Bring up the topic of Safety Instrumented Systems in any industrial forum and you will get a spectrum of responses that could range from "fear and mistrust", to "not my job, don't need to know" to "deer in the headlights"
It seems that many of the folks in the Instrumentation and Controls field may be among those who do not understand the role of the safety instrumented system. This month's issue of Intech magazine which is published by the ISA (international society of automation) featured two such articles. Both articles were very good and informative, and offered links to register for upcoming training sessions.
So the question really becomes how well do people outside of the Instrumentation and Controls world understand safety instrumented systems? How well do those people need to understand the role of safety instrumented systems? The answer to both of those questions depends entirely on perspective. Operationally there is often little thought given to safety instrumented systems until they fail, or require maintenance. This has led to a misconception that safety instrumented systems, should only be thought about when they fail or require maintenance. Consequently those same systems are not upgraded or updated as easily or regularly as they would be if they were basic process control systems.
The mere thought of upgrading a safety instrumented system can strike fear, in the hearts of even the steeliest of Maintenance and Operations Managers. "Why is this needed?" is the question most often asked. "Obsolescence" is the most common answer. In most cases neither the Maintenance nor Operations Manager had any idea that the safety instrumented systems in their facility were more than twenty years old, and as such had reached the end of useful life. What is more common is that these systems fail outright, causing a spurious trip. The instrumentation and controls department is now left with the task of repairing a system for which parts may or may not be available.
Safety and Reliability or Reliability and Safety, these two concepts fit "hand-in-glove" and yet we continue to see organizations who perform the periodic proof testing without giving much thought to other primary reliability concepts, such as end of life replacement, or performance review. The primary reason is that modifying the safety instrumented systems invokes a review and revision of the performance calculations (safety integrity level validation) and safety requirements specification, which in many cases means bringing in a consultant to conduct those reviews, and update or create the required documentation.
Wouldn't it be easier to manage all of that paperwork and documentation ourselves, and do all of that in one place? Planning for end of life replacement could be done proactively allowing the engineering group to select the most applicable and best suited components. This way technological advances would trickle down to the safety instrumented systems at the same rate as they do for the basic process control systems. Beyond the cost efficiencies associated with proactive lifecycle management this would allow people to better understand not only the role of the safety instrumented system, but also their own role as "steward" of pro-active safety lifecycle management.
