IEC 61508-5-2010 PDF

Full title and description

IEC 61508-5:2010 — Functional safety of electrical/electronic/programmable electronic safety-related systems. Part 5: Examples of methods for the determination of safety integrity levels. This part of IEC 61508 provides worked examples, methods and practical guidance to help determine required safety integrity levels (SILs) for safety functions and to illustrate application of the principles given in the main parts of the IEC 61508 series.

Abstract

IEC 61508-5:2010 presents representative examples and calculation approaches for assigning safety integrity levels (SIL 1 to SIL 4) to safety functions in electrical/electronic/programmable electronic (E/E/PE) systems. It complements the normative prescriptions of IEC 61508 by showing practical methods, typical assumptions, probabilistic techniques and architectural considerations that support the determination and justification of required SILs for specific safety functions.

General information

• Status: Published standard (in-force publication from 2010).
• Publication date: 2010.
• Publisher: International Electrotechnical Commission (IEC).
• ICS / categories: Functional safety; electrotechnical systems (ICS classification for safety-related systems).
• Edition / version: 2nd consolidated edition (2010), IEC 61508 series second edition).
• Number of pages: Approximately 40–80 pages (publication format varies by publisher and national body).

Scope

This part gives illustrative examples and methods to determine safety integrity levels for safety functions implemented by E/E/PE systems. It shows how to apply probabilistic failure rate calculations, diagnostic coverage and architectural constraints to justify SIL assignments, and how to interpret and apply the requirements from Parts 1–4 of IEC 61508 in practical engineering cases. It is intended to aid engineers in translating risk assessments into specific SIL requirements and in documenting the rationale.

Key topics and requirements

• Worked examples of SIL determination for representative safety functions.
• Probabilistic methods and model calculations for random hardware failures.
• Use of diagnostic coverage (DC), proof-test intervals and safe-state assumptions in calculations.
• Architectural constraints and redundancy techniques relevant to achieving target SILs.
• Guidance on combining systematic capability and hardware fault tolerance considerations.
• Documentation and justification practices for SIL assignments and verification planning.

Typical use and users

Primary users are functional safety engineers, system designers, safety assessors, certification bodies, and project managers working on the design, assessment and certification of safety-related E/E/PE systems. Typical applications include process industry safety instrumented systems, machinery safety controllers, transportation safety subsystems and other sectors where electronic safety functions are required to meet quantified integrity targets.

Related standards

IEC 61508-5 is part of the IEC 61508 series (Parts 1–7). Other related and commonly referenced standards include IEC 61511 (process industry safety instrumented systems), IEC 62061 and ISO 13849 (machinery safety), and sector-specific functional-safety standards and guidance documents that map IEC 61508 concepts to particular industries.

Keywords

IEC 61508, functional safety, safety integrity level, SIL, E/E/PE systems, probabilistic methods, diagnostic coverage, architectural constraints, safety assessment, safety justification.

FAQ

Q: What is this standard?

A: IEC 61508-5:2010 is Part 5 of the IEC 61508 series and provides examples and methods to determine safety integrity levels for safety functions implemented by electrical/electronic/programmable electronic safety-related systems.

Q: What does it cover?

A: It covers worked examples, calculation methods (probabilistic and related), use of diagnostic coverage, architectural considerations and guidance to support justification of required SILs derived from risk assessments and the requirements in other parts of IEC 61508.

Q: Who typically uses it?

A: Functional safety engineers, system designers, safety assessors, certification bodies and project managers involved in designing, verifying or certifying safety-related E/E/PE systems across industries (process, machinery, transportation, etc.).

Q: Is it current or superseded?

A: IEC 61508-5 was published in 2010 as part of the second-edition consolidation of the IEC 61508 series. Users should check with their national standards body or the IEC for any later amendments or corrigenda and for harmonized or sector-specific updates that may affect application.

Q: Is it part of a series?

A: Yes — it is one part (Part 5) of the IEC 61508 series, which comprises Parts 1 through 7 covering general requirements, system design, hardware and software requirements, examples, guidance on applications and supporting processes for functional safety.

Q: What are the key keywords?

A: Safety integrity level (SIL), functional safety, E/E/PE systems, diagnostic coverage, probabilistic failure, safety assessment, IEC 61508.