Method for using a two-drum crane for raising or lowering a load

摘要

The disclosure involves a crane having a main hoist drum and an auxiliary hoist drum for handling a load under normal and emergency (the latter actual or simulated) conditions, respectively. The latter condition involves a main hoist which is inoperative because of a failure or by intent. The auxiliary hoist drum is wrapped with about twice the length of cable as the main drum and can move the load up or down, irrespective of load position if and when the main hoist becomes inoperative. Also disclosed is a novel method for moving a load. Steps include maintaining one drum in a non-rotating mode and rotating the other drum. An improved crane load block is also disclosed to have "floating sheaves" which help prevent excessive fleet angles.