Ring lifting crane

A ringlift crane, comprising:

• a ring which forms an annular track;
• an undercarriage and an upper carriage arranged within said ring which is connected for slewing action to the undercarriage and has a plurality of hoisting winches;
• a load-bearing element;
• rollers arranged to support the load-bearing element with rolling action on the annular track of the ring, a center point of at least one of the ring and the undercarriage forming a slewing axis;
• a counterweight having load bearing bars and arranged at one end of the load-bearing element;
• a main boom;
• a mast, the main boom and the mast being articulated to another end of the load-bearing element;
• a stay cable arranged to connect a top of the mast to the counterweight in an operating condition of the crane;
• a changeable-length cable stay arranged to connect a head of the main boom to the top of the mast;
• a stay support articulated on the mast on a side of the mast which is inclined toward the counterweight, a free end of the stay support being connectable to the stay cable of the mast for lifting the top of the mast into an operating position;
• a further changeable-length cable stay arranged to connect a free end of the stay support to a free end of the load-bearing bars of the counterweight;
• and
• an auxiliary hoisting winch arranged on the load-bearing element, a free cable end of the further changeable-length cable stay being connected to the auxiliary hoisting winch, whereby the top of the mast, when connected to the head of the main boom by the changeable-length cable stay, is liftable into a relaxed position by reducing the length of the further changeable-length cable stay so that tension in the stay cable is released in the relaxed position whereby one end of the stay cable is disconnectable from the stay support and connectable to the counterweight in the relaxed position.