MATERIALS HANDLING

the movement of raw goods from their native site to the point of use in manufacturing, their subsequent manipulation in production processes, and the transfer of finished products from factories and their distribution to users or sales outlets. In early systems of handling materials, goods were handled as single units in a discontinuous manner. These early methods treated the three basic stages of handlingmaterials collection, manufacturing, and product distributionas discrete steps, and materials were moved in individual rather than bulk units. Modern materials-handling systems, by contrast, emphasize the integrated flow of goods from the source of raw materials to final user. This can be achieved by transporting goods in large quantities and in standardized units; by handling procedures using cranes, conveyor belts, and other machines; and by the careful coordination of the movement of goods with production, processing, and distribution schedules. Recent developments in bulk transport have been directed toward keeping materials in units as long as possible, minimizing unit costs, and reducing the amount of handling necessary at all stages. Materials that are capable of being moved in liquid or gaseous form in large quantities, such as petroleum and natural gas, are most often moved through pipelines from mining sites to storage tanks and refineries, and in turn to distribution facilities. Piping networks are also used to transport slurries, which are solids (such as coal) suspended in water. The compression of natural gas and the use of large-capacity tankers have also facilitated the transportation of these materials over long distances and through major waterways. Materials handled in bulk that cannot flow through pipelines are restricted to shipping, trucking, and rail transport. Such commodities include unprocessed minerals and building materials. A third type of material consists of machine parts and other manufactured goods that can be transported in bulk to assembly lines or distributors. Materials handling equipment ranges from the simplest carts and wheelbarrows to a specialized variety of highly sophisticated cranes. Power trucks and forklifts are used for lifting bulky or heavy loads, often in connection with trailers that transport the materials along a particular route for distribution. Conveyors and monorails, powered artificially or by gravity, are also widely used in the short-distance transfer of materials within a plant and for sorting and assembly line production. Containers that range from boxes and bins to truck-size proportions help to reduce the amount of handling needed for materials and parts and to maximize efficiency through transportation in large units. Frames are also used, with or without pallets, as a way of optimizing the use of vertical storage space. Generally, optimal efficiency of handling involves a balance between the desired speed of an individual shipment and its size, weight, and composition. Innovations in trucking have produced specialized equipment for transporting refrigerated goods, bulk liquids, and gases and have developed loading methods that use pallets and wide platforms to minimize handling labour. The rail industry has produced rail cars that can be loaded from the side, flatcars, trilevel cars for shipping automobiles, and unit trains consisting of a chain of cars that carry a single bulk commodity. These trains can be loaded efficiently by cranes, hoppers, and conveyors and are capable of transporting large quantities of goods over long distances at lowered costs. Efficient transoceanic conveyance of bulk materials is typically accomplished by large cargo freighters and conference carriers. Supertankers are capable of carrying larger loads, but they also involve an increased risk of severe economic loss in case of accidents or, in transporting petroleum, of potentially destructive environmental hazards. General-cargo vessels are used for moving packaged goods along well-traveled water routes. Of all methods of transport, air travel offers the greatest advantage in speed of delivery, but it is also the highest in cost and the least capable of handling bulky or heavy shipments. Nevertheless, equipment has been developed to reduce loading time, and special containers help to maximize the efficient use of air cargo space.