Download Fire Development

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]
Lighter or match
Polyethylene wastebasket (0.6 kg) filled
with shredded paper (0.2 kg)
<1
15
Approximate Peak Burning
Duration [s]
100 - 200
Pillow with 0.65kg of polyurethane foam
40
100
Luggage filled with clothes
120 (hard suitcase)
300
Two men’s jackets
Trash bags filled with paper (1.17kg total)
25 (soft suitcase)
75 - 85
140 (1 bag - 1.17 kg)
1000
10 - 20
100
280 (2 bags - 2.34 kg)
20
350 (3 bags - 3.51 kg)
30 – 260
100
10 - 400
Amtrak trash bags from overnight trains
(1.8 - 9.5 kg)
●
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
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, 3rd International Conference on Fire in
Vehicles (FIVE), 131-142
Advanced Methods – Example 1
No fire development
● Objective:
estimation of
fire development
trends relative
to:

Forced ventilation
(open doors)

Ignition source
strength and
location
One portion of incident car
Ignition location: floor beneath
seats
Reference: Milford A, Senez P, Calder K, Coles A (2014) Computational Analysis of Ignition Source
Characteristics on Fire Development in Rapid Transit Vehicles, 3rd International Conference on Fire in
Vehicles (FIVE), 131-142
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, 13th
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, 13th
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
0.99
P(det)=0.99
P(ext')=0.90
0.9
1.447E-04
P(ext')=1.0
1
1.624E-06
P(ext)=0.93
0.93
2.841E-03
P(ext')=0.07
0.07
2.138E-04
P(ext')=1.0
1
3.086E-05
P(spread)=0.05
0.05
P(det')=0.01
0.01
Full Vehicle
Involvement
0.56
P(arson)=0.56
P(fire)=0.0058
0.0058
0.99
P(det)=0.99
P(spread')=0.95
0.95
P(det')=0.01
0.01
Incident
P(mech/elec)=0.44
0.44
P(other)=0.9942
0.9942
2.552E-03
0.9942
1.000000
Localized
Damage
Evaluation of Risk Context
● Probabilistic assessment
 What is credible?
 Statistical data
 Uncertainty?
● Evaluation
 Risk scoring
 Cost-benefit analysis
Thank you!
Questions?