Dynamic Support Surface for Vessel Lifting Re-Hit Prevention
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Solution Overview
Problem
Existing methods for lifting objects from a floating vessel are prone to re-hits due to vessel movements, especially in rough seas, and lack flexibility for larger objects, with complex compensation systems being unreliable and potentially hazardous.
Innovation Solution
A device that dynamically adjusts the lifting speed by retracting the support surface towards the deck once the object is lifted, using a detector to determine the instant of weight transfer and an actuator system to lower the support surface at a significant percentage of the lifting speed, thereby reducing the risk of re-hits without requiring continuous active compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed crane on a floating vessel is used to lift objects, then the lifting operation can be performed, but the vessel movements cause the object to re-hit with parts of the vessel, creating damage risk
Solution Approach 1:
The support surface is lowered in advance before the lifting operation completes, creating a safety margin that prevents re-hit before it can occur. This preliminary protective action eliminates the harmful effect of vessel movements causing object collision during the lifting process
Solution Approach 2:
The support surface acts as an intermediary between the vessel and the lifted object. By dynamically adjusting the support surface position relative to the vessel deck, it mediates the harmful vessel movements and prevents them from transferring to the lifted object, thereby eliminating re-hit damage risk
2Object-affected harmful factors
If an active compensation system is used to prevent re-hit, then the object can be held stationary relative to the crane, but the system is complex and potentially unreliable
Solution Approach 1:
The invention extracts and eliminates the need for complex active compensation systems by using a passive geometric approach. Instead of continuously compensating for vessel movements through complex control systems, the solution removes the re-hit hazard by lowering the support surface, thereby simplifying the overall system while maintaining safety
Solution Approach 2:
The invention replaces expensive, complex, and potentially unreliable active compensation systems with a simple, fail-safe geometric solution. The support surface lowering mechanism is inherently safe without requiring continuous active control, reducing system complexity and improving reliability
3Productivity
If the support surface remains at the first height during lifting, then the object can be lifted from the deck, but the vessel movements may cause the object to collide with the vessel parts
Solution Approach 1:
The support surface is lowered in advance during the lifting operation, creating a safety margin that prevents collision before it can occur. This preliminary protective action allows the lifting to proceed at normal speed while eliminating the harmful collision risk
Solution Approach 2:
The support surface position is dynamically adjusted during the lifting operation. By making the support surface movable and adjusting its position in response to lifting progress and vessel movements, the system maintains both high productivity and safety by preventing collisions
Data Source
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AI summary
Described is a device for lifting an object from a deck of a vessel subject to movements in a heave direction. The device comprises a support surface (6a) for the object provided at a first height (11) in the heave direction relative to the deck. A lifting crane (5) is configured to take up the object from the support surface (6a) at a lifting point thereof at a lifting speed. An actuator system (16) is configured to lower the support surface (6a) relative to the deck at the instant in time at which the object is lifted from the surface to a second height in the heave direction at a lowering speed. A method using the device is also described.