ABSTRACT
Lifting gear has become a major casualty of modernization. The Derrick rig has become nearly a memory, being overcome by the more versatile deck cranes, container gantry cranes and of course by the ramps for the unit load systems. The most widely used derricks in the marine industry are of a welded structure, consisting of either three or five welded sections of tubular steel. Wooden derricks, which generally lifted only up to three tonnes, have been superseded. Some heavy lift derricks have the spider band manufactured so that the lugs opposite each other are attached to a yoke piece that passes through the derrick, providing additional strength in working. The function of the derrick is to raise, transfer and lower weights. Derricks are topped when the vessel is in a loading or discharging port. Once lifting/cargo operations are complete and the ship is prepared for sea, the derrick booms will be lowered and stowed in crutches, mounted above the deck.
