Class NK beefs up box ship strength requirements

JANUARY 5, 2015 — ClassNK has released amendments to its Rules and Guidance for the Survey and Construction of Steel Ships that include updated structural strength requirements for container carriers.

These requirements have been in focus since the loss of the MOL Comfort, the large containership that sank in June 2013 after breaking in two.

In response to that loss, ClassNK established an Investigative Panel on Large Containership Safety and subsequently released a “Report on Structural Safety of Large Containerships” in September 2014.

Japan’s Ministry of Land, Infrastructure, Transport and Tourism (MLIT) Committee on Large Containership Safety released its own recommendations on requirements for large container ships in March 2015.

The International Association of Classification Societie (IACS) subsequently adopted a new Longitudinal Strength Standard for Containerships (Unified Requirement S11A) and Functional Requirements on Load Cases for Strength Assessment of Containerships by Finite Element Analysis (Unified Requirement S34).

In line with its action plan for rule amendments and the recommendations by the MLIT Committee, ClassNK has updated its independent longitudinal strength requirements in consideration of the effects of whipping (transient elastic vibration of the ship hull girder caused by wave impact loads on the hull such as slamming), and the effects of sea water pressure and container loads. The amendments also reflect the new IACS Unified Requirements (UR) S11A and S34.

These amendments will apply to containerships contracted for construction on or after April 1, 2016, three months before the application of the IACS UR S11A and S34.

“The development and application of the containership rule amendments reflects our firm commitment to providing the industry with the appropriate technical standards,” says Mr. Yasushi Nakamura, ClassNK Representative Director and Executive Vice President. “The new rules will contribute to even safer ship building and design and we will continue devoting our effort to further improving safety in the maritime industry.”

The amendments also include requirements related to the following:

• Propeller shaft and stern tube shaft surveys
• Welding procedures and related specifications
• Scope of application of fire-resistant cables
• Fire safety measures for vehicle carriers transporting motor vehicles powered by compressed hydrogen or compressed natural gas