Swiss Cheese Risk Analyzer

Dashboard

Active Scenario

No scenario defined yet. Go to Scenarios tab.

Residual Risk Gauge

—

Barrier Summary

No barriers added yet.

Project Information

Study Title

Document No.

Revision

Facility / Site

Process Unit / Area

Location

Study Date

Next Review Date

HAZOP Reference No.

P&ID Drawing No.

Risk Tolerance Criteria

Study Objective / Scope

Study Team

#	Name	Role / Title	Company / Dept	Email	Phone	Discipline

Add Team Member

Name

Role / Title

Company / Dept

Phone

Discipline

Hazard Scenarios

Barrier Layers

⬅ Prevention Barriers (Pre-Top-Event)

Mitigation Barriers (Post-Top-Event) ➡

LOPA – Layer of Protection Analysis

Select a scenario to run LOPA calculations.

Swiss Cheese Visualization

🟡 Cheese slice = Barrier layer ⚫ Hole = Vulnerability (more = lower effectiveness) 🟫 Plug = Add-on control ➡ Red arrow = Hazard trajectory Top stripe = Barrier type color

—

LOPA Reference — IPL Credits & Standards

Standard IPL Credit Factors (CCPS / IEC 61511)

Initiating Event Demand Rates (Typical)

Initiating Event	Typical Frequency (/yr)	Notes

LOPA Methodology Notes

Independence requirement: IPLs must be independent of the initiating event and of each other. A BPCS loop that participates in the initiating event cannot be credited as an IPL for that scenario.

Mitigated consequence frequency: f_mitigated = f_IE × PFD₁ × PFD₂ × … × PFD_n × Conditional Modifier

Risk gap: If f_mitigated > Risk Tolerance Criterion, additional IPLs are required. The required risk reduction = f_mitigated / RTC.

IPL credit limits: CCPS LOPA guidance typically limits combined IPL credit to 10⁻⁵ for a single scenario. Human IPLs require: clear alarm/indication, sufficient response time (>10 min), trained operators, and documented procedures.

Standards references: CCPS "Layer of Protection Analysis" (2001), IEC 61511-3:2016, OSHA PSM 29 CFR 1910.119, API RP 14C, NFPA 652/654, ISO 45001.