Feature 4 | CARGO HANDLING AND DECK EQUIPMENT
Design should be defined by ship’s cargo not by default
By starting from an understanding of a ship’s cargo profile, a container ship’s utilisation rates can be maximised and its environmental impact minimised, according to Cargotec’s Dry Cargo business line sales director Ari Viitanen and senior naval architect Kari Tirkkonen
T
raditionally, important factors when designing a container carrier are its hull dimensions, fuel
efficiency and visibility from the bridge. Te decisions made about these factors at the beginning of the ship building process pre-define the framework for the cargo handling system, and this can mean that the resulting features of the cargo handling system are determined by default rather than by design. However, this approach underestimates
the vital role that the cargo handling system plays in the environmental impact of a container ship and its cargo. Te more efficient the cargo handling system, the greater the number of TEUs a ship can carry, which in turn reduces the emissions per carried TEU, and subsequently per transported commodity. Therefore, we believe that the traditional design process effectively starts from the ‘wrong end’. Cargotec defines cargo profile as the
distribution of containers onboard a ship in terms of container sizes and container weights on a certain route. Our proposal takes a whole-ship approach and works forward from the cargo profile. But, this must happen at an early stage of the ship project, before any restrictive decisions have been made. As a result of
this
forward-thinking approach, it is possible to improve the specified loading ability and the efficiency of the entire system.
A tool for cargo profile analysis Practical experience from existing ships already supports our approach, but it is Cargotec’s wish to establish evidence that proves that an efficient cargo system really counts when addressing environmental issues. To do this, Cargotec has signed a co-operation agreement with the ship design evaluation specialist, Safety at Sea, based in
112 MacGregor takes a different approach to cargo handling
Efficient use of space is efficient use of energy Productivity of container ships can be measured using several indicators, such as maximum capacity and utilisation rate, fleet utilisation, and operating cost per TEU.
loadings for GM (metacentric height) and ballast scenarios to keep hull stability satisfactory. And this is done without being able to take into account, or the specification of, the actual capability of the cargo handling system.
The Naval Architect September 2012
Glasgow, Scotland. Te purpose of the co-operation is to establish a statistical method and tools for analysing the cargo profiles of our customers’ newbuildings, and to use these profiles to define the cargo handling system requirements for these vessels. From a design point of view, the analysis
tools provide the means to produce the optimal container stack arrangement and optimal stack container weight distributions for each cargo profile. Te tools are based on statistical reviews of the cargo moved onboard and enable the user to compare the productivity of different cargo systems and ship concepts.
Traditionally, vessels are designed to carry
a maximum number of containers loaded in the holds and on deck, and usually the method for deciding this figure is based on two considerations: the total number of boxes allowed by visibility rules from the bridge, and the homogeneous loading limited by the displacement of the hull. These considerations can lead to
an arrangement where the utilisation rate of the vessel’s cargo space can vary significantly, depending on the actual cargo mix. Additionally, if designers do not have information about the intended cargo profile, they are forced to undertake several calculations of different homogeneous
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