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IEC 61508 STANDARD & SAFETY INTEGRITY LEVELSOperational safety is defined as the absence of unacceptable risks, injury or harm to the health of humans, whether direct or indirect, resulting from damage toequipment or the environment. A risk analysis allows for the determination of how operational safety will allow for a guarantee of adequate protection againstany risk that may arise. These dangers are therefore treated appropriately during the design phase so that the final system is fault-free.

Safety functions result from electrical, electronic or programmable electronic systems, which are usually complex and make it very difficult to determine breakdowns. The objective is therefore to design a system in such a way as to preventas many breakdowns as possible and control them when they do occur.

Breakdowns may occur for a number of different factors:

Software errors,Human error,Environmental influence,Random breakdown of equipment mechanisms,

Etc.Operational safety therefore depends on the proper operations of a global systemor equipment in response to system or equipment entries. For this reason, standard IEC 61508 was created.

THE IEC 61508 STANDARD

Titled Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems, it includes the necessary and sufficient requirements to minimize these breakdowns. All the phases of the equipment and software lifecycle (from the conceptualization through to the design, installation, operations, maintenance and final disposal) are involved.

IEC 61508 was approved by CENELEC as a European Standard (ES)

Standard IEC 61508 presents a generic approach to all activities related to thelifecycle (from the creation to the disposal of the system) of the electrical-electronic-programmable electronic (E/E/PE) elements that are used to realize safety features.

Due to the broad variety of electrical-electronic-programmable electronic applications at very diverse levels of complexity, the IEC 61508 standard defines methods for analysis and development in order to achieve operational safety based ona risk analysis and determine the safety integrity level (SIL) to be reached for a given risk, but no general rules per se.

50126, 50129, 50128 : STANDARDS DERIVED FROM THE IEC 61508

Standards derived from the IEC 61508 include, for example, standards for industrial processes (IEC 61511), the nuclear sector (IEC61513), machine safety (IEC 62061 and ISO 13849) or railway industry (EN 50126/EN 50128 /EN 50129).

In this area, the EN 5012x standards are based on system life cycle and were written to fit the requirements of IEC 61508 generic standard constraints in this sector. Compliance with the requirements of the EN 5012x standards is sufficientto ensure compliance with the IEC61508 standard without necessitating any further evaluation.

SIL: SAFETY INTEGRITY LEVEL

The SIL or Security Integrity Level is a level of safety integrity. The SIL noti

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on results directly from the IEC 61508 standard. The SIL may be defined as a measurement of operational safety that determines recommendations related to the integrity of the safety features to be assigned to E/E/PE systems.

There are four SIL levels: SIL4 being the highest level of system security, SIL1the lowest.

This involves an average probability of failure on demand, PFDavg, for a periodof 10 years.

SIL 4 Very significant impact on the community leading to a reduction in danger from 10000 to 100000SIL 3 Very significant impact on the community and employees leading to a reduction in danger from 1000 to 10000SIL 2 Significant protection of the installation, production and employees leading to a reduction in danger from 100 to 1000.SIL 1 Low protection of the installation and production leading to a reductionin danger from 10 to 100.Thanks to significant expertise in formal calculation, operational safety and th

e use of the B method (broadly used in industry to create proven safety software), ClearSy System Engineering is qualified to conduct projects that require a SIL certification (SIL2, SIL3 or SIL4) pursuant to IEC 61508 standard.