Composite Pipe End-Fitting Using Ridges and Collet Locking
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Solution Overview
Problem
The challenge lies in effectively terminating composite pipes, particularly those made of fibre-reinforced thermoplastic polymer, and connecting them reliably to non-composite, especially steel, piping and apparatus at subsea and surface interfaces, while ensuring a secure structural and sealing connection, and resisting axial and torsional forces.
Innovation Solution
A composite pipe termination design featuring a composite pipe with an annular portion having circumferentially extending ridges, a collet with grooves, an annular collar, and locking means, which together prevent axial movement and provide a secure connection through meshing ridges and grooves, along with sealing elements to enhance the seal and resist forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel end-fitting is attached to a composite pipe, then a reliable structural connection is achieved, but the seal reliability deteriorates due to different thermal expansion and structural properties
Solution Approach 1:
The patent introduces a composite collar as an intermediary component between the steel end-fitting and the composite pipe. This collar is made of the same composite material as the pipe, allowing it to expand and contract with the pipe during thermal cycles. The collar provides a compliant sealing surface that maintains seal reliability while the steel end-fitting provides structural strength.
Solution Approach 2:
The patent uses composite materials (fibre-reinforced thermoplastic polymer) for both the pipe and the collar. This ensures that the collar has matched thermal expansion properties to the pipe, preventing seal failure during thermal cycling while maintaining the structural integrity needed for high-pressure applications.
2Strength
If a composite pipe termination is designed to resist axial and torsional forces, then connection reliability is improved, but the diameter of the pipe termination increases
Solution Approach 1:
The patent divides the termination structure into distinct functional segments: the composite pipe, the composite collar for sealing, and the steel end-fitting for structural connection. This segmentation allows each component to be optimized for its specific function without requiring the entire termination to be oversized, maintaining a compact overall diameter while providing the necessary strength.
Solution Approach 2:
The patent addresses axial and torsional force resistance through the longitudinal arrangement and interlocking geometry of components rather than increasing radial diameter. The collar and end-fitting are designed with features that engage axially and resist torsion through their geometric configuration, allowing strength to be achieved without significantly increasing the pipe termination diameter.
3Reliability
If composite pipe terminations are designed for harsh subsea conditions, then environmental resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent selects specific material parameters (fibre-reinforced thermoplastic polymer with defined glass transition temperature and melting point) that provide the necessary environmental resistance. The composite collar is designed with a wall thickness parameter that ensures adequate sealing capability while maintaining manufacturability. These parameter selections balance performance requirements with manufacturing feasibility.
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 ensures a reliable, secure connection between composite and steel pipes, resisting axial and torsional forces, while maintaining a small diameter and effective sealing, suitable for harsh subsea conditions.
Implementation Method 1
the external surface comprises circumferentially extending ridges; a collet having an interior collet surface, wherein the collet encloses at least a part of the annular portion and wherein the interior collet surface comprises circumferentially extending grooves, and wherein circumferentially extending ridges on the external surface of the annular portion mesh with circumferentially extending grooves on the interior collet surface to provide axial movement blocking means which prevent or limit axial movement of the collet relative to the annular portion
Implementation Method 2
a liner, wherein the interior pipe surface is fused to the liner
Data Source
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AI summary
A composite pipe termination is provided comprising: a) a composite pipe having an interior pipe surface, an exterior pipe surface, a pipe end and a liner; b) a composite annular portion attached to the exterior pipe surface, the external surface of the annular portion comprising circumferentially extending ridges; c) a collet having an interior collet surface, wherein the collet encloses at least a part of the annular portion and wherein the interior collet surface comprises circumferentially extending grooves, and wherein circumferentially extending ridges on the external surface of the annular portion mesh with circumferentially extending grooves on the interior collet surface to provide axial movement blocking means; d) an annular collar which encloses and mates with the collet to prevent the collet from moving axially relative to the annular collar; e) an end-fitting locked to the annular collar.