BV class for Chinese ultra-large boxships

The 16,000teu vessels will be the largest container ships built in China to date. One will be built at the Shanghai Waigaoqiao Shipbuilding (SWS) yard, and the other two at Shanghai Jiangnan Changxing Heavy Industry, part of which came under the management of SWS earlier this year.

Accoding to BV, in recent years, Chinese shipyards have secured orders for increasingly large box ships, and the three new 16,000teu ships are only fractionally smaller than the largest container vessels being built today in Korea. The design was developed by the Marine Design and Research Institute of China (MARIC) in co-operation with BV, which performed the drawing approval and conducted a thorough structural examination.

The vessels will have an overall length of 399m, with 54m beam and 16m draught. Special consideration has been given to hydroelastic design (whipping and springing) issues, which are said to be particularly important for this size of ship. A hydroelastic examination has been performed using BV’s Homer software in order to take into account extreme whipping loads due to slamming and additional fatigue damage due to springing, factoring in the elastic structural response of the ship. This review is intended to offer a higher level of safety compared to the rigid approach traditionally adopted to such issues, and is mandatory under BV Rules for ULCSs of 300m and above. On the strength of this examination, BV’s WhiSp2 notation has been assigned to the ships.

The vessels will be also granted BV’s VeriSTAR HULL DFL 25-year notation, which certifies various structural details, including hatch corners and coamings, for 25 years of fatigue life, following a spectral fatigue analysis with a 3D finite element analysis model. BV adds that the importance of fatigue for large container ships, which generally lack torsional rigidity and become more elastic with size, has been confirmed by real measurements on board ULCSs in BV class.

The 16,000teu ships will be able to operate at a maximum speed of over 23 knots with a single-screw propeller directly coupled to a 69,000kW two-stroke electronically controlled engine. The vessels’ environmentally friendly profile is covered by class notations Cleanship and FORS. The latter incorporates special arrangements to ensure that the ship’s fuel oil tanks are safely emptied in case of emergency, minimising the risk of pollution. Steel cutting for the new vessels is due to begin in 2014 and the ships are scheduled for delivery in 2015.