2013 cfaa presentation - andrew coles - fire and... · 2013 cfaa british columbia technical seminar...

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Vancouver Toronto Calgary Singapore Global Leaders in Fire Engineering

Application of Fire and Smoke

Modelling to Automatic Fire

Detection

2013 CFAA British Columbia Technical

Seminar

Andrew Coles

Presented to:

Presented by:

Global Leaders in Fire Engineering Vancouver Toronto Calgary Singapore

› Introduction – Sereca Fire Consulting

› Fire alarm system requirements and design standards

› Location and spacing requirements for heat and smoke

detectors: ‘ordinary’ spaces

› Limitations of prescriptive requirements for non-’ordinary’

spaces

– High atriums, interconnected floor spaces, high bay industrial facilities

› Application of fire modelling

– Understanding smoke and heat detection in non-ordinary spaces

Presentation Overview

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› Provide you information about tools and methods available

in the industry

› What Fire Engineering can do to provide cost effective,

functional designs

Objective


Our Company

› Established in Vancouver in 2003 as a Forensic Investigation

Firm

› Offices in Singapore (2008), Calgary (2009), Toronto (2011)

› Building & Fire Code Analysis

› Fire Protection Engineering Design

› Fire Modeling & Visualization

› Evacuation Modeling

› Product Testing & Development

› Fire Investigation

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› Fire alarm systems may be required by:

– Building Code

– Insurer

– Owner’s risk management

› Building Codes specify design standards:

– Canada: CAN/ULC-S524 Installation of Fire Alarm

Systems

– US: NFPA 72 National Fire Alarm and Signaling Code

Fire Alarm System Requirements


› In normal buildings and indoor spaces, design standards

recognize spot-type heat and smoke detectors where

automatic fire (heat or smoke) detection is required

› Design standards provide prescriptive rules for location and

spacing, rules of standards apply within limits:

› Essentially equivalent if a 3600 mm (11.8 ft) ceiling is

considered the limit of “ordinary”

Heat and Smoke Detectors

S524 NFPA 72

Heat Detectors Ceilings up to 9000 mm (29.5 ft) high Ceilings up to 30 ft high

Smoke Detectors Ceilings up to 3600 mm (11.8 ft) high "Ordinary indoor locations" (17.7.1.4)

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› Detectors are required to be tested and ‘listed’ by a

recognized laboratory (ie: ULC)

› Heat detectors: listed with a specified maximum rated

spacing (often 50 ft)

› Smoke detectors: listed, but do not have a rated

spacing

– Nominal spacing of 30 ft is assumed, adjusted in

accordance with conditions

Detector Listings


› Heat and smoke detectors are listed differently

because heat and smoke behave different

– Heat: easily generated and measured, permitting

repeatable tests

– Smoke: differs in particle size, chemical

composition, and colour depending on fuel,

temperatures, availability of oxygen, ambient

conditions

› Smoke travel paths within a space can be more

difficult to predict than heat transfer

Differences in Detector Listings

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› Prescriptive rules for smoke detection in S524 and NFPA

72 apply to ‘ordinary’ spaces

› Requirements start with listed/nominal spacing, and

then adjust for:

– Ceiling height

– Ceiling construction: smooth, joists, beams

– Ceiling slope

› Within their limits, prescriptive requirements have been

found to produce acceptable levels of protection

Prescriptive Requirements Revisited


› Many modern buildings contain spaces that are outside of

the ‘ordinary’ category (high atriums, interconnected floor

areas, high ceiling bays)

S524: 5.7.4.2.1 – Note: Data is not available for ceilings higher than

9000mm, therefore, in such installations, fire type, growth rate,

engineering judgment, and manufacturer’s recommendations should

be used. For additional information refer to NFPA 72 …

S524: 5.7.5.1.2 – On ceilings above 3600 mm in room height, spot-type

smoke detector spacing shall be based on fire type, growth rate,

engineering judgment, and manufacturer’s recommendations.

NFPA 72: Requires “performance-based” design for any condition not

included in the prescriptive rules.

Application in Modern Buildings

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Code or Standard

Objectives and Functional Statements

Prescriptive Performance-based

Prescriptive vs. Performance Based

• Objectives met by

following exactly what

Code/Standard tells

you to do

• Application may not

be directly or

sufficiently addressed

by the Code

• Prove that what is being

evaluated meets the

Objectives of the Code

• Alternative Solution


› ‘Engineering Judgment’ and ‘Performance-based’ design:

requires understanding of the movement of smoke and heat

› Some methods for evaluating smoke and heat movement

include:

– Hand calculations/correlations

– Zone models

– 3D Computational Fluid Dynamics (CFD)

› Methods that are applicable depend on the complexity,

desired resolution of data, engineer’s

knowledge/experience, …

Quantifying Fire Effects in Non-‘Ordinary’ Spaces

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› Hand Calculations (NFPA)

› Zone Fire Modelling: CFAST

› Contaminant Transport (multi-zone):

CONTAM

› Computational Fluid Dynamics: FDS,

OpenFOAM

Analysis Tools


› For design purposes, the time-dependent movement of

heat and smoke can be evaluated in greatest detail using

CFD

› CFD fire models were originally developed ~ 30 to 40 years

ago as a research tool, and have become mainstream with

increase in computing power

› Validation of CFD models: comparison with measurements

from real-world experiments

› Parametric analysis: evaluation of the effects of various

parameter, such as building ventilation, varying the

ambient conditions, baffles, smoke curtains, etc.

Engineering Analysis - Modelling

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What is CFD?

› Equations for mass, energy, and momentum are

solved using a numerical grid (mesh)

› Detailed predictions of 3D flow and fire

› Detailed outputs: temperature, smoke, other gases,

velocity


› Examples of ‘non-ordinary’ spaces relevant to

understanding applications of detection spacing and

location

› Atrium spill plume

– 1 MW desk fire

– 6 m (19.7 ft), 12 m (39.4 ft), 18 m (59 ft) height

› Industrial room with roof beams,

– 230 KW transformer oil fire

– 200 mm and 600 mm ceiling beam height

› High bay with sloped roof

– 1 MW wood fire

– Two ceiling beam orientations

Fire Modelling Examples

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› Examining temperature and smoke distribution from a

desk fire into an adjacent atrium space

› Atrium area: 9 m x 30 m

Atrium Examples

Fire Location

18 m height

12 m height6 m height


Atrium – 18 m height (20 x normal speed)

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› As height increases there is more smoke compared to heat

at the top of the atrium

– This is why sprinklers are ineffective in high ceiling

spaces

Atrium - Results


› Evaluating the movement of smoke and height at ceiling

level in the presence of large beams

› Room dimensions: 15 m x 30 m x 4.6 m

Beam Ceiling Examples

200 mm beam depth 600 mm beam depth

Fire Location

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200 mm Beam Depth (20 x normal speed)

Plan view


600 mm Beam Depth (20 x normal speed)

Plan view

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› Deep beams – dominant smoke and heat spread laterally

within beam pockets

› Temperature differences between adjacent beam pockets

can be significant

› Smoke dispersion is much less affected by beams

Beam Ceiling - Results


› Movement of smoke and heat along a sloped ceiling

with two orientations of roof beams

› Compartment dimensions: 16 m x 30 m x 12 m (peak)

High Bay with Sloped Roof

Parallel Beams Perpendicular Beams

Fire Location

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Sloped Roof – Parallel Beams (20 x normal speed)


Sloped Roof – Perpendicular Beams (20 x normal speed)

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› Initial smoke spread is greatly affected by beam

orientation

› Heat dispersion is less impacted relative to smoke

movement

Sloped Roof - Results


› Simple industrial building with equipment

– H2S leak: with and without exterior wind

– Natural gas leak: with and without building ventilation

Gas Detection

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H2S Leak – No wind (20x speed)


H2S Leak – Wind (20x speed)

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Natural Gas Leak – No ventilation (20x speed)


Natural Gas Leak – 2 fans on left wall (20x speed)

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› Standards (ULC and NFPA) provide acceptable life

safety requirements within the prescribed limits

› In reality, non-‘ordinary’ spaces require further

consideration

› Smoke and heat movement are not the same for a

specific space and require careful consideration when

designing appropriate detection systems

› Other alternative scientifically-based approaches exist

to design or evaluate detection systems

Conclusions


Thank you!

Questions?

2013 cfaa presentation - andrew coles - fire and... · 2013 cfaa british columbia technical seminar...

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