Fire and Gas Mapping - Generic Methodology

1. INTRODUCTION
ERM F&GPro is one of the leading 3D aided software tools to perform Fire & Gas Mapping with
significant accuracy, which considers all elements (equipment, piping and structures, etc.) of the facility 3D
models and is featured as WYSIWYG (What You See Is What You Get) in mapping calculations. Fire
characteristics of Radiant Heat Output (RHO) and physical fire size (fire area in m2) are taken into account
to produce flame mapping results closer to the scenarios found in a fire detection event. It aims at cost-
effective solutions to provide adequate F&G detection coverage with optimized F&G detector layouts.
ERM is fully experienced in conducting fire and gas mapping studies via approaches such as industry
accepted BP GP 30-85, Shell DEP 32.30.20.11-Gen, PTS 32.30.20.11, Woodside Energy W1000SF008, NORSOK
Standard S-001, ISA-TR84.00.07-2010, or tailor-made approaches.
FIRE AND GAS MAPPING SOFTWARE:ERM F&GPRO
ERM F&GPro is compatible with the leading CAD format, i.e. Microstation (.dgn format) and STL
(STereoLithography) and it enables ERM to deliver 3D F&G mapping with significant accuracy to meet the
client’s requirement.
 All elements (including equipment, piping,
structure, etc) of the facility 3D models are taken
into account in mapping calculations by ERM
F&GPro.
 If 3D CAD models are unavailable
(which may occur for existing legacy
facilities and at the FEED stage for new
facilities), ERM F&GPro is also capable of
importing 2D facility layouts and
creating skeleton geometry models
which represents obstruction from major
equipment.
ERM - Fire & Gas Mapping Methodology

2.  Popular F&G mapping tools consider the fire as a
point source thus detection is dependent only on
clear line-of-sight from the detector to the fire
location. ERM F&GPro is able to consider the fire as
an area source, i.e. it takes into account factors of
heat radiation (RHO in kW) as well as physical fire
size (in m2) in mapping calculation. Therefore,
even if a fire at a specific location is partially
blocked, a flame detector can still be triggered
by the visible portion if the fire is close enough to the flame detector. This feature produces flame
mapping results that are closer to the scenarios found in a fire detection event.
STUDY METHODOLOGY OVERVIEW

3. FLAME MAPPING METHODOLOGY
 Performance grading will be conducted to determine the level of detection coverage
required for an area or equipment based on the nature and level of risk expected. Target fire
size and coverage performance target will be determined accordingly.
 Facility 3D CAD models will be imported to ERM F&GPro.
 Detection coverage will be conducted
based on line-of-sight from the
detectors, considering the blockage
from equipment, piping and structures
etc.
 The calculation first determines the coverage from each detector and then areas of
overlapping coverage if voting logic is to be applied by overlaying the coverage area from
each detector in turn. Areas which lie in sight of two or more detectors, areas in sight of one
detector and areas with no coverage can then be determined.
 If the performance target is not met,
the preliminary flame detector layout will
then be improved by relocating flame
detectors and / or adding flame detectors
if required.
 The calculation can also be made to
determine the impact of detector in fault
(Fail Danger) (maximum up to 3 detectors)
and its associated reduction in overall
detection coverage of the zone which
enables the safety versus economic value
of each detector to be judged, as well as assists the
operator to make decision in case one detector is in
fault but spare detector is not available in stock due
to reasons such as logistics.
 Results will be presented in terms of coverage maps,
overlaid on plot layouts, as well as flame detector
locations.
GAS MAPPING METHODOLOGY
 Performance grading will be conducted to determine the level of detection coverage
required for an area or equipment based on the nature of the area and its congestion level.
Target cloud size and coverage performance target will be determined accordingly. Typical
target gas cloud sizes lie in the range of 4m to 10m diameter for enclosed areas to relatively
open areas.

4.  Instead of conservative typical target gas cloud sizes, site specific target gas cloud sizes can
be determined from CFD explosion analysis based on facility 3D models of each unit area.
Combinations of conditions (cloud size, cloud position and ignition location) produce a
large number of simulations in FLACS. The
smallest cloud that can generate damaging
overpressure (150 mbar) will be determined and
adopted in the gas mapping study. For an open
area with lower congestion levels, the site-specific
target cloud size could vary from 10 m to 26 m
based on ERM’s past project experiences. Such
realistic target cloud sizes minimize the potential
excessive gas detectors required from gas
mapping calculation using the typical
conservative target cloud size of 10 m sphere.
 For the target cloud size, dispersion modelling will be conducted using PHAST, for a range
of release cases and weather conditions applicable to the facilities in the study, to determine
the gas plume size at Low/ High alarm set points.
 Facility 3D CAD models will be imported to ERM F&GPro.
 Similar to flame mapping, areas which lie in detection of two or more detectors, areas in
detection of one detector and areas with
no coverage can be determined.
 If the performance target is not met, the
preliminary gas detector layout will
then be improved by relocating gas
detectors and / or adding gas detectors
if required.
 Similar to flame mapping, the
calculation can also be made to
determine the impact of detector in fault
(Fail Danger) (maximum up to 3
detectors) and its associated reduction
in overall detection coverage of the zone.
 Results will be presented in terms of coverage maps, overlaid on plot layouts, as well as gas
detector locations.
For more information on ERM’s process safety, risk, and reliability services and how our team can help
your business, please contact:
North Asia
Mr. Herve Bonnel
Tel: + 852 2271 3205
Email:
Herve.Bonnel@erm.com
South Asia / Australia
Dr. Christina Phang
Tel: + 60 3 2733 9830
Email:
Christina.Phang@erm.com
Europe and Middle East
Mr. Kevin Kinsella / Mr. Gareth
Roberts
Tel: +44 161 958 8800 / +971 2 443
1989
Email: Kevin.Kinsella@erm.com /
Gareth.Roberts@erm.com
United States
Mr. Stephen Shaw
Tel: +1 832 786 5920
Email:
Stephen.Shaw@erm.com
Fire & Gas Mapping Technical Inquiry
Dr. Sunny Cao
CEng MIChemE MIET CFSP
Tel: + 852 2271 3227
Email: Sunny.Cao@erm.com
LinkedIn: https://www.linkedin.com/in/sunny-shengli-cao-90025428/