Subsea Pipe Reel-Lay Straightening for RC Section Orientation
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Solution Overview
Problem
Existing methods for laying subsea pipes using a pipe reel laying vessel face challenges in controlling the orientation of Residual Curvature (RC) sections, leading to improper installation and reduced effectiveness of controlled lateral buckling, particularly in deep water applications.
Innovation Solution
A method for laying subsea pipes that involves configuring a straightener system to produce both straight and non-straight portions of pipe, including under-straightened and over-straightened sub-portions, to ensure the RC sections are installed horizontally on the seabed, thereby controlling their rotation in the catenary span.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the straightener system is configured to produce RC sections with conventional under-straightening only, then the pipe can be installed on the seabed, but the RC sections rotate improperly in deep water leading to incorrect orientation and reduced effectiveness of controlled lateral buckling
Solution Approach 1:
The RC section is divided into multiple sub-portions with different curvature characteristics (under-straightened and over-straightened portions). This segmentation allows different parts of the RC section to serve different functions: the under-straightened portions provide the necessary flexibility for buckling while the over-straightened portions act as stabilizing elements that control rotation and ensure proper horizontal orientation on the seabed.
Solution Approach 2:
Different portions of the RC section are given different local qualities through varying the degree of straightening. The under-straightened sub-portions have higher curvature and flexibility to facilitate buckling, while the over-straightened sub-portions have lower curvature and greater stiffness to control rotation. This local differentiation of properties enables the RC section to simultaneously achieve both buckling functionality and orientation control.
2Ease of operation
If the pipe is laid using conventional straightening methods, then the installation process is simple, but the RC sections do not maintain proper horizontal orientation on the seabed in deep water conditions
Solution Approach 1:
The desired horizontal orientation is achieved through preliminary action during the straightening process itself. By configuring the straightener system to create alternating under-straightened and over-straightened sub-portions, the RC section is pre-conditioned with specific curvature characteristics that naturally guide it to assume the correct horizontal orientation when installed on the seabed, eliminating the need for post-installation orientation adjustments.
3Adaptability or versatility
If conventional under-straightening is used to create RC sections, then the pipe can accommodate thermal expansion, but the RC sections experience excessive rotation in the catenary span leading to improper installation
Solution Approach 1:
The curvature parameter of the RC section is changed by applying both under-straightening and over-straightening in alternating sub-portions. This parameter modification creates a balanced curvature distribution where the under-straightened portions provide the necessary adaptability for thermal expansion while the over-straightened portions provide rotational stability, preventing excessive rotation in the catenary span during installation.
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 approach enhances the controlled lateral buckling mechanism, improving the thermal expansion control and reducing the risk of pipeline failure by ensuring the RC sections are correctly oriented on the seabed, even in deep water conditions.
Implementation Method 1
The pipe passes through the straightener system, which generally comprises rollers, after being unspooled from a reel of the vessel. This reverses the plastic deformation that was imparted to the pipe upon spooling.
Implementation Method 2
Transfer of such high temperature fluids can cause thermal gradients across the pipeline, especially during multiple production shut down and start up cycles. Repeated expansion, contraction and thermal cycling of the pipeline can lead to pipeline buckling, movement and loading
Data Source
AI summary
The invention relates to a method for laying a subsea pipe. In particular, the invention relates to a method for laying a subsea pipe by means of a pipe reel laying vessel. The method is for laying a pipe (3) in a subsea location, the method comprising:a) configuring a straightener system (25) to straighten a pipe, and unwinding the pipe (3) from the reel to provide a straight portion (19) of pipe having a predetermined length (LS) greater than 300 m;b) configuring the straightener system (25) to provide a non-straight portion of pipe (24) having a predetermined length (LE);wherein the non-straight portion of pipe (24) produced during step b) comprises at least one under-straightened sub-portion of pipe (21) and at least one over-straightened sub-portion of pipe (22, 23).