Arctic Council Working Group

Chapter 4: Subdivision and Stability (Part IA)

Chapter summary:

Chapter 4 identifies requirements for ensuring adequate subdivision and stability for both damaged and intact vessels at risk of ice accretion or ice-related damage. These are set out in the text of Chapter 4 below.

Submissions

Hyperlink: Eagle.org

ABS is a leading international classification organization devoted to promoting the security of life and property and preserving the natural environment through the development and verification of standards for the design, construction and operational maintenance of marine and offshore assets.

The ABS Steel Vessel Rules contain requirement for stability that match the International Load Line Convention. When ice accretion is likely to occur, ABS offers an ice accretion analysis as part of the climate hazard assessment service, additional stability assessments are required. Also when ice accretion is likely the vessel needs to have appropriate means of managing the ice buildup. The ABS Guide for Vessels Operating in Low Temperature Environments contains some helpful guidance for ship operators, but ABS through its Advisory Services, offers assistance to ship owners in selecting realistic and practical solutions to deal with ice accretion.

Hyperlink: IMO Polar Code
Follow this link for DNV GL’s guide to the Polar Code Document ‘Maritime Polar Code: Understand the Code’s requirements to take the right steps for smooth compliance’. For Chapter 4, see page 16.

See also:

Hyperlink: http://www.icetra.is
The Icelandic Transport Authority manages the administration of transport affairs and conducts oversight pertaining to aviation, maritime affairs, traffic and safety oversight of transport structures and navigation. The Icelandic Transport Authority issues certificates to seafarares and is responsible for Port State Control and Flag State Control and manages the Icelandic ship registry.

Hyperlink 1: The Polar Code by Lloyds
Lloyd's provides information and assistance for users to comply with the Polar Code. Lloyd's interactive toolkit allows users to work through the Code on their own terms and download Lloyd's register free guidance, templates and examples to help understand and meet compliance needs.

Hyperlink 2: Lloyd's Polar Code Resources
Lloyd's also provides guidance documents on; the Operational Assessment, setting operational limitations (limitation wording), determining the Operating Envelope and LR’s How to use POLARIS.

Hyperlink 3: The Polar Code: A Regulatory Interpretation Guide
This document provides Loyd's Register guidance on all aspects of the Polar Code (chapter by chapter). For Chapter 4, see LR Regulatory Guide pages 33 to 36. See also the LR guidance on ice accretion in Part 8, Chapter 1 of the Rules for Ships.

Lloyd's Register website.

Hyperlink 1: Northern Sea Route – Best practices and Challenges (2017)
For Chapter 4, see pages 3-4.

Hyperlink 2: Offshore Vessel Operations In Ice and or Severe Sub Zero Temperatures in Artic and Sub Artic regions (2014).
The purpose of this paper is to provide guidance to operators and charterers of offshore support vessels employed for use in areas impacted by ice or severe sub-zero temperatures with the aim of encouraging high standards of safety and environmental protection for those operating in Arctic and Sub-Arctic regions.

CHAPTER 4 – SUBDIVISION AND STABILITY: Full Polar Code text

As adopted from IMO - Full Polar Code text

4.1 Goal

The goal of this chapter is to ensure adequate subdivision and stability in both intact and damaged conditions.


4.2 Functional requirements

In order to achieve the goal set out in paragraph 4.1 above, the following functional requirements are embodied in the regulations of this chapter:

  • .1 ships shall have sufficient stability in intact conditions when subject to ice accretion; and
  • .2 ships of category A and B, constructed on or after 1 January 2017, shall have sufficient residual stability to sustain ice-related damages.

4.3 Regulations
4.3.1 Stability in intact conditions

  • 4.3.1.1 In order to comply with the functional requirement of paragraph 4.2.1, for ships operating in areas and during periods where ice accretion is likely to occur, the following icing allowance shall be made in the stability calculations:
    • .1 30 kg/m2 on exposed weather decks and gangways;
    • .2 7.5 kg/m2 for the projected lateral area of each side of the ship above the water plane; and
    • .3 the projected lateral area of discontinuous surfaces of rail, sundry booms, spars (except masts) and rigging of ships having no sails and the projected lateral area of other small objects shall be computed by increasing the total projected area of continuous surfaces by 5% and the static moments of this area by 10%.
  • 4.3.1.2 Ships operating in areas and during periods where ice accretion is likely to occur shall be:
    • .1 designed to minimize the accretion of ice; and
    • .2 equipped with such means for removing ice as the Administration may require; for example, electrical and pneumatic devices, and/or special tools such as axes or wooden clubs for removing ice from bulwarks, rails and erections.
  • 4.3.1.3 Information on the icing allowance included in the stability calculations shall be given in the PWOM.
  • 4.3.1.4 Ice accretion shall be monitored and appropriate measures taken to ensure that the ice accretion does not exceed the values given in the PWOM.

4.3.2 Stability in damaged conditions

  • 4.3.2.1 In order to comply with the functional requirements of paragraph 4.2.2, ships of categories A and B, constructed on or after 1 January 2017, shall be able to withstand flooding resulting from hull penetration due to ice impact. The residual stability following ice damage shall be such that the factor si, as defined in SOLAS regulations II-1/7-2.2 and II-1/7-2.3, is equal to one for all loading conditions used to calculate the attained subdivision index in SOLAS regulation II-1/7. However, for cargo ships that comply with subdivision and damage stability regulations in another instrument developed by the Organization, as provided by SOLAS regulation II-1/4.1, the residual stability criteria of that instrument shall be met for each loading condition.
  • 4.3.2.2 The ice damage extents to be assumed when demonstrating compliance with paragraph 4.3.2.1 shall be such that:
    • .1 the longitudinal extent is 4.5% of the upper ice waterline length if centred forward of the maximum breadth on the upper ice waterline, and 1.5% of upper ice waterline length otherwise, and shall be assumed at any longitudinal position along the ship's length;
    • .2 the transverse penetration extent is 760 mm, measured normal to the shell over the full extent of the damage; and
    • .3 the vertical extent is the lesser of 20% of the upper ice waterline draught or the longitudinal extent, and shall be assumed at any vertical position between the keel and 120% of the upper ice waterline draught.