Double girder gantry crane has strong bearing capacity, large span, good overall stability and various types; its quality is larger and its cost is higher than that of single girder gantry crane with the same lifting capacity. According to the different girder structure, it can be divided into two forms: box structure and truss structure. Generally, box structure is adopted more widely.
The truss structural form welded with angle steel or I-beam has the advantages of low cost, light weight and good wind resistance. However, due to the many welding points and the defects of the truss itself, the truss beam also has the disadvantages of large deflection, small stiffness, relatively low reliability, and frequent detection of welding points. It is suitable for places with low safety requirements and small lifting capacity.
The box-type structure is welded with steel plate, which has the features of high safety and high rigidity. It is generally used for lifting or moving large tonnage and super tonnage. At the same time, the box girder has the disadvantages of high cost, self importance and poor wind resistance.
This kind of crane mostly adopts box type and truss structure, which is the most widely used type. It can carry all kinds of finished and bulk materials, with a lifting capacity of less than 100 tons and a span of 4-39 meters. The common gantry crane with grab has a higher working level.
Common gantry crane mainly refers to the hook gantry crane, grab gantry crane, electromagnetic gantry crane, hoist gantry crane, and also includes semi gantry crane.
For assembling the hull on the slipway, there are usually two lifting trolleys: one with two main hooks, running on the track of the upper flange of the bridge; the other with one main hook and one auxiliary hook, running on the track of the lower flange of the bridge, so as to overturn and lift large hull sections. Generally, the lifting capacity is 100-1500 tons, the span is 185 meters, the lifting speed is 2-15 m/min, and the inching speed is 0.1-0.5 m/min.
The container gantry crane is used in container terminal for containers lifting and moving. After the container unloaded from the ship is transported to the yard or rear by the trailer, the container gantry crane is used to stack or directly load the container, which can speed up the turnover of
the container bridge or other cranes. The yard that can stack containers of 3-4 layers in height and 6 rows in width is generally of tire type and rail type. Compared with container straddle crane, the span and height of both sides of gantry crane are larger. In order to meet the needs of port transportation, this kind of crane has a higher working level. The lifting speed is 8-10 m/min; the span is determined by the number of containers to be crossed, and the maximum lifting capacity is about 60 m, corresponding to 20, 30 and 40 foot long containers, which are about 20, 25 and 30 tons respectively.
The span of gantry crane is an important factor affecting its own quality. In the selection, under the premise of meeting the service conditions of equipment and span series standards, the span shall be minimized.
In the work, a certain space size shall be reserved between the external dimension of gantry crane and the cargo and transport vehicle passageway of storage yard to facilitate the loading and unloading operation. When the general transport vehicle is loaded and unloaded within the span, it shall be kept at a distance of more than 0.7m from the door leg. When the spreader is not working, it shall be more than 0.5m away from the transport vehicle. When the cargo passes through the door leg, it shall be more than 0.5m away.
The working performance and service life of each mechanism of crane depend on lubrication to a great extent.