CHIKSAN~R LNG MARINE LOADING ARMS ENHANCED FOR APPLICATION IN EXPOSED AREAS BRAS DE CHARGEMENT MARINE GNL CHIKSAN~R POUR APPLICATION SUR SITES EXPOSES

摘要

Shell Global Solutions Int. and FMC Technologies jointly developed an offloading system using a Chiksan~R Marine Loading Arm for loading of LNG in exposed areas. A 16-inch diameter Double Counterweighted Loading Arm ('DCMA-S' type) has been dynamically analyzed and tested utilizing a purpose-built dynamic analysis tool and test bench. The project, which started in 1999, concentrated on the development of a semiautomated connecting mechanism to assist the operator in making a controlled connection between the Chiksan~R hydraulic Quick Connect/Disconnect Coupler (QC/DC) and the Manifold Flange on the LNG Carrier (LNGC) under highly dynamic conditions. The connecting operation consists of crawling the QC/DC to the receiving flange on the LNGC using a constant-tension guide-cable between the base-riser of the Loading Arm and the Manifold on the LNGC. The closer the two flanges come together, the smaller the relative motions. Connecting operation tests have been successfully completed in 2002 for motions, which became available from scale 1:50 basin model tests on weathervaning barges with alongside moored LNGC. The Marine Loading Arm enhanced with the newly developed connecting mechanism showed that reliable and safe connections can be made for relative motions between the mating flanges in the range of 4m. For comparison, the conventional Marine Loading Arm will not be connected when the relative motion is more than 0.5m depending on motion frequencies. This enhanced Marine Loading Arm offers the captain of the LNGC a much wider mooring envelope. The new system therefore opens opportunities not only for Floating LNG Export and Re-gasification facilities, but also for more exposed onshore LNG plants and terminals, thus reducing the need for breakwaters and allowing consideration of different sites.