Section 2 Ice Strengthening

201. Classification of Ice Strengthening

1. Strengthening for navigation in ice is classified into the following 5 class notations dependent on the degree of reinforcement and engine output of the ship(see Annex 1, 102).

(1) IA Super : ships with such structure, engine output and other properties that they are normally capable of navigating in difficult ice conditions without the assistance of Icebreakers

(2) IA : ships with such structure, engine output and other properties that they are capable gating in difficult ice conditions, with the assistance of Icebreakers when necessary

(3) IB : ships with such structure, engine output and other properties that they are capable

gating in moderate ice conditions, with the assistance of Icebreakers when necessary

(4) IC : ships with such structure, engine output and other properties that they are capable gating in light ice conditions, with the assistance of Icebreakers when necessary

(5) ID : ships that have a steel hull and that are structurally fit for navigation in the open

of navi-

of navi- of navi-

sea and

that, are capable of navigating in very light ice conditions with their own propulsion machinery

2. It is the responsibility of the Owner to determine which class in Par 1 is most suitable for this requirement.

202. Definitions

The definitions of terms which appear in this Chapter are to be specified as the following, unless otherwise specified elsewhere.

1. The bow, midbody, and stern regions in way of hull part are defined for ships of Ice classes IA Super, IA, IB and IC and the bow region is defined for ships of Ice class ID as follows:

(1) Bow region: From the stem to a line parallel to and 0.04 aft of the bow borderline of the part of the hull where the waterlines run parallel to the centerline. For Ice classes IA Super and IA the overlap over the borderline need not exceed 6 m, and for Ice classes IB, IC and ID this overlap need not exceed 5 m.

(2) Midbody region: From the aft boundary of the bow region to a line parallel to and 0.04 aft of the aft borderline of the part of the hull where the waterlines run parallel to the centreline. For Ice classes IA Super and IA the overlap over the borderline need not exceed 6 m, and for Ice classes IB and IC this overlap need not exceed 5 m.

(3) Stern region: From the aft boundary of the midbody region to the stern.

2. The ice belt is the part of the shell plating which has to be reinforced. (see Fig 1.1)

Fig 1.1 Ice Belt at each region

3. The upper ice waterline (UIWL) shall be the envelop of the highest points of the waterline at which the ship is intended to operate in ice. The line may be a broken line. The lower ice water- line (LIWL) shall be the envelop of the lowest points of the waterline at which the ship is in- tended to operate in ice. The maximum and minimum Ice class draughts at fore and aft perpendic- ulars shall be determined in accordance with the upper and lower ice waterlines.

4. Restrictions on draughts when operating in ice shall be documented and kept on board readily available to the master. The maximum and minimum Ice class draughts fore, amidships and aft shall be indicated in the classification certificate. For ships built("Built" means the keel of ships has been laid or which has been at a similar stage of construction) on or after 1 July 2007, if the summer load line in fresh water is anywhere located at a higher level than the UIWL, the ship’s sides are to be provided with a warning triangle and with an Ice class draught mark at the max- imum permissible Ice class draught amidships. Ships built before 1 July 2007 shall be provided with such a marking, if the UIWL is below the summer load line, not later than the first sched- uled dry docking after 1 July 2007(see Annex 1, 103). Ships built before 1 July 2007 shall be provided with such a marking, if the UIWL is below the summer load line, not later than the first scheduled dry docking after 1 July 2007.

5. The draught and trim, limited by UIWL, must not be exceeded when the ship is navigating in ice.

The salinity of sea water along the intended route shall be taken into account when loading the

ship.

203. Security of Minimum Draught

1. Any ballast tank, situated above the LIWL and needed to load down the ship to this water line is to be equipped with proper devices to prevent the water from freezing.

2. The propeller is to be fully submerged, if possible, entirely below the ice.

3. The minimum forward draught is not to be less than that obtained from the following formula, which need not exceed .

(m)

= the displacement (ton) of ship on the maximum ice-class draught according to 202. 3

= level ice thickness given in Table 1.1

Table 1.1 Level ice thickness