Containment force explained: how hard does your film hold the load?
What containment force is
When stretch film is wrapped around a load, it tries to return to a shorter length. That pull presses the load together and holds it to the pallet. The total force at a point on the pallet is the containment force.
Roughly, it is the result of two things:
- the force of each layer: how hard the film is pulled onto the load as it is applied,
- the number of layers at that point.
Two layers applied with the right force can hold better than four layers applied loosely.
What decides it
- Pre-stretch. Film that is stretched into its working zone and locks the load gives a steady, lasting force. Under-stretched film keeps an elastic memory and can lose force or crush the load. See the right pre-stretch.
- Wrap force on the carriage. How hard the film is pulled between the carriage and the load.
- Wrapping pattern. Number of revolutions, overlap, extra wraps at the top and bottom, and roping.
- Film type and thickness. Different films reach different forces at the same settings.
- The load. Soft or compressible goods give way, and the force is spread differently from rigid cartons.
How to measure it
- Pick fixed points. Measure at several heights, for example near the top, the middle and the bottom, and on more than one side of the pallet. Write down where.
- Use a gauge. A pull gauge or a force gun pulls the film out from the load at the point and reads the force. Keep the method the same every time.
- Measure at the same time after wrapping. Film relaxes in the first minutes and hours, so compare like with like.
- Compare films on the same load. Measure the current film and the new film the same way, on pallets with the same load.
Palletseal lets the rep type in the readings from their own gauge for each point, or load them from the C-Meazure wireless containment force tool, and prints them in the report next to the film saving.
Why it matters when you change film
A thinner or high-performance film can hold a load as well as a thicker one, because correct pre-stretch makes the film stronger and more even. Containment force is the number that shows it. If the force on the new film matches or exceeds the old one at the same points, the buyer has a clear reason to accept the saving.
For the full picture, combine it with a tilt test and, where a bench is available, an EUMOS 40509 acceleration test. Read more in why load stability matters.
Questions we often get
What is containment force?
The force the stretch film exerts on the load to hold it together. It is the sum of the force from all the film layers at a given point.
How is containment force measured?
With a gauge that pulls the film out from the load at a fixed point and reads the force. Measure at several heights and on more than one side, because the force varies over the pallet.
Does more film always mean more containment force?
No. Containment force depends on how the film is applied. Film that is stretched correctly and wrapped with the right number of layers can hold better than more film applied badly.
Is containment force enough to prove a load is stable?
It is one important part. Combine it with a tilt test, and an acceleration test where possible, to show how the load behaves under transport forces.
