The London-based International Maritime Organisation is expected to adopt the finalised revised phase-out schedule on single-hull tankers at its 46th session of the Marine Environment Protection Committee (MEPC 46) between 23-27 of this month.

"The first, formal step towards a global timetable for the accelerated phasing-out of single-hull oil tankers was reached at the MEPC 45. The necessary amendments to MARPOL 73/78 will be finalised at the forthcoming meeting," said Rossid Musa of Marine Department.

Rossid who was speaking at recent Marine Environmental Pollution Seminar organised by Malaysian Shipowners' Association the decision will pave the way for the adoption of a revised regulation 13G of MARPOL to accommodate the swiftest possible introduction of new rules.

The MEPC 45 working group (in October 2000) has categorised tankers into three major groups.

The first category refers to Pre-MARPOL oil tankers of 20,000 tonnes deadweight and above carrying crude oil, fuel oil, heavy diesel oil or lubricating oil as cargo, and of 30,000 tonnes deadweight and above carrying other oils, which do not comply with the requirements for protectively located segregated ballast tanks.

The draft revision of MEPC 45 sets out two clear alternative schemes (A and B) for phasing-out single-hull tankers. Both schemes would see Category 1 vessels phased-out progressively between 1 January 2003 and 1 January 2007, depending on their year of delivery.

The Category 2 refers MARPOL tankers with same size of Category 1, which comply with the protectively located segregated ballast tank requirements. Tankers in this category built in 1986 or earlier would be phased out after their 25th year of operation under both schemes, (A and B. Ships built after 1986 would be phased out between 2012 and 2015 under alternative A and between 2012 and 2017 under alternative B.

The working group also agreed that continued operation of Category 2 oil tankers beyond 2010 should only be permitted to high quality ships which had been subject to a Condition Assessment Scheme (CAS) which generally depending on the physical condition of the vessel, past performance and possible improvements in survey and inspection practice.

It was stressed that the introduction of a CAS should not undermine the Enhanced Survey Program (ESP) system under resolution A. 744 (18) and that the scheme would assume that vessels should pass their ESPs.

The third category oil tankers refer to an oil tanker of 5,000 tons deadweight and above but less than the tonnage specified for Category 1 and 2 tankers.

For Category 3 tankers, both schemes (A and B) entail progressive phasing out. Tankers built in or before 1987 phased-out between 2003 and 2013. Ships built after 1987 would be phased out between 2013 and 2015 for ships under scheme A and between 2013 and 2017 under scheme B.

Rossid also said the new-build tankers are covered by Regulation 13F.

If they do not comply with Regulation 13F, their owners must decide whether to convert them to the standards set out in regulation 13F, or to scrap them. This regulation requires all new tankers of 5,000 dwt and above to be fitted with double hulls separated by a space of up to 2 metres (on tankers below 5,000 dwt the space must be at least 0.76m).

As an alternative, tankers may incorporate the "mid-deck" concept under which the pressure within the cargo tank does not exceed the external hydrostatic water pressure. Tankers built to this design have double sides but not a double bottom. Instead, another deck is installed inside the cargo tank with the venting arranged in such a way that there is an upward pressure on the bottom of the hull.

Other methods of design and construction may be accepted as alternatives "provided that such methods ensure at least the same level of protection against oil pollution in the event of a collision or stranding and are approved in principle by the MEPC based on guidelines developed by the Organization."

For oil tankers of 20,000 dwt and above new requirements have been introduced concerning subdivision and stability. 

The amendments also considerably reduce the amount of oil, which can be discharged into the sea from ships (for example, following the cleaning of cargo tanks or from engine room bilges). Originally oil tankers were permitted to discharge oil or oily mixtures at the rate of 60 litres per nautical mile. The amendments reduce this to 30 litres.

For non-tankers of 400 grt and above the permitted oil content of the effluent which may be discharged into the sea is cut from 100 parts per million to 15 parts per million.