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Machine guarding and economic value: Wired safety versus safety automation
October 31, 2011
Machine safety has experience probably the greatest transformation over the past 10 years since the advent of machine control technology. In my opinion, the recent adoption of “safety automation” has outpaced the original adoption of PLC technology in the early 1970s. It was in the early 1970s that machine safety was mandated by industry standards to be “hard wired.” At this time PLC technology had just been introduced and its reliability paled in contrast to the robust PLC reliability of today. Just take a quick glance at the conceptual graph illustrated below.
I experienced the introduction of automation technology lead by PLCs as a young engineer in an automotive plant. After a slow start, automation technology took off like a rocket experiencing wide spread adoption and application to machine control. The advantages of diagnostics reduced wiring, increased machine up-time, reduced panel space, easier trouble shooting, etc. drove acceptance as research and development drove technological improvements and inherent reliability. At the same time, however, machine safety was required to be hard wired and could not enjoy these advantages or technological improvements.
In my opinion, this created a safety layer in the machine control architecture interfacing the safety related electromechanical components to the machine control automation technology. The unintended consequences resulted in a rather stagnant level of technology innovation for the safety layer in comparison to the automation technology. This gap of technology helped drive a new metric called “unplanned downtime.” Plant operation personnel became used to the diagnostics and other advantages of the automation technology and conversely became frustrated by the lack of diagnostics, intermittent downtimes, and other disadvantages of the safety layer. Thusly, many of us experienced occasions where “quick fixes” were made to get machines back into production to meet schedule demands.
To make a long story short, folks in my era have experienced the changing landscape of machine control to once again see the unified machine control architecture of “integrated automation with safety” in innovative technology. Machine safety can once again be designed in vs an after-thought. Of course, direct wiring of safety components is still a viable option. However, for larger more complicated machines integrated safety is now available. Most importantly the economic values of increased productivity can drive increased profits which in turn can provide a competitive advantage.
What experiences have you had along this changing landscape evolution?
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For more than 30 years, J.B. Titus has advised a wide range of clients on machine functional safety solutions, including Johnson + Johnson, Siemens, General Motors, Disney, Rockwell Automation, Bridgestone Firestone, and Samsung Heavy Industries. He holds a Bachelor of Business Administration degree from Oklahoma University in industrial management and an MBA from Case Western Reserve University in marketing and finance. He is a professional member of the American Society of Safety Engineers and is OSHA-certified in machine guarding. Titus is also TUV-certified as a Functional Safety Expert and serves on several American National Standards Institute, National Fire Protection Association, and National Electrical Manufacturers Association national safety and health standards committees. Reach him at jb(at)jbtitus.com and via www.jbtitus.com.
Thursday, 24-11-11 02:10
Being of a generation when PLCs were first conceptualized, the use of "hardwiring" for the "safety layer" is where I learned my trade and skills as a troubleshooter. This is my comfort zone.
But I have been involved in and tried to keep pace with the evolution from "hard wiring" to the modern concepts of today's safety systems based upon microprocessor, data transfer, and no cable (wireless) intergration.
What is of growing concern is when young tradepersons and engineers do not have access to diagnostics via electronic medium but have to revert to old schematics and use of analog or DVM meters that there is a perceptible lack of understanding of basics.
Look, feel, smell, listen are still pertinent.