Technical Articles
Compliance and Certification in accordance with IEC 61508: Functional Safety of Electrical / Electronic / Programmable Electronic Safety-related Systems
Compliance and Certification in accordance with IEC 61508: Functional Safety of Electrical / Electronic / Programmable Electronic Safety-related Systems
Introduction:
IEC 61508 is an international standard developed by the International Electrotechnical Commission (IEC) that addresses functional safety for electrical, electronic, programmable electronic systems (E/E/PES). This technical article aims to provide a comprehensive understanding of IEC 61508, focusing on compliance requirements and the certification process for achieving functional safety.
Scope:
IEC 61508 provides a framework for the analysis, design, implementation, and maintenance of functional safety systems. It is applicable to a wide range of industries and sectors where E/E/PES are used, including but not limited to automotive, aerospace, industrial automation, medical devices, and process industries.
Key Provisions:
1. Safety Lifecycle: IEC 61508 emphasizes the concept of a safety lifecycle, which encompasses all phases of a system's life, from concept to decommissioning. It mandates the identification and management of safety-related activities during each stage, including hazard and risk assessment, requirements specification, design, verification, validation, operation, maintenance, and modification.
2. Safety Integrity Levels (SIL): The standard introduces the concept of SILs, which represent target levels of risk reduction required for a safety function. SILs are determined based on the severity of potential consequences, the likelihood of occurrence, and the level of risk reduction achieved by the safety system. Compliance with IEC 61508 involves selecting appropriate SILs for each safety function and ensuring their achievement through appropriate design and implementation measures.
3. Safety Requirements Specification: IEC 61508 requires the development of a Safety Requirements Specification (SRS) that captures all safety-related requirements for the E/E/PES. The SRS includes functional and non-functional requirements, such as performance, reliability, and availability, necessary to achieve the desired SIL targets and ensure functional safety.
4. Verification and Validation: The standard highlights the importance of thorough verification and validation activities throughout the safety lifecycle. It mandates the use of appropriate techniques, such as testing, analysis, and simulation, to demonstrate that the safety requirements are met and that the system operates within the specified safety limits.
Certification Process:
1. Assessment and Planning: The certification process begins with an assessment of the E/E/PES's functional safety. This involves identifying relevant standards and regulations, determining the applicable safety integrity requirements, and developing a certification plan.
2. Documentation Review: The certification body reviews the documentation related to the E/E/PES, including the SRS, design specifications, verification and validation reports, and other relevant records. This ensures compliance with the requirements specified in IEC 61508.
3. Assessment of Implementation: The certification body conducts an on-site assessment to verify the implementation of functional safety measures. This involves reviewing the system architecture, hardware and software designs, safety procedures, and the overall safety management system to ensure that they align with the standard's provisions.
4. Testing and Evaluation: The E/E/PES undergoes rigorous testing and evaluation to assess its performance and reliability under different operational conditions. This includes functional testing, fault injection, and analysis of failure modes and effects to determine if the system meets the specified SIL requirements.
5. Certification and Continuous Improvement: Upon successful completion of the assessment and testing process, the certification body issues a certificate of compliance with IEC 61508. However, functional safety is an ongoing process, and organizations are encouraged to continually monitor, assess, and improve their safety systems to ensure long-term compliance with the standard.
Conclusion:
Compliance and certification in accordance with IEC 61508 are crucial for ensuring functional safety in E/E/PES. The standard provides a framework for managing safety throughout the lifecycle of a system, including hazard analysis, SIL determination, safety requirements specification, verification and validation, and ongoing improvement. The certification process involves assessment, documentation review, implementation evaluation, testing, and issuance of a compliance certificate. By adhering to IEC 61508, organizations demonstrate their commitment to functional safety, mitigate risks, and enhance the reliability and integrity of their electrical and electronic systems.
Nina She