ISO 12100 · ISO 13849-1 · IEC 62061 · IEC 61508 · IEC 61511
Risk assessment and safety function design standards.
PL vs SIL — Which Path?
The choice between Performance Level (PL) and Safety Integrity Level (SIL) depends on application domain:
| Domain | Approach | Standard | Foundation |
|---|---|---|---|
| Industrial machinery | PL (most common) | ISO 13849-1 | ISO 12100 |
| Industrial machinery (alternative) | Machinery SIL | IEC 62061 | IEC 61508 |
| Process industry | SIL | IEC 61511 | IEC 61508 |
| Generic E/E/PE safety | SIL | IEC 61508 | (foundational) |
ISO 13849-1 and IEC 62061 are alternative design routes for machinery, not a ladder. Neither one “takes over” from the other above a given integrity level. The choice is made on project requirements, the technologies in the safety function, the architecture, customer requirements, and your organisation’s established methodology.
They can also be used together on one machine — for example ISO 13849-1 for the electromechanical elements and IEC 62061 for a programmable safety controller — provided each subsystem meets the requirements of the standard it is designed under.
In both routes, the machinery risk assessment is performed per ISO 12100. The required integrity target then comes from the design standard: PLr from the ISO 13849-1 Annex A risk graph, or a SIL target from the IEC 62061 method. ISO 12100 does not itself output a PLr or a SIL.
Standards in This Family
ISO 12100 — Risk Assessment Foundation
Status: Reviewed
Foundation standard for all machinery safety. Provides a systematic process for risk assessment and risk reduction. EU machinery law requires a documented risk assessment; EN ISO 12100 is the harmonized methodology normally used to satisfy that requirement.
- Hazard identification
- Risk estimation and evaluation
- Risk reduction strategy (inherently safe design → safeguarding → information for use)
ISO 13849-1 — Performance Level (PL)
Status: Reviewed
Safety-related parts of control systems. The PL approach uses architectural categories (B, 1–4) and diagnostic coverage to determine the achievable Performance Level (PLa–PLe).
- Most common approach for industrial machinery
- Uses simplified reliability data (MTTFd, DC, CCF)
- Validated by ISO 13849-2 (validation methods)
IEC 62061 — Machinery SIL
Status: Reviewed
Functional safety for safety-related electrical control systems on machinery. Uses SIL (1–3) instead of PL. More aligned with IEC 61508 methodology but scoped to machinery.
- An alternative route to ISO 13849-1, or used alongside it on different subsystems
- Machinery applications conventionally use SIL 1 to SIL 3; SIL 4 is defined by IEC 61508 and is not used in machinery verify against the published edition
- Selected on project, architecture, customer and methodology grounds — not because a given PL or SIL is “unreachable” under ISO 13849-1
IEC 61508 — Generic Functional Safety
Status: Reviewed
The foundation standard for all functional safety. IEC 62061 and IEC 61511 both derive from IEC 61508. Multi-part standard covering E/E/PE safety-related systems across all industries.
- Parts 1–7 cover the full safety lifecycle
- Part 3 covers safety-related software
- Rarely applied directly; usually via IEC 62061 or IEC 61511
IEC 61511 — Process Industry SIS
Status: Reviewed
Application standard for safety instrumented systems (SIS) in the process industry. Covers the SIS lifecycle from concept through decommissioning.
- Applies to oil and gas, chemicals, power generation, and similar process industries
- SIF (Safety Instrumented Function) design and allocation
- Proof test interval and PFDavg calculation
- Process SIS lifecycle, SIL determination, SIS design, and operation or maintenance pages are present in the reference library
Standards Hierarchy Diagram
graph TD
ISO12100[ISO 12100
Risk Assessment] --> ISO13849[ISO 13849-1
PL approach]
ISO12100 --> IEC62061[IEC 62061
Machinery SIL]
ISO13849 --> IEC60204[IEC 60204-1
Implementation]
IEC62061 --> IEC61508[IEC 61508
Foundation]
IEC61511[IEC 61511
Process SIS] --> IEC61508
IEC61131[IEC 61131-3
PLC Software] --> IEC62061
IEC61131 --> IEC61508
This site is an independent educational reference for industrial automation standards. It paraphrases and organizes guidance in original language; it is not a substitute for the official published standards, professional engineering judgment, or legal review, and content has not been independently verified against current published editions.
Items marked Review pending await technical review against the identified edition. Items marked Planned have no reviewed source material behind them. Do not rely on this site for compliance determinations, safety-critical design decisions, or legal interpretation.