A pallet (also called a skid) is a flat transport structure, which supports goods in a stable fashion while being lifted by a forklift, a pallet jack, a front loader, a jacking device, or an erect crane. Many pallets can handle a load of . While most pallets are wooden, pallets may also be made of plastic, metal, paper, and recycled materials.
A pallet is the structural foundation of a unit load, which allows handling and storage efficiencies. Goods in shipping containers are often placed on a pallet secured with strapping, stretch wrap or shrink wrap and shipped. In addition, pallet collars can be used to support and protect items shipped and stored on pallets.
Containerization for transport has spurred the use of pallets because shipping containers have the smooth, level surfaces needed for easy pallet movement. Since its invention in the twentieth century, its use has dramatically supplanted older forms of crating like the wooden box and the wooden barrel, as it works well with modern packaging like corrugated boxes and intermodal containers commonly used for bulk shipping. As of 2020 about half a billion pallets are made each year and about two billion pallets are in use across the United States alone.
Organizations using standard pallets for loading and unloading can have much lower costs for handling and storage, with faster material movement than businesses that do not. The exceptions are establishments that move small items such as jewelry or large items such as cars. But even they can be improved. For instance, the distributors of costume jewelry normally use pallets in their warehouses and car manufacturers use pallets to move components and spare parts. The greatest investment needed for economical pallet use is in the construction of commercial or industrial buildings. Ability to pass through standard doors and buildings make handling more convenient. For this reason, some modern pallet standards are designed to pass through standard doorways, for example the europallet (800 mm × 1,200 mm) and the U.S. military .
The lack of a single international standard for pallets causes substantial continuing expense in international trade. A single standard is difficult because of the wide variety of needs a standard pallet would have to satisfy: passing doorways, fitting in standard containers, and bringing low labor costs. For example, organizations already handling large pallets often see no reason to pay the higher handling cost of using smaller pallets that can fit through doors. Heavy-duty pallets are a form of reusable packaging and are designed to be used multiple times. Lightweight pallets are designed for a single use. In the EU, government legislation based on the Waste Framework Directive requires the reuse of packaging items in preference to recycling and disposal.
History
Skids date back to Ancient Egypt and Ancient Mesopotamia, at least as far back as the 1st millennium B.C."Remains of timber, the lengths laid upon the pavement parallel to one another (fig. 114) where a large number of blocks were found, suggest skids upon which they were moved". (Loud, 1936: 108). Cited by Peter Roger Stuart Moorey, Ancient Mesopotamian Materials and Industries: The Archeological Evidence (Eisenbrauns, 1999), page 32.
The development of the forklift and the needs of World War II logistics operations led to substantial use of pallets.
References to the early modern pallets types are slim with a string of patents showing parts of the development. The earliest may be a U.S. patent on a skid from 1924 describing Howard T. Hallowell's "Lift Truck Platform".United States Patent Office, Lift-Truck Platform, patent reference 1,508,183, awarded 9 September 1924, accessed 21 January 2017 In the late 1930s, pallets became more commonplace with the newer forklift types. George G. Raymond and William C. House filed for a patent in 1937 (granted US Patent 2178646 in 1939) for a pallet designed to complement a new pallet jack design; the essential features of both are still in common use today. A 1939 patent from Carl Clark shows a type of pallet with steel stringers. Wartime developments were often patented just after the war, so there is a patent from Robert Braun on a four-way pallet in 1945, and a patent from Norman Cahners (a U.S. Navy supply officer) shows a disposable pallet in 1949. The principle of a modern four-way pallet is described by Darling Graeme in 1949.
Materials Wood
The production of pallets accounts for 43% of hardwood and 15% of softwood usage in the U.S.
The cheapest pallets are made of softwood and are often considered expendable, to be discarded as trash along with other wrapping elements, at the end of the trip. These pallets are simple stringer pallets, and able to be lifted from two sides.
Slightly more complex, hardwood block pallets, plastic pallets and metal pallets can be lifted from all four sides. These costlier pallets usually require a deposit and are returned to the sender or resold as used. Many "four way" pallets are color-coded according to the loads they can bear, and other attributes. Wood pallets can pose serious bio-hazard risks as they are susceptible to bacterial and chemical contamination, such as E. coli problems in food and produce transportation, and even insect infestation, and thus the need for ISPM 15.
Wooden pallet construction specifications can depend on the pallet's intended use: general, FDA, storage, chemical, export; the expected load weight; type of wood desired: recycled, hard, soft, kiln dried or combo (new and recycled); and even the type of fasteners desired to hold the pallet together: staples or nails.
The price of wooden pallets reached a record high during the COVID-19 pandemic, due to increases in the prices of supplies and labor.
Although pallets come in all sizes and configurations, all pallets fall into two very broad categories: "stringer" and "block" pallets. Various software packages exist to assist the pallet maker in designing an appropriate pallet for a specific load and evaluating wood options to reduce costs.
Stringer pallets are one of the original models of wooden pallets. They use a frame of three or more parallel pieces of timber (called stringers). The top deckboards 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 can be made of both wood and plastic.
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.
The least expensive way to improve a pallet is usually to specify better nails. With non-wood pallets, a controlled coefficient of friction is often helpful to prevent the pallet from slipping from forks and racks. Stiffer pallets are more durable, and are handled more easily by automated equipment. If a pallet does not need to be lifted from all four sides, two-way pallets with unnotched stringers may be used, with the additional benefits of added rigidity and strength. Specifying tolerances on flatness and water content may help the supplier meet target requirements. Inspection of pallets, whether in person or by a third-party (such as "SPEQ" inspected pallets) offer additional assurance of quality.
The main processes that are used to manufacture wooden pallets:
Material selection Cutting wood plate / block Chamfering (depends on the demand) Notching Nailing wooden pallet
Due to the International Plant Protection Convention (abbreviated IPPC), most pallets shipped across national borders must be made of materials that are incapable of being a carrier of invasive species of insects and plant diseases. The standards for these pallets are specified in ISPM 15.
Pallets made of raw, untreated wood are not compliant with ISPM 15. To be compliant the pallets (or other wood packaging material) must meet debarked standards, and must be treated by either of the following means under the supervision of an approved agency:
Heat treatment: The wood must be heated to achieve a minimum core temperature of for at least 30 minutes. Pallets treated using this method bear the initials HT near the IPPC logo. Chemical fumigation: The wood must be fumigated with methyl bromide. Pallets treated using this method bear the initials MB near the IPPC logo. From 19 March 2010 the use of methyl bromide as a treatment according to ISPM15 has been banned within all EU member states.European Commission, Commission Decision of 18 September 2008 concerning the non-inclusion of methyl bromide in Annex I to Council Directive 91/414/EEC and the withdrawal of authorisations for plant protection products containing that substance, 2008/753/EC, accessed 31 October 2019 This is due to causing potential harm to the Earth's stratospheric ozone layer.
Treated wood pallets must be stamped on two opposite sides, indicating either HT for heat treated or MB for methyl bromide treatment.
Pallets made of non-wood materials such as steel, aluminum, plastic, or engineered wood products, such as plywood, oriented strand board, or corrugated fiberboard do not need IPPC approval, and are considered to be exempt from ISPM 15 regulations.
Plastic
Plastic pallets are often made of new HDPE or recycled PET (drink bottles). They are usually extremely durable, lasting for a hundred trips or more,Raballand, ibid., p. 11 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. The large supply chains have increased the use of plastic pallets as many organisations seek to reduce costs through waste, transport, and health and safety. Pallets and dollies can be combined (for example the Pally), eliminating pallet instability and the need for additional lifting equipment along with creating valuable space in busy operating environments. They also deliver significant time and cost savings by reducing supply chain handling. Plastics' reusability has contributed to an increase in usage of plastic pallets.