Dust Control Handbook for Industrial Minerals Mining and Processing

Plastic Pallet WrapThe final consideration for dust control in the palletizing of paper bags is plastic pallet wrapsystems. The purpose of plastic pallet wrap is to contain product and dust leakage from bagsloaded onto full pallets from becoming airborne while also providing protection from torn orruptured bags during the pallet transportation process. Currently, there are two types of plasticpallet wrap systems being used: (1) spiral stretch wrap, and (2) shrink wrap/stretch hoods. Bothsystems are commonly used in the minerals processing industry and they can be used in bothmanual and automated applications. The size of the packaging system will normally dictatewhich pallet wrapping system is most practical.A consideration when using plastic pallet wrap systems is that the bags should be completelyvoid of entrapped air before the plastic wrap is applied. If a protective plastic coating is appliedbefore the bags have been deflated, it will become "loose" and thus, ineffective. In operationswhere entrapped air is a problem, a pallet press should be used to "squeeze" the excess air fromthe bags immediately before the plastic wrap is applied.Spiral stretch wrap was one of the first types of plastic wrapping techniques developed and usedin the industry. This can be performed either through a manual or automated process. Formanual operations, the full pallet is placed in an open area and a worker manually walks aroundthe pallet, unwinding spiral stretch wrap over the pallet. Once completing multiple revolutionsto the point that the pallet is adequately covered, the worker cuts the stretch wrap from the rolland connects the cut end to the pallet.In the automated process, the full pallet of bags is placed on a rotating table. As this table spinsthe pallet round and round, a roll of stretch plastic is continually wrapped around the pallet whileslightly moving up and down at a predetermined wrap tension (Figure 6.19). After enoughrevolutions occur that the pallet is completely sealed, a mechanical device cuts the plastic wrapfrom the roll and assists the unrolled end in being attached to the pallet.Figure 6.19. Automated spiral stretch wrap machine.180 Bagging