Wood pallets have traditionally been the way in which material is moved from vendor to customer and then onto the consumer. The wood pallet sits in warehouses and stores throughout the world. In the US there are millions of pallets in use every day and the vast majority is made from wood. For the manufacturer of the wood pallet, there are voluntary guidelines that have been developed by the National Wooden Pallet and Container Association (NWPCA) to ensure that every pallet that is used in the shipping and storing of materials is as safe as possible.
Standard for Wood Pallets
The National Wooden Pallet and Container Association has developed a uniform standard for the wood pallet that explicitly describes how a wood pallet should be manufactured, the necessary performance of the pallet, and the how a wood pallet should be sanitized. This standard was approved by the NWPCA in May of 2012 and gives anyone who is involved with wood pallets the information that they need to deal with any situation involving pallets.
Manufacture of Pallets
The NWPCA guidelines aim to give a minimum quality requirement for wood pallets. The section of the guidelines referring to the manufacture of pallets includes descriptions on components, definitions, and description of fasteners, dimensional tolerances, moisture content levels, and information on the repair and remanufacture of pallets. There are two classes of pallets; stringer pallet, which uses a frame of three or more parallel pieces of timber, and the block pallet, which uses both parallel and upright stringers for more efficient handling.
The pallet can be made of a number of different components; lumber, plywood or OSB (oriented strand board), wood-based composites, and engineered wood components. The components should be used with fasteners such as driven nails and staples, steel carriage bolts, wood screws, and lag screws. There should be a minimum number of fasteners for each connection, based on the width of the component involved, and the placement of those fasteners is covered in the specification.
The repair of pallets is important as it reduces the number of pallets being sent to landfills and it is a benefit to companies that use pallets as it reduces the cost of purchasing or manufacturing new pallets. The specification gives detailed information as to how to repair the pallet given any number of scenarios, such as missing wood, splits, delamination, or twisted blocks.
Performance of Pallets
Each pallet should be able to do the job it was designed to do, and as such the NWPCA specification gives companies information on the performance of a pallet, given a number of conditions. The testing of pallets is defined by an ISO test method; ISO 8611-1:2011 specifies the test methods available for evaluating new flat pallets for materials handling. The test methods are split into groups for nominal load testing, maximum working load testing, and durability comparison testing. There are two distinct types of load test: proof testing and testing to destruction. The most common pallet testing is testing to destruction, as it is only possible to measure a pallet load safety factor if the item under test has exceeded safe working load up to breaking load.
Sanitation of Wood Pallets
The NWPCA specification describes the phytol sanitation of wood pallets. The NWPCA indicates that all pallets should conform to the International Standards for Phytosanitary Measures Publication No. 15 (ISPM 15). This standard has been adopted by the US and a growing number of countries. The ISPM 15 was developed to reduce the risk of introduction and spread of quarantine pests associated with the movement in international trade of wood packaging material made from raw wood. The treatments of wood include heat treatment, which specifies the heating to 56 C for a minimum duration of 30 continuous minutes. Other treatments include the use of methyl bromide, which is used to fumigate the wood over a period of 24 hours.