The rapid development of automation and distributed intelligence has led to an exponential increase in machinery, systems, devices and products with electronic or programmable command and control systems that are given security functions.
When the functionality of an element within a system can jeopardize its safety, ensuring just primary safety is no longer sufficient; functional safety must also be guaranteed.
The topics covered by the IEC 61508 family of standards and those related to them (ISO 13849s, ISO 16232s, IEC 62061, IEC 61800-5-2, IEC 61496s, EN 50495, etc.) constitute the state-of-the-art and the normative reference for the design and management of safety systems in plants, with particular attention to electrical, electronic and programmable electronic systems. They are widely used in various industrial sectors including the chemical, petrochemical, refining, nuclear, transport, electro-medical, industrial automation and automotive industries.
Machinery Directive 2006/42/EC requires that the safety-related elements of the control system be designed and constructed so as to ensure that any failure in the control logic of the machinery does not cause dangerous events. It thus becomes critical to determine the Performance Level (PL) achieved, based on the parameters of the chain of command and, in particular, on the Diagnostic Coverage (DC) and on the Mean Time to Dangerous Failure (MTTFD) or B10D for electromechanical/mechanical components.
The EN ISO 13849-1:2015 Standard “Safety of machinery – Safety-related parts of control systems – Part 1: General principles for design” pursues these objectives to ensure the proper selection and design of the hardware and software architecture that manages how the machinery operates.
The standard EN ISO 13849-2: 2012 “Safety of machinery – Safety-related parts of control systems – Part 2: Validation”, on the other hand, constitutes the final part of the design process, i.e. the validation of the machinery control system.