IMO Sub-Committee on Ship Design and Construction (SDC 11)
The 11th session of the IMO Sub-Committee on Ship Design and Construction (SDC 11) took place from 13 to 17 January 2025. A new set of guidelines for emergency towing arrangements other than tankers were agreed to facilitate emergency assistance and reduce the risk of pollution. Draft amendments to the 2011 ESP Code were agreed to enable the use of remote inspection techniques and thereby enhance safety and efficiency during ship inspections. SDC 11 also progressed the revision of the explanatory notes for the Safe Return to Port regulations for passenger ships, as well as draft new requirements for non-traditional steering and propulsion systems.
Relevant for shipowners, managers, seafarers, maritime training institutes and flag states.
Meeting highlights
- Finalized draft new guidelines for emergency towing arrangements on new ships other than tankers
- Agreed on draft amendments to the “Revised Guidance on Shipboard Towing and Mooring Equipment” (MSC.1/Circ.1175/Rev.1)
- Agreed on draft amendments to the Industrial Personnel (IP) Code to increase the IP weight in stability calculations from 75 to 90 kg
- Agreed on draft amendments to the 2011 ESP Code to address the use of remote inspection techniques for close-up surveys
- Finalized a draft revision of the 2009 Code on Alerts and Indicators
- Progressed a revision of the interim explanatory notes for the Safe Return to Port concept (MSC.1/Circ.1369)
- Progressed a revision of SOLAS Chapter II-1 to address non-traditional steering and propulsion systems
- Initiated considerations of the standards for ship manoeuvrability (Resolution MSC.137(76)) based on sea trial data
- Established a Correspondence Group to facilitate the experience- building phase for the reduction of underwater radiated noise
Emergency towing arrangements
In May 2024, MSC 108 adopted amendments to SOLAS II-1/3-4 to extend the SOLAS requirements for emergency towing devices to all new ships over 20,000 GT to facilitate emergency assistance and towing operations and thereby reduce the risk of ship wreckage and pollution. In the current requirements, tankers of 20,000 DWT and above are required to have an emergency towing device, while other cargo ships and passenger ships must have a towing procedure only. The new requirements will enter into force on 1 January 2028.
SDC 11 finalized a new set of interim guidelines for emergency towing arrangements on new ships other than tankers.
SDC 11 also agreed on draft amendments to the “Revised Guidance on Shipboard Towing and Mooring Equipment” (MSC.1/Circ.1175/Rev.1), addressing fittings and supporting hull structures associated with normal towing and mooring operations, in addition to emergency towing operations for tankers. The draft amendments will align the guidance with IACS unified requirements UR A1 and A2 and IACS Recommendation No. 10, which were revised in 2022.
Consequential draft amendments to the “Guidelines for Owners/Operators on Preparing Emergency Towing Procedures” (MSC.1/Circ.1255) was agreed.
The draft new and amended guidelines will be submitted to MSC 110 (June 2025) for approval.
Industrial personnel
A new SOLAS Chapter XV and the related new Code of Safety for Ships Carrying Industrial Personnel (IP Code) entered into force on 1 July 2024. Industrial personnel are defined as persons who are on board for the purpose of offshore industrial activities performed on board other ships and/or offshore facilities.
SDC 11 agreed on draft amendments to the IP Code to align the weight used for stability calculations for ships certified according to SOLAS Chapter I with that for ships certified according to the HSC Code. Accordingly, the dimensioning weight for industrial personnel, including their PPE, will be consistently specified as 90 kg.
The draft amendments will be submitted to MSC 110 (June 2025) for approval. The draft amendments are expected to enter into force on 1 January 2028, with a three-date (contract, construction and delivery) implementation scheme for new buildings.
Safe Return to Port for passenger ships
The Safe Return to Port (SRtP) concept was introduced in SOLAS in 2010 with the intention to increase the robustness and fault tolerance of passenger ships. Even in the event of a flooding or fire casualty, the ship shall be able to return to port with its own machinery and provide a safe area for all the persons on board. The SRtP regulations apply to passenger ships with a length of 120 metres or more or with three or more main vertical zones.
SDC 11 progressed a revision of the “Interim Explanatory Notes for the Assessment of Passenger Ship Systems’ Capabilities After a Fire or Flooding Casualty” (MSC.1/Circ.1369) to facilitate uniform implementation of the concept, taking into account experienced gained.
The revision of the circular includes three main areas:
- A complete revamping of the main body of the document
- A complete revamping of the appendices, including interpretations of “remain operational”
- To include recommendations on operational aspects
SDC 11 focused on revamping the main body of the document. This includes a harmonization of inter alia the assessment process, documentation requirements, identification and differentiation between system categories, criteria for the return voyage, tests and trials.
It was agreed to include only high-level explanatory notes on operational aspects, and to submit relevant aspects to the Sub-Committees on Implementation of IMO Instruments (III) and Human Element, Training and Watchkeeping (HTW) for further deliberations.
The revision of MSC.1/Circ.1369 will continue in a Correspondence Group until SDC 12 (2026).
Enhanced Survey Programme for bulk carriers and tankers
Remote inspection techniques – for example real-time sensing devices carried by drones, remote-operated vehicles, unmanned rot arms, divers and climbers – are increasingly useful tools for supporting an attending surveyor on-site when conducting inspections.
SDC 11 agreed on draft amendments to the 2011 ESP Code to allow the use of remote inspection techniques (RITs) for close-up surveys of existing ships. RIT is defined as a means of survey of any parts of the structure without the need for direct physical access by the surveyor and should not be mixed with the concept of remote surveys.
In addition, SDC 11 agreed on a correction of MSC.1/Circ.1502 on “Guidance on Pressure Testing of Boundaries of Cargo Oil Tanks Under Direction of the Master” to reflect the tank pressure testing provisions as per the latest 2011 ESP Code (Resolution MSC.525(106)).
The draft amendments will be submitted to MSC 110 (June 2025) for approval.
New guidance for the use of RITs under the 2011 ESP Code was progressed. The work will continue in a Correspondence Group until SDC 12 (2026).
Safety netting on accommodation ladders
Rigging of a safety net from the ship’s deck to the outboard side of an accommodation ladder may be associated with risks for the crew, particularly at night or in bad weather.
SDC 11 agreed on a draft revision of the “Guidelines for Construction, Installations, Maintenance and Inspection/Survey of Means of Embarkation and Disembarkation” (MSC.1/Circ.1331) to reduce the operational safety risks of crew assigned to rigging safety nets.
A draft new MSC circular will be submitted to MSC 110 (June 2025) for approval.
Steering and propulsion
SOLAS Chapter II-1 addresses traditional steering gear arrangements with a propulsion system and a rudder. Alternatively, modern combined steering and propulsions systems (e.g. azimuth thrusters, waterjets) are, however, not addressed in the current regulatory framework.
SDC 11 progressed a revision of SOLAS Chapter II-1 to address both traditional and non-traditional propulsion and steering systems. The new requirements will be goal-based and apply to all steering and propulsion systems, both existing conventional systems and modern combined steering and propulsion systems.
SDC 11 also considered draft amendments to Resolution MSC.137(76), providing standards for ship manoeuvrability. It was agreed that new mandatory goal-based SOLAS requirements should not strengthen the required manoeuvring performance compared to the current fleet. SDC 11 further agreed to consider the appropriateness of the current manoeuvring criteria provided in Resolution MSC.137(76) by collecting and comparing sea trial data. Member States and organizations were invited to submit relevant trial data for consideration by SDC 12 in 2026.
Acknowledging that it would not be possible to meet the targeted entry into force of the SOLAS amendments on 1 January 2028 due to the manoeuvrability investigations, a roadmap for the establishment of mandatory standards for ship manoeuvrability were agreed, targeting entry into force of the SOLAS amendments and manoeuvrability standards on 1 January 2032.
Guard rails
The Load Line Convention requires guard rails on superstructures and freeboard decks to have at least three courses. With modern ship designs, some deck structures (e.g. bridge deck, living quarters decks), do not fall under the definition of “superstructure” and may be fitted with less than three guard rails. Large openings between the courses may constitute a safety hazard for the crew.
SDC 11 agreed on draft amendments to Regulation 25(3) of the Load Lines Protocol so that also guard rails fitted on structures other than superstructures are required to have at least three courses. In addition, chains fitted in lieu of guard rails should be tightened as much as practicable and be detachable.
The draft amendments will be submitted to MSC 110 (June 2025) for approval.
Unified Interpretations (UIs)
Remotely operated valves
SDC 11 agreed on a draft UI of SOLAS Regulation II-1/12.6.2 to clarify the term “remotely controlled valve”. For ships constructed after 1 January 2024, the collision bulkhead may be pierced below the bulkhead deck of passenger ships and the freeboard deck of cargo ships, provided that the pipe is fitted with a remotely controlled valve capable of being operated from the above the bulkhead or freeboard deck.
The draft UI provides illustrations of arrangements and clarifies that “remotely controlled” does not have to mean “power actuated”; in other words, that a manual deck-standing type fitted on and operated from the bulkhead or freeboard deck may be accepted as “remotely controlled” if it also meets the fail-close requirements of SOLAS Regulation II-1/12.6.2.
Emergency escape from machinery spaces
SDC 11 considered a revision of MSC.1/Circ.1511/Rev.1 related to the UIs of SOLAS Regulations II-2/13.4.1 and 13.4.2 concerning means of escape from machinery spaces. The regulations require an escape trunk to extend from the lower part of the machinery space, and the UI clarifies that the “lower part of the space” should be regarded as the lowest deck level, platform or passageway.
SDC 11 could not agree on further clarifications of the UI. There was agreement that the current UI of the “lower part of the space” should be understood as either the lowest deck level or a platform or passageway; however, due to some opposing views, SDC 11 could not conclude that the text should not be understood as “whichever is lowest”.
SDC 11 agreed to invite the Sub-Committee on Implementation of IMO Instruments (III 11) to note that the discussion raised questions related to Port State Control activities.
Fibre-reinforced plastics (FRP) within ship structures
SDC 11 considered a revision of the “Interim Guidelines for Use of Fibre Reinforced Plastics (FRP) Elements Within Ship Structures: Fire Safety Issues” (MSC.1/Circ.1574) to address experiences in application of the interim guidelines since their approval in 2017.
A Correspondence Group will progress a revision of MSC.1/Circ.1574 until SDC 12 (2026). The group will address fire safety for load bearing divisions and elements as part of the work, however excluding those contributing to global strength.
In parallel, MSC 110 (June 2025) will be invited to clarify whether or not load bearing divisions contributing to global strength should be considered as part of the scope.
2009 Code on Alerts and Indicators
SDC 11 agreed on draft amendments to the 2009 Code on Alerts and Indicators (Resolution A.1021(26)) to reflect new and updated IMO instruments approved since 2009, and to eliminate contradictions, ambiguities and redundancies.
The draft amendments will be submitted to MEPC 83 (April 2025) and MSC 110 (June 2025) for approval, and subsequent adoption by Assembly 34 (November 2025).
Underwater radiated noise
In October 2024, MEPC 82 agreed to continue the work on reducing underwater radiated noise (URN) from ships by introducing an experience-building phase (EPB) and to extend the target completion year to 2026.
SDC 11 established a Correspondence Group to identify and evaluate studies on URN emissions, consider next steps and develop a framework for the assessment of the implementation of the “Revised Guidelines for the Reduction of Underwater Radiated Noise from Shipping to Address Adverse Impact on Marine Life” (MEPC.1/Circ.906/Rev.1).
Any other business
Second-generation intact stability criteria (MSC.1/Circ.1627)
SDC 11 agreed to inform the Sub-Committee on Carriage of Cargoes and Containers (CCC) about experiences with the use of MSC.1/Circ.1627 under its agenda item “Development of measures to prevent the loss of containers at sea”.
Recommendations
As SDC is a Sub-Committee, all decisions concerning rules, regulations and dates are subject to further consideration and approval by the Maritime Safety Committee (MSC). DNV recommends that our customers monitor the outcome of MSC 110 in June 2025.
DNV class customers are encouraged to visit the Compliance Planner to monitor how upcoming statutory requirements will impact their ships.
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