Lined Pipeline Connector with Permeable Chokes
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Solution Overview
Problem
Plastics liners in pipelines face issues such as fluid permeation leading to liner collapse and difficulties in joining lengths of lined pipes due to heat damage during welding, especially in subsea operations where conventional connections are impractical.
Innovation Solution
A connector that bridges the pipe weld, engages with the liner, and includes permeable chokes to equalize pressure while isolating the inner pipe surface from corrosive fluids, allowing for welding without exposing the liner to excessive heat or corrosion, and accommodating liner creep and ovality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional butt welding is used to join steel pipe lengths, then the joining process is simple and efficient, but the heat of welding damages the plastics liner
Solution Approach 1:
The patent introduces a connector as an intermediary component that bridges two lined pipes. This connector includes a heat shield that physically separates the welding heat from the plastics liner, allowing the steel pipes to be welded without directly exposing the liner to harmful temperatures. The connector acts as a buffer zone that protects the sensitive liner material while enabling the welding process to proceed.
Solution Approach 2:
The patent divides the pipe joint into three distinct segments: the first lined pipe, the connector (which itself has a lined interior and an external heat shield), and the second lined pipe. This segmentation allows each component to serve its specific function - the liner provides corrosion protection, the steel provides structural strength, and the heat shield protects the liner during welding. The connector's dual structure (lined interior with external heat shield) exemplifies this segmentation principle.
2Object-affected harmful factors
If threaded or flanged connections are used to avoid heat damage to liners, then the liner is protected from thermal damage, but such connections are impractical for subsea operations
Solution Approach 1:
The connector serves as an intermediary that enables welding (a simple, efficient joining method) while protecting the liner from heat damage. This intermediary component makes the welding process compatible with lined pipes by introducing a protective element between the heat source and the liner, thereby resolving the conflict between joining efficiency and liner protection.
Solution Approach 2:
The heat shield is positioned locally at the weld zone rather than protecting the entire pipe length. This localized protection is sufficient because the harmful thermal effects are concentrated at the welding location. The shielded zone extends only as far as needed to protect the liner during the welding process, optimizing the balance between protection and ease of installation.
3Object-affected harmful factors
If the connector isolates the inner pipe surface completely from bore fluids, then corrosion protection is maximized, but pressure equalisation between micro-annulus and bore is prevented
Solution Approach 1:
The connector incorporates a porous choke that allows controlled fluid passage. This porous element enables pressure equalisation between the micro-annulus and the bore by allowing gas to pass through while maintaining a degree of isolation. The porous structure provides selective permeability - it allows gas molecules to pass through for pressure equalisation while still providing a barrier that reduces the rate of fluid interchange, thereby balancing corrosion protection with pressure equalisation requirements.
Solution Approach 2:
The connector provides different levels of isolation at different locations and for different substances. The porous choke allows gas passage for pressure equalisation while restricting liquid flow for corrosion protection. This spatial and functional differentiation within the connector enables it to simultaneously address both requirements - corrosion protection and pressure equalisation - by applying different properties to different parts of the same component.
4Reliability
If the micro-annulus pressure is allowed to equalise rapidly with bore pressure, then liner collapse is prevented, but excessive fluid interchange between bore and micro-annulus promotes corrosion
Solution Approach 1:
The porous choke provides controlled permeability that allows rapid enough pressure equalisation to prevent liner collapse while restricting excessive fluid interchange that would promote corrosion. The pore structure and size are designed to allow gas molecules to pass through quickly for pressure equalisation while creating sufficient resistance to liquid flow to minimize corrosion-promoting fluid exchange between the bore and micro-annulus.
Solution Approach 2:
The porous choke changes the flow parameters between gas and liquid phases. It allows gas to pass through with minimal resistance (enabling rapid pressure equalisation) while creating significant resistance to liquid flow (reducing corrosion). This parameter-based differentiation in flow characteristics enables the single component to address both the collapse prevention and corrosion protection requirements.
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 connector effectively prevents liner collapse, maintains a continuous corrosion-resistant surface, and facilitates easy installation and removal, ensuring reliable operation under varying pressure conditions and pipeline orientations.
Implementation Method 1
at least one circumferential permeable choke projecting radially from each male interface element to control fluid flow around the tube in use
Implementation Method 2
The connector of the invention also permits equalisation of pressure in the micro-annulus
Implementation Method 3
sufficiently isolating the inner wall surface of a steel pipe from bulk of the product carried by the pipeline to reduce corrosion of that surface
Data Source
AI summary
A connector for lined pipelines includes a tube having opposed male interface elements extending inwardly from respective ends of the tube. One or more circumferential permeable chokes project radially from each male interface element. The chokes minimize flow of oxidizing fluid from the bore into the micro-annulus between the liner and the pipe while maximizing flow of fluid from the micro-annulus into the bore in the event of catastrophic pressure drop in the bore. To maintain gaps between the tube ends and the pipe liners for fluid flow, shoulder formations extend circumferentially around the tube. The connector may be used in a joint arrangement where each liner includes a body, an end of lesser thickness and greater bore than the body that terminates short of an end of the pipe, an inner step between the body and the end, and an outer step between the end and the pipe.