Subsea Rigid-Flexible Pipe Connection via Catenary Undulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Temperature variations in hydrocarbon extraction cause longitudinal deformations in rigid submarine pipes, leading to movement and abrasion of flexible pipes on the seabed, and retraction forces can damage the rigid pipes, especially at great depths, making maintenance difficult.
Innovation Solution
A connection method that allows the flexible pipe to form a deformable undulation between the anchor point and the free connection end of the rigid pipe, enabling relative movement and deformation without stressing the rigid pipe, using anchoring means like anchor piles and flexible anchor lines, and optionally fitting bend limiters or buoys to prevent abrasion and kinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the rigid pipe is allowed to deform freely due to temperature variations, then the pipe can accommodate thermal expansion and contraction, but the flexible pipe on the seabed undergoes translation and abrasion which accelerates aging
Solution Approach 1:
The invention introduces an intermediary element (the suspended portion of the flexible pipe forming a catenary) between the rigid pipe and the anchored flow-line portion. This intermediary absorbs the thermal deformation movements through its catenary configuration, preventing direct translation and abrasion of the flow-line portion on the seabed, thus protecting the flexible pipe while allowing rigid pipe deformation
2Adaptability or versatility
If the rigid pipe retracts when hydrocarbon flow stops and cooling occurs, then thermal contraction is natural, but retraction forces oppose pulling forces from the flexible pipe which can damage the rigid pipe, especially at great depths
Solution Approach 1:
The invention provides beforehand cushioning by allowing the rigid pipe to move freely within the confines of the catenary configuration during installation. The catenary acts as a pre-configured buffer that absorbs retraction forces during thermal contraction, preventing these forces from being transmitted to the connection point and potentially damaging the rigid pipe structure
3Stability of the object's composition
If the flow-line portion is anchored at a fixed point, then the pipe position is stable, but the suspended portion exerts longitudinal pull on the rigid pipe which combines with retraction forces to increase damage risk
Solution Approach 1:
The invention resolves the force conflict by transitioning from a linear arrangement to a catenary configuration in another dimension. The anchored flow-line portion connects to the suspended portion via a catenary curve rather than a straight line, allowing the longitudinal pull to be converted into radial forces distributed along the catenary arc, thereby eliminating the direct longitudinal pull on the rigid pipe while maintaining anchor stability
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 method allows the rigid pipe to deform freely without damage, simplifies maintenance, and reduces economic costs by requiring only one connection point, while protecting the flexible pipe from abrasion and kinking, thus enabling reliable operation at great depths.
Implementation Method 1
the flow-line portion to form a deformable undulation between the anchor point and the free connection end so as to allow the relative movement of the free connection end relative to the anchor point and the deformation of the undulation
Implementation Method 2
by laying the suspended portion as a catenary substantially in line with the vicinity of the free connection end
Data Source
AI summary
A method and an installation for connecting a rigid submarine pipe and a flexible submarine pipe. The rigid pipe terminates in a free connection end. The flexible pipe has a flow-line portion and a suspended portion. The flow-line portion has an input end connected to the free connection end. The installation comprises an anchoring device to hold the flow-line portion anchored at an anchor point and to allow the flow-line portion to form an undulation. The anchoring device is suitable for holding the anchor point at a distance and close to the free connection end to form the undulation between the anchor point and the free connection end.