The Soft Yoke Mooring and Offloading System for LNG Offloading Applications

The ever-rising need for energy and environmental issues have propelled LNG as one of the most promising source of clean energy for the near future. LNG differs greatly from oil when it comes to loading and offloading in at least two respects. Firstly, owing to its temperature at atmospheric pressure (−162°C), Liquefied Natural Gas does not lend itself to offloading via the well-known floating hoses routinely used for oil. Instead, specially designed articulated steel structures are used in all jetty terminals around the world. Secondly, the very nature of long-term contracts negotiated with utility companies requires regular, uninterrupted LNG supply to their network. This requires extremely high availability figures for import/export terminals or floating, moored LNG producing facilities. A new concept based on the well-known soft yoke principle has been developed whereby the yoke structure has the dual function of mooring the LNG carrier to a fixed import terminal or to the stern of a permanently moored Floating LNG (FLNG) FPSO and of supporting the rigid pipe fluid transfer system. Whilst all soft yoke systems built to date permanently moor an oil FPSO to a fixed jacket structure, the new SYMO^® system is designed as a temporary mooring for a fleet of dedicated LNG carriers. This paper addresses new engineering challenges associated with the SYMO^® system.