Lately, our globe faces a trend of global warming phenomena involving gradual rise of tropospheric temperature largely due to increasing emission of greenhouse gases represented by carbon dioxide(CO2). A consecutive cycle of global warming processes results in rising temperature of sea surface as well as reduced sea ice area and rising sea surface level. These changes of oceanic environment under the influence of global warming have inevitable effects on the intensity of regional storms like typhoon or hurricane. Recent research findings demonstrate that the intensity of typhoon has been gradually stronger over the last few decades than before.
Ever-intensifying power of typhoon may cause fatal risks to safety of vessels on sea. For instance, Maemi, a super typhoon struck on southern seashore of Korea on Sept. 12, 2003 and caused many personal and material damages. This typhoon caused total 62 marine accidents on southern seashore region (including 8 sunken vessels, 32 stranded vessels and 22 collided vessels).
Particularly, ever-intensifying power of typhoon has firsthand impact on anchoring ships. When a ship is anchored at certain area, it is important that external force resulting from wind, wave and tidal current should be brought into balance with counter force including holding power driven by anchor and anchor chains and thrust force of main engine, so that the ship can be secured firmly enough to resist external force without dragging anchor. Here, the higher power of typhoon leads directly to the higher external force against the ship, causing higher risks of dragging anchor. As a result, there are also higher risks of accidents due to dragging anchor, such as collision, stranding, personal injury and marine pollution.
In regard to these issues, this study focuses on investigating into anchor and anchor chain both of which account for the largest part of counterforce to stop anchoring ships from dragging anchor, with a view to examine the specification requirements of anchor and anchor chain according to standard regulations on the number of equipments for current classifications applied to every category of vessel. Then, it seeks to find out whether current specification can satisfy requirements for security of vessel from changing marine environment.
In order to achieve these purposes, this study made a case analysis on real accidents of dragging anchor in 2 training ships named ‘Hanbada’ and ‘Hannara’ to measure external force against vessel as well as counterforce of vessel at dragging anchor. And it sought to calculate counterforce of these two training ships on the basis of anchor and anchor chain according to such number of equipments as calculated by equipment number formula specified in current classifications of vessel, so that it could deduce marginal external force of dragging anchor.
Based on a series of procedures as above, this study could spot any point that would require improvement of current classification regulations. Conclusively, it is expected that this study will contribute to safe operation of vessels by implementing anchor and anchor chain to satisfy the requirements on full number of equipment for vessel from the outset of shipbuilding process.