What is IEC 61508

Introduction

IEC 61508 is a standard that embodies the concept of functional safety in the design and development of electrical, electronic, and programmable electronic systems. Compliance with this standard ensures that these systems are reliable and safe to use in various industries such as automotive, aerospace, and manufacturing.

Understanding IEC 61508

IEC 61508 provides a comprehensive framework for managing functional safety throughout the lifecycle of a system. The standard outlines principles, requirements, and guidance on functional safety assessment, management, and verification.

One of the fundamental concepts in IEC 61508 is the item. An item refers to a hardware or software component that contributes to achieving a specific safety-related function. This can range from simple components like sensors and actuators to complex systems like control units and safety instrumented systems.

The standard classifies items into several Safety Integrity Levels (SILs) based on their level of risk reduction. SIL 4 represents the highest level of safety integrity, while SIL 1 represents the lowest. Each SIL has corresponding requirements and performance targets that must be met during the development and operation of the system.

Writing an IEC 61508 Item

Developing an IEC 61508 item involves a rigorous process to ensure functional safety. This includes requirements specification, architectural design, software development, and verification/validation activities.

Firstly, the safety requirements for the item must be clearly defined. This involves understanding the intended function, its reliability requirements, and any potential hazards or risks associated with its operation.

Next, the architectural design phase involves determining the necessary hardware and software components to meet the safety requirements. Factors such as redundancy, fault tolerance, and diagnostics play a critical role in achieving the required safety integrity.

Once the design is complete, the software development process begins. Special attention must be given to programming practices that minimize potential systematic faults, such as avoiding unsafe constructs and utilizing appropriate coding standards.

After the item is developed, comprehensive testing and verification/validation activities are conducted to ensure that it meets the specified safety requirements. This includes functional testing, fault injection, and evaluation of failure modes and effects.

Conclusion

IEC 61508 plays a vital role in ensuring the functional safety of electrical, electronic, and programmable electronic systems. Understanding the concept of an IEC 61508 item and following the prescribed processes for its development can greatly enhance the reliability and safety of these systems.

Compliance with this standard not only fosters confidence among users but also contributes to preventing accidents and minimizing the risks associated with complex technological systems.