REGULATIONS & COMPLIANCE
BETTER TO BE ON THE SAFE SIDE
ISO 13849 is a critical element to ensure safe machinery, allowing manufacturers to have confidence that they are operating in a well-defined functional safety environment
Stewart Robinson MIET MInstMC, Advisory Consultant and Functional Safety Expert at TÜV SÜD, says its vital that manufacturers understand the requirements of ISO 13849-1
safety related control function is one of the measures that makes a contribution to the overall reduction of risk with machinery. ISO 13849-1:2023 is a safety standard which applies to parts of machinery control systems that are assigned to providing safety functions. It provides safety requirements and guidance on the principles of design, and the integration of safety-related parts of control systems (hardware or software).
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ISO 13849-1:2023 was listed in the European Union Official Journal on May 15, 2024. As it was published in the Commission Implementing Decision (EU) 2024/1329, this provides a presumption of conformity for the standard under the Machinery Directive 2006/42/EC. The transition period for EN ISO 13849-1:2015 ends on May 15, 2027. After this date, the 2023 version will be the primary standard for safety-related parts of control systems and will have a presumption of conformity with corresponding EU rules, and it will be also become listed as a designated standard in the UK. However, as the Machinery Directive will be replaced on 20 January 2027 by the new Machinery Regulation , the transition period for EN ISO 13849-1:2015 will, in reality, be shorter. ISO 13849-1 provides safety requirements and guidance on the principles for the design and integration of safety-related parts of control systems (SRP/CS). This includes the design of software, and the standard includes specific requirements for SRP/CS using programmable electronic systems. It also specifies characteristics that include the Performance Level required for carrying out safety functions. The standard applies to
24 OCTOBER 2025 | PROCESS & CONTROL
SRP/CS for high demand and continuous mode, regardless of the type of technology and energy used (electrical, hydraulic, pneumatic, mechanical, etc.), for every type of machinery.
The whole document has been reorganised to better reflect the design and development process for control systems and the following discusses some, but not all, changes. The standard now includes a focus on risk assessment recommendations. For example, Figure 2 of Clause 4 is an enhanced version of Figure 1 in the current version - breaking out the ‘three-step process’ of risk reduction. Alongside this, Clause 4.6 (subsystems) is new, while significant parts of Clause 4 have been moved to their own clauses for specification, design, and verification.
Throughout the standard there is an increased focus on the decomposition of functions into subsystems. And the term ‘subsystem’ is used extensively, for example in Clause 6 – Design Considerations. Again, this clause has been restructured and includes a new sub-clause for systematic failures (6.1.7). There is also a new Clause 7 on software safety requirements. Changes and additions include explaining the differences between limited variability language (LVL) and full variability language (FVL), and guidance in deciding between them. Both LVL and FVL can be used for safety-related application software (SRASW) in accordance with ISO 13849. Greater rigour is required for LVL due to the complexity.
Clause G.5 of Annex G covers the management of functional safety, requiring a functional safety plan to be drawn up and
documented for each SRP/CS design project, which should be updated as any changes to the system are made. Key features of a functional safety plan should include: • The identification of the relevant activities in the SRP/CS design process and confirmation of the order in which they should take place. • The identification of the roles and resources required for actioning and reviewing activities. • The creation of a validation plan. There is also a new Annex L on
electromagnetic interference (EMI) immunity. Example sources of EMI are both natural, such as static & lightning, and manmade intentional transmission and unintentional interference, such as electronics, electric power, communications, machines, and ignition systems. It provides a scoring methodology (table L.1) that can be used where equipment that integrates electronics can be assessed by considering various measures to achieve immunity.
Annex M includes additional information for safety requirements specification, while Annex N also introduces the concept of fault-avoiding measures for the design of safety related software. Meanwhile, Annex O now covers safety-related values of components or parts of the control systems. This is extracted from a data library format created by the German machinery manufacturers association (VDMA). It has been around for some years and is used in applications like SISTEMA to help with the calculations for hardware reliability. Carrying out the calculations required by EN ISO 13849-1 is a complex task, and while software solutions can help, it still remains a resource-hungry process. However, it is vital that manufacturers understand its requirements and their associated responsibilities.
TÜV SÜD
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