Crane, method for controlling tension of steel wire rope and hydraulic system

The invention provides a crane, a method for controlling the tension of a steel wire rope and a hydraulic system, and the crane, the method and the system can be used for solving the problems of low stability and low work efficiency of the conventional stretchable arm type crane with a super-lifting winding mechanism during stretching of a lifting arm in the prior art. The hydraulic system comprises a master reversing valve, a switching valve, a check valve, a backpressure valve and a hydraulic motor, wherein the master reversing valve is used for leading hydraulic oil into or out of the hydraulic system; the hydraulic motor is used for outputting power to a traction device of the steel wire rope; a first end of the switching valve is communicated with a first oil outlet of the master reversing valve; the inlet of the check valve is communicated with the outlet of the backpressure valve; a second end of the switching valve is communicated with the second oil outlet of the master reversing valve and a first end of the hydraulic motor; and the inlet of the backpressure valve is communicated with the outlet of the check valve and a second end of the hydraulic motor.