On what criteria should a defect identified during the visual testing of weld seams be accepted?

A defect detected on a weld seam during standardized quality control does not necessarily mean it is unacceptable. To decide, one must refer to the acceptance criteria set by the quality standard implemented for the visual testing of welding.

Acceptance criteria for a welding imperfection in visual testing

To decide whether a welding imperfection observed during visual testing is acceptable or not, it is necessary to refer to the acceptance criteria provided by the quality welding standard in place:

  • EN 1090-2
  • ISO 3834
  • EN 15085
  • ISO 9606
  • Other

In general, all these welding quality management standards are based on the EN ISO 5817 standard. Depending on the quality level demanded by the standard, it gives mathematical formulas to apply in order to calculate the permissible tolerances.

The EN ISO 5817 standard sets three levels of quality:

  • Basic :                level D
  • Normal :           level C
  • Strict :                level B

The tolerances for welding imperfection will be all the more stringent as the demanded quality level for the weld seam is significant.

Here is an excerpt from the EN ISO 5817 standard concerning the quality of welds:

Exemple de défaut de soudure selon la norme ISO 6520-1 et détail de l'exigence de cette norme
Exemple de défaut de soudure selon la norme qualité des cordons de soudage ISO 6520-1 et du détail de l'exigence de cette norme avec des niveaux de qualité B, C ou D.

In the excerpt above, when a undercut type welding imprefection (5011 or 5012) is detected on a 5mm thick steel sheet:

If the required welding quality level is D

the height ‘h’ of the undercut must be less than or equal to: h ≤ 0.2*5mm, i.e., h ≤ 1mm (in addition to being a short defect)

If the required welding quality level is B

no undercut is allowed

It is always important to refer to the welding quality management standard in place because it sets the acceptance criteria for imperfection.

For example, under the EN 1090-2: EXC2 standard (§7.1), the acceptance criteria correspond to the EN 5817 quality level C except for the following welding imperfections:

  • Undercut (5011,5012) – overflow (506) – accidental arc strike (601) – open crater shrinkage (2025): quality level D is required
  • Lack of inter-run fusion (505) – micro lack of fusion (401): always allowed

What is the classic method of control for welding beads and why is it difficult to conduct a visual inspection with the classic measuring tools for welds?

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