Functional safety describes the part of a system’s safety that depends on the correct function of the safety-related control system. Safety generally depends also on other risk-reducing measures, which are considered in accordance with EN ISO 12100. E-STOPs, safety gates, light curtains or speed monitoring are just some of the typical safety devices used to safeguard plant and machinery. The rising level of complexity of plant and machinery means that programmable control systems are increasingly being used alongside conventional relays. Both EN ISO 13849 and IEC 62061 ensure compliance with international legislation, e.g. the Machinery Directive. Both standards are paramount for plant and machine builders, because many B and C standards refer to them directly.
Revision of the standards EN ISO 13849 and IEC 62061
Both standards need to be updated to continue to represent the "state of the art". The latest edition of IEC 62061 was published on 19 February 2021. The impetus to revise both standards stemmed not just from the routine revision and upgrade to the state of the art, but also from the many discussions that took place during the failed attempt to unify the two standards within IEC/ISO 17305.
The content of IEC 62061 is known, but the changes to EN ISO 13849 are not yet finalised; however, it is clear that both new editions:
- Require a clear description of the safety requirements specifications, including information such as
- The operating modes during which the function is active (always, only during maintenance, etc.)
- How to monitor safety functions
- When and how to test the safety function
- The associated fault reaction
- Reaction times
- Changed their methodology on how to define the required safety level (PL or SIL)
- Changed requirements with respect to the application software, in line with the complexity and programming language selected
- Allow subsystems that were developed in accordance with one standard to be used within the other
Existing safety concepts must be closely scrutinised
Plant and machine builders should re-assess existing safety concepts with regard to the changed risk classification in the standards. In some cases there will be greater flexibility with regard to the proposed risk parameters. Whether there are any effects on existing safety assessments must be tested on a case-by-case basis.
Transition periods after ratification?
IEC 62061 was published in February 2021; however, due to ongoing discussions in the standards committees, it might be 2022 for EN ISO 13849. It is far from clear whether there will be a transition period for publication of the standards in the Official Journal and if so, how long this might be. For this reason, it is advisable to deal with the expected development early, in other words now.
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