Cantilever-Type Gantry Crane

a hoisting crane with a bridgelike spanning structure mounted on two high supports that move along tracks on the ground. Either a hoist trolley with an operator cab or a rotary jib crane travels along the length of the span. Design considerations for the cantilever-type gantry crane include the need to compensate for deformations caused by changes in temperature and for skew of the span in relation to the supports during movement. The span may have one or, as in the case of cranes servicing ships, two cantilevers, one of them functioning as the hoist boom. The cranes are equipped with automatic holding devices in order to prevent creep caused by wind action when the crane is not in operation. Grab buckets, and sometimes lifting electromagnets, are used as the cargo-handling gear of the crane.

Cantilever-type gantry cranes are used to transfer bulk cargoes, such as coal and ores, and piece cargoes, such as high-grade rolled metal. They are used mainly in open storage areas, such as railroad freight yards, river ports, and seaports. Such cranes have lifting capacities ranging from five to 30 tons, with spans of up to 120 m and cantilever lengths of up to 50 m. Their bridges move at rates of 10-30 m per min, and the trolleys move at rates of up to 360 m per min. Grab-bucket-type cranes have capacities of 500-1,000 tons per hour and more.