IEC 61508-6-2010 PDF

Full title and description

Functional safety of electrical/electronic/programmable electronic safety-related systems — Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3. This part provides guidance, worked examples and explanatory material to help apply the hardware and software requirements given in Parts 2 and 3 of IEC 61508.

Abstract

IEC 61508-6:2010 is an informative guidance document accompanying the normative requirements in IEC 61508-2 (hardware) and IEC 61508-3 (software). It contains explanatory annexes (A–E) with an overview of application steps, example calculations for hardware failure probabilities, worked examples for diagnostic coverage and software safety integrity, and methods for assessing common-cause failures. The second edition (2010) replaces the earlier edition and consolidates clarified techniques and worked examples for use in SIL assessments.

General information

• Status: Published — current edition (second edition, 2010).
• Publication date: 30 April 2010.
• Publisher: International Electrotechnical Commission (IEC).
• ICS / categories: 25.040.40 (Industrial process measurement and control).
• Edition / version: Edition 2.0 (2010).
• Number of pages: 237 pages (English/French).

Scope

This part offers guidance on applying the requirements of IEC 61508-2 and IEC 61508-3 to electrical/electronic/programmable electronic safety-related systems. It is informative rather than normative and focuses on explanation, worked examples and calculation techniques for probability of dangerous failures, diagnostic coverage, common-cause failure quantification and software safety-integrity table applications (with examples for SIL 2 and SIL 3). The annexes provide stepwise application guidance and modelling techniques useful for designers, assessors and auditors.

Key topics and requirements

• Guidance on applying IEC 61508-2 (hardware) and IEC 61508-3 (software) requirements.
• Annex A: overview of application steps and interaction with Parts 2 and 3.
• Annex B: example techniques for calculating probabilities of hardware failure (PFD/PFH) using reliability methods.
• Annex C: worked example for diagnostic coverage and safe-failure fraction calculations.
• Annex D: methodology for quantifying the effect of hardware-related common cause failures.
• Annex E: worked software safety-integrity examples for SIL 2 and SIL 3.
• Illustrative modelling approaches: reliability block diagrams, fault trees and other analytical techniques for safety assessments.

Typical use and users

Used by functional safety engineers, system designers, software developers working on safety-related systems, safety assessors, certification bodies, and project managers responsible for demonstrating compliance with IEC 61508 hardware and software requirements. The guidance is commonly used during SIL determination, safety lifecycle planning, reliability modelling and independent assessment activities.

Related standards

IEC 61508-6 is one part of the IEC 61508 series (Parts 1–7) covering functional safety for E/E/PE systems; it supports the normative requirements in IEC 61508-2 and IEC 61508-3 and is often used alongside national/adopted versions (for example EN/BS/DIN variants). Other related documents include IEC/TR 61508-0 (background and overview) and the other parts of the IEC 61508 family used for management, hardware, software, measures and guidance.

Keywords

Functional safety, IEC 61508, safety integrity level (SIL), diagnostic coverage, probability of dangerous failure (PFD/PFH), common-cause failure (CCF), software safety, reliability modelling, safety lifecycle.

FAQ

Q: What is this standard?

A: IEC 61508-6:2010 is the guidance part of the IEC 61508 functional safety standard series; it provides explanatory material and worked examples to help apply the hardware and software requirements in Parts 2 and 3.

Q: What does it cover?

A: It covers application guidance, example calculations for hardware failure probabilities, worked diagnostic coverage examples, methods for common-cause failure assessment and software safety-integrity worked examples (not normative requirements). The content is organised in informative annexes (A–E).

Q: Who typically uses it?

A: Functional safety engineers, designers of safety-related E/E/PE systems, software engineers working on safety-critical code, safety assessors and certification bodies use this document as practical guidance when implementing or assessing IEC 61508 Part 2 and Part 3 requirements.

Q: Is it current or superseded?

A: The current (second) edition was published on 30 April 2010 and replaced the earlier edition; it remains the valid edition published in 2010 (stability date shown by the IEC webstore is 2027). For historical context the previous edition (first edition) dates from the late 1990s/2000s and was superseded by the 2010 edition.

Q: Is it part of a series?

A: Yes — IEC 61508-6 is one part of the IEC 61508 family (Parts 1 through 7), which together define functional safety requirements, measures and guidance for electrical, electronic and programmable electronic safety-related systems.

Q: What are the key keywords?

A: Functional safety, SIL, diagnostic coverage, PFD/PFH, common-cause failure, software safety integrity, reliability modelling.