To ensure the safety of machines and those who operate them, safety measures are needed. Machinery control systems that provide safety functions will not only detect the risk but, additionally, take preventive action to decrease the risk.
The IEC has published a new edition of IEC 62061, Safety of machinery – Functional safety of safety-related control systems. This standard provides an approach to achieve the necessary performance of the safety functions in order to reduce the potential hazards generated by machines. Compared to the previous edition, the scope of the standard has been broadened to include non-electrical systems.
According to Wolfgang Reinelt, Project Leader for the new edition of IEC 62061, “The aim of IEC 62061 has been to apply the requirements of functional safety to the machine sector. With the updated edition of IEC 62061, we have addressed new areas such as non-electronic technologies, software aspects, security and testing.” This edition also offers improvements in terms of structure, readability and the inclusion of many new examples.
IEC 62061 provides a methodology and requirements to determine the safety integrity for each safety function, enables the design of appropriate safety functions and integrates safety-related subsystems. In addition, the standard provides measures to validate the safety functions.
Understanding functional safety
The IEC has published a horizontal series of standards, IEC 61508, which provides functional safety requirements applicable to a wide range of industry sectors. It requires the analysis of the potential risks or hazards of a given system or device and provides categories to determine the level of likelihood of a potential hazard and the consequences should it occur. Safety integrity levels (SIL) are defined to indicate the degree to which a system will meet its specified safety functions.
IEC 62061 offers a specific safety standard for the machine industry that is fully aligned with IEC 61508 including its SIL scheme, principles and vocabulary. According to Reinelt, “With IEC 62061, we have been able to specify principles that are very specific to the machine industry that are not discussed in IEC 61508.”
Broadening its scope
The second edition of IEC 62061 has enhanced several key areas: functional safety management that addresses the machinery workflow, extending the scope to include non-electrical technologies and safety-related software. Greater emphasis has also been given to software aspects in order to surpass requirements specified in older standards.
Requirements in the new edition of IEC 62061 focus on the avoidance of faults in the software lifecycle and ensuring that the requirements generate readable, understandable, testable, maintainable and correct software.
With the convergence of the OT and IT environments, security is increasingly becoming an important factor that can affect safety. Security is included in the new edition of IEC 62061. As Reinelt explains, “The present philosophy in IEC 62061 considers that security has to be considered in safety-related control systems. It requires that security measures should not have an adverse effect upon safety.”
The edition of the standard also calls for security risk assessments in order to identify the threats and vulnerabilities of the safety-related control system.
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