Simplified Iec Risk Assessment Calculator Sirac !!exclusive!! ✨

Simplified IEC Risk Assessment Calculator (SIRAC)

The Simplified IEC Risk Assessment Calculator (SIRAC) is a compact, practical tool designed to help engineers and safety professionals perform IEC-style functional safety risk assessments quickly and consistently. It implements core concepts from IEC 61508/61511 in a streamlined way, focusing on clarity and ease of use for common industrial control scenarios.

What SIRAC Does

SIRAC streamlines the risk assessment process by automating the core logic of IEC 62061 and its companion, ISO 13849-1. Instead of wrestling with multi-page worksheets, users answer a handful of structured questions about a machine hazard:

Severity of Injury (S): Minor, Serious, or Death/Loss of Limb.
Frequency of Exposure (F): Rare (e.g., monthly) or Frequent (e.g., hourly).
Possibility of Avoidance (P): Possible (e.g., with warning systems) or Impossible (e.g., sudden start-up).

From these inputs, SIRAC calculates a Risk Level (Low, Medium, High) and—crucially—recommends a required Performance Level (PLr) or Safety Integrity Level (SIL) for the safety-related control system. simplified iec risk assessment calculator sirac

Step 1: Identify Machine Limits

Before touching the calculator, define the machine's lifecycle (transport, installation, operation, cleaning, maintenance). SIRAC is only accurate if you know who is exposed and when.

The Spreadsheet Method (Free, Risky)

Pros: Free, transparent, customizable.
Cons: No version control, easy to corrupt formulas, no audit trail.

Key Concepts

Hazard: A potential source of harm (e.g., overpressure, lost containment).
Risk: Combination of consequence severity, frequency of exposure, and probability of avoidance.
SIF (Safety Instrumented Function): A function designed to prevent or mitigate the hazard.
Demand Mode vs. Continuous Mode: Demand mode = occasional demand (e.g., emergency shutdown); continuous = ongoing risk reduction (e.g., gas detection).
Risk Reduction Factor (RRF) and Probability of Failure on Demand (PFDavg): Core metrics mapping to SIL targets per IEC standards.

Part 9: Frequently Asked Questions (FAQ)

Q: Is SIRAC an official ISO/IEC standard? A: No. "SIRAC" is a colloquial name for the simplified application of the IEC 62061 risk graph. The standard does not use the acronym, but the industry does. Severity of Injury (S): Minor, Serious, or Death/Loss

Q: Can I use SIRAC for a machine I built in-house? A: Yes. In fact, in-house machine builders must use it more rigorously than OEMs because they lack type-examination certificates.

Q: How often must I re-run the SIRAC assessment? A: Whenever the machine is modified (MOC – Management of Change) or every 5 years for general review. From these inputs, SIRAC calculates a Risk Level

Q: What if SIRAC says "No safety requirement"? A: That means the risk is negligible. However, you must still document that fact. You cannot simply ignore it.

Mapping to IEC Targets

Convert Risk Score to required RRF/PFDavg using predefined mappings depending on demand mode:
- SIL 1: PFDavg 0.1–0.01 (RRF 10–100)
- SIL 2: PFDavg 0.01–0.001 (RRF 100–1000)
- SIL 3: PFDavg 0.001–0.0001 (RRF 1000–10000)

Purpose

Estimate required Safety Integrity Level (SIL) or Safety Performance Level (SPL) equivalents for safety functions.
Provide a fast, repeatable risk ranking to prioritize mitigation.
Translate qualitative risk descriptions into quantitative targets for safety instrumented functions (SIFs).

Simplified Assessment Steps

Identify hazard and define the safety function.
Estimate consequence severity (e.g., Minor, Serious, Fatal).
Estimate exposure frequency (e.g., Rare, Occasional, Frequent).
Estimate probability of avoidance (e.g., Very Likely, Likely, Unlikely).
Combine these inputs via a simple scoring matrix to derive a Risk Score.
Map Risk Score and demand mode to required SIL (or equivalent RRF/PFDavg).
Recommend architectural measures, diagnostics, and proof test intervals to meet required risk reduction.