Functional Safety Of Machine Controls
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Functional safety of machine controls
The EN ISO 13849-1 standard, “Safety of machinery – Safety-related parts of control systems”, contains provisions governing the design of such parts. This report is an update of BGIA Report 2/2008e of the same name. It describes the essential subject-matter of the standard in its third, revised 2015 edition, and explains its application with reference to numerous examples from the fields of electromechanics, fluidics, electronics and programmable electronics, including control systems employing mixed technologies. The standard is placed in its context of the essential safety requirements of the Machinery Directive, and possible methods for risk assessment are presented. Based upon this information, the report can be used to select the required Performance Level PLr for safety functions in control systems. The Performance Level PL which is actually attained is explained in detail. The requirements for attainment of the relevant Performance Level and its associated Categories, component reliability, levels of diagnostic coverage, software safety and measures for the prevention of systematic and common-cause failures are all discussed comprehensively. Background information is also provided on implementation of the requirements in real-case control systems. Numerous example circuits show, down to component level, how Performance Levels a to e can be engineered in the selected technologies with Categories B to 4. The examples provide information on the safety principles employed and on components with well-tried safety functionality. Numerous literature references permit closer study of the examples provided. The report shows how the requirements of EN ISO 13849-1 can be implemented in engineering practice, and thus makes a contribution to consistent application and interpretation of the standard at national and international level.
Functional Safety of Machinery
FUNCTIONAL SAFETY OF MACHINERY Enables readers to understand ISO 13849-1 and IEC 62061 standards and provides a practical approach to functional safety in machinery design Functional Safety of Machinery: How to Apply ISO 13849-1 and IEC 62061 introduces functional safety of machinery as a single unified approach, despite the existence of two standards. Aligning with the latest updates of ISO 13849-1 and IEC 62061, the book explains the intent behind the standards and the mathematical basis on which they are written, details the differences between the two standards, and prescribes ways to put them into practice. To aid in seamless reader comprehension, detailed examples are included throughout the book which walk readers through concepts like Random and Systematic Failures, High and Low demand mode of operation, Diagnostic Coverage, and Safe Failure Fraction. Other sample topics covered within the book include: Basics of reliability engineering and functional safety Roles of the standards in the design and evaluation of safety functions Description of the Main Parameters used in the two standards How to deal with Low Demand Safety Systems The Categories of ISO 13849-1 and the Basic Subsystem Architectures of IEC 62061 How Categories and Architectures can be validated Machinery design engineers, machinery manufacturers, and professionals in system and industrial safety fields can use this book as a one-stop resource to understand the specifics and applications of ISO 13849-1 and IEC 62061.
Safe drive controls with frequency inverters
Machine drives using closed-loop speed control are state of the art. As on drives without closed-loop speed control, the movement of a machine part at varying speeds frequently gives rise to a hazard against which the machine operators must be protected. The simplest means of preventing movements during manual intervention in danger zones is the (safe) disconnection of the energy driving the relevant motors. This is however often not possible, for example when intervention is required whilst the machine is running for the purpose of clearing faults, setup, during test operation, etc. Scenarios such as these require the machine to be operated with protective equipment disabled. In order for the operators‘ safety to be assured nonetheless, Annex I, Section 1.2.5 of the Machinery Directive sets out the required measures. Safety sub-functions for drive controls have been defined for implementation of the machine functions required for this purpose. Examples are STO (safe torque off), SLS (safely limited speed) and SS1 (safe stop 1). This report addresses the use of drive control equipment that implements safety sub-functions at a certain Performance Level according to ISO 13849-1 in consideration of the application and risks. The basic safety sub-functions of drive controls and the requirements relating to their use are presented. The principles of operation of frequency inverters and DC converters are described, and implementation of the safety sub-functions are explained. Examples are provided of application circuits by which the various machine safety functions can be implemented. The corresponding SISTEMA files for quantification of these safety functions are available for download free of charge. The examples include both standard frequency inverters and frequency inverters with integrated safety functions.