Loss of containers is a major problem for the operators of container ships. From information on the actual wave condition, ship motions and loading, Det Norske Veritas (DNV) is developing a surveillance system that will provide operators with advice on how to operate their ships safely. Based on predefined acceptance criteria, the new decision-support tool helps to minimise damage to the ship and to avoid loss of containers.
Presently “good seamanship” is a basis for Classification. However, with the expected increase in size, speed and complexity of the vessels, experience shows that the actual loads and motions may exceed the traditional basis for design under severe weather conditions. This may be realized too late by the vessel crew, which may lead to structural damages and loss of containers. The problem of loosing containers may become even more serious as the size of the container vessels increase. Presently, the largest container vessel in operation is more than 6500 TEU. There are vessels on order of about 7500 TEU.
The new surveillance system - Active Operator Guidance (AOG) is currently being tested as a prototype. The wave condition is continuously monitored by the latest Miros wave radar technology. The surveillance system uses ship motions and wave loads predicted by the analysis tool WASIM, and checks that limits of hull loading, impact pressure, water on deck, motions and accelerations are not exceeded. For ships operating at 25 knots, voluntary speed reduction and course alterations are means to minimise the hull loading and motions of vessels. This will reduce the risk of structural damage and loss of containers. Future modules for the AOG are planned to include decision support for route planning, trend analyses and advice on actual situation for the vessel, and will ultimately be integrated into the bridge system.