Ask Steve
April 25, 2023
Question from Jordan: Do the corners of the tier sheets poking through the stretch film affect load containment?
Hi Jordan, thanks for the question. I know this will come as a surprise, but there are two answers to this question.
First, if you are using conventional stretch film and a sharp corner pierces the film, the hole is likely to propagate or enlarge. The extent of the enlargement depends on the tension (between the pre-stretch carriage and load). However, it is certain that if the tension is set for maximum load containment, the web will break immediately when the corner of the tier sheet punctures the film as it is being wrapped. If the web does not break during the wrap cycle when punctured it is because the tension has been reduced, which means your load containment has also been reduced. I have written in previous Ask Steve’s that when a force is applied during transportation (either over the road or moving pallets around in the warehouse), the force will cause the contents of the load to press against the stretch film. For effective load containment, the stretch film must resist this force by not stretching any further. Unfortunately, any tear or puncture in the film (from a tier sheet, corner of a pallet, sharp corner of a box or bag) will enlarge when a force is applied. As the puncture grows, the applied force overcomes the film’s resistance to stretch, allowing the contents to move or shift freely. This is a fundamental cause for load failures. On the other hand, if there are sharp corners, but the film is not puncturing, it means the tension is very low, which means the film will continue stretching when force is applied. So, the first answer to your question is yes, punctures will reduce load containment and possibly lead to a load failure. In addition, lowering tension to eliminate punctures will also reduce load containment and possibly lead to a load failure.
Now for the second answer, and I think you will like this one! I know you have our Rapid Bander installed on your machines, so the simple answer is no, punctures will not compromise your load containment. Our technology incorporates 2 rolls of stretch film, one full web and one banded. The bands are mechanically narrowed through a set of rollers to form a rolled edge or filament at the top and bottom of each band. The bands join, and are incorporated into, the full web through the pre-stretch carriage of the wrapping machine. The filaments that we have embedded in the full web provide reinforcement, preventing a web break when punctured. If there is a puncture, it will only expand to the nearest filament, and immediately stop. This means that optimized tension and pre-stretch settings can be used confidently, lowering your wrapped cost per pallet while substantially increasing your load containment.
I know that sounds too good to be true, and you may be waiting for the catch, but I can honestly say that there is no catch! The reason is quite simple, we use science to solve the challenges of load containment. When you do that, you know how it works, but just as important, you know why it works. Without science, the solution has always been to add more wraps and reduce tension – increasing cost while reducing load containment. Now you know why we rely on science and not traditional thinking!
Thanks for asking!
