Process safety is a major concern to anyone who works in a process facility. An estimated 25,000 facilities covered by the Occupational Safety and Health Administration (OSHA) Process Safety Management of Highly Hazardous Chemicals regulation will most likely have safety instrumented systems (SIS), also known as emergency shutdown systems.
Throughout the decades, process industries have used different forms of safety based on what was available in the market. Relays have been used in safety applications since the 1930s. Solid-state systems, that do not use software, were developed to replace relays and have been used in safety applications since the 1970s. Programmable Logic Controllers (PLCs) that do use software, were developed to replace relays and have also been used in safety applications since the 1970s.
Guidelines and standards for the design and implementation of safety systems have been in place in a variety of industries since the 1990s. Many things change, even standards. Yet many other things do not change – or change very little – such as industrial processes that have been running for decades. So what are people expected to do with safety systems installed prior to current standards? Are previous designs automatically assumed to be acceptable, or must all older systems be ripped out and replaced? This is one topic that has its fair share of misinformation and scare tactics, and what will be explored in this white paper.