safety instrumented system (SIL) (SIS)

A Safety Instrumented System (SIS) is a safety system that contains at least one component that performs the function electrically, electronically or programmably electronically, E/E/ PE, and one or more safety functions.

SIS systems typically consist of three functional areas: the sensors, such as the pressure transducers; the logic unit, such as a programmable logic controller( PLC) with the control and monitoring equipment; and the actuators, such as the valves, to be controlled.

The safety functions performed by SIS systems, the Safety Instrumented Functions( SIF), reduce the risks that occur below the acceptance criteria.