By name: safety-engineering-expert version: 1.0.0 description: Expert-level chemical process safety covering HAZOP, LOPA, relief system design, consequence modeling, inherently safer design, and process safety management. author: luo-kai tags: [process safety, HAZOP, LOPA, relief valves, PSM, inherently safer design]
Safety Engineering Expert
Before Starting
- New design or operating plant review?
- Which hazard analysis method? (HAZOP, FMEA, What-If)
- Risk assessment or relief system design?
Core Expertise Areas
Hazard Analysis
HAZOP: hazard and operability study, guide words applied to design intent. Guide words: no, more, less, as well as, part of, reverse, other than. FMEA: failure mode and effects analysis, bottom-up equipment failure analysis. What-if: structured brainstorming, less systematic than HAZOP. Bow-tie: causes on left, top event center, consequences on right, barriers shown.
LOPA
LOPA: layers of protection analysis, semi-quantitative risk assessment. Initiating event frequency: starting point for scenario frequency. Independent protection layers: each IPL must be independent and auditable. PFD: probability of failure on demand for each IPL. Risk tolerance: compare mitigated frequency to tolerable risk criteria.
Relief System Design
Relief valve: spring-loaded, opens at set pressure, reclosed on pressure reduction. Rupture disk: one-time device, fails at rated burst pressure. Sizing: API 520 and 521 for pressure relief device sizing and selection. Credible scenarios: blocked outlet, fire, thermal expansion, reflux failure. Disposal: flare, scrubber, or containment for relief discharge.
Process Safety Management
PSM: OSHA 1910.119 for highly hazardous chemicals above threshold quantities. PHA: process hazard analysis required every 5 years. MOC: management of change, review all changes before implementation. Incident investigation: root cause analysis, findings and recommendations tracked.
Best Practices
- Apply inherently safer design principles to eliminate hazards at source
- Involve operations and maintenance in HAZOP teams
- Never bypass or defeat safety systems without formal risk assessment
- Track all HAZOP action items to closure before startup
Common Pitfalls
| Pitfall | Fix |
|---|---|
| IPLs not truly independent | Verify each IPL has separate initiation and hardware |
| Missing fire case for relief sizing | Fire case often governs vessel relief requirement |
| Inadequate MOC for small changes | Even small changes can introduce new hazards |
| HAZOP action items not closed | Track all items with owner and due date to closure |
Related Skills
- process-control-expert
- process-design-expert
- reaction-engineering-expert