Consulting Naval Architects OSK-ShipTech A/S

Denmark

World Wide Marine Consultancy Services Since 1966

Gotlandsbolaget – Newbuilding Worlds most powerfull LNG ferry

  Concept Development   Tender and tender

evaluation   Contract negotiation   Basic Design   Interior Design

Samsø – Newbuilding Denmark's first domestic LNG powered ferry

  Concept Development   Project Management   Interior Design   Tender and tender

evaluation   Contract negotiation

Intact Stability

• Within IMO, the Ship Design and Construction (SDC) subcommittee has been instructed to develop 2nd generation intact stability criteria

• Reasons: - Present stability criteria are based on outdated data. - Present stability criteria do not consider all possible failure

modes appropriately - Modern hull forms may not be considered correctly

• During the last decade discussions on dynamic intact stability criteria have been dominated by academia

• Now the first workable proposals are available

Failure Mode 1 – loss of stability

Failure Mode 2 – Parametric roll

Failure Mode 3 – Surf-Riding/ Broaching

Failure Mode 4 – Dead ship condition

Failure Modes 5 – Excessive acceleration

Level of approach

Accuracy

Explanation

Level 1 •  Identify possible vulnerability •  High simplification •  High conservativeness

Level 2 •  Mathematical approximation •  Moderate conservativeness

Level 3 (direct stability assessment)

•  Numerical approximation •  Low conservativeness

Operational guidance

•  Restriction when criteria are not met

DAMAGE, safe return to port

Requirements applicable to all passenger ships built after July 2010 Having :

Regulation II-2/21.1 • a length of 120 m or more, or • three or more main vertical zones

Note! Also applicable to ROPAX vessels as well. Summary of requirements - Casualty Threshold, Safe Area, Essential Services and Safe Return to Port concepts. - Orderly Evacuation and Abandonment after a casualty

Casualty Threshold (SOLAS Reg. II-1/8-1 & II-2/21) When damage does not exceed the casualty threshold, essential systems should remain operational and provide for systems to support safe area(s) Casualty thresholds are defined for: Flooding:

flooding of any single watertight compartment Fire:

loss of space of origin up to the nearest “A” class boundaries

DAMAGE, safe return to port

Concept – segregation of conventional diesel propulsion plant

Concept – Contra-rotating pod unit

Concept – diesel electric propulsion plant

Cross-flooding – Historic Background

•  In connection with an EU research project FLOODSTAND (2009-2012) errors in the formulas for determination of time to cross-flood through ducts was observed!

•  This resulted in a revision of MSC.245(83) and MSC.362(90) was thereby adopted by MSC 14 June 2013.

•  The guidelines in the 3 resolutions are not mandatory (it is up to Administrations whether they will use them).

•  The 3 resolutions does not supersede each other.

•  In order to calculate the time to cross-flood through a ducts or pipe the friction coefficients k within the system must be known.

Questions

95% of all casualties occurs on Domestic routes - Are the rules and regulations of today for passenger vessels too sophisticated and do they enhance safety where needed? Goal based standards are difficult to understand and use in practice – does this create a conflict between operators, designers and approval authorities? Are ferries safe enough?