Major types of pallets used in warehousing and logistic services
Stringer pallets are one of the original models of wooden pallets. They use a frame of three or more parallel pieces of timber. The top deck boards are then affixed to the stringers to create the pallet structure. Stringer pallets can have a notch cut into them allowing “four-way” entry. Forklifts can lift a stringer pallet from all four directions, though lifting by the stringers is more secure. Stringer pallets no longer need to be built in or permanently attached to the pallet, making it possible to customize the basic pallet. Stringer pallets can be made of both wood and plastic.
Block pallets are typically stronger than stringer pallets. Block pallets utilize both parallel and perpendicular stringers to better facilitate efficient handling. A block pallet is also known as a “four-way” pallet, since a pallet-jack may be used from any side to move it.
Carrier blocks are specialized pallets for lumber carriers
Flush pallets are pallets with deck boards that are flush with the stringers and stringer boards along the ends and sides of the pallet.
All stringer and some block pallets have “unidirectional bases,” i.e. bottom boards oriented in one direction. While automated handling equipment can be designed for this, often it can operate faster and more effectively if the bottom edges of a pallet have bottom boards oriented in both directions. For example, it may not need to turn a pallet to rack it, and operation is less sensitive to pallet orientation.
Plastic pallets are usually extremely durable, lasting for a hundred trips or more and resist weathering, rot, chemicals and corrosion. The benefits of plastic pallets over wood pallets include the ability to be easily sanitized, resistance to odor, fire retardancy, longer service life span, durability and better product protection, non-splintering, and lighter weight, thus saving on transportation and labor costs and making them safer and more environmentally friendly. They often stack.
Plastic pallets are exempt by inspection for biosafety concerns, and easily sanitize for international shipping. HDPE is impervious to most acids and toxic chemicals clean from them more easily. Some plastic pallets can collapse from plastic creep if used to store heavy loads for long periods. Plastic pallets cannot easily be repaired, and can be ten times as expensive as hardwood,[ so they are often used by logistics service providers who can profit from their durability and stackability.
Plastic pallets are produced and used widely in the U.S. and Europe, spurred by the adoption of the ISPM 15. A full comparison of wood vs plastic can be made by a life cycle analysis. Plastic pallets can cost 10 times as much as hardwood pallets and even more expensive compared to cheap expendable softwood pallets.
There are six main types of plastic processes that are used to manufacture pallets:
High pressure injection molding
