Crane use and maintenance: operational errors more. Because understanding the structure of the machine, the performance is not enough (especially the new operator) 120-ton crane how much easier due to operational errors caused by fault 120 tons crane sales companies, and even cause mechanical accident. Since the crane is a special vehicle, the operator should accept the manufacturer's training, guidance, structure of the machine, there is a full understanding of the performance of 120 tons of used cranes much money, and get some experience before the operation and maintenance of operating the machine. Crane main performance parameters indicators: speed. Luffing speed: Speed ??is the steady motion amplitude state in the minimum rated load luffing plane hanging from the most significant to the horizontal displacement of the minimum amplitude of the average linear velocity. Walking speed: walking speed refers to the road status, mobile cranes hanging steady speed rated load. Rotation speed: the speed of rotation refers to a stable state of motion, the crane to rotate around its center of rotation speed.