Safety Instrumented System (SIS).

An independent control system that brings a process to a safe state when monitored variables exceed defined limits, protecting people, environment, and assets. It belongs to the OT / ICS / IoT category of cybersecurity.

An independent control system that brings a process to a safe state when monitored variables exceed defined limits, protecting people, environment, and assets.

A Safety Instrumented System (SIS) is a dedicated, certified control system whose only job is to detect dangerous process conditions and automatically take the plant to a safe state — typically by closing valves, tripping motors, or venting pressure. It is engineered, segregated, and certified to functional-safety standards such as IEC 61508 and IEC 61511, with a required Safety Integrity Level (SIL) derived from a hazard and operability study. Common products include Triconex, Honeywell Safety Manager, Siemens S7-1500F, and Yokogawa ProSafe-RS. SIS must be logically and physically separated from the basic process control system (BPCS); the TRITON attack on a Triconex SIS in 2017 demonstrated the catastrophic potential when this separation fails.

Defences for Safety Instrumented System (SIS) typically combine technical controls and operational practices, as detailed in the full definition above.

Common alternative names include: SIS, Emergency Shutdown System (ESD), Safety system.