Volume control

By J.Peyceré / Cetie - Photo Angelo Giampiccolo / Shutterstock
The 30/09/2019
In the field of packaging, the quantity packed is a crucial matter.
From the consumer's point of view, the quantity must of course be the same as that promised by the seller, which is usually clearly indicated on the label. The competent authorities in each country legislate, conduct checks and impose sanctions if necessary to ensure that the consumer does not suffer prejudice. As for the "filler", it is in its best interest not to exceed the required nominal quantity sold, as anything beyond this is a gift to the consumer—who is not even aware of it—and therefore represents a loss with nothing in return.
These general considerations naturally apply to the sector of glass packaging, particularly bottles and jars intended for foodstuffs, which in France represent more than 10 billion units per year. However, the subject becomes more complicated for a number of reasons that can sometimes combine to the point of becoming a headache for the bottlers.
Contacted by several industry players, Cetie has decided to set up a working group on the topic to find ways to improve the situation.

With its 3000 regular users (a four-fold increase in visitors over five years), Cetie has international outreach, enabling the stakeholders in the different countries—European at least—to compare their experience during meetings which are open to all Cetie members, and transform it into consensus-based reference documents (from guides and technical data sheets to FAQs, glossaries and image banks).

This being said, even though the details of the general principles are defined by a European Directive (76-211), each country fine?tunes how the Directive is applied and chooses the degree of pressure it intends to apply to bottlers and market players in general. It is fair to say that consumers in France are particularly well protected by the State, which has transposed the European Directive by decree 78-166 and actively oversees its application.

The Cetie working group will analyse the state of play, starting with the French situation, and this could ultimately lead to the preparation of a Guide to help bottlers better target their choices and practices. The first meeting will be held on 10 October in Paris and will initially serve to take stock of the situation and of the various difficulties encountered.
To simplify things a little, the situation is as follows:
For a given production batch, the bottler must guarantee an average value that is greater than or equal to the nominal capacity value. However, save in special cases where the volume placed in each individual bottle can be controlled and monitored directly, the bottler must manage this guarantee through indirect statistical checks.
Many bottlers typically fill the bottles to level: the bottle is filled through a filler tube which enters the neck of the bottle, with slight over-filling, then the excess liquid is sucked out to reduce the level to a given height.
The bottle manufacturer is also subject to constraints intended to facilitate the bottler's task. If the manufacturer produces a model stated to be a "measuring container" (a choice that can be made jointly with its customer, materialised by a reversed epsilon "'" engraved on the bottle), then it undertakes to monitor and control the volume of the bottles produced according to this model such that they serve as a kind of volume standard for the bottler. In practice this means that the manufacturer chiefly guarantees:
  • the alignment of the mean value of a production batch with the nominal volume;
  • the regularity of the bottle volume for its entire production run.
This mainly implies:
  • setting the weight of glass in the bottles produced to obtain a volume that is as close as possible to the nominal value;
  • then correcting the weight as soon as it drifts in order to remain close to the nominal value (and not accept a systematic shift under the pretext that it will be within the tolerances),
  • and lastly periodically checking that this glass weight value still corresponds to a volume centred on the nominal value.
This organisational constraint, which is relatively simple for the glass bottle manufacturer to manage with round bottles produced by a blow-and-blow process, does not guarantee the bottler that each batch purchased will be centred on the nominal value, nor does it exclude isolated outliers (values relatively far from the nominal).
Thus, even with bottles deemed to be "measuring containers", the bottler must start by assessing the average volume of the bottles before filling in order to adapt the filling level to this average level (by adding to that correction the correction associated with the filling temperature and by adding yet again the few millilitres to compensate for measurement errors); this correction is theoretically valid if the batch of bottles is uniform, which is by no means certain. With "measuring containers", the correction is often relatively small, but with models that are not measuring containers it can be quite significant and in this case the bottler may be obliged to significantly reduce the free volume above the liquid, compromising the capacity of the bottle to withstand normal thermal expansion. Systematic overfilling as a precautionary measure is therefore not always possible, not to mention the cost that this would represent.
Even with good equipment and the relevant know-how, the bottler can find itself with a batch of empty bottles which comply with the law and the specifications and yet be unable to produce a batch of full bottles that comply with the European Directive.
It is on this apparent contradiction that the Cetie working group will be focusing, with representatives from glass bottle manufacturing, beverage brands, stopper and closure manufacturing, and as many willing participants as possible!
 
More infos : contact-us on contact (at) cetie.org
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