ISO 13849-1 is the international standard that gives a methodology, requirements and guidance for designing and integrating the parts of machine control systems that perform safety functions. A circuit that stops the motor when a guard door opens, or a press that halts when a light curtain is interrupted, falls within its scope. The result is expressed as a performance level (PL), a five-step scale from a to e.
According to the International Organization for Standardization (ISO), the current version is the fourth edition, published in April 2023 (ISO 13849-1:2023), which replaced the 2015 edition. The second route in the same field is IEC 62061; the International Electrotechnical Commission (IEC) describes it as a machinery-specific standard within the framework of IEC 61508, the generic functional safety standard.
In short:
- ISO 13849-1 expresses its result as PL a to e; IEC 62061 uses the safety integrity level (SIL).
- IEC 61508 is the basic framework that sector standards build on; SIL has four levels (IEC).
- In the EU, Machinery Regulation 2023/1230 applies from 14 January 2027 and replaces Directive 2006/42/EC.
What is functional safety?
By IEC's definition, functional safety is the part of overall safety that depends on a system or equipment responding correctly to its inputs. IEC's own example makes the point: a level switch that closes a valve when a tank of flammable liquid reaches a dangerous level is functional safety; a fire-resistant door is a passive measure and is not.
The same distinction holds for machinery. A fixed guard reduces risk but is not functional safety; an interlocking circuit that stops motion when a door opens is, and it falls under ISO 13849-1 or IEC 62061.
What does ISO 13849-1 cover, and what is PL?
According to ISO's abstract, ISO 13849-1:
- Covers the design of safety-related parts of control systems (SRP/CS), including software design.
- Is technology-neutral: it applies to electrical, hydraulic, pneumatic and mechanical systems.
- Applies to high-demand and continuous modes of operation; for low-demand mode it points to the IEC 61508 series.
- Does not specify which safety functions or which required performance level (PLr) to use in a particular application.
- Gives no security measures; it refers to ISO/TR 22100-4 and IEC/TR 63074 on that subject.
In practice the flow is: the required level (PLr) for each safety function is derived from the risk assessment, then the PL achieved by the designed circuit is determined and compared with the PLr. The application report of IFA, the German occupational safety institute, shows with component-level example circuits how performance levels a to e can be engineered with Categories B to 4. Put simply, the category describes the structure of the circuit, while PL describes how reliably that circuit performs its safety function; the two are not the same thing.
How does IEC 62061 differ from ISO 13849-1?
According to IEC's catalogue entry, IEC 62061:2021 (edition 2.0, 22 March 2021) sets requirements and recommendations for the design, integration and validation of safety-related control systems for machines. It applies to machines that are not hand-portable while working and to groups of machines working together in a coordinated way; electrical hazards of the control equipment itself and the design of complex programmable electronic subsystems are out of scope. An amendment was added in 2024.
The practical differences can be summarised as follows:
- Metric: ISO 13849-1 uses PL (a to e), IEC 62061 uses SIL.
- Framework: IEC 62061 is explicitly the machinery standard of the IEC 61508 family; ISO 13849-1 defines its own method but refers to IEC 61508 for low-demand mode.
- Technology emphasis: ISO 13849-1 explicitly lists hydraulic, pneumatic and mechanical parts in its scope; IEC 62061's catalogue summary speaks in terms of control systems and subsystems.
In Orient Global's view, the two standards are not rivals but two routes to the same question. Whichever route is chosen, what matters is that the choice is documented for each safety function and applied consistently from design through validation.
Where does IEC 61508 fit in?
According to IEC, IEC 61508 is the common framework for functional safety in electrical, electronic and programmable electronic systems, and the foundation for sector standards in manufacturing, energy, transportation, healthcare and process automation. It has seven parts; normative requirements are in parts 1 to 4, which are basic safety publications that IEC committees must use when preparing their own sector standards. The current edition 2.0 was published in April 2010.
By IEC's definition, a safety integrity level is one of four levels, each corresponding to a range of target failure likelihood for a safety function, and it is a property of the function rather than of a system. For the railway counterpart, see our article on RAMS and EN 50126.
How does the EU Machinery Regulation affect these standards?
The European Union's Machinery Regulation 2023/1230 applies from 14 January 2027, and Machinery Directive 2006/42/EC is repealed on the same date. Among the regulation's essential health and safety requirements is a heading devoted to the safety and reliability of control systems. For Turkish manufacturers selling machinery or machinery components into the EU, this timetable may mean reviewing technical files and design verifications. The current status of Türkiye's national alignment legislation should be checked in the texts published by the competent ministry; this article is not legal advice.
Conclusion: where to start with machinery functional safety?
ISO 13849-1 and IEC 62061 make the required reliability of a machine's safety functions measurable; one speaks the language of PL, the other of SIL, and both rest on the approach set out by IEC 61508. A practical start is to derive the list of safety functions and the required level for each from the risk assessment, decide function by function which standard to use, and update technical files in line with the 2027 timetable.
"Functional Safety (Machinery)" is part of Orient Global's corporate training catalogue; details are on the trainings page.
This article is for general information only and is not legal advice; current legislative texts prevail.
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