Machine safety faces paradigm shift

Time’s running out: How will your company embrace the new international standard?
September 23, 2011

Like it or not, many—perhaps most—U.S. companies will be embracing a new international standard for machine safety come the first of the year. For all intents and purposes, adopting EN ISO 13849-1:2008 is virtually unavoidable. This new quantitative-based approach to machine safety will undoubtedly impact U.S. industry in significant and various ways. With the compliance deadline of January 1, 2012 looming large, a closer look at how this new standard will roll out and the impact it will have on U.S. manufacturing seems in order.

When asked for his perspective on this landmark regulation, machine safety expert and consultant J.B. Titus said that for him two views prevail: a professorial one and a practical one. The first view involves training and educating everyone in industry about compliance requirements and possible business advantages. The second addresses each segment of the standard as needed to develop tailored adoption methodologies.

“The professorial view,” said Titus, “makes no attempt to segregate the market based on size of company, personnel competence, OEM versus end user, and other key market segments. Does adoption mean the same thing to a Fortune 500 company as it does to a small independent manufacturer with less than 50 employees? Probably not!”

What’s a small manufacturer to do?

So how, then, does the small, independent U.S. machinery manufacturer approach the adoption of ISO 13849-1:2008?

First, look at the roots of this international consensus standard. It was driven largely by the European community and is now part of the European Machinery Directive, the body of legislation governing industry in Europe. Its listing by the Directive brings this consensus standard under the Directive. Therefore, compliance is enforced via legal regulation in Europe. In the U. S., this international consensus standard will likely be enforced through a “best practices” approach, a company’s safety culture, and, regrettably on occasion, litigation.

According to the scope statement of 13849-1:2008, the standard “provides safety requirements and guidance on the principles for the design and integration of the safety-related parts of control systems (SRP/CS).” This standard launches various new compliance requirements, including the design of software. For the SRP/CS, it specifies characteristics that include the performance level required for carrying out safety functions. It also applies to the SRP/CS, regardless of the type of technology and energy used (electrical, hydraulic, pneumatic, mechanical, etc.) for all kinds of machinery.

From a practical standpoint, the small manufacturer typically may not have the staff to meet the additional compliance requirements of ISO 13849-1:2008. Where then will a small company operating on a thin margin get the needed competencies for compliance, asked Titus? “Small companies don’t usually do a complete control system retrofit,” he continued. “Who will evaluate the complete safety circuit (motor, contactor, logic controller, actuator, interlock switch, for example) as required by 13849-1? The performance level must be determined for the safety circuit even though only a new contactor has been installed, and each component in the circuit conceivably will contain a mixture (for instance, none, SIL, Cat, PL, and the like) of device safety ratings.”

And what about the end user?

Also starting on January 1, 2012, the European Machinery Directive will no longer allow the use of EN 954-1 1996 to demonstrate conformity. Over the last 15 years, EN 954-1 successfully helped OEMs, systems integrators, and end users understand hazard categories and the importance of mitigating hazards to acceptable levels and improving overall safety. During that time, automation suppliers introduced many new products designed, tested, and certified for safety applications—a number of them hardware- and software-based offerings that carry complicated new sources of possible failure and potential hazards.

“This transition in innovation for safety technology,” said Titus, “in large part has driven the need for a quantitative approach to evaluate the performance level of safety circuits and to include the evaluation of software—specifically the level of diagnostics in the software.” OEM system designers and integrators using EN ISO 13849-1:2008 and its quantitative analysis of safety circuits to determine the performance levels to achieve required safety functions during the design phase, he went on, will now have the flexibility to modify a design to meet the acceptable hazard levels determined in the risk assessment. The transition for the end user, however, is a bit different. “Under the qualitative approach of EN 954-1,” said Titus, “the OEM, systems integrator, and end user all likely had the competencies to demonstrate conformance. But under 13849-1, end users may not have them. In one recent survey, nearly 40% of the respondents said they needed outside help or tools to meet the compliance requirements of the new standard. Another 42% said maybe they will need them, or that they were unsure!”

A challenge for some, benefits for all

So just how ready are U.S. companies to adopt and comply with this standard? The study to which Titus refers was conducted last spring by CFE Media’s Control Engineering. The Webex survey, which focused on the adoption of EN ISO 13849-1:2008 and EN/IEC 62061 (functional safety), showed 81% of respondents expected to comply with these standards by the end of 2011. However, more than 80% (as noted above) also indicated they would need tools or outside assistance to meet this goal. Informal surveys of trade show attendees had only 10% of those queried expecting to comply with these standards by the end of this year. Although certainly not scientific, these studies do show that companies are aware of the revised and updated standards and their requirements; that industry recognizes the approaching effective date; and that most companies feel a need to comply with the requirements.

Because the U.S. is part of the International Standards Organization (ISO), most U.S. companies are adopting ISO EN 13849-1:2008. Many will have to if they expect to continue to do business globally. But beyond a compulsion to comply, Titus believes the new standard simply improves machine safety because it moves compliance from qualitative categories to quantitative performance levels.

Although compliance with the new standard promises improved safety and possibly better machine performance, efficiency, and plant productivity, the reality is that some companies are finding it hard to meet its requirements by the end of this year. Those struggling with the standard should recognize that help is available; that a number of companies, organizations, and consulting firms offer classes on the new standard; and that answers may be as close as enrolling in a class or two.

The specifics of EN ISO 13849-1:2008 can be debated infinitely. However, it seems apparent that machine safety will be going through a paradigm shift over the next several months— perhaps years—as SIL (safety integrity level) and Cat (Category) parameters are phased out and SIL and PL (Performance Level) become the new basis for machine guarding and hazard mitigation. It also seems without question that when all is said and done, machine safety overall will benefit.

J.B. Titus, CFSE, is president of J.B. Titus and Associates, Solutions for Machine Safety, Duluth, GA. Contact him at or visit the website at

J.B Titus continues to address the dynamic issues of EN ISO 13849-1:2008 in his machine safety blog. Stay up-to-date on what’s happening with this international consensus standard, and with machine safety in general, by following the discussion on the Control Engineering website at For those seeking assistance with compliance and a better understanding of the new standards, help is available from a number of manufacturers. Siemens, for example, offers a free, TÜV-certified Safety Evaluation Tool to assist customers in checking their safety designs to determine compliance with SIL or PL requirements. For more information on this tool and other Siemens safety automation related products, visit the Siemens Industry website at

Another resource offered at no charge is the SISTEMA (Safety Integrity Software Tool for the Evaluation of Machine Applications) Software PL Calculation Tool developed by the German Institute for Occupational Safety and Health to simplify implementation of EN ISO 13849-1:2008. It allows functional safety data to be input manually or automatically using a manufacturer’s SISTEMA data library. For more information, go to

This article was submitted for the custom newsletter, Siemens Simplified Safety. See other articles in the Siemens Simplified Safety newsletter.