The Submerged Yoke System (SYS) is based on proven technological components by Advanced Production and Loading (APL™) and is designed for long-term unattended service. All critical components are designed for lifetime use along with inspection and maintenance access.
An SYS base anchored to the seabed integrates the pipeline end manifold (PLEM) and a mooring yoke with a chain connection to the floating production, storage, and offloading (FPSO) vessel at its bow. The yoke weight and heights are adjusted to cater for any vessel size and high sea states. A column transfers the torque and supports the topsides inclusive of the swivel stack and associated piping and valves. Flexible jumpers transfer oil, gas, water, and utilities to and from the FPSO vessel in a U-shaped catenary.
The SYS allows for scheduled decoupling between the offshore and shipyard work. Initial installation of SYS can be completed independently of the FPSO vessel conversion or new build. The system is installed offshore before FPSO vessel arrival at the field. Upon arrival, the vessel hooks up to the SYS with the help of tugs, but no construction vessel is required to assist.
The SYS provides for reduced bending moments on the structure compared with traditional jacket soft yoke. In turn, reduced bending moments allow for a more cost-efficient structure that is less prone to fatigue issues.
The system also allows for high sea states in very shallow waters—up to 10 m Hs in water depths of 42 m and 5 m Hs in depths of 18 m.
During offshore installation, the SYS chain connection to the FPSO vessel is decoupled from the yoke. The yoke is controlled by a chain jack winch, and the chains are load-free while the connection is performed.
Vessel modifications are in the bow area and are limited to chain connecting arms, gutters, and equipment layout as opposed to bow integration of a yoke.
SYS in ice
The SYS has a minimum sea-surface interface. Its column diameter can further be equipped with a conical-shaped ice breaker that allows the system to sustain up to 50 cm of ice sheet.
SYS for high-pressure liquefied natural gas regas
The SYS can be used to moor floating storage regasification units.