Safety Engineering Expert

---
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
1. New design or operating plant review?
2. Which hazard analysis method? (HAZOP, FMEA, What-If)
3. 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