Floatability assessment

Watertight subdivision is vital for ship stability and survivability to protect life, property and the marine environment in cases of hull damage after collision or grounding. The number of openings in watertight bulkheads on passenger ships is to be kept to a minimum in accordance with SOLAS regulation II-1/13.1 (previous SOLAS regulation II-1/15.1). In order to maintain watertight subdivision, while allowing for the safe and effective operation of the ship, all watertight doors are to be kept closed during navigation, except in certain limited circumstances when passenger ships operators may have the operational need to keep one or more WTDs opened while at sea.

The scenario

SOLAS regulation II-1/22.3 (previous SOLAS regulation II-1/15.9.2), allows a WTD to be temporarily opened to permit the passage of passengers or crew, or when work in the immediate vicinity of the door necessitates it being opened. In this case, the door must be immediately closed when transit through the door is complete or the work is finished. Additionally, SOLAS regulation II-1/22.4 (previous SOLAS regulation II-1/15.9.3) permits certain watertight doors to remain open during navigation but only if considered absolutely necessary to the safe and effective operation of the ship's machinery or to permit passengers normally unrestricted access throughout the passenger area.

Deliverables

In order to make the above determinations, the Operator shall provide the below  information for each ship:

• NAPA model (inclusive of loading conditions and damage stability calculation according to SOLAS Ch II-1 probabilistic or deterministic) depending on the vessel's keel laid date
• number and location of the watertight doors to remain open during the navigation
• general arrangement plan (all decks including Tank Top)
• capacity plan
• damage control plan
• plan showing the position of openings through which progressive flooding may take place
• cross flooding arrangement (if available)
• justification.

Why RINA?

RINA delivers to the Operator  the floatability assessment of each of the managed ships with the purpose of determining the impact of open watertight doors on ship survivability under SOLAS regulation II-1/22.4 and as foreseen by IMO MSC.1/Circ.1380 Appendix 1.

Having carried out several floatability assessments for cruise vessels of different size and typology, and with huge expertise of their operational aspects, RINA can quickly understand the needs of a Cruise Operator to keep one or more WTDs opened while at sea.