IMO revises unified interpretations of the 2008 IS Code

The International Maritime Organization has released the revised unified interpretations of the 2008 Intact Stability Code.

MSC.1/Circ.1537/Rev.2 was released on 14 July 2023 and revokes MSC.1/Circ.1537/Rev.1.

Foreword

The Maritime Safety Committee, at its ninety-sixth session (11 to 20 May 2016), in order to facilitate global and consistent implementation of requirements of the 2008 Intact Stability Code (2008 IS Code), approved unified interpretations of the 2008 IS Code (MSC.1/Circ.1537), prepared by the Sub-Committee on Ship Design and Construction, at its third session.

The Maritime Safety Committee, at its 101st session (5 to 14 June 2019), approved amendments to MSC.1/Circ.1537 to include revisions of the unified interpretations of section 2.3 (Severe wind and rolling criterion (weather criterion)), as well as of section 3.4.2 (Assumptions for calculating loading conditions), prepared by the Sub-Committee on Ship Design and Construction, at its sixth session.

The Maritime Safety Committee, at its 107th session (31 May to 9 June 2023), approved amendments to MSC.1/Circ.1537/Rev.1, prepared by the Sub-Committee on Ship Design and Construction, at its ninth session, to clarify that the scope of application of the interpretation of the specific down-flooding points applied to the entire 2008 Intact Stability Code.

The amended text of the unified interpretations is set out in the annex.

Member States are invited to apply the annexed unified interpretations and to bring them to the attention of all parties concerned.

Annex: Unified interpretations of the 2008 IS Code

Introduction

2.23 Definition of the term "lightship"

The weight of mediums on board for the fixed fire-fighting systems (e.g. freshwater, CO2, dry chemical powder, foam concentrate, etc.) should be included in the lightweight and lightship condition.

Part A – Mandatory criteria

2.1 General

In applying φf, openings which cannot be or are incapable of being closed weathertight include ventilators (complying with regulation 19(4) of the International Convention on Load Lines, 1966) that for operational reasons have to remain open to supply air to the engine-room, emergency generator room or closed ro-ro and vehicle spaces (if the same is considered buoyant in the stability calculation or protecting openings leading below) for the effective operation of the ship. Where it is not technically feasible to treat some closed ro-ro and vehicle space ventilators as unprotected openings, Administrations may allow an alternative arrangement that provides an equivalent level of safety.

Part B – Recommendations for certain types of ships and additional guidelines

Chapter 1 General

In applying φf, openings which cannot be or are incapable of being closed weathertight include ventilators (complying with regulation 19(4) of the International Convention on Load Lines, 1966) that for operational reasons have to remain open to supply air to the engine-room, emergency generator room or closed ro-ro and vehicle spaces (if the same is considered buoyant in the stability calculation or protecting openings leading below) for the effective operation of the ship. Where it is not technically feasible to treat some closed ro-ro and vehicle space ventilators as unprotected openings, Administrations may allow an alternative arrangement that provides an equivalent level of safety.

3.4.2 Assumptions for calculating loading conditions

For tankers assigned with a tropical load line, the ship should be assumed to be loaded in accordance with the following:

.1 a fully loaded departure condition at the tropical load line and the corresponding arrival loading condition are considered;
.2 the cargo is homogeneously distributed throughout all cargo tanks; and
.3 seawater density is 1.025 t/m3.

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