There is currently a transition of the regulatory approach from IMO, improving SOLAS which historically has been applying a risk based approach when using an alternative fuel. At present, prescriptive regulations are developed to enhance an easy and safe practical implementation.
What features are subject for classification society approval?
All features or systems of a ship that may cause multiple casualties or total loss of ship, if failing, are subject for flag approval. Examples: Escape routes, stability and systems for fire- detection and extinguishing. The regulatory framework is outlined in SOLAS and is published by the International Maritime Organization (IMO).
If the governing flag state have plan approval capacity, they will review the design documentation according to SOLAS. Example: Swedish Transport Agency. The most common situation today, however, is that the governing flag state does not have permanent staff engaged in plan approval duties. These flag states are referred to as open international registers. Examples: Liberia and Bahamas. The class society is then delegated the task to issue a statutory approval on the flag state’s behalf.
So what is left for class approval? The remaining systems and features that may endanger passengers/crew or result in property damage, if mal- functioning. Examples: Structures and welding, machinery, electric installations and automation.
Of course, there is a thin line between what is subject for flag state approval and class approval. In some areas the scopes are overlapping. Even if a ship’s system is for flag consideration, per definition, it may well be that the contracted class society has their own rules on top of SOLAS. Similarly, a flag state may have stricter national rules than what is required by SOLAS.