Global machine safety following IEC/ISO 17305

• By Derek Jones
• Factory Automation

Summary

Standards delayed, but expect changes to global machine safety in coming years

By Derek Jones

A single global machine safety standard has been in the works for a long time and will now be a little longer. The merger of safety standards ISO 13849 and IEC 62061 into one standard, IEC/ISO 17305, was scheduled to take effect in 2017. However, the project was canceled based on decisions made at the October 2015 plenary meeting of ISO technical committee ISO/TC 199.

The committee simply could not reconcile the differences between the ISO and IEC standards by its deadline. As a result, IEC/ISO 17305 is stopped, and its future will not be known until after the next IEC/TC 44 and ISO/TC 199 plenary meetings in March 2017. Despite the setback of the proposed merger, machine designers can still expect to see changes to global machine safety standards in the coming years.

Evolution of machine safety standards

Any eventual reimplementation of the IEC/ISO 17305 merger would be another step forward in the evolution of safety standards. But even without the merger process, the evolution will continue in the form of further updates and continued convergence of ISO 13849 and IEC 62061. These two standards have many similarities, but also distinctions.

ISO 13849 is primarily used for conventional machines, including those for discrete production where only a simple, self-contained design and validation methodology is required. IEC 62061 is typically used for more complicated machines that require more complex safety functions, such as those used in process applications.

The transition to these two standards was a significant leap for many machine designers. Switching from simple machine safety categories to performance level (PL) and safety integrity level (SIL) models brought greater complexity. It also caused confusion about when SIL-qualified components can be used in PL-qualified systems, or vice versa, and created training demands to ensure engineers understand both standards.

At the same time, the value that these two standards have brought to safety compliance is undeniable. The standards' support of new, programmable safety technologies helps end users meet safety requirements while also enhancing productivity. The two standards are also a simplified way to achieve safety compliance in markets around the world.

One company capitalizing on IEC 62061 and ISO 13849 is Wisconsin-based Paper Converting Machine Company (PCMC), a leader in tissue converting, packaging, flexographic printing, and nonwoven technology. It is using the standards to make safety an integral part of its design process and equipment upgrades.

It's really a change in philosophy,- said Jill Thiede, strategic accounts manager for PCMC. Now, we can design an integrated safety system that reduces machine hazards and associated risks-and improves overall efficiency and productivity.

PCMC now uses the standards to implement contemporary safety technologies. For example, it can use zone control to divide a complex converting line into safety zones that correspond to specific risks or hazards. The system can be configured to safely remove power from one zone so a maintenance technician can service it, while keeping the rest of the line running.

Preparing for changes

If IEC/ISO 17305 ever does come to pass, it will likely encounter some resistance like any standard change does. However, machine designers should find that their migration to and understanding of current IEC 62061 and ISO 13849 standards will make future migration more manageable.

Those concerned with understanding the relationship between the two standards and potential areas of convergence can start by studying the ISO TR 23849 or IEC/TR 62061-1 technical reports. They have helpful interpretations of each standard and offer guidance on specific applications.

As far as potential changes for ISO 13849, machine designers may get some relief from the quantification burdens required for more simple and deterministic systems. IEC 62061 may include additions that address new factors, such as low-demand safety applications, to cover a wider range of machinery.

Even as these changes are made, the basic requirements of the standards will stay the same. That is why it is important to commit to understanding and making the most of the current standards. This is especially true for safety professionals who are responsible for maintaining their organizations' corporate safety standards.

Is there any value for users and machine builders to make changes today, since the safety standards ISO 13849 and IEC 62061 have not yet been merged in one standard? Yes, ISO 13849 and IEC 62061 are currently the most stringent and encompassing international safety standards. Building machinery to comply with these standards helps to ensure it will meet regional requirements no matter where a plant is located. Many large, international end users are standardizing their machinery to meet ISO 13849 and IEC 62061 across all locations. Regardless of whether the two standards are merged into one, machine builders wanting to serve these end users need to meet these two standards. In addition, the European Commission requires that any machine shipped into or out of the European Union meets ISO 13849 or IEC 62061. ISO 13849 and IEC 62061 also allow the use of contemporary safety technologies and add more flexibility in safety system design. For example, zone control allows users to divide a complex converting line into safety zones that correspond to specific risks or hazards. A system can be configured to safely remove power from one zone so a maintenance technician can service it, while keeping the rest of the line up and running.

What changes in engineering and design should users and machine builders make, if any? When adopting these standards, designers need to assess the reliability of a safety system in relationship to time. Each component must have an assigned probability of dangerous failure or mean time to dangerous failure. Although this means more steps and procedures, it also helps instill confidence that the safety system will perform properly today and tomorrow. In the long run, the time element should result in less pain for machine operators and safety system designers due to the ability to quantify circuit reliability through specific performance and system integrity calculations. Being able to define performance requirements gives designers more flexibility to tailor their circuits to the specific needs of the application, rather than generalizing the overall design based on the simpler\, more prescriptive requirements of the past.

Those who commit to understanding existing standards will be better prepared to develop higher-performing and internationally competitive machinery, while also containing the costs of multinational safety compliance. They will also be better positioned in the future to migrate to revised standards-and eventually to a potential single converged standard, if it happens.

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