This paper presents the extensive work performed to propose to the LNG industry an offloading solution fully compliant with EN1474 standard requirements using floating hoses. Between 2009 and 2013, a tandem offloading system using floating cryogenic flexible hoses developed and qualified to be able to transfer LNG in open seas. This arrangement was selected in order to combine the safety and the availability brought by the tandem configuration with the wide operational envelope provided by the use of floating hoses.
This system is composed of an innovative and compact hose storage system on the LNG Terminal allowing to store the hoses between two offloading operations, of a connection head (hose end termination piece) to ease the deployment/retrieval of the hoses and of a storage and maintenance platform for the connection head at the aft of the LNG Terminal, also allowing to replace a hose section in offshore conditions. On the LNG Carrier side, a bow loading platform is installed to ensure hoses connection even in exposed environmental conditions. The 20" ID cryogenic floating hoses to be used with this system has been developed and qualified in parallel with the development of the tandem system.
A red line for this development was to keep a similar level of safety, integrity and performance to onshore offloading operations. To fulfill this requirement, simple, robust and proven technologies have been considered for the main items of the system. The system incorporates a comprehensive panel of safety layers through monitoring, hardware, procedures and control philosophy providing protection for people and material during all steps of the offloading sequence. Regarding the performance, the system can transfer LNG at a flowrate of 10, 000 to 12, 000 m3/h using three hoses, which gives redundancy to transfer LNG even with one hose unavailable. To offer a high availability, dedicated solutions have been implemented in the system to withstand sea states with Hs up to 3.5 m for hoses connection and 4 m for cargo transfer and hoses disconnection.
This solution will help unlocking offshore stranded gas resources in many areas around the world through FLNG development.