Engineering knowledge · IEC 61508 · IEC 61511

Functional safety knowledge, organised for engineering work.

Follow a subject from first principles to the decision, evidence and tool used in practice. Each guide has its own shareable reference page.

Start with the task

Choose an engineering path

Learn the foundations

SIS, SIF, SIL and the safety lifecycle.

Determine required SIL

Build the risk-reduction basis before design.

Design and verify a SIF

Connect architecture, data and the three gates.

Specify and maintain

Write testable requirements and preserve assumptions.

Start here

Build the right foundation

Start here8 min

Functional safety fundamentals

Understand functional safety, SIS, SIF, SIL and the lifecycle thread that connects risk to operation.

Read guide

Risk and requirements

Risk and requirements10 min

Determining the required SIL

Build the risk-reduction basis with a defined scenario, tolerable-risk criterion and reviewable assumptions.

Read guide

Design

Design10 min

Designing a Safety Instrumented Function

Translate the safety requirement into sensors, logic solver interfaces, final elements and a testable safe action.

Read guide

Verification

Verification11 min

Failure data for SIL verification

Select, classify and document failure-rate data without losing its application conditions or provenance.

Read guide Verification9 min

PFDavg

Low-demand probability of failure, SIL bands and the SILProof algebraic and Markov basis.

Read guide

Architecture

Architecture8 min

Route 1H

Hardware architecture using device type, safe failure fraction and hardware fault tolerance.

Read guide Architecture8 min

Route 2H and Table 6

Field-reliability evidence, hardware fault tolerance and the distinction from IEC 61511 Table 6.

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Requirements

Requirements11 min

Writing a SIF Safety Requirements Specification

Write one controlled SIF requirement set that can drive design, verification, testing and validation.

Read guide

Operation and maintenance

Operation and maintenance10 min

Proof testing and restoration assumptions

Connect proof-test interval, coverage, diagnostics and repair assumptions to a procedure that can actually be executed.

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Assurance

Assurance8 min

Engineering basis and review guide

Understand scope, assumptions, engine methods and the checks needed before relying on a result.

Read guide

Reference

Reference6 min

Functional safety glossary

Plain engineering definitions for the terms used across SIL determination, SIF design and verification.

Read guide