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SFS 25 YEAR ANNIVERSARY
SEMINARSprinkler System Design Performance Solutions –
NIST FDS
Andre Mierzwa FIE
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QUESTION
Can we model a growing fire through to sprinkler activation and then the operation of the sprinkler system impacting on the fire to the point where either fire suppression, fire control or an uncontrolled fire is reliably determined?
Occasionally we see Fire Safety Engineers attempt to do this. Just because a fire model provides some functionality – is this OK? Is it a friend or foe?
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WHAT TOOLS ARE OUT THERE?
Available to Fire Safety Engineers
NIST Fire Dynamics Simulator
Pyrosim – graphical user interface
Available to FM Research, Academia and Industry
OpenFOAM and FireFOAM
Open source CFD toolboxes written in C++
FireFOAM has 5 specific sub-models
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WHAT DOES IT TAKE TO
REALLY MODEL FIRE AND
SPRINKLER PERFORMANCE?
Firstly - Model the fire for the actual commodity and
configuration
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WHAT DOES IT TAKE TO
REALLY MODEL FIRE
SPRINKLER PERFORMANCE?
Secondly – Model fire suppression
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FIREFOAM DEVELOPMENT
FM Research
Many PHD Scientists working over the last 12
years to develop our current models – working
on a lot more
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FIREFOAM DEVELOPMENT
FM Research
Many PHD Scientists working over the last 12
years to develop our current models – working
on a lot more
▪ Spray/Plume
Interaction
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FIREFOAM DEVELOPMENT
FM Research
Many PHD Scientists working over the last 12
years to develop our current models – working
on a lot more
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WHAT DO WE USE THE MODELLING
FOR?
Help solve fire protection problems – develop sprinkler
system design
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RECENT SUCCESSES
Virtual floor concept – in rack sprinkler layout for cost effective
unlimited height warehouses – standard racking structure (in AS
2118.1:2017)
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RECENT SUCCESSES
Automatic Stacking and Retrieval in-rack sprinkler layout and
design criteria (utilising the virtual floor concept) for mini load
(plastic bins) racking (in Amendment 2 AS 2118.1:2017)
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RECENT SUCCESSES
Roll paper storage (FM
Global Data Sheet)
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LIMITATIONS
Limitations
Only 3 sprinklers modelled – water mist under way
Commodities –Class 2, Class 3, Unexpanded Plastics in
cartons, Roll Paper and Unexpanded Plastic – Cartoned
and Uncartoned Expanded Plastic is under way.
Ignitable Liquids future work.
Need a Supercomputer – FM research Norwood,
collaboration with National Supercomputer Centre Oak
Ridge.
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WHAT ARE WE SEEING FIRE SAFETY
ENGINEERS ATTEMPTING TO DO?Request to fire engineer out a problem (sound familiar)
Existing Warehouse with ESFR System, Building 11.3 m high, compliant for cartoned unexpanded plastic.
Change in commodity – Sprinkler standard limits storage height to 1.5m for 12.2m ceiling or 4.5m with maximum 9m ceiling height (there is a good reason for this if one understands sprinkler design requirements)
Required outcome – Performance Solution to store new commodity to 4.5m with the ceiling only ESFR sprinklers in the 11.3 m high warehouse
Assessment Method A0.5(b)(ii)&(d)
Such other Verification Methods as the appropriate authority accepts for determining compliance with Performance Requirements
Comparison with the Deemed-to-Satisfy Provisions
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FIRE MODELLING – “ABSOLUTE” VERIFICATION
Model used – NIST FDS and Pyrosim
Fire source – Generic best guess
Fire Slabs
Ultra fast t2
Peak Heat Release Rate – HRRpk – 500 kW/m2
Peak Fire Size – 15 MW
Radiation Fraction – 0.35
Reaction – Polyurethane
Soot Yield 0.1
Duration – 5 min
“Absolute” Verification based on
Sprinkler Activation Time
Temperature at target on sprinkler activation
Heat Flux at target at time of sprinkler activation
*Water spray from sprinklers – turned off
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NIST FDS COMPARED WITH FIREFOAM
NIST FDS
Fire Source – generic
best guess – not related
to the actual commodity
Time to sprinkler activation
Sprinkler Spray turned off
Suppression deemed to
occur at time of sprinkler
activation, temperature and radiant
heat flux on target (across aisle)
at that time
Where exceeded –
“the high flow and pressure of the
ESFR sprinkler spray should easily
and quickly control a fire that has only
just begun to spread across the aisle”
Is this an acceptable “Absolute” validation
of the performance solution?
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PERFORMANCE SOLUTIONS USING
NIST FDS
Although some functionality is provided to build and model rack storage
fires, determine sprinkler activation time for single and multiple sprinklers
and the inclusion of spray simulation – can we rely on the model output as
verification of a performance solution?.
The answer is NO
The NIST FDS only plays around the edges of real fire and sprinkler
performance modelling.
The only acceptable validation of a performance solution involving
sprinkler system design is full scale fire testing
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CONCLUSION
Yes – we can model real fire growth, sprinkler activation, water interaction
with the fire plume and burning commodity to determine fire suppression,
control or uncontrolled fire.
Limited to less than a handful of sprinklers and a few generic commodities.
Only FM Research has all the models and data to do that.
FM Research uses this capability to identify potential protection design
criteria for specific protection problems
FM Research ALWAYS verifies and validates the results through full scale fire
testing.
Results are published as prescriptive design requirements in FM Data Sheets
and Australian Standards
Warning - DO NOT ATTEMPT TO DO THIS AT HOME
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THE ONLY PERFORMANCE SOLUTION
FOR SPRINKLER SYSTEM DESIGN
Is DtS – AS 2118.1 – 2017 and where
appropriate FM Data Sheets
Apply the standard as it is – do not
attempt to modify it
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THANK YOU