Machine safety compliance

Inside Machines: Does adopting ISO 13849-1:2006 change the U.S. model for compliance and enforcement?


Industrial machine safety standards have been harmonizing over the past 10 to 15 years with greater interest, activity, collaboration, and results from participating countries globally. Standards technical committees are working together to create international standards that meet the needs of global and regional markets and individual countries. This seems to be driven by global companies, economic and competitive issues, and a world economy. Countries still have domestic standards, but even they are trending to reference the international standards more often, such as those from IEC (International Electrotechnical Commission) and ISO (International Organization for Standardization).

Flowchart on left shows the relatively straightforward European legal model for enforcement. On the right, the U.S. model is less straightforward. Courtesy: JB Titus & Associates

As international standards become more prominent, there are additional U.S. issues to consider.

Manufacturers at safety seminars express concern about lack of training materials related to the U.S. model for machine safety compliance and enforcement.

Historically, international standards (IEC & ISO) have been strongly influenced by the European countries; each member country (including Canada and U.S.) has a vote. This could explain, in part, why ISO standards (like ISO 13849-1:2006 Safety of machinery – Safety-related parts of control systems – Part 1: General principles for design) are largely written for suppliers, not users, of machinery. Conversely, U.S. consensus standards for machine safety tend to be written equally for users and suppliers, especially as it relates to the design, construction, and long-term ownership of machinery. Therefore, we’ve seen a U.S. shift toward additional compliance requirements.

Enforcement (Law)

Enforcement most often is analogous to the term “law.” The U.S. legal model for enforcement is not very straightforward compared to the European compliance model, as the chart shows.  

In each model, the U.S. Occupational Safety & Health Administration (OSHA) and the European Machinery Directive are the “Law.”

Since the Machinery Directive lists the standards, a single flow with dual purpose is achieved, driving compliance and enforcement to the supplier. These listed standards are regularly updated and must be re-approved under the Machinery Directive. However, OSHA uses a list of “regulations” created in the early 1970s for enforcement. OSHA, the “Law,” cites these “regulations” and openly enforces compliance to the end user of machinery and not the supplier. Furthermore, OSHA reserves the “right to reference” consensus standards for enforcement to the end user.

 Many believe that this practice confuses U.S. compliance because OSHA doesn’t openly require (with the force of “Law”) that a supplier build a compliant machine. Many also believe that most suppliers do build compliant machines because:

- End users pass through machine safety compliance requirements in the purchase order.

- Suppliers understand their liability.

- Suppliers apply due diligence and want to provide safe machines to users.

Compared to Europe, OSHA sees U.S. enforcement in the “rearview mirror,” especially as users begin to seriously examine the latest ISO 13849-1 and its mathematical requirements for calculating the performance level (PL) of a safety circuit with multiple components. As the requirements of ISO 13849-1 become more broadly adopted, those at many small- to medium-sized user organizations believe they’ll need help from suppliers to perform these calculations, particularly on legacy equipment, to maintain compliance. Suppliers typically have the resources and skills indirectly required by the standard.

How the U.S. adopts requirements of an international standard, like ISO 13849-1, is critically important, since OSHA puts the U.S. user first in line for enforcement. Users must consider the business impacts of these changes.

The U.S. model requires that we acknowledge our compliance and enforcement flow with appropriate measures as we consider adopting international machine safety standards. 

- J.B. Titus, Certified Functional Safety Expert (CFSE), writes the Control Engineering Machine Safety Blog. Reach him at jb(at); Edited by Mark T. Hoske, content manager CFE Media, Control Engineering and Plant Engineering, mhoske(at)

ONLINE extras

Machine Safety Blog

Machine Safety – functional safety and the steps to be compliant in the U.S.

Machinery Directive in 4 days drops EN 954 and EN ISO 13849-1 is fully in force – What’s your impact?

Is OSHA rearview mirror enforcement?

Cover Story: Machine Safety Integration (Survey shows lack of Machinery Directive preparedness.)

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