IEC 61508-4 PDF

3 Dec IEC Standard | functional safety, smart city | Functional safety of electrical/electronic/programmable electronic safety-related. 12 May 4) In order to promote international unification, IEC national IEC has been prepared by sub-committee 65A: System aspects, of IEC. IEC contains the definitions and explanation of terms that are used in parts 1 to 7 of the IEC series of standards. The definitions are.

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In any particular application, the required safety measures will be dependent on many factors specific to the application This International Standard, by being generic, will enable such measures to be formulated m future application sector international standards. Figure 4 – Failure model 3. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of ‘BIS Catalogue’ 61058-4 ‘Standards: An example of such a fault is a design fault.

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6108-4 In most situations, safety is achieved by a number of protective systems which rely on many technologies for example mechanical, hydraulic, pneumatic, electrical, electronic, programmable electronic. Definitions and abbreviations [ETD Review of Indian Standards Amendments are issued to standards as the need arises on the basis of comments. This unified approach has been adopted in order that a rational and consistent technical policy be developed for all electrically 61058-4 safety-related systems.

This Indian Standard has been developed from Doc: The text of lEC Standard has been approved as suitable for publication as an Indian Standard without deviations.

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The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard. Dependability and quality of service lEC EXAIWPLE Verification activities include – reviews on outputs documents from all phases of the safety lifecycle to ensure compliance with the objectives and requirements of the phase, taking into account the specific inputs to that phase; design 16508-4 Overview of techniques and measures ISO Although there may be other systems having safety functions, it is the safety-related systems that have been designated to achieve, in their own right, the required tolerable risk Iev related systems can broadly be divided into safety-related control systems and safety-related protection systems, and have two modes of operation see 3.

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Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision.

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The corresponding Indian Standards, isc are to be substituted in their respective places, are listed below along with their degree of equivalence for the editions indicated: NOTE 3 – The term safe diagnostic coverage, or diagnostic coverage including sate failures, is used to descnbe respectively the fractional decrease in the probability of safe hardware failure, or of both safe and dangerous hardware failures, resulting from the operation of the automatic diagnostic tests 3.

Computer-based systems genencally referred to as programmable electronic systems PESs are being used in all application sectors to perform non-safety functions and, increasingly, to perform safety functions. General requirements lEC For undated references, the latest edition of the normative document referred to applies. Figure 2 d illustrates a PES with dual programmable electronics i e two-channel but with a single sensor and a single actuator 3.

NOTE 2 – The safety- related systems are designed to prevent the EUC from going into a dangerous state by taking appropriate action on receipt of commands. Attention is particularly drawn to the following: Certain conventions are, however, not identical to those used in Indian Lec.

In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist. A major objective is to facilitate the development of application sector standards. NOTE 2 – The term can be used to describe a complete system, or a portion of a system for example, sensors or final elements.

International Standard lEC Guide See also lec A of lEC This does not preclude the free use, in course of implementing the standard, of necessary details, such as symbols and sizes, type or grade designations. Examples of methods 16508-4 the determination of safety integrity levels lEC For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with IS 2: Fundamental terms ISO Any safety strategy must therefore consider not only all the elements withm an 61508-44 system for example sensors, controlling devices and actuators but also all the safety-related systems making up the total combination of safety-related systems.

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Automatic control lEC Copyright BIS has the copyright of all its publications. 615508-4 part of these publications may be reproduced in any form without the prior permission in writing of BIS. If separate channels are used, these tests are done for each channel separately. International Standard lEC That is, the required safety integrity level may be achieved by implementing the safety functions in the EUC control system and possibly by additional separate and independent systems as well or the safety functions may be implemented by separate and independent systems dedicated to safety NOTE 4 – A safety-related system may a be designed to prevent the hazardous event i.

Figure 2 — Programniable electronic system PES: H c Single PES with dual program- mable electronic devices linked in a serial manner for example intelligent sensor and programmable controller H PEi d Single PES with dual program- mable electronic devices but with shared sensors and final elements i. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply However, parties to agreements based on this part of lEC are encouraged to investigate the possibility of applying the most 615008-4 editions of the normative documents indicated below.

If computer system technology is to be effectively and safely exploited, it is essential that those responsible for making decisions have sufficient guidance on the safety aspects on which to make those decisions.

The failure of a safety-related system would be included m the events leading to the determined hazard or hazards. Data processing – Vocabulary – Part Software requirements lEC