What is a process plant Safety Instrumented System (SIS)?
Any process loop identified as a safety system is referred to as a Safety Instrumented System (SIS). In the past, these loops were defined as Emergency Shutdown (ESD) or Safety Shutdown (SSD). The purpose of an SIS is to reduce the risk of an accident. SIS loops defined: “An SIS is a distinct, reliable system used to safeguard a process to prevent a catastrophic release of toxic, flammable, or explosive chemicals.” (Ref. ISA S84.01) SIS loop scope: “System composed of sensors, logic solvers, and final control elements for the purpose of taking a process to a safe state, when predetermined conditions are violated.” (Ref ISA S84.01 and IEC 61508) Thus, SIS is composed of the entire control loop. This loop will likely consists of pressure and temperature transmitters, Control Valves, DCS (or PLC and SLC), plumbing, wiring, power supplies, and other loop equipment.
Related Questions
- Describe the process of how an intervention is selected, including: what are the carrier Safety Measurement System (SMS) thresholds that trigger the interventions?
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