What is the difference between IEC 61508 and IEC 62061

In the field of functional safety, two important standards are widely used – IEC 61508 and IEC 62061. These standards provide guidance for the development and assessment of safety-related systems in various industries. Although they have similar objectives, there are notable differences between IEC 61508 and IEC 62061 that engineers and professionals need to be aware of.

Scope and Application

IEC 61508 covers the complete lifecycle of electrical, electronic, and programmable electronic (E/E/PE) safety-related systems. It is a generic standard applicable to various industries such as manufacturing, process control, transportation, and more. On the other hand, IEC 62061 specifically targets the safety of machinery and addresses the particular requirements for mechanical equipment.

While IEC 61508 provides a broad framework for designing and implementing safety-related systems, IEC 62061 offers specific guidelines for assessing the safety of machinery. The scope of these standards determines their applicability and sets them apart in terms of industry focus.

Performance Levels and Validation

A crucial difference between IEC 61508 and IEC 62061 lies in how they define and evaluate the performance levels of safety functions. IEC 61508 utilizes a probabilistic approach, where the required performance level is determined based on the probability of failure. This standard introduces the concept of Safety Integrity Level (SIL), ranging from SIL1 to SIL4, with SIL4 indicating the highest level of safety.

On the other hand, IEC 62061 follows a different methodology known as the Performance Level (PL). PL is defined based on five levels, from PL-a to PL-e, with PL-e representing the highest level of safety. Unlike SIL, which focuses on the probability of failure, PL considers other factors such as fault tolerance, diagnostic coverage, and architectural constraints in assessing the performance level of safety functions.

Functional Safety Management

Functional Safety Management (FSM) plays a crucial role in ensuring the effectiveness and reliability of safety-related systems. Both IEC 61508 and IEC 62061 emphasize the importance of FSM but differ in their requirements.

IEC 61508 incorporates a more comprehensive FSM approach covering the entire lifecycle of safety-related systems. It defines core activities such as hazard identification, risk assessment, safety requirements specification, configuration management, and verification/validation. The standard specifies roles and responsibilities, documentation requirements, and emphasizes the need for independent assessment and auditing processes.

In comparison, IEC 62061 focuses more on machinery safety and places slightly less emphasis on FSM processes. While it prescribes some requirements for FSM, it recognizes that machinery safety standards may already address specific lifecycle stages or processes. Therefore, it allows for alignment with existing standards, provided that the principles of functional safety are met.

Understanding the differences between IEC 61508 and IEC 62061 is essential for professionals involved in designing, developing, and assessing safety-related systems. By following the appropriate standard based on the industry and application, engineers can ensure compliance, reliability, and efficiency in functional safety.