Multilayer Flexible Pipe Structure for Rapid Gas Decompression
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Solution Overview
Problem
Conventional high-pressure fluid pipes made of materials like polyethylene fail to maintain structural integrity upon decompression due to rapid gas decompression, as gases permeate through the pipe walls, leading to delamination and loss of flexibility.
Innovation Solution
A flexible pipe design featuring a multilayer structure with an innermost layer of ethylene-vinyl alcohol copolymer resin composition, a hydrophobic thermoplastic resin layer, and an adhesive resin layer, which provides excellent gas barrier properties and maintains structural integrity under high pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional materials like polyethylene are used for high-pressure fluid pipes, then the pipe can be manufactured with ease, but the pipe fails to maintain structural integrity upon decompression due to gas permeation and delamination
Solution Approach 1:
The patent employs a multilayer composite structure consisting of an inner layer (polyethylene or polypropylene), an intermediate layer (ethylene-vinyl alcohol copolymer with 90-99 mol% vinyl alcohol content), and an outer layer (polyethylene or polypropylene). This composite structure combines the processability of conventional polymers with the gas barrier properties of EVOH, preventing gas permeation and maintaining structural integrity during rapid decompression while remaining manufacturable through conventional extrusion processes.
Solution Approach 2:
The patent applies different material properties to different layers of the pipe structure. The inner and outer layers use conventional polymers for ease of manufacture and flexibility, while the intermediate layer uses high-vinyl-alcohol-content EVOH specifically for its exceptional gas barrier properties. This localized assignment of material functions resolves the contradiction by placing gas-blocking capability only where needed to prevent delamination during decompression.
2Reliability
If the pipe thickness is increased to satisfy strength and barrier properties, then the barrier performance improves, but the flexibility of the pipe deteriorates
Solution Approach 1:
The multilayer composite structure allows achieving superior gas barrier performance without increasing overall pipe thickness. The EVOH intermediate layer provides exceptional gas blocking capability in a thin configuration, while the outer conventional polymer layers maintain flexibility and handleability. This enables the pipe to be both highly effective at preventing gas permeation and sufficiently flexible for practical applications.
Solution Approach 2:
The patent concentrates the gas barrier function in the intermediate EVOH layer rather than uniformly thickening the entire pipe wall. This localized approach to barrier enhancement maintains overall pipe flexibility while providing sufficient barrier performance to prevent gas accumulation and delamination during rapid decompression events.
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 pipe effectively prevents gas permeation and maintains structural integrity during rapid pressure changes, as demonstrated by passing the rapid gas decompression test, ensuring reliable high-pressure fluid transport without collapse or failure.
Implementation Method 1
the inner layer is a multilayer article having an innermost layer containing the hollow portion, wherein the innermost layer is a layer of the ethylene-vinyl alcohol copolymer resin composition
Implementation Method 2
the pipe is flexible, and wherein the inner layer is a multilayer article having an innermost layer containing the hollow portion
Data Source
AI summary
A flexible pipe comprising at least one layer of ethylene-vinyl alcohol resin (EVOH) as the innermost layer, wherein the pipe is suitable for use under high pressure, is configured to retain mechanical properties at pressures up to at least about 1500 psig, and can also retain its structural function upon decompression.