How to stretch wrap a pallet: film, pattern and containment force

Stretch wrap holds a unit load together and to its pallet during handling and transport. Done well, the load moves as one piece. Done badly, the cases separate, lean or slide off the pallet, no matter how much film is used. This guide covers the wrap pattern, the film, the equipment, and how to check that a load is wrapped tightly enough.

#The short version

1. Build a good load first. Square, flat top, no overhang. Wrap cannot fix a bad pattern.
2. Start at the base and lock the load to the pallet. Three or more revolutions at the bottom, with the film covering the top deckboards.
3. Spiral up with about 50% overlap between passes.
4. Wrap the top with two or more revolutions, overlapping the top layer.
5. Spiral back down if the load needs more containment.
6. Cut and secure the tail so it does not unwind.
7. Check containment force and adjust.

#Lock the load to the pallet

The most common wrapping failure is film that holds the cases together but not to the pallet. The whole load then slides off the deck in a hard stop.

• Start the first revolutions low enough to cover the top deckboards and lead boards.
• On a machine, use a "roping" device that bunches the bottom edge of the film into a cord, which bites into the pallet.
• By hand, twist the film into a rope for the first turn and run it around the pallet at the level of the top deckboards, so it grips the pallet edges.
• Do not wrap over the fork openings. Film across the entries gets torn by forks and can pull the load.

#Wrap pattern

Top-sheets or a cap of film on top keep rain and dust out and help hold the top layer.

#Containment force: the number that matters

Containment force is the inward force the film applies to the load. It is what holds the cases in place. It depends on the film's pre-stretch, how much tension the wrapper applies, and the number of film layers at any point.

To measure it, use a containment force gauge (a plate and force meter) at a set distance from the load corner and pull the film outward a set distance, following the gauge maker's method. Record the reading on each face, at the base, middle and top.

Wrapper manufacturers and film suppliers publish target containment force ranges by load weight and stability. Heavy, tall and unstable loads need more; light, stable loads need less. Start from the supplier's guidance, then confirm by trial shipments. In Europe, the EUMOS 40509 test method is widely used to test the rigidity of a wrapped load under acceleration.

#Stretch film basics

Most stretch film is linear low-density polyethylene (LLDPE).

Pre-stretch means the film is stretched before it goes onto the load. 250% pre-stretch turns 1 ft of film on the roll into 3.5 ft on the load, which cuts film use and increases the film's holding power.

#How much film does a pallet use?

An estimate for a 48 × 40 × 50 in load: the perimeter is 176 in (14.7 ft). With 20 in film at 50% overlap, the body takes about 5 passes, plus 3 base and 2 top revolutions, about 10 revolutions or 147 ft of film on the load. At 250% pre-stretch that is about 42 ft of film off the roll. By hand, with little stretch, the same load can use several times as much. These figures are estimates for comparison; weigh a wrapped load's film to know your real use.

#Hand wrapping vs machine wrapping

Turntable and conveyor-fed wrappers work best with flat, square pallets with no protruding nails or broken boards. See pallets for automation.

#Alternatives and additions

• Strapping (steel, polyester or polypropylene) binds heavy or dense loads such as bricks, lumber and drums. Use edge protectors under straps.
• Stretch hoods are a tube of film pulled over the load. They give five-sided weather protection and consistent containment on high-volume lines.
• Netting lets produce and hot goods breathe.
• Tier sheets between layers make column stacks more stable.
• Stretch film with UV inhibitors or tint protects loads stored outdoors.

#Common mistakes

• Film not anchored to the pallet, so the load slides.
• Too few top revolutions, so the top layer walks off.
• Film across fork openings.
• Excessive tension crushing box corners on light cartons. Use corner boards.
• Wrapping a leaning or overhanging load, which locks in the problem.
• Loose tail that unwinds in transit.

#Safety when wrapping

• Hand wrapping means walking backward around a load while bent over at the base. Use an extended-core dispenser so you can wrap the base standing up, clear the floor around the pallet first, and wrap in short sessions on busy shifts.
• Turntables create a pinch and entanglement zone. Keep people out of the ring while the table turns, and use the machine's guards and stop controls.
• Film cutters and loose tails are cut and trip hazards. Dispose of cores and scrap film promptly.
• Moving the load: a freshly wrapped load can still be top-heavy. Lift and travel with it low. See how to use a pallet jack.

#Checking the wrap before shipping

A short check at the end of the line prevents most load failures:

1. Push the top corner of the load by hand. It should move with the pallet, not independently.
2. Look for film tears at corners and over sharp edges.
3. Confirm the base film covers the top deckboards.
4. Confirm labels are on the outside of the film and readable.
5. Spot-check containment force on one load per shift, or whenever the film or wrapper settings change.

#For LTL and mixed loads

LTL loads are handled many more times than truckloads. Wrap them tightly, add corner boards, cap the top, and label on at least two sides over the film, not under it. See shipping pallets LTL and mixed pallets.