How safe? You decide

Mark T. Hoske, Editor-in-Chief -- Control Engineering, 1/1/2006

Newer safety standards offer more flexibility. Does that make your figurative cup half empty or half full? Rather than following exact safe-design instructions, you can evaluate risks, assess probability of failures, see how they match, and determine the needed design-safety level for your machine or manufacturing process. Then, ensure everyone understands the equipment and safe procedures under all possible scenarios.

Talking to various industry experts and reviewing materials from a half-dozen industry conference sessions in recent months, I learned just enough about safety to be dangerous. If you want a blueprint for a safe design, then newer regulations may not satisfy. Gaining a working knowledge can take weeks of studying newer standards and an unmerciful number of cross-references. If you are creative, and like some flexibility, you may find it stimulating to apply new safety standards. If you're cynical, you also may think that new regulations are meant to sell more standards, providing ample work for consultants, trainers, system integrators, and software vendors in sorting it out. Knowledge of prior regulations can help in applying current safety standards—review regulations regularly, take a class, question those experts, and use their manuals and other tools.

Recently introduced, safety standard IEC-62061 helps with the design and validation of machine control systems that use PLCs or safety controllers for protection. Exida's Jon Keswick is teaching a related two-day course in February. He says, "Changes in standards are potentially difficult for people in the short term. Risk-based standards present a challenge to those who are more used to a prescriptive approach. Now people are required to think in greater detail about management, software, and the design of more complex, programmable systems." And the EN 954-1 standard, covering the design of non-complex safety related control systems under European machinery directive, is expected to be re-issued soon as ISO13849-1.

Integrating controls, hardware, and software with safety should be used as an opportunity to improve designs. Hazardous machine parts and their potential points of failure shouldn't be a conundrum, inside a mystery, wrapped in an enigma. Elegant, safe designs should ensure that the easiest way to do something is also the most economical and efficient. They should not encourage "work arounds," create production impediments, or contribute to accidents caused by complexity. Approach new safety regulations as blessing rather than a curse, and update me on your progress in safely filling (or manufacturing) the rest of your "half-full cup.

mhoske@reedbusiness.com