Overhead double-girder crane is an important tool and equipment for mechanization and automation of production process in modern industrial production and lifting and transportation. Therefore, double-girder bridge cranes are widely used in indoor and outdoor industrial and mining enterprises, iron and steel chemical industry, railway transportation, port terminals and logistics turnover and other departments and places.

The double-girder overhead crane is a hoisting equipment that is horizontally mounted over workshops, warehouses and stockyards for material hoisting. Because its two ends sit on tall concrete columns or metal supports, it is shaped like a bridge. As the name suggests, it consists of two main beams. The bridge frame of the double-girder bridge crane runs longitudinally along the tracks laid on the elevated sides on both sides, which can make full use of the space under the bridge frame to lift materials without being hindered by ground equipment. It is the most widely used and the largest number of hoisting machinery.

All electrical equipment enclosures of overhead cranes should be grounded. If the trolley track is not welded on the main beam, measures should be taken to weld the ground wire. The grounding wire can be galvanized flat iron with a cross-sectional area greater than 75mm2 or bare copper wire with a cross-sectional area of 10mm2 or galvanized round steel with a cross-sectional area greater than 30mm2. There should be more than two grounding positions for the driver’s cab or the crane body. The grounding resistance between any point on the crane and the neutral point of the power supply should be less than 4Ω.