Synthetic Rope Motion Compensation Without Sheave Heat Damage
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Solution Overview
Problem
Existing motion compensation methods for deep water lifting and lowering operations using synthetic ropes generate excessive sliding friction and heat, which can damage the ropes, especially when heavy loads are handled at great depths, reducing the lifting capacity and increasing the risk of equipment damage.
Innovation Solution
The method employs a system with steel cable grippers to support the synthetic rope over sheaves, minimizing sliding friction by using smooth surfaces and double wedging for failsafe gripping, allowing the synthetic rope to be used effectively without generating internal heat, and maintaining load capacity with depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If synthetic rope is used for deep water lifting and lowering operations, then the load capacity is improved and the rope weight is reduced, but sliding friction generates excessive heat that can damage the rope
Solution Approach 1:
A steel cable is introduced as an intermediary element between the synthetic rope and the sheave. The steel cable grips the synthetic rope and transmits the lifting force, while the steel cable itself contacts the sheave. This mediator prevents direct contact between the synthetic rope and sheave, eliminating the sliding friction that generates harmful heat on the rope while still enabling effective force transmission.
2Adaptability or versatility
If conventional winching methods are used with synthetic rope, then deep sea lifting capability is enabled, but the sliding friction on sheaves generates heat that can melt the rope
Solution Approach 1:
The steel cable acts as a protective intermediary that carries the mechanical interaction with the sheave, shielding the synthetic rope from direct contact and the resulting thermal damage. This allows the system to maintain deep sea lifting capability while protecting the rope from heat-generated damage.
Solution Approach 2:
The system replaces the direct mechanical contact between synthetic rope and sheave with a steel cable-mediated contact system. The steel cable is better suited for withstanding the sliding friction and heat generation, while the synthetic rope remains protected, effectively substituting the mechanical interaction pathway.
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
This approach enables safe and efficient deep sea lifting and lowering operations by reducing heat generation and maintaining the synthetic rope's strength, expanding deep sea capabilities while preventing damage to the rope and equipment.
Implementation Method 1
The capability to lower subsea packages to the seafloor with a synthetic rope under motion compensation control would allow substantially expanded deep sea lifting and lowering capabilities as contemporary winching methods for synthetic rope has the potential for damaging the critical synthetic rope during motion compensation operations.
Implementation Method 2
double wedging for failsafe gripping
Data Source
AI summary
A method of providing motion compensation of a subsea package with a synthetic rope comprising attaching the synthetic rope to the subsea package, supporting a first gripper with a wire rope from a winch capable of motion compensation control characteristics and gripping the synthetic rope with the first gripper, supporting a second gripper with a second wire rope, and repeating the following sequence: lowering the first gripper, the synthetic rope, and the subsea package a first distance, gripping the synthetic rope with the second gripper, releasing the first gripper from the synthetic rope, raising the first gripper the first distance, gripping the synthetic rope with the first gripper, releasing the second gripper from the synthetic rope, such that when the subsea package is lowered proximate the subsea landing location the winch capable of operating with motion compensation characteristics can operate to compensate for the vessel motion and smoothly lower the subsea package to the subsea landing location.