ClassNK Advocates Speed Gap Monitoring to Optimize Fuel Efficiency in Heavy Weather

ClassNK’s latest Technical Journal includes a summary of recent developments on safety measures for ammonia and other alternative fuels, and also reveals a ‘fuel-saving tip’ for ships operating in rough sea conditions.
The sections on ammonia feature an update on the International Maritime Organization’s (IMO) Guidelines for the Safety of Ships Using Ammonia as Fuel as well as a review of the classification society’s own initiatives.
ClassNK’s rough seas fuel-saving tip is a detailed paper aimed at a highly technical audience, rather than those looking for a quick fix to cut bunker bills. Essentially, it notes that ‘there seems to be a common practice in the shipping industry to lower the main engine speed when encountering rough seas’ – but the amount by which the speed is reduced is ‘usually left to the individual ship crew’s experience’. Instead, the ClassNK paper advises that crews should monitor the ‘speed gap’ between the actual speed and the ‘commanded speed’ (i.e. the desired engine speed set by the vehicle’s control system) and then lower the commanded speed ‘until the gap disappears’.
The paper concludes: ‘By properly adjusting the main engine speed order in heavy weather conditions, a significant amount of fuel can be saved. In addition to the economic benefits, eliminating the speed gap reduces the likelihood of turbocharger failures and damage to other components exposed to exhaust gases.’