The article focuses on mechanism of gantry cranes and their functioning. This post is sponsored by Granada Material Handling, the gantry hoist and overhead crane manufacturing innovator servicing domestic UK and EU market.
Gantry cranes structure
The bridge crane is a major supporting structure designed to move the trolley that works with overhead loads or lifting devices. Since the mass of the bridge may constitute up to 75% of the total weight of the metal gantry crane and wind loads on the bridge may increase the load up to 85%, the design of the gantry crane for a given object is absolutely crucial.
Bridge structures are different and are selected taking into account specific conditions of the bridge, having the lowest metal content and the easiest to manufacture and assemble. By the number of supporting beams are classified into single and double-girder bridges. Depending on the required width of the served areas and access roads for vehicles with single beam and girder bridges are either console (with one or two consoles) or non-console.
On a number of cranes used in ports, one of the consoles can run the lift to the passage of ships. The height of the bridge girders is determined by the crane consoles. With the length of the console equal to 20-30% of the span, the height of beams equals 8%. When using non-console cranes the height of beams increases by 4-5%.
The bridge is usually implemented in a curved form, with construction rise in migration, which serves to compensate for the bending of driving under the influence of the loads of cargo transported. The availability rise building is particularly necessary in the taps made using hoists without brakes in the mechanism of movement. In some cases, building lifting is done only on consoles because of their great flexibility.
Building growth, equal to 50% of the maximum deflection of the bridge under the action of weight loads, is created by the respective device mounting connections or pre-bridge giving the necessary guiding profile. As a guide for freight trucks using conventional narrow-gauge railway tracks, as well as squares or strips of manganese steels having improved wear resistance. In order to facilitate the replacement of these elements when worn performed with removable fastening to the supporting structures of the bridge.
The application of designs where the wheel bogie roll directly on the shelves, I-beams, angles and other sections are made from conventional steel with a relatively low wear resistance is recommended only for cranes of simple design. The constructive use of the bridge is closely linked with the decision taken in the design of the type of trolley. Bridges imply riding the trolley at the bottom or top of the mime belts. When moving the trolleys along the lower zones (suspended trolley) these belts can be executed in the form of a monorail or sled spaced belts