Unbonded Flexible Pipe Optical Fiber Monitoring Layer
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Solution Overview
Problem
Existing unbonded flexible pipes for offshore and subsea fluid transportation lack effective monitoring solutions for mechanical, thermal, and chemical impacts, leading to premature retirement despite potential for extended use, as current sensor arrangements are not adequately protected against mechanical damage and do not provide high-resolution monitoring along the pipe length.
Innovation Solution
Incorporating an optical fiber layer with a length of at least three times the pipe length, arranged in a tape configuration that provides overlength protection, allowing for high-resolution monitoring without weakening the armor layers, and ensuring the optical fiber is safely protected against mechanical damage in dynamic applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensor arrangements are mounted in grooves of metallic armor elements using epoxy material, then the optical fiber can be fixed in the pipe, but the sensor arrangement is vulnerable to mechanical damage and does not provide high-resolution monitoring along the pipe length
Solution Approach 1:
The patent transitions from discrete point sensors mounted on armor elements to a continuous distributed optical fiber sensor system that runs longitudinally through the pipe structure. This dimensional change from 0D point sensors to 1D continuous sensing enables high-resolution monitoring along the entire pipe length while the fiber is protected within the layered structure.
Solution Approach 2:
The optical fiber is nested within the multi-layered pipe structure, specifically positioned between the inner sealing sheath and the pressure armor layer. This nesting provides mechanical protection to the fragile optical fiber while allowing it to span the entire length of the pipe for continuous monitoring.
2Measurement precision
If the optical fiber is arranged with a length of at least three times the pipe length, then high-resolution monitoring is enabled, but the fiber becomes more susceptible to mechanical damage in dynamic applications
Solution Approach 1:
The optical fiber is positioned within the protected space between the inner sealing sheath and pressure armor layer, creating a cushioning effect that absorbs mechanical stresses. The surrounding structural layers act as protective barriers that cushion the fiber from direct mechanical damage during dynamic operations.
Solution Approach 2:
The optical fiber is surrounded by flexible polymer layers including the inner sealing sheath and anti-friction layers that can deform and accommodate the fiber's length. These flexible encapsulating layers protect the fiber from mechanical damage while allowing the extended length necessary for high-resolution monitoring.
3Loss of information
If discrete sensors are mounted on armor layers, then monitoring capability is provided, but the armor layers are weakened and the pipe flexibility is reduced
Solution Approach 1:
The patent replaces discrete mechanical sensor mounting systems that require grooves and epoxy adhesives (which weaken the armor) with an integrated optical fiber system. The optical fiber senses mechanical, thermal, and chemical parameters without requiring physical attachment to the armor layers, thus preserving armor integrity and pipe flexibility.
Solution Approach 2:
The optical fiber serves multiple functions simultaneously: it provides continuous monitoring of mechanical strain, temperature, and chemical conditions along the entire pipe length, while also acting as a protective element within the layered structure. This multi-functionality eliminates the need for separate sensor mounting hardware that would compromise armor strength.
Data Source
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AI summary
A unbonded flexible pipe with a length and a longitudinal axis is described. The pipe comprises an innermost sealing sheath defining a bore, at least one armor layer surrounding the inner sealing sheath and at least one optical fiber containing layer, wherein the optical fiber containing layer comprises at least one tape and at least one optical fiber arranged with a length of at least about 3 times the length of the flexible pipe.In an embodiment the optical fiber is incorporated into the at least one tape of said optical fiber containing layer to provide an integrated fiber tape where advantageously the optical fiber is arranged with S-shaped folds.