EVOH Barrier in Coextruded Pipe Insulation
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Solution Overview
Problem
The existing plastic casing pipes face issues with insulation aging due to oxygen penetration, leading to reduced thermal insulation and mechanical failure, especially at high temperatures, as the gas permeation barrier layers in prior solutions are prone to damage during manufacturing or mechanical stress.
Innovation Solution
A method involving a gas permeation barrier layer made of ethylene-vinyl alcohol copolymers (EVOH) integrated within the plastic outer pipe, coextruded with other layers to prevent oxygen ingress and maintain insulation properties, ensuring a closed system that protects the barrier layer from damage and maintains adhesive bond integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gas permeation barrier layer is applied to prevent oxygen ingress, then insulation aging is prevented and thermal insulation value is maintained, but the barrier layer is prone to damage during manufacturing or mechanical stress
Solution Approach 1:
The gas permeation barrier layer is integrated within the plastic outer pipe as a nested structure, with the barrier layer surrounded by protective plastic material on both inner and outer sides. This nesting approach protects the fragile barrier layer from mechanical damage during manufacturing and service while maintaining its gas permeation barrier function.
Solution Approach 2:
The plastic outer pipe is constructed as a composite material system combining the gas permeation barrier layer with plastic materials (such as polyethylene) that provide mechanical protection. This composite structure allows the barrier layer to perform its gas sealing function while the plastic material absorbs mechanical stresses and protects the barrier from damage.
2Reliability
If the diffusion-regulating layer is arranged on the outside of the outer pipe, then gas permeation is controlled, but the layer is damaged or destroyed by mechanical effects
Solution Approach 1:
The gas permeation barrier layer is nested within the plastic outer pipe structure rather than being placed on the outside. This positioning ensures the barrier layer is surrounded and protected by the mechanically stronger plastic material, preventing damage from external mechanical effects while maintaining gas permeation control.
3Reliability
If the diffusion-regulating layer is arranged between the outer pipe and the polyurethane foam, then gas exchange is reduced, but the inner pipe damages or destroys the layer during threading
Solution Approach 1:
The gas permeation barrier layer is nested within the plastic outer pipe, positioned such that it is surrounded by plastic material on the inner side. This arrangement prevents direct contact between the inner pipe (steel pipe) and the barrier layer during the threading process, eliminating the damage mechanism while maintaining gas exchange reduction.
Solution Approach 2:
The plastic material acts as an intermediary layer between the inner pipe and the gas permeation barrier layer. This intermediary plastic layer prevents direct contact and potential damage from the inner pipe while allowing the barrier layer to maintain its gas permeation control function.
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
This solution effectively prevents insulation aging, maintains thermal insulation value, and ensures mechanical characteristics over the service life of the plastic casing pipe, allowing for higher temperatures without reducing service life, while being easy to manufacture and connect without damaging the gas permeation barrier layer.
Implementation Method 1
oxygen, in particular, penetrating through the plastic outer pipe. Due to the penetrating oxygen, oxidation processes occur within the insulation
Implementation Method 2
gas permeation barrier layer made of ethylene-vinyl alcohol copolymers (EVOH) integrated within the plastic outer pipe
Implementation Method 3
coextruded with other layers to prevent oxygen ingress and maintain insulation properties
Data Source
Figure 1~2
AI summary
The plastic coating pipe has a medium pipe made of steel, a plastic external pipe serves as mechanical protective coating and an annular gap provided between the medium pipe and an external pipe (3). The external pipe is formed as multi-layer pipe and has a permeation barrier (4) made of plastic. The permeation barrier is integrated in the external pipe. The permeation barrier is made of ethylene-vinyl alcohol copolymer. The external pipe is made of polyethylene, particularly cross linked high-density polyethylene. An isolation unit is made of rigid form, particularly polyurethane rigid foam. An independent claim is also included for a method for manufacturing a plastic coating pipe.