Gantry cranes are typically used at open space warehouses, mainly for general cargo, containers and timber, for installation of prefabricated industrial and civil buildings, maintenance of hydropower plants and partial assembly in shipbuilding. They are produced mainly with hoists or with special lifting devices. General purpose crane spans are usually 4-40 m; in serving shipbuilding stocks up to 170 m. The capacity of these cranes is 3-50 tons and for maintenance of hydropower plants and the stocks reaches 400-800 m (in some cases 1,600 tons – two trolleys of 800 tons). Capacity for small as a trolley used for self-propelled electric hoists. For the installation of large items (such as shipbuilding) cranes with two trolleys are used, allowing the load to turn over weight. The manufacturing of this equipment is conducted by medium and large businesses, focusing on custom and serial equipment manufacturing, such as Granada Material Handling, a far-famed gantry hoist and overhead crane manufacturer, servicing both UK and EU markets.
Installation of cranes with a two supports
A common requirement for the installation of gantry cranes is to the ensure minimum labor intensity and cost. Gantry cranes with a two legs are usually constructed with pillars hinged to the bridge. This allows you to tap by tightening self-lifting grounds rack mounting tackles. Previously, cranes with with lifting capacity of 5 – 12.5 m performed this operation without the use of other mechanisms: the running trolley supplied cable reel devices, allowing for the period of installation to connect the drum to the drive.
Recently, these drums are provided only in cranes designed for construction works (frequent relocation). Sometimes pulley cage assembly is mounted on racks, but mainly limited device lugs to connect them. For the tightening pulley winches or other tractors are used.
Due to the wide spread of mobile jib cranes, including heavy-duty ones (100-250 tons), the lifting of the bridge gantry cranes is increasingly produced with two mobile jib cranes, and in the span of 16 – 25m with one jib crane, with running wheels, attached to the racks, which are pivotally connected to the bridge, with the rise of the crane travel paths. The installation of gantry cranes should be carried out by tightening the supports or the use of other cranes. For valves with a relatively large lifting height (12 – 13 meters), these methods are not always acceptable. A significant length of rack supports, with the initial period of installation tilt, making their contraction difficult.
In some cases (in the warehouses of timber companies) there is no possibility of using the jib cranes with the necessary parameters. In this case, the method can be used with the initial installation of the rise of support in the working position in which they are held by load distribution system. Then via pulley, upper yoke which are secured to supports girders, supports are raised and secured thereto beforehand assembled at ground level bridge.