IEC 62061 applies IEC 61508 functional safety principles to the machinery sector, using SIL 1-3 language. It is the SIL-based alternative to ISO 13849 (PL-based). Both are harmonized under the EU Machinery Directive 2006/42/EC.
IEC 62061:2021 Single-part standard. Defines SRECS (Safety-Related Electrical Control Systems), SIL 1-3 framework for machinery, PFHD targets, architectural constraints, software requirements adapted from IEC 61508-3.
(SRECS) (SIL CL) (PFHD) Both are harmonized under the EU Machinery Directive 2006/42/EC. Both cover the safety control system of a machine. They produce the same level of risk reduction if applied correctly. The choice is mostly about vocabulary and tooling preferences:
| Aspect | ISO 13849-1 | IEC 62061 |
|---|---|---|
| Vocabulary | PL a-e, Categories B/1/2/3/4 | SIL 1-3, Architectures A-D |
| Origin | Mechanical engineering tradition (ex-EN 954-1) | IEC 61508 machinery adaptation |
| Mode | High demand only (PFHD) | High demand only (PFHD) |
| Software | Simplified treatment | Full IEC 61508-3 software requirements |
| Component certification | Wide (Pilz, Sick, Schmersal libraries) | Wide (overlaps with IEC 61508) |
| Designer tool | SISTEMA (free, IFA) | Spreadsheet calculators, less mature tooling |
| Best fit | Standard machinery (assembly lines, conveyors, presses) | Complex machinery with significant programmable electronic content |
In practice: ISO 13849 dominates Europe for typical machinery. IEC 62061 is used when:
IEC 62061 simplifies architectures into 4 classes:
| Arch | Description | Equivalent ISO 13849 |
|---|---|---|
| A | Single channel, no diagnostics | Cat B / 1 |
| B | Single channel with diagnostics (test before use) | Cat 2 |
| C | Redundant channels (1oo2), no diagnostics | Cat 3 (partial) |
| D | Redundant channels with cross-monitoring + diagnostics | Cat 3 / Cat 4 |
For SIL 3 (the typical maximum in machinery), architecture D is required: dual channel with cross-monitoring achieving DC > 99%.
ISO and IEC started a joint project — IEC/ISO 17305 — to unify ISO 13849 and IEC 62061 into a single standard. The work was suspended around 2015 due to unresolved methodological differences. As of 2026, both standards remain active and both will continue to be harmonized under the upcoming Machinery Regulation 2027 (replacing the 2006 Directive).
For practitioners: pick one, document the choice in your Safety Requirements Specification, and stick with it for the whole machine. Mixing approaches on the same SRECS creates documentation nightmares.