Polypropylene Sealing Sheath for High-Temperature Underwater Pipes
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Solution Overview
Problem
Existing underwater pipes for hydrocarbon transport in deep water face challenges with materials that are either too expensive or prone to swelling, blistering, and chemical aging when exposed to high temperatures and pressures, particularly with hydrocarbons containing hydrogen sulfide, carbon dioxide, and methane.
Innovation Solution
A polypropylene-based inner polymeric sealing sheath with specific density and melt index characteristics, such as homopolymeric polypropylene with a density greater than 0.900 g/cm3 and a melt index less than 10 g/10 minutes at 230°C, is used, which provides resistance to swelling and blistering, and is compatible with high-temperature hydrocarbons, reducing the risk of chemical aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyethylene is used for the inner polymeric sealing sheath, then the material is cost-effective and provides good ductility, but it exhibits high swelling tendency and poor resistance to high temperatures and pressures
Solution Approach 1:
The patent changes the chemical composition parameter by selecting polypropylene homopolymer with specific density (0.90-0.92 g/cm³) and melt flow index (0.1-10 g/10min) parameters, which fundamentally alters the material's interaction with hydrocarbons to reduce swelling while maintaining cost-effectiveness
Solution Approach 2:
The patent creates a composite structure by combining polypropylene homopolymer with specific additives including antioxidants (such as Irganox 1076), UV stabilizers (such as Tinuvin 292), and processing aids, forming a composite material that enhances chemical resistance and durability while maintaining the base polymer's cost advantages
2Reliability
If polyamide is used for the inner polymeric sealing sheath, then the material provides good blistering resistance and low swelling tendency, but it is prone to hydrolysis and chemical aging in the presence of water and acids
Solution Approach 1:
The patent converts the potential harm of polypropylene's susceptibility to oxidation by incorporating antioxidant additives (such as Irganox 1076 at 0.1-5.0 phr), transforming the vulnerability into a protected state where the material gains enhanced oxidative stability while maintaining its inherent resistance to hydrolysis
Solution Approach 2:
The patent creates a chemically inert environment within the polymer matrix by selecting polypropylene homopolymer, which inherently resists hydrolysis and acid attack, and enhancing this inertness through additives that prevent oxidative degradation, effectively creating a protective chemical environment
3Reliability
If PVDF is used for the inner polymeric sealing sheath, then the material provides excellent chemical inertness and high temperature resistance, but it is sensitive to cavitation and has significantly higher cost
Solution Approach 1:
The patent applies the principle of selecting a more economical material (polypropylene homopolymer) that, while not as inherently expensive as PVDF, achieves comparable service life and performance through careful formulation with stabilizers and additives, providing a cost-effective alternative that meets the 20-year service requirement
Solution Approach 2:
The patent changes the material parameters by selecting polypropylene with specific density (0.90-0.92 g/cm³) and melt flow index (0.1-10 g/10min), which optimizes the balance between chemical resistance, mechanical properties, and cost, achieving PVDF-level performance at lower cost
4Adaptability or versatility
If the polymeric sheath is made flexible to accommodate pipe movement, then the pipe adapts to installation conditions, but the sheath becomes prone to extrusion and cavitation under internal pressure
Solution Approach 1:
The patent creates a composite material system where polypropylene homopolymer provides the base matrix with inherent cavitation resistance, while embedded additives (antioxidants, stabilizers, and reinforcing fillers) enhance the material's mechanical strength and extrusion resistance, creating a composite that maintains flexibility without sacrificing durability
Solution Approach 2:
The patent optimizes the melt flow index parameter (0.1-10 g/10min) to control the polymer's viscosity and molecular weight distribution, which directly influences the balance between flexibility for installation and resistance to extrusion under pressure, achieving optimal mechanical properties
Data Source
AI summary
An underwater pipe, including a metal reinforcing layer around an inner polymeric sealing sheath capable of being in contact with hydrocarbons. The inner polymeric sealing sheath includes a homopolymeric polypropylene or a mixture of homopolymeric polypropylenes, wherein the homopolymeric polypropylene or the mixture has a density greater than 0.900 g/cm3, and a melt index measured at 230° C. under a mass of 2.16 kg of less than 10 g/10 minutes, its preparation method and its use for the transport of hydrocarbons. Such a sheath may be used in contact with hydrocarbons at high temperature.