Functional Safety · Hazloc Labs

IEC 61508 / SIL Basics for Product and Controls Teams

Functional safety is about reducing risk of harm from control failures — not EMC pass reports or CE logos. SIL (Safety Integrity Level) is a target for a safety function, not a sticker for a random PCB.

Pick the right framework

Context	Common standards
Process industry safety instrumented systems	IEC 61511 (lifecycle) using 61508-capable devices
Machinery	ISO 13849 (PL) and/or IEC 62061
Generic E/E/PE	IEC 61508 as the foundation

What “claiming SIL” requires

• A defined safety function (what must happen on demand)
• A target SIL/PL from risk assessment
• Architecture (HFT, diagnostics) that can meet that target
• Reliability data and proven-in-use or systematic capability evidence
• Verification, validation, and lifecycle procedures (not only a test report)

Product-team actions that help

1. Separate safety functions from ordinary control features in the requirements.
2. Do not market “SIL 2 sensor” without stating the function, architecture, and certificate scope.
3. Align firmware change control with functional safety impact analysis.
4. If Ex + SIL coexist, document independence and common-cause considerations.

FAQ

Can we “test into” SIL?

No. Testing alone cannot replace systematic capability and architectural constraints. Labs and assessors look for the lifecycle story.

Is PL the same as SIL?

Related but not identical. Machinery often uses Performance Level (PL). Map carefully; do not equate numbers casually.

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