Ensuring Performance: Closed-Cell Structure in Foam Core Pipes
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For foam core pipes, particularly those used in drainage, waste, and venting (DWV) or sewer applications, the structure of the foam core is critical for performance. A key requirement is the presence of a closed-cell structure within the foam.
Function of Closed Cells
A core with insufficient resistance against shear forces can lead to the skins acting independently, reducing the actual stiffness compared to the calculated stiffness. Crucially, if the cells within the foam core are open rather than closed, axial leakage can occur through the foam material. This means liquids or gases could potentially travel along the length of the pipe within the foam layer.
Standards and Testing
To prevent this issue, standards for foam core pipes often include specific requirements related to the cell structure. For example, in the ASTM standard (since 2012), there is a requirement for closed cells. This requirement is verified through a test designed to detect axial leakage. The test involves subjecting a pipe sample to water pressure and checking for leaks.
Technical Specifications
Cell Structure: Requirement for closed cells in the foam core.
Leakage Test (ASTM): No leaks in 30 minutes through an 18-inch pipe sample at 10 psi water pressure. This test verifies the closed-cell requirement.
FAQ Section
Why is a closed-cell structure important for foam core pipes?
A closed-cell structure is crucial to prevent axial leakage, where liquids or gases could otherwise travel through the foam layer along the pipe length, which is a risk if the core lacks sufficient shear resistance.
How do standards like ASTM ensure the closed-cell structure?
The ASTM standard (since 2012) includes a specific requirement for closed cells, verified by a test where the pipe must show no leaks in 30 minutes when subjected to 10 psi water pressure over an 18-inch length.
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Humberto Goldoni
