A radiographic pore indication and a through-leak are different observations. A pore can be isolated inside weld metal; a connected network or another discontinuity can link the oil side to the outside. The same weld may need separate structural and leak-integrity decisions. [1]
Ask which boundary the evidence crosses
| Observation | Supported conclusion | Unresolved question |
|---|---|---|
| Isolated image indication | Discontinuity visible under that examination | Actual three-dimensional connectivity |
| Clustered image indications | Multiple discontinuities in projection | Whether they join into a path |
| Leak signal | Transfer through a path under test conditions | Defect shape and structural significance |
| No detected leak | No leak above demonstrated capability | Other defects or leaks outside test sensitivity |
Preserve the method limits
Imaging collapses or samples geometry under its particular technique. An apparent cluster in projection does not prove connection. A leak test is driven by the test medium and pressure boundary; it can detect transfer without identifying the whole defect shape.
Use the applicable structural acceptance criteria for porosity and the specified leak criteria for the oil boundary. A nonleaking pore can still be unacceptable structurally, and a small leak path can matter even when its volume is difficult to image.
Choose NDT using material, weld thickness, welding process, quality requirements and demonstrated coverage. NDT acceptance levels are not a detailed one-to-one translation of weld quality levels. [2]
Keep pore size and leak response separate
Assume two weld records show equal 1 mm projected pore diameter, but one has a confirmed through-leak and the other has no detected leak above the demonstrated sensitivity. The projected size does not establish connectivity. Apply structural and leak criteria to their respective final weld states; neither result substitutes for the other.
References
- U.S. Federal Highway Administration, Bridge Welding Reference Manual, FHWA-HIF-19-088, 2019.
- ISO, ISO 17635:2025, Non-destructive testing of welds — General rules for metallic materials.