ISO standard · reference card
Which part of the ISO 3834 series applies? Selection-criteria decision flow for the fusion-welding quality-requirements standard, the parts it points to, and the records that back the level you declare.
ISO 3834-1 answers a question that comes before any acceptance standard: which set of quality requirements does this manufacturer actually need to meet? Its output is a decision — Part 2, 3 or 4 — and that decision governs which requirements apply everywhere else in the series.
The recurring failure is skipping this part and guessing. Defaulting to Part 2 out of caution pays for controls the work does not need; defaulting to Part 4 invites a certification body to challenge the declaration once safety-critical work appears.
The criteria are proportionality-based, not a checklist with one right answer per industry: safety consequence, metallurgical demand and process range all weigh in. EN 1090-2 pre-answers the question for structural steelwork by mapping execution classes onto a part; elsewhere the manufacturer runs the logic and keeps the reasoning on file — an auditor’s first question is rarely “which part,” it is “why this one.”
Once a part is selected, ISO 3834-5 lists the further documents that declaration depends on. Therness equipment sits under that layer regardless of which part governs: the same per-weld thermal and parameter trail supports a Part 2 declaration or a Part 3 one, because what changes between parts is the depth of control expected, not the shape of the evidence a monitoring system produces.
| Question | If yes | If no |
|---|---|---|
| Does an application standard or the contract already name a part? | Work to the part it names; this part's criteria do not override a requirement already stated. | Apply the selection criteria in this part directly, and keep the reasoning on file. |
| Is the product safety-critical, or does it involve a wide range of materials, thicknesses or joint types? | The comprehensive requirements of Part 2 are the expected route. | A lighter part may be proportionate; the reasoning still has to be documented. |
| Is production straightforward — a narrow material range, established processes, low consequence of a defect? | Part 3 or Part 4 may be adequate, chosen by the same proportionality logic this part sets out. | Move back toward the comprehensive requirements of Part 2. |
| Is the manufacturer genuinely unsure between two adjacent parts? | Select the higher part. Downgrading later needs its own justification, and an auditor will ask for it. | Record the decision once, naming the criteria actually used. |
| Does the manufacturer already run a certified quality management system, such as ISO 9001? | Clause 6 of this part identifies which quality-management elements complement the series. | The quality-management elements the declared part expects still have to be demonstrated separately. |
Conformity is decided by inspection and testing against the criteria the standard and the contract set. The records below are evidence that the process was held where it was qualified; they support an inspection result, they never replace one.
| Requirement | Record produced | Source |
|---|---|---|
| Evidence the declared level of quality control is actually applied in production | Continuous per-weld thermal and parameter records tied to the declared scope | HeatCore AI |
| A traceable link between each weld and its welder, procedure and equipment | Weld identifier, operator, timestamp and process record in one export | WeldTrace |
Therness records what the machine actually delivered on every weld — parameters, thermal signature and a per-weld trail — so a conformity argument rests on measurements instead of recollection.
Progetto cofinanziato nell'ambito del PR Piemonte FSE+ 2021-2027,
Priorità I, Obiettivo Specifico a), Azione 4 – "Sostegno alla nascita delle start up"
