Event Tree Analysis (ETA) – Software
Layer of Protection Analysis (LOPA)
Event Tree Analysis
The Mantua Group delivers Event Tree Analysis (ETA) using RWB — modelling accident sequences from initiating events through safety function success or failure to final consequences, enabling risk quantification and Safety Integrity Level determination for safety-critical systems.
- Initiating event frequency modelling
- Safety function success/failure branches
- Consequence category assignment
- Sequence probability calculation
- Linked fault trees for safety functions
- LOPA and SIL determination support
- Uncertainty propagation
- IEC 61508 and IEC 61511 compliant
Integrated since 2009
Implementation
Software Deployed
Professionals on Staff
Why Choose RWB Event Tree Analysis
Event trees model the forward propagation of consequences from an initiating event — the complementary perspective to fault trees which work backwards from the undesired outcome. Together they form the complete accident sequence logic required by functional safety and nuclear safety standards.
Initiating Event Modelling
Define initiating events — equipment failures, process deviations, human errors — with their frequency of occurrence. Event tree branches from each initiating event represent the success or failure of independent protection layers, barriers and safety functions that determine the final consequence.
Sequence Probability and Frequency
Calculate the frequency of each accident sequence — initiating event frequency multiplied by the probability of each branch outcome along the sequence path. Sequences are assigned to consequence categories (safe state, minor release, major release, catastrophic) and their frequencies summed per category.
LOPA and SIL Determination
Layer of Protection Analysis (LOPA) uses simplified event tree logic to determine the required risk reduction from each protection layer. Where risk reduction targets cannot be met by non-instrumented protections, the required Safety Integrity Level (SIL) for the Safety Instrumented Function (SIF) is determined.
Linked Fault Trees for Safety Functions
Link safety function branches in the event tree directly to fault tree models of the protection system. The unavailability of each protection layer — calculated from its fault tree — flows automatically into the event tree sequence calculation, maintaining a consistent model across both analysis types.
Consequence Assignment and Risk Matrix
Assign each event tree sequence to a consequence category — safety, environmental, production, financial — and plot sequence frequencies against consequence severity on a risk matrix. Demonstrate compliance with the corporate or regulatory risk acceptance criteria for each consequence category.
Functional Safety and SIS Design Support
TMG delivers ETA and LOPA studies supporting Safety Instrumented System (SIS) design — determining SIL targets, verifying that the proposed SIS architecture achieves the required risk reduction, and producing the evidence required for IEC 61508 / IEC 61511 compliance demonstration.
How The Mantua Group Works With You
Every organisation is at a different point in its reliability journey. We match our engagement to where you are — from full hands-on delivery through to training your team to self-sufficiency.
We Do — You Learn
TMG leads the full implementation with your team participating throughout to build genuine capability alongside delivery. Ideal for first-time deployments or when internal resources are stretched.
We Do Together
Our most common model. TMG engineers work alongside your maintenance, operations and engineering teams in structured workshops — combining their asset knowledge with our analytical methodology to produce models your team trusts and owns.
We Train — You Do
For teams building internal capability, TMG delivers structured training covering software operation, methodology, and integration. Available as public courses or dedicated onsite delivery across Australia and the United States.
Independent Review & Audit
TMG provides independent technical review of existing models and regulatory submissions — assessing methodology rigour, data quality and standards compliance. Particularly valuable ahead of AER determinations, investment board presentations or safety audits.
Model Your Accident Sequences
Whether you need event tree analysis for a functional safety case, LOPA for SIL determination, or your team trained in ETA methodology — The Mantua Group is ready to help.
Contact Us Today+61 (0) 439 118 714
+1 (330) 294-3744