Internal porosity is a casting condition, not a single inspection specification. The required examination depends on the alloy, manufacturing route, section thickness and function of the part. A pressure-retaining casting and a lightly loaded housing may have different acceptance requirements.
Radiographic techniques can show changes in transmitted intensity associated with internal discontinuities. Ultrasonic techniques can investigate suitable castings, but the material structure and geometry may limit penetration or interpretation. Neither method guarantees detection of every pore.
Separate a search for volumetric porosity from investigation of cracks or other discontinuities. Orientation and geometry influence detection, so one successful demonstration should not be extended to every flaw type.
Identify heavy sections, abrupt thickness changes, riser-removal areas and other locations the product specification requires. Document accessible surfaces and any regions where the chosen arrangement cannot establish the required coverage. If reference specimens or images are used, confirm that their application matches the specified material and technique.
An image should be evaluated using the applicable acceptance reference and its conditions. Avoid assigning an acceptance level from an unrelated product standard because the examples look similar.
Tie the report to the casting identity, heat or batch information and drawing revision. Record the examination arrangement, reference checks, findings and limitations. Where repair is permitted, preserve the original examination and repair record before re-examination. The responsible product authority decides whether the evidence supports acceptance, repair or further investigation.
ASNT’s overview of NDT methods provides further background. Use the governing specification and approved procedure for the actual job.
Discuss the examination scope. Include the component, material, service history and decision the inspection needs to support.