IACS Acts on MOL Comfort Report
The final report issued by Japan about the MOL Comfort break up concludes that the sea loads experienced by the vessel at the time of the casualty exceeded hull girder ultimate strength.
MOL Comfort was a 2008-built Bahamian-flagged 8,110teu container ship chartered by Mitsui O.S.K. Lines. It cracked and then broke in two in June 2013 sailing in heavy seas about 200 nautical miles off the coast of Yemen.
The report prepared by the Committee on Large Container Ship Safety (CLCSS) indicated that simulation work carried out demonstrated that the hull was weaker than the lateral and vertical bending loads it experienced at the time of the cracking. It suggests that the hull fracture originated from the bottom shell plates in MOL Comfort’s midship section.
The simulation included whipping motion loads. Whipping is the vibration of hull girders that occurs when the bow breaks free of the water and then re-enters.
The report recommends that International Association of Classification Societies (IACS) rules for container ships over 8,000teu should include lateral loads in the assessment of overall structural strength. They should also include whipping effects in longitudinal strength calculations.
IACS has confirmed that it has received the report and will study its recommendations. It will then make its findings public.
IACS launched an expert group on the structural safety of container ships at the beginning of 2014, which carried out a post MOL Comfort review, also taking into account a number of past casualties.
This work has resulted in the development of two new IACS Unified Requirements (URs)
- UR S11A which is a longitudinal strength standard for container ships
- URS 34 dealing with functional requirements for direct analysis by finite element method of container ships, including a set of loading conditions.
A statement released by IACS states that this ongoing work had already taken into account the CLCSS recommendations, because they take into account the effect of lateral loads on bi-axial buckling of stiffened panels (a phenomenon preceding loss of ultimate strength as correctly indicated in the report) and whipping on vertical bending strength.
With respect to the third recommendation of the report (representation of technical backgrounds), IACS confirmed that class societies rules already consider the strength of the ship under specified operating and environmental conditions corresponding to its entire life.
The two URs will be finalized in the coming months, but IACS warns that their URs are minimum common technical requirements to be incorporated into the rules of each individual member. URs are not intended to address all the strength aspects of hull structures, which remains the function and responsibility of each class society.
Mitsui OSK Lines is currently suing the vessel’s builder Mitsubishi Heavy Industries for damages. Claims against the shipbuilder have exeeded $500 million.