ISO 13849

ISO 13849 is an international standard concerning the safety of machinery. More specifically, it addresses safety-related parts of control systems (SRP/CS). It is divided into two main parts: ISO 13849-1, which outlines general principles for design, and ISO 13849-2, which focuses on validation.

The purpose of ISO 13849 is to provide a framework for designing and validating safety functions within machine control systems, reducing risks to operators and other personnel. It uses a risk-based approach, requiring designers to identify hazards, assess risks, and implement appropriate safety measures to achieve a defined performance level (PL).

Key concepts within ISO 13849 include:

• Performance Level (PL): A measure of the safety function's ability to perform its intended purpose under foreseeable conditions. PLs range from PL a (lowest) to PL e (highest).
• Category: A classification of the architecture of a safety-related control system, ranging from Category B (basic) to Category 4 (highest redundancy and monitoring).
• Mean Time To Dangerous Failure (MTTFd): The average time a component or subsystem is expected to function before a dangerous failure occurs.
• Diagnostic Coverage (DC): The effectiveness of the diagnostics in detecting dangerous failures.
• Common Cause Failure (CCF): Failures of multiple components or subsystems due to a single cause.

ISO 13849 is often used in conjunction with other standards, such as ISO 12100 (Safety of machinery – General principles for design – Risk assessment and risk reduction), which provides guidance on risk assessment. The standard provides a structured approach to ensure that safety functions are designed, implemented, and validated to a level commensurate with the identified risks. Compliance with ISO 13849 helps manufacturers demonstrate due diligence and meet regulatory requirements related to machine safety.