SIF PFDavg Calculator MVP
Inputs
Trip Initiator
Logic Solver
Final Element
Results
Reference Tables
| Preset | Architecture | λd FIT | DC | PTC | T (hr) | MTTR (hr) | β |
|---|
Study Material (How it Works)
Formulas & Assumptions
Per-channel PFD is computed as:
PFD_ind = λd · (1 − DC) · PTC · (T/2) + λd · DC · MTTR
Where λd is dangerous failure rate, DC is diagnostic coverage, PTC is proof test coverage, T is proof test interval, and MTTR is mean time to repair for detected failures.
Voting uses a β-factor model. Let p=PFD_ind, pind=(1−β)·p. Then:
- 1oo1: PFD = p
- 1oo2: PFD ≈ β·p + (pind)²
- 2oo2: PFD ≈ β·p + [1 − (1 − pind)²] = β·p + 2pind − (pind)²
- 2oo3: PFD ≈ β·p + [3 pind² − 2 pind³]
SIF PFDavg is the sum of voted PFDs for Initiator + Logic Solver + Final Element.
How to Use
- Pick λd units (FIT or 1/hr). Changing this converts your λd inputs in place.
- Enter each subsystem’s values or select a preset from Reference Tables and click Use Selected Row.
- Click Compute. Review the Results and subsystem details.
- Export PDF or Excel for reporting. PDF downloads directly—no preview is shown.
Notes
Values are illustrative; confirm against your project’s reliability data sources and corporate standards.
Self Tests
Disclaimer: Educational Use Only. This SIF PFDavg calculator is provided solely for training and educational purposes and must not be used to design, operate, or modify real-world safety instrumented systems. It is not a substitute for professional engineering judgment, formal SIL verification/validation, or compliance assessments. No warranty—express or implied—is given regarding accuracy, completeness, or fitness for any purpose. You are responsible for verifying all inputs, assumptions, methods, and outputs against applicable standards (including IEC 61511 and IEC 61508), manufacturer data, and your company’s approved practices. The authors and distributors accept no liability for any decisions, actions, losses, or damages arising from use of this tool. By using the calculator, you acknowledge and agree to these terms.