Heave Motion Compensator Seal Rotation Dynamics
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Solution Overview
Problem
Current heave motion compensation systems in the offshore industry are unsatisfactory, leading to limitations in drilling operations, such as inability to use sophisticated tools due to inadequate compensation of heave motion, which restricts operational speed, weather windows, and handling capacity.
Innovation Solution
A heave motion compensator with a piston and cylinder assembly that includes a motor to cause the seal to revolve relative to the cylinder, maintaining dynamic friction and reducing stick-slip effects, thereby improving compensation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the seal is stationary relative to the cylinder during piston oscillation, then the structure is simple, but static friction causes stick-slip effects that reduce compensation precision
Solution Approach 1:
The seal is transformed from a stationary component to a dynamic rotating component. The seal rotates continuously or periodically while the piston oscillates, ensuring that the seal surface maintains dynamic friction with the cylinder wall. This dynamic motion prevents stick-slip effects and improves compensation precision, directly resolving the technical contradiction between precision and complexity.
Solution Approach 2:
The seal implements periodic rotation synchronized with or independent from the piston oscillation cycle. This periodic motion ensures continuous variation of the contact interface between the seal and cylinder, preventing static friction buildup and eliminating stick-slip phenomena, thereby achieving precise compensation without excessive structural complexity.
2Reliability
If a motor is added to rotate the seal relative to the cylinder, then friction is maintained in dynamic regime improving compensation behavior, but device complexity increases
Solution Approach 1:
The seal rotation mechanism introduces dynamic motion to maintain consistent dynamic friction conditions. This ensures reliable compensation behavior across varying operating conditions, as the dynamic friction regime is more predictable and controllable than static friction, directly addressing the reliability-complexity contradiction.
Solution Approach 2:
The invention replaces the reliance on pure mechanical friction-based damping with a controlled rotational mechanism. This substitution allows for more reliable and predictable compensation behavior by actively managing the friction regime through rotation, rather than passively relying on static friction characteristics.
3Speed
If the piston oscillates rapidly to compensate for high-frequency heave motions, then compensation speed improves, but friction losses and heat generation increase
Solution Approach 1:
The rotating seal maintains dynamic friction conditions that reduce energy loss compared to static friction. During rapid piston oscillation, the continuous rotation of the seal ensures that contact surfaces slide past each other smoothly rather than sticking and slipping, reducing frictional energy loss and heat generation while maintaining high compensation response speed.
Solution Approach 2:
The invention changes the friction regime parameter from static to dynamic through seal rotation. This parameter change reduces the coefficient of friction and stabilizes the friction force during rapid oscillation, thereby reducing energy losses and heat generation while maintaining the required compensation speed for high-frequency heave motions.
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 solution enhances the behavior and efficiency of heave compensation systems, allowing for more accurate and effective reduction of weight variation on the drill bit, especially in calm wave conditions, and can be applied to both passive and active compensators.
Implementation Method 1
said piston being provided with a seal frictionally engaging said cylinder
Implementation Method 2
said compensator further includes a motor that causes said seal to revolve relative to said cylinder
Data Source
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AI summary
A heave motion compensator (30, 40, 70, 100, 140, 300) for compensating heave motions comprises a cylinder (41) and a piston (44) delimiting a variable volume fluid chamber (49) in said cylinder (41), wherein said piston (44) can oscillate within said cylinder (41), said piston (44) being provided with a seal (48) frictionally engaging said cylinder. The compensator further includes a motor (65) that causes said seal (48) to revolve relative to said cylinder (41) so as to obtain a dynamic friction regime between the seal (48) and the cylinder (41). In a possible embodiment the motor (65) is arranged to rotate said piston (44), and the seal (48) is mounted on said piston (44) so as to rotate along with said piston (44).