These portable platforms, on which packaged materials can be handled and stored , can be had in a variety of standard sizes and in almost any custom-made size. The dimensions, however, tend to be set by the transportation vehicle in which they will move. The most common 88-in. truck width, and the 108-in. boxcar width have resulted in a "standard" pallet size of 42 by 48 in., which fits two across in a truck (the 42-in. side) and two across in a boxcar (the 48-in. side), with adequate clearance for maneuvering the lift truck handling them.
There are several variations of this basic size, including the well used G.M.A. (Grocery Manufacturers Assn.) size of 48 by 40 in. The choice of the exact size depends on the truck and boxcar width normally available, the size of the package load, and the customer's receiving and handling facilities. Ideally, the sum of the package dimensions should exactly fit the pallet, but in actual practice this is virtually impossihle. The following rules of thumb are helpful:
For bags: exact pallet dimensions, or up to 1/2-in, overhang on each side. For cartons: pallet dimensions or underhang by 1/2, in. on each dimension. For drums, cylinders, etc.: pallet dimensions or underhang by as much as 1 in.
Pallet patterns to achieve the above conditions are numerous. Figure 7-53 shows some common patterns used in the chemical process industries. Other considerations aside it is advantageous to use the pattern that most completely uses the space available. It is time consuming to use trial and error to determine the most efficient pattern. These are the two areas where Opti-Miser will save time and money; Pattern development and efficiency.
The traditional material for pallet construction has been hard-wood such as oak, ash, and maple. Yellow pine is also often used. Nails and adhesives are used to join component pieces. The growing shortage of hardwood has increased the cost of wooden pallets to a point where plastic pallets and composites of wood, paper, and plastics are economically feasible. Much development work is being done on plastic-pallet design to handle typical loadings. Because of the cost of disposing of expendable pallets, returnable ones are often justified.
Fig 7-53. Typical pallet patterns. (a) Unitblock pattern is commonly used, although oftentimes unstable. It may be made more secure by encircling the top tier of containers with wire or strapping. (b) Multiblock and Irregular (Brick) patterns are most commonly used. Containers are interlocked to make a relatively stable load by placing alternate tiers at a 90-deg. position to each other. (c) Pinwheel pattern is used where the Brick patterns are found unstable. Alternate tiers can be interlocked.