Functional safety - Safety instrumented systems for the process industry sector - Part 1: Framework, definitions, system, hardware and application programming requirements

2Scope / Description

IEC 61511 Part 1 provides the requirements for the specification, design, installation, operation, and maintenance of safety instrumented systems (SIS), enabling them to be confidently entrusted with achieving or maintaining a controlled state of process. IEC 61511-1 was developed as a specific implementation of IEC 61508:2010 in the process industry. In particular, IEC 61511-1: a) specifies the requirements for achieving functional safety, but does not specify who is responsible for implementing these requirements (e.g., designer, supplier, owner/operating company, contractor); b) applies to the integration of devices conforming to the IEC 61508 series (2010 edition) or IEC 61511-1:2016 requirements into overall systems used in process industry applications; c) defines the relationship between IEC 61511 and IEC 61508; d) applies to the development of applications for systems with limited variability languages or when using devices with fixed programming languages, but not to the development of embedded software (system software) or the use of fully variable languages by manufacturers, SIS designers, integrators, and users; e) applies to various industries within the process industry, such as chemical, oil and gas, pulp and paper, pharmaceutical, food and beverage, and non-nuclear power generation; f) outlines the relationship between safety instrumented functions (SIFs) and other instrumented functions; g) identifies SIFs after considering the risk reduction of implementation by other methods. The document outlines the functional and safety integrity requirements of the SIS system. It includes: h) System architecture and hardware configuration, application programming, and system integration lifecycle requirements; i) Application programming requirements for SIS users and integrators; j) Applicable when using one or more SIFs to achieve functional safety to protect people, the public, or the environment; k) Applicable to non-safety applications, such as asset protection; l) Requirements for implementing the SIF as part of a holistic arrangement for achieving functional safety; m) Using the SIS safety lifecycle (see Figure 7) and defining a series of necessary activities to determine the functional and safety integrity requirements of the SIS; n) Requirement to conduct a Hazard and Risk Assessment (H&RA) to define the safety functional requirements and Safety Integrity Level (SIL) for each SIF; o) Target values for the Probability of Requested Failure (PFDavg) and the Average Frequency of Hazardous Failures (PFLAG) for each SIL; p) Minimum requirements for Hardware Fault Tolerance (HFT); q) Measures and techniques required to achieve the specified SIL; and r) The highest functional safety performance level (SIL) achievable by an SIF implemented according to IEC 61511-1. 4) s) Defines the minimum functional safety performance level (SIL 1) below which IEC 61511-1 is not applicable; t) Provides a framework for establishing SIL, but does not specify the SIL required for specific applications (it should be determined based on the understanding of the specific application and the overall risk reduction objective); u) Specifies the requirements for all parts of the SIS from sensors to end components; v) Defines the information needed throughout the SIS safety lifecycle; w) Specifies that the design of the SIS should take human factors into account; x) Does not directly impose requirements on individual operators or maintenance personnel. ...