USED FOR:
Welding / Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded). Quality levels for imperfection
Defining the acceptable size and frequency of weld imperfections (porosity, undercut, lack of fusion, etc.) for a given quality level
RELATED STANDARDS:
- ISO 6520-1 “Welding and allied processes – Classification of geometric imperfections in metallic materials – Part 1: Fusion welding”
- ISO 17637 “Non-destructive testing of welds – Visual testing of fusion-welded joints”
- ISO 17635 “Non-destructive testing of welds – General rules for metallic materials”
- ISO 13919-1 “Welding – Electron and laser-beam welded joints – Quality levels for imperfections – Part 1: Steel”
- EN ISO 10042 “Welding – Arc-welded joints in aluminium and its alloys – Quality levels for imperfections”
DIMENSIONAL RANGE:
There is an actual dimensional trigger here, not just a proxy: ISO 5817 applies to material thickness of 0.5 mm and above, with no declared upper ceiling, and covers fully penetrated butt welds and all fillet welds (its principles can also be extended to partial-penetration butt welds by agreement). Below that 0.5 mm threshold the standard simply doesn’t apply, which is why very thin-gauge or precision welded assemblies typically fall back on a different acceptance document. Within that thickness range, most of the individual imperfection limits in the tables (undercut depth, pore diameter, and so on) are themselves expressed as a fraction of the local wall or leg thickness rather than as a fixed millimetre value, which is the real reason the three quality levels stay meaningful across such a wide range of component sizes.
DESCRIPTION:
Three quality levels: B (stringent), C (intermediate), D (moderate); govern what’s acceptable once an imperfection has been detected. It doesn’t tell you how to inspect; it tells you what to do with what you find. We match the quality level to consequence of failure and loading type: cyclic or safety-critical piping almost always calls for Level B.
IMPORTANT NOTES:
ISO 5817 must be read together with ISO 17635 (which links quality level to appropriate NDT method and extent) and ISO 17637 (visual testing procedure). Specifying Level B without specifying the inspection regime that goes with it is an incomplete spec.
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