Recent Trends in Ship Technology
Introduction
While efforts to develop new technologies in shipping and shipbuilding have generally been directed mainly at achieving energy conservation and labor saving, recently a diversity of broader goals have come to the fore. These include conservation of the global environment; handling modal shift-from trucking to coastwise shipping; improvement of safety and reliability; enhancing productivity; and research and development of large scale floating structure (Mega-Float).
This article summarizes how the Japanese shipping and shipbuilding industries are approaching these new tasks.
1. Conservation of the global environment
The United Nations Environmental Program is playing a leading role in the environmental conservation. Prevention of marine pollution and atmospheric pollution, two goals set forth by this Program, have particular relevance to the shipping and shipbuilding industry.
1-1 Prevention of marine pollution
1) Whereas the history of organized efforts to prevent marine contamination with oil dales back to the MARPOL 1954 Convention, the most significant topic in this context in recent years is the double-hull requirement for tankers under the revised MARPOL. This was inspired by the stranding of the EXXON VALDEZ. The revised MARPOL was adopted in March 1992 and became applicable to vessels for which a newbuilding contract was signed not before July 6, 1993. Japanese shipbuilders made several proposals regarding the technical details of the requirement and the timing of its enforcement. One of these proposals was about the mid-deck structure, which has been recognized as an equivalent alternative to the double hull.
In order to evaluate various deserving alternatives which may be proposed in the future, the causes of oil spills and what happens when one occurs need to be fully understood. To gain such an understanding, it is necessary to be able to accurately predict how a tanker hull would be damaged in a collision or when stranded, and how oil would spill out of damaged parts of hulls.
The Association for Structural Improvement of the Shipbuilding Industry in fiscal 1991 launched research projects on techniques for predicting tanker structure ruptures and oil spills. The former project was commissioned to Mitsubishi Heavy Industries, Ltd., which carried out joint experiments with the Maritime Foundation of the Netherlands, the Applied Technology Research Institute and MSC. The experiments, intended to improve the accuracy of simulations of the destruction of hull structures, were conducted on an actual vessel. MHI has also conducted damage tests with a large model and simulated damage using calculations. The latter project was entrusted to Ishikawajima-Harima Heavy Industries Co., Ltd., which conducted research on the simulation of oil spills from ruptures in a hull. Integration of the findings of the two projects is expected to make important contributions to reducing oil spills from tankers.
2) Regarding other aspects of marine pollution, the Shipbuilders' Association of Japan, ahead of all others in the world, in 1991 undertook self-restraint on the use of antifouling marine paints containing tributyltin (TBT) compounds, and has been engaged in developmental research on a new pollution-free antifouling system in collaboration with paint manufacturers.
In the IMO, the movement has begun to appear for prohibiting worldwide the use of antifouling marine paints containing tributyltin(TBT) compounds.
In order to more effectively prevent marine pollution, further cooperation among all interested parties throughout the world is strongly called for.
1-2 Prevention of atmospheric pollution
SOx and NOx are now attracting worldwide concern as main contaminants of the atmosphere. The meetings of the MEPC of the IMO in 1990 discussed the proposed targets to reduce SOx and NOx emissions by 50 percent and 30 percent respectively of their current levels by 2000. Discussions are continuing also on ways to control the emissions of halon and chlorofluorocarbons, and other air pollutants, in addition to SOx and NOx, under a new annex to the MARPOL.
1) SOx, which derives from the sulfur content of fuel, cannot be reduced unless sulfur-free fuel is used or SOx is removed from engine exhaust gas.
Some claim that high-sulfur fuel should be eliminated from the market, but removal of sulfur from the residual fraction, which is currently used as marine bunker oil, would require enormous investments in refineries, which would mean an
