France-based engineering company GTT has received an order from the Chinese shipyard Hudong-Zhonghua Shipbuilding (Group) Corp. Ltd. to design the LNG tanks—each representing a capacity of 174,000 m3 of two dual-purpose vessels capable of operating as efficient LNG Carriers and Floating Storage and Regasification Units (FSRUs).
These vessels will be built at Shanghai, China, for the owner Dynagas. Their delivery is due in 2021.
GTT will use the membrane cryogenic containment system NO96 GW, with glass wool insulation, for the LNG storage on board. The NO96 membrane system is a cryogenic liner directly supported by the ship’s inner hull. This liner includes two identical metallic membranes and two independent insulation layers.
The primary and secondary membranes are made of Invar, a 36% nickel-steel alloy, 0.7mm thick. The primary membrane contains the LNG cargo, while the secondary membrane, identical to the primary, ensures a 100% redundancy in case of leakage. Each of the 500mm wide Invar strakes is continuously spread along the tank walls and is evenly supported by the primary and the secondary insulation layers.
The primary and secondary insulation layers consist in a load-bearing system made of prefabricated plywood boxes filled with expanded perlite. The standard size of the boxes is 1m x 1.2m. The thickness of the primary layer is equal to 230mm; the thickness of the secondary layer is 300mm. The primary layer is secured by means of the primary couplers, themselves fixed to the secondary coupler assembly. The secondary layer is laid and evenly supported by the inner hull through load-bearing resin ropes, and fixed by means of the secondary couplers anchored to the inner hull.
Currently, 14 vessels in operation and 42 on order use this technology. In October, Samsung Heavy Industries ordered LNG tanks for a new FSRU scheduled for late 2020.
Earlier this month, GTT was chosen by Hudong-Zhonghua for the design of cryogenic tanks for nine LNG-fueled mega containerships. (Earlier post.)