The IMO’s Sub-Committee on Stability, Load Lines and Fishing Vessel Safety (SLF) continues its work to improve international regulations.

Following the IMO’s completion of its intense work on the revision of technical regulations for the 1988 Load Line Protocol and harmonisation of passenger and cargo ship provisions in chapter II-1 of SOLAS-74, the SLF’s 48th session was held during the week from 12 to 16 September 2005 on a note of consolidation. DNV was represented by four advisors to the Norwegian delegation. This report highlights agenda items assumed to be of special interest to DNV and DNV’s customers.

Revised SOLAS chapter II-1:
Development of explanatory notes
Although the revised chapter is scheduled to come into force in 2009, the industry is in immediate need of such guidance since the design of new ships, in particular passenger ships, is starting now. A large number of issues needing clarification have been collected by the SLF’s damage stability working group since the previous session.

DNV has contributed significantly to this work, based on queries received from shipowners and yards. The collected items were discussed thoroughly during the session and accepted for inclusion in the notes or for further deliberations.

The most prominent issues are related to the intermediate stages of flooding, calculation of cross-flooding and equalisation, and the definition of escape routes that must be rendered usable. Construction and testing principles for watertight bulkheads and doors are to be included as well as principles to apply when permitting watertight doors to be left open. Guidance on improved damage control information, including the use of computers, is also to be developed.

Revision of the Intact Stability Code
There is general agreement between IMO Members that some basic intact stability requirements should be made mandatory. The code will be split into two parts. The work at this session was largely to determine what provisions should go into each part. The mandatory part will contain basic provisions relating to intact stability criteria for passenger ships and cargo ships, the weather criterion, including guidelines for the use of model tests, and additional criteria for certain ship types.

The voluntary part will include guidance on intact stability criteria for offshore supply vessels, special purpose ships, fishing vessels and pontoons as well as guidance on the preparation of stability documentation and the approval of loading computer software. Further discussions on the substance of the mandatory part have now been cut short in order to prepare a final draft text for the next session. The revised IS Code is expected to enter into force as a mandatory instrument in January 2009.

Supply ships: Review of the LHNS and OSV Guidelines
The old OSV Guidelines (resolution A.469(XII)) need an overhaul to reflect various cargo ship provisions, such as watertight subdivision, that have been included in SOLAS-74 since 1981. It has also been decided to include provisions for the carriage of limited amounts of hazardous and noxious liquid substances (LHNS) in the revised document.

As for stability, it was decided to introduce a minimum damage length while maintaining the one-compartment standard. The requirements as to watertight doors and the design of bulkheads are to be aligned with chapter II-1 of SOLAS-74. It is also proposed to introduce a ‘Document of Compliance’ and to maintain the existing definition of ‘Offshore supply vessel’. A draft MSC resolution will be forwarded to the IMO’s Maritime Safety Committee (MSC) for possible adoption. DNV’s Supply Vessel and SF rules are expected to require an update if the revised guidelines are approved.

Passenger ships: Damage stability in excess of the current standard
Independently of the work on revising SOLAS chapter II-1, the MSC had requested the development of application parameters in the form of damage scenarios for a safe return to port either under own power or under tow as well as for ensuring time for an orderly evacuation should that threshold be exceeded.

Among the items concluded were that most of the MSC’s requests would be adequately covered by the revised chapter without the introduction of additional requirements, while a threshold for the possibility to return to port could be developed based on the ‘minor damage’ already found in the revised chapter. Further development related to the flooding prediction was considered not to be practicable in the near future. Accordingly, the SLF will continue to work on criteria to ensure a safe return to port.

Harmonisation of damage stability provisions in other IMO instruments
A list of possible IMO instruments containing deterministic damage stability provisions to replace the probabilistic requirements in the revised chapter II-1 of SOLAS-74 was up for evaluation. It was concluded that the 2000 HSC code, the OSV Guidelines, the MODU Code, the provisions in MARPOL 73/78 and the IBC and IGC Codes should remain deterministic, due to practical limitations when developing and using the probabilistic principles for these types of ships.

The SPS and INF Codes were found to be suitable candidates for harmonisation while regulation 27 of the 1988 LL Protocol will need further consideration – but only for the ‘B minus’ ships. The work will be continued at the next session.

Revision of the technical regulations of the 1966 LL Convention
There were only a few items up for discussion, the most significant being the application of the bow height requirements for self-elevating MODUs. The MODU issue was recognised, but it was agreed that it would need to be considered in connection with the ongoing revision of the MODU Code in the DE sub-committee. No further revisions are required for the time being, with the possible exception of regulation 27.

It is possible, however, that a proposal to keep the load line item on the SLF’s agenda for the purpose of discussing sea loads on hatch covers will be submitted to the MSC.

HSC and DSC: Review of the 2000 HSC Code and amendments to the DSC Code and the 1994 HSC Code
In addition to a number of changes to the 2000 HSC Code of an editorial nature, significant changes to the damage stability requirements had been put forward, in particular with respect to bottom-raking damage. The general sentiment was that the damage definitions in the current text, which have only been in force for a few years, should remain unchanged for now. Some editorial matters will be forwarded to the DE sub-committee.

Open-top containerships: Tonnage measurement
A number of proposals relating to the view that open-top containerships are unfavourably treated under the 1969 TM Convention were up for discussion. It was agreed that the existing provisional formula for a reduced GT for these ships could be revised and that such reduced tonnage is also to be inserted in the ‘Remarks’ column in the TM certificate in the future.

Special purpose ships: Review of the SPS Code
The IMO has considered that the SPS Code, resolution A.534(13)), needs to be updated to reflect the various amendments to the cargo and passenger ship provisions in chapter II-1 of SOLAS-74 over the years. There were indications that the time might be right to consider making the code mandatory. Due to its workload, the SLF decided to defer further work to the next session.

Safety aspects of ballast water management
It was discussed whether limited deviations from the intact and damage stability requirements could be accepted during ballast water exchange. The SLF concluded that no transitory deviation from the stability standards should be permitted.