Pallet stability
If the entire world population were to be accommodated on Euro pallets, each human would have an area of approximately 20 by 30 centimeters. Although this scenario is highly improbable, it makes one thing very clear: the number of pallets in circulation is incredibly high. You almost certainly ship goods on pallets as well - and they need to be stable for everything to run smoothly. So it's time to take a closer look at pallet stability.
How important pallet stability is, is usually only noticed when it is already too late. Who doesn't know the hassle of customer complaints because of damaged or dented goods - all this is time-consuming and does not bring any profit to the company. But not only the customer is interested in the stability of your pallets, legislators, too, have been paying closer attention to the stability of pallets in road traffic for several years.
The legal framework
Section 22 of the German Highway Code (StVO) states that the load must, amongst other things, be secured in accordance with the recognized standards of technology in such a way that it does not slip, fall over, roll back and forth, fall down or generate avoidable noise, even during emergency braking or sudden evasive action. As a company, you should therefore know exactly how stable your own pallets are. For this, annex 3 of the EU directive 2014/47 provides the EUMOS 40509, which specifies the forces that a load must be able to withstand during transport in order to be stable. This defines the maximum acceptable deformations and displacements during transport.
For a EUMOS 40509-compliant pallet, the dynamic deformation (during transport, for example during emergency braking) must not exceed 10%, the permanent deformation (measurable after transport) must not exceed 5%, and the displacement of the individual layers must not exceed 2%. These values, especially the dynamic deformation, can be measured very precisely on acceleration benches. One such bench can be found in our Mobile Test Center. Based on the data measured in this way, and provided that the limit values are complied with, a certification according to EUMOS 40509 for pallet stability can be issued.
In many cases, however, these limits are not complied with - and this can have a variety of reasons. This is because many different factors must interact and work well together to ensure optimum pallet stability.
First of all, the primary packaging is of crucial importance. If the goods are not carefully and securely cushioned in the carton, there will be no benefit if the carton itself firmly sits on the pallet. This is because movement within the primary packaging can of course also cause significant transport damage.
Secondly, attention must be paid to the scheme according to which the goods are palletized. Ideally, a pallet is loaded flush with the edges, i.e. the edges of the outer cartons form a line with the edge of the pallet. In this way, the space on the pallet is optimally exploited and the stretch film is not additionally strained by overhangs. In addition, it is advantageous to stack cartons alternately, as this creates additional stability.
Once the goods are securely packed and optimally stacked on the pallet, the outer wrapping of the pallet can begin. There are a few different options here.
Shrink and stretch hoods
Both shrink and stretch hoods are commonly used to wrap pallets. Both are slipped over the pallet, and while shrink hoods firmly adhere to the pallet through the application of heat, stretch hoods achieve this through the stretchability of the material. Although the necessary pallet stability can be achieved in this way in some cases, shrink and stretch hoods are not an option preferably used by packaging optimizers because they are very material-intensive due to their extreme thickness (up to 200µ) and thus are easy on neither the wallet nor the environment. At least the same results can also be achieved with a fraction of the material if stretch film is used.
Stretch film
Whether it's for manual or machine application - stretch film is clearly the proven classic among all variants of pallet securing. Through the optimized use of stretch film, maximum pallet stability can be achieved with minimal material input - provided that it is used correctly and the material and machine settings are correctly adjusted. It is not only important that the film itself is of high quality, but also that it is applied correctly. To optimize this, some basic knowledge of how stretch film works is required.
The stretch behavior of films explained in simple terms
The quintessential property of stretch film is that it can be stretched - so far so good. However, only very few people know the exact stretching behavior of stretch films and are also not aware that this knowledge has a decisive influence on pallet stability.
Quite clearly - when applied in its original state, no pallet stability can be achieved with a film. If the film is not stretched at all, it hangs limply from the pallet and yields to the slightest pressure. If the film is now stretched a little, it develops a high retraction force. This means that although it is stretched, it constantly tries to pull back again. If the film is wrapped around the pallet in this state, moderate pallet stability can be achieved, but the retraction force can cause the goods to be squashed on the pallet. In addition, there is still significant stretch potential in the film, so that it yields to the pressure of the goods in the event of an emergency braking - exactly the opposite of what it should do.
Only when fully stretched out film is used, optimum pallet stability can be achieved. Here, the retraction is greatly weakened and the film no longer yields to pressure. According to our experience in the packaging market, the vast majority of users wrap the film around their pallets in a not yet fully stretched-out state, and so it is no wonder that squashed goods are a frequent reason for complaints when shipping pallets. One of the main reasons for this is that many conventional films are not of sufficient quality to be reliably used when fully stretched out. High-performance films, however, achieve excellent results here and guarantee very high pallet stability at minimal consumption.
From theory to practice
In order to be able to optimally apply the basic knowledge regarding the stretching behavior of films, a high amount of knowledge amassed through experience and many different factors must be taken into account. However, some points are universally applicable. The difference between standard films and pre-stretched films is of particular importance. In contrast to standard film, pre-stretched film is already fully stretched out when it is unrolled, and thus has no or only a very low stretch potential left in it.
Hand stretch film
In the area of hand stretch film, standard film is generally not recommended, as the full stretching potential could never be exploited in hand application. Standard films can be stretched by approx. 150 percent, whereas in hand application, films are only stretched up to 80%. This is because considerable force and space are required to exploit the full stretch potential, which is practically unrealistic. The use of a pre-stretched film is therefore ideal here - full stretch can be achieved with little effort and a stable pallet can be wrapped.
Machine stretch film
If a stretch wrapper is used, many more factors have an influence on pallet stability than with manual application. First of all, it is important whether and how much the stretch wrapper can pre-stretch the film. If the pre-stretch is adjustable, standard, power or even high performance film is suitable, whereas pre-stretched film is suitable for machines that either cannot pre-stretch at all or can only pre-stretch very little themselves. However, since many other factors such as the pallet configuration, any overhangs and weight and type of goods also have an influence on the choice of film and the settings of the stretch wrapper, individual advice and adjustment of the stretch wrapper by a packaging optimizer is advisable here in order to achieve optimum pallet stability.
Conclusion
The stability of pallets is crucial for the safe transport of goods. Clear standards are set out for this in EU Directive 2014/47. Optimum pallet stability requires suitable primary packaging, an adequate packing scheme and optimized wrapping. Highest pallet stability can be achieved with fully stretched stretch film. To optimize the use of stretch film, especially machine film, it is advisable to consult a packaging optimizer or technical expert, as many different aspects have to be considered. If you pay attention to all the aspects mentioned, nothing will stand in the way of seamless pallet stability - for less transport damage and more customer satisfaction.
