ディープデッシュ工法を用いた「HAKURYU-5」の延命およびバリアブルデッキロード増強工事の概要

抄録

Japan Drilling Co., Ltd. (JDC) owns and operates HAKURYU-5(H-5). It was built in 1977 at Mitsubishi Heavy Industries' Hiroshima Shipyard, and has been working over 30 years. To meet the requirements of the deepwater drilling demand, in 2004 JDC undertook a project that would extend the life and enhance the variable deck load (VDL) of H-5. Five engineering firms were invited to put forth proposals. EXMAR Offshore Company (EOC) was selected based on their remarkable ‘Deepdish’ concept.
The Deepdish concept features transverse and diagonal braces formed as a unitized structure joined to the under side of lower hull.
Basic design of Deepdish, including reinforcement of existing structure, was performed by EOC and approved by ABS Houston. Detailed design, made in January 2007, and fabrication of Deepdish was conducted by IHI Marine United (IHIMU). Deepdish was fabricated before the H-5 arrived at shipyard.
Fabrication work of Deepdish began in March 2008 and was completed on October 14, 2008. H-5 arrived at IHI Aichi Works in Chita city on September 15, 2008 and docked in on October 20, 2008. Upon completion of dry-dock work, she docked out on February 7, 2009. The duration of dry-dock was three and half months, which is much shorter than conventional timeframes. The project was completed and H-5 sailed out on February 26, 2009 for operations offshore Vietnam.
The key to the success of the project was to foresee potential problems and to prepare candidate solutions. These included, for example, strategies for minimizing the gap between the new and existing structures and maintaining the position control when mating the Deepdish to the H-5.