Compensated Elevator Link for Heave Motion Control
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Solution Overview
Problem
Existing compensation systems for floating drilling rigs are either complex, costly, or require significant intervention to activate and reset, posing safety risks and efficiency issues when the primary heave compensation system fails during 'locked to bottom' operations.
Innovation Solution
A compensated elevator link with hydraulic cylinders and a compressible fluid system that automatically adjusts to extend and retract in response to tensional forces, providing passive compensation without the need for complex valve systems or significant intervention, using a combination of non-compressible and compressible fluids to manage heave motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive compensation systems utilise hydraulic cylinders with pneumatic accumulators, then heave compensation is provided, but the accumulators are large in size and require static location mounting with pneumatic connections
Solution Approach 1:
The pneumatic accumulator is nested within the hydraulic cylinder assembly, with the accumulator positioned inside the cylinder housing. This integration allows the compensation system to maintain heave compensation functionality while significantly reducing the overall volume and eliminating the need for separate static mounting locations and pneumatic connections.
Solution Approach 2:
The patent combines the hydraulic cylinder and pneumatic accumulator into a single integrated compensated elevator link assembly. The hydraulic piston and pneumatic accumulator work together within the same housing, merging two previously separate systems into one compact unit that provides both hydraulic actuation and pneumatic spring force.
2Stability of the object's composition
If active heave compensation systems are used, then lower load variations are maintained, but the systems are more complex than passive compensators
Solution Approach 1:
The compensated elevator link is designed as a passive self-regulating system where the pneumatic accumulator automatically provides spring force in response to tension changes without requiring external control systems. The hydraulic piston responds automatically to load variations, extending or retracting the link to maintain stability without electronic controls or active intervention.
Solution Approach 2:
The system uses a combination of hydraulic fluid in the cylinder and pneumatic gas in the accumulator to create a passive compensation mechanism. The incompressible hydraulic fluid transmits force while the compressible pneumatic gas provides spring force, creating a self-regulating system that maintains load stability without electronic controls.
3Ease of manufacture
If a telescopic elevator link with shear pin is used, then the system is easily installed into the derrick, but all tension in the drill string is lost once activated and the shear pin cannot be reset without rigging down
Solution Approach 1:
The compensated elevator link is designed to be retained and reused after activation. Unlike the shear pin that must be discarded and requires rigging down to replace, this link maintains its structural integrity and can be reset by simply reversing the extension mechanism, allowing quick recovery without equipment removal or complex rigging operations.
Solution Approach 2:
The link uses a dynamic extension mechanism with hydraulic pistons that can both extend and retract. This bidirectional movement capability allows the system to activate by extending under load and then reset by retracting, providing a reusable solution rather than a single-use shear pin that requires complete equipment replacement.
4Force
If large pneumatic accumulators are mounted in static locations, then compensation force is provided, but pneumatic connections are required between the accumulator bank and hydraulic cylinders
Solution Approach 1:
The pneumatic accumulator and hydraulic cylinder are merged into a single integrated assembly where the accumulator is positioned inside the cylinder housing. This eliminates the need for external pneumatic connections between separate accumulator banks and hydraulic cylinders, as the pneumatic spring force is generated in-situ within the same housing that contains the hydraulic piston.
Solution Approach 2:
The accumulator is nested within the hydraulic cylinder assembly, with the pneumatic chamber positioned inside the hydraulic cylinder housing. This nesting arrangement eliminates external pneumatic tubing and connections, creating a self-contained unit where the compensation force is generated internally without requiring complex external pneumatic infrastructure.
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
The system effectively compensates for heave motion, maintaining stability and safety by automatically adjusting to prevent excessive forces on the workstring, reducing the risk of equipment damage and personnel safety hazards, while being simpler and less costly to install and operate compared to existing solutions.
Implementation Method 1
the piston rod having an internal chamber for accommodating a compressible second working fluid
Implementation Method 2
first and second actuable means configured operable with a piston rod by way of respective first working fluids
Data Source
AI summary
A compensated elevator link is disclosed. In at least one aspect, the compensated elevator link comprises a plurality of cylinder housings and a rod having a plurality of ends, each end comprising a piston head adapted to be slideably received within one of the cylinder housings for defining first and second hydraulic cylinders. Each hydraulic cylinder has at least one annulus for receiving a non-compressible fluid. The rod comprises a passage for receiving a compressible fluid, wherein each piston head comprises at least one passage to allow selective displacement of the non-compressible fluid between the annulus of the cylinder housing and the passage within the rod during selective displacement of the hydraulic cylinders between a contracted condition to an extended condition for either compression or expansion of the compressible fluid by the non-compressible fluid.