There is growing concern due to the fact that fatigue cracking on ship sides has been brought to the attention of the container ship industry. Through increased focus, training and know-how, the seagoing personnel themselves may play a key role in revealing and dealing with the problem.
Side shell cracking has been a well-known problem on large oil tankers for a number of years. As the world’s leading class society within the crude-oil transportation sector, DNV has for several decades increased the knowledge of how to prevent these problems at the design stage and under construction.
For existing ships with inadequate fatigue life, a good strategy is to calculate the fatigue life retrospectively, systematically inspect the areas where the fatigue life is about to expire, and then map and report the findings. Repairs and improved design details may then be planned and budgeted for. This will give the operator control of the situation rather than being caught with an oil spill in port.
The cause of side shell cracking in tankers is somewhat different to that in container ships, but the cure is much the same. A lot can therefore be gained by applying the big ship experience relating to tankers to container ships.
A few years ago, DNV introduced the Container Express Program The concept is simple. The idea is to discover potential problems as early as possible to allow for a controlled process to deal with them. A side shell crack may be discovered due to an oil leak on the ship side once the damage is done. Alternatively, it can be inspected according to a plan, by people who know what to look for, thus providing an early warning and allowing time to plan and budget.
A key factor for success is to provide training and detailed information to senior officers and superintendents.
Recently DNV and Seagull, a leading developer of a computer-based program for the onboard training of seafarers, developed a tool for hull and structure inspections onboard container vessels. This tool pays a lot of attention to coating and critical areas and provides plenty of visual advice in a language intended for the onboard personnel.
By combining traditionally developed experience of other ship types with the development of these new tools for container transportation, DNV aims to be ahead of the problems that may occur and to allow risks to be managed in time.
DNV’s share of the container ship market is growing continuously. It has doubled over the last few years, and is now at about 5%.