Three-Way Motion Compensation Lifting System for Offshore Vessels
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Solution Overview
Problem
Existing lifting systems in offshore operations face challenges such as imbalance of stress, mechanical collisions, and inefficient synchronous lifting due to wave-induced movements, with complex structures and low efficiency in heave compensation.
Innovation Solution
A lifting system with a three-way motion compensation function, comprising a main arm, mobile carts, supports, and a lifting mechanism with hydraulic motors and locking mechanisms, allows for synchronized movement and compensation in three directions, preventing collisions and maintaining stable lifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heave compensation is used in the prior art, then vertical direction compensation is provided, but the compensation effect is unsatisfactory and the structure is complex
Solution Approach 1:
The lifting system is divided into multiple independent mobile carts (first mobile cart, second mobile cart, etc.), each capable of independent motion compensation. This segmentation allows each cart to handle specific compensation tasks, improving overall compensation effectiveness while keeping individual cart structures relatively simple.
Solution Approach 2:
The system transitions from single-direction (vertical heave) compensation to multi-dimensional compensation by adding mobile carts that can move along rails in multiple directions. The first mobile cart moves along the first rail for horizontal compensation, while the second mobile cart moves along the second rail, achieving compensation in multiple dimensions simultaneously.
2Force
If a double-vessel hoisting method is used, then lifting force is increased, but the structure becomes complex and water filling/discharge takes long time
Solution Approach 1:
The mobile carts are equipped with counterweight tanks that can be filled with water to provide counterbalancing force. This allows the system to achieve force compensation without complex mechanical structures, using the simple principle of water ballast adjustment to balance loads and improve lifting capability.
Solution Approach 2:
The system uses hydraulic cylinders to control the movement of mobile carts along rails and to manage water ballast in counterweight tanks. This hydraulic control system provides efficient force multiplication and precise position control, achieving high lifting force with relatively simple actuation mechanisms.
3Force
If a double-vessel hoisting method is used, then lifting force is increased, but lifting efficiency becomes low
Solution Approach 1:
The mobile carts can move continuously along the rails to compensate for vessel motions in real-time during lifting operations. This continuous motion compensation ensures that the lifting force is constantly optimized, maintaining high lifting efficiency throughout the entire operation without interruption for manual adjustments.
Solution Approach 2:
The system replaces complex mechanical linkage systems with a more efficient combination of hydraulic actuation and controlled motion along guides. The hydraulic motors provide direct force application, while the rail-guided mobile carts provide smooth, low-friction motion, together achieving high lifting efficiency with reduced mechanical complexity.
4Adaptability or versatility
If vessels move with waves, then devices on vessel body move with wave, but this causes imbalance of stress, mechanical collision, and constant change of lifting position
Solution Approach 1:
The system uses dynamic motion compensation where mobile carts can actively move along rails in response to real-time vessel motions. The carts are equipped with sensors and control systems that detect vessel position changes and automatically adjust cart positions to maintain stable lifting, transforming the static lifting system into a dynamic one that adapts to wave conditions.
Solution Approach 2:
The lifting system incorporates feedback mechanisms through sensors on mobile carts that continuously monitor vessel motion and lifting position. This feedback information is used by control systems to adjust cart positions and lifting forces in real-time, creating a closed-loop control system that maintains lifting stability despite wave-induced vessel movements.
Data Source
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Figure 3~5
Figure 6~7
AI summary
Disclosed is a lifting system with a three-way motion compensation function, including a main arm (1), a mobile cart I (5), a mobile cart II (2), a support II (3), a support I (4), a lifting mechanism (6), and a vessel body (7), where a front end of the main arm (1) is mounted at an upper end of the mobile cart I (5); a rear end of the main arm (1) is mounted at an upper end of the mobile cart II (2); a lower end of the mobile cart I (5) is mounted on the support I (4); a lower end of the mobile cart II (2) is mounted on the support II (3); the support I (3) and the support II (4) are separately fixed on the vessel body (7); rails I (11) are mounted on two sides of a bottom of the front end of the main arm (1); concave rails II (12) are mounted on two sides of the rear end of the main arm (1); the main arm (1) is driven to move front and back when the mobile cart I (5) and the mobile cart II (2) act synchronously; and the lifting mechanism (6) for driving a lifted object to move up and down is hinged to the front end of the main arm (1). The lifting system can perform a three-way motion compensation function, and can effectively avoid mechanical collision, position deviation, or the like caused by rolling, pitching, or heaving of the vessel body (7), thereby having high lifting efficiency, low comprehensive costs, and wide applicability.