Lifting Arrangements
The past three decades have seen a considerable reduction in the number
of shipyard built and rigged derricks as shipboard lifting devices and their
replacement with bought in cranes. The crane being less labour intensive,
faster operating, more easily controlled and taking up less deck area. They
do however require a higher degree of onboard maintenance.
When ordering a new ship the shipowner normally specifies the number,
safe working load, position, and any special features of the cargo lifting
devices to be fitted. Where derricks are specified the shipbuilder or an outside
specialist consultant is then responsible for the detailed design of each
derrick rig, together with the various fittings at the derricks and mast.
Where patent derricks and masts are fitted the patentee may supply the
drawings, etc., to the shipyard, who then build and erect these rigs. Masts,
except some patent types, are the responsibility of the shipbuilders; blocks,
wire, and usually derrick booms being supplied by an outside manufacturer
to the shipyard’s specification.