Shipboard cranes of various types and capacities are still required for multi-purpose cargo vessels, geared bulk carriers, feeders, reefers, heavy lift vessels and some forest product carriers. Manufactures offer crane designs and special handling attachments (container spreaders, rotators and grabs) to suit all dry cargo trades.
Computer-based cargo spotting systems enable even relatively unskilled operators to cope with the pendulum effects and centrifugal forces. They also help in keeping containers or other cargo units constantly aligned with a given axis, regardless of slewing motion and other external forces. Such electronic aids substantially improve productivity.
Some owners report a doubling of the hourly container-handling rate. Other benefits include: reduced operator fatigue, improved safety and lower cargo and ship structure damage.
Among the design criteria in specifying cranes for geared container ships and multipurpose dry cargo tonnage is safe working load (SWL) of 36-40t. A two-wire configuration with widest possible jib head is preferred for easier cargo spotting and increased stability. Another important factor is the need to create the maximum possible container stowage space on deck. Thus the crane is expected to occupy no more than one container slot (2.4m with); a small minimum luffing radius (less than 2.4m) is also valued so that containers stowed closest to the crane can be handled. Internal access to the crane is essential, and cargo lighting will normally have to be fitted at the top of the crane housing.
Forest product carriers are required to transport and handle a variety of cargoes, including packaged sawn timber, logs (bundled or loose), and refined products such as pulp, paper and boards. The cranes must therefore be suitable for working with special attachments like clamps, multi-lifts and frames.
Mast cranes for dedicated heavy lift and project cargo vessels are a specialty of the Dutch company Huisman-Itrec which has supplied over 30 such units with lifting capacities up to 800t since developing the concept in the early 1980s. Deliveries have included eight 275t capacity cranes for a recent newbuilding class for BigLift shipping. Each of the four 8874dwt vessels in the series is equipped with two rotating mast cranes, one located aft to port and other forward to starboard. Working tandem, the pair can handle loads up to 500t, the relatively long jibs securing outreach approaching 28m. See also Cranes.