Functional Safety: Ensuring Systems Operate as Intended
Introduction to Functional Safety Standards
Functional safety is an approach to safety that ensures equipment, systems, and processes operate correctly in response to their intended functionality. As industrial systems have grown increasingly automated and complex, functional safety standards have been developed to establish best practices for protecting people, property, and the environment from unintentional harm. This article provides an overview of some of the key international functional safety standards and their objectives.
IEC 61508 Standard
The IEC 61508 standard, published by the International Electrotechnical Commission (IEC), aims to ensure the functional safety of electrical, electronic, and programmable electronic safety-related systems through their lifecycle. Often referred to as the umbrella standard, IEC 61508 establishes a common framework for other IEC functional safety standards and defines core terminology, management responsibilities, and techniques required at each stage of development. It advocates a risk-based approach to functional safety that involves identifying potential hazards, estimating likelihood and severity of any hazardous events, and implementing appropriate risk reduction methods.
IEC 61511 Standard
Building upon IEC 61508, IEC 61511 provides specific Functional Safety requirements for the process industry sector. Known as the functional safety standard for the process industry or SIS standard, IEC 61511 focuses on instrumentation, logic systems, and shut-off valves used to safely shutdown process plants in the event of an emergency. It aims to ensure safety instrumented systems (SIS) are reliable and available to operate on demand to maintain the process in a safe state. Key aspects addressed include lifecycle management, system architecture, engineering design, installation and commissioning, operation and maintenance.
ISO 26262 Standard
ISO 26262 is an international automotive functional safety standard aimed at ensuring functional safety for electrical and/or electronic systems in production automobiles. Published by the International Organization for Standardization (ISO), it was developed to address growing concerns over software-related vehicle defects and establish assessment guidelines for automotive safety integrity levels (ASILs) from A to D based on potential severity of hazards. Requirements cover functional safety concepts, safety life cycle management, product development at the system level, software level and hardware level.
IEC 62061 Standard
Originally published as EN 954-1, IEC 62061 provides functional safety requirements for the design of safety-related parts of control systems for machinery. This includes safety-related control systems, safety-related parts of other control systems, and other technical hardware and software that are used to fulfill safety functions. IEC 62061 aims to reduce risks to persons from hazards in machinery through protective measures like guards, safeguarding devices, and safety functions. Its requirements pertain to all phases of a machinery control system's lifecycle.
Functional Safety Lifecycle Management
To fully realize functional safety objectives, standards advocate careful management throughout a product or system's development lifecycle. Key activities include hazard and risk analysis, safety requirement specification, design implementation, verification and validation testing, change management, installation, commissioning, operation and maintenance. Regular documentation, reviews and audits help ensure deviations from approved safety plans are identified and corrected. Organizations are also responsible for competency training and certification of personnel performing safety tasks. Adhering to functional safety standards provides engineering teams a systematic approach to designing in safety.
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