Introduction to ISO 13849 and Safety Integrity Levels

In the realm of industrial automation and machine tools, ensuring the safety of operators and technicians is of paramount importance. ISO 13849 is an international standard that plays a critical role in achieving this by providing guidelines for the safety-related parts of control systems. This standard is often discussed in conjunction with Safety Integrity Levels (SIL), which are used to quantify the performance requirements of safety functions. Understanding the relationship between ISO 13849 and SIL can help manufacturers and engineers design more effective safety systems for machine tools.

Understanding ISO 13849

ISO 13849 is part of the ISO 12100 series of standards dedicated to machine safety. It specifically addresses the safety-related parts of control systems (SRP/CS). The standard provides a framework for assessing the performance of these parts, focusing on the Probability of Dangerous Failure per Hour (PFH). It ensures that the control system can adequately reduce risks associated with machine operation.

ISO 13849 also introduces the concept of Performance Levels (PL), which are used to categorize the ability of a system to perform a safety function under foreseeable conditions. These levels range from PLa to PLe, with PLe representing the highest level of safety.

Safety Integrity Levels (SIL) Explained

While ISO 13849 uses Performance Levels, the concept of Safety Integrity Levels (SIL) comes from another set of standards known as IEC 61508 and its sector-specific derivatives, like IEC 62061 for machinery. SIL ratings are used to describe the reliability of electrical, electronic, and programmable electronic safety-related systems. They indicate the required risk reduction and are assigned based on the severity of potential hazards.

SILs range from SIL 1 to SIL 4. A higher SIL level indicates a greater degree of risk reduction and reliability required from the safety system. SIL 4 represents the highest level of safety integrity, often reserved for applications with very high-risk potential.

Comparing PL and SIL

While both PLs and SILs aim to ensure safety, they originate from different standards and industries. PLs are widely used in the machinery sector, while SILs are common in process industries. One of the key distinctions between them is the primary focus: PLs emphasize the architecture and robustness of the safety system, whereas SILs focus on the failure probabilities and the overall performance of a system.

Despite these differences, there is a level of alignment between the two. Conversion tables exist to help engineers translate between PLs and SILs, facilitating communication and standardization across different sectors and applications.

Implementing ISO 13849 in Machine Tool Safety

Incorporating ISO 13849 into machine tool safety involves several steps. Firstly, a detailed risk assessment must be conducted to identify potential hazards and quantify the associated risks. Once the risks are known, the appropriate Performance Level can be determined for each safety function. This assessment helps in deciding the necessary measures and technologies to implement.

Designing the SRP/CS includes selecting components and subsystems that meet the required PL or SIL. It often involves redundancy, fault detection, and fail-safe principles to enhance reliability. Regular validation and verification are crucial to ensure that the implemented system performs as intended and complies with the set requirements.

Benefits of Understanding and Applying SIL Ratings

By comprehending and applying SIL ratings alongside ISO 13849, manufacturers can significantly enhance the safety and reliability of their machine tools. This not only protects operators and reduces the likelihood of accidents but also ensures compliance with international safety standards. Moreover, it fosters a culture of safety and innovation, where continuous improvements are made to adapt to emerging technologies and challenges.

Conclusion

ISO 13849 and SIL ratings are essential tools in the arsenal of safety engineers and manufacturers aiming to create safer machine tools. Understanding their differences and synergies enables a more comprehensive approach to safety, ensuring that machines operate within acceptable risk levels. As technology evolves, staying informed and compliant with these standards will remain crucial in safeguarding the well-being of those who work with and around industrial machinery.