|
|
|
|
Pallet
|
| |
|
| |
A pallet (sometimes called a skid) is a flat transport structure that supports goods in a stable fashion while being lifted by a forklift, pallet jack, or other jacking device.
Discussion
Ask a question about 'Pallet' Start a new discussion about 'Pallet' Answer questions from other users |
Encyclopedia
A pallet (sometimes called a skid) is a flat transport structure that supports goods in a stable fashion while being lifted by a forklift, pallet jack, or other jacking device. A pallet is the foundation of a unit load design, which can be as simple as placing the goods on a pallet, and securing them with straps or stretch-wrapped plastic film, or as exotic as a ULD minicontainer.
While most pallets are wooden, pallets also are made of plastic, metal, and paper. Each material has advantages and disadvantages relative to the others. (See the sections "Phytosanitary compliance" and "Materials used" below.)
Overview
Containerization for transport has spurred the use of pallets because the containers have the clean, level surfaces needed for easy pallet movement. Most pallets can easily carry a load of 1,000 kg (about 2,000 lb). Today, over half a billion pallets are made each year and about two billion pallets are in use across the United States alone.
Pallets make it easy to move heavy stacks. Loads with pallets under them can be hauled by forklift trucks of different sizes, or even by hand-pumped and hand-drawn pallet jacks. Movement is easy on a wide, strong, flat floor: concrete is excellent. A forklift truck can cost the same as a luxury automobile, but a good reconditioned hand-drawn pallet jack costs only a few hundred dollars. The greatest investment is thus in the construction of commercial or industrial buildings where the use of pallets could be economical. Passage through doors and buildings must be possible. To help this issue, some later pallet standards (the europallet and the U.S. Military 35×45.5") are designed to pass through standard doorways.
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 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.
History
Development of commercial transport packaging
Skids and pallets were slowly introduced throughout the early 20th century; wooden boxes, crates, barrels and kegs were much more commonly used to unitize, protect, store and transport goods. The predecessor of the modern wooden pallet was a simple skid that consisted only of stringers fastened to a top deck. It first appeared in American factories in conjunction with the low lift truck. A crude low lift hand truck was invented in 1887 and a more durable, all-steel low lift truck design was introduced in 1909.
The high lift fork truck first appeared in 1915. With further modification in 1919, the truck could lift loads several feet high while other improvements included cantilever design and forks. The emergence of forks as well during the same period enabled lift trucks to handle a much greater range of materials.
Another development was the new capability of the mast of the fork lift to tilt both forward and back, independent of the lifting mechanism. These developments, along with the emergence of the double-faced pallet during the same time period, allowed for tiering of unit loads. As early as 1926, the essence of the modern lift truck had been developed. Now, pallets no longer were simply a means of moving materials within the plant. High lift trucks made possible vertical stacking of unit loads and a resulting dramatic improvement of warehouse and plant storage efficiencies.
Pallet development
The pallet was developed in stages. Spacers were used between loads to allow fork entry, progressing to the placement of boards atop stringers to make skids. Eventually boards were fastened to the bottom to create the pallet. The addition of bottom boards on the skid, which appeared by 1925, resulted in the modern form of the pallet. With the bottom deck, several problems common to the single faced skid were addressed. For example, the bottom boards provided better weight distribution and reduced product damage; they also provided better stacking strength and rigidity. Lift truck manufacturers promoted the idea of using more vertical area of a plant for stock storage.
In size, skids started narrow in order to pass through ordinary doors. As facilities were rebuilt, many organizations optimized their buildings for larger pallets in order to reduce labor costs.
The earliest referenced U.S. patent on a skid is Hallowell's 1924 "Lift Truck Platform." In 1939, Carl Clark patented a recognizably modern pallet, although with steel stringers. In World War II, palleted material handling was rapidly perfected in order to transfer Allied war materials. The patent activity picked up again after the war, as inventors claimed items they improvised for the war effort. The first four direction pallet was claimed in 1945 by Robert Braun. At the end of 1948, Sullivan Stemple claimed the basic idea of a pallet designed to be used with a fork lift; the pallet was to be stamped from steel. During World War II, to reduce the resupply time of warships, the first modern disposable four-way block pallet was developed, and patented in early 1949 by Norman Cahners, a U.S. Navy Supply Officer in the ordnance depot at Hingham, Massachusetts. The first completely modern 2-direction stringer pallet was described in 1949 by Darling Graeme.
Effect on rail transport
Pallets and forklifts also provided much quicker turnaround of rail cars and ships. In 1931, three days were required to unload a boxcar containing 13,000 cases of unpalletized canned goods. When the same amount of goods was loaded into the railway trucks on pallets or skids, the identical task took four hours.
With the entry of the U.S. into World War II, the urgency for material-handling reform changed almost overnight. Palletization was regarded as an enormous opportunity to help the U.S. armed forces do more with less. Palletized loads could handle more goods with fewer people, freeing up men for military duty; it also could increase warehouse storage capacity and throughput, reducing the need for additional warehouse capacity. Pallets were used somewhat in the European theater, and were put to work extensively in the Pacific.
Standardization and regulation
Dimensions
In a pallet measurement the first number is the stringer length and the second is the deckboard length. Square or nearly-square pallets help a load resist tipping.
Two-way pallets are designed to be lifted by the deckboards. In a warehouse the deckboard side faces the corridor. For optimal cubage in a warehouse, the deckboard dimension should be the shorter. This also helps the deckboards be more rigid.
Four-way pallets, or pallets for heavy loads, or general-purpose systems that might have heavy loads are best lifted by their more rigid stringers. A warehouse has the stringer side facing the corridor. For optimal cubage in a warehouse, the stringer dimension should be the shorter.
Pallet users want pallets to easily pass through buildings, stack and fit in racks, forklifts, pallet jacks and automated warehouses. To avoid shipping air, pallets should also pack tightly inside containers and vans.
No universally accepted standards for pallet dimensions exist. Companies and organizations utilize hundreds of different pallet sizes around the globe. While no single dimensional standard governs pallet production, a few different sizes are widely used.
ISO pallets
The International Organization for Standardization (ISO) sanctions six pallet dimensions, detailed in ISO Standard 6780: Flat pallets for intercontinental materials handling -- Principal dimensions and tolerances:
| Dimensions (mm) | Dimensions (inches) | Wasted floor, ISO Container | Region |
|---|
| 1219 × 1016 | 48.00 × 40.00 | 3.7% | North America | | 1200 × 1000 | 47.24 × 39.37 | 6.7% | Europe, Asia; similar to 48x40". | | 1165 × 1165 | 44.88 × 44.88 | 8.1% | Australia | | 1067 × 1067 | 42.00 × 42.00 | 11.5% | North America, Europe, Asia | | 1100 × 1100 | 43.30 × 43.30 | 14% | Asia | | 1200 × 800 | 47.24 × 31.50 | 15.2% | Europe; fits many doorways |
North American pallets
Of the top pallets used in North America, the most commonly used by far is the Grocery Manufacturers' Association (GMA) pallet, which accounts for 30% of all new wood pallets produced in the United States. The ISO also recognizes the GMA pallet footprint as one of its six standard sizes.
| Dimensions (mm) | Dimensions (in.) | Production Rank | Industries Using |
|---|
| 1219 × 1016 | 48 × 40 | 1 | Grocery, many others | | 1067 ×1067 | 42 × 42 | 2 | Telecommunications, Paint | | 1219 × 1219 | 48 × 48 | 3 | Drums | | 1016 × 1219 | 40 × 48 | 4 | Military, Cement | | 1219 × 1067 | 48 × 42 | 5 | Chemical, Beverage | | 1016 × 1016 | 40 × 40 | 6 | Dairy | | 1219 × 1143 | 48 × 45 | 7 | Automotive | | 1118 × 1118 | 44 × 44 | 8 | Drums, Chemical | | 914 × 914 | 36 × 36 | 9 | Beverage | | 1219 × 914 | 48 × 36 | 10 | Beverage, Shingles, Packaged Paper | | 889 × 1156 | 35 × 45.5 | Unknown | Military 1/2 ISO container, fits 36" standard doors | | 1219 × 508 | 48 × 20 | Unknown | Retail |
European pallets
In Europe, the EuroPallet (an EUR standard pallet), also called a CEN pallet, is widely used in many industries. It measures 80 by 120 by 12 cm. Manufacturers of EuroPallets must be sanctioned by the EuroPallet Pallet Association (EPAL), which governs the smallest details, even which types of nails and lumber may be used. The strict standardization is based on the existence of europool pallet swap organizations - their mutual swap agreements across country boundaries does only include EuroPallets of a specific EPAL/EUR type (mostly restricted to type 1). Most freight forwarders will accept pool palettes handling the cost clearing between sender and receiver even for international transport to countries that take part in the europool system. The ongoing harmonization of freight handling within the European Economic Area has led to a decline of the europool system.
The four common sizes of EuroPallets are:
| Name | Dimensions (mm) |
|---|
| Pallet EUR | 800 × 1200 fits through many doors | | Pallet EUR 2 | 1200 × 1000 | | Pallet EUR 3 | 1000 × 1200 | | Pallet EUR 6 | 800 × 600 |
Australian Standard Pallets
The Australian Standard Pallet is a pallet size commonly found in Australia but found rarely elsewhere. It is a square hardwood pallet 1165 mm by 1165 mm in size which fits perfectly in the RACE container of the Australian Railway, but is ill suited to fitting in the standard ISO containers used around the globe. However, with two Australian pallets side-by-side, there is still 22mm 'spare'. If the pallets are loaded correctly (without any overhang), this means there is an average of 7mm on between the container wall, the pallets and the opposite container wall. While this is a tight fit, it means there is less need for dunnage (stuffing) between the container walls and the pallets.
Standard-setting organizations
A number of different organizations and associations around the world work towards establishing and promulgating standards for pallets. Some strive to develop universal standards for pallet dimensions, types of material used in construction, performance standards, and testing procedures. Other organizations choose to focus on pallet standards for a specific industry (such as the groceries) or type of material (such as wood).
ISO Technical Committee 51: Pallets for unit load method of materials handling
ISO TC 51 states its scope of work entailing the "standardization of pallets in general use in the form of platforms or trays on which goods may be packed to form unit loads for handling by mechanical devices". The Technical Committee works in conjunction with other Technical Committees focused on transportation infrastructure to develop interrelated standards. TC 51 is responsible for developing ISO Standard 6780: Flat pallets for intercontinental materials handling -- Principal dimensions and tolerances as well as sixteen other standards related to pallet construction and testing.
National Wood Pallet and Container Association
The National Wood Pallet and Container Association (NWPCA) is a trade organization based in the United States devoted to representing the interests of wood pallet and container manufacturers. The NWPCA defines its mission as helping its membership create cost-effective, environmentally-friendly solutions to customers' needs.. Towards that end, the NWPCA developed a bevy of resources to assist its membership, including the Pallet Design System (PDS), which allows users to develop and analyze pallet designs.
U.S. DOD, Dept. of Navy, Naval Sea Systems Command
This organization maintains MIL-STD-1660, the standard description of palletized unit loads for the U.S. Military and some allies.
DOD Unit loads generally use 40x48" pallets, are less than 4000lbs (1800kg), weatherproof, and stack 16' (4.9m) high. They often use steel pallets, steel straps with notched seals, outdoor plywood, and plastic film. The standard describes tests for stacking, transport, sling, forklift and pallet jack, impact, drop tests, tip, water-retention, and disassembly.
European Committee for Standardization (Comité Européen de Normalisation)
In addition to the other standards it publishes, the European Committee for Standardization, also known as the Comité Européen de Normalisation (CEN), produces standards for pallets. While the standards are voluntary in nature, many companies and organizations involved in transportation have adopted them. The major standard for pallets produced by CEN is ICS: 55.180.20 General purpose pallets
Timcon - Timber Packaging and Pallet Confederation
Timcon (Timber Packaging and Pallet Confederation) is based in the UK and is a National Trade Association that represents the timber packaging industry interests, especially the manufacturers of timber pallets, packing cases crates and export packaging.
Further information About TIMCON links and other standards can be found here
Phytosanitary compliance
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 is specified in ISPM 15.
Pallets made of raw, untreated wood are not compliant with ISPM 15. To be compliant the pallets 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 56°C for at least 30 minutes. Pallets treated via this method bear the initials HT near the IPPC logo.
- Chemical fumigation The wood must be fumigated with methyl bromide. Pallets treated via this method bear the initials MB near the IPPC logo.
Pallets made of non-wood materials such as steel, aluminum, plastic, or engineered wood products, such as plywood, oriented strand board, or cardboard do not need IPPC approval.
Pallet construction
Types of pallets
Although pallets come in all manner of sizes and configurations, all pallets fall into two very broad categories: "stringer" pallets and "block" pallets. The National Wooden Pallet & Container Association has developed a Pallet Design System PDS© to manufacture pallets. PDS© is a computer program that allows the pallet maker to generate the best suited pallet design for a specific load and generate several options for wood selections to further reduce costs. Cap3d is another program that does the same thing.
Stringer pallet
Stringer pallets use a frame of three parallel pieces of timber (called stringers). The top deckboards are then affixed to the stringers to create the pallet structure. Stringer pallets are also known as "two-way" pallets, since a pallet-jack may only lift it from two directions instead of four. Forklifts can lift a stringer pallet from all four directions, though lifting by the stringers is more secure.
Block pallet
Block pallets (also referred to as Manoj 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.
Perimeter base 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.
Quality improvements
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.
Materials used
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 liftable 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.
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 & recycle); and even the type of fasteners desired to hold the pallet together: staples or nails.
Paper pallets are often used for light loads, but engineered paper pallets are increasingly used for loads that compare with wood. Paper pallets are also used where recycling and easy disposal is important.
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, and resist weathering, rot, chemicals and corrosion. 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.
Steel pallets are strong and resist plastic creep. They are used for heavy loads, high-stacking loads, long term dry storage, and loads moved by abusive logistic systems. They are often used for military ammunition. Metal pallets make up less than 1% of the market. Materials include carbon steel, stainless steel, and aluminum. Of these, carbon steel offers excellent durability at the lowest cost. Stainless steel doesn’t require a paint coating, and is preferred for such applications as clean room environments. Aluminum offers the durability of metal at a lighter weight. Carbon steel units are relatively expensive compared to wood, and stainless and aluminum cost about 2-3 times that of carbon steel. Long term costs, however, can be lower than wood. General advantages of metal pallets are high strength and stiffness, excellent durability, bug free, no splinters, sanitary, and recyclable. Disadvantages include a higher initial price, significant weight, low friction, and susceptibility to rusting (carbon steel). Metal is primarily used in captive or closed loop environments where durability and product protection are key performance requirements. Metal units today are increasingly price competitive and lighter in weight. Primary industries that use metal pallets include automotive, pharmaceutical, lawn tractors, motorcycles, and tires
Aluminum pallets are stronger than wood or plastic, lighter than steel, and resist weather, rotting, plastic creep and corrosion. They are sometimes used for air-freight, long-term outdoor or at-sea storage, or military transport.
Alternative uses
Old and discarded wooden pallets can be used in pallet crafts.
They can also be used as a supply of free or nearly free firewood, although for safety reasons, the amount of softwood pallets burned in a fireplace should be limited in order to prevent creosote buildup. Some consider it risky to use pallets for firewood because of the possibility that chemicals or other harmful substances have been spilled on the pallet. They can also be used to build a skateboarding obstacle called a manual pad. Some pallets have even been used as barricades during amateur paintball games.
Soft wood pallets are fairly easy to take apart such that the wood is excellent once the nails are removed for use as kindling for outdoor fires. Hard wood from pallets can be reused for making outdoor items such as small animal cages as the wood from pallets is fairly weather resistant and generally very durable especially with a light coat of outdoor wood paint or stain. Hard wood from a pallet can be used for creating a short fence for keeping in small animals. Pallet wood has been recycled for use as furniture wood by at least one company. Pallet wood can be used to create fences that will last longer if painted with an outdoor stain. Pallets require being taken apart for the wood to be reused. Using a pry bar can make it easier to take apart a pallet but it still requires effort because they are well constructed. Pallet hard woods will require work equipment designed for harder woods to work with it. With sanding, staining and/or painting pallet wood can be part of a beautifully recycled wood project.
Fire hazards
Idle pallet storage can burn intensely. Plastic pallets produce a fire far more severe than wood pallets.
Steel Pallets are fireproof and provide limited openings for fire suppression sprinkler sytems.
See also
Further reading
- Brody, A. L., and Marsh, K, S., "Encyclopedia of Packaging Technology", John Wiley & Sons, 1997, ISBN 0-471-06397-5
- LeBlanc, Rick and Stewart Richardson, "Pallets: A North American Perspective", PACTS Management, Inc., www.pactsmgt.com, 2003.
- ASTM D 1185 Test Methods for Pallets and Related Structures
- ASTM D6253 Treatment and/or Marking of Wood Packaging Materials
External links
|
| |
|
|
