The STSARCES project aims at speeding up not only the revision of EN 954 part 1 and the drafting of emerging standards like the EN 954 part 2, but also their harmonised putting into practice by test-houses as well as by manufacturers of the European Union.
Links need to be established to avoid divergences of EN 954 with international basic safety standards.-
The methodology is based on the concept of the overall safety lifecycle of a system, which is quite new in the field of the machinery and covers both hardware and software in an integrated way. A significant part of the results deal with the software life cycle, since this is not developed in EN 954.The Markov modelling approach, also very innovative when applied to the field of the machinery, has revealed very successful. The immense influence of the diagnostic coverage could be demonstrated and data on appropriate on-line test intervals for these dedicated architectures proposed in the methodology, combined with realistic MTTF values, are provided and justified. Such information provides fundamental advice for the system designer as well as hints for the persons carrying out the evaluations. STSARCES succeeds to determine validation methods of programmable electronic systems in their use for safety functions both in EN 954 and draft IEC 62061, a machine application standard derived from IEC 61508. It does allow defining credible and understandable links between CATEGORIES (EN 954) and Safety Integrity Levels or SILs (draft IEC 62061). This connection is indispensable during the design and development phases of control circuits for the machinery, which make use of components based on the category concept, like mechanical, hydraulic, pneumatic, electro-mechanical ones, and simultaneously of programmable electronic systems, better characterised by the SIL concept.
Technical reports on software safety were yet transferred at mid-term to TC 44 WG 7 for IEC 62061. The results were presented to CEN TC 114 WG6 CD-ROMs of the Final Report were disseminated. The Final Report will be made available during the summer 2000 on the European Network SAFETYNET with comprehensive links to all technical annexes.
In the field of machinery safety, the essential requirements regarding the safety-related parts of control systems are covered by EN 954 part 1 (1996) dealing with general principles for design. Current work on the validation process of such systems, including both analysis and testing, has demonstrated that no harmonised validation procedures exist for safety-related complex electronic systems, which are becoming of a generalised use in the machinery sector, and include often today programmable technologies. Furthermore, deterministic validation methods, commonly used with low complexity systems, are faced with practical limitations.
(1) software aspects need investigating tools for avoidance of systematic faults.
(2)Testing procedures need to be supplemented by analysis of the design to properly evaluate safety performances of both hardware and software elements.
(3) understandable links for the machinery sector need to be established between EN 954 and IEC 61508.
(4)With respect to industry interests, consideration of innovative technologies and designs, in close relationship with manufacturers in the consortium, must be incorporated, to avoid innovation (i.e. competitiveness of the European industry) obstacles by emerging standards.are.
Funding SchemeCSC - Cost-sharing contracts
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