IMO Sub-Committee on Ship Design and Construction

The 7th session of IMO’s Sub-Committee on Ship Design and Construction (SDC) was held in London from 3 to 7 February 2020. SDC 7 finalized the interim guidelines on the second-generation intact stability criteria, clarified the requirements to watertight integrity on passenger ships and cargo ships, developed mandatory provisions for OSVs and other cargo ships carrying more than 12 industrial personnel, and finalized safety guidelines for fishing vessels and pleasure yachts operating in polar waters.

Relevant for ship owners and managers of cargo ships and passenger ships, and of fishing vessels and yachts operating in polar waters.

Meeting highlights

SDC 7:

  • Finalized interim guidelines on the second-generation intact stability criteria
  • Agreed on a draft new SOLAS chapter XV for cargo ships carrying more than 12 industrial personnel
  • Finalized safety guidelines for fishing vessels and pleasure yachts operating in polar waters
  • Agreed on draft amendments to the Explanatory Notes to SOLAS chapter II-1 on subdivision and damage stability
  • Clarified requirements to watertight doors on cargo ships

Explanatory Notes, SOLAS II-1 subdivision & damage stability

SDC 7 finalized the revised Explanatory Notes to SOLAS chapter II-1 with a view to adoption by MSC 102 (May 2020) as resolution MSC.429(98)/ Rev.1. The revised Explanatory Notes provide application provisions both for ships constructed on or after 1 January 2020 and also for ships constructed on or after 1 January 2024.

For ships constructed on or after 1 January 2024, the Explanatory Notes contain clarification of the maximum separation distance between watertight bulkheads and valves in piping systems (450 mm on either side) in order to regard them as part of the bulkhead. A new explanatory note to regulation 17.3 regarding doors above the bulkhead deck for passenger ships was also introduced in order to add clarity to the requirements for fire safety, water tightness and escape.

The associated MSC.1/Circ. 1572 regarding doors in watertight bulkheads of passenger ships and cargo ships was updated for approval by MSC 102 (May 2020). The circular will apply to new ships constructed on or after 1 January 2020 or from the effective date of issue. It is, however, expected that this circular will have to be revisited prior to SOLAS 2024 entering into force.

Non-SOLAS ships in polar waters

Incidents in polar waters pose risks to human life, to the polar environment and to search and rescue operations. Accordingly, the IMO has initiated a phase 2 of the Polar Code to address safety measures also for non-SOLAS ships operating in polar waters.

SDC 7 finalized draft guidelines for fishing vessels of at least 24 m in length and operating in polar waters, aligned with the 2012 Cape Town Agreement, and for pleasure yachts above 300 gross tonnage not engaged in trade. The draft guidelines outline recommendations for mitigating hazards in polar waters, such as icing, low temperatures, darkness, high latitudes, and delays in emergency response.

The two draft guidelines will be submitted to MSC 103 (November 2020) for approval, giving the Sub-Committee on Human Element, Training and Watchkeeping (HTW) time to comment on the training provisions in the fishing vessel guidelines.

Second-generation intact stability criteria

The 2008 Intact Stability Code uses empirical criteria, based on past casualty data. Hence, as ship design evolves, the uncertainty of these criteria increases. The new second-generation intact stability criteria are performance-based and allow the designer to choose between advanced numerical simulations, simplified criteria and operational measures.

SDC 7 finalized draft interim guidelines for the second-generation intact stability criteria, which address five dynamic stability failure modes in waves (dead ship condition, excessive accelerations, pure loss of stability, parametric roll and surf-riding/broaching).

The draft interim guidelines will be submitted to MSC 102 (May 2020) for approval with the aim of providing them for trial use to the industry. A correspondence group will work on the explanatory notes to the interim guidelines until SDC 8 (January 2021), with a view to approval at MSC 104 (June 2021).

Industrial personnel

The IMO has agreed to develop new mandatory provisions for the carriage of more than 12 industrial personnel (IP) on cargo ships to and from offshore facilities (e.g. offshore renewable installations) and ships.

SDC 7 agreed on a draft new SOLAS chapter XV and made good progress on a related mandatory goal-based IP Code. The draft IP Code is based on the 2008 SPS Code but with adaptions and provisions also for training of industrial personnel, safe personnel transfer, and the carriage of dangerous goods.

SDC 7 decided that all types of cargo ships can carry industrial personnel. However, ships carrying toxic, low-flashpoint products or acids are not allowed to have more than 60 persons on board. For ships certified to transport more than 240 persons, the SOLAS passenger ships regulations will apply for the carriage of dangerous goods.

The draft new SOLAS chapter XV targets entry into force from 1 January 2024, subject to approval and adoption by MSC. SDC 7 agreed that the new chapter shall apply to ships constructed on or after the entry into force date, and to existing ships staring to carry industrial personnel after that date. The application to existing ships already carrying industrial personnel will be considered by MSC 102 (May 2020).

A correspondence group will continue the work on the draft IP Code, including provisions for high-speed craft carrying industrial personnel, until SDC 8 (January 2021).

Water level detectors on non-bulk cargo ships

SDC 7 agreed on a draft new SOLAS regulation II-1/25-1, requiring new multiple-hold cargo ships to be fitted with water level detectors in each cargo hold intended for dry cargo. The draft new regulation will not apply to tankers, cargo holds intended for liquids, and tanks located entirely above the freeboard deck. The draft new SOLAS regulation will be submitted to MSC 102 (May 2020) for consideration and approval, with a view of entry into force from 1 January 2024.

MSC 102 may consider reviewing and expanding the existing regulation II-1/25 (water level detectors on single hold cargo ships other than bulk carriers) in order to consider water level detector requirements for ships that comply with the damage stability requirements.

Enhanced Survey Programme (2011 ESP Code)

SDC 7 agreed to draft amendments to the 2011 ESP Code to require that thickness measurements need only be taken at “suspect areas” at the first renewal survey of double hull oil tankers. This will align the thickness measurement requirements for oil tankers with the requirements for bulk carriers. The draft amendments will be submitted to MSC 102 (May 2020) for approval.

SDC 7 decided to discuss a framework for the use of Remote Inspection Techniques (RITs) as an alternative to close-up surveys at SDC 8 (January 2021).

Watertight doors on cargo ships

SDC 7 agreed on draft amendments to the MARPOL and Load Lines Convention and to the IBC and IGC Codes to address the inconsistencies between these IMO instruments and SOLAS regarding the consideration especially of hinged watertight doors in the different damage stability calculations, considering the type, technical/operational requirements such as quick acting/single action and indication on the navigation bridge, and the frequency of use of these watertight doors.

The amendments will apply to new ships from 1 January 2024, and possible existing ships (application provisions to be further considered by MEPC/MSC), subject to approval by MEPC 75 (April 2020) and MSC 102 (May 2020).

Any other business

SDC 7 agreed on a minor correction to the non-mandatory “Guidelines for safety access to tanker bows” (MSC.62(67)) to align the provisions on foot-stops in gangways with the requirements of the mandatory Load Lines Convention.

SDC 7 further agreed to a minor correction to regulation 22 of the Load Lines Convention to correct an erroneous reference to “inlets” in a table showing acceptable arrangements of scuppers and discharges.

The corrections are subject to approval by MSC 102 (May 2020).


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 GL recommends our customers to monitor the outcome of MSC 102 in May 2020.


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