Porosity

The presence of gas voids or cavities in a weld or casting, appearing as rounded discontinuities. Porosity is caused by gas entrapment during solidification, improper shielding gas coverage (in welds), or excessive moisture in coatings. Scattered porosity of small size may be acceptable, but large or clustered porosity weakens material. Porosity is readily detected by radiography and ultrasonic testing.

Detection and Assessment

Porosity must be detected early and accurately characterized to determine safety implications. Multiple NDT methods may be required for comprehensive evaluation.

Acceptance Criteria

Industry standards such as ASME Section V, AWS D1.1, and API standards provide specific acceptance limits. Whether a detected porosity is acceptable depends on material, component function, and applicable code.

Best Practices

• Always follow applicable NDT standards and procedures
• Use properly calibrated and maintained equipment
• Ensure personnel are properly trained and certified
• Document inspection procedures and results completely
• Keep current with industry standards and best practices