Quantitative FTA: Cut Sets and Probabilities

Date
2026-10-23
Location
Online
Host
Zach L

About this event

A live 30-minute expert session on Cut Sets and Probabilities, part of the Fault Tree Analysis (FTA) track from Critical Systems Analysis. Recurs monthly. Related topics: cut sets and probabilities · cut · sets · probabilities · fault tree analysis · top event · cut set · minimal cut set · basic event · logic gate · boolean logic · probability · quantitative analysis · qualitative analysis · safety goal · failure. Browse the whole track: Fault Tree Analysis (FTA)](https://luma.com/critical-systems-analysis?tag=fault-tree-analysis-fta)) All Fault Tree Analysis (FTA) sessions (5 more): Fault Tree Analysis (FTA) for Safety-Critical Systems](https://luma.com/critical-systems-analysis?tag=fault-tree-analysis-fta-for-safety-critical-systems)) · FTA vs FMEA: When to Use Which](https://luma.com/cr

Topics

Registration

View event page

About Fault Tree Analysis and Reliability Modeling

This online session delivers expert-led instruction on the regulatory landscape and implementation approach for Fault Tree Analysis and Reliability Modeling.

Fault Tree Analysis (FTA) models how combinations of basic failures propagate through logic gates to a defined top event, enabling qualitative insight (minimal cut sets) and quantitative estimates (probability/frequency) for safety and reliability decisions.

What it regulates

Construction of trees from top events, Boolean reduction to minimal cut sets, quantification with basic-event data, and complementary models (Markov, reliability block diagrams) where dependencies or repair matter.

Who must comply

Reliability and safety engineers demonstrating PFD/PFH for complex architectures, accident analysts, and teams justifying architecture choices in certification.

Key requirements of Fault Tree Analysis and Reliability Modeling

  • Top event definition aligned with hazard analysis
  • Gate logic (AND/OR/voting), transfer symbols, and basic events
  • Minimal cut set derivation and importance measures
  • Quantification including CCF via beta factor and time-dependent unavailability
  • Markov models for repairable or sequence-dependent architectures (1oo2D and similar)

Key concepts: Fault Tree Analysis and Reliability Modeling

Minimal cut set
The smallest combination of basic events whose joint occurrence causes the top event — single-element cut sets flag single points of failure.
1oo2 / 2oo3 voting
Redundancy architectures whose safety and availability trade-offs the models quantify.
Common cause failure modeling
Explicit basic events or beta factors representing shared-cause failures across redundant channels.
Importance measures
Rankings (Fussell-Vesely, Birnbaum) of which basic events dominate top-event probability, directing design effort.

Frequently asked questions: Fault Tree Analysis and Reliability Modeling

How do fault trees support SIL verification?

For architectures beyond simple formulas, FTA/Markov compute the average PFD or PFH from element data (λDU, DC, proof intervals, beta), providing the quantitative leg of the SIL claim.

When do I need Markov instead of a fault tree?

When behavior depends on sequences, repair, or state (degraded modes, diagnostic switchover) — for example computing PFH of a 1oo2D system with online repair — static trees misestimate what state-based models capture.

Standard information based on the published text of Fault Tree Analysis and Reliability Modeling. Event content is provided by the host. For authoritative guidance, consult the official standard body.