International classification society Bureau Veritas and French shipowner Services & Transport have developed an Ecomax tanker design intended to address all the major causes of large oil spills. The Aframax design has two independent engine rooms, power supply systems and steering
gear, increased hull scantlings, reduced high tensile steel content, duplicated navigation equipment with off-track monitoring and full inerting of all ballast spaces.
"While smaller oil spills are getting less frequent, the occurrence of large spills due to tanker accidents is remaining constant," says Philippe Anslot, technical director of services & transports. "When we looked at the underlying causes of those spills we saw that the four main factors were machinery failure, navigation error, fire and explosion and hull damage. So we set out to design a tanker which would be much less likely to have an accident due to any of those factors. The Ecotanker is the result."
The Ecotanker design is based initially on an Aframax vessel, but studies have also been done for larger and smaller vessels. Length is slightly
increased over conventional aframaxes, but other dimensions remain much the same.
The possibility of machinery and systems failure is addressed by duplicating the engine rooms, stern tubes, propellers, steering gears and rudders. In the event of breakdown of one power plant or system, the vessel will still be able to operate in complete safety, and make 12.5 knots as opposed to 16.5 knots with both slow speed diesels functioning.
Navigational failures are tackled by building in a high level of redundancy to the equipment, applying ergonomic techniques to the bridge layout and design, and by the installation of a newly-developed Automatic Navigation and Tracking System which will warn of any off-track deviation.
Fire and explosion risk is reduced by efficient and permanent inerting of all ballast and double hull spaces, using the Hellespont-developed Vent 2D system, and by installation of double gas sampling systems in the ballast tanks adjacent to cargo spaces.
Hull failure is addressed through reducing the use of HTS to 32 per cent, from a typical 48 per cent, increased attention to fatigue details, increased scantlings particular at main deck level, and coating all ballast tanks and sensitive areas of cargo tanks.
Jean François Segretain, head of Bureau Veritas' development department, says, "Our new BV Rules 2000 are unique in giving tankers increased deck
scantlings to take account of ultimate hull girder strength. Combined with the attention to fatigue and corrosion, and the detailed attention to making survey and inspection easier, built into this design, we have come up with a 40 year world-wide ship, much stronger than those being built today."
The design has been discussed with a number of Asian shipyards. Overall build cost is estimated to be 25 per cent in excess of a standard Aframax
tanker. Anslot says, "Of course such a ship will cost more to build at present, as this design is non standard with respect to shipyards' optimised
building procedures. But should this design become a standard the overall build cost will be reduced. Also, the additional building cost is offset by other factors. We are confident in the safety and ecological advantages which these vessels offer, which result in reduced risks of major casualties. Hull and machinery and P&I costs will be lower which will reduce the impact of the building cost. We are confident that we will have the backing of major charterers, and over the life of the ship, there are savings in the overall ecological impact either directly or indirectly which will make this a viable project. After the Erika, perceptions of costs and
value have changed. We must build stronger and safer ships. We intend to work with BV to be the first to do that."