Reference for CCPS (2001) Layer of Protection Analysis methodology. Load this skill when lopa-report-generator, ipl-qualification-assessor, or another action skill needs to verify LOPA methodology, IPL qualification criteria, or risk tolerance frameworks. Not intended as a standalone user tool.
This skill provides reference material for CCPS (2001) Layer of Protection Analysis: Simplified Process Risk Assessment, published by the Center for Chemical Process Safety of the American Institute of Chemical Engineers. It ensures accurate technical information when producing LOPA reports, risk assessments, IPL qualification evaluations, SIL determination studies, and process safety analyses.
Read the relevant section file(s) based on the technical domain of the query:
| File | Coverage | When to Read |
|---|---|---|
sections/s01-overview-methodology.md | Chapter 2: LOPA overview, 5-step methodology, when to use LOPA, cause-consequence pairs, Figure 2.1 layers of defence | Any query about LOPA process, methodology steps, when LOPA is appropriate, relationship to PHA/HAZOP |
sections/s02-consequences-severity.md | Chapter 3: Consequence categorisation (Tables 3.1, 3.2), four methods for consequence evaluation, severity classification | Consequence assessment, severity categories, category definitions, methods for evaluating consequences |
sections/s03-initiating-events.md | Chapter 5: Initiating event frequencies (Table 5.1 complete), Table 5.2 notation formats, enabling events and conditions, types of initiating events | Initiating event frequency lookup, equipment failure rates, BPCS failure, operator error rates, enabling events |
sections/s04-ipl-identification.md | Chapter 6: IPL definition, 3 qualification rules, IPL characteristics, Table 6.1 non-IPL safeguards, Table 6.2 dependent failure causes, Table 6.3 passive IPLs, Table 6.4 active IPLs, Table 6.5 human action IPLs, SIL 1–4 PFD ranges, preventive vs mitigation IPLs, BPCS Approach A/B | IPL qualification, PFD lookup, safeguard assessment, SIL determination, independence evaluation, common cause analysis |
sections/s05-scenario-frequency.md | Chapter 7: Equation 7-1, mitigated scenario frequency calculation, conditional modifiers (P_ignition, P_personnel, P_fatality), worked examples | Frequency calculations, Equation 7-1, conditional modifiers, mitigated frequency determination |
sections/s06-risk-decisions.md | Chapter 8: Risk decision methods (matrix, numerical criteria, IPL credits, expert judgment, cost–benefit), Table 8.1 risk matrix, Table 8.2 IPL credit requirements, Equation 8-1 cumulative risk, LOPA summary sheet format (Tables 8.3, 8.4), Section 8.9 cautions | Risk decision making, risk matrix lookup, IPL credit determination, tolerable risk comparison, LOPA documentation |
sections/s07-risk-tolerance-criteria.md | Appendix E: Industry risk tolerance criteria data, typical LOPA criteria (per scenario and cumulative), company examples (ICI, Rohm and Haas), Notes 1–3 | Risk tolerance criteria, maximum tolerable risk, negligible risk, workforce vs public criteria, per-scenario vs cumulative |
sections/s08-high-demand-mode.md | Appendix F: High demand mode calculations, Equations F-1 and F-2, low demand vs high demand transition, worked examples | High initiating event frequency scenarios, demand rate exceeding test frequency, high demand mode equations |
sections/s09-glossary-references.md | Glossary of Terms, SIL table (demand mode), key definitions (BPCS, CPQRA, IPL, LOPA, PFD, PHA, SIF, SIL, SIS), References list | Terminology definitions, SIL/PFD relationship table, citation verification, reference list |
| Query Topic | Primary Section(s) | Coverage |
|---|---|---|
| LOPA methodology and process | s01 | 5-step process, when to use, cause-consequence pairs |
| Consequence severity categories | s02 | Tables 3.1, 3.2, four evaluation methods |
| Initiating event frequency values | s03 | Table 5.1 complete (20+ event types with ranges and screening values) |
| Equipment failure rates | s03 | Pressure vessels, piping, tanks, gaskets, pumps, cooling water |
| BPCS instrument loop failure | s03 | Table 5.1 BPCS entries |
| Human error / operator failure rates | s03, s04 | Table 5.1 operator failure, Table 6.5 human action IPLs |
| IPL qualification rules | s04 | Three rules: effective, independent, auditable |
| What is NOT an IPL | s04 | Table 6.1 (14 safeguard types that usually do not qualify) |
| Common cause / dependent failure | s04 | Table 6.2 causes of dependent failure |
| Passive IPL PFD values | s04 | Table 6.3 (dike, drainage, open vent, fireproofing, blast wall, ISD, arrestors) |
| Active IPL PFD values | s04 | Table 6.4 (relief valve, rupture disc, BPCS, SIL 1–4) |
| Human action IPL PFD values | s04 | Table 6.5 (three response time categories) |
| SIL / PFD relationship | s04, s09 | SIL 1–4 PFD ranges in Table 6.4 and Glossary |
| Mitigated frequency calculation | s05 | Equation 7-1, conditional modifiers |
| Risk matrix interpretation | s06 | Table 8.1 with action zones |
| IPL credit requirements | s06 | Table 8.2 credit requirements by consequence category |
| Risk tolerance criteria | s07 | Appendix E typical LOPA criteria, industry examples |
| High demand mode | s08 | Equations F-1, F-2, transition point, worked examples |
| LOPA summary sheet format | s06 | Tables 8.3, 8.4 complete worked examples |
| Glossary / definitions | s09 | All key terms with CCPS definitions |
Note: This skill covers CCPS (2001) only. For IEC functional safety standards, refer to IEC 61508 and IEC 61511. For Australian WHS legislation context, use the safetysure-whs-legislation plugin (whs-act-checker and whs-regulation-checker skills).