Since 1995, Abiss® brand Oxysampler and Oxylos® instruments have historically been designed for applications on crisps, and by similarity on flowpack bags, with Oxysamplers for gas analysers, and more recently Oxylos® which have been improved with leak and burst tests, in a patented system.

For flow pack applications, such as crisps, we can be confronted on production sites with a variety of sizes ranging from 25 g to 1 kg of content.

The formation of a large internal volume to mechanically protect the crisps from external stresses means that leak tests take longer to achieve the desired internal pressure, especially if the bag is free to expand (stretching effect of the film, expansion of the headspace).

But because of the size of the bags and their expansion behaviour, the response time for the leakage measurement, based on the DIN55508-1 standard, could be around 70s to perform the leakage test on a 330g pack.

Although fast and giving a result with a minimum of influencing variables, when compared for example with other positive pressure measurement techniques, such as pressure variation according to DIN55508-3, volume expansion introduces a bias in the result for the same test time, or requires a longer test to reduce uncertainty.

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What’s more, Exos® and Oxylos® can analyse the gas in the internal atmosphere in addition to measuring the leak, so you know the initial atmosphere of the pack and can anticipate the effect of leak size on gas changes by directly correlating the two values. This means a minimum of influencing variables, high sensitivity and controlled pressure conditions, whatever the shape and construction of the packaging.

The Exos® solution is versatile, easy to use and can provide key performance indicators for production line quality control. Exos® applies a pre-defined test pressure and then calculates the flow rate required to maintain that pressure. The flow rate is an aggregate of all leaks through the package, whereas other techniques provide no data.

You can then easily examine the distribution of leakage values and their deviation, as shown in the following figure, the ideal shape being a straight line with a small slope proportional to the constant sampling :

DECISION SUPPORT

The sensitivity of the instrument allows us to discriminate by experience the causes of leakage among the following examples:

• Film perforation
• Best film material for leak level
• Seal quality
• Presence of product in seals
• The effect of machine settings on performance
• Fatigue phenomena (creep test)

COMMIT TO RELIABLE SPECIFICATIONS

The technique used by Exos® and Oxylos® enables compliance with DIN 55508-1 to be verified:

• Joint strength
• Leakage measurement (down to 5µm)
• Breathability of the packaging
• Gas absorption over time for modified atmosphere applications

The performance achieved is such that the sensitivity, or detection limit, can be as low as a 5µm equivalent diameter perforation at low stress. It is at this level of effective sensitivity that packaging solutions can be truly evaluated. This instrumentation provides the right tool to measure and control improvements, and ultimately to act on the most cost-effective solution, becoming a true quality differentiator for the development of your strategic markets.

Knowing the modified atmosphere without measuring leaks can lead to the wrong conclusion if contamination is detected in a package while the gas level is still good after a few hours.

Even if a 0.5 to 2 µm pathogen has no chance of passing through a 5 µm perforation, an initial population of Escherichia coli in the package can be multiplied by 10 in 50 hours if a certain mass of O2 is supplied by structural defects. For example, after 15 hours, the headspace can still be measured below 1% O2, but with a defect as low as a leak rate of 1ml/min and maintained for 6 hours under a pressure difference condition of only 10 mbar, provides the necessary number of molecules to grow the pathogen.