Flexible Line Recovery With Slack Buffer for Continuous Sectioning
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Solution Overview
Problem
Current methods for decommissioning offshore fluid production sites are inefficient and costly due to frequent stops of tensioners in line recovery systems, leading to reduced productivity and increased maintenance issues.
Innovation Solution
The method involves creating an intermediate slack region of the flexible line between the lifted region and the processing stage to compensate for velocity differences, allowing continuous lifting while processing the upper end region into shorter sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the tensioners are stopped frequently to process the upper end region of the flexible line, then the processing can be performed, but the productivity is reduced and maintenance issues increase
Solution Approach 1:
The flexible line is divided into an upper end region being processed and a lower end region continuing to be lifted. The processing stage is separated from the lifting system, allowing independent operation of each function without mutual interference.
Solution Approach 2:
An intermediate slack region is introduced between the lifting system and the processing stage. This slack region acts as a buffer that decouples the continuous lifting motion from the intermittent processing operations, allowing the lifting tensioners to continue operating without stopping.
2Ease of manufacture
If the tensioners are stopped frequently for processing, then the upper end region can be divided into sections, but maintenance costs increase due to frequent stops
Solution Approach 1:
The lifting tensioners operate continuously without interruption throughout the processing operation. The useful action of lifting the flexible line is maintained continuously while the processing of the upper end region is performed independently on the processed section.
3Productivity
If the line recovery system operates continuously without stops, then productivity improves, but it becomes difficult to process the upper end region into sections
Solution Approach 1:
The flexible line is segmented into a processed upper end region and an unprocessed lower end region. The upper end region is divided into manageable sections while the lifting system continues to process the lower end region, enabling both continuous operation and sectioning.
Solution Approach 2:
The upper end region is brought to the processing stage and prepared for sectioning before the actual cutting or processing occurs. This preliminary positioning allows the processing equipment to work on a stationary section while the lifting system continues operating on the moving line.
4Ease of manufacture
If the velocity of the lifted region and upper end region are different, then processing can occur, but gaps or slack regions create operational complexity
Solution Approach 1:
The intermediate slack region serves as a mediator that absorbs the velocity difference between the continuously moving lifted region and the intermittently processed upper end region. This slack region accommodates the speed variations without requiring complex synchronization mechanisms.
Solution Approach 2:
The system dynamically adjusts the length of the intermediate slack region during operation. The slack region expands and contracts naturally to accommodate the varying velocities of the lifting system and processing stage, providing automatic adaptation without complex control systems.
Data Source
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AI summary
The method comprises : - progressively lifting the flexible line (11) from the body of water (14) on or/and above a recovery installation (10) using a line recovery system (22); - repeatedly processing an upper end region (26) of the flexible line (11) beyond the line recovery system (22) to divide the upper end region (26) in several line sections (12) in a processing stage (24) of the recovery installation (10); - creating an intermediate slack region (30) of the flexible line (11) between a lifted region (108) of the flexible line (11) in the line recovery system (22) and the upper end region (26) in the processing stage (24) to compensate an instantaneous velocity difference between a velocity of the lifted region (108) and a velocity of the upper end region (26).