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When designing programmable controllers in machines and facilities, EN ISO 13849 and IEC 62061 ensure conformity with international legislation, for example, the Machinery Directive. Both standards were revised in 2021 to ensure they remained up to date with technological developments.
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One particularly pressing reason was the fact that EN ISO 13849 and IEC 62061 previously contained very little relating to the growing tendency towards digitalization: The standards did not give sufficient consideration to either software-based safety solutions, or the networking of automation systems, or the cybersecurity issues that are becoming increasingly important as a result of these technologies. The revisions were also intended to improve consistency between EN ISO 13849-1 and EN IEC 62061.
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There are modifications in several sections in Part 1 of EN ISO 13849. References to other standards, terms and definitions have been updated, and the structure of the standard has been improved. Requirements for validation have now been moved from Part 2 of the standard to Part 1 (Section 10). This change to the standard was carried out in light of the fact that Part 2 is to be withdrawn.
A key aspect of the revised EN ISO 13849 standard is the extensive description of the SRS (Safety Requirements Specification). This part of the standard provides detailed specifications relating to the creation of machine risk assessments for safety functions. There is a new section that describes how safety-related parts of control systems (SRP/CS) should be constructed. The standard describes special safety features in detail, for example, safety-related stop functions, restart functions or interruption of the energy source.
The revised EN ISO 13849-1 also includes detailed requirements for software security. A section on ergonomic aspects has been introduced for the first time. Designing the interface between the operator and the SRP/CS in compliance with this section should mean that the control system can no longer be circumvented and that machines cannot be unintentionally misused or mishandled.
To guarantee EMC interference immunity, Annex L contains practical instructions on how to meet EMC requirements for an SRP/CS or subsystems.
The revised EN ISO 13849-1 standard introduces new factors to determine Performance Levels (PLr). These factors make it easier to classify how possible it is to avoid a hazard (P parameters). The standard also includes a selection aid to help identify parameter P1 or P2.
While EN IEC 62061 previously only applied to electric, electronic or programmable technologies, the updated version does not have this restricted applicability. This means that the standard can now also be applied to hydraulic or pneumatic systems.
There is also a greater emphasis on software. The requirements in the revised EN IEC 62061 standard focus on the avoidance of faults in the software life cycle.
The new version of EN IEC 62061 simplifies the validation of safety-related software. Section 8 defines the “software level” for application software, for example.
Another new element is the Functional Safety Management Plan, which defines the responsibilities and project phases for products with functional safety.
To achieve a greater degree of consistency with IEC 61508 and other standards, the term “SILCL” (SIL Claim) has been replaced with “SIL”.
A new feature of the revised EN IEC 62061 standard is the fact that it defines PFD failure limits according to IEC 61508. If the standard is applied correctly, this means that low-demand applications can now be evaluated according to the Machinery Directive within the scope of a “presumption of conformity”.
The new edition also includes requirements pertaining to cybersecurity. These cover how possible repercussions for functional safety must be assessed.
EN IEC 62061 now includes additional EMC requirements and new annexes on failure rates (Annex C), diagnostic coverage (Annex E) and reliability calculations (Annex K).
The revised versions improve the legibility of the two standards in many places as well as clarifying numerous details. In particular, they ensure a higher level of protection with regard to AI and “smart” applications. Of course, the new versions also have a direct impact on the work of the engineer or planner of a machine or control system. Among other things, the following considerations now apply:
· Following their revision, the two standards EN ISO 13849-1 and EN IEC 62061 are now aligned more closely. Subsystems that were developed in accordance with one of the two standards can now be moved over to the other standard more easily.
· The main new consideration is the effect of cyber-attacks on functional safety. Specific standards such as EN 62443 (IT security for industrial automation systems) also help with this.
The updates to EN ISO 13849-1 and EN IEC 62061 state that the core safety concepts of existing systems should be checked as a basic principle. In particular, the alterations to the classification of risks may in some cases lead to increased flexibility with regard to the risk parameters to be adopted. For example, the new P factor selection aid makes risk assessment considerably more straightforward.
On the other hand, the procedures for calculating the Safety Integrity Level SIL and Performance Level PLr themselves have not changed. The engineer or developer can continue to use the methods for calculating SIL and PLr as described in Eaton’s “Safety manual”, for example. The same applies to circuits that have previously been installed with safety-related controllers. The circuits given as examples in Eaton’s “Safety manual” are still perfectly suitable for being used to achieve the desired functional safety in safety-related applications.
Functional safety is crucial in order to protect people, equipment and the environment. With the right safety-related parts of control systems (SRP/CS), the risks associated with the operation of machinery can be minimized, thereby making it functionally safe. The updates to EN ISO 13849-1 and EN IEC 62061, as well as the forthcoming Machinery Regulation, ensure that standardization reflects the latest technological innovations. For more information on the updates, see Eaton’s white paper “Update on machine safety”.
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