Introduction
In high-hazard industries like oil & gas, petrochemicals, and refineries, fire and explosion risks pose a significant threat to life, assets, and environmental sustainability. Over the decades, catastrophic incidents such as Piper Alpha (1988), Jaipur IOC Terminal Fire (2009), and Vizag LG Polymers Gas Leak (2020) have shown the importance of systematic hazard analysis.
One of the most powerful tools in a process safety engineer’s arsenal is the Fire and Explosion Risk Analysis (FERA) study.
FERA is a structured methodology that assesses the probability and consequences of fire and explosion scenarios. The results guide facility layout, fire protection strategies, risk reduction measures, and emergency planning.
What is a FERA Study?
FERA (Fire and Explosion Risk Analysis) is a quantitative or semi-quantitative study that assesses:
- Likelihood of fire and explosion events
- Consequence severity (thermal radiation, overpressure)
- Risk to personnel and equipment
- Need for mitigation measures (barriers, spacing, active protection)
It is often carried out during the FEED (Front-End Engineering Design) or Detailed Engineering stage and forms a key input for:
- Facility layout optimization
- Fireproofing decisions
- Siting of control rooms and occupied buildings
- Emergency Response Plan (ERP)
👉 Internal Link: List of Process Safety Studies
When is FERA Required?
- During greenfield or brownfield design
- For regulatory approvals (PESO, OISD, local authorities)
- Before implementing hazardous modifications (MOC)
- In support of QRA, SIL, F&G Mapping, and HAZOP
Scope of a FERA Study
| Element | Description |
|---|---|
| Hazardous Scenarios | Fire (pool, jet), explosion (VCE, BLEVE), flash fire |
| Event Frequencies | Derived from failure databases (OREDA, EI) |
| Thermal & Overpressure Effects | On humans, equipment, and structures |
| Risk Ranking | Based on individual and societal risk |
| Recommendations | Mitigation, spacing, fireproofing, shutdown logic |
Types of Fires and Explosions Considered
🔥 Fire Scenarios:
- Jet Fire: High-pressure leak ignites – long, narrow flame.
- Pool Fire: Spilled liquid forms a pool and ignites.
- Flash Fire: Vapor cloud ignites momentarily.
- Torch Fire: Controlled burn at flare stack.
- Fireball (BLEVE): Pressurized vessel explodes, creating a fireball.
💥 Explosion Scenarios:
- Vapor Cloud Explosion (VCE): Flammable vapor cloud ignites with confinement.
- BLEVE: Boiling Liquid Expanding Vapor Explosion – typical for LPG vessels.
- Dust Explosion: Fine solid particulates in air ignite explosively (rare in oil & gas).
Governing Codes and Guidelines
| Standard | Description |
|---|---|
| API 521 | Pressure-relieving and Depressuring Systems |
| API 505 / NFPA 30 | Flammable Liquids Classification |
| CCPS Guidelines | Fire and Explosion Risk Assessment Procedures |
| EI Model Code | Ignition source control |
| OISD 118 / OISD 150 | Fire Protection and Risk Analysis |
| ISO 13702 | Control and mitigation of fires and explosions |
👉 Internal Link: Codes and Standards for Process Safety
Methodology of FERA Study
Step 1: Data Collection
- Process descriptions and P&IDs
- Equipment list (vessels, pumps, exchangers, tanks)
- Material Safety Data Sheets (MSDS)
- Facility layout drawings
- Design and operating conditions
Step 2: Hazard Scenario Identification
- Identify credible leak sources (valves, flanges, pumps)
- Define hole sizes (small, medium, large)
- Define initiating events (LOPA, HAZOP output)
- Consider wind speed, direction, ambient temperature
Step 3: Consequence Modeling
Use dispersion and radiation modeling software such as:
| Tool | Use |
|---|---|
| PHAST | Jet/pool fires, VCEs, flash fires |
| ALOHA | Emergency dispersion planning |
| FLACS | CFD-based explosion modeling |
| EFFECTS | Jet/pool fires and explosion impact |
| SAFETI | Societal risk and consequence analysis |
Model parameters:
- Fire: Thermal radiation contours (kW/m²)
- Explosion: Overpressure (bar), impulse
- Impact zones: Fatality thresholds, escalation
Thermal Radiation Criteria
| Radiation Level (kW/m²) | Effect |
|---|---|
| 1.2 | Pain in 20s; safe evacuation possible |
| 4.0 | First-degree burns in 20s |
| 6.3 | Second-degree burns in 20s |
| 12.5 | Fatality within 1 min |
| 37.5 | Equipment damage threshold (steel rupture) |
Overpressure Effects
| Overpressure (bar) | Impact |
|---|---|
| 0.02 – 0.03 | Window breakage |
| 0.14 | Human injury, panel damage |
| 0.3 | Structural damage begins |
| 0.7 | Reinforced structures fail |
| >1.0 | Catastrophic failure of equipment |
Risk Assessment Metrics
A. Individual Risk
- Fatality probability for a person exposed continuously at a location.
- Acceptable limit: 1×10⁻⁴ /year (India), 1×10⁻⁶ /year (Europe)
B. Societal Risk (FN Curve)
- Frequency (F) vs. number of fatalities (N)
- Used for large installations or urban proximities
Risk Ranking & Classification
| Risk Level | Criteria | Action |
|---|---|---|
| Intolerable | High frequency + severe consequence | Redesign or eliminate |
| ALARP | Medium risk, tolerable if justified | Reduce where practicable |
| Acceptable | Negligible frequency and severity | No action needed |
Key Outputs of FERA
- List of credible fire/explosion scenarios
- Event frequencies (per year)
- Thermal and overpressure contour plots
- Risk contours (individual and societal)
- Fatality zones and exposure assessments
- Fireproofing, spacing, blast wall recommendations
- Inputs for Fire & Gas Mapping, QRA, EERA
👉 Internal Link: QRA vs FERA vs EERA – What’s the Difference?
Real-World Case Study – LPG Storage Facility
Facility: LPG bullets with 150 m³ capacity
Material: Propane (flammable, pressurized)
FERA Findings:
- BLEVE scenario leads to 37.5 kW/m² radiation up to 110 meters
- Overpressure exceeds 0.3 bar at 85 meters during VCE
- Existing control room is 60 meters away → unsafe
- Recommended:
- Relocation of control room
- Passive fire protection for pipelines
- Fireproofing of supports and valves
- Automatic deluge system with redundancy
Recommendations from a FERA Study
| Category | Example |
|---|---|
| Layout | Relocate buildings, increase separation |
| Fire Protection | Add deluge, foam monitors, hydrants |
| Passive Protection | Fireproofing, blast walls |
| Shutdown Systems | ESD, isolation valves |
| Occupied Building Siting | Control room blast resistance |
| Detectors | Optimized F&G mapping input |
| ERP | Muster point repositioning |
Common Pitfalls to Avoid
| Pitfall | Fix |
|---|---|
| Generic assumptions for leak sizes | Use realistic failure data |
| Ignoring cumulative risk | Include societal risk evaluation |
| Lack of cross-verification | Use multiple software outputs |
| Ignoring future expansion | Keep buffer zones in design |
| Copy-paste FERA | Customize to site-specific risks |
How FERA Integrates With Other Safety Studies
| Study | Relationship with FERA |
|---|---|
| HAZOP | Identifies initial scenarios |
| SIL Study | Validates the need for shutdown on detection |
| QRA | Provides overall risk profile |
| EERA | Aligns emergency evacuation strategy |
| Fire & Gas Mapping | Inputs on fire zones and hazard types |
👉 Internal Link: HAZOP Study Guide
India-Specific Notes
- PESO and OISD often require FERA for licensing LPG and POL terminals.
- Local fire authorities refer to OISD-150 and factory act rules for FERA acceptance.
- Site-specific modeling is increasingly mandatory in public safety-sensitive zones (Mumbai, Vizag, Ahmedabad).
FAQs
Q1: Is FERA mandatory in India?
Yes, for most hazardous installations involving flammable/explosive materials, FERA is part of the risk assessment package for statutory approvals.
Q2: How long does a FERA take?
Typically 2–6 weeks depending on the complexity and number of scenarios.
Q3: What’s the difference between FERA and QRA?
QRA covers a broader risk landscape (toxics, fatalities, evacuation), whereas FERA focuses specifically on fire and explosion.
Q4: Can FERA be reused for revamp projects?
Partially, if process conditions haven’t changed. However, it must be revalidated.
Conclusion
FERA (Fire and Explosion Risk Analysis) is not just a deliverable—it’s a critical layer in your process safety lifecycle. Whether you’re designing a new facility, modifying an existing one, or preparing for regulatory audits, a robust FERA study gives you the insight, foresight, and confidence to operate safely.
It enables proactive decisions, minimizes risk exposure, and ensures compliance with local and international norms. In today’s environment where safety and reputation go hand in hand, a well-executed FERA could be the difference between a near-miss and a disaster.
