Fuel Efficiency At The Cost Of Negative Effect



Olivier van der Kruijs shares his experiences from the audits on more than one hundred container vessels last year.

The modern container ships are designed to increase capacity and also improve energy efficiency and environmental performance.  The rise in fuel prices and lower freight rates have forced ship owners and operators to audit fuel usage.

Fuel efficiency monitoring can be achieved by using computer and communication software which monitors and analyses the ship’s performance and operational parameters in real time.  One study suggested that fuel consumption could be reduced by as much as 5% using this technology.

A point of attention during these surveys is the requirement to review maximum permissible forces, there are limitations resulting from the strength of the container itself.  It is important to appreciate that there is no safety margin on these limits.  Theoretically, a container may thus distort as soon as these force limits are exceeded.

It has become apparent that during the voyage, the ship is sometimes instructed by the owners (or the charterers) to make adjustments to improve fuel efficiency.  These (unplanned) adjustments of draught and trim often at various occasions could lead to a situation whereby the ship left port with the calculated lashing forces being within design limits, but exceeding the limits at a later stage when the trim adjustments were made.

However, if the ship was to encounter its “design motions criteria”, damage to the container stacks and cargo could occur, thus as an indirect result of saving fuel.

Source: BMT Group