scope:

In the context of the safety of machinery, the sector standard IEC 62061 as well as ISO 13849-1 provide requirements to manufacturers of machines for the design, development and integration of safety-related control systems (SCS) or safety-related parts of control systems (SRP/CS), depending on technology used (mechanical, pneumatic, hydraulic or electrical technologies) to perform safety function(s). This document does not replace ISO 13849-1 and IEC 62061. This document gives additional guidance to the application of IEC 62061 or ISO 13849-1. This document: - gives guidelines and specifies additional requirements for specific safety functions based on the methodology of ISO 12100, which are relevant in machinery and respecting typical boundary conditions of machinery; - considers safety functions which are designed for high demand mode of operation yet are rarely operated, called rarely activated safety functions; NOTE 1 - IEC 62061:2021 completely covers high demand. However, other safety functions related to the protection of the machine itself and indirectly of persons are considered more in detail in this document. - gives additional information for the calculation of failure rates using other (non-electronic) technologies based e.g. on Weibull distribution, because all the formula defined in IEC 62061 and ISO 13849-1 are based on exponential distribution. Therefore, the basis for these guidelines and additional requirements is - a typical classification of safety functions; - a consideration of typical architectures used for designing safety functions; - a consideration of modes of operation of safety functions; - the derivation and evaluation of PFH formulas for subsystems considering the used technology. NOTE 2 - These guidelines can also be used for application of ISO 13849-1 for the design process of SRP/CS. This document does not address low demand mode of operation according to IEC 61508.