North P&I club has warned shipowners to take great care when attempting to comply with ballast-water rules by exchanging ballast water at sea. The club says in the latest issue of its loss-prevention newsletter Signals that without a meticulously prepared and implemented procedure for ballast water exchange, ships face a serious risk of a loss of stability.
According to risk management executive, Simon MacLeod, “The 2004 International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BMW Convention) needs to be ratified by just three more states with 10% of world tonnage, but many countries have already introduced their own regional mandatory ballast-water requirements – many of which are based on IMO guidelines.”
The new regulations are designed to prevent the introduction and spread of harmful marine organisms by shipping, and one of the most common ways of complying is to exchange ballast water on passage. “However, this can pose significant stability risks if a proper plan is not developed and rigorously followed on board,” says MacLeod.
North reminds shipowners that emptying and refilling ballast tanks can significantly reduce a vessel’s stability, both by reducing ballast weight but also by introducing free-surface effects. In dynamic deep-sea conditions, this can potentially lead to an angle of loll and ultimately capsize.
“An angle of loll is very dangerous situation and should be corrected as soon as possible,’ says Macleod. ‘However, the effects of corrective actions should be carefully calculated to ensure matters are not made worse.”
“Given the potential risks associated with deep-sea ballast-water exchange, it is critical that a proper plan, including the sequence in which the tanks have to be emptied and refilled and the weather limits to be observed during operation, is carefully developed and implemented,’ says MacLeod. ‘Full use should be made of the vessel’s stability book and loading computer in developing the plan.”