Oriented Pipe End Thickening for High-Burst-Pressure Joining
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Solution Overview
Problem
Biaxially oriented polymer pipes experience a significant decrease in mechanical properties, particularly burst pressure, when joined using conventional methods like butt welding, as the orientation is lost at the joint, leading to suboptimal performance.
Innovation Solution
A modification process involving the placement of an insert within the pipe end, followed by localized heating to create a thickened end portion that maintains orientation in the hoop direction, allowing for high burst pressure retention during joining without requiring special equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If butt welding is used to join biaxially oriented pipes, then the joining process is simple, but the burst pressure decreases significantly due to loss of orientation at the joint
Solution Approach 1:
The insert is placed inside the pipe end before the heating and joining process. This preliminary placement ensures that when the end portion is heated and shrinks, the insert constrains the inner periphery to maintain hoop orientation, preventing the orientation loss that would otherwise occur during the joining process
Solution Approach 2:
The insert acts as an intermediary tool that temporarily occupies the pipe interior during modification. It serves as a constraint that prevents radial shrinkage while allowing axial shrinkage, thereby maintaining the hoop orientation of the polymer chains at the joint region without requiring complex external equipment
2Reliability
If mechanical joining methods are used to preserve orientation, then burst pressure is maintained, but the joining process becomes more complex and requires special equipment
Solution Approach 1:
The invention replaces complex mechanical joining equipment with a simple thermal processing approach. Instead of using sophisticated mechanical alignment and joining devices, the method uses localized heating to soften the polymer, allowing the end portions to be joined through simple push-together mechanics while the insert maintains orientation
Solution Approach 2:
The invention changes the physical state of the pipe material by heating it to a temperature where the polymer becomes soft and pliable. This parameter change (temperature increase) allows the end portions to be deformed and joined easily, while the insert ensures that hoop orientation is maintained during this transitional state
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 process enhances the burst pressure at the joined butt ends by retaining orientation in the hoop direction, resulting in improved mechanical properties while simplifying the joining process by eliminating the need for specialized equipment.
Implementation Method 1
heating the end portion such that the end portion axially shrinks while the inner periphery of the cross section of the end portion is substantially maintained
Implementation Method 2
the end portion axially shrinks while the inner periphery of the cross section of the end portion is substantially maintained
Data Source
Figure 1~2
AI summary
The invention relates to a modification process for modifying a biaxially oriented pipe, comprising a) providing a biaxially oriented pipe made by stretching a tube made of a thermoplastic polymer composition in the axial direction and in the peripheral direction, b) placing an insert within an end portion of the pipe, wherein the outer periphery of the cross section of the insert substantially matches the inner periphery of the cross section of the pipe and c) heating the end portion such that the end portion axially shrinks while the inner periphery of the cross section of the end portion is substantially maintained, to obtain a modified biaxially oriented pipe with a thickened end portion