Crane safety devices: leg locking mechanism. Except when buying 50 tons crane accident, leading to the legs vertical cylinder high-pressure hose or pipeline rupture or cutting the price of 50-ton crane, hydraulic system bidirectional hydraulic lock cylinder block can block two outrigger pressure oil chamber, so Outrigger indented or thrown, to ensure the safety of lifting operations. Crane of structure: by lifting the nature points. Mobile cranes, tower cranes, mast crane. According to the structure, the crane can be divided into small light lifting equipment, bridge type (bridge, gantry crane), the arm frame (self-propelled, tower, gantry, rail-style, floating boat-mast cranes), cable type.