Braided Reinforced Thermoplastic Pipe for Subsea Pressure and Buckling
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Solution Overview
Problem
Conventional spoolable reinforced thermoplastic pipes (RTP) are not suitable for dynamic offshore applications due to external pressure loads and may experience upheaval buckling in buried applications, requiring improved resistance to external hydrostatic pressure, cyclic bending, and axial stiffness to minimize longitudinal growth.
Innovation Solution
A reinforced thermoplastic pipe design featuring a polymeric barrier layer, braided or helically wound non-metallic reinforcement layers with specific lay angles to manage axial compression, and an optional metallic inner layer for enhanced collapse resistance, allowing for controlled elongation and resistance to external pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional RTP is used for offshore applications, then the pipe structure allows large deflections without bending stresses, but the pipe cannot withstand external hydrostatic pressure loads
Solution Approach 1:
The patent employs a composite structure consisting of a polymeric barrier layer, multiple non-metallic reinforcement layers (braided and helically wound), and a polymeric cover layer. This composite construction combines materials with different properties to simultaneously achieve flexibility for large deflections and sufficient strength to withstand external hydrostatic pressure loads in offshore applications.
2Stability of the object's composition
If high axial stiffness pipe is used for buried applications, then longitudinal growth is minimized, but upheaval buckling may occur due to internal pressure and thermal loads
Solution Approach 1:
The patent carefully selects and optimizes the lay angles of the reinforcement layers (braided layer at approximately 45 degrees, helically wound layers at specific angles) to control the pipe's axial stiffness. By adjusting these geometric parameters, the pipe achieves sufficient axial stiffness to minimize longitudinal growth while maintaining enough flexibility to accommodate thermal expansion and prevent upheaval buckling under internal pressure.
3Strength
If reinforcement layers with specific lay angles are used, then axial compression force is reduced, but manufacturing complexity increases
Solution Approach 1:
The reinforcement structure is divided into distinct segments: a polymeric barrier layer, at least one braided reinforcement layer, at least one helically wound reinforcement layer, and a polymeric cover layer. Each layer serves a specific function and can be manufactured independently using standard processes, reducing overall manufacturing complexity while achieving the desired axial compression resistance through the combined effect of properly oriented reinforcement layers.
Data Source
AI summary
A reinforced thermoplastic pipe having a polymeric barrier layer formed about a longitudinal axis; at least one first non-metallic reinforcement layer configured to carry an internal pressure load surrounding the polymeric barrier layer; at least one second non-metallic reinforcement layer configured to carry an axial load surrounding the at least one first reinforcement layer; and a polymeric cover layer surrounding the at least one second reinforcement layer. At least one of the first or second reinforcement layers is braided. In some embodiments, the lay angles of the first and second reinforcement layers are selected to reduce the axial compression force in the pipe in a constrained application. In another embodiment, an interior helical metallic layer around which the polymeric barrier layer is formed, the interior layer being an interlocked metallic carcass, a flat helically wound strip or a helically wound wire.