Machine Safety: Easy to Love, Hard to Understand

U.S. Safety Standards Continue to Be an Obscure Issue

By Joe Feeley

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As Control Design celebrates its 15th anniversary, we bring you a look back at some of the topics we have covered and that have generated the most discussion among our machine builder and integrator audience. This article is part of our June 2012 cover story, "We Celebrate 15 Years."


Just as building machines for a global market has been something of an adventure, the evolution of machine safety has been an exciting, often confusing, period.

Here again, competing in the global economy meant better understanding of regional differences—safety standards in particular. But even in the U.S., standards were a thorny issue.

At What Cost, Safety?
In the January 2008 issue ("Why Is Safety Information So Pricey?"), Scott Gee, chief software architect at ISDTech, Canyon Country, Calif., lamented in the OEM Insight guest column, "Engineers are bombarded with mantras of Safety Compliance and Standards Conformity. If you are not following the latest safety decrees, you could jeopardize your company's ability to do business, not to mention liabilities you could incur. But no one wants to recognize a question of 'How much is this going to cost me?' I'm not referring to the costs of implementing these processes and procedures; rather, it's about the cost just to even learn the information in these standards."

Gee had replaced an old extrusion press controller system with a new PLC. The local inspector's report frequently referred to UL508 and UL508A as the authority for items that needed to be fixed.

"I asked the inspector if I could get more than just a reference number to this standard," Scott continued. "He politely chuckled. He wasn't trying to embarrass me, but he clearly was amused by my request. He said I would have to find and purchase these standards for myself. I did a web search for these standards and quickly understood the inspector's reaction. The least expensive price I was quoted for UL508 and UL508A was about $450 a piece, and other places wanted as much as $600 each."

When he finished reading them, Gee had one thought: "'Why am I paying so much for these documents?' There were about two dozen pages between both of these documents that actually pertained to my specific situation. I paid $900 to find the reference for not affixing the proper signage?"

Scott concluded by writing, "I have two issues with what happened to me and probably to countless other engineers trying to do the right thing. First, a significant amount of these standards don't contain information relevant to a particular application. Second, standards companies still charge as if you were getting an actual book, but they are delivering PDF files. It's fair for a company to recoup its research investment costs, but hasn't UL been able to amortize their initial costs for the 17th edition of a safety standards book over the decades since the first edition appeared? Spare me the, 'We have to charge that much because of continuing research' argument. The physics of electrical panel safety does not change every year or two."

Safe by Design
In our May 2008 cover story, "Proceed With Caution," we learned that many designers believe that most machines are initially safe but don't stay that way because of improper operation or end user modifications. "Most accidents occur due to lack of end user training or from purposeful bypassing or defeating of the safeties and alarms supplied by the manufacturer of the machine or robot," said Eric Wolfgang, who was then the quality assurance and safety standards manager at Engel Machinery, York, Pa. Engel makes horizontal and vertical injection molding machines and the robots and associated automation used with them.

"Injury was minimal, but the situation is frightening. The incident would have been prevented had the programmer not defeated the safety circuit and entered the safety enclosure while the robots were running."

Abstract discussions of safety are important, but nothing brings safety to life like a recounting of actual unsafe practices or machine accidents. "The most serious accident I know of occurred when one of my fellow programmers was pinned against a wall by a robot that he programmed at the customer site," said Shahvar Pirouznia, engineering manager and founder of Balance Automation Solutions, Longmont, Colo. "This was completely his fault as he attempted to fix a problem while the system was running. It was the wrong decision."

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