Two of the largest very large ethane carriers (VLECs) ever built will have a new Type B cargo containment system developed for efficient, long-distance, large-scale gas transportation, underpinning the growth in the global ethane cargo trade
Developed under a joint effort by China’s Jiangnan Shipyard and class society ABS, the Type B cargo containment system is called BrilliancE, with initial installation in two 99,000-m3, dual-fuel Type B VLECs ordered by Pacific Gas. The two ships represent an expansion for the Hong Kong-based shipowner beyond its core focus of liquefied ethylene gas carriers and very large gas carriers. Pacific Gas owns and operates five liquefied ethylene gas (LEG) carriers and 10 VLGCs, providing 3M tonnes of cargo capacity annually.
The two newbuild VLECs, H2624 and H2625, are to be delivered in Q4 2021 and Q1 2022, respectively. The minimum temperature for the vessels will be -104 C.
As a tradition, Jiangnan always gives a nickname to a newly developed ship. Jiangnan has assigned this novel VLEC as ’Bluebonnet,’ the state flower of Texas, the home state of ABS world headquarters.
Jiangnan’s design is the product of close co-operation between engineers at Jiangnan and ABS during the conceptual stage, which resulted in ABS granting approval in principle in September.
“These vessels are full of innovation that not only helps meet emissions objectives but also contributes to owners’ operational targets,” said ABS vice president, global engineering Bill Shi.
“The innovations behind this Type B VLEC design open a new chapter in mass ethane transportation,” claimed Jiangnan Shipyard (Group) Co Ltd chief of corporate technology Keyi Hu. “In this interconnected world trade, Jiangnan and ABS have demonstrated the added value of working in a partnership to bring these large Type B VLECs to the market,” he added.
Incorporating dual-fuel technology, each VLEC will be equipped with a shaft generator that can use ethane as fuel. “For this design,” said Mr Shi, “the ME-GI engine will be used as dual-fuel propulsion. Two Type C tanks can be optionally installed above deck. There are ways to handle BOG as well as supply ethane to the ME-GI-engine.” Each VLEC’s hydrodynamic line and internal space have also been optimised.
The VLEC’s BrillancE Type B cargo containment system is a critical part of the vessel’s optimisation. In discussing the new VLEC design with LNG Shipping & Terminals, Mr Shi said “Ethane is chilled and transported as a liquid. The pressure setting for the Type-B containment system is not very high – typically 0.25 bar g in seagoing condition and 0.40 bar g in harbour condition. He said the boil-off rate (BOR) with the newly developed containment system is expected to be among the very best from liquefied gas carriers. “For example, the typical 174,000-m3 membrane LNG carriers have a BOR of around 0.15%, depending on the layers and thickness of insulation panels.”
Mr Shi explained, “The BrilliancE Type B cargo containment system is made of independent tanks that are constructed of 5% nickel steel. Multi-layer insulation panels are installed on these tanks together with leakage path, detection and leakage mitigation measures.”
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