Practical assistance on the revised standard for controls

Status:

completed 11/2007

Aims:

ISO 13849-1:2007 (EN 954-1 Safety of machinery - Safety-related parts of control systems - Part 1: General principles for design) is a generic machinery standard presenting requirements for the structure and probability of failure of safety-related control systems. In this context, the current version, which dates back to 1997, defines five typical control system architectures, termed "Categories" (single or two-channel, tested/untested), independent of the technology employed (mechanical, pneumatic, hydraulic, electrical). This standard has now been thoroughly revised. A BGIA Report had therefore to be produced as an aid to application of the revised machine construction standard EN ISO 13849-1. Besides explaining the complex subject-matter of the standard, the report serves also to illustrate the assessment methods with reference to numerous practical examples. Use of the standard, which has become more complex owing to the revision, is simplified as a result. Besides increasing the standard's acceptance, the report enables errors in its application to be avoided. At the same time, typical solutions are discussed for common control tasks.

Activities/Methods:

The methods described in the standard were developed for the most part in the BGIA - Institute for Occupational Safety and Health of the German Social Accident Insurance. They were edited step by step by a number of control system experts in order to provide comprehensible illustrations of and comments on the complex subject-matter. The various approximation methods of ISO 13849-1 were considered both in general terms and with reference to specific examples. For this purpose, all relevant steps of the methods described in the standard were formulated in a readily comprehensible form suitable for real-case application. The new version of ISO 13849-1 also addresses requirements for software (firmware and application programming). Handling of these requirements and typical approaches to solutions were also discussed and formulated in the report. The differences between ISO 13849-1 and other standards governing controls were also addressed, as was the integration of subsystems already tested in accordance with other standards.

Results:

The results of the project are summarized in a comprehensive BGIA Report which was published at the beginning of 2008. The first four chapters provide an introduction to the subject-matter, including a description of the historical background, an overview of the relevant standards, and a structured overview of EN ISO 13849 and the report itself. The extensive chapters five to seven describe practical application of the standard in detail with regard to safety functions and their contribution to risk reduction, assessment of the Performance Level, and its validation. General explanations are followed by practical information on application of the standard over and above that contained in the standard itself, and by interpretations of it. The explanations are accompanied by a detailed example. Practical examples from a number of sectors are provided in the form of a further 37 block diagrams, not technology-specific, together with brief descriptions. Nine annexes provide additional information or more detailed information on particular subjects.

The report can be used to obtain a comprehensive overview or for access to specific topics or applications. It serves to inform readers or as an aid to consultancy and testing. In conjunction with the BGIA SISTEMA software developed at the same time, the report thus substantially promotes understanding of the important control standard EN ISO 13849, both nationally and internationally, and among its users.

Further informations:

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