rra study of gtu project -...
TRANSCRIPT
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 2 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
PREFACE
Engineers India Limited (EIL), New Delhi, has been appointed as the Project Management
Consultant (PMC) by M/s Bharat Petroleum Corporation Limited (BPCL), Mumbai for its GTU
Project at Mahul, in the state of Maharashtra, India. As a part of the project Rapid Risk Analysis
study of the facilities under the GTU Project is being executed for the Environment Clearance of
the Project along with the EIA Study.
Rapid Risk Analysis study identifies the hazards associated with the facility, analyses the
consequences, estimates the risk posed by them, draws suitable conclusions and provides
necessary recommendations to mitigate the hazard/ risk.
This Rapid Risk Analysis study is based on the information made available at the time of this
study and EIL’s own data source for similar plants. EIL has exercised all reasonable skill, care
and diligence in carrying out the study. However, this report is not deemed to be any
undertaking, warrantee or certificate.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 3 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
TABLE OF CONTENTS
1. EXECUTIVE SUMMARY ......................................................................................................................5
1.1 PROJECT DESCRIPTION ............................................................................................................5
1.2 MAJOR FINDINGS AND RECOMMENDATIONS ........................................................................5
2. INTRODCUTION ...................................................................................................................................9
2.1 STUDY AIMS AND OBJECTIVE ...................................................................................................9
2.2 SCOPE OF WORK .......................................................................................................................9
3. SITE CONDITION .............................................................................................................................. 10
3.1 GENERAL .................................................................................................................................. 10
3.2 SITE, LOACTION AND VICINITY .............................................................................................. 10
3.3 METEOROLOGICAL CONDITIONS .......................................................................................... 10
4. HAZARDS ASSOCIATED WITH THE FACILITIES ........................................................................... 13
4.1 GENERAL .................................................................................................................................. 13
4.2 HAZARDS ASSOCIATED WITH FLAMMABLE MATERIALS ................................................... 13
4.2.1 HYDROGEN .................................................................................................................. 13
4.2.2 NAPHTHA AND OTHER HEAVIER HYDROCARBONS .............................................. 13
4.3 HAZARDS ASSOCIATED WITH TOXIC/CARCINOGENIC MATERIALS ................................. 14
4.3.1 HYDROGEN SULPHIDE .............................................................................................. 14
5. HAZARD IDENTIFICATION ............................................................................................................... 15
5.1 GENERAL .................................................................................................................................. 15
5.2 MODES OF FAILURE ................................................................................................................ 15
5.3 SELECTED FAILURE CASES ................................................................................................... 16
6. CONSEQUENCE ANALYSIS ............................................................................................................ 17
6.1 GENERAL .................................................................................................................................. 17
6.2 CONSEQUENCE ANALYSIS MODELLING .............................................................................. 17
6.2.1 DISCHARGE RATE ...................................................................................................... 17
6.2.2 DISPERSION ................................................................................................................ 17
6.2.3 FLASH FIRE .................................................................................................................. 17
6.2.4 JET FIRE ....................................................................................................................... 18
6.2.5 POOL FIRE ................................................................................................................... 18
6.2.6 VAPOR CLOUD EXPLOSION ...................................................................................... 18
6.2.7 TOXIC RELEASE .......................................................................................................... 18
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 4 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
6.3 SIZE AND DURATION OF RELEASE ....................................................................................... 18
6.4 DAMAGE CRITERIA .................................................................................................................. 19
6.4.1 LFL OR FLASH FIRE .................................................................................................... 19
6.4.2 THERMAL HAZARD DUE TO POOL FIRE & JET FIRE .............................................. 19
6.4.3 VAPOR CLOUD EXPLOSION ...................................................................................... 20
6.4.4 TOXIC HAZARD ............................................................................................................ 20
6.5 CONSEQUENCE ANALYSIS OF THE SELECTED FAILURE CASES .................................... 20
6.5.1 GTU ............................................................................................................................... 21
6.5.2 DHT ATU ....................................................................................................................... 23
7. MAJOR FINDINGS AND RECOMMENDATIONS ............................................................................. 24
8. GLOSSARY........................................................................................................................................ 28
9. REFERENCES ................................................................................................................................... 30
ANNEXURE-I: HAZARD DISTANCES
ANNEXURE-II: FIGURES FOR CONSEQUENCE ANALYSIS
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 5 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
1. EXECUTIVE SUMMARY
1.1 PROJECT DESCRIPTION
M/s Bharat Petroleum Corporation Limited (BPCL) has decided to set up a new facility and
revamp an existing unit under its GTU Project at Mahul, in the state of Maharashtra, India, for
meeting the Euro-VI emission norms.
In this connection, M/s Engineers India Limited (EIL) has been appointed as the Project
Management Consultant (PMC) by M/s BPCL for its GTU Project. As a part of the project Rapid
Risk Analysis is being carried out, which is required for Environmental Clearance of the project
and this report shall form an Annexure of EIA study report.
This report contains methodology, results, observations and recommendations of the Risk
analysis study for facilities under GTU Project of BPCL Mumbai Refinery.
Rapid Risk Analysis (RRA) involves carrying out consequence analysis which comprises of
identification of various potential hazards, identification of credible failure scenarios for various
units and other facilities including off-site storages, etc. based on their frequency of occurrence
& resulting consequence. Two types of scenarios are identified spanning across various
process facilities; Cases with high chance of occurrence but having low consequence, e.g.:
Instrument Tapping Failure and Cases with low chance of occurrence but having high
consequence, e.g. Large Hole of Pressure Vessels. Effect zones for various outcomes of
failures scenarios (Flash Fire, Jet Fire, Pool Fire, Blast overpressures, toxic releases etc.) are
studied and identified in terms of distances on plot plan. Based on affect zones, measures for
mitigation of the hazard/risk are suggested.
1.2 MAJOR FINDINGS AND RECOMMENDATIONS
The major findings and recommendations arising out of the Rapid Risk analysis study for GTU
Project of BPCL Mumbai Refinery are summarized below:
Consequence modelling for High frequency credible scenarios of Gasoline Treatment Unit
was carried out and it is observed that LFL & Blast overpressure effect zones in the event of
Instrument Tapping Failure at Feed Pump, H2 Make Up Gas Compressor, Ist Stage HDS
Feed Pump, H2S stripper Inlet Line, HCN Product Pump and Flange Leakage at Stabilizer
Reflux Pump, IInd Stage HDS Feed Pump, may extend beyond the battery limits of the unit
and damage the equipment’s in the nearby process units, depending upon the prevalent
wind conditions & ignition source encountered at the time of release. It may also effect the
nearby FCCU Control Room based on the location of the equipment’s in the unit (FCC
Control Room is being converted to Blast resistant construction separately by BPCL-MR).
The 37.5 & 12.5 kW/m2 radiation intensities of Jet & Pool fire may also produce damaging
effects within the unit and even beyond the unit.
In order to mitigate the hazardous effect zones of the above said scenarios, following is
recommended:
Install hydrocarbon detectors within the units at strategic locations.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 6 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Classify the Road No. 7, B-53 & 14 for emergency vehicles only and minimize vehicle
movement on the road no. 9, to prevent any chances of ignition.
No operator cabin to be located in the vicinity of unit.
Ensure suitable radiation protection for the ISBL pipe-rack & OSBL (Northern, Eastern,
& Western) Pipe-rack adjacent to the unit.
Low frequency & high consequence credible failure scenarios are also modelled in Gasoline
Treatment Unit for the equipment handling bulk inventories. From consequence modelling it
is observed that the flammable & explosion effect zones for Large Hole scenarios in Feed
Surge Drum, Splitter Reflux Drum, IInd Stage Cold Separator, Stabilizer Reflux Drum are
crossing the unit’s B/L’s and may cause damage.
Being low frequency scenario, outcomes of these scenarios to be utilized for preparation of
the Disaster Management Plan & Emergency Response Guidelines for the Refinery.
Requirement of remote operated isolation valves at the bottom of the bulk inventory vessels
may be reviewed during detailed engineering stage for the early inventory isolation, as the
unit is located in already congested area.
Toxic Scenarios are also modelled for the Gasoline Treatment Unit, it is observed that for
high frequency credible failure scenarios, H2S IDLH concentration may extend beyond the
B/L of the unit, depending upon the prevalent direction of the wind at the time of release.
However, it may not reach the grade level.
It is recommended to install H2S detectors with Hooter (Local Alarm) at the strategic
locations within the unit, near to the equipment’s handling toxic material. Individual’s to be
evacuated on priority from area around Gasoline Treatment Unit in event of any toxic
release from the unit. These scenarios to be also utilized for preparation of the Disaster
Management Plan & Emergency Response Guidelines for the Refinery. Wind socks to be
installed near the GTU.
Toxic Scenarios is modelled for the existing ATU in DHT Block, it is observed that H2S IDLH
hazard effect zone for credible failure scenario may not reach grade level but toxic cloud
may spread throughout the unit.
It is recommended to ensure H2S detectors with Hooter (Local Alarm) at the strategic
locations within the unit, near to the equipment’s handling toxic material.
Recommendations for Construction Safety during execution of the GTU Project
Adequate barricading of the new proposed / revamp unit to be done from existing running
process units during construction phase. Hydrocarbon / toxic detectors to be placed along
the barricading suitably to detect any hydrocarbon / toxic gas in vicinity of construction
area. Also, adequate fire-fighting & toxic gas handling arrangement are to be ensured in the
construction area. Ensure training of persons associated with construction activities for
response during fire & toxic gas release.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 7 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Proper material movement path within the Refinery shall be identified during the
construction phase of the project.
Detailed HSE Plan & HSE Philosophy to be developed by contractors during construction
phase of the project, in line with client’s safety requirements.
It is recommended to identify & analyze the possible hazards during construction phase
and prepare the action plan to prevent / mitigate the same, as the proposed unit is located
in the already congested area of the running process units.
GENERAL RECOMMENDATIONS
For positively pressurized building, both Hydrocarbon & Toxic detectors need to be placed
at suction duct of HVAC. HVAC to be tripped automatically in event of the detection of any
Hydrocarbon / toxic material by detector.
Mitigating measures
Mitigating measures are those measures in place to minimize the loss of containment event and
thereby hazard associated. These include:
Rapid detection of an uncommon event (HC leak, Toxic gas leak, Flame etc.) and alarm
arrangements and development of subsequent quick isolation mechanism for major
inventory.
Measures for controlling / minimization of Ignition sources inside the Refinery complex.
Active and passive fire protection for critical equipment’s and major structures.
Effective Emergency Response plans to be in place.
Detection and isolation
In order to ensure rapid detection of hazardous events the following is recommended:
Ensure installation of flammable / toxic gas detection and fire detectors at strategic locations
for early detection and prevention of an uncommon event emanating from the process
facilities. Once the flammable / toxic gas release has been detected, as the gas or
subsequent fire, toxic and escalation risk will be reduced by isolation of the major inventory
from the release location (prevention of loss of containment). Hence, manual / automated
mechanism is required to isolate the major inventory during any uncommon event.
It is recommended that the storage vessels (column bottom, reflux drum, feed surge drums,
storage tanks etc.) which are dealing with very large inventory should be considered to have
remote operated valves so that these valves can be closed from the safe location upon fire
or flammable gas detection.
Ignition control
Ignition control will reduce the likelihood of fire events. This is the key for reducing the risk
within facilities that process flammable materials. As part of mitigation measure it is strongly
recommended to consider minimize the traffic movement within the refinery complex.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 8 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Escape routes
Provide windsocks throughout the site to ensure visibility from all locations. This will enable
people to escape upwind or crosswind from flammable / toxic releases. Sufficient escape routes
from the site should be provided to allow redundancy in escape from all areas.
Preventive maintenance for critical equipment’s
In order to further reduce the probability of catastrophes efficient monitoring of vessel
internals during shut-down to be carried out for Surge Drums & Reflux drums and critical
vessels whose rupture would lead to massive consequences based upon the outcomes of
RRA study.
The vehicles entering the refinery should be ensured to be fitted with spark arrestors.
In order to prevent secondary incident arising from any failure scenario, it is recommended
that sprinklers and other protective devices provided on the tanks to be regularly checked to
ensure that they are functional.
Routine check to be ensured in the area to prevent presence of any potential ignition source
in the vicinity of the refinery.
Others
Removal of hammer blinds from the process facilities to be considered.
Closed sampling system to be considered for pressurized services like LPG, Propylene etc.
Whenever a person visits for sampling and maintenance etc. it is always recommended one
should carry portable H2S / Chlorine detectors.
Provide breathing apparatus at strategic locations inside Refinery.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 9 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
2. INTRODCUTION
2.1 STUDY AIMS AND OBJECTIVE
The objectives of the Rapid Risk Analysis study are to identify and quantify all potential failure
modes that may lead to hazardous consequences and extent. Typical hazardous consequences
include fire, explosion and toxic releases.
The Rapid Risk analysis will also identify potential hazardous consequences having impacts on
population and property in the vicinity of the facilities, and provides information necessary in
developing strategies to prevent accidents and formulate the Disaster Management Plan.
The Rapid Risk Analysis includes the following steps:
a) Identification of failure cases within the process and off-site facilities.
b) Evaluate process hazards emanating from the identified potential accident scenarios.
c) Analyze the damage effects to surroundings due to such incidents.
d) Suggest mitigating measures to reduce the hazard / risk.
The Rapid Risk analysis study has been carried out using the risk assessment software
program ‘PHAST & PHAST RISK’ ver. 6.7 developed by DNV Technica.
2.2 SCOPE OF WORK
The study addresses the hazards that can be realized due to operations associated with the
facilities under BPCL Mumbai Refinery. It covers the following facilities of BPCL Mumbai
Refinery:
Table 1: Process facilities under GTU Project
S. No DESCRIPTION REMARKS
1. New GTU
2. ATU (Revamp)
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 10 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
3. SITE CONDITION
3.1 GENERAL
This chapter depicts the location of BPCL Mumbai Refinery complex. It also indicates the
meteorological data, which will be used for the Risk Analysis study.
3.2 SITE, LOACTION AND VICINITY
M/s Bharat Petroleum Corporation Limited (BPCL) is located geographically at 180 54’ N
latitude and 720 49’ E longitude. Figure 1: BPCL MR Site
3.3 METEOROLOGICAL CONDITIONS1
The consequences of released toxic or flammable material are largely dependent on the
prevailing weather conditions. For the assessment of major scenarios involving release of toxic
or flammable materials, the most important meteorological parameters are those that affect the
atmospheric dispersion of the escaping material. The crucial variables are wind direction, wind
speed, atmospheric stability and temperature. Rainfall does not have any direct bearing on the
results of the risk analysis; however, it can have beneficial effects by absorption / washout of
1 Meteorological Conditions have been taken from QRA Study BPCL Mumbai Refinery Mumbai (Doc No:
A369-04-41-RA-001)
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 11 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
released materials. Actual behaviour of any release would largely depend on prevailing weather
condition at the time of release.
For the present Rapid Risk Analysis study, Meteorological data of Mumbai station (nearest
observatory) have been taken from Climatological tables of Observatories in India (1961–1990),
published by India Meteorological Department.
Atmospheric Parameters
The Climatological data which have been used for the Rapid Risk Analysis study is summarized
below: Table 2: Atmospheric Parameter
S. No. PARAMETER AVERAGE VALUE CONSIDERED FOR STUDY
1. Ambient Temperature (OC) 28
2. Atmospheric Pressure (mm Hg) 760
3. Relative Humidity (%) 70
4. Solar Radiation flux (kW/m2) 0.76
Wind Speed and Wind Direction
The average monthly wind speed varies between 1.8 to 4.5 m/s. For the purpose of present
study the selected representative wind speeds are 2 m/s, 3 m/s and 5 m/s. These wind speeds
have been selected to represent the entire range of wind speeds in the region. Table 3: Average Mean Wind Speed (m/s)
Jan Feb Mar April May June July Aug Sep Oct Nov Dec
1.89 2.19 2.36 2.64 3.08 3.88 4.47 4 2.44 1.72 1.72 1.75
Table 4: % Number of Days Wind From
N NE E SE S SW W NW Calm
D 9 1 0 0 1 10 30 48 1
N 4 10 14 4 4 8 13 5 38
Weather Category
One of the most important characteristics of atmosphere is its stability. Stability of atmosphere
is its tendency to resist vertical motion or to suppress existing turbulence. This tendency directly
influences the ability of atmosphere to disperse pollutants emitted into it from the facilities. In
most dispersion scenarios, the relevant atmospheric layer is that nearest to the ground, varying
in thickness from a few meters to a few thousand meters. Turbulence induced by buoyancy
forces in the atmosphere is closely related to the vertical temperature gradient.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 12 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Temperature normally decreases with increasing height in the atmosphere. The rate at which
the temperature of air decreases with height is called Environmental Lapse Rate (ELR). It will
vary from time to time and from place to place. The atmosphere is said to be stable, neutral or
unstable according to ELR is less than, equal to or greater than Dry Adiabatic Lapse Rate
(DALR), which is a constant value of 0.98°C/100 meters.
Pasquill stability parameter, based on Pasquill – Gifford categorization, is such a meteorological
parameter, which decreases the stability of atmosphere, i.e., the degree of convective
turbulence. Pasquill has defined six stability classes ranging from `A' (extremely unstable) to `F'
(stable). Wind speeds, intensity of solar radiation (daytime insulation) and night time sky cover
have been identified as prime factors defining these stability categories.
When the atmosphere is unstable and wind speeds are moderate or high or gusty, rapid
dispersion of pollutants will occur. Under these conditions, pollutant concentrations in air will be
moderate or low and the material will be dispersed rapidly. When the atmosphere is stable and
wind speed is low, dispersion of material will be limited and pollutant concentration in air will be
high. In general worst dispersion conditions (i.e. contributing to greater hazard distances) occur
during low wind speed and very stable weather conditions, such as that at 2F weather condition
(i.e. 2 m/s wind speed and Pasquill Stability F).
Literature suggests that Category ‘D’ is most probable at coastal sites in moderate climates,
and may occur for up to 80% of the time. Hence, the Pasquill stability category best represented
for the present facilities would be category ‘D’ (neutral).
Based on the above discussions and considering the predominant wind speeds, the following
representative weather conditions are considered for reporting of hazard/ consequence
distances.
Table 5: Weather Conditions
WIND SPEED PASQUILL STABILITY
2 F
3 D
5 D
Note: For RRA Study Plot Plan (Doc. No.: A918-000-17-44-0001 Rev C) has been used.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 13 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
4. HAZARDS ASSOCIATED WITH THE FACILITIES
4.1 GENERAL
Refinery complex handles a number of hazardous materials like Hydrogen, Naphtha and other
hydrocarbons which have a potential to cause fire and explosion hazards. The toxic chemicals
like Hydrogen sulphide are also being handled in the Refinery. This chapter describes in brief
the hazards associated with these materials.
4.2 HAZARDS ASSOCIATED WITH FLAMMABLE MATERIALS
4.2.1 HYDROGEN
Hydrogen (H2) is a gas lighter than air at normal temperature and pressure. It is highly
flammable and explosive. It has the widest range of flammable concentrations in air among all
common gaseous fuels. This flammable range of Hydrogen varies from 4% by volume (lower
flammable limit) to 75% by volume (upper flammable limit). Hydrogen flame (or fire) is nearly
invisible even though the flame temperature is higher than that of hydrocarbon fires and hence
poses greater hazards to persons in the vicinity.
Constant exposure of certain types of ferritic steels to hydrogen results in the embrittlement of
the metals. Leakage can be caused by such embrittlement in pipes, welds, and metal gaskets.
In terms of toxicity, hydrogen is a simple asphyxiant. Exposure to high concentrations may
exclude an adequate supply of oxygen to the lungs. No significant effect to human through
dermal absorption and ingestion is reported. Refer to below table for properties of hydrogen. Table 7: Hazardous Properties of Hydrogen
S. No. PROPERTIES VALUES
1. LFL (%v/v) 4.12
2. UFL (%v/v) 74.2
3. Auto ignition temperature (°C) 500
4. Heat of combustion (Kcal/Kg) 28700
5. Normal Boiling point (°C) -252
6. Flash point (°C) N.A.
4.2.2 NAPHTHA AND OTHER HEAVIER HYDROCARBONS
The major hazards from these types of hydrocarbons are fire and radiation. Any spillage or loss
of containment of heavier hydrocarbons may create a highly flammable pool of liquid around the
source of release.
If it is released at temperatures higher than the normal boiling point it can flash significantly and
would lead to high entrainment of gas phase in the liquid phase. High entrainment of gas phase
in the liquid phase can lead to jet fires. On the other hand negligible flashing i.e. release at
temperatures near boiling points would lead to formation of pools and then pool fire.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 14 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Spillage of comparatively lighter hydrocarbons like Naphtha may result in formation of vapour
cloud. Flash fire/ explosion can occur in case of ignition. Refer to below table for properties of
Naphtha. Table 8: Hazardous Properties of Naphtha
S. No. PROPERTIES VALUES
1. LFL (%v/v) 0.8
2. UFL (%v/v) 5.0
3. Auto ignition temperature (°C) 228
4. Heat of combustion (Kcal//Kg) 10,100
5. Normal Boiling point (°C) 130 -155
6. Flash point (°C) 38 - 42
4.3 HAZARDS ASSOCIATED WITH TOXIC/CARCINOGENIC MATERIALS
4.3.1 HYDROGEN SULPHIDE
Hydrogen sulphide is a known toxic gas and has harmful physiological effects. Accidental
release of hydrocarbons containing hydrogen sulphide poses toxic hazards to exposed
population. Refer to below table for hazardous properties of Hydrogen Sulphide.
Table 9: Toxic Effects of Hydrogen Sulphide
S. No. THRESHOLD LIMITS CONCENTRATION (PPM)
1. Odor threshold 0.0047
2. Threshold Limit Value(TLV) 10
3. Short Term Exposure Limit (STEL) (15 Minutes) 15
4. Immediately Dangerous to Life and Health (IDLH) level (for 30
min exposure) 100
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 15 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
5. HAZARD IDENTIFICATION
5.1 GENERAL
A classical definition of hazard states that hazard is in fact the characteristic of
system/plant/process that presents potential for an accident. Hence all the components of a
system/plant/process need to be thoroughly examined in order to assess their potential for
initiating or propagating an unplanned event/sequence of events, which can be termed as an
accident.
In Risk Analysis terminology a hazard is something with the potential to cause harm. Hence the
Hazard Identification step is an exercise that seeks to identify what can go wrong at the major
hazard installation or process in such a way that people may be harmed. The output of this step
is a list of events that need to be passed on to later steps for further analysis.
The potential hazards posed by the facility were identified based on the past accidents, lessons
learnt and a checklist. This list includes the following elements.
Large hole leak from drain line from the process vessel.
Small hole, cracks or small bore failure (i.e. instrument tapping failure, drains/vents failure
etc.) in piping and vessels.
Flange leaks.
5.2 MODES OF FAILURE
There are various potential sources of large leakage, which may release hazardous chemicals
and hydrocarbon materials into the atmosphere. These could be in form of gasket failure in
flanged joints, bleeder valve left open inadvertently, an instrument tubing giving way, pump seal
failure, guillotine failure of equipment/ pipeline or any other source of leakage. Operating
experience can identify lots of these sources and their modes of failure. A list of general
equipment and pipeline failure mechanisms is as follows:
Material/Construction Defects
Incorrect selection or supply of materials of construction
Incorrect use of design codes
Weld failures
Failure of inadequate pipeline supports
Pre-Operational Failures
Failure induced during delivery at site
Failure induced during installation
Pressure and temperature effects
Overpressure
Temperature expansion/contraction (improper stress analysis and support design)
Low temperature brittle fracture (if metallurgy is incorrect)
Fatigue loading (cycling and mechanical vibration)
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 16 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Corrosion Failures
Internal corrosion (e.g. ingress of moisture)
External corrosion
Cladding/insulation failure (e.g. ingress of moisture)
Cathodic protection failure, if provided
Failures due to Operational Errors
Human error
Failure to inspect regularly and identify any defects
External Impact Induced Failures
Dropped objects
Impact from transport such as construction traffic
Vandalism
Subsidence
Strong winds
Failure due to Fire
External fire impinging on pipeline or equipment
Rapid vaporization of cold liquid in contact with hot surfaces
5.3 SELECTED FAILURE CASES
A list of selected failure cases was prepared based on process knowledge, engineering
judgment, experience, past incidents associated with such facilities and considering the general
mechanisms for loss of containment. A list of cases has been identified for the consequence
analysis study based on the following.
Cases with high chance of occurrence but having low consequence:
Example of such failure cases includes two-bolt gasket leak for flanges, instrument
tapping failure at pump discharge, etc. The consequence results will provide enough data
for planning routine safety exercises. This will emphasize the area where operator's
vigilance is essential.
Cases with low chance of occurrence but having high consequence:
Example includes large hole leak of lines, process pressure vessels, etc.
This approach ensures at least one representative case of all possible types of accidental
failure events, is considered for the consequence analysis. List of scenarios along with the
Hazard distances are attached as Annexure-I. Moreover, the list of scenarios includes at least
one accidental case comprising of release of different sorts of highly hazardous materials
handled in the refinery.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 17 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
6. CONSEQUENCE ANALYSIS
6.1 GENERAL
Consequence analysis involves the application of the mathematical, analytical and computer
models for calculation of the effects and damages subsequent to a hydrocarbon / toxic release
accident.
Computer models are used to predict the physical behaviour of hazardous incidents. The model
uses below mentioned techniques to assess the consequences of identified scenarios:
Modeling of discharge rates when holes develop in process equipment/pipe work.
Modeling of the size & shape of the flammable/toxic gas clouds from releases in the
atmosphere.
Modeling of the flame and radiation field of the releases that are ignited and burn as jet
fire, pool fire and flash fire.
Modeling of the explosion fields of releases which are ignited away from the point of
release.
The different consequences (flash fire, pool fire, jet fire and explosion effects) of loss of
containment accidents depend on the sequence of events & properties of material released
leading to the either toxic vapour dispersion, fire or explosion or both.
6.2 CONSEQUENCE ANALYSIS MODELLING
6.2.1 DISCHARGE RATE
The initial rate of release through a leak depends mainly on the pressure inside the equipment,
size of the hole and phase of the release (liquid, gas or two-phase). The release rate decreases
with time as the equipment depressurizes. This reduction depends mainly on the inventory and
the action taken to isolate the leak and blow-down the equipment.
6.2.2 DISPERSION
Releases of gas into the open air form clouds whose dispersion is governed by the wind, by
turbulence around the site, the density of the gas and initial momentum of the release. In case
of flammable materials the sizes of these gas clouds above their Lower Flammable Limit (LFL)
are important in determining whether the release will ignite. In this study, the results of
dispersion modelling for flammable materials are presented LFL quantity.
6.2.3 FLASH FIRE
A flash fire occurs when a cloud of vapours/gas burns without generating any significant
overpressure. The cloud is typically ignited on its edge, remote from- the leak source. The
combustion zone moves through the cloud away from the ignition point. The duration of the
flash fire is relatively short but it may stabilize as a continuous jet fire from the leak source. For
flash fires, an approximate estimate for the extent of the total effect zone is the area over which
the cloud is above the LFL.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 18 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
6.2.4 JET FIRE
Jet fires are burning jets of gas or atomized liquid whose shape is dominated by the momentum
of the release. The jet flame stabilizes on or close to the point of release and continues until the
release is stopped. Jet fire can be realized, if the leakage is immediately ignited. The effect of
jet flame impingement is severe as it may cut through equipment, pipeline or structure. The
damage effect of thermal radiation is depended on both the level of thermal radiation and
duration of exposure.
6.2.5 POOL FIRE
A cylindrical shape of the pool fire is presumed. Pool-fire calculations are then carried out as
part of an accidental scenario, e.g. in case a hydrocarbon liquid leak from a vessel leads to the
formation of an ignitable liquid pool. First no ignition is assumed, and pool evaporation and
dispersion calculations are being carried out. Subsequently late pool fires (ignition following
spreading of liquid pool) are considered. If the release is bunded, the diameter is given by the
size of the bund. If there is no bund, then the diameter is that which corresponds with a
minimum pool thickness, set by the type of surface on which the pool is spreading.
6.2.6 VAPOR CLOUD EXPLOSION
A vapour cloud explosion (VCE) occurs if a cloud of flammable gas burns sufficiently quickly to
generate high overpressures (i.e. pressures in excess of ambient). The overpressure resulting
from an explosion of hydrocarbon gases is estimated considering the explosive mass available
to be the mass of hydrocarbon vapour between its lower and upper explosive limits.
6.2.7 TOXIC RELEASE
The aim of the toxic risk study is to determine whether the operators in the plant, people
occupied buildings and the public are likely to be affected by toxic substances. Toxic gas cloud
e.g. H2S, etc. was undertaken to the Immediately Dangerous to Life and Health concentration
(IDLH) limit to determine the extent of the toxic hazard created as the result of loss of
containment of a toxic substance.
6.3 SIZE AND DURATION OF RELEASE
Leak size considered for selected failure cases are listed below2.
Table 10: Size of Release
EQUIPMENT DESCRIPTION SIZE OF RELEASE
Process vessel / Column Large Hole Leak (50 mm)
Pump Instrument tapping failure (20 mm)
Exchanger Flange Leak (10 mm)
Process Piping Instrument tapping failure (20 mm)
2 Refer to Guideline for Quantitative Risk assessment ‘Purple Book’.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 19 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
The discharge duration is taken as 10 minutes for continuous release scenarios as it is
considered that it would take plant personnel about 10 minutes to detect and isolate the leak3.
6.4 DAMAGE CRITERIA
In order to appreciate the damage effect produced by various scenarios, physiological/physical
effects of the blast wave, thermal radiation or toxic vapour exposition are discussed.
6.4.1 LFL OR FLASH FIRE
Hydrocarbon vapour released accidentally will spread out in the direction of wind. If a source of
ignition finds an ignition source before being dispersed below lower flammability limit (LFL), a
flash fire is likely to occur and the flame will travel back to the source of leak. Any person caught
in the flash fire is likely to suffer fatal burn injury. Therefore, in consequence analysis, the
distance of LFL value is usually taken to indicate the area, which may be affected by the flash
fire.
Flash fire (LFL) events are considered to cause direct harm to the population present within the
flammability range of the cloud. Fire escalation from flash fire such that process or storage
equipment or building may be affected is considered unlikely.
6.4.2 THERMAL HAZARD DUE TO POOL FIRE & JET FIRE
Thermal radiation due to pool fire, jet fire or fire ball may cause various degrees of burn on
human body and process equipment. The damage effect due to thermal radiation intensity is
tabulated below. Table 11: Damage Due to Incident Thermal Radiation Intensity
INCIDENT RADIATION
INTENSITY (KW/M²) TYPE OF DAMAGE
37.5 Sufficient to cause damage to process equipment
32.0 Maximum flux level for thermally protected tanks containing flammable
liquid
12.5 Minimum energy required for piloted ignition of wood, melting of plastic
tubing etc.
8.0 Maximum heat flux for un-insulated tanks
4.0 Sufficient to cause pain to personnel if unable to reach cover within 20
seconds. However blistering of skin (1st degree burns) is likely.
The hazard distances to the 37.5 kW/m2, 32 kW/m2, 12.5 kW/m2, 8 kW/m2 and 4 kW/m2
radiation levels, selected based on their effect on population, buildings and equipment were
modelled using PHAST.
3 Release duration is based on Chemical Process Quantitative Risk Analysis, CCPS.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 20 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
6.4.3 VAPOR CLOUD EXPLOSION
In the event of explosion taking place within the plant, the resultant blast wave will have
damaging effects on equipment, structures, building and piping falling within the overpressure
distances of the blast. Tanks, buildings, structures etc. can only tolerate low level of
overpressure. Human body, by comparison, can withstand higher overpressure. But injury or
fatality can be inflicted by collapse of building of structures. The damage effect of blast
overpressure is tabulated below.
Table 12: Damage Effects of Blast Overpressure
BLAST OVERPRESSURE (PSI) DAMAGE LEVEL
5.0 Major structure damage
3.0 Oil storage tank failure
2.5 Eardrum rupture
2.0 Repairable damage, pressure vessels remain intact, light
structures collapse
1.0 Window pane breakage possible, causing some injuries
The hazard distances to the 5 psi, 3 psi and 2 psi overpressure levels, selected based on their
effects on population, buildings and equipment were modelled using PHAST.
6.4.4 TOXIC HAZARD
The inhalation of toxic gases can give rise to effects, which range in severity from mild irritation
of the respiratory tract to death. Lethal effects of inhalation depend on the concentration of the
gas to which people are exposed and on the duration of exposure. Mostly this dependence is
nonlinear and as the concentration increases, the time required to produce a specific injury
decreases rapidly.
The hazard distances to Immediately Dangerous to Life and Health concentration (IDLH) limit is
selected to determine the extent of the toxic hazard Created as the result of loss of containment
of a toxic substance.
6.5 CONSEQUENCE ANALYSIS OF THE SELECTED FAILURE CASES
This section discusses the associated consequences of selected credible failure scenarios. The
consequence results are reported in tabular form for all weather conditions as an Annexure-I
and are represented graphically in Annexure-II for the selected failure scenario in a unit
causing worst consequences.
NOTE: Equipment locations has been considered in the centerline of the unit for the new
proposed unit.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 21 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
6.5.1 GTU
Large Hole at Bottom Outlet of Feed Surge Drum: From the consequence results and graphs of
the selected credible scenario, it can be concluded that LFL may be extended up to a distance
of 145 m. The Jet Fire radiation intensity of 37.5 & 12.5 kW/m2 would spread up to a distance
of 73 m & 90 m respectively. The Pool Fire radiation intensity of 37.5 & 12.5 kW/m2 would
spread up to a distance of 75 m & 121 m respectively. The 5 & 3 psi blast overpressures travel
up to a distance of 194 m & 214 m respectively.
Instrument Tapping Failure at Feed Pump: From the consequence analysis of selected failure
scenario it can be observed that LFL shall be travelling up to a distance of 97 m. The Jet Fire
radiation intensity of 37.5 & 12.5 kW/m2 would extend up to a distance of 49 m & 60 m
respectively. The Pool Fire radiation intensity of 37.5 & 12.5 kW/m2 would extend up to a
distance of 28 m & 35 m respectively. The 5 & 3 psi blast overpressures travel up to a distance
of 113 m & 122 m respectively.
Instrument Tapping Failure at H2 Make Up Gas Compressor: From the event outcome of the
selected failure scenario it can be observed that LFL may be extended up to a distance of 20 m.
The Jet Fire radiation intensity of 37.5 kW/m2 is not realized & 12.5 kW/m2 may spread up to
distance of 13 m. The 5 & 3 psi blast waves may reach up to a distance of 26 m & 28 m
respectively.
Large Hole at Bottom Outlet of Splitter Reflux Drum: From the incident outcome analysis of the
selected failure scenario it is observed that LFL hazard distance is extended up to 119 m. The
Jet Fire radiation intensity of 37.5 & 12.5 kW/m2 would extend up to a distance of 67 m & 82 m
respectively. The Pool Fire radiation intensity of 37.5 kW/m2 is not realized & 12.5 kW/m2 will
extend up to a distance of 29 m. The 5 & 3 psi blast waves may reach up to a distance of 150 m
& 165 m.
Instrument Tapping Failure at Ist Stage HDS Pump: From the event outcome of the selected
failure scenario it can be observed that LFL may be extended up to a distance of 65 m. The Jet
Fire radiation intensity of 37.5 & 12.5 kW/m2 would be getting extended up to 45 m & 55 m
respectively. The Pool Fire radiation intensity of 37.5 & 12.5 kW/m2 would be getting extended
up to 36 m & 47 m respectively. The 5 & 3 psi blast waves may reach up to a distance of 76 m
& 82 m respectively.
Instrument Tapping Failure at H2S Stripper Inlet Line-Toxic: From the consequence analysis of
the selected failure scenario it can be observed that LFL may be extended up to a distance of
90 m. The Jet Fire radiation intensity of 37.5 & 12.5 kW/m2 would be getting extended up to 45
m & 55 m respectively. The Pool Fire radiation intensity of 37.5 & 12.5 kW/m2 would be getting
extended up to 42 m & 60 m respectively. The 5 & 3 psi blast waves may reach up to a distance
of 100 m & 107 m respectively. The H2S IDLH concentration may travel upto a downwind
distance of 18 m from the leak source.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 22 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Instrument Tapping Failure at Amine KO Drum - Toxic: From the event outcome of the selected
failure scenario it can be observed that LFL may be extended up to a distance of 17 m. The 5 &
3 psi blast wave may reach up to a distance of 14 m and 15 m respectively. The H2S IDLH
concentration may not reach to the ground but can travel a downwind distance of 23 m at height
of 7 m from the leak source.
Instrument Tapping Failure at Recycle Gas Compressor: From the consequence analysis, it is
observed that for this failure scenario LFL may spread up to a distance of 18 m. The Jet Fire
Radiation of 37.5 kW/m2 is not realized & 12.5 kW/m2 can reach up to a distance of 12 m. The 5
& 3 psi blast wave may reach up to a distance of 14 m and 15 m respectively.
Flange Leakage at IInd Stage HDS Feed Pump: From the event outcome of the selected failure
scenario it can be observed that LFL may be extended up to a distance of 25 m. The Jet Fire
Radiation of 37.5 kW/m2 & 12.5 kW/m2 can reach up to a distance of 26 m & 31 m respectively.
The Pool Fire Radiation of 37.5 kW/m2 & 12.5 kW/m2 can reach up to a distance of 23 m & 33
m respectively. The 5 & 3 psi blast wave may reach up to a distance of 27 m and 30 m
respectively.
Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic: From the
consequence analysis results for this failure scenario it is realized that LFL shall travel up to a
distance of 16 m. The 5 & 3 psi blast wave may reach up to a distance of 14 m and 15 m
respectively. The H2S IDLH concentration may not reach to the ground but can travel a
downwind distance of 7 m at a height of 4 m from the leak source.
Large Hole at Bottom Outlet of IInd Stage Cold Separator - Toxic: From the incident outcome
analysis, it is observed that for this failure scenario LFL may spread up to a distance of 271 m.
The Jet Fire Radiation of 37.5 & 12.5 kW/m2 can reach up to a distance of 100 m & 124 m
respectively. The Pool Fire Radiation of 37.5 kW/m2 and 12.5 kW/m2 can reach up to a distance
of 77 m & 107 m respectively. The 5 & 3 psi blast wave can extend up to a distance of 327 m &
352 m respectively. The IDLH concentration of H2S may reach up to a distance of 35 m from
the leak source.
Instrument Tapping Failure at HCN Product Pump: From the event outcome of the selected
failure scenario it can be observed that LFL may be extended up to a distance of 47 m. The Jet
Fire Radiation of 37.5 & 12.5 kW/m2 can reach up to a distance of 36 m & 44 m respectively.
The 5 & 3 psi blast wave can spread up to a distance of 52 m & 56 m respectively.
Large Hole at Bottom Outlet of Stabilizer Reflux Drum - Toxic: From the incident outcome
analysis of the selected failure scenario it is observed that LFL hazard distance is extended up
to a distance of 136 m. The Jet Fire Radiation Intensity of 37.5 & 12.5 kW/m2 can spread up to a
distance of 84 m and 101 m respectively. The 5 & 3 psi blast wave can extend up to a distance
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 23 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
of 163 m & 175 m respectively. The IDLH concentration of H2S may reach up to a distance of
86 m from the leak source.
Flange Leakage at Stabilizer Reflux Pump - Toxic: From the incident outcome analysis, it is
observed that for this failure scenario LFL may spread up to a distance of 18 m. The Jet Fire
Radiation of 37.5 & 12.5 kW/m2 can reach up to a distance of 21 m & 25 m respectively. The 5
& 3 psi blast wave can extend up to a distance of 14 m & 16 m respectively. The H2S IDLH
concentration may travel a downwind distance of 11 m.
Instrument Tapping Failure at Stabilizer Reflux Drum Overhead - Toxic: From the consequence
analysis results for this failure scenario it is realized that LFL shall travel up to a distance of 6 m.
The H2S IDLH concentration may not reach to the ground but can travel a downwind distance of
70 m at a height of 10 m from the leak source.
6.5.2 DHT ATU
Instrument Tapping Failure at Amine Regenerator Reflux Drum Ovhd.-Toxic: Instrument tapping
failure in the Amine Regeneration Reflux drum overhead piping has been considered for risk
analysis. From the report it is observed that the flash fire hazard would be realized. Hazard due
to flash fire would be restricted within the unit boundary. But the toxic effect due to the H2S leak
would affect hazardously up to a distance of 98 m from the source of leak.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 24 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
7. MAJOR FINDINGS AND RECOMMENDATIONS
The major findings and recommendations arising out of the Rapid Risk analysis study for GTU
Project of BPCL Mumbai Refinery are summarized below:
Consequence modelling for High frequency credible scenarios of Gasoline Treatment Unit
was carried out and it is observed that LFL & Blast overpressure effect zones in the event of
Instrument Tapping Failure at Feed Pump, H2 Make Up Gas Compressor, Ist Stage HDS
Feed Pump, H2S stripper Inlet Line, HCN Product Pump and Flange Leakage at Stabilizer
Reflux Pump, IInd Stage HDS Feed Pump, may extend beyond the battery limits of the unit
and damage the equipment’s in the nearby process units, depending upon the prevalent
wind conditions & ignition source encountered at the time of release. It may also effect the
nearby FCCU Control Room based on the location of the equipment’s in the unit (FCC
Control Room is being converted to Blast resistant construction separately by BPCL-MR).
The 37.5 & 12.5 kW/m2 radiation intensities of Jet & Pool fire may also produce damaging
effects within the unit and even beyond the unit.
In order to mitigate the hazardous effect zones of the above said scenarios, following is
recommended:
Install hydrocarbon detectors within the units at strategic locations.
Classify the Road No. 7, B-53 & 14 for emergency vehicles only and minimize vehicle
movement on the road no. 9, to prevent any chances of ignition.
No operator cabin to be located in the vicinity of unit.
Ensure suitable radiation protection for the ISBL pipe-rack & OSBL (Northern, Eastern,
& Western) Pipe-rack adjacent to the unit.
Low frequency & high consequence credible failure scenarios are also modelled in Gasoline
Treatment Unit for the equipment handling bulk inventories. From consequence modelling it
is observed that the flammable & explosion effect zones for Large Hole scenarios in Feed
Surge Drum, Splitter Reflux Drum, IInd Stage Cold Separator, Stabilizer Reflux Drum are
crossing the unit’s B/L’s and may cause damage.
Being low frequency scenario, outcomes of these scenarios to be utilized for preparation of
the Disaster Management Plan & Emergency Response Guidelines for the Refinery.
Requirement of remote operated isolation valves at the bottom of the bulk inventory vessels
may be reviewed during detailed engineering stage for the early inventory isolation, as the
unit is located in already congested area.
Toxic Scenarios are also modelled for the Gasoline Treatment Unit, it is observed that for
high frequency credible failure scenarios, H2S IDLH concentration may extend beyond the
B/L of the unit, depending upon the prevalent direction of the wind at the time of release.
However, it may not reach the grade level.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 25 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
It is recommended to install H2S detectors with Hooter (Local Alarm) at the strategic
locations within the unit, near to the equipment’s handling toxic material. Individual’s to be
evacuated on priority from area around Gasoline Treatment Unit in event of any toxic
release from the unit. These scenarios to be also utilized for preparation of the Disaster
Management Plan & Emergency Response Guidelines for the Refinery. Wind socks to be
installed near the GTU.
Toxic Scenarios is modelled for the existing ATU in DHT Block, it is observed that H2S IDLH
hazard effect zone for credible failure scenario may not reach grade level but toxic cloud
may spread throughout the unit.
It is recommended to ensure H2S detectors with Hooter (Local Alarm) at the strategic
locations within the unit, near to the equipment’s handling toxic material.
Recommendations for Construction Safety during execution of the GTU Project
Adequate barricading of the new proposed / revamp unit to be done from existing running
process units during construction phase. Hydrocarbon / toxic detectors to be placed along
the barricading suitably to detect any hydrocarbon / toxic gas in vicinity of construction
area. Also, adequate fire-fighting & toxic gas handling arrangement are to be ensured in the
construction area. Ensure training of persons associated with construction activities for
response during fire & toxic gas release.
Proper material movement path within the Refinery shall be identified during the
construction phase of the project.
Detailed HSE Plan & HSE Philosophy to be developed by contractors during construction
phase of the project, in line with client’s safety requirements.
It is recommended to identify & analyze the possible hazards during construction phase
and prepare the action plan to prevent / mitigate the same, as the proposed unit is located
in the already congested area of the running process units.
GENERAL RECOMMENDATIONS
For positively pressurized building, both Hydrocarbon & Toxic detectors need to be placed
at suction duct of HVAC. HVAC to be tripped automatically in event of the detection of any
Hydrocarbon / toxic material by detector.
Mitigating measures
Mitigating measures are those measures in place to minimize the loss of containment event and
thereby hazard associated. These include:
Rapid detection of an uncommon event (HC leak, Toxic gas leak, Flame etc.) and alarm
arrangements and development of subsequent quick isolation mechanism for major
inventory.
Measures for controlling / minimization of Ignition sources inside the Refinery complex.
Active and passive fire protection for critical equipment’s and major structures.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 26 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Effective Emergency Response plans to be in place.
Detection and isolation
In order to ensure rapid detection of hazardous events the following is recommended:
Ensure installation of flammable / toxic gas detection and fire detectors at strategic locations
for early detection and prevention of an uncommon event emanating from the process
facilities. Once the flammable / toxic gas release has been detected, as the gas or
subsequent fire, toxic and escalation risk will be reduced by isolation of the major inventory
from the release location (prevention of loss of containment). Hence, manual / automated
mechanism is required to isolate the major inventory during any uncommon event.
It is recommended that the storage vessels (column bottom, reflux drum, feed surge drums,
storage tanks etc.) which are dealing with very large inventory should be considered to have
remote operated valves so that these valves can be closed from the safe location upon fire
or flammable gas detection.
Ignition control
Ignition control will reduce the likelihood of fire events. This is the key for reducing the risk
within facilities that process flammable materials. As part of mitigation measure it is strongly
recommended to consider minimize the traffic movement within the refinery complex.
Escape routes
Provide windsocks throughout the site to ensure visibility from all locations. This will enable
people to escape upwind or crosswind from flammable / toxic releases. Sufficient escape routes
from the site should be provided to allow redundancy in escape from all areas.
Preventive maintenance for critical equipment’s
In order to further reduce the probability of catastrophes efficient monitoring of vessel
internals during shut-down to be carried out for Surge Drums & Reflux drums and critical
vessels whose rupture would lead to massive consequences based upon the outcomes of
RRA study.
The vehicles entering the refinery should be ensured to be fitted with spark arrestors.
In order to prevent secondary incident arising from any failure scenario, it is recommended
that sprinklers and other protective devices provided on the tanks to be regularly checked to
ensure that they are functional.
Routine check to be ensured in the area to prevent presence of any potential ignition source
in the vicinity of the refinery.
Others
Removal of hammer blinds from the process facilities to be considered.
Closed sampling system to be considered for pressurized services like LPG, Propylene etc.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 27 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Whenever a person visits for sampling and maintenance etc. it is always recommended one
should carry portable H2S / Chlorine detectors.
Provide breathing apparatus at strategic locations inside Refinery.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 28 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
8. GLOSSARY
CASUALTY Someone who suffers serious injury or worse i.e. including fatal
injuries. As a rough guide fatalities are likely to be half the total
casualties. But this may vary depending on the nature of the event.
HAZARD A chemical or physical condition with the potential of causing
damage.
FLAMMABILITY LIMITS In fuel-air systems, a range of compositions exists inside which a
(UFL – LFL) flame will propagate substantial distance from an
ignition source. The limiting fuel concentrations are termed as Upper
flammability or explosives limit (Fuel concentrations exceeding this
are too rich) and Lower flammability or explosives limit (Fuel
concentrations below this are too lean).
FLASH FIRE The burning of a vapor cloud at very low flame propagation speed.
Combustion products are generated at a rate low enough for
expansion to take place easily without significant overpressure ahead
or behind the flame front. The hazard is therefore only due to thermal
effects.
OVERPRESSURE Maximum pressure above atmosphere pressure experiences during
the passage of a blast wave from an explosion expressed in this
report as pounds per square inch (psi).
EXPLOSION A rapid release of energy, which causes a pressure discontinuity or
shock wave moving away from the source. An explosion can be
produced by detonation of a high explosive or by the rapid burning of
a flammable gas cloud. The resulting overpressure is sufficient to
cause damage inside and outside the cloud as the shock wave
propagation into the atmosphere beyond the cloud. Some authors
use the term deflagration for this type of explosion
DOMINO EFFECT The effect that loss of containment of one installation leads to loss of
containment of other installations
EVENT TREE A logic diagram of success and failure combinations of events used
to identify accident sequences leading to all possible consequences
of a given initiating event.
TLV “Threshold limit value” is defined as the concentration of the
substance in air that can be breathed for five consecutive 8 hours
work day (40 hours work week) by most people without side effect.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 29 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
STEL “Short Term Exposure Limit” is the maximum permissible average
exposure for the time period specified (15 minutes).
IDLH “Immediate Dangerous to Life and Health” is the maximum
concentration level from which one could escape within 30 minutes
without any escape impairing symptoms.
PASQUILL CLASS Classification to qualify the stability of the atmosphere, indicated by a
letter ranging from A, for very unstable, to F, for stable.
FREQUENCY The number of times an outcome is expected to occur in a given
period of time.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 30 of 30
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
9. REFERENCES
a. Classification of hazardous locations, A. W. Cox, F. P. Lees and M. L. Ang, Published
by the Institute of Chemical engineers, U. K.
b. The reference manual, Volume-II, Cremer & Warner Ltd. U. K. (Presently Entec).
c. Risk analysis of six potentially hazardous industrial objects in the Rijnmond area; A pilot
study. A report to the Rijnmond Public Authority. D. Riedel publishing company, U. K.
d. Loss prevention in the process industries, Hazard identification, Assessment and
Control, Frank. P. Lees (Vol. I, II & III), Published by Butterworth-Heinemann, U. K.
e. AICHE, CCPS, Chemical process Quantitative Risk Analysis
f. Guideline for Quantitative Risk assessment, ‘Purple book’.
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 1 of 3
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Annexure-I
Hazard Distances
Temp.
(OC)Press.
(Kg/cm2g) 4 KW/m212.5 KW/m2
37.5 KW/m24 KW/m2
12.5 KW/m237.5 KW/m2 2 psi 3 psi 5 psi
2 F 145 119 90 73 189 121 75 236 214 194 -
3 D 123 114 85 68 184 119 78 180 166 154 -
5 D 97 108 79 63 179 119 82 136 126 116 -
2 F 97 78 60 49 42 35 28 131 122 113 -
3 D 87 76 57 46 - - - 112 104 98 -
5 D 77 73 54 42 - - - 99 93 87 -
2 F 20 18 13 NR - - - 31 28 26 -
3 D 18 18 14 NR - - - 18 16 14 -
5 D 18 19 16 NR - - - 18 16 14 -
2 F 119 106 82 67 63 29 NR 181 165 150 -
3 D 103 101 77 62 68 29 NR 149 138 128 -
5 D 81 95 71 57 74 30 NR 121 111 103 -
2 F 65 72 55 45 62 47 36 88 82 76 -
3 D 60 69 52 42 64 53 41 85 79 74 -
5 D 62 67 49 39 63 55 45 84 79 74 -
2 F 90 73 55 45 84 60 42 115 107 100 H2S - 18
3 D 77 70 53 42 81 59 43 97 91 86 H2S - NR
5 D 66 67 49 39 77 58 45 86 80 74 H2S - NR
2 F 17 10 NR NR - - - 17 15 14 H2S - NR
3 D 16 10 NR NR - - - 16 15 14 H2S - NR
5 D 14 11 NR NR - - - 16 15 13 H2S - NR
2 F 18 16 12 NR - - - 17 15 14 -
3 D 17 16 12 NR - - - 17 15 14 -
5 D 16 16 13 NR - - - 17 15 14 -
2 F 25 41 31 26 50 33 23 33 30 27
3 D 22 39 30 24 52 37 24 32 29 27
5 D 19 38 28 22 54 41 25 19 17 15
2 F 16 10 NR NR - - - 17 15 14 H2S - NR
3 D 15 10 NR NR - - - 16 15 14 H2S - NR
5 D 14 11 NR NR - - - 16 15 13 H2S - NR
2 F 271 163 124 100 151 107 77 379 352 327 H2S - 35
3 D 229 158 118 94 - - - 310 289 271 H2S - 30
5 D 185 151 110 86 - - - 257 240 224 H2S - 27
2 F 47 58 44 36 - - - 61 56 52 -
3 D 43 56 42 34 - - - 59 54 51 -
5 D 42 54 40 31 - - - 58 54 50 -
2 F 136 130 101 84 - - - 188 175 163 H2S - 86
3 D 135 125 95 78 - - - 179 168 158 H2S - 81
5 D 140 120 90 72 - - - 178 167 157 H2S - 84
2 F 18 32 25 21 - - - 17 16 14 H2S - NR
3 D 16 31 24 20 - - - 17 15 14 H2S - NR
5 D 13 30 22 18 - - - 17 15 14 H2S - NR
GTU
3 H2 Make-up Gas Compressor Instrument Tapping Failure 30 24 0.4
2 Feed Pump
Pool Fire (m) Blast Over Pressure (m)IDLH Hazard
Distances (m)Remarks
1 Feed Surge Drum Large Hole on Bottom Outlet 60 2.5 22.3
Unit Sl No. Equipment Failure Case
Operating Conditions
Leak Rate
Kg/s WeathersFlash Fire
(m)
Jet Fire (m)
Instrument Tapping Failure 60 25.3 11.3
5 Ist Stage HDS Pump Instrument Tapping Failure 167 21.9 10.1
4 Splitter Reflux Drum Large Hole on the Bottom Outlet 45 1.3 15.3
8 Recycle Gas Compressor Instrument Tapping Failure 85 22.2 0.44
7 Amine K O Drum Instrument Tapping Failure-TOXIC 40 15 0.32
6 H2S Stripper Inlet Line Instrument Tapping Failure-TOXIC 130 16.9 9.19
10 IInd Stage Cold Separator Overhead Instrument Tapping Failure-TOXIC 55 13 0.22
9 IInd Stage HDS Feed Pump Flange Leakage 125 22.1 2.6
Instrument Tapping Failure 180 10.1 6.67
11 IInd Stage Cold Separator Large Hole on the Bottom Outlet - TOXIC 55 13 52.7
Consequence Analysis Hazard Distances
14 Stabilizer Reflux Pump Flange Leakage-TOXIC 55 9.1 1.56
13 Stabilizer Reflux Drum Large Hole on the Bottom Outlet-TOXIC 55 6.7 33.4
12 HCN Product Pump
Page 2 of 3
Temp.
(OC)Press.
(Kg/cm2g) 4 KW/m212.5 KW/m2
37.5 KW/m24 KW/m2
12.5 KW/m237.5 KW/m2 2 psi 3 psi 5 psi
GTU
Pool Fire (m) Blast Over Pressure (m)IDLH Hazard
Distances (m)Remarks
1 Feed Surge Drum Large Hole on Bottom Outlet 60 2.5 22.3
Unit Sl No. Equipment Failure Case
Operating Conditions
Leak Rate
Kg/s WeathersFlash Fire
(m)
Jet Fire (m)
Consequence Analysis Hazard Distances
2 F 6 - - - - - - - - - H2S - NR
3 D 6 - - - - - - - - - H2S - NR
5 D 6 - - - - - - - - - H2S - NR
2 F 1 - - - - - - - - - H2S - NR
3 D 1 - - - - - - - - - H2S - NR
5 D 1 - - - - - - - - - H2S - NR
GTU
DHT - ATU
0.4
1 Amine Regenerator Reflux Drum Ovhd. Instrument Tapping Failure-TOXIC 40 0.5 0.07
15 Stabilizer Reflux Drum Ovhd. Instrument Tapping Failure-TOXIC 55 6.7
Page 3 of 3
RRA Study of GTU Project BPCL Mumbai Refinery,
Mumbai
Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 1 of 62
Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved
Annexure-II
Figures for Consequence Analysis
Figure 6.5.1.1 A: GTU: Large Hole on Bottom Outlet of Feed Surge Drum; Flash Fire Distances (m)
Page 2 of 62
Figure 6.5.1.1 B: GTU: Large Hole on Bottom Outlet of Feed Surge Drum; Jet Fire Distances (m)
Page 3 of 62
Figure 6.5.1.1 C: GTU: Large Hole on Bottom Outlet of Feed Surge Drum; Pool Fire Distances (m)
Page 4 of 62
Figure 6.5.1.1 D: GTU: Large Hole on Bottom Outlet of Feed Surge Drum; Over Pressure Distances (m)
Page 5 of 62
Figure 6.5.1.2 A: GTU: Instrument Tapping Failure at Feed Pump; Flash Fire Distances (m)
Page 6 of 62
Figure 6.5.1.2 C: GTU: Instrument Tapping Failure at Feed Pump; Pool Fire Distances (m)
Page 8 of 62
Figure 6.5.1.2 D: GTU: Instrument Tapping Failure at Feed Pump; Over Pressure Distances (m)
Page 9 of 62
Figure 6.5.1.3 A: GTU: Instrument Tapping Failure at H2 Make Up Gas Compressor; Flash Fire Distances (m)
Page 10 of 62
Figure 6.5.1.3 B: GTU: Instrument Tapping Failure at H2 Make Up Gas Compressor; Jet Fire Distances (m)
Page 11 of 62
Figure 6.5.1.3 C: GTU: Instrument Tapping Failure at H2 Make Up Gas Compressor; Over Pressure Distances (m)
Page 12 of 62
Figure 6.5.1.4 A: GTU: Large Hole on the Bottom Outlet of Stripper Reflux Drum; Flash Fire Distances (m)
Page 13 of 62
Figure 6.5.1.4 B: GTU: Large Hole on the Bottom Outlet of Stripper Reflux Drum; Jet Fire Distances (m)
Page 14 of 62
Figure 6.5.1.4 C: GTU: Large Hole on the Bottom Outlet of Stripper Reflux Drum; Pool Fire Distances (m)
Page 15 of 62
Figure 6.5.1.4 D: GTU: Large Hole on the Bottom Outlet of Stripper Reflux Drum; Over Pressure Distances (m)
Page 16 of 62
Figure 6.5.1.5 A: GTU: Instrument Tapping Failure at Ist Stage HDS Feed Pump; Flash Fire Distances (m)
Page 17 of 62
Figure 6.5.1.5 B: GTU: Instrument Tapping Failure at Ist Stage HDS Feed Pump; Jet Fire Distances (m)
Page 18 of 62
Figure 6.5.1.5 C: GTU: Instrument Tapping Failure at Ist Stage HDS Feed Pump; Pool Fire Distances (m)
Page 19 of 62
Figure 6.5.1.5 D: GTU: Instrument Tapping Failure at Ist Stage HDS Feed Pump; Over Pressure Distances (m)
Page 20 of 62
Figure 6.5.1.6 A: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Flash Fire Distances (m)
Page 21 of 62
Figure 6.5.1.6 B: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Jet Fire Distances (m)
Page 22 of 62
Figure 6.5.1.6 C: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Pool Fire Distances (m)
Page 23 of 62
Figure 6.5.1.6 D: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Over Pressure Distances (m)
Page 24 of 62
Figure 6.5.1.6 E: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; H2S IDLH Distances (m)
Page 25 of 62
Figure 6.5.1.6 F: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; H2S IDLH Distances (m)
Page 26 of 62
Figure 6.5.1.7 A: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; Flash Fire Distances (m)
Page 27 of 62
Figure 6.5.1.7 B: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; Jet Fire Distances (m)
Page 28 of 62
Figure 6.5.1.7 C: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; Over Pressure Distances (m)
Page 29 of 62
Figure 6.5.1.7 D: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; H2S IDLH Distances (m)
Page 30 of 62
Figure 6.5.1.8 A: GTU: Instrument Tapping Failure at Recycle Gas Compressor; Flash Fire Distances (m)
Page 31 of 62
Figure 6.5.1.8 B: GTU: Instrument Tapping Failure at Recycle Gas Compressor; Jet Fire Distances (m)
Page 32 of 62
Figure 6.5.1.8 C: GTU: Instrument Tapping Failure at Recycle Gas Compressor; Over Pressure Distances (m)
Page 33 of 62
Figure 6.5.1.9 A: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Flash Fire Distances (m)
Page 34 of 62
Figure 6.5.1.9 B: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Jet Fire Distances (m)
Page 35 of 62
Figure 6.5.1.9 C: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Pool Fire Distances (m)
Page 36 of 62
Figure 6.5.1.9 D: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Over Pressure Distances (m)
Page 37 of 62
Figure 6.5.1.10 A: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; Flash Fire Distances (m)
Page 38 of 62
Figure 6.5.1.10 B: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; Jet Fire Distances (m)
Page 39 of 62
Figure 6.5.1.10 C: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; Over Pressure Distances (m)
Page 40 of 62
Figure 6.5.1.10 D: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; H2S IDLH Distances (m)
Page 41 of 62
Figure 6.5.1.11 A: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Flash Fire Distances (m)
Page 42 of 62
Figure 6.5.1.11 B: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Jet Fire Distances (m)
Page 43 of 62
Figure 6.5.1.11 C: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Pool Fire Distances (m)
Page 44 of 62
Figure 6.5.1.11 D: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Over Pressure Distances (m)
Page 45 of 62
Figure 6.5.1.11 E: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; H2S IDLH Distances (m)
Page 46 of 62
Figure 6.5.1.11 F: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; H2S IDLH Distances (m)
Page 47 of 62
Figure 6.5.1.12 A: GTU: Instrument Tapping Failure at HCN Product Pump; Flash Fire Distances (m)
Page 48 of 62
Figure 6.5.1.12 B: GTU: Instrument Tapping Failure at HCN Product Pump; Jet Fire Distances (m)
Page 49 of 62
Figure 6.5.1.12 C: GTU: Instrument Tapping Failure at HCN Product Pump; Over Pressure Distances (m)
Page 50 of 62
Figure 6.5.1.13 A: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; Flash Fire Distances (m)
Page 51 of 62
Figure 6.5.1.13 B: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; Jet Fire Distances (m)
Page 52 of 62
Figure 6.5.1.13 C: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; Over Pressure Distances (m)
Page 53 of 62
Figure 6.5.1.13 D: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; H2S IDLH Distances (m)
Page 54 of 62
Figure 6.5.1.13 E: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; H2S IDLH Distances (m)
Page 55 of 62
Figure 6.5.1.14 A: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; Flash Fire Distances (m)
Page 56 of 62
Figure 6.5.1.14 B: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; Jet Fire Distances (m)
Page 57 of 62
Figure 6.5.1.14 C: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; Over Pressure Distances (m)
Page 58 of 62
Figure 6.5.1.14 D: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; H2S IDLH Distances (m)
Page 59 of 62
Figure 6.5.1.15 A: GTU: Instrument Tapping Failure at Stabilizer Reflux Drum Overhead - Toxic; Flash Fire Distances (m)
Page 60 of 62
Figure 6.5.1.15 D: GTU: Instrument Tapping Failure at Stabilizer Reflux Drum Overhead - Toxic; H2S IDLH Distances (m)
Page 61 of 62