Self-adjusting Riser Centralizer for Offshore Drilling
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Solution Overview
Problem
Existing riser centralizing devices in offshore drilling systems fail to accommodate unpredictable motion caused by waves and wind, leading to premature wear and malfunction due to excessive loading, which can result in damage to risers, equipment, and platform structures.
Innovation Solution
A riser centralizing assembly with a frame assembly and circumferentially spaced rollers that are adjustable in the lateral direction and movable in response to angular movement, allowing the rollers to maintain contact with the riser and limit lateral movement while accommodating tilt, thus reducing stress and extending the lifespan of the centralizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed-position rollers are used to constrain lateral riser movement, then riser alignment is improved, but the centralizing devices experience premature wear and malfunction due to excessive loading from unpredictable wave and wind motion
Solution Approach 1:
The patent applies the dynamics principle by making the roller assembly movable along the longitudinal axis of the frame assembly. The roller assembly is mounted on a sliding mechanism that allows it to move freely in the longitudinal direction, enabling the rollers to maintain continuous contact with the riser surface while accommodating longitudinal motion caused by wave and wind forces. This dynamic adjustment prevents excessive loading on the centralizer components while maintaining effective lateral constraint and riser alignment.
2Adaptability or versatility
If the roller assembly is made movable in the longitudinal direction, then adaptability to wave and wind motion is improved, but the mechanism complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the centralizer into distinct functional modules: a frame assembly for structural support, a movable roller assembly for lateral constraint, and a sliding mechanism for longitudinal adjustment. This modular segmentation allows each component to perform its specific function independently, simplifying the overall design while achieving the desired adaptability. The roller assembly can be manufactured and maintained as a separate unit, reducing system complexity.
Solution Approach 2:
The patent applies parameter changes by allowing the position of the roller assembly to vary dynamically along the longitudinal axis in response to environmental conditions. The sliding mechanism enables the roller assembly to adjust its longitudinal position automatically, changing the geometric parameters of the system to accommodate wave and wind-induced motion. This passive parameter adjustment achieves adaptability without requiring complex active control systems.
3Manufacturing precision
If the rollers maintain continuous contact with the riser, then lateral movement limitation is improved, but stress concentration occurs during angular movement and tilting
Solution Approach 1:
The patent applies dynamics by enabling the roller assembly to move longitudinally in response to angular movement and tilting of the riser. When the riser experiences angular displacement or tilting due to wave motion, the roller assembly automatically shifts position along the longitudinal axis to maintain optimal contact. This dynamic repositioning distributes the contact stress over a larger area and prevents stress concentration at fixed contact points, thereby protecting both the riser and centralizer from damage.
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 solution effectively maintains riser alignment and reduces stress on both the riser and the platform, preventing damage and prolonging the operational life of the centralizers by accommodating natural motion and maintaining contact with the riser during tilting and lateral shifts.
Implementation Method 1
The roller assembly includes a roller that is rotatable on an axle mounted to the housing such that the roller extends from a radially inner portion of the housing to bear on an exterior surface of the riser to limit lateral movement of the riser with respect to the frame assembly
Data Source
AI summary
A riser tensioner assembly for supporting risers on an offshore drilling platform includes a frame assembly and a plurality of riser centralizers circumferentially spaced about the frame assembly. The riser centralizers each include a clevis supporting roller for bearing on a riser to limit lateral movement of the riser with respect to the frame assembly. The clevis includes an elongated channel along which the roller is movable to accommodate angular movement of the riser with respect to the frame assembly.