High Integrity Protection 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

High Integrity Protection System


Non-conventional autonomous safety instrumented system with sufficiently high safety integrity (see

3.2.1) to protect equipment against exceeding the design parameters

  • Note: 1 to entry: Deviations from industry standards describing mechanical protection systems (e.g. ISO 23251[31] = API

STD 521[32], ISO 10418[33], API RP 14C[58]) are treated as HIPS. An ultimate protection relying solely on Safety

Instrumented Systems (SIS) is qualified as HIPS, irrespective of its required Safety Integrity Level (SIL).

Source: ISO/TR 12489:2013(E) Reliability modelling and calculation of safety systems. Global Standards

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