Crane

A crane, comprising:

• a hydraulic winch;
• a wire rope that is drawn in and out from the hydraulic winch and is suspended on a sheave of a boom to be derricked with a hydraulic cylinder or a sheave of a jib provided to a distal end section of the boom;
• a safety apparatus that sets a number of turns of the wire rope drawn in and out from the hydraulic winch;
• and,
• a control apparatus that calculates a tension of the wire rope from an output torque of the hydraulic winch and a winding radius of the wire rope wound around the hydraulic winch, wherein
• the control apparatus calculates an estimated suspension load from the number of turns of the wire rope set in the safety apparatus and the tension of the wire rope,
• the control apparatus calculates an actual suspension load from a thrust of the hydraulic cylinder and a shape and attitude of the boom or shapes and attitudes of the boom and the jib, and
• the control apparatus determines that a setting in the safety apparatus is erroneous, when a difference between the estimated suspension load and the actual suspension load is out of a predetermined range.