New DD Scheme for Bahamas-Flagged Passenger Ships

DNV initiated a study in 2023 to investigate whether the age limit of 20 years for DD scheme may be waived without adversely affecting the ship’s maintenance.

Concept

A DNV project demonstrated that passenger ships over 20 years of age can also apply for in-water surveys (IWS) instead of dry-docking. Following the DNV analysis, The Bahamas Maritime Authority (BMA) removed the 20-year age limit in the DD scheme, allowing applications for all passenger ships under the provisions described in the revised maritime notice MN075.

Why passenger ships?

The design, and most importantly, the operation, of passenger ships differ significantly from typical cargo ships (e.g., oil tankers, dry cargo). While the rule-based design life of cargo ships is 20 to 25 years for strength/fatigue considerations, a passenger ship 20 years of age has only entered the middle of its operational life, with a typical passenger ship’s life “expectancy” being 40 years.

Passenger ship operators often re-route or alter itineraries to avoid storms, significantly reducing the risk of extreme loading. Real-time AIS data allows for the extraction of the actually encountered wave loading, which then can be compared with the design’s rule-based extreme and fatigue values from the DNV Nauticus Hull software.

Findings from the analysis

An in-depth analysis of the historical survey records extending over the last 35 years of the DNV fleet of passenger ships revealed that there is no increase in class survey findings for passenger ships over 20 years of age compared to vessels younger than 20 years. Furthermore, the analysis of the last 40 years’ damage records on the bottom structure and equipment revealed no major concerns or increased risks to the ship’s safety regarding strength, propulsion and steering/navigation.

These conclusions were well received by the BMA and opened the possibility for Bahamas-flagged ships to apply for a five-year dry-docking, DD scheme period.

How to qualify for the new DD scheme

One important provision to qualify for the “one-in-five” dry-docking DD scheme is that a ship-specific study must be prepared by DNV to evaluate the condition of the bottom or inner bottom structure and the propulsion, steering and navigation equipment. The study will provide the BMA with a clear conclusion on whether DNV supports the scheme for the subject vessel. The conclusion must be backed by the relevant documentation and/or calculations.

The process to apply for the “one-in-five” dry-docking DD scheme for ships over 20 years of age is described in the flowchart in Appendix A in the pdf.

Recommendations

Ship managers of passenger ships are encouraged to perform additional surveys, and based on Class recommendations, perform extra servicing and repairs during dry-docking. This should be done alongside a targeted occasional survey and before the final BMA application for the in-water survey (IWS), which is less costly compared to a dry-docking survey.

References

• Bahamas Maritime Authority MN075 – Passenger Ship Bottom Inspections, Rev 1.1
• SOLAS Ch.I Pt.B Reg.7
• IMO circular MSC.1/Circ.1348
• IMO Resolution A.1186(33)

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