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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Attention 61508–4 particularly drawn to the following: Copyright BIS has the copyright of all its publications. 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’ and ‘Standards: 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.

Definitions and abbreviations [ETD Examples of methods for the determination of safety integrity levels lEC Figure 2 — Programniable electronic system PES: The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

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 Safety- related systems can broadly be divided into safety-related control systems and safety-related protection systems, and have two modes of operation see 3. The corresponding Indian Standards, which are to be substituted in their respective places, are listed below along with their degree of equivalence for the editions indicated: Figure 2 iwc illustrates a PES with dual programmable electronics i e two-channel but with a single sensor and a single actuator 3.

For undated references, the latest edition of the normative document referred to applies.

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.

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: Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a ic regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency 6158-4 accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular 615008-4 to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.


NOTE 2 – The term can be used to describe a complete system, or a portion of a system for example, sensors or final elements. 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. Automatic control lEC General kec lEC Overview of techniques and measures ISO NOTE 2 – The safety- related systems are designed to prevent the EUC from going into a dangerous state by 16508-4 appropriate action on receipt of commands.

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 iwc the automatic diagnostic tests 3.

International Standard lEC Guide An example of such a fault is a design fault. 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. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that 615084 changes are needed; if the review indicates that changes are needed, it is taken up for revision.

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. Certain conventions are, however, not identical to those used in Indian Standards. Software requirements lEC ieec Any safety strategy must therefore consider not only all the elements withm an individual system for example sensors, controlling devices and actuators but also all the safety-related systems making up the total combination of safety-related systems.

Dependability and quality of service lEC 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. Programming languages I EC 61 ieec The text of lEC Standard has been approved as suitable for publication as an Indian Standard without deviations.


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.

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This unified approach has been adopted in order that a rational and consistent technical policy be developed for all electrically baseo safety-related systems. 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 reviews: Search the history of over billion web pages on the Internet.

See also annex A of lEC International Standard lEC Review of Indian Standards Amendments are issued to standards as the need arises on the basis of comments.

No part of these publications may be reproduced in any form without the prior permission in writing of BIS. 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 recent editions of the normative documents indicated below.

This Indian Standard has been developed from Doc: Fundamental terms ISO If separate channels are used, these tests are done for each channel separately. In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist. Data processing – Vocabulary – Part A major objective is to facilitate the development of application sector standards.

Figure 4 – Failure model 3. The failure of a safety-related system would be included m the events leading to the determined hazard or hazards.