IMO Sub-Committee on ship design and construction (SDC 12)

The 12th session of the IMO Sub-Committee on Ship Design and Construction (SDC 12) took place from 19 to 23 January 2026. SDC 12 finalized the revised Explanatory Notes for the Safe Return to Port concept, the new guidelines for the use of remote inspection techniques under the 2011 ESP Code, and the interim guidelines for the use of fibrereinforced plastics in ship structures. New initiatives were also considered, including performance standards for engine control room alert management as well as a work plan for the development of a safety framework for emerging technologies such as wind propulsion, battery power and nuclear reactors.

Information for: Ship owners, managers, seafarers, maritime training institutes and flag states.

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 12 finalized 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 experience gained.

The draft revision of the Explanatory Notes expands the scope of the guidance beyond that set out in MSC.1/Circ.1369 to cover the full life cycle of passenger ships – from design and verification to testing and operational aspects, including the following:

• Essential aspects to be addressed in the pre-contract/early project phase
• Design requirements and acceptance criteria for all SRtP and OEA systems
• The SRtP assessment process
• Documentation, verification and approval
• Tests and trials
• On-board documentation for SRtP and OEA
• High-level operational aspects

The new draft of the revised guidance “Explanatory Notes for Safe Return to Port and Orderly Evacuation and Abandonment after a Fire or Flooding Casualty” will apply to ships:

• for which the building contract is placed on or after1 January 2028, or
• in the absence of a building contract, the keel of which is laid or which is at a similar stage of construction on or after 1 July 2028, or
• the delivery of which is on or after 1 January 2032.

The draft revision of the Explanatory Notes will be submitted to MSC 111 (May 2026) for approval.

The Sub-Committees on Human Element, Training and Watchkeeping (HTW) and Implementation of IMO Instruments (III) will be invited to consider whether existing instruments on operational aspects need to be amended to support the new Explanatory Notes.

2011 ESP Code

Remote inspection techniques

Remote inspection techniques – for example real-time sensing devices carried by drones, remote-operated vehicles, unmanned robotic arms, divers and climbers – are increasingly useful tools for supporting an attending surveyor on-site when conducting inspections.

MSC 110 approved draft amendments to the 2011 ESP Code to allow the use of remote inspection techniques (RIT) for closeup surveys of existing tankers and bulk carriers. An RIT is defined as a means of survey of any part of the structure without the need for direct physical access by the surveyor and should not be mixed with the concept of remote surveys.

SDC 12 finalized new draft guidelines for the use of RIT under the 2011 ESP Code.

The draft of the new guidelines will be submitted to MSC 111 (May 2026) for approval in conjunction with the adoption of the related draft amendments to the 2011 ESP Code.

Fraction detection procedures

SDC 12 agreed to draft an amendment to the 2011 ESP Code to harmonize the fracture detection procedures between bulk carrier and oil tankers by including the option for “other equivalent means” to paragraph 5.4.2 of both parts A and B of Annex A.

The draft amendments will be submitted to MSC 111 (May 2026) for Approval in Principle and is planned to be adopted by MSC 114 (2028).

Means of access to the cargo hold of single-side skin bulk carriers

SDC 12 agreed on draft amendments to the “Technical provisions for means of access for inspections” (Resolution MSC.133(76), as amended by Resolution MSC.158(78)) to align the provisions regarding the use of portable ladders with the requirements of the 2011 ESP Code.

The draft amendments will be submitted to MSC 111 (May 2026) for approval and subsequent adoption by MSC 112, and are expected to enter into force on 1 January 2032.

New technologies and alternative fuels

The Maritime Safety Committee has considered potential alternative fuels and new technologies to support the reduction of greenhouse gas (GHG) emissions from ships from a safety perspective, and has identified safety obstacles, barriers and gaps in the current IMO instruments that may hinder their use. Related recommendations to support the possible safe use of these new fuels and technologies have been assigned to the relevant Sub-Committees.

SDC 12 considered the recommendations from MSC 110 and prepared a work plan for the development of a safety regulatory framework to support the safe uptake of new technologies and alternative fuels. The work plan includes the following technologies and possible deliverables:

Lithium-ion batteries and swappable traction lithium-ion battery containers:

• Consideration of draft amendments to SOLAS Regulation II-1/41 to allow for batteries to be used as the main source of electrical power and lighting systems.
• The initial work plan indicates target completion in 2028 of any draft amendments.

Wind propulsion and wind-assisted power:

• Consideration of revisions to the Intact Stability Code and the development of interim guidelines for the safety of ships using wind propulsion and wind-assisted power.
• Initial tasks include identifying relevant parts of IMO instruments, and relevant existing hazard-identification work
• The initial work plan indicates target completion in 2029 of any draft amendments and new guidelines

Nuclear power:

• Consideration of a revised Nuclear Code and related amendments to SOLAS Regulation VIII.
• Initial tasks include compiling information on previous hazard identification work and developing a comprehensive inventory of potential challenges related to the use of nuclear reactors for maritime applications.
• Any deliverables are expected in 2030, at the earliest.

Engine control room alert management

In March 2019, the passenger ship Viking Sky lost propulsion and nearly grounded off the coast of Norway. The accident investigation indicated that engine control room operators were overwhelmed by alarms during critical situations, increasing the risk of human error and delayed response. As a result, the IMO has agreed to develop performance standards for engine control room alert management (ECRAM) to mitigate these risks.

SDC 12 agreed to a draft outline for ECRAM performance standards and a related road map for the development work. A Correspondence Group was established to progress the work until SDC 13 in 2027. The road map indicates finalization of the performance standards by 2028.

Fibre-reinforced plastics

SDC 12 finalized a draft 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.

The draft revision is intended as a guidance regarding the assessment of the fire safety in the case of alternative designs, and addresses main fire safety aspects, including ignition potential of the FRP material, fire growth potential, firefighting strategies and equipment, and maintenance of the insulation to protect the FRP.

The revised interim FRP guidelines will be submitted to MSC 111 (May 2026) for approval.

Propulsion and steering systems

SOLAS Chapter II-1 addresses traditional steering gear arrangements with a rudder. Alternative, modern combined steering and propulsions systems (e.g. azimuth thrusters or waterjets) are, however, not addressed in the current regulatory framework.

SDC 12 considered 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 12 further discussed the ongoing development of draft new international ship manoeuvrability standards. The draft new standards are intended to be applicable to new ships subject to the new goal-based SOLAS regulations; however, they should not strengthen the required manoeuvring performance compared to the current fleet. The existing standards for ship manoeuvrability in Resolution MSC.137(76) will continue to be applicable to existing ships.

Members states and international organizations were encouraged to submit relevant trial data to support the development of the manoeuvrability standards. The work will be progressed in a Working Group at SDC 13 in 2027.

The draft revision of SOLAS Chapter II-1 to address both traditional and non-traditional propulsion and steering systems targets entry into force on 1 January 2032.

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 12 agreed to a draft technical guidance on co-optimizing energy efficiency and URN at the design and retrofit sage.

The draft technical guidance will be submitted to MEPC 84 for approval. MEPC 84 will also be invited to extend the target completion year of the EPB to 2028.

Emergency escape from machinery spaces

SOLAS Regulations II-1/13.4.1 and 13.4.2 require an escape trunk to extend from the lower part of the machinery space, without defining “lower part”. The Unified Interpretation in MSC.1/Circ.1511/Rev.1 clarifies that the term “lower part of the space” should be regarded as the lowest deck level, platform or passageway.

Many ships have escape trunks that do not extend fully down to the lowest deck level of the engine room, and recent Port State Control (PSC) inspections have challenged these arrangements, although they were approved by the flag administration.

MSC 110 acknowledged the differing interpretations and approved MSC.1/Circ.1689, inviting PSC authorities to adopt a pragmatic approach in the inspection of such arrangements while the Committee works on a long-term clarification of this issue.

SDC 12 considered whether there were any safety concerns with the current regulations and how they had been applied. It was agreed that no safety issues were demonstrated and that no further discussion was needed.

MSC 111 will be invited to note that no safety issues have been demonstrated and that the agenda item may be considered complete. Circular MSC.1/Circ.1689, being an interim solution, may be revoked accordingly.

MODU Code – emergency shutdown

The 2009 MODU Code requires equipment on an open deck to be shut down upon explosion hazards (gas leaks) unless the equipment is intended to be operational after shutdown and therefore rated for operation in Zone 2 locations.

SDC 12 agreed to draft amendments to paragraph 6.5 of the 2009 MODU Code to clarify the term “after shutdown” in the context of emergency shutdown systems with multiple levels of shutdown.

The draft amendments clarify that any equipment that must continue operating after emergency shutdowns must be either suitable for Zone 2 hazardous areas or subject to a conclusive risk assessment, or be properly protected within enclosed spaces. Furthermore, it was clarified that the term “after shutdown” refers to any level of emergency shutdown and not only total shutdown of the unit.

Critical functions like emergency lighting, blow out preventer controls, alarms, public address and battery radio systems must always remain operable. Shutdowns may isolate ignition sources by location or system, and any enclosed‑space equipment still operating must have protective measures to stay safe during a gas‑release incident.

The draft amendments will be submitted to MSC 111 (May 2026) for adoption and are expected to take effect from 1 January 2027.

Nitrogen receiver / buffer tank spaces

Paragraph 2.4.1.4 of Chapter 15 of the FSS Code requires an “enclosed space” where a nitrogen receiver or buffer tank is installed to have access from the open deck and be provided with extraction-type ventilation.

SDC 12 considered draft amendments to Chapter 15 of the FSS Code, to clarify the access and ventilation requirements when the nitrogen receiver or a buffer tank of the nitrogen generator system is located inside the engine room.

The work will continue at SDC 13 in 2026.

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 111 in May 2026.

DNV class customers are encouraged to visit the Compliance Planner to monitor how upcoming statutory requirements will impact their ships.