Keeping the ice class
Under the Finnish–Swedish ice class regulations, older vessels with DNV GL or DNV ice class Ice(1A), Ice(1A*) or Ice(1A*F) or GL ice class E3 or E4 may lose their ice class if the engine output fails to meet the minimum requirement. DNV GL explains the implications and can support owners in performing and verifying the necessary calculations.
Operators of vessels with ice class need to comply with the requirements of the Finnish–Swedish ice class regulations (FSICR), which have been incorporated into the rules of the classification societies. The year of build of a vessel determines which set of regulations applies to it. Provisions on the application of the various sets of regulations are currently laid down in the 2017 regulations.
For operators with a vessel keel-laid before 1 September 2003 it is important to comply with the minimum power requirement of the current Finnish ice class rules (TRAFI/31298/03.04.01.00/2010) when the vessel reaches 20 years of age. Due to the fact that the average age of MPVs is rising, many vessels now reach their twenties, and owners are approaching DNV GL’s experts for help to maintain their vessel’s ice class. Jan Rüde, Ship Type Expert MPV at DNV GL, shares some insights on the steps owners need to take.
How can an owner avoid losing ice class?
Jan Rüde: A vessel can only keep its current Trafi ice class if its installed engine power is proved to meet the minimum requirement. This engine power requirement is higher than what the vessel was originally designed for.
What happens if the vessel does not comply?
Rüde: If the minimum power requirement for the ice class is not met, lower ice classes can be assigned, provided the power of the ship is sufficient. This means that a vessel may be downgraded to a lower ice class, or lose its ice class altogether. Being assigned a lower ice class does not directly affect the ice class given by the classification society as such but will have an effect on Finnish fairway dues and traffic limitations in Finnish and Swedish ports.
How can an owner prove that the engine power requirement is being met?
Rüde: There are three possibilities to prove that the engine power requirement is met:
1. Carry out simple but conservative calculations according to Trafi rules. The advantage of these formulas is that no information about the hull form is needed.
2. If compliance cannot be demonstrated using the simple formulas, more complex calculations can be performed using certain hull form data as input. The advantage is that these calculations are less conservative and have a lower engine power requirement. However, to determine the input values, a lines plan or electronic hull form representation is needed. These data may be difficult to obtain for an older vessel.
3. Ice basin model tests can be carried out to determine the resistance of the hull in ice and the resulting power requirement. Model tests typically result in a much lower power requirement but are expensive and time-consuming. In addition, information about the hull lines is needed.
How can DNV GL support its customers to facilitate the process?
Rüde: In any case, timely action is required to avoid downgrading or loss of ice class for older vessels. DNV GL supports its customers with approval of ice powering calculations which can be submitted to Trafi. Customers may have the calculations carried out by an engineering company and then submit them to DNV GL for approval, or task DNV GL directly to carry out the calculations. It is also possible to search the database for sister vessels for which Trafi acceptance is already available, and to submit the acceptance documents for additional vessels.