Safety Instrumented System

Definition(s)


Safety Instrumented System

System composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are met.

  • NOTE Other terms commonly used for a SIS include emergency shutdown system (ESD, ESS), safety shutdown system (SSD), and safety interlock system (see E.3.3.1).

Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards

Safety Instrumented System

ISA S84.01 defines a safety instrumented system as a “system composed of sensors, logic solvers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are violated. Other terms commonly used include emergency shutdown system (ESD, ESS), safety shutdown system (SSD), and safety interlock system.” HIPS also fit the definition of a safety instrumented system.

Source: API STD 521, Pressure-relieving and Depressuring Systems, Fifth Edition, January 2007 (Addendum May 2008). Global Standards

 

Safety Instrumented System

System used to implement one or more safety-instrumented functions [2].

  • Note: A safety-instrumented system is composed of any combination of sensor(s), logic solver(s), and actuator(s).

Source: ANSI/ISA–99.00.01–2007, Security for Industrial Automation and Control Systems, Part 1: Terminology, Concepts, and Models, 29 October 2007. National Standard