Composite Pipe Lining With Elastomeric Buffer Against Cracking
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Solution Overview
Problem
Existing internal pipe linings face issues such as cracking due to exothermic reactions and radial shrinkage during curing, inadequate adhesion leading to hydrostatic infiltration, and inability to withstand internal pressure and external loading without compromising structural integrity, especially in Class IV linings for potable water applications.
Innovation Solution
A composite laminate pipe lining system comprising a low modulus elastomeric first layer and a high modulus rigid polymeric second layer, with an optional third layer for additional resistance, where the rigid layer is bonded to the elastomeric layer rather than the pipe substrate, allowing for strain absorption and minimizing adhesion-related issues, and an intermediate reinforcing layer for enhanced strength and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermoset polymeric materials are applied thickly in one pass to create a rigid internal lining, then the lining provides improved structural properties, but the increased exothermic reaction causes embrittlement and cracking of the polymer
Solution Approach 1:
The patent divides the single thick polymeric layer into multiple thinner layers applied in sequence. This segmentation reduces the exothermic reaction intensity in each layer, preventing embrittlement and cracking while still achieving the desired structural strength through cumulative thickness. The method applies multiple coats of thermoset polymeric material, allowing each layer to cure properly without excessive heat generation.
2Strength
If the polymeric material is adhered directly to the pipe substrate, then adhesion strength is improved, but radial and longitudinal shrinkage during curing causes cracking
Solution Approach 1:
The patent introduces an intermediate elastomeric layer between the rigid polymeric lining and the pipe substrate. This intermediate layer acts as a buffer that accommodates shrinkage stresses during curing, preventing cracking in the rigid polymeric layer while maintaining adhesion to the substrate through the compliant intermediate layer.
Solution Approach 2:
The patent changes the mechanical properties of the intermediate layer to have elastomeric characteristics with higher elasticity and lower modulus than the rigid polymeric layer. This parameter change allows the intermediate layer to deform and absorb shrinkage stresses, preventing crack propagation from the substrate interface into the rigid lining.
3Strength
If the rigid lining is firmly adhered to the pipe wall, then adhesion is improved, but the lining cannot survive fractures or deformations in the pipe
Solution Approach 1:
The patent changes the mechanical parameters of the intermediate layer to have elastomeric properties with high elasticity and low modulus. This allows the intermediate layer to deform with pipe fractures and movements while maintaining the connection between the rigid lining and substrate, preventing adhesion failure.
Solution Approach 2:
The elastomeric intermediate layer serves as a mediator between the rigid polymeric lining and the pipe substrate. It provides a compliant interface that can accommodate pipe deformations and fractures, allowing the rigid lining to remain intact while the pipe undergoes structural changes.
4Reliability
If an attempt is made to impede adhesion to the host pipe using mold release, then adhesion is reduced to prevent cracking, but the rigid lining detaches after curing creating an annulus
Solution Approach 1:
The elastomeric intermediate layer acts as a mediator that provides controlled adhesion between the rigid polymeric lining and the pipe substrate. It maintains sufficient bond strength to prevent detachment and annulus formation while accommodating shrinkage and deformation through its elastic properties.
Solution Approach 2:
The patent creates a composite structure with three distinct layers: the rigid polymeric lining, the elastomeric intermediate layer, and the pipe substrate. This composite material system combines the advantages of rigid strength with elastomeric compliance, achieving both adhesion and crack resistance simultaneously.
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 solution provides a structurally independent lining that maintains hydrostatic integrity, withstands internal pressure and external loading, and prevents infiltration by absorbing and distributing strain, meeting Class IV standards for potable water systems and other fluid applications.
Implementation Method 1
an elastomeric layer is provided between the inner pipe surface and the rigid internal layer... which has the capability to expand and yield to reduce the reaction forces between the rigid liner and the pipe when these strains occur
Implementation Method 2
thermoset polymeric materials used to create a rigid internal lining are unable to adequately resist cracking caused by exothermic reaction and or radial shrinkage during the curing process
Implementation Method 3
there is always some radial and longitudinal shrinkage during curing, and if the polymeric material is adhered directly to the pipe substrate this shrinkage can cause cracking of the polymeric material
Data Source
AI summary
A pipe lining having at least two material layers, a first elastomeric layer spray applied directly to the inside of a pipe which acts as a hydrophobic, ductile membrane, and a second rigid layer is spray applied to the first layer prior to complete curing of the first layer. One or more additional layers may be applied to the second layer to provide additional abrasion, erosion or chemical resistance to the second layer. An intermediate reinforcing layer may be disposed between the first and second layers. The first layer cures into a closed cell elastomeric foam, such that stress and other forces are not passed from the pipe to the rigid second layer.