Inverted Riser Tensioner Using Pressure Differential Retraction
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Solution Overview
Problem
Offshore riser tensioners face challenges in maintaining consistent tension and compensating for vessel motion induced by waves, leading to potential buckling or failure of risers, and existing systems lack efficient mechanisms for retracting and re-tensioning risers effectively.
Innovation Solution
A riser tensioner assembly with a telescoping rod and piston system, utilizing a pressure differential between a high-pressure annulus and a low-pressure chamber, where the high-pressure fluid in the annulus urges the piston downward, retracting the tensioner and applying upward force on the riser, while a high-pressure lubricant conduit supplies liquid lubricant to maintain seal integrity and an internal accumulator maintains pressure differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional riser tensioner system is used, then the riser can be tensioned to prevent buckling, but the system lacks efficient mechanisms for retracting and re-tensioning risers, leading to operational inefficiency
Solution Approach 1:
The patent inverts the conventional tensioner design by making the rod the stationary component connected to the riser, while the cylinder barrel becomes the moving component that telescopes in and out. This inversion allows the high-pressure fluid to directly push the cylinder barrel, creating efficient retraction motion without complex intermediate mechanisms, thereby improving productivity while managing device complexity
Solution Approach 2:
The patent employs hydraulic principles by using high-pressure fluid injected into the sealed annulus between the rod and cylinder barrel to generate the forces needed for retraction and tensioning. The fluid pressure differential creates the driving force that moves the cylinder barrel relative to the rod, providing an efficient and controllable mechanism for riser tensioner operation
2Force
If high pressure fluid is used in the annulus to retract the tensioner, then upward force is applied to the riser, but seal integrity may be compromised under high pressure conditions
Solution Approach 1:
The patent introduces lubricant as an intermediary substance between the high-pressure fluid and the seal surfaces. The lubricant reduces direct contact and friction between sealing surfaces, allowing the high-pressure fluid to generate the necessary upward force while protecting the seal from damage and maintaining seal integrity under high-pressure conditions
Solution Approach 2:
The patent manages pressure parameters by creating a controlled pressure differential between the annulus and the lubricant supply system. By carefully controlling the pressure of the lubricant relative to the high-pressure fluid, the system maintains seal integrity while still generating the required upward force on the riser through the pressure differential
3Ease of operation
If a telescoping rod and piston system is used, then retraction and extension are achieved, but the device complexity increases
Solution Approach 1:
The patent designs the rod-cylinder barrel assembly to serve multiple functions simultaneously: the telescoping mechanism provides retraction and extension capability, while the sealed annulus between them serves as the high-pressure fluid chamber. The rod both transmits the upward force to the riser and defines the boundary of the pressure chamber, eliminating the need for separate components and reducing overall device complexity
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 maintains consistent tension, compensates for vessel motion, and ensures reliable retraction and extension of the riser, enhancing the durability and operational efficiency of offshore riser systems by utilizing a pressure differential and internal lubrication to maintain seal integrity.
Implementation Method 1
a pressure differential between a high-pressure annulus and a low-pressure chamber, where the high-pressure fluid in the annulus urges the piston downward
Implementation Method 2
a high-pressure lubricant conduit supplies liquid lubricant to maintain seal integrity
Data Source
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AI summary
Embodiments of the present disclosure include a riser tensioner includes a cylinder barrel, a rod reciprocally carried within the cylinder barrel and having an external end sealingly extending out of a proximal end of the cylinder barrel, and a piston on an interior end of the rod that slides and seals against an inner surface of the cylinder barrel. The tensioner further includes a selectively sealed low pressure chamber in the cylinder barrel between the piston and a distal end of the cylinder barrel and fillable with a low pressure fluid, and a selectively sealed annulus between the rod and the cylinder barrel, the annulus extending between the piston and the proximal end of the cylinder barrel and fillable with an annulus fluid at a pressure higher than the low pressure fluid, thereby urging the piston and rod towards retraction.