Chapter 4:

subdivision and stability

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 clearly set out in the Chapter 4 wording below.


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
  • 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%.
  • 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.
  • Information on the icing allowance included in the stability calculations shall be given in the PWOM.
  • 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
  • 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.
  • The ice damage extents to be assumed when demonstrating compliance with paragraph 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.

administration1   participants1