Section 2 Definitions

2.1.1  Finnish Swedish Ice Class Rules (hereinafter referred to as FS Rules) are the ice class Rules incorporated into Pt 8 Rules for Ice and Cold Operations of the Rules for Ships for first-year ice conditions.

2.1.2  Polar Class Rules (hereinafter referred to as PC Rules) are the ice class Rules incorporated into Pt 8 Rules for Ice and Cold Operations of the Rules for Ships for multi-year ice conditions.

2.1.3 The definitions in Ch 1, 2.2 Ship definitions, Ch 1, 2.3 Propulsion unit definitions and Ch 1, 2.4 Operational definitions are intended for use in identifying and describing Stern First Ice Class Ships and their operations only.

2.2.1  Conventional Ice Class Ship is designed to operate in ice-covered waters with the support of an icebreaker or with independent navigation by means of an ice-strengthened bow. The level of capability in ice is dependent on the level of ice-strengthening, hull form optimisation and propulsive power. Such ships are not covered by these Rules. See Table 1.2.1 Ship types in relation to ship operations and ice conditions.

2.2.2  Stern First Ice Class Ship is equipped with podded propulsion units or azimuthing thrusters and designed for stern first operations in ice, and is expected to operate in ice going stern first as part of its operational profile. Such ships may be provided with a conventional bow for open water or light ice conditions, or for ice an icebreaking bow. See Table 1.2.1 Ship types in relation to ship operations and ice conditions.

2.2.3  Icebreaker is a sea-going ship especially designed for icebreaking duties. Icebreaker refers to any ship having an operational profile that includes escort or ice management functions, having powering and dimensions that allow it to undertake aggressive operations in ice-covered waters. These Rules may also be applied to icebreakers intended to operate stern first in ice as part of their operational profile. See Table 1.2.1 Ship types in relation to ship operations and ice conditions.

2.3.1 In these Rules, propulsion units are considered to be of the pulling type. Other propulsion arrangements, such as nozzles, ducts, push/pull or pushing type applications will receive special consideration based on the philosophy of the Rules and the operational scenarios developed.

2.4.1  Stern. The end of the ship which incorporates the propulsion unit. This is irrespective of the direction in which the ship transits. See Figure 1.2.1 Direction-dependent definitions.

Figure 1.2.1 Direction-dependent definitions

2.4.2  Bow. The opposing end of the ship to the stern, as defined in 2.4.1. This is irrespective of the direction in which the ship transits. See Figure 1.2.1 Direction-dependent definitions.

2.4.3  Forward. The term ‘forward’ is direction dependent. For the bow first mode ‘forward’ refers to the bow. For stern first mode ‘forward’ refers to the stern. See Figure 1.2.1 Direction-dependent definitions.

2.4.4  Aft. The term ‘aft’ is direction dependent. For the bow first mode ‘aft’ refers to the stern. For stern first mode, ‘aft’ refers to the bow. See Figure 1.2.1 Direction-dependent definitions.

2.4.5  Mode of operation refers to the direction and method by which the ship operates in ice.

2.4.6  Bow first mode. The mode of operation with the bow facing the direction of travel. In the bow first mode the propeller pulls from aft. See Figure 1.2.1 Direction-dependent definitions.

2.4.7  Stern first mode. The mode of operation with the stern facing the direction of travel. In the stern first mode the propeller pulls from forward. See Figure 1.2.1 Direction-dependent definitions.

2.4.8  Independent. Navigation in ice which does not adhere to a predetermined route or area and does not require assistance from icebreakers.

2.4.9  Escorted. Operation on a predetermined route or area which is supported by icebreakers.

2.4.10  Unescorted. Operates on a predetermined route or area which is supported by icebreakers but generally does not require icebreaker assistance.

2.4.11  Ice transit. Describes any part of a ship voyage in which ice is encountered at a sufficient concentration or thickness to affect significantly the ship’s open water performance.

2.4.12  Bow first ice transit. Describes a part of the voyage with the ship going through ice in the bow first mode. The extent (in terms of ice conditions) of a bow first ice transit will be dependent on the ice-strengthening capability incorporated into the bow structure.

2.4.13  Stern first ice transit. Describes a part of the voyage when the ship goes through ice in the stern first mode. The extent (in terms of ice conditions) of a stern first ice transit will be dependent on the ice-strengthening capability incorporated into the stern structure.

2.5.1  Operational scenario describes, for a way point during operation in ice, the ice conditions that the ship will encounter and the mode of operating.

2.5.2  Load scenario is associated with one or more operational scenarios, giving the most critical loading for the hull area or machinery component under consideration as a result of stern first operation in ice.

2.5.3  Standard load scenario is the load scenario used as the basis for interpreting the FS Rules and PC Rules for stern first operation in these Rules.

2.5.4  Non-standard load scenario is a load scenario that differs from the standard load scenarios in these Rules.

2.6.1 The World Meteorological Organisation (WMO) definitions for sea ice thickness are given in Table 1.2.2 WMO definition of ice conditions.

2.6.2  Old ice. Sea ice which has survived at least one summer’s melt. May be subdivided into second-year and multi-year ice.

2.6.3  Ice cover. The ratio of an area of ice of any concentration to the total area of sea surface within a large geographic location, this location may be global, hemispheric, or prescribed by a specific oceanographic entity such as Baffin Bay or the Barents Sea.

2.6.4  Level ice. Sea ice which is unaffected by deformation.

2.6.5  Brash ice. Accumulation of floating ice made up of fragments not more than 2 m across, from the wreckage of other forms of ice.

2.6.6  Ice ridge. A line or wall of broken ice forced up by pressure. The submerged volume of broken ice in a ridge, forced downwards by pressure, is termed an ice keel. See Figure 1.2.2 Ice ridge terminology.

Figure 1.2.2 Ice ridge terminology

2.6.7  Ice pressure. Pressure actively causing deformation processes in ice. Pressure may result from ocean, tidal, river or coastal currents, wind or a combination of these.

2.6.8  Ice channel. A passage in the ice broken by an icebreaker or a proceeding ship.

2.6.9  Consolidated (refrozen) ice. Ice which has melted and/or broken up before reforming under pressure and refreezing.

2.6.10  Special ice features. Grounded first-year ridges (stamukhas), massive multi-year ice, etc.

2.6.11  Open water. A large area of freely navigable water in which the ice cover is less than 1/10th.