Expansion Compensator for Plastic Piping Thermal Stress
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Solution Overview
Problem
Thermoplastic pipes used in piping systems, such as PVC and CPVC, are prone to failure due to thermal expansion and contraction, leading to axial forces that can cause leaks and require costly and time-consuming repairs, especially in high-rise buildings where mechanical constraints exacerbate the issue.
Innovation Solution
An expansion compensator comprising an outer metal conduit and an inner plastic liner, where the inner plastic liner is secured to the outer metal conduit to absorb thermal cycling stresses, allowing the metal conduit to absorb most of the axial forces, thereby reducing stress on the plastic liner and preventing leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermoplastic pipes are used to convey hot water, then the piping system can provide hot water distribution, but the pipes are subject to thermal expansion and contraction causing axial forces that lead to failure and leaks
Solution Approach 1:
The piping system is segmented by inserting an expansion compensator device between pipe sections. This compensator includes a flexible element that can expand and contract independently, separating the thermal expansion issue from the rigid pipe connections and preventing failure at joint locations.
Solution Approach 2:
The expansion compensator incorporates a flexible element with varying stiffness characteristics along its length, allowing it to accommodate thermal expansion through controlled deformation. The flexible element's material properties and geometric parameters are designed to absorb axial forces generated by thermal cycling.
2Length of moving object
If plastic pipes are mounted vertically in high rise buildings, then water can be transported between floors, but mechanical constraints from transverse pipe attachments exacerbate thermal expansion forces causing buckling
Solution Approach 1:
The expansion compensator acts as an intermediary device between the constrained vertical pipe sections. It absorbs the thermal expansion forces that would otherwise be transmitted to the mechanically constrained pipe locations, preventing buckling and bending in the vertically mounted piping system.
3Reliability
If expansion compensators are installed to reduce thermal stresses, then piping system reliability improves, but the device complexity increases
Solution Approach 1:
The expansion compensator utilizes a flexible element constructed from layered composite materials including flexible circuits and thin film structures. These flexible shells provide the necessary compliance for thermal expansion while maintaining structural integrity, achieving reliability improvement with relatively simple geometric configurations.
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 expansion compensator effectively mitigates thermal expansion and contraction stresses, reducing the likelihood of leaks and enhancing the reliability of plastic piping systems, allowing for their use in long runs without the risk of buckling or cracking.
Implementation Method 1
Thermoplastic pipes (such as polyvinyl chloride (PVC) and/or chlorinated polyvinyl chloride (CPVC) pipes) may be subject to thermal expansion and/or contraction after installation
Implementation Method 2
an expansion compensator may expand and/or contract in response to an applied axial force (compressive or tensile)
Data Source
AI summary
Methods for producing an expansion compensator by: providing an inner plastic liner having first and second spaced apart ends, an inner surface, an outer surface, and an interior volume extending from the first end to the second end; positioning the inner plastic liner interior of an elongate metal conduit, the elongate metal conduit having first and second spaced apart ends, an inner surface, an outer surface, and an expansion/contraction section; applying pressure to a fluid positioned in the interior volume of the inner plastic liner while the inner plastic liner is at or above a forming temperature to expand the inner plastic liner whereby the expanded inner plastic liner has an expansion/contraction section; and cooling the inner plastic liner to below the forming temperature.