Ship-to-ship LNG Transfer Heading Control via Adjustable Mooring
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Solution Overview
Problem
Conventional ship-to-ship transfer of liquefied natural gas (LNG) at offshore mooring systems faces challenges in maintaining safe heading control, particularly in locations with adverse weather conditions, leading to risks of vessel movement, cargo sloshing, and potential damage due to the inability to manage external forces like wind, waves, and currents.
Innovation Solution
A method and system for heading control during LNG transfer, involving the use of thrusters and adjustable spread mooring lines to rotate the FSRU and LNGC, allowing them to be aligned with the predominant oceanic and weather forces, thereby minimizing unwanted movement and sloshing risks, and enabling safe and efficient transfer operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the FSRU is allowed to weathervane freely at the offshore mooring system, then the FSRU can minimize damage from external weather forces, but the FSRU cannot maintain a stable heading for safe STS transfer operations
Solution Approach 1:
The patent applies dynamics by making the mooring system adjustable rather than fixed. The spread mooring lines can be reconfigured in terms of length and arrangement to dynamically adapt to different operational requirements. This allows the system to transition between a more rigid configuration (for heading stability during STS transfer) and a more flexible configuration (for weather response), resolving the contradiction between maintaining stable heading and adapting to weather conditions.
2Reliability
If the FSRU maintains a fixed heading during STS transfer, then vessel stability is improved, but the FSRU becomes vulnerable to damage from adverse weather conditions
Solution Approach 1:
The patent applies preliminary action by pre-configuring the spread mooring lines before STS transfer operations begin. The lines are arranged and tensioned in advance to establish the desired heading and stabilize the FSRU position. This preliminary configuration ensures that when transfer operations commence, the vessel is already in the optimal stable position, preventing excessive movement while still allowing the system to respond to weather forces through the flexible mooring arrangement.
3Reliability
If spread mooring lines are used to control FSRU heading, then heading stability is improved, but the complexity of the mooring system increases
Solution Approach 1:
The patent applies segmentation by dividing the mooring system into multiple independent spread mooring lines rather than using a single complex mooring arrangement. Each line can be independently adjusted in length and tension, allowing for precise control of the FSRU heading. This segmented approach simplifies the overall system by using multiple simple, adjustable components rather than one complex fixed system, while still achieving the desired heading stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the safety and reliability of LNG transfer operations by reducing vessel movement and sloshing risks, allowing for continuous and efficient cargo transfer even in challenging weather conditions, thereby improving operational safety and reducing the risk of damage to vessels and equipment.
Implementation Method 1
A method and system for heading control during LNG transfer, involving the use of thrusters and adjustable spread mooring lines to rotate the FSRU and LNGC
Implementation Method 2
involving the use of thrusters and adjustable spread mooring lines to rotate the FSRU and LNGC, allowing them to be aligned with the predominant oceanic and weather forces
Data Source
AI summary
A method and system for heading control during ship-to-ship (STS) transfer of liquefied natural gas (LNG). A method for heading control during STS transfer of LNG while moored on a buoy includes berthing a floating storage regasification unit (FSRU) to a buoy at a forward end of the FSRU, holding a stern of the berthed FSRU at a first heading with a bow of the FSRU pointing into a current, docking an LNG carrier (LNGC) alongside the berthed FSRU, mooring the LNGC to the berthed FSRU in a double-banked configuration at the first heading, adjusting the first heading of the FSRU and moored LNGC to a second heading with the bow of the FSRU and a bow of the LNGC pointing into a swell, and transferring LNG from the LNGC to the FSRU while the FSRU and moored LNGC are pointed into the swell.