IEC 61508: The Functional Safety Standard

IEC 61508 is an international standard that provides a framework for ensuring the functional safety of systems that depend on electrical, electronic, or programmable electronic (E/E/PE) technologies. IEC 61508 is a generic functional safety standard and is applicable across a wide range of industries where electrical, electronic, or programmable electronic systems perform safety-related functions that could cause harm to people, the environment, or assets.. It serves as the foundational safety framework for numerous industry-specific standards and is relevant to any sector where system failures could lead to hazardous situations.

Industries Applicable to IEC 61508:

• Industrial Equipment
  • Safety instrumented systems (SIS)
  • Programmable logic controllers (PLCs) with safety functions
• Machinery and Industrial Automation
  • Robotics
  • Manufacturing equipment safety controls
    (Leads into IEC 62061 and ISO 13849-1)
• Automotive
  • Advanced driver-assistance systems (ADAS)
  • Electric vehicle safety systems
    (IEC 61508 forms the basis for ISO 26262)
• Medical Devices
  • Life-supporting or life-sustaining systems
    (Sometimes supports compliance with IEC 60601-1 and IEC 62304)
• Renewable Energy
  • Wind turbine control systems
  • Solar plant safety controllers
• Power Generation
• Process Industry
  • Chemical plants
  • Oil and gas facilities
  • Water treatment
    (Often applied through IEC 61511, derived from IEC 61508)
• Railway and Transportation
  • Train control and signaling systems
  • Mass transit and automated transport
    (Influences standards like EN 50126/50128/50129)
• Aerospace and Defense
  • Flight control systems
  • Missile and weapon control safety

Scope of IEC 61508

The scope of IEC 61508 encompasses the development and management of electrical, electronic, and programmable electronic (E/E/PE) systems that perform safety-related functions. It provides a generic, cross-sector framework that serves as the foundation for many industry-specific functional safety standards. The standard covers the entire safety lifecycle, from concept and risk assessment through design, implementation, operation, maintenance, and decommissioning. It ensures that systems function correctly and reliably to reduce risks to acceptable levels. IEC 61508 applies to both hardware and software, addressing random hardware failures, systematic design issues, and human error. A key feature is the use of Safety Integrity Levels (SILs), which classify the required reliability of safety functions based on the severity of potential hazards.

IEC 61508 Testing for Compliance

IEC 61508 testing is not a single pass/fail test, but a structured process embedded within the product’s development lifecycle. It combines analytical techniques, functional testing, fault simulation, and rigorous documentation to verify that the system meets defined safety integrity levels and operates reliably under both normal and failure conditions.

Typical Test Procedure for IEC 61508

1. Safety Requirements Specification (SRS) Review - confirm that safety functions and target SIL are clearly defined while verifying traceability of all safety requirements throughout the development and test processes.
2. Hardware and Software Design Validation - evaluate the product's architecture, redundancy, and fault tolerance features ensuring compliance with design rules and SIL-specific requirements for failure rates, diagnostics, and reliability.
3. Failure Mode and Effects Analysis (FMEA/FMEDA) - perform detailed analysis to identify potential failure modes and their effects.
4. Static Code Analysis and Software Review - analyze source code for compliance with safe coding standards and check for logic errors, dead code, and adherence to software development practices outlined in IEC 61508-3.
5. Dynamic Testing (Unit, Integration, and System Testing) - test individual components (unit tests), integrated subsystems (integration tests), and the full system (system tests). Confirm correct execution of safety functions under normal and fault conditions.
6. Fault Injection and Diagnostic Testing - introduce faults to validate the system’s response and assess diagnostic coverage and the system’s ability to enter a safe state when needed.
7. Hardware Reliability Testing - perform environmental and stress testing (temperature, vibration, EMC, etc.) to simulate operational conditions.
8. Proof Testing Procedures - define and verify procedures to regularly test safety functions during the product’s operational life and ensure these procedures effectively detect latent faults.
9. Safety Function Performance Verification - measure the actual performance of safety functions (e.g., response time, signal integrity) and compare results to SRS requirements.
10. Documentation and Certification Review - compile all test data, analysis results, and traceability matrices and submit documentation to a third-party certifying body, such as Intertek, for independent assessment and certification.

Intertek's Functional Safety Solutions

We support full lifecycle functional safety compliance with frameworks like IEC 61508, addressing risk assessment, safety integrity levels (SIL), failure analysis methods (such as FMEA and FTA), and overall systems interaction. Our functional safety services not only enhance safety and reliability but also reduce liability, warranty claims, and operational downtime—ultimately boosting product quality and competitive advantage. We offer services that extend across sectors including industrial machinery, hazardous environments, medical devices, transportation, utilities, and more.