Making up the unit
the cargo should, as nearly as possible, exactly fit the pallet or ship sheet. cargo overhanging the deck of a pallet may cause the following problems:
put excessive pressure on the lowest tiers of cargo, particularly that which is in contact with the edge of the pallet. the G forces generated during transport can force the edge of the pallet deck to penetrate the cargo-particularly bags and cartons-with resultant damage to the contents.
make the securing of the load to the pallet difficult or even impossible.
risk the pallet load fouling adjacent cargo or units, with the load becoming wedged or jammed in the stow.
similarly a unit module which is too small for the deck of the pallet will make the securing of the cargo to that pallet less effective, and reduce the ability of ship's bulkhead, container walls, or other cargo to support the pallet loads laterally in the stow.
the height of a pallet load should be such that the pallet and cargo combined leaves a clearance of at least:
50mm(2'') between top of cargo and door header (or ceiling) of a container.
150mm(6") between the top of the uppermost pallet and the lowest deck-head obstruction in a 'tween deck or hold.
method of securing
stapping
man-made fibre or steel. banding should pass under the top deck of the pallet, to remain clear of mechanical handling equipment requirements. some cargo may require protection form the point loading of the strapping, which me by achieved with scrap dunnage, waste cardboard,etc., or using proprietary equipment specially designed for the purpose.
steel strapping may not be suitable for securing cargo that may alter shape or contract, e.g. bags, telescopic cartons etc. Man-made fibres, particularly nylon, may stretch and allow rigid items to move in some instances.
nets:
usually of polypropylene, and used to secure awkward shaped packages onto a pallet.
Glue:
for securing regular stows of cartons or bags. should be strong in sheer strength, but with little resistance to a vertical force when dismantling the pallet load. A 5% dextrine solution can be a suitable mixture for this purpose.
shrink-wrap:
a plastic (transparent) cover over the pallet load which is heat shrunk into place. certain types of plastic wrapping may be put around the cargo without the need of heat. may be used for most goods and provide protection against dirt, pilferage, etc.
locking pattern:
unit loads may be built up on pallet with plan dimension suited to modules being handled. in this way layers may be built up each differing from its neighbours and providing restraint in a similar manner to a brick wall. alternate layer patterns are reversed to "tie in" the layer beneath.
the effect of the pallet
the pallet, because it raises the cargo approximately 150mm (6") off the deck of the hold. has the effect of raising the centre of gravity of the cargo which may, in certain circumstances, have to be allowed for.
pallet use more space than conventional dunnage, perhaps 10 to 14%.