IMO revises the Unified interpretation of SOLAS chapter II-1

The International Maritime Organization has published the revised Unified interpretation of SOLAS chapter II-1.

Circular MSC.1/Circ.1362/Rev.2 was published on 14 July 2023 and revokes MSC.1/Circ.1362/Rev.1.

The Maritime Safety Committee, at its eighty-seventh session (12 to 21 May 2010), with a view to providing more specific guidance for application of the relevant requirements of the 1974 SOLAS Convention, approved a unified interpretation of SOLAS regulation II-1/2.14, prepared by the Sub-Committee on Stability and Load Lines and on Fishing Vessels Safety, at its fifty-second session.

The Maritime Safety Committee, at its 105th session (20 to 29 April 2022), agreed to amend the above unified interpretation by incorporating interpretations for SOLAS regulations II-1/5.4 and II-1/5.5, prepared by the Sub-Committee on Ship Design and Construction, at its eighth session (17 to 21 January 2022).

The Maritime Safety Committee, at its 107th session (31 May to 9 June 2023), in order to clarify the documentation which is necessary to support an Administration or a recognized organization (RO) in verifying compliance with SOLAS regulation II-1/3-8, as well as to provide clarification for pressure testing of penetrations in watertight divisions after a fire test (SOLAS regulation II-1/13.2.3), approved amendments to MSC.1/Circ.1362/Rev.1, prepared by the Sub-Committee on Ship Design and Construction, at its ninth session.

Member Governments are invited to use the annexed unified interpretations as guidance when applying relevant provisions of SOLAS chapter II-1 and to bring them to the attention of all parties concerned.

Annex: Unified interpretation of SOLAS chapter II-1

Regulation 2.14 – Definitions

For ships constructed on or after 21 May 2010, in determining the permeability of a space, the volume of a space should be taken as the moulded volume, i.e. the immersed volume of a space should be the underwater moulded volume of that space multiplied by the permeability.

Regulation 3-8

SOLAS regulation II-1/3-8, as amended by resolution MSC.474(102) reads:

"Regulation 3-8

Towing and mooring equipment:

Paragraphs 4 to 6 of this regulation apply to ships constructed on or after 1 January 2007.
Paragraphs 7 and 8 of this regulation only apply to ships:

.1 for which the building contract is placed on or after 1 January 2024; or
.2 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 2024; or
.3 the delivery of which is on or after 1 January 2027.

This regulation does not apply to towing arrangements provided in accordance with regulation 3-4.
Ships shall be provided with arrangements, equipment, and fittings of sufficient safe working load to enable the safe conduct of all towing and mooring operations associated with the normal operation of the ship.
Arrangements, equipment and fittings provided in accordance with paragraph 4 above shall meet the appropriate requirements of the Administration or an organization recognized by the Administration under regulation I/6 (Refer to the Guidance on shipboard towing and mooring equipment (MSC.1/Circ.1175) for ships constructed on or after 1 January 2007 but before 1 January 2024 and the Guidance on shipboard towing and mooring equipment (MSC.1/Circ.1175/Rev.1) for ships constructed on or after 1 January 2024).
Each fitting or item of equipment provided under this regulation shall be clearly marked with any limitations associated with its safe operation, taking into account the strength of the supporting ship's structure and its attachment to it."
For ships of 3,000 gross tonnage and above, the mooring arrangement shall be designed, and the mooring equipment including lines shall be selected, in order to ensure occupational safety and safe mooring of the ship, based on the guidelines developed by the Organization (Refer to the Guidelines on the design of mooring arrangements and the selection of appropriate mooring
equipment and fittings for safe mooring (MSC.1/Circ.1619)). Ship-specific information shall be provided and kept on board (Refer to towing and mooring arrangement plan in the Guidelines on the design of mooring arrangements and the selection of appropriate mooring equipment and fittings for safe mooring (MSC.1/Circ.1619)).
Ships of less than 3,000 gross tonnage should comply with the requirement in paragraph 7 above as far as reasonably practicable, or with applicable national standards of the Administration.
For all ships, mooring equipment, including lines, shall be inspected and maintained in a suitable condition for their intended purposes (Refer to the Guidelines for inspection and maintenance of mooring equipment including lines (MSC.1/Circ.1620)).

Interpretation

The expression "all ships" in SOLAS regulation II-1/3-8.9 means ships constructed before, on, or after 1 January 2009 in accordance with SOLAS regulation ~~II-1/1.3.3~~II-1/1.1.3.2.
Irrespective of the scope of review by the Administration or a recognized organization (RO), as clarified below, for ships covered by the application provisions described in SOLAS regulations II-1/3-8.1 and II-1/3-8.2, as amended by resolution MSC.474(102), owners and designers should comply with the:

.1 Revised guidance on shipboard towing and mooring equipment (MSC.1/Circ.1175/Rev.1);
.2 Guidelines on the design of mooring arrangements and the selection of appropriate mooring equipment and fittings for safe mooring (MSC.1/Circ.1619); and
.3 Guidelines for inspection and maintenance of mooring equipment including lines (MSC.1/Circ.1620),

footnoted in SOLAS regulation II-1/3-8, in its entirety, and ensure that appropriate measures are taken to mitigate any occupational risks arising from deviations.

While applying the requirements of SOLAS regulation II-1/3-8.4 to regulation II-1/3-8.6 and SOLAS regulation II-1/3-8.8, for ships of less than 3,000 gross tonnage, the following is recommended:

.1 the "Towing and mooring arrangements plan" should be provided for information, where the winch brake holding capacities should be included in addition to the information provided in section 5 (Towing and mooring arrangements plan) of the annex to MSC.1/Circ.1175/Rev.1. A technical specification document of the mooring lines supplied with the ship should be provided for information. The manufacturers' recommended minimum diameter D of each fitting in contact with the mooring lines and the Line Design Break Force (LDBF) of the mooring lines should be included in the document;
.2 for confirmation of the appropriate selection of mooring line, the properties of mooring lines related to LDBF and bend radius (D/d ratio) should be submitted to the Administration or the RO. A warning should be provided that the wear rate of lines may be higher for lower diameter (paragraph 5.6 of MSC.1/Circ.1620); and.
.3 at delivery of the ship, the Administration or the RO should confirm that the towing and mooring arrangements plan is provided on board.

While applying the requirements of SOLAS regulation II-1/3-8.4 to regulation II-1/3-8.6 and the SOLAS regulation II-1/3-8.7, for ships of 3,000 gross tonnage and above, the following is recommended in addition to those specified under paragraph 3 of this interpretation:

.1 A document should be provided by the designer for information and as a supplement to the towing and mooring arrangements plan, confirming that MSC.1/Circ.1619 has been considered. The document should explicitly state that the deviations, if any, were unavoidable;
.2 Deviations should be recorded (paragraph 6.1 of MSC.1/Circ.1619), justification and suitable safety measures should be provided (paragraph 6.2 of MSC.1/Circ.1619) in the supplement to the towing and mooring arrangements plan. A reference to the supplement should be included in the towing and mooring arrangements plan (paragraph 6.3 of MSC.1/Circ.1619);
.3 If deviations are not found necessary, and the supplement is not needed, then this should be mentioned explicitly in the towing and mooring arrangements plan;
.4 The mooring winchesʹ brake holding capacities should be less than 100% of the Ship Design Minimum Breaking Load (MBLSD) (paragraphs 5.2.3.3 and 5.2.4 of MSC.1/Circ.1619). The winches should be fitted with brakes that allow for the reliable setting of the brake rendering load; and
.5 At delivery of the ship, the Administration or the RO should confirm that the towing and mooring arrangements plan and the supplement describing deviations and suitable safety measures is provided on board.

While applying the requirements of SOLAS regulation II-1/3-8.9, the following should be complied with, and compliance should be confirmed by the surveyor at the initial survey for new ships or at the first annual survey for the issuance of the Cargo Ship Safety Construction Certificate or renewal survey for the issuance of the Passenger Ship Safety Certificate after 1 January 2024 for existing ships:

.1 Procedures for mooring operations, inspection and maintenance of mooring equipment, including mooring lines, should be established and available on board (paragraph 3.1 of MSC.1/Circ.1620), taking into account industry practices (section 7 of MSC.1/Circ.1620);
.2 Procedures to allow the identification and control of mooring lines, tails and associated attachments should be established and available on board (paragraph 3.3 of MSC.1/Circ.1620);
.3 The periodic inspection of mooring lines, mooring line tails and associated attachments should be included in the onboard maintenance plan or equivalent maintenance management system (paragraph 4.1.1 of MSC.1/Circ.1620).
.4 Manufacturersʹ criteria for replacement of mooring lines should be available (paragraph 4.3.1 of MSC.1/Circ.1620).
.5 Records of the original design concept, equipment, arrangements, and specifications should be available on board (paragraph 4.4.4 of MSC.1/Circ.1620). For ships, the keels of which were laid before 1 January 2007 and without appropriate documentation, owners may establish the MBLSD for mooring based on the safe working load of mooring equipment provided on board. If no safe working load is specified, then owners are advised to check the strength of mooring equipment and their supporting hull structure based on MSC.1/Circ.1175/Rev.1 and determine MBLSD based on the actual capacity of the equipment and their supporting hull structure on board. Manufacturers' test certificates for mooring lines, joining shackles, and synthetic tails should be kept on board and properly linked back to the equipment, if available (paragraph 6.2 of MSC.1/Circ.1620); and
.6 A document should be provided on board for gathering the information above and describe how the information listed above is filed and collected.

While applying the requirements of SOLAS regulation II-1/3-8.9, the following should be complied with, and the compliance should be confirmed by the surveyor at the periodical survey for endorsement/issue of the Cargo Ship Safety Construction Certificate or the renewal survey for the Passenger Ship Safety Certificate after 1 January 2024 for existing ships:

.1 The records of inspection and maintenance of mooring equipment and inspection and replacement of mooring lines, since the last periodical survey, should be kept updated and available on board (paragraphs 4.4.3 and 6.1 of MSC.1/Circ.1620).

Regulations 5.4 and 5.5

SOLAS regulations II-1/5.4 and II-1/5.5 read:

"Regulation 5

Intact stability

...

Where any alterations are made to a ship so as to materially affect the stability information supplied to the master, amended stability information shall be provided. If necessary, the ship shall be re-inclined. The ship shall be re-inclined if anticipated deviations exceed one of the values specified in paragraph 5.
At periodical intervals not exceeding five years, a lightweight survey shall be carried out on all passenger ships to verify any changes in lightship displacement and longitudinal center of gravity. The ship shall be re-inclined whenever, in comparison with the approved stability information, a deviation from the lightship displacement exceeding 2% or a deviation of the longitudinal center of gravity exceeding 1% of L is found or anticipated."

Revised Explanatory Notes to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and Rev.2) read:

"Regulation 5.4

When alterations are made to a ship in service that result in calculable differences in the lightship properties, a detailed weights and centres of gravity calculation to adjust the lightship properties should be carried out. If the adjusted lightship displacement or longitudinal centre of gravity, when compared to the approved values, exceeds one of the deviation limits specified in regulation 5.5, the ship should be re-inclined. In addition, if the adjusted lightship vertical centre of gravity, when compared to the approved value, exceeds 1%, the ship should be re-inclined. The lightship transverse centre of gravity is not subject to a deviation limit.
When a ship does not exceed the deviation limits specified in explanatory note 1 above, amended stability information should be provided to the master using the new calculated lightship properties if any of the following deviations from the approved values are exceeded:

.1 1% of the lightship displacement; or
.2 0.5% of L for the longitudinal centre of gravity; or
.3 0.5% of the vertical centre of gravity.

However, in cases when these deviation limits are not exceeded, it is not necessary to amend the stability information supplied to the master.

When multiple alterations are made to a ship in service over a period of time and each alteration is within the deviation limits specified above, the cumulative total changes to the lightship properties from the most recent inclining also should not exceed the deviation limits specified above or the ship should be re-inclined."

Interpretation

Definition of lightweight calculation

For the purposes of this interpretation, the term "lightweight calculation" means a detailed calculation of weights on and weights off a ship, resulting from all alterations to the ship since the date of the last approved inclining test, to determine the adjusted lightship properties. Lightship properties include weights and the centre of gravity. The documented weights and their centres of gravity should be verified on board/on-site by the attending class surveyor.

When weights are added, removed or relocated, the final cumulative change is to be compared to the last approved inclining test.

"Lightweight survey" is defined in the International Code on Intact Stability 2008, paragraph 2.24.

Definition of stability information

"Stability information" includes any document (whether on paper or electronic) or electronic means of calculation of stability which includes lightship properties. This could include, but is not limited to, the approved stability book, computer software for onboard calculation of stability, the approved strength book and the loading instrument.

Amendment of stability information in conjunction with alterations of lightship properties:

If the lightweight calculation, regardless of keel laying date, shows a deviation in lightweight mass, or the longitudinal or vertical position of the center of gravity:

1.1 beyond any of the tolerance limits specified in explanatory note 1 to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and Rev.2), then the ship should be re-inclined, and the stability information, as defined above, should be updated to reflect the lightship properties derived from the inclining test and should be approved.
1.2 within the tolerance limits specified in the explanatory note 1 and exceeding any of the deviations specified in explanatory note 2 to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and Rev.2), then the stability information should be updated to reflect the lightship properties derived from the lightweight calculation and should be approved; or
1.3 within the tolerance limits specified in explanatory note 2 to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and Rev.2), then a copy of the endorsed lightweight calculation report should be provided on board for future reference with no further amendments required to the stability information. However, even if addition, removal, or relocation of any weight results in lightship particulars being within tolerable limits, that weight should still be noted, and the "constant" adjusted for lightweight calculation in the stability information for all future references and calculations.

A summary of paragraph 1 of this interpretation is provided in the following table. Where stability information is to be updated, it should be approved and provided to the master with the instruction that it should now be used for all stability calculations.
Lightship properties should be consistent in all documents which use them, e.g. loading manual, stability manual and computer data.
A change in lightweight will result in a change in deadweight unless there is an associated change in freeboard. The consequences of the change could have an impact on compliance with other regulations, e.g. MARPOL Annex VI.

Regulation 13

SOLAS regulation II-1/13.2.3 reads:

"Regulation 13
Openings in watertight bulkheads below the bulkhead deck in passenger ships

2.3 Lead or other heat-sensitive materials shall not be used in systems which penetrate watertight bulkheads, where deterioration of such systems in the event of fire would impair the watertight integrity of the bulkheads."

Interpretation

Any penetration used for the passage of heat-sensitive piping systems through a watertight bulkhead or deck on a passenger ship under SOLAS regulation II-1/13.2.3 should be tested with the heat-sensitive piping and should be type-approved for watertight integrity as per paragraphs 4 and 5 of the explanatory notes to regulation II-1/13.2.3 contained in the annex of resolutions MSC.429(98)/Rev.1 and Rev.2, as applicable, after the fire test.
SOLAS regulation II-1/13.2.3 should be applicable to heat-sensitive piping systems and should not be applied to cable penetrations in watertight bulkheads and decks.

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