Section 1 Polar Class Descriptions and Application

101. Application

1. This chapter is to apply to ships constructed of steel and intended for navigation in ice‐infested po- lar waters. However ships with ice breaking capability or ice breakers are to be in complaince with the requirements of Ch 3.

2. Ships that comply with the requirements in Sec 2 and Sec 3 can be considered for a Polar Class notation as listed in Table 2.1. The requirements of Sec 2 and Sec 3 are in addition to the open water requirements of the Society. If the hull and machinery are constructed such as to comply with the requirements of different polar classes, then both the hull and machinery are to be as- signed the lower of these classes in the classification certificate. Compliance of the hull or machi- nery with the requirements of a higher polar class is also to be indicated in the classification cer- tificate or an annex thereto.

102.

Polar classes

1. The Polar Class (PC) notations and descriptions are given in Table 2.1. It is the responsibility of the Owner to select an appropriate Polar Class. The descriptions in Table 2.1 are intended to guide owners, designers and administrations in selecting an appropriate Polar Class to match the re- quirements for the ship with its intended voyage or service.

2. The Polar Class notation is used throughout this chapter with respect to operational capability and strength.

to convey the differences between classes

Table 2.1 Polar class descriptions

103. Upper and lower ice waterlines

1. The upper and lower ice waterlines upon which the design of the vessel has been based is to be indicated in the classification certificate. The upper ice waterline (UIWL) is to be defined by the maximum draughts fore, amidships and aft. The lower ice waterline (LIWL) is to be defined by the minimum draughts fore, amidships and aft.

2. The lower ice waterline is to be determined with due regard to the vessel’s ice-going capability in the ballast loading conditions(e.g. propeller submergence).

104. Subdivision and stability

1. For the ships to apply this chapter, the followings are to be examined, considering the navigation fea- tures in ice-infested polar waters within approved limitations, in addition to the requirements regarding the stability and subdivision for the ships navigating in open waters.

(1) Intact stability when operated in ice-infested polar waters

(A) Account should be taken of the effect of icing in the stability calculations.

(B) Suitable calculations should be carried out and/or tests conducted to demonstrate the follow- ing:

(a) the ship, when operated in ice within approved limitations, during a disturbance causing roll, pitch, heave or heel due to turning or any other cause, should maintain sufficient positive

stability; and

(b) ships of Polar Classes 1 to 3 and Icebreakers of all classes, when riding up in ice and remaining momentarily poised at the lowest stem extremity, should maintain sufficient

positive stability.

(C) Sufficient positive stability in paragraphs (A). (a) and (b) means that the ship is in a pos- itive state of equilibrium with a positive metacentric height of at least 150 mm, and a line

150 mm below the edge of the freeboard deck as defined in the applicable LL Convention,

is not submerged.

(D) For performing stability calculations on ships that ride up onto the ice, the ship should be assumed to remain momentarily poised at the lowest stem extremity as follows:

(a) for a regular stem profile, at the point at which the stem contour is tangent to the keel line;

(b) for a stem fitted with a structurally defined skeg, at the point at which the stem con-

tour meets the top of the skeg;

(c) for a stem profile where the skeg is defined by shape alone, at the point at which the stem contour tangent intersects the tangent of the skeg; or

(d) for a stem profile of novel design, the position should be specially considered.

(2) Damage stability to be expected when operated in ice-infested polar waters

(A) All Polar Class ships should be able to withstand flooding resulting from hull penetration due to ice damage of the extent set out in paragraph (B) and location set out in paragraph

(C), and the residual stability following ice damage should be such that the factor si, as de-

fined in SOLAS regulation II-1/7.2, has si = 1 for all loading conditions.

(B) The dimensions of an ice damage penetration should be taken as:

(a) longitudinal extent 0.045 of upper ice waterline length if centered forward of the point of maximum beam on the waterline, and 0.015 of upper ice waterline length otherwise;

(b) depth 760 mm measured normal to the shell over the full extent of the damage; and

(c) vertical extent the lesser of 0.2 of upper ice draft, or of longitudinal extent of (a).

(C) The centre of the ice damage may be located at any point between the keel and 1.2 times the upper ice draft. The vertical extent of damage may be assumed to be confined between

the keel and 1.2 times the upper ice draft. For ships of Polar Classes 6 and 7 not carrying

polluting or hazardous cargoes, damage may be assumed to be confined between watertight bulkheads, except where such bulkheads are spaced at less than the damage dimension of (B).

(3) Security of subdivision and watertightness when operated in ice-infested polar waters

(A) Subject to (B) and (C), no Polar Class ship should carry any pollutant directly against the outer shell. Any pollutant should be separated from the outer shell of the ship by double

skin construction of at least 760 mm in width.

(B) All Polar Class ships should have double bottoms over the breadth and the length between forepeak and afterpeak bulkheads. Double bottom height should be in accordance with the rules of the Classification Societies in force. Double bottoms should not be used for the carriage of pollutants except where a double skin construction complying with paragraph (A) is provided, or where working liquids, are carried in way of main machinery spaces in

tanks not exceeding 20 m3 individual volume.

(C) Double bottoms in ships of Polar Classes 6 and 7 may be used for the carriage of any working liquids where the tanks are aft of midships and within the flat of bottom.

(D) All Polar Class ships with icebreaking bow forms and short forepeaks may dispense with

double bottoms up to the forepeak bulkhead in the area of the inclined stem, provided that the watertight compartments between the forepeak bulkhead and the bulkhead at the junction

between the stem and the keel are not used to carry pollutants.