Section 1 General

1.1.1 The Technical Background Document follows the structure and content of the Rules for Stern First Ice Class Ships. Sections in the Technical Background cross-refer to those of the Rules. Cross-references between Sections of this Technical Background are suffixed by ‘TB’.

1.1.2 The Rules have been developed primarily in relation to podded propulsion units. However, the philosophies and principles included in the Rules may also be applied to any other propulsion unit that provides azimuthing thrust as the primary means of propulsion when operating stern first in ice. This includes mechanical azimuthing thrusters and other devices where the propulsion drive system is internal to the ship. It should be noted that the operational scenarios for such applications may result in different loading conditions than those used in Ch 3 Ship Structures and Ch 4 Main and Auxiliary Machinery.

1.2.1 Clasification Society Register (hereinafter referred to as LR) can assist the Owner/Builder when selecting the appropriate notation and application of the Rules.

1.2.2 The Owner/Builder is recommended to approach LR early in the specification and design process to ensure clarity of requirements and compliance to enable the intended notation(s) to be assigned.

1.3.1 The application of the Rules is based upon scenarios of operation. Operational scenarios are comprised of a set of parameters and conditions for stern first operation in ice.

1.3.2 LR has used standard load scenarios to develop the requirements in Ch 3 Ship Structures. Where the ship’s operational scenarios differ from the standard load scenarios, the philosophy of the Rules is to be applied and documented in the Scenario Document as described in Ch 6 Direct Calculations and Non-Standard Load Scenarios.

1.3.3 The flow chart in Figure 1.1.1 Methodology for applying Rules to Stern First Ice Class Ships shows the methodology of application for the Rules.

Figure 1.1.1 Methodology for applying Rules to Stern First Ice Class Ships

1.3.4 The basic approach to application of the Rules is as follows:

1. Hull structure: apply relevant ice class Rules considering the stern as a bow with application of strengthening levels and extents based on the standard load scenarios. The level of strengthening applicable to the standard load scenarios is generally lower than a direct application of the ice class Rules using the ‘stern as a bow’ approach.

2. Propulsion units: apply the appropriate Chapters of Pt 5 Main and Auxiliary Machinery of the Rules for Ships for podded propulsion units or thrusters, with additional loads from the standard loads scenarios of the Rules.

3. Layout and arrangements: apply the Rules for Ships considering stern first operation.

1.3.5 The Scenario Document will identify where the scenarios deviate from the standard load scenarios and the prescriptive requirements of Ch 3 Ship Structures, Ch 4 Main and Auxiliary Machinery and Ch 5 Control and Electrical Systems of the Rules. This is represented by the dashed line in Figure 1.1.1 Methodology for applying Rules to Stern First Ice Class Ships.

1.3.6 Further information on the methods adopted for Rule application to SFIC ships may be found in Ch 7, 2.1 References to published papers 2.1.1.