Updated IEC Standard ensures the functional safety of machinery

An alert is given that a hazardous zone has been breached: a person has entered the zone and may be at physical risk. As a result, the machine operating in that zone is automatically switched off. This is an example of functional safety. It is part of the overall safety of a system or device that depends on automatic safeguards put in place to respond to a potentially dangerous situation.

Machinery in an automotive factory
Machinery in an automotive factory

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 integration 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.”

Reinelt also points out that IEC 61508 primarily addresses large application sectors, such as the process industry, as well as sectors with high integrity requirements such as avionics, space and railways. “For these sectors, higher SILs such as SIL3 and SIL4 are required, whereas this is not often the case for machinery. Also, these industries are typically comprised of large companies, very often with entire departments dedicated to safety and reliability, while this is less prevalent in the machinery sector.”

The result, remarks Reinelt, “was not to make machinery less safe, but rather to make it acceptably safe for those who work in this domain and allow small and medium enterprises to efficiently work with the standard.”

Working together with ISO

Similar to IEC 62061, ISO has also published its standard for the design and implementation of safety-related control systems of machinery known as ISO 13849-1, which addresses non-electrical technologies. In an effort to align IEC 62061 and ISO 13849-1, Joint Working Group 14 has been set up between IEC TC 44 and ISO TC/199.

The new edition of IEC 62061 builds upon the work of this joint working group. According to Reinelt, “The second edition of IEC 62061 includes the outcome from JWG 14. What we have learned in this group has been applied to this edition of the standard.”

Consequently, 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. Regarding risk reduction, Reinelt notes, “The performance levels defined in ISO 13849 are now integrated into the safety-related control systems defined in IEC 62061.”

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.

Addressing cyber security

With the convergence of the OT and IT environments, security is increasingly becoming an important factor that can affect safety. Security addresses intentional harm in the digital environment but which can have a detrimental impact on the physical safety of machinery and those who operate it.

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.

Enabling safe, smart factories

Smart factories leverage new technologies that bring intelligence to the work floor. By automating processes, gathering, analyzing and generating data, smart factories can improve efficiencies, reduce costs and enhance flexibility. It is a technology-driven approach that integrates the physical and virtual environments.

IEC 62051 brings safety to this vision. It is expected to be used by machine manufacturers, system integrators as well as component manufacturers as they build safe and smart factories for the future.