This is a reminder to owners and managers of vessels with DNV GL/DNV ice class Ice(1A), Ice(1A*) or Ice(1A*F) or GL ice class E3 or E4. The Finnish Transport Safety Agency (Trafi) introduced a retroactive engine output requirement in 2002 for ships whose keel was either laid or a similar stage of construction before 1 September 2003. To retain the equivalent Finnish ice class (e.g. for operation in the Baltic Sea), the ship must comply with the retroactive requirement on 1 January of the year when 20 years have elapsed since the year the ship was delivered.
Relevant for ship owners and managers as well as design offices.
OThe retroactive requirement for vessels with the highest ice classes was introduced in Trafi’s Ice Class Regulations (hereafter “the Finnish ice class”) in 2002, which has remained unchanged since then. The current requirement is given in TRAFI/494131/03.04.01.00/2016, which came into force on 1 December 2017.
Vessels whose keel was either laid or at a similar stage of construction before 1 September 2003 can only keep their current Finnish ice class after 1 January of the year the vessel turns 20 years if the installed engine power complies with the retroactive minimum requirement. This engine power requirement has increased and may be higher than the installed power.
If the minimum engine output required by Trafi is not met, a lower equivalent Finnish ice class may be considered. The possible lowering of the Finnish ice class does not affect the ice class given by the class society, but it will influence Finnish fairway dues and result in traffic limitations to Finnish and Swedish ports.
There are three options for proving that the engine output requirement is met:
- Simple but conservative calculation formulas according to Trafi rules. The advantage of these formulas is that information about the hull form is not needed.
- If the vessel does not comply with the simple formulas, more complex calculations can be carried out using certain hull form data as input. The advantage is that these calculations are less conservative and require less engine power. At the same time, to determine the input values, a lines plan or electronic hull form representation is needed. For older vessels, such data can be difficult to obtain.
- Model tests in an ice basin can be carried out to determine the resistance of the hull in ice and to assess the power needed. The model tests normally result in much lower power requirement, but they are expensive and time-consuming. In addition, information about the hull lines is also needed. Such a model test should be discussed in advance with Trafi or the Swedish Transport Agency.
Recommendations
- Timely action is required to avoid downgrading or loss of equivalent Finnish ice class for older vessels (keel laid before 1 September 2003) with a high ice class – Ice(1A), Ice(1A*), Ice(1A*F), E3 or E4 – when reaching 20 years of age.
- Upon request, and subject to a fee, DNV GL may verify compliance with the retroactive Finnish ice class rules engine output requirement. Confirmation of compliance will be entered in the vessel’s Appendix to the Classification Certificate or Technical File. If the installed engine power is found to be insufficient, the DNV GL/DNV/GL ice class notation will be kept, but it will be specified in the Appendix to the Classification Certificate or Technical File which Finnish ice class the vessel complies with.
References
Trafi – Ice classes of ships including current and past regulations and equivalences
Contact
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