The IEC 61131 standard, specifically Part 6, addresses functional safety in programmable controllers, outlining requirements and guidelines for ensuring the safety of automated systems. This standard, titled "Programmable Controllers – Part 6: Functional Safety," provides a framework for the development, implementation, and verification of safety-related functions within programmable controllers.
Functional safety in programmable controllers is essential to prevent accidents, injuries, and damage to equipment in industrial environments. It involves identifying and mitigating risks associated with the operation of automated systems, such as those found in manufacturing, process control, and machinery applications.
IEC 61131-6 defines various safety-related concepts and terms, establishes safety integrity levels (SILs), and outlines the principles of safety lifecycle management. It also provides guidance on the design, programming, testing, and maintenance of safety-related functions in programmable controllers.
Key elements of the standard include:
Safety Integrity Levels (SILs): SILs are assigned to safety functions based on the level of risk reduction they provide. The standard defines four SIL levels (SIL 1 to SIL 4), with SIL 4 representing the highest level of safety integrity.
Safety Requirements Specification: This document specifies the safety functions, performance requirements, and validation criteria for the programmable controller's safety-related functions.
Safety Lifecycle Management: The standard outlines the safety lifecycle stages, including concept, design, implementation, validation, operation, and maintenance. It emphasizes the importance of systematic planning, documentation, and verification throughout the lifecycle to ensure the integrity of safety functions.
Programming Guidelines: IEC 61131-6 provides recommendations for programming safety-related functions, such as using structured programming languages, avoiding complex logic, and implementing self-diagnostic checks.
Verification and Validation: The standard emphasizes the need for rigorous testing and verification of safety-related functions to ensure they meet the specified safety requirements. This includes functional testing, fault injection, and analysis of failure modes and effects.
Compliance with IEC 61131-6 helps manufacturers and system integrators develop and implement safe and reliable programmable controllers. By following the guidelines and principles outlined in the standard, organizations can mitigate risks, protect personnel and equipment, and ensure compliance with regulatory requirements related to functional safety in industrial automation.
