Wrapping heavy, sharp and top-heavy loads safely

Heavy loads rarely come apart evenly. Failure starts in one of three places: the top courses, the corners, or wherever something hard is pressed against a stretched web. Under braking, the mass at the top keeps moving forward. That is the part of the load with the fewest turns of film over it and the least support underneath, so the top two or three courses lean, then walk, then go over the edge.

Corners take the second hit. Film touches a pallet along four contact lines, and most of the tension in the wrap is concentrated there. On a dense load those same corners are where the hard edges sit: a cut end, a band buckle, the lip of a steel frame. Tension and a sharp edge in the same place is where a wrap opens.

A wrapped pallet is a web under tension in every direction. That tension is the point — it is what holds the load as one block. It is also what turns a small cut into a large one. Nick a stretched film and the nick acts like a crack tip: the web opens along the line of least resistance and keeps going. The hole does not stay a hole.

One tine mark, one proud staple, one sharp corner from the pallet stacked against it, and several turns of film unload at once. What is left holds the load from the wrong places, usually furthest from where the force is going. That is why pallets that looked perfect in the loading bay arrive leaning.

A top-heavy pallet — a machine on a low frame, drums stacked, a mixed load with the dense items above the light ones — behaves differently in a roundabout. Lateral acceleration acts through the centre of gravity, and the higher that sits, the more leverage the load has against everything holding it. Wrap cannot cancel that leverage. It can only stop the load moving as separate pieces.

Which is why the turns at the bottom matter more than anything at the top. Two revolutions at the base tie the load to the pallet, so the mass above cannot pivot off its own deck. And if the heavy items ended up on top because that is the order the picker walked, restack it. No film fixes a load built upside down.

The instinct after a failure is to buy a thicker film. Thickness buys weight, not structure. An un-reinforced film keeps stretching under a sustained load: it creeps, and it releases its grip over the hours a load spends in a trailer. A thick film creeps in the same way, just more expensively. Resistance to puncture does not scale with micron either.

Toreto ran the comparison on one pallet, one machine, the same power stretch and tension settings, weighing the film and measuring what the wrap held. Solid film at 23µ held 9.9 kg per square inch using 200 g of film, about €0.48 a pallet. At 17µ it still held 9.9, with 140 g. Supersonic and Aerosonic at 16µ held 10 kg per square inch with 66 g, about €0.32. These are Toreto's own tests, and cost moves with film price and pallet size.

Supersonic is the reinforced film in the range: a non-perforated “Tiger” construction with the reinforcing built into the film rather than wrapped around the load afterwards. It gives the web directional rigidity, so holding comes from structure instead of mass. On a heavy or sharp-edged pallet that counts twice — it resists the tear that starts at a puncture, and it holds the load with much less material on it.

It also shortens the cycle. Built-in reinforcement means roughly half the revolutions of ordinary wrap, plain or perforated, by hand or by machine. On heavy pallets that is throughput: the same wrapper puts out about twice as many loads in a shift, each carrying less film.

What it is not is strapping. Reinforced film unitises and protects a load; it does not replace banding, corner boards, edge protection, dunnage or a stack that was built properly. And no film is a load-securing certification — no roll specification can promise that a load meets a transport safety standard, because that depends on the load, the vehicle and how it is restrained inside it.

Put the inside face of the film against the goods; it adheres better. Two revolutions at the base to secure the load to the pallet, then spiral up with a 20–30 mm overlap, then two revolutions at the top. Tension enough to secure the load fully, not so much that you crush cartons or bow a drum. On heavy or unstable loads, spiral back down to the pallet as well: the criss-cross adds real stability on slippery surfaces.

Where pallets are wrapped by hand, wrap quality falls off as the shift does. In Toreto's UK field test a pallet with large gaps and very sharp corners, machine-wrapped and already failing, was rewrapped by hand with the Hyper Wrap System: 151 g instead of 181 g, one minute instead of two, £0.74 instead of £1.00 with labour at £0.20 a minute. Half the metres went on, not half the weight.