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 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.
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 purpose of such standards is to determine the Performance Level (PL) or the Safety Integrity Level (SIL) reached, based on the architecture of the system and the reliability of the components.
The verification – as conducted by ECO Certificazioni – of the parts linked to the safety of the command system is a voluntary modular service structured in phases. The service was developed to accompany machine manufacturers from the defining of the safety functions deriving from the machine risk assessment, to then continue on to the definition of the functional diagrams (Functional Block Diagram or FBD and Reliability Block Diagram or RBD), up to the evaluation of the functional safety parameters required and the relative level of reliability (SIL/PL required), and finally the verification of the correct planning through the evaluation of the reliability parameters analysed (SIL/PL verification), including the drafting of the relative sections of manuals (Manuals for Safety Loops).
Activities for the planning, definition and verification phases of the “Safety Integrity Level”:
Activities for the planning, definition and verification phases of the “Performance Level”.
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.