Transit Vehicle Design Standards and Risk Analysis on Fire Development in Rapid Transit Vehicles Adrian Milford Sereca - a Jensen Hughes Company, Project Engineer Vancouver, BC, Canada
Motivation Design fire size: important parameter in the design of emergency ventilation systems Factors: materials, train geometry, ignition source characteristics, ventilation conditions, suppression Potential impact on life safety (system performance) Construction and equipment costs
Important Factors: Fire Development 1. Material ignition and burning properties Flame spread, smoke development characteristics 2. Ignition source characteristics Potential severity, locations, exposure to combustibles Likelihood of occurrence 3. Conditions for fire development Configuration of materials, ventilation conditions Operational response, detection/intervention
1. Material Fire Properties Transit vehicle design standards ie: NFPA 130, EN 45545 Testing methodology, performance criteria based upon material function Flame spread, smoke developed Fire hardened materials
1. Material Fire Properties - Example EN 45545 3 hazard levels assigned based upon 4 operational categories and 4 design categories
1. Material Fire Properties Side Walls Example EN 45545 NFPA 130 Flame spread radiant panel Smoke generation Flame spread Heat release cone calorimeter Smoke generation
2. Ignition Sources Exterior fire development Train equipment, vehicle systems separated from interior Interior fire development Train equipment/systems not separated from interior Limited by vehicle design standard requirements Introduced combustibles/ignition sources Generally potential for greatest fire size Severity and likelihood - Risk
2. Ignition Sources - Interior Item Peak HRR [kw] Approximate Peak Burning Duration [s] Lighter or match < 1 - Polyethylene wastebasket (0.6 kg) filled with shredded paper (0.2 kg) 15 100-200 Pillow with 0.65kg of polyurethane foam 40 100 Luggage filled with clothes 120 (hard suitcase) 25 (soft suitcase) 1000 Two men s jackets 75-85 10-20 Trash bags filled with paper (1.17kg total) 140 (1 bag - 1.17 kg) 100 Amtrak trash bags from overnight trains (1.8-9.5 kg) 280 (2 bags - 2.34 kg) 300 20 350 (3 bags - 3.51 kg) 100 30 260 10-400 Range ~1 kw to 350 kw, most likely sources are minor Extreme ignition sources flammable liquids
3. Conditions for Fire Development Ignition source sufficient to ignite exposed materials Fire development undetected/no intervention occurs in incipient stages Material configuration and ventilation conditions facilitate spread Operational response Train remains operational or is disabled? Fuel configuration, ventilation, suppression response
How are Design Fire Sizes Estimated? Traditional methods Typically assume 1 car is fully burning Summation of all vehicle material heat release rates or available ventilation (post-flashover) Assumptions based upon historical events and testing Advanced methods pyrolysis, prescribed material burning rate modelling Skilled user knowledge, important material inputs required Model parameter uncertainty, limitations, validation
Traditional Fire Estimation Limitations relative to key factors: 1. Historical fire events/testing largely involve materials that do not comply with current design standards 2. No ignition source context 3. Propensity for fire spread not included, no risk context Further limitations Fire dynamics in interconnected vehicles? Influence of train configuration, interaction of ventilation conditions with fire development,
Advanced Methods of Fire Estimation Objective: obtain better understanding of influence of key factors on fire development Limitations Uncertainty in model input parameters, sub-models Impact of simplifying assumptions (ie: prescribed burning rates) Further work would be beneficial in evaluating/validating prediction methodology flame spread at assembly and full scale for modern firehardened materials
Reference: Milford A, Senez P, Calder K, Coles A (2014) Computational Analysis of Ignition Source Characteristics on Fire Development in Rapid Transit Vehicles, 3 rd International Conference on Fire in Vehicles (FIVE), 131-142 Advanced Methods Example 1 Prescribed burning rate methodology with interconnected trains FDS 5.5.3, material burning properties from cone calorimeter testing
Reference: Milford A, Senez P, Calder K, Coles A (2014) Computational Analysis of Ignition Source Characteristics on Fire Development in Rapid Transit Vehicles, 3 rd International Conference on Fire in Vehicles (FIVE), 131-142 Advanced Methods Example 1 Objective: estimation of fire development trends relative to: No fire development One portion of incident car Forced ventilation (open doors) Ignition source strength and location Ignition location: floor beneath seats
Advanced Methods Example 2 Assembly scale testing of rapid transit vehicle materials with large initiating source (500 kw) Pyrolysis modelling and comparison: FDS 5 Reference: Coles A, Wolski A, Lautenberger C (2009) Predicting Design Fires in Rail Vehicles, 13 th International Symposium on Aerodynamics and Ventilation of Vehicle Tunnels, 819-833
Advanced Methods Example 2 Comparison of model with experiment (500 KW burner) Evaluation of other ignition source: 300 kw (peak) trash bag Reference: Coles A, Wolski A, Lautenberger C (2009) Predicting Design Fires in Rail Vehicles, 13 th International Symposium on Aerodynamics and Ventilation of Vehicle Tunnels, 819-833
Advanced Methods: Example Findings Small localized ignition sources unlikely to lead to fire development beyond the immediate area under natural ventilation Most common nuisance ignition sources (trash, minor introduced combustibles): minimal risk Extreme ignition scenarios (ie: flammable liquids) have potential for fire spread beyond initiating area Remote event, disproportionate to materials typically present, security and risk implications
Risk Considerations Risk philosophy: What is acceptable and what constitutes acceptance? Owners/operators, authorities/regulators, public Likelihood of occurrence for the key factors vs potential severity
Event Tree Analysis Type of Incident Type of Fire Spread Detection Extinguished Probability P(ext)=0.10 0.1 1.608E-05 P(spread)=0.05 0.05 0.99 P(det)=0.99 P(ext')=0.90 0.9 1.447E-04 Full Vehicle Involvement P(det')=0.01 P(ext')=1.0 0.01 1 1.624E-06 P(fire)=0.0058 P(arson)=0.56 P(spread')=0.95 P(det)=0.99 P(ext)=0.93 0.93 2.841E-03 0.95 P(ext')=0.07 2.138E-04 Localized Damage Incident P(det')=0.01 P(ext')=1.0 0.01 1 3.086E-05 P(mech/elec)=0.44 0.44 2.552E-03 P(other)=0.9942 0.9942 1.000000
Evaluation of Risk Context Probabilistic assessment What is credible? Statistical data Uncertainty? Evaluation Risk scoring Cost-benefit analysis
Thank you! Questions?