Preventing Axial Leakage in Foam Core Pipes

Axial leakage is a potential problem that can arise in foam core pipes if the foam structure does not meet specific requirements. This refers to the unwanted movement of fluids or gases longitudinally through the foam layer within the pipe wall.

Understanding Axial Leakage Risk

Axial leakage is primarily a risk associated with the foam core's internal structure. If the foam contains interconnected, open cells, it can create pathways for substances to migrate along the pipe's length. This issue is linked to the core's ability to resist shear forces; insufficient resistance can compromise the integrity of the foam structure and its barrier function.

Mitigation through Standards and Design

Recognizing this risk, industry standards for foam core pipes, such as ASTM F891 in the USA, incorporate requirements aimed at preventing axial leakage. A key aspect is the demand for a closed-cell foam structure. To verify this, standards often include specific tests. The ASTM standard, for instance, includes a requirement implemented since 2012 mandating closed cells and provides a test method: a pipe sample (18 inches long) must demonstrate no leaks after being subjected to 10 psi water pressure for 30 minutes. Ensuring sufficient resistance to shear forces within the core formulation and processing helps achieve the required closed-cell structure.

Technical Considerations

• Core Integrity: Core must resist shear forces to prevent skins acting independently and compromising foam structure.
• Cell Structure: Requirement for closed cells to prevent longitudinal flow.
• ASTM Leakage Test: Validates closed-cell structure by checking for water leaks under pressure (18" sample, 10 psi, 30 min).

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