The 7,600 cu.m LNG-fueled vessel was ordered by Germany's Bernhard Schulte Ship management in late 2016 and is currently under construction to LR class at HMD's Ulsan, South Korea, shipyard.
By getting rid of ballast water, the vessel not only eliminates the need to fit a ballast water management system but also the need to comply with the Performance Standard for Protective Coatings for ballast tanks and related regulation, enabling maintenance costs savings.
To apply the ballast-free concept to the vessel, HMD gave careful consideration to the special hull form with dead rise (the upward slope of a ship's bottom from the keel to the bilge); forward "engine room and deckhouse" and a twin propulsion system with azimuth thrusters so that the vessel can retain its damage stability and easily control the trim and heel without ballasting.
HMD's first obstacle was the speed management by dead rise. In general, says LR, dead rise is known to help improve the ship's stability, which is critical to this ballast-free vessel, but it is also likely to deteriorate the vessel's speed performance. To counteract this, HMD focused heavily on the hull form optimizsation and successfully developed a better performing dead-rise hull form, confirmed through the wet model test.
Another key feature of this vessel that enables it to be ballast-free is the twin propulsion system with two azimuth thrusters. The smaller diameter of propellers fitted in the azimuth thrusters enables the vessel to achieve full immersion in all operational conditions.
LNG will be stored in two independent IMO type C tanks which are designed to contain the LNG with a minimum temperature of minus 165° C and maximum vapour pressure of 3.75 bar(g), and can be transferred to an LNG-fuelled vessel at the rate of about 1,250m³/hour through the cryogenic flexible hoses without ballasting and/or de-ballasting operation. Additionally, the natural vaporizing gas from the bunkering vessel and the returned boil-off gas from the LNG-fueled vessel will be compressed up to 220 bar(g), stored in two sets of 40 feet container and used for propulsion fuel and electric.
Seung-Ho Jeon, SVP of HMD Initial Planning Division, said: "The ballast-free concept will be made a reality by the technology expertise of HMD. We aim to stand out in the field of eco-friendly business practice."
"We are delighted to work with the shipyard helping the marine industry bring innovative designs to the market," said Jin-Tae Lee, Ph.D, LR's Korea Chief Representative & Marine Manager. "We believe that this design is another remarkable development for HMD to realise the industry's need for safe, efficient and clean requirements in the shipping industry worldwide."
The ballast-free concept not only eliminates need for the vessel to install a ballast water treatment system, it also removes the need to comply with the Performance Standard for Protective Coatings for ballast tanks and related regulation, enabling maintenance costs savings.