The large bridge type grab ship unloader is equivalent to a bridge crane. The large bridge type grab ship unloader uses a moving trolley to drive the grab bucket to grab materials from the cabin and unload them into the onboard hopper. The bulk intermittent (or periodic) unloader is mainly composed of a metal structure, mechanism, and electrical control system. The metal structure mainly includes a main beam, door frame, tie rod, etc; The mechanism of a large bridge type grab ship unloader mainly includes a lifting mechanism/opening and closing mechanism, a small car walking mechanism, a large car walking mechanism, and an arm pitching mechanism.
The electrical control system of a large bridge type grab ship unloader mainly includes power distribution system, drive and control system, protection system, etc. The bridge type grab bucket unloader can be divided into self-propelled and towed types according to the trolley drive mode.

The working characteristic of a large bridge type grab bucket unloader is to grab bulk materials from the cargo hold through the individual or combined action of the lifting/opening/closing mechanism and the trolley running mechanism, and provide them to the dock conveyor system through the funnel on the unloader, realizing the operation of the dock front unloader.
The main technical parameters of the large bridge type grab ship unloader include productivity, outward extension distance, track gauge and base distance, lifting height, maximum wheel pressure, etc. The rated production rate is 400t/h~5000t/h, and the outward displacement distance needs to be determined comprehensively based on factors such as the maximum design ship width, the distance between the water side track and the dock front edge, and the thickness of the rubber rail.
Large bridge type grab ship unloaders are the most important equipment for loading and unloading bulk cargo ships both domestically and internationally, especially for coal and ore loading and unloading terminals. They have high loading and unloading efficiency and are widely used in various ship types. In recent years, 400000 ton ore ships loaded and unloaded at ports such as Qingdao Port and Dalian Port have all been bridge type and chain type grab ship unloaders, as well as continuous type grab ship unloaders. Compared with continuous type grab ship unloaders, bridge type grab ship unloaders have mature manufacturing technology, high reliability, strong adaptability to different types, and are easy to use and maintain. The main disadvantages are that the grab bucket is prone to generating dust during operation, and the grab bucket and traction wire rope are prone to wear and tear. The clearance volume of bulk cargo is larger than that of continuous equipment, and the self weight is larger than that of continuous unloaders under the same ship discharge efficiency. The wheel pressure is also high, which puts high pressure on the dock structure