ISO 13849

ISO 13849 is a safety standard which applies to parts of machinery control systems that are assigned to providing safety functions (called safety-related parts of a control system).

• ISO 13849-1, Part 1: General principles for design, provides safety requirements and guidance on the principles of design and integration of safety-related parts of control systems (hardware or software).
• ISO 13849-2, Part 2: Validation, specifies the procedures to be followed for validating by analysis or tests, the safety functions of the system, the category achieved and the performance level achieved.

In Part 1, ISO 13849, the design of the safety system is based on the risk assessment performed by the manufacturer of the machine. This risk assessment identifies the safety functions required to mitigate risk and the performance level these functions need to meet to adequately mitigate the identified risks. The performance level of a function is determined by the architectural characteristics of the controller (classified according to categories), the MTTFd of the components and system and the average diagnostic coverage implemented in the system. The principle here is that not only shall the control system be able to perform the safety function to a level that will mitigate the identified risk, but also do so in the presence of a failure.