Machine safety: NRTL certified convergence of machine control and the safety-related parts combined

Does a Nationally Recognized Testing Laboratory (NTRL) certify machine control systems? OSHA has identified 15 organizations qualified to test and certify products for use in safety applications for the U.S. work force. There's a link between machine safety and productivity.


So what the devil is a NRTL, and does it actually certify machine control systems? How does it impact our business? NRTL (Nationally Recognized Testing Laboratory) is a term established by OSHA that identifies 15 organizations qualified to test and certify products for use in safety applications for the U.S. work force.


Machine control technology landscape and machine safety have changed significantly since 1970. J.B. Titus & Associates, CFE Media used with permissionThe background I have witnessed is captured in the graph shown. OSHA was created by an act of Congress in 1971. Within approximately 18 months programmable logic controllers (PLCs also called “automatic sequencers”) were introduced to manufacturing for machine control. At the beginning of their life, PLCs were highly unreliable. Thus, the brand-new OSHA regulations and established safety standards quickly wrote normative language requiring everything safety to be hard wired. In my opinion, these divergent approaches caused a layering effect in a machine’s control architecture. 

PLCs quickly evolved through the 1970s, 1980s, and 1990s with rapid increases in reliability, advances in technology, and adoption throughout manufacturing. The divergence in technology of general automation and hard wired safety on a machine’s architecture resulted in huge amounts of unplanned machine downtime. One piece of collateral damage related to this phenomenon was that after finding the failed safety device someone would jumper that device out of operation. After some lengthy unplanned machine downtime, production was ultimately restored but safety was de-activated.

Continuing in 2002, NRTL certified safety PLCs were introduced to U.S. manufacturing. A new “option” for safety compliance became available called safety automation. In the last 12 years safety automation also has evolved following the general automation trend line discussed above. These technological advancements have allowed safety automation and general automation to converge into one platform. Hardwiring everything for safety is no longer the only option. When it makes sense in an application, safety automation is also an acceptable option for safety compliance. 

In my opinion, a business case analysis approach is available for manufacturers in considering the total cost of ownership for a layered versus integrated machine control architecture. For example, the cost of unplanned machine downtime typically goes directly to the bottom line. Therefore, reducing unplanned machine downtime by as little as 4% can generate huge incremental profits. A recent Aberdeen Group study shows a direct link between machine safety and productivity.   

Is a converged solution your best choice? 

Has this presented you with any new perspectives? Add your comments or thoughts to the discussion by submitting your ideas, experiences, and challenges in the comments section below.

J.B. Titus, CFSE

Related articles:

OSHA – NRTL (Nationally Recognized Testing Laboratory)

Machine Safety: Managing operational risk

Aberdeen Group - “Operational Risk Management”, November 2012 

Contact: for “Solutions for Machine Safety”.

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