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Summary of the 9th session of the IMO Sub-Committee on Ship Design and Construction (SDC 9)

Feb. 9, 2023 | By Office of Design and Engineering Standards

The International Maritime Organization’s (IMO) Sub-Committee on Ship Design and Construction (SDC) held its ninth session in-person and remotely from IMO headquarters in London, United Kingdom, from January 23 to 27, 2023.  Captain Daniel Cost, Chief of the U.S. Coast Guard’s Office of Design & Engineering Standards (CG-ENG), led the U.S. delegation, comprised of members from U.S. Coast Guard, U.S. Navy, U.S. Department of State, U.S. National Oceanographic and Atmospheric Administration, U.S. Maritime Administration and technical advisors from the private sector.

The key topics of discussion at SDC 9 were:

  1. The review of the Guidelines for the Reduction of Underwater Noise (MEPC.1/Circ.833) and identification of next steps;
  2. Revisions of performance standards for water level detectors on bulk carriers and single hold cargo ships other than bulk carriers;
  3. Unified Interpretations to provisions of IMO safety, security, and environment –related conventions;
  4. Revisions to the Safe Return to Port (SRtP) interim explanatory notes;
  5. Safety objectives and functional requirements of the guidelines on alternative designs and arrangements for SOLAS Chapters II-1; and
  6. Amendments to SOLAS II-1/3-4 for emergency towing equipment for new ships other than tankers.

Underwater Radiated Noise
The Sub-Committee finalized the draft revised guidelines for the reduction of underwater noise from commercial shipping to address adverse impacts on marine life (MEPC.1/Circ.833) – for intended approval at the 80th session of the Marine Environmental Protection Committee (MEPC 80). A Correspondence Group, coordinated by Canada, was re-established for the intersessional period between SDC 9 and 10, The Correspondence Group will be addressing the remaining work on this agenda item, including finalizing and prioritizing the provisional list of suggested next steps to further prevent and reduce underwater radiated noise from ships.

Water level detectors
The Sub-Committee revised the draft amendments (MSC.188 (79)/Rev.1) on Performance standards for water level detectors on ships subject to SOLAS regulation II-1/25, II-1/25-1, and XII/12 – to clarify installation heights for bilge and water level detectors. The revised amendments have an entry into force date of January 1, 2024.

Unified Interpretations
The Sub-Committee finalized four unified interpretations during the session. First, on the newly amended SOLAS regulation II-1/3-8 (Towing and mooring equipment), to clarify the documentation which is necessary to support an Administration or a regional organization (RO) in verifying compliance with the regulation. Second, regarding SOLAS regulation II-1/13, clarifying that heat-sensitive piping systems penetrating a watertight bulkhead or deck on a passenger ship should be tested and be type-approved for watertight integrity after the fire test. Third, for the expressions "ships constructed before 1 January 2024" and "multiple hold cargo ships other than bulk carriers and tankers constructed on or after 1 January 2024" in SOLAS Chapter II-1. Lastly, a revision of the interpretation of down-flooding points to realign the scope of their application to all criteria addressed by the 2008 Intact Stability Code.

Safe Return to Port (SRtP)
The Sub-Committee considered the output of the Working Group established during this session to review the Interim Explanatory Notes (MSC.1/Circ 1369) providing guidance for the uniform implementation of SOLAS regulations II-1/8-1, II-2/21, and II-2/22.  The Working Group recommended that the Notes, which were published in 2010 immediately before the entry into force of the SRtP design requirements, required more consideration in light of the numerous advances seen on cruise ships. The Sub-Committee agreed and a Correspondence Group, to be coordinated by Germany, was established for the intersessional period between SDC 9 and 10.

Alternative Design and Arrangements for SOLAS Chapter II-1
The Sub-Committee progressed draft goals for SOLAS Chapter II-1 Part C on “Machinery installations” and Part E on “Periodically unattended machinery spaces” based on agreed failure modes. The goal-based provisions for Part D on “Electrical installations” were agreed at SDC 8. The goal-based provisions will eventually be included in a second revision of the Guidelines on Alternative Design and Arrangements for SOLAS Chapters II-1 and III (MSC.1/Circ.1212/Rev.1) and submitted to MSC for approval. A Correspondence Group, led by Japan, for the intersessional period between SDC 9 and 10. The Correspondence Group will progress goals, functional requirements and expected performances for SOLAS Chapter II-1 Parts C and E until SDC 10 in January 2024.

Towing Equipment
The Sub-Committee finalized the amendments to SOLAS Chapter II-1/3.4 to require that all ships other than tankers over 20,000 gross tonnage (ITC) built on or after January 1, 2028, to be equipped with towing arrangements. The expert’s group assigned to finalize the requirements also recommended the Sub-Committee to request of the parent committee (Maritime Safety Committee) to agree to new guidelines for towing arrangements for new ships other than tankers and amend the guidelines for emergency towing arrangements (MSC.35(63)).

Tentative dates for SDC 10
The tentative dates for SDC 10 are 22 to 26 January 2024.

Election of Chair and Vice-Chair
The Sub-Committee elected Mr. Erik Tvedt (Denmark) and Mr. Jaideep Sirkar (United States) as Chair and Vice-Chair respectively for SDC for the calendar year 2024.

For more information, please contact LCDR Bryan Andrews at

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