Single-girder cranes usually refer to single-girder bridge cranes and the English name is Single-beam Crane. The girders of the single girder crane bridge are mostly composed of I-section steel or combination section of steel type and steel plate(this also fit for double girder crane). Lifting trolleys are often assembled with chain hoists, electric wire rope hoists or hoists as parts of lifting mechanisms. they are widely used in factories, warehouses, stockyards and other occasions to lift the goods, they are prohibited to be used in flammable, explosive corrosive media environments.