SFS 25 YEAR ANNIVERSARY

SEMINARSprinkler System Design Performance Solutions –

NIST FDS

Andre Mierzwa FIE

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?

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

WHAT DOES IT TAKE TO

REALLY MODEL FIRE AND

SPRINKLER PERFORMANCE?

Firstly - Model the fire for the actual commodity and

configuration

WHAT DOES IT TAKE TO

REALLY MODEL FIRE

SPRINKLER PERFORMANCE?

Secondly – Model fire suppression

FIREFOAM DEVELOPMENT

FM Research

Many PHD Scientists working over the last 12

years to develop our current models – working

on a lot more

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

FIREFOAM DEVELOPMENT

FM Research

Many PHD Scientists working over the last 12

years to develop our current models – working

on a lot more

WHAT DO WE USE THE MODELLING

FOR?

Help solve fire protection problems – develop sprinkler

system design

RECENT SUCCESSES

Virtual floor concept – in rack sprinkler layout for cost effective

unlimited height warehouses – standard racking structure (in AS

2118.1:2017)

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)

RECENT SUCCESSES

Roll paper storage (FM

Global Data Sheet)

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.

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

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

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?

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

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

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

THANK YOU