The presetn invention use an auxiliary hoist(22) to realize many kinds of manufacturing procecess, the auxiliary hoist(22) provided on a rotating part(4) of the crane and equipped of an auxiliary cable(23) of diameter lower than lifting and hoist cables. The spaning operation includes: installing the cable on the hoist; mounting a temporary sling(24) for temporary retention of a boom(9), and mounting a tie rod line for retention of the boom, and for retention of the structure mounted on the balance arm.