Direct Acting Single Sheave Heave Compensator
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Solution Overview
Problem
Heave compensation systems often cause line damage or failure due to fatigue from continuous bending over elements, particularly in lighter-weight fiber lines, as they operate in offshore lifting and landing operations.
Innovation Solution
A direct acting heave compensation system with a traction winch, support base, and a movably mounted compensator sheave that maintains a constant line length between the winch and sheave, reducing stress and flexing by guiding the line along a curved rail that matches the arc-like path of the line's motion, minimizing sheave rotation and line travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the line moves over or flexes at sheaves in the compensation system during operation, then the heave compensation system can control load position and tension, but the line may be damaged or fail due to fatigue from continuous bending
Solution Approach 1:
The sheave is made movable rather than fixed, allowing it to dynamically adjust its position to follow the arc-like path of the line. This dynamic configuration reduces line flexing and bending fatigue while maintaining operational capability during heave compensation
Solution Approach 2:
The sheave mounting frame follows a curved arc-like path that matches the natural geometry of the line's motion during heave compensation. This curved trajectory minimizes sharp bends and reduces fatigue stress on the line compared to linear or fixed sheave configurations
2Adaptability or versatility
If a winch-based system with multiple sheaves is used for heave compensation, then both passive and active mode control is achieved, but the line experiences increased fatigue from continuous back-and-forth travel and flexing
Solution Approach 1:
The sheave mounting frame is designed to move dynamically along a curved path rather than remaining stationary. This dynamic movement accommodates both passive and active heave compensation modes while significantly reducing the cumulative flexing and bending cycles that cause line fatigue and reduce service life
Solution Approach 2:
The movable sheave mounting frame acts as an intermediary element between the fixed winch and the suspended load. It mediates the line's motion by following its natural arc-like path, reducing direct stress and fatigue on the line while enabling versatile compensation modes
3Device complexity
If the sheave is fixed in position, then the system structure is simpler, but the line must continuously flex and travel over the sheave during heave compensation, causing fatigue damage
Solution Approach 1:
The sheave is transformed from a fixed component to a movable one that travels along a curved guide path. This dynamic configuration adds some structural complexity but dramatically improves line durability by eliminating continuous flexing and bending over a fixed sheave edge
Data Source
Figure 1
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Figure 3a~3d
AI summary
A heave compensation system provides a direct acting heave compensator that reduces stress and fatigue on a line, the system includes a single sheave system that compensates for heave as it carries a load line and moves along a curve profile of the heave compensator tangent to the point the load line comes off of a line handling system. The length of the line extending from the line handling system to the sheave remains substantially the same length during heave compensation operations, and the point where the line takes off from the line handling system is substantially the only point of changing stress on the line.