (21) of the container (20) is measured by Raman spectroscopy.

Description

State of the art

The present invention relates to a method and apparatus for leak testing a sealed container having an internal closed volume filled with a first gaseous substance at a predetermined pressure.

In particular, in the field of food industry and the pharmaceutical industry to ensure that containers are bacteria-proof. It is further desirable that such containers are also virus-proof. Bacteria have a diameter of about 0.5 microns, viruses of about 10 nm. In a bacteria-proof or virus-tight container no bacteria or viruses may occur. A bacteria-proof container must not have any holes that are about 1 μm in diameter. This means that gaseous leak rates in the range of 1 × 10 ^-5 Pa · m ³ / s must be reliably detected for such a bacteria-proof container. In particular, in the field of pharmaceutical or food industry non-destructive methods are often used for leak testing of sealed containers or packaging.

Such a non-destructive method for leak testing a sealed container is for example from EP 1 021 697 B1 known. In this method, a sealed container comprising at least one liquid is introduced into a test chamber in which a pressure is created which is less than the pressure prevailing in the container. In this case, the pressure prevailing in the test chamber is less than or equal to the vapor pressure of the at least one liquid. In this method, a leaktightness or leakage test is based on a leakage rate of the gas and / or vapor molecules emerging from the closed container.

From the document DE 10 2009 026 744 A1 For example, a method and apparatus for leak testing a component having an internal sealed volume is known. In this case, a pressure difference between the closed volume and a volume surrounding the component is generated. Further, after a predetermined time, a number of molecules is measured by Raman spectroscopy in the volume in which the lower pressure has prevailed, and the measured number of molecules is compared with the number of molecules determined before the lapse of the predetermined time. Thus, in this method must be measured before and after expiration of the predetermined time.

In addition to non-destructive, serial monitoring methods, destructive methods are also known in which the container is opened and the gas contained is analyzed in the laboratory. Here, however, only random examinations are possible.

Disclosure of the invention

The inventive method for leak testing a sealed container with the features of claim 1 and the device for leak testing with the features of claim 10 have over the prior art has the advantage that in this case a leak of a sealed container filled with an interior with a first substance first volume is determined in a simplified manner by means of a single concentration measurement of the molecules of a second gaseous substance which has entered the first volume of the closed container and has different physical properties than the first substance. For this purpose, a second pressure, which is greater than the first pressure of the first substance present in the first volume of the container, is generated in a second volume surrounding the container by filling in the second substance. The second substance causes a change, for example an increase, of the Raman spectral band of the first gaseous substance or has a Raman spectral band lying in a different wavelength range than the Raman spectral bands of the first gaseous substance or suitable by Raman mathematical methods Spectral bands of the first gaseous substance separable and thus distinguishable. Further, after lapse of a predetermined time, the concentration of the second gaseous substance molecules in the first volume of the container is measured by Raman spectroscopy. As a result, it is further achieved that contamination of the second volume by molecules of the first substance emerging from a closed container with leakage is avoided. Thus, a container leak without contamination of the environment can be detected in one step in a simple and secure manner nondestructive.

The dependent claims show preferred developments of the invention.

According to a preferred embodiment of the invention, Raman spectroscopy is performed on the container introduced into the second volume. Thus, pressure generation and spectral analysis can be performed without moving the container in one location. According to the invention, a container to be tested can be introduced into a pressure chamber in which by filling the second substance of the second pressure is generated. Here, the second volume corresponds to the volume of the pressure chamber. After the lapse of the predetermined time, which is long enough for enough molecules of the second substance to enter the first volume of the container, Raman spectroscopy is then performed to measure the concentration of the molecules of the second gaseous substance in the first volume of the container. During the performance of Raman spectroscopy then remains to be tested container in the pressure chamber. It is very advantageous that by means of a leakage test according to the invention preferably also the presence of leaks, which are in the range of order of bacteria or viruses, by means of a Raman spectroscopy, that is, by means of an optical method, can be easily detected. In the leakage test according to the invention, a Raman spectroscopy, that is, an optical method is used which is non-destructive and contactless feasible and thereby does not affect the necessary sterility of the contents of a container to be tested.

In this embodiment of the invention, the presence of another test cell for performing Raman spectroscopy is not necessary. It is also advantageous that in such a pressure chamber both based on a Raman spectroscopy leak test of a container, in the first volume of which atmospheric pressure prevails, is very accurate feasible, as well as based on a Raman spectroscopy leak test of a container in whose first volume vacuum is present or a first pressure prevails that is less than the atmospheric pressure, is very accurate feasible. It is also very advantageous that for carrying out the Raman spectroscopy the container to be tested does not have to be led out of the pressure chamber. In this case, it is avoided that the molecules of the second gaseous substance escape from the container to be tested, after the container to be tested is led out of the pressure chamber, to be introduced later into a test cell for performing the Raman spectroscopy. For example, the pressure chamber may be evacuated prior to performing the Raman spectroscopy, so that in the pressure chamber vacuum or the first pressure, in particular that first pressure which is less than the atmospheric pressure is adjusted.

According to a further preferred embodiment of the invention, the Raman spectroscopy is alternatively carried out on the guided out of the second volume container, whereby a simple process control is made possible. According to the invention, a container to be tested can be introduced into a pressure chamber in which the second pressure is generated by filling in the second substance. Again, the second volume corresponds to the volume of the pressure chamber. After the lapse of the predetermined time, which is long enough for enough molecules of the second substance to enter the first volume of the container in the event of a leak, the container is introduced into a separate test cell in which Raman spectroscopy is used to measure the concentration of the molecules second gaseous substance is performed. During the performance of Raman spectroscopy, the container to be tested remains in the test cell. In the first volume of the container to be tested atmospheric pressure can prevail. In the first volume of the container to be tested may also be present vacuum or a first pressure which is less than the atmospheric pressure. For example, the test cell can be evacuated with the inserted container after the lapse of the predetermined time and before performing the Raman spectroscopy, so that in the test cell vacuum or the first pressure, in particular that first pressure, which is less than the atmospheric pressure is adjusted. For example, atmospheric pressure may be present in the test cell. It is very advantageous that when there is atmospheric pressure in the first volume of the container to be tested, atmospheric pressure also prevails in the test cell. In this case, during the performance of Raman spectroscopy, no molecules of the second substance can escape from the container to be tested.

Preferably, the first volume of the container to be tested is filled with air and the container to be tested is depressed in the second volume with nitrogen as a test gas. The entering in the presence of a leak in the container to be tested nitrogen molecules cause the detectable after pressing the container to be tested Raman spectral band changed, in particular increased, compared to the Raman spectral bands of air, which are detectable before the container to be tested were. The molecules entering the container to be tested also cause a change in the concentration of the nitrogen molecules in the container to be tested. This change in concentration is then measured by Raman spectroscopy. Since the concentration of nitrogen in air is known, in order to measure said concentration change, the concentration of the nitrogen molecules in the container to be tested prior to the exposure of this test gas to the nitrogen need not be measured separately.

In particular, when there is atmospheric pressure in the container to be tested, it is preferable that a plurality of containers to be tested are simultaneously exposed to the second pressure in the pressure chamber and then introduced individually into the test cell for performing Raman spectroscopy. Preferably, the predetermined time in which a container to be tested must be exposed to the second pressure, much longer than the time required to perform the Raman spectroscopy. In this case, the sensitivity of the leak test can be substantially increased by extending the predetermined time in which the containers to be tested are exposed to the second pressure. If atmospheric pressure exists in the first volume of the individual sealed containers, the respective waiting times until the individual containers can be introduced into the test cell for performing Raman spectroscopy have no influence on the concentration of the molecules of the first container in the first volume second gaseous substance. Therefore, particularly in the case just mentioned, a plurality of containers to be tested can be simultaneously introduced into the pressure chamber to be simultaneously exposed to the second pressure. Thereby, the total time for performing the leak test of the plurality of containers can be greatly shortened.

According to the invention, a direct molecule-specific concentration measurement of the molecules of the second substance which have entered the first volume of the container is carried out nondestructive and contactless on site by means of Raman spectroscopy. Characterized in that the leak test according to the invention is based on a molecule-specific measurement of molecules which have entered the first volume of a container to be tested with leakage and not on a molecule-specific measurement based on a leak rate of the leaked from the first volume of a container to be tested container molecules, the leaktightness or leakage test is falsified by foreign substance molecules which may occur, for example, because of a leaky test chamber in which such a container to be tested is located during the leak test, or because of materials present outside the container such as fats or oils ,

In a very preferred embodiment of the invention, such a pressure difference is generated between the second pressure and the first pressure that when the container has at least one predetermined size exceeding a leak, a predetermined one in the first volume after the lapse of the predetermined time Limit exceeding concentration of the molecules of the second gaseous substance are located.

In another highly preferred embodiment of the invention, the pressure difference between the second pressure and the first pressure is at least 510 Pa. Also, the pressure difference between the second pressure and the first pressure may be between 10 ⁵ Pa and 6 x 10 ⁵ Pa.

The first gaseous substance may be nitrogen or oxygen or ethanol vapor or water vapor. Furthermore, the second gaseous substance may be air. In other words, the first gaseous substance or the gas phase of a sealed container used in particular in the pharmaceutical or food industry includes air, nitrogen or vapor of the filled liquids, which are mostly aqueous or alcoholic solutions. It makes sense to use a second gaseous substance as the test gas which has at least one characteristic Raman spectral band which is not spectrally disturbing in the gas phase of a container to be tested. In particular, the use of air or compressed air or nitrogen as a test gas for cost reasons makes the most sense. Preferably, depending on the filling substance, the use of nitrogen as a test gas makes the most sense, since nitrogen can be used as an inert gas to avoid contamination in the smallest traces of container filling.

For example, a Raman spectral band of oxygen (O ₂ ) at a wavenumber of 1556 cm ^-1 , a Raman spectral band of nitrogen (N ₂ ) at a wavenumber of 2331 cm ^-1 , is a Raman spectral band of ethanol in between 800 cm ^-1 and 1550 cm ^-1 extending wave number range and a Raman spectral band of water at a wave number of 3000 cm ^-1 . From this example, it can be seen that air fractions in the ethanol or water vapor can easily be distinguished.

The closed container is preferably transparent or has a transparent area or a built-in optical window. In the leakage test according to the invention by means of a Raman spectroscopy, it is necessary that the container to be tested has an optical access.

Preferably, the sealed container may be a glass container, in particular a vial.

Preferably, the sealed container is a vacuum container. This means that the first volume of the sealed container to be tested need not be filled with gas and / or steam. There may also be vacuum in the first volume of the container.

More preferably, the closed container is a firmly formed container. Such a firmly formed container has no flexible areas or walls.

Preferably, the sealed container comprises in addition to the first gaseous substance another substance which is a liquid or a solid, in particular a pulverulent solid. Preferably, the further substance may also be gaseous. In other words, the leakage test method according to the invention can be carried out independently of the state of aggregation of the further substance present in the closed container.

The method according to the invention can be carried out in parallel with a method for determining residual oxygen. Here, the second gaseous substance is air. In this case, the pressurization time of the sealed container with air, that is, the predetermined time in which the sealed container is exposed to the second pressure, should be long enough that the residual oxygen concentration in the container to be tested with leakage is above a predetermined limit.

drawing

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. For the designation of the same components, the same reference numerals have been used in the drawing. In the drawing is:

1 a schematic sectional view of a device according to the invention for leak testing a sealed container according to a first embodiment of the invention, and

2 a schematic sectional view of a device according to the invention for leak testing a sealed container according to a second embodiment of the invention.

Preferred embodiments of the invention

In the 1 is a sectional view of a device according to the invention 10 for leak testing of a sealed container 20 illustrated according to a first embodiment of the invention.

The container 20 has a first inner closed volume 21 which is filled with a first gaseous substance having a first pressure p1. The device 10 further includes a pressure chamber 30 with a second volume 31 , To perform a leak test by means of the device 10 becomes the container to be tested 20 in the pressure chamber 30 introduced. In the pressure chamber 30 is generated by filling a second gaseous substance having a Raman spectral band which is in a different wavelength range than the Raman spectral bands of the first gaseous substance, a second pressure p2. The container is exposed to the second pressure p2 for a predetermined time. The predetermined time must be so long that when the container 20 has a hole or a leak, enough molecules of the second gaseous substance in the first closed volume 21 of the container 20 can penetrate. The container 20 is preferably by means of a lid 23 locked. The container 20 more preferably can not cover 23 and be formed, for example, as glass, which is sealed directly after filling by means of a molten glass. This means that the containers to be tested 20 even such self-contained container can be.

After the lapse of the predetermined time, the concentration in the first volume becomes 21 of the container 20 molecules of the second gaseous substance are measured by Raman spectroscopy. This includes the pressure chamber 30 Furthermore, a laser, in particular designed as a laser diode 40 for generating a laser beam 50 and a spectrograph 60 for detecting and evaluating stray light 51 of the laser beam 50 ,

The laser 40 includes an illumination optics with a flexible light guide 41 and / or a lens system. The light guide 41 can also be designed as a glass fiber. The container 20 may be transparent or have at least one transparent area or at least one observation window.

The one from the laser 40 generated laser beam 50 is via the flexible light guide 41 to the container 20 guided. Because of the small diameter of the laser beam 50 , the container edge about 1 mm and in the middle of the container 20 about 0.4 mm, can also containers 20 be tested, which have only a small observation solid. This is the case, for example, when the container 20 next to the first gaseous substance another substance 22 includes high capacity. The container to be tested 20 penetrating laser beam 50 is by means of a on the the laser 40 opposite side of the container 20 positioned absorber 70 absorbed.

Preference is given to a laser 40 used a laser beam 50 generated at a wavelength which lies in the red or infrared spectral range. So it can be ensured that in the means of the laser beam 50 illuminated areas of the container 20 no fluorescence can occur. Thus, neither the first gaseous substance nor the other in the container 20 filled substance 22 through the laser beam 50 to be damaged. This is especially important in medical filling products.

Further, such scattered light emitted at an angle θ becomes 51 of the laser beam 50 by means of a detection optics with another flexible light guide 61 and / or another lens system on the spectrograph 60 led to the concentration measurement. The further light guide 61 can also be designed as another fiber. The angle θ, which is also referred to as the detection angle, can assume values between 0 ° and 360 °, in particular a value of 90 ° or values between 90 ° and 180 °. When the container 20 is transparent on its upper side, that is, for example, that the container 20 by means of a transparent cover 23 or is sealed directly after its filling by means of a molten glass, a detection of the scattered light 51 also done from above.

The spectrograph 60 preferably comprises a monochromator (not shown separately) for selecting on the spectrograph 60 incident stray light having a wavelength which lies in the Raman spectral band to be detected of the second gaseous substance or corresponds to a Raman spectral line of the second gaseous substance. More preferably, the spectrograph comprises 60 a CCD camera (not shown separately) for converting the scattered light selected by the monochromator into a measurement voltage. The measurement voltage generated by the CCD camera is directly proportional to the number of photons in the first volume 21 of the container 20 located molecules of the second gaseous substance have been scattered at the detection angle θ Raman and on the spectrograph 60 have come within a given detection time.

When measuring the concentration in the first volume 21 of the container 20 After the elapse of the predetermined time molecules of the second gaseous substance, the existing due to the physical conditions relationship between the said number of photons and said concentration is used.

In the 2 is a sectional view of a device according to the invention 10 for leak testing at least one sealed container 20 illustrated according to a second embodiment of the invention. Such a container to be tested 20 each has a first inner closed volume 21 which is filled with a first gaseous substance having a first pressure p1. The device 10 includes a pressure chamber 80 with a second volume 81 ,

In the pressure chamber 80 can one or more containers to be tested 20 be introduced. For this purpose, before or the container to be tested 20 preferably by means of a linear conveyor belt or by means of a rotatable rotary table with a clock rate of, for example 100 Containers per minute led into the pressure chamber area. The number of containers to be tested 20 are not for leak testing of containers 20 relevant, but only in terms of transport management, such as in terms of handling, the clock rate or the space required to interpret.

Further, in the pressure chamber 80 by filling a second gaseous substance or a test gas with a Raman spectral band, which lies in a different wavelength range than the Raman spectral bands of the first gaseous substance, a second pressure p2 is generated. The filling of the test gas, for example, via a not separately in the 2 shown Prüfgaseinlass done with shut-off valve.

To perform a leak test by means of the device 10 becomes the container (s) to be tested 20 for a predetermined time the second pressure p2 exposed or depressed for a predetermined time with the test gas. This time, in which the containers are depressed with the test gas, must be so long that if a container to be tested 20 has a hole or a leak, a sufficient number of molecules of the test gas in the first closed volume 21 of the container 20 can penetrate. The longer this time, the greater the concentration of the molecules of the test gas in the first volume of a container 20 with a leak.

For example, the test gas is air and the first volume 21 of the container 20 is filled with nitrogen.

If the container to be tested 20 a bacteria-proof container, such as a vial should be, so leak rates in the range of 1 · 10 ^-5 Pa · m ³ / s must be reliably detected. Such a leakage rate would be, for example, for a sealed container 20 arise in its first volume 21 Vacuum prevails, a hole or a leak of about 1 has μm and was depressed with test gas in the form of air at atmospheric pressure.

The larger the second duck p2 of the test gas, the faster a sufficient number of molecules of the test gas penetrate into the first volume 21 of the closed container 20 one. The limitation of the second pressure p 2 of the test gas depends on the strength of the container to be tested. Usually, the vials used in the pharmaceutical industry hold a pressure difference between the second pressure p2 and the first pressure p1 of about 6 · 10 ⁵ Pa ·. It means that Vials a test gas with a second pressure p2 of up to 7 · 10 ⁵ Pa · can be exposed.

To calculate the dependence between two leakage rates of the incoming molecules, which occur in the presence of different values of the first pressure p1 and / or the second pressure p2, it is assumed in sufficiently accurate approximation that the flow of the entering molecules is visco-laminar. This means that when the second pressure p2 is 2 × 10 ⁵ Pa or 7 × 10 ⁵ Pa · and in the first volume 21 of the closed container, a first pressure p1 of 1 × 10 ⁵ Pa · prevails, instead of the above-indicated leak rate of 1 × 10 ^-5 Pa · m ³ / s only leak rates in the range of 3 · 10 ^-5 Pa · m ³ / s or of 5 · 10 ^-4 Pa · m ³ / s are hedged.

For example, when the test gas is air having a standard oxygen concentration of about 200,000 ppm and a second pressure p2 of about 2 × 10 ⁵ Pa or about 7 × 10 ⁵ Pa · and the container to be tested 20 a first volume of 0.5 cm ³ filled with nitrogen at a first pressure p 1 of about 10 ⁵ Pa and a hole or a leak of the order of 1 μm and for a period of 10 s has been exposed to the second pressure p2, a leakage rate of about 3 · 10 ^-5 Pa · m ³ / s or 5 · 10 ^-4 Pa · m ³ / s will occur. After the expiration of this time of 10 s will be in the first volume 21 of the closed container 20 an oxygen concentration in the nitrogen filling of about 1184 ppm resp 19739 set ppm.

After the expiration of the predetermined time in which the container or containers to be tested 20 have been exposed to the second pressure p2 of the test gas, the container or containers 20 from the pressure chamber 80 led out. Depending on the nature of the container 20 are then small waiting times of, for example, each considerably less than 1 s to achieve a uniform distribution of the molecules of the test gas in the first volume 21 of each of the containers to be tested 20 observed. Even large waiting times are allowed, as when the first pressure is in the first volume 21 a container to be tested 20 existing first gaseous substance, which may comprise gas and / or vapor, is equal to the atmospheric pressure, such a waiting time for the actual tightness test is insignificant, since due to the then no longer present pressure difference between the first pressure p1 and the ambient air pressure no outflow of molecules through a leakage of the containers 20 takes place. Diffusion processes can be neglected here.

After the expiration of the waiting time, the concentration of the first volume 21 of the container 20 entered or located molecules of the test gas measured by Raman spectroscopy. This is in the device 10 a separate test cell 90 provided, the one designed in particular as a laser diode laser 40 for generating a laser beam 50 and a spectrograph 60 for detecting and evaluating stray light 51 of the laser beam 50 includes.

To perform the Raman spectroscopy, the container or containers to be tested are 20 to or through the test area of the test cell 90 preferably guided by means of a linear conveyor belt or a rotatable rotary table. When using a linear conveyor belt can then be stopped for a detection time of, for example, less than 1 s. When using a rotary rotary table eliminates the stopping, as long as the residence time of the container 20 on the rotary table is long enough for performing Raman spectroscopy. By means of the spectrograph 60 For example, scattered light is used to perform Raman spectroscopy 51 of the laser beam 50 recorded and preferably evaluated directly online, that is, a so-called in-situ Raman spectroscopy is performed.

The laser 40 includes an illumination optics with a light guide 42 , The light guide 42 is preferably formed as a glass fiber. The container 20 may be transparent or have at least one transparent area or at least one observation window. The one from the laser 40 generated laser beam 50 is over the light guide 42 to the container 20 guided. The container to be tested 20 penetrating laser beam 50 is by means of a on the the laser 40 opposite side of the container 20 positioned absorber 70 absorbed. The illumination optics can preferably also be designed as a lens system.

Further, the stray light emitted at an angle θ becomes 51 of the laser beam 50 by means of a detection lens with a lens system 62 on the spectrograph 60 led to the concentration measurement. The angle θ, which is also referred to as the detection angle θ, can assume values between 0 ° and 360 °, in particular a value of 90 ° or values between 90 ° and 180 °. When the container 20 is transparent on its upper side, that is, for example, that the container 20 by means of a transparent cover 23 or is sealed directly after its filling by means of a molten glass, a detection of the scattered light 51 also done from above.

The spectrograph 60 preferably comprises a monochromator (not shown separately) for selecting from the spectrograph 60 incident stray light 51 having a wavelength in the Raman spectral band of the test gas to be detected or corresponds to a Raman spectral line of the second gaseous substance. More preferably, the spectrograph comprises 60 a CCD camera (not shown separately) for converting scattered light selected by the monochromator into a measurement voltage. The measurement voltage generated by the CCD camera is directly proportional to the number of photons in the first volume 21 of the container 20 located molecules of the test gas have been scattered at the detection angle θ Raman and the spectrograph 60 have come within the detection time.

When the test gas is air and the first volume of the container 20 is filled with nitrogen, then by means of Raman spectroscopy, the concentration in the first volume 21 a container to be tested 20 measured oxygen molecules.

When measuring the constant concentration in the first volume 21 of the container 20 The molecules of the test gas which are present on the basis of the physical conditions, use the linear relationship with a defined zero point between the stated number of photons and the stated concentration. More specifically, the number of photons as a product results between the concentration, a form factor, the laser power of the laser 40 and the detection time. The form factor is for one in the device 10 arranged Raman measurement setup with fixed sizes constant. The Raman measurement setup of the device 10 includes the test cell 90 together with the laser 40 and the corresponding illumination optics and the spectrograph 60 and the corresponding detection optics. Here, the form factor of the temperature, the wavelength of the laser beam 50 , the wavelength of the Raman spectral band to be examined, or Raman spectral line of the test gas, by the Raman measurement setup of the device 10 determined detection angle θ, the by the Raman measurement setup of the device 10 determined detection space angle, the detected reader beam length and optical influences, due to the geometry of a container to be tested 20 and / or due to loss of used optical systems, such as observation windows, lenses, apertures, etc., depending.

The in the above-mentioned linear relationship with defined zero point between said number of photons and the occurring form factor can be determined in a very simple manner by means of a calibration, in particular by means of a one-point calibration, with adjusted laser power and set measurement or detection time.

If the test gas is air, the calibration can be done with a measurement of the number of photons scattered by the oxygen of the ambient air Raman by means of the same Raman setup. Also, the calibration can be performed with a measurement of the number of photons scattered by nitrogen of the ambient air Raman by means of the same Raman setup. In this case, the known and assumed as constant oxygen concentration of 20 , 95% or the known and assumed to be constant nitrogen concentration of 78.08%. The measurement of the number of photons scattered by ambient air oxygen Raman can occur within a detection time of less than 1 second. This means that when air is used as the test gas, also the measurement of the concentration in the first volume 21 a container to be tested 20 located oxygen molecules can be done in less than 1 s.

The linearity of the number of Raman scattered photons, as measured by Raman spectroscopy, with respect to laser power and detection time can be used to measure the concentration in the first volume of a container to be tested 20 located molecules of the air used as test gas, a different laser power and / or detection time in comparison to the carried out in the calibration by means of ambient air measurement by a simple linear conversion. This means that, for example, in the presence of a double detection time, a double detection signal by means of the spectrograph 60 when performing a corresponding Raman spectroscopy is generated. It is not necessary to carry out a new calibration, in which a further measurement is carried out by means of ambient air for the differently set laser power and / or differently set detection time. It is very advantageous that by increasing the laser power and / or the detection time, a more sensitive concentration measurement can be achieved in the smaller concentration range when using a calibration by means of easily available ambient air.

In technical implementation, the calibration is preferably carried out by means of reference containers, such as for example by means of vials which are filled with ambient air and the same nature as the container to be tested 20 exhibit. This calibration preferably takes place before the device is put into operation 10 that is, before, by means of the device 10 ever a tightness test of a container to be tested 20 has been carried out. Thus, optical influences, which arise, for example, by the container geometry, can be calibrated. More preferably, a recurring stability control of the device 10 done by that calibrations are regularly carried out on reference containers filled with ambient air. In the mentioned calibration, the limit of the detection resolution of the spectrograph 60 from for example 16 bit not exceeded.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• EP 1021697 B1 [0003]
• DE 102009026744 A1 [0004]

Claims (14)

Method for leak testing a closed container ( 20 ), which is a first inner closed volume ( 21 ) filled with a first gaseous substance having a first pressure (p1), 20 ) surrounding second volume ( 31 . 81 ) a second pressure (p2) which is greater than the first pressure (p1) is generated, - for generating the second pressure (p2) in which the container (p2) 20 ) surrounding second volume ( 31 . 81 ) a second gaseous substance is introduced, which causes a change in the Raman spectral band of the first gaseous substance or has a Raman spectral band which lies in a different wavelength range than the Raman spectral bands of the first gaseous substance or by mathematical methods of the Raman Spectral bands of the first gaseous substance is separable, and - after expiration of a predetermined time, the concentration or concentration change in the first volume ( 21 ) of the container ( 20 ) molecules of the second gaseous substance is measured by Raman spectroscopy. The method of claim 1, wherein the Raman spectroscopy on the into the second volume ( 31 . 81 ) ( 20 ) is carried out. The method of claim 1, wherein the Raman spectroscopy on the second volume ( 31 . 81 ) guided out container ( 20 ) is carried out. Method according to one of the preceding claims, wherein between the second pressure (p2) and the first pressure (p1) such a pressure difference is generated that when the container ( 20 ) has at least one hole exceeding a predetermined size, in the first volume ( 21 ) are after the expiration of the predetermined time a predetermined threshold exceeding concentration of the molecules of the second gaseous substance. Method according to one of the preceding claims, wherein the pressure difference between the second pressure (p2) and the first pressure (p1) is at least 10 ⁵ Pa and / or between 10 ⁵ Pa and 56 x 10 Pa. Method according to one of the preceding claims, wherein the first gaseous substance is nitrogen or oxygen or ethanol vapor or water vapor and the second gaseous substance is air. Method according to one of the preceding claims, wherein the closed container ( 20 ) is transparent or has a transparent area. Method according to one of the preceding claims, wherein the closed container ( 20 ) is a vacuum container and / or a glass container or a vial. Method according to one of the preceding claims, wherein the closed container ( 20 ) next to the first gaseous substance another substance ( 22 ) which is a liquid or a solid, in particular a powdery solid. Contraption ( 10 ) for the tightness test of a closed container ( 20 ), which is an internal closed volume ( 21 ) filled with a first gaseous substance having a first pressure (p1), the device ( 10 ) a pressure chamber ( 30 . 80 ) into which the container ( 20 ) is insertable and in which a second pressure (p2) which is greater than the first pressure (p1) can be generated, a laser ( 40 ) for generating a laser beam ( 50 ) and a spectrograph ( 60 ) for detecting and evaluating scattered light ( 51 ) of the laser beam ( 50 ), wherein the second pressure (p2) in the pressure chamber ( 30 . 80 ) by introducing a second gaseous substance which causes a change in the Raman spectral band of the first gaseous substance or has a Raman spectral band which lies in a different wavelength range than the Raman spectral bands of the first gaseous substance or by mathematical methods of the Raman Spectral bands of the first gaseous substance is separable, can be generated. Apparatus according to claim 10, wherein the pressure chamber ( 30 ) the laser ( 40 ) and the spectrograph ( 60 ). Apparatus according to claim 10, further comprising a test cell ( 90 ) into which the container ( 20 ) is insertable and which the laser ( 40 ) and the spectrograph ( 60 ). Device according to one of claims 10 to 12, wherein in the pressure chamber ( 30 ) Such a large second pressure (p2) can be generated, that between the second pressure (p2) and the first pressure (p1), a pressure difference of at least 10 ⁵ Pa and / or between 10 ⁵ Pa and 6 10 ⁵ Pa pressure difference can be generated is. Device according to one of claims 10 to 13, wherein the laser ( 40 ) a laser diode and / or illumination optics with a flexible light guide ( 41 ) for guiding the laser beam ( 50 ) to the container ( 20 ) and / or the spectrograph ( 60 ) a detection optics with another flexible Optical fiber ( 61 ) for guiding stray light ( 51 ) of the laser beam ( 50 ) from the container ( 20 ). Device according to one of claims 10 to 14, wherein the laser ( 40 ) a laser beam ( 50 ) at a wavelength which is in the red or infrared spectral range.

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