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Application of Consequence Analysis
and Risk Assessment in ERDMP
Dr. Asit K Patra
Disaster Management Institute
Bhopal
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What we do in Consequence Analysis
Consequence Analysis --- an analytical approach used
to determ ine the poss ible phys ical effects resulting fromthe release of a hazardous substance.
Source term modelling -- Estimation of the source term --
how much mater ial in what form(gas/liquid/two-phase)is being released
Hazard modelling -- Estimation of the hazard level as a
function of time and at selected receptor locations.
Vulnerability modelling --- Estimation of damage level on
the selected receptor, based on the hazard level at the
receptor location.
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1. Discharge Models: Loss of containment/Release
scenarios.
2. Dispersion Models: Transport and dispersion of
released flammable/Explosive/toxic chemicals.
3. Consequence/Effect models: Effect on people,
property and environment.
What we do in Consequence Analysis*****Contd.
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(A) Liquid Discharges
* Hole in atmospheric storage tank or other atmospheric
storage vessel or pipe under liquid head.
* Hole in vessel or pipe containing pressurized liquid
below its normal boiling point.
(B) Gas Discharges
* Hole in equipment (pipe, vessel) containing gas under
pressure
* Relief valve discharge (of vapour only)
Contd..
Typical Release Scenarios
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*Evaporation from liquid pool (e.g., naptha, heavy cut
etc.)
*Relief valve discharge from top of pressurized storagetank
* Generation of toxic combustion products as a result of
fire
(C) Two-Phase Discharges
*Hole inpressurized storage tank or pipe containing a
liquid above its normal boiling point.
* Relief valve discharge (e.g., due to a runaway reaction or
foaming liquid)
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.... .. .
++++++++++++++++
+++++++++++++++++++++++
++++++++++++++++
Leak
Aerosol
TBOILING POINT< T AMBIENT
Pool Spread
BoilingPool
Flash
Example: Super-heated release (Release of Liquid Chlorine)
Tank with
liquid
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EXAMPLERELEASE OF PRESSURISED
GAS
Release
Jet fire
No ignitionSafe dispersion
Ignition
Delayed
ignition
Immediate
ignition
Open
atmosphere
Congested atmosphere Vapour cloudexplosion
Flash fire
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EXAMPLERELEASE OF A REFRIGERATED
LIQUEFIED GAS
Release
Pool fire
No ignitionSafe dispersion
Ignition
Delayed
ignition
Immediate
ignition
Open
atmosphere
Congested atmosphere Vapour cloudexplosion
Flash fire
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EXAMPLEEVENT TREE FOR RELEASING OF
LIQUEFIED GAS UNDER PRESSURE
Release
No ignitionSafe dispersion
Ignition
Delayed
ignition
Openatmosphere
Congested atmosphereVCE
Flash fire
Immediate
ignition
No cooling
CoolingJet fire
BLEVE
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Atmospheric Dispersion
The process of dilution of a hazardous substance by the
surrounding fluid.Initial Acceleration
& Dilution Internal Negative
Buoyancy
Ambient
Turbulence
Source Emission Transition to Ambient Turbulence
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Wind speed & direction:Dilutes the released chemical and then it
spreads along the wind direction.
Thermal stability: Stable (E - F), Neutral(D) and Unstable (A-C)
Temperature Inversion: Suppress the movement of toxic cloud.
Factors Affecting Transport and Dispersal of toxic chemicals
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Procedures : CA
Two types of analysisthat make up an
Consequence Analysis (CA):
(i) Worst Case Release Scenario Analysis
(WCRSA): how far away -------
the worst possibleaccident release
scenario .
(ii) Alternative Case Release Scenario
Analysis (ACRSA): circumstances that
are more likely to occur accidentally.
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Scenario:Jet Fire Scenario of Natural Gas while being
transported through underground pipeline
Pipe Diameter: 20 inches Pipe Length: 10 Km
Pipe Press: 500 psia Pipe Temperature: 35 C
Wind: 5 meters/second Ground Roughness: Industrial
Air Temperature: 35 C Stability Class: DRelative Humidity: 70%
*******************************************************
THREAT ZONE:
Threat Modeled: Thermal radiation from jet fire
4.5 Kw/m2 (Blue Zone) 168
12.5 Kw/m2 (Orange Zone) 99
37.5 Kw/m2 (Red Zone) 45 meters
Consequence Analysis
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Scenario:Catastrophic rupture of a Naptha storage tank: Pool Fire
Chemical details:* Capacity of tank = 950 m3. * Density at 20OC = 0.93 g/ml.
* Dyke Dimension: 40.5 m x 36.25 m
* Storage Conditions: Atmospheric.
* LFL/LEL = 1% by volume of air.
Table 1: Maximum affected distances (in meter) for Pool fire
scenarios under D class with wind speed of 5.0 m/s
Thermal radiation Affected Distance in Metre from Poollevels for Fire
4.5 Kw/m2 (Blue Zone) 69
12.5 Kw/m2 (Orange Zone) 24
37.5 Kw/m2 (Red Zone) Not Reached
Consequence Analysis using SAFETI Micro
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Case Study: Consequence and Risk Analysis of
Natural Gas Release scenarios (TransportationMode: Underground Pipeline)
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Analysis identifies release of NG due to two events(i) Rupture of pipeline.
(ii) Hole in the pipeline.
Consequences
1. Jet FireMost Credible release Scenario
2. Vapour cloud ExplosionCredible Scenarios
3. Flash fire - Credible Scenarios
4. FireballNot possible
5. Pool FireNot possible
Identification of Hazards
FMEA M d C d C
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FMEA: Mode, Causes and Consequences.
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** Normally Fire ball scenario is not expected. Its
frequency of occurrence is low.
** Jet fireand flash fireare the credible scenarios with
sufficient frequencies of occurrences.
** VCE chances are considered as only 10% and
remaining 90% cases results in flash fire incidents.
Failure Frequency Assessment: Pipeline and Scenarios
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Probability of Ignition
Leak Size Ignition Probability
10 mm20 mm (Small Leak) -------- 0.01 0.03
~ 50 mm (Medium Leak) --------------- 0.07
Full Bore Rupture ------------------------ 0.3
E t t f h d i id t t f NG i li
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Event tree for hazardous incident outcomes of NG pipeline
SELECTION OF MAXIMUM CREDIBLE LOSS
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SELECTION OF MAXIMUM CREDIBLE LOSS
SCENARIOS
Maximum pipeline length in between twosectionalizing valves = 32 km with 20 inches diameter.
Worst-case Scenario: Full bore rupture
Alternative-case Scenario: Release through Leak sizes
of 20 mm (small hole) and 40 mm (medium hole).
Operating Pressure = 37 kgf/cm2
Volume pack in the line= 232736 m3= 180131 kg.
SELECTION OF MAXIMUM CREDIBLE LOSS
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SELECTION OF MAXIMUM CREDIBLE LOSS
SCENARIOS
Other Input Parameters
Average temperature = 30OC
Average relative humidity = 70%
Wind speeds = 1.5 m/s to 5 m/s
Atmospheric Stability = B, D and F
Angles of release for jet fire scenario: 45Oand 90Oto
the pipeline.
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CONSEQUENCE ANALYSIS RESULTS:FIRE
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Radiation radii of jet fire for rupture of pipeline when
the angle of release is 90 degree with the pipeline.
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Overpressure radii of vapour cloud explosion of NG for
rupture of pipeline when the angle of release is 90 degree
with the pipeline.
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Pipeline Risk = Linear Risk
Risk contours for a pipeline = Risk transects = Risk at
given transverse distances from the pipeline.
Pipeline Risk
POPULATION DENSITY USED IN RISK
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POPULATION DENSITY USED IN RISK
CALCULATION
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FATALITY RISK TRANSECT OF PIPELINE
Outcome of Consequence &
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Outcome of Consequence &
Risk Analysis
(a) Maximum loss scenarios
(b) Consequences in terms of Heat radiation, Over
pressure and intoxication.
Identification of vulnerable zones and
classification of unitswhich have the potential forcreating an off-site emergency.
(d)Identification of important facilities which are
coming into the vulnerable zones.
DMI
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Concern for man himself and his
safetymust always form the chief
interest of all technical endeavours.
Never forget this in the midst of your
diagrams and equations.
------ Einstein.
DMI
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For Further Information, Please contact:
asitkpatro@gmail.com
Thanks
DMIInfrastructures required
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. Complete Inventoryof hazardous processes, chemicals,
details of storage (T, P, type of vessel etc.) etc.
. Expert professionalshaving thorough understanding of
the process thermodynamics and atmospheric dispersion.
. Meteorological data and knowledge of stability classes.
. Relevant Softwareto predict vulnerable zones
DMIInfrastructures requiredfor Consequence/Risk
Analysis
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Part I: Baseline Information
Consequence Analysis --- an analytical approach used todetermine the possible physical effects resulting from the
release of a hazardous substance.
The credibility of any given modelling result depends upon the
credibility of the release scenario (hazardous event) chosen,
the supporting assumptions made in the analysis and the
technical merits of the model itself.
A good understanding of the underlying physics of the
scenario is essential to the success of model selection.
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MAJOR INDUSTRIAL ESTATES IN MADHYA
PRADESH
Hazard modelling ---Estimation of the hazard level as a function of
time and at selected receptor locations.
Estimation of:
Thermal radiation flux for fires (for a jet fire, pool fire, or fireball)
Overpressure for explosions (for a confined explosion, boiling
liquid expanding vapour explosion [BLEVE], or vapour cloud
explosion (VCE)
* Ambient concentrations for a toxic or flammable gas release (for
modelling the effects of a toxic cloud or flash fire),
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MAJOR INDUSTRIAL ESTATES IN MADHYA
PRADESH
Vulnerability modelling --- Estimation of damage
level on the selected receptor, based on the hazard
level at the receptor location.
L i Di f C /Ri k A l i
DMI
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Logic Diagram for Consequence /Risk Analysis
Release of Hazardous Substance
Discharge & Dispersion Models
Explosion & Fire Models
Consequence Models
Risk Calculation
Flammable Release
Toxic Release
Mitigation
Factors
B i f D i ti f ABCD i li
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Brief Description of ABCD pipeline
MODE:ABCD receives natural gas from Oil India Ltd.
through a 200 km underground pipelinestarting from A to D.
The pipelines are of level PSL 2 as per API 5L.
OPERATING CONDITIONS: The maximum operating
pressure and temperature at the pipeline is 45 kgf/cm2and
60OC respectively with the design pressure of 92 kgf/cm2.
PIPELINE ROUTE DESCRIPTION WITH FACILITIES:
(i) ABCD starts at the A dispatch station located near Oil India
Ltd. well No. 50 .
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Brief Description of ABCD
(ii) From dispatch section, the ABCD goes to 22 km with 20
pipeline. One sectionalizing valve station (SV1) is installed inthis section. The river R1 with a width of 517 m is situated at a
distance of 9.0 km from dispatch section.
(iii) From SV1, ABCD goes on to a distance of 31 km with 20pipeline. One sectionalizing valve station (SV2)is installed.
(iv) From SV2, the pipeline system goes on to a distance of 23
km with 20pipeline. One sectionalizing valve station (SV3) isinstalled.There are two rivers river R2 with width of 90 m
and R3 with width of 120 m - located at the distances of 6 km
and 12 km respectively from SV2.
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Brief Description of ABCD
(v) From SV3, ABCD goes on to a distance of 25 km with 20
pipeline. One intermediate pigging station (IP1) is installed.
The river R4 with width of 65 m is situated at a distance of 12.5
km in this section from SV3.
(vi) From IP1, the pipeline system, goes on to a distance of 24
km with 20pipeline. One sectionalizing valve station (SV4) is
installed.
(vii) From SV4, ABCD goes on to a distance of 23 km with 20
pipeline. One sectionalizing valve station (SV5) is installed. The
river R5 with width of 60 m is situated at a distance of 2.5 km
in this section from SV5.
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Brief Description of ABCD
(viii) From SV5, ABCD goes on to a distance of 32 km with 20
pipeline. One intermediate pigging station (IP2) is installed.
This is the longest stretch in between two sectionalizing valves.
(ix) From IP2, the pipeline system, goes on to a distance of 14
km with 16pipeline. The receiving station at D is installed in
this section.The river R6 with width of 160 m is situated at a
distance of 10 km in this section.
(x) The receiving station of D refinery is the end point of
ABCD.
Identification of Hazards
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Identification of Hazards
(i) Manufacture, Storage and Import of Hazardous
Chemicals (MS& IHC) Rules of 1989 as amended in2000 of Environment (Protection) Act of 1986, Govt.
of India.
(ii) Failure Mode and Effect Analysis (FMEA)
Id tifi ti f H d MS&IHC R l
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Identification of Hazards as per MS&IHC Rules
Hazards of NG: The natural gas to be transported by the pipelines
predominantly contains methane (around 92%). Other components
of the gas include ethane, propane and butane. As per the MS&IHC
Rules 1989 as amended in 2000, methane comes under Flammable
gascategory. Its Lower Flammability/Explosivity Level (LFL/LEL)is 5% and upper level range (UFL/UEL) is 15% by volume of air. Its
flash point is -188OC.
The minimum ignition energy for pure Methane at atmospherepressure is 0.29 mJ, which is very low when compared to static
discharge of 22 mJ (on walking) or ordinary spark plug discharge of
25 mJ. Hence ignition can occur at any time during the gas release.
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References
1. Loss Prevention in Chemical Process Industries. Volume
1, 2 & 3. by F. P. Lees, 1996. Butterworth Publications.
2. Guidelines for Chemical Process Quantitative Risk
Analysis. 2ndEdition, CCPS, AIChE, 2000.
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CONSEQUENCE ANALYSIS RESULTS:VCE
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CONSEQUENCE ANALYSIS RESULTS:VCE
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Pipeline Risk = Linear Risk
Risk follows the entire pipeline length, in contrast to a fixedhazardous facility, where the risk extends only to a
limited distance from the facility.
Risk contours for a pipeline are represented as running parallel
to the pipeline. Risk levels for linear risks are often presented
in the form of risk transects, showing the risk at given
transverse distances from the pipeline
Pipeline Risk