Flexible Pipe Body with Helical Metal Barrier for Permeation Control
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Solution Overview
Problem
Flexible pipes used for transporting production fluids face issues with fluid permeation through the layers, leading to corrosive environments and mechanical failures due to fluid accumulation in the pipe annulus, and have limitations on bending radius that can cause damage to the barrier layer.
Innovation Solution
A flexible pipe body design featuring a continuous metallic permeation-barrier layer helically wound between the internal pressure sheath and the armour layer, with a connection portion joining laterally adjacent tape wraps, and optionally sandwiched between sacrificial layers to prevent fluid permeation and maintain flexibility without damaging the barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer sheath or pressure sheath is used as the fluid-retaining layer, then the pipe can retain fluid pressure, but fluids such as carbon dioxide and hydrogen sulphide can permeate through the layer leading to corrosive environments and mechanical failure
Solution Approach 1:
The patent employs a composite structure combining a polymer pressure sheath with a metallic barrier layer (stainless steel or corrosion-resistant alloy) wound helically around it. This composite construction maintains the pressure-containing capability of the polymer while adding impermeability and corrosion resistance through the metallic layer, preventing fluid permeation and subsequent corrosion of armour layers.
2Adaptability or versatility
If the pipe is designed to allow large deflections for flexibility, then the pipe can adapt to sub-sea installations, but the minimum bending radius is limited and bending stresses can impair functionality
Solution Approach 1:
The patent utilizes a flexible polymer pressure sheath as the innermost layer that can accommodate large deflections and bending without rigid structural support. This flexible shell design allows the pipe to adapt to sub-sea installations with varying routing requirements while maintaining structural integrity through the layered construction, with the metallic barrier layer and armour layers providing strength without compromising flexibility.
3Object-affected harmful factors
If a metallic barrier layer is used to prevent fluid permeation, then corrosion is reduced, but the pipe flexibility and bending capability are compromised
Solution Approach 1:
The patent applies the metallic barrier layer in the form of a helically wound tape or strip around the polymer pressure sheath, creating localized corrosion protection where it is most needed (at the outer surface exposed to annulus fluids) while maintaining the overall flexibility of the pipe through the continuous helical winding and the inherent flexibility of the thin metallic layer. The armour layers provide additional mechanical flexibility support.
Data Source
AI summary
A flexible pipe body for transporting production fluids, a flexible riser, and a method of manufacturing a flexible pipe body are disclosed. The flexible pipe body comprises: an internal pressure sheath; a helically wound armour layer radially outward of the internal pressure sheath; and a continuous metallic permeation-barrier layer disposed radially inward of the helically wound armour layer; wherein the continuous metallic permeation-barrier layer comprises a helically wound tape and a connection portion configured to join laterally adjacent tape wraps of the helically wound tape.