Safety Instrumented Systems

Standardization Reigns in Automation Safety

Our First 25 Years Have Seen Arcane Systems Evolve into a Highly Standardized and Tightly Regulated Discipline

By Paul Studebaker

Safety is a big topic, involving not only instrumentation and control, but equipment design and maintenance, hazardous areas, personnel training and protection, security and in recent times, cybersecurity. Control's inaugural issue in October 1988 included features on fault-tolerant control systems and the role of instrumentation in process safety. These and other articles in our early years laid the groundwork for extensive coverage of safety system technology and applications.

Many would trace a rise in attention to safety systems back to the Bhopal incident in 1984, which led to amendments of the Clear Air Act of 1990 requiring OSHA and the EPA to enact regulations dealing with chemical plant process and environmental safety.

In 1992, OSHA enacted 29 CFR Part 1910.119, "Process Safety Management of Highly Hazardous Chemicals," commonly known as Process Safety Management (PSM). OSHA's PSM preamble says, "Recent major incidents include the 1984 Bhopal incident, resulting in more than 2,000 deaths; the October 1989 Phillips 66 Chemical Plant incident resulting in 24 deaths and 132 injuries; the July 1990 Arco Chemical incident resulting in 17 deaths; the July 1990 BASF incident resulting in two deaths and 41 injuries; and the May 1991 IMC incident resulting in eight deaths and 128 injuries." In 1996, the EPA enacted 40 CFR Part 68, "Risk Management Program" regulations, extending PSM to further protect the environment.

The evolution of safety system technology is chronicled in the accompanying timeline. Over the years, Control discussed and debated to a standstill questions about the suitability of microprocessors, the need for separate and independent systems, the importance of diversity, the virtues of specialized field devices, the effectiveness of intrinsic safety as an alternative to explosion-proof or purged systems, and more recently, reliability's role, wireless and cybersecurity.

"One of OSHA 1910.119 PSM regulation's 14 elements is mechanical integrity—to ensure that critical process equipment is designed, installed correctly and operates properly, which sounds like reliability is probably in there somewhere," we wrote in April, "but you will probably not find a reliability engineer on the PSM staff nor a PSM engineer on the maintenance staff."

The issue with using wireless for critical control and safety primarily comes down to the wireless channel reliability and what occurs if it is unreliable, we said in July. Wireless design and installation, hardware and support issues are more complex and sophisticated, which can have a significant effect on the reliability.

Despite our assiduous efforts to define safety as an engineering and technology problem, its Achilles' heel remains in the wetware: people are not only unreliable, they're also creative, unpredictable and occasionally malevolent. That and the fact that cybersecurity often generates attention-getting headlines have raised it as the great unresolved safety issue of the 21st century. We'll continue to follow that story, as well as the less exciting, but equally important developments in safety system hardware and software, over our next 25 years.

View the Process Control Safety Timeline