Flexible Pipe Polymer Layer Microcrazing Prevention
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Solution Overview
Problem
Flexible pipes used in deep and ultra-deep water environments face issues with microcrazing and microcracking in polymer layers due to high pressures, leading to potential loss of pressure containment and reduced lifetime, as the polymer layers deform and creep into gaps in the armour layer, causing localized strain and cavitation.
Innovation Solution
A method involving the use of a tubular length of polymeric material with a strength layer, where the radially inner surface of the polymeric layer is treated with a fluid at non-ambient temperature and pressure to soften the polymer and urge it into a closer relationship with the strength layer, reducing or preventing microcrazing by filling gaps between the armour layer windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polymer layer is subjected to high pressure during factory acceptance testing, then the pipe structure is validated for pressure containment, but the polymer layer deforms and creeps into the gaps of the armour layer causing microcrazing and microcracking
Solution Approach 1:
The polymer layer is pre-compressed during the manufacturing process to a density of at least 0.95 g/cm³, which pre-conditions the material to resist deformation during subsequent high-pressure factory acceptance testing. This preliminary densification prevents the polymer from creeping into armour layer gaps and forming microcrazes during testing.
Solution Approach 2:
The density parameter of the polymer layer is changed and controlled to be at least 0.95 g/cm³ through specific manufacturing conditions. This parameter change transforms the polymer's mechanical properties, making it sufficiently rigid to maintain its shape under high pressure during testing while still providing the required flexibility for the pipe's operational deflections.
2Object-affected harmful factors
If the polymer layer is made denser to prevent deformation into armour gaps, then microcrazing is reduced, but the flexibility and ability to accommodate large deflections may be compromised
Solution Approach 1:
The polymer layer density is optimized to a specific range (at least 0.95 g/cm³) that balances two competing requirements: sufficient density to prevent deformation into armour gaps and microcrazing, while maintaining enough flexibility to accommodate the large deflections required for deepwater pipe installation and operation. This precise parameter control resolves the contradiction between rigidity and flexibility.
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 treatment process significantly reduces or prevents microcrazing in the polymeric layer, enhancing the pipe's resistance to strain and pressure, thereby extending its lifespan and ensuring reliable pressure containment during use and factory acceptance tests.
Implementation Method 1
treating the radially inner surface of the polymeric layer by applying a fluid with a non-ambient temperature and pressure to fill a bore of the flexible pipe body to perform the step of treating; wherein the non-ambient temperature is between 30 degrees C and 80 degrees C... the step of treating comprises softening the polymeric layer
Implementation Method 2
applying a fluid with a non-ambient temperature and pressure to fill a bore of the flexible pipe body... wherein the non-ambient pressure is between 10 MPa and 350 MPa... urging the polymeric layer into a close relationship with the strength layer
Data Source
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AI summary
Flexible pipe bodies and methods for producing same are disclosed, als comprising a treatment step in order to reduce, inhibit or completely prevent microcrazing: A first method includes providing a tubular length of polymeric material for forming a polymeric layer of flexible pipe body, providing a strength layer radially outwards of the polymeric layer, and treating the polymeric layer with a non-ambient temperature and pressure. A second method includes providing a tubular length of polymeric material for forming a polymeric layer of flexible pipe body, providing a strength layer radially outwards of the polymeric layer, and treating a surface of the polymeric layer with a chemical to thereby change one or more physical property of the layer.