«GUIDELINES FOR THE APPLICATION OF THE FINNISH-SWEDISH ICE CLASS RULES TRAFI/21816/03.04.01.01/2011 Helsinki, 20 December 2011 Guidelines for the ...»
GUIDELINES FOR THE APPLICATION OF
THE FINNISH-SWEDISH ICE CLASS RULES
Helsinki, 20 December 2011
Guidelines for the application of the Finnish-Swedish Ice Class Rules
Table of contents
2 The Status of the Guidelines
3 Implementation of the Finnish-Swedish Ice Class Rules in Finland and in Sweden
3.1 Implementation of the Finnish- Swedish Ice Class Rules in Finland 3.1.1 Ice Class Certificate of the FMA
3.2 Implementation of the Finnish-Swedish Ice Class Rules in Sweden 4 The Purpose and the Scope of the Rules
4.1 Design Philosophy 4.1.1 The Engine Power Regulations 4.1.2 Hull Structural Design 4.1.3 Propeller, Shafts and Gears 4.1.4 Application of the Rules for the Design of Ships for Other Sea Areas 5 General (Chapter 1 of the Rules)
5.1 Ice Classes 6 Ice Class Draught (Chapter 2 of the Rules) 7 Engine Output (Chapter 3 of the Rules)
7.1 Definitions (Section 3.2.1 of the Rules)
7.2 Existing Ships of Ice Class IB or IC (Section 3.2.3 of the Rules)
7.3 On Selection of the Propulsion System
7.4 Other Methods to Determine Ke or RCH 7.4.1 Other Methods to Determine Ke 7.4.2 Other Methods to Determine RCH 8 Hull Structural Design (Chapter 4 of the Rules)
8.1 Frame Connections
8.2 Vertical Extension of Ice Strengthening of Framing (Section 4.4.1 of the Rules)
8.3 Inclined or Unsymmetric Frame Profiles (Section 220.127.116.11 in the Rules)
8.4 Arrangement for Towing (Section 4.7.2 of the Rules)
8.5 Reduction in Corrosion Allowance (Section 4.3.2 of the Rules)
8.6 Propeller Clearance
8.7 Transom Stern
8.8 Bilge Keels 9 Rudder and Steering Arrangements (Chapter 5 of the Rules)
9.1 Ice Knife
9.2 Rudder Turning Mechanism
9.3 Bow Thrusters 10 Propulsion Machinery (Chapter 6 of the Rules)
10.1 Fatigue Design of Propeller Blade (Section 18.104.22.168 of the Rules)
10.2 Blade Failure Load (Section 6.5.4 of the Rules) Guidelines for the application of the Finnish-Swedish Ice Class Rules TRAFI/21816/03.04.01.01/2011 11 Miscellaneous Machinery Requirements (Chapter 7 of the Rules)
11.1 Sea Inlet and Cooling Water Systems 12 General Suitability for Winter Conditions
12.1 Low Ambient Temperature Appendices Appendix 1. Instructions for the application of a letter of compliance Appendix 2. Guidelines for the calculation of propeller thrust for open and nozzle propellers Appendix 3. Guidelines for bollard pull tests for determining the thrust of the propeller(s) Appendix 4. Guidelines for the verification of a ship’s performance for ice classes through model tests References
- Finnish-Swedish Ice Class Rules, 2010, (see www.trafi.fi, (23.11.2010 TRAFI/31298/03.04.01.00/2010)
- The Equivalence between the Finnish-Swedish Ice Classes and Ice Classes of Classification Societies, (see www.trafi.fi (23.11.2010 TRAFI/31299/ 03.04.01.00/2010)
- Act on the Ice Classes of Ships and Icebreaker Assistance (1121/2005) and Act on Fairway Dues (1122/2005), as amended, (see www.finlex.fi)
The Finnish Transport Safety Agency (Trafi) and the Swedish Transport Agency (STA) have developed the Finnish-Swedish Ice Class Rules in co-operation with classification societies.
The development of the rules started as early as in the 1930’s. The rules have been amended several times during the past years, for example in 1971 and 1985, and the latest version was published in 2010 (see Finnish Transport Safety Agency TRAFI 23.11.2010, available at www.trafi.fi). Most of the members of the International Association of Classification Societies (IACS) have adopted the Finnish-Swedish ice class rules and incorporated them in their own regulations on the classification of ships.
The purpose of these Guidelines is to provide classification societies, ship designers and shipyards some background information on the ideas behind the rules, to provide a harmonised interpretation for the implementation of certain parts of the rules, and to provide guidance on certain aspects of winterisation of the ship, not mentioned in the rules.
These Guidelines will be updated when needed and published at the websites of Trafi and the STA.
In general, Trafi and the STA accept class approval based on these Guidelines for design of vessels. The approval of Trafi or the STA for the engine power of a vessel is required in case the engine power is determined by model tests or by means other than the formulae given in the rules in regulation 3.2.5. Instructions for the application of a letter of compliance are given in Appendix 1. Model tests done for vessels contracted for construction on or after 1 January 2012 should be done according to these Guidelines.
These Guidelines replace all Guidelines issued earlier by Trafi or by the STA.
The Finnish and Swedish administrations provide icebreaker assistance to ships bound for ports in these two countries in the winter season. Depending on the ice conditions, restrictions in regard to the size and ice class of ships entitled to icebreaker assistance are enforced.
Winter traffic restrictions for ships are set in order to ensure smooth winter navigation and the safety of navigation in ice. Assistance of ships with inadequate engine output or ice strengthening would be both difficult and time-consuming. It would also not be safe to expose such vessels to ice loads and ice pressure.
The traffic restrictions are modified during the winter period depending on ice conditions. A typical strictest traffic restriction for ships bound for the Finnish ports in the eastern Gulf of Finland is, as a minimum, ice class IA and a minimum deadweight of 2000 TDW. A typical strictest traffic restriction for the ports in the northern Bay of Bothnia is ice class IA and a minimum deadweight of 4000 TDW. On the other hand, a lower minimum ice class is required for ships bound for the ports on the south-western coast of Finland where the ice
conditions are less difficult. A typical minimum requirement is ice class IC and a deadweight of 3000 TDW.
3.1 Implementation of the Finnish-Swedish Ice Class Rules in Finland Pursuant to section 12 of the Act on Fairway Dues (1122/2005 as amended by Acts1267/2007, 750/2008, 787/2008, 1257/2009 and 1309/2009), the Finnish Transport Safety Agency has, on 23 November 2010, adopted a regulation on the structural design and engine output required of ships for navigation in ice (see www.trafi.fi, 23.11.2010 TRAFI/31298/03.04.01.00/2010). The Act on the Ice Classes of Ships and Icebreaker Assistance has been issued as Act 1121/2005.
Pursuant to section 12 of the Act on Fairway Dues (1122/2005), the Finnish Transport Safety Agency has confirmed the list of ice class notations of authorized classification societies and the equivalent Finnish-Swedish ice classes (see www.trafi.fi, 23.11.2010 TRAFI/31299/03.04.01.00/2010). The ice class of a ship, which has an ice class of a classification society, is determined in accordance with this regulation.
The Finnish Transport Agency is responsible for giving icebreaker assistance for ships entering Finnish ports, if the ice conditions require that. This assistance service is included in the fairway due. The Finnish Transport Agency sets traffic restrictions for ships pending on ice conditions (see Rules for Winter Navigation at www.liikennevirasto.fi). Finnish icebreakers only assist ships that meet the ice class requirements set out in the FinnishSwedish Ice Class Rules 2010.
The fairway due imposed on a ship entering a Finnish port depends on the ice class of the vessel in accordance with the Government Decree on Fairway Dues (1122/2005) (see www.finlex.fi).
From 1 January 2006 Ice Class Certificates are no longer issued by the inspectors of the Finnish Transport Safety Agency at Finnish ports. The Ice Class of a ship will be determined on the basis of the Classification Certificate of the ship.
3.2 Implementation of the Finnish-Swedish Ice Class Rules in Sweden The STA is responsible for giving icebreaker assistance for ships entering Swedish ports. This assistance service is free of charge. The STA sets traffic restrictions for ships pending on ice conditions.
Swedish icebreakers only assist ships that meet the Finnish-Swedish ice class rules. Sweden also applies the same equivalencies to the Finnish-Swedish ice classes as Finland (FMA/31299/03.04.01.00/2010). The STA does not issue ice class certificates, but the ice class is based on the Classification Certificates of ships.
The Finnish-Swedish Ice Class Rules are primarily intended for the design of merchant ships trading in the Northern Baltic in the winter. The rules primarily address matters directly relevant to the capability of a ship to advance in ice. The regulations for minimum engine output (Chapter 3 of the Rules) can be considered to be regulations of an operational type.
Ships are required to have a certain speed in a brash ice channel in order to ensure the smooth progress of traffic in ice conditions. The regulations for strengthening the hull, rudder, propellers, shafts and gears (Chapters 4 to 6 of the Rules) are clearly related to the safety of navigation in ice. In principle, all parts of the hull and the propulsion machinery exposed to ice loads have to be ice-strengthened.
4.1 Design Philosophy
The Finnish-Swedish Ice Class Rules are intended for the design of merchant ships operating in first year ice conditions part of the year. Usually, compromises have to be made when ships are designed both for open water and ice conditions. The basic philosophy of the rules is to require, for operative reasons, a certain minimum engine power for ships with an ice class.
However, no general requirements for the hull form have been set. The structural strength of the hull and the propulsion machinery should be able to withstand ice loads with a minimum safety margin. For economic reasons excessive ice strengthening is avoided.
The Finnish-Swedish Ice Class Rules set the minimum requirements for engine power and ice strengthening for ships assuming that icebreaker assistance is available when required.
Special consideration should be given to ships designed for independent navigation in ice, or for ships designed for navigation in other sea areas than the Baltic Sea.
The design points for hull and propulsion machinery as well as for the ice performance (propulsion power) are all different. This reflects the fact that different ice conditions in
different ship operations form the critical design situations. The design points are as follows:
4.1.1 The Engine Power Regulations The regulations for minimum engine output are based on long term experience of the Finnish and Swedish icebreaker assistance in the northern Baltic Sea area. The number of icebreakers
is limited, and they have to be able to assist all ships entering or leaving the winter ports. Thus the minimum engine power requirement is “a matter of definition” to be decided by the Maritime Authorities depending on the number of icebreakers, number of ships in need of assistance, ice conditions, and maximum waiting time for icebreaker assistance. In Finland, the maximum average waiting time for icebreaker assistance is defined as about four hours.
The principle of the winter navigation system is that all ships meeting the traffic restrictions are given icebreaker assistance. Ice classed ship is assisted by an icebreaker when the ship is stuck in ice or is in need of assistance, because her speed has substantially decreased.
Normally the ship is assisted to (or from) the fairway entrance and after that the ship should be able to sail to the port on its own (or sail out of the port on its own), although the icebreaker often has to escort in particular smaller ships into the port. Most of the fairways leading to Finnish coastal ports are routed through the archipelago area. In archipelago areas the ice cover is stationary. The engine power requirements of the rules have been developed for navigation in brash ice channels in archipelago areas at a minimum speed of 5 knots. Thus the mere compliance with these regulations must not be assumed to guarantee any certain degree of capability to advance in ice without icebreaker assistance nor to withstand heavy ice compression at open sea, where the ice field may move due to high wind speeds. It should be also noted that the ice-going capacity of small ships may be somewhat lower than that of larger ships having the same ice class. This observation which is based on icebreaker operators experience may be attributed partly to the beneficial effect that larger inertia has in ice going.
4.1.2 Hull Structural Design
The rules for hull structural design (Chapter 3 of the Rules) deal with the local strength of the hull (plating, frames, stringers and web frames). Ice loads given in the Rules have been determined based on measurements on ships that sail in the Baltic Sea in winter. The situation where a ship is stuck in compressive and/or moving ice and large ice forces are acting on the parallel midbody is not considered in the rules. It is assumed that icebreaker assistance is available in such cases so that there is no time for a serious compressive situation to develop.
However, according to the experience of the Administrations, vessels strengthened to ice classes IA and IA Super rarely get damaged in compressive ice situations. During recent years, ice damages on the midbody of ships with ice class IC have been observed.
Recent observations on ice damages on ice strengthened vessels indicate that most of the damages on hull occur at an early stage of the winter season. These ships are probably operated at open sea at a high speed when the ice coverage is less than 100 %. Damages on the hull may thus occur when the vessel hits an ice floe at high speed.
4.1.3 Propeller, Shafts and Gears