RRA Study of GTU Project -...

RRA Study of GTU Project BPCL Mumbai Refinery,

Mumbai

Doc No.: A918-17-43-RA-0001 Rev. No.: 0 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.


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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


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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


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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.


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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.


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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.


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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.


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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)


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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)


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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.


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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.


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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.


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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


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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)


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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.


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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.


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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’.


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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.


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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.


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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.


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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


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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.


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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.


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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.


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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.


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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.


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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.


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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.


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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’.


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Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 1 of 3


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


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Doc No.: A918-17-43-RA-0001 Rev. No.: 0 Page 1 of 62


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 B: GTU: Instrument Tapping Failure at Feed Pump; Jet Fire Distances (m)

Page 7 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)

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Figure 6.5.1.6 A: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Flash Fire Distances (m)

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Figure 6.5.1.6 B: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Jet Fire Distances (m)

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Figure 6.5.1.6 C: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Pool Fire Distances (m)

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Figure 6.5.1.6 D: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; Over Pressure Distances (m)

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Figure 6.5.1.6 E: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; H2S IDLH Distances (m)

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Figure 6.5.1.6 F: GTU: Instrument Tapping Failure at H2S stripper Inlet Line; H2S IDLH Distances (m)

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Figure 6.5.1.7 A: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; Flash Fire Distances (m)

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Figure 6.5.1.7 B: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; Jet Fire Distances (m)

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Figure 6.5.1.7 C: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; Over Pressure Distances (m)

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Figure 6.5.1.7 D: GTU: Instrument Tapping Failure at Amine KO Drum - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.8 A: GTU: Instrument Tapping Failure at Recycle Gas Compressor; Flash Fire Distances (m)

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Figure 6.5.1.8 B: GTU: Instrument Tapping Failure at Recycle Gas Compressor; Jet Fire Distances (m)

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Figure 6.5.1.8 C: GTU: Instrument Tapping Failure at Recycle Gas Compressor; Over Pressure Distances (m)

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Figure 6.5.1.9 A: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Flash Fire Distances (m)

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Figure 6.5.1.9 B: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Jet Fire Distances (m)

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Figure 6.5.1.9 C: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Pool Fire Distances (m)

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Figure 6.5.1.9 D: GTU: Flange Leakage at IInd Stage HDS Feed Pump; Over Pressure Distances (m)

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Figure 6.5.1.10 A: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; Flash Fire Distances (m)

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Figure 6.5.1.10 B: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; Jet Fire Distances (m)

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Figure 6.5.1.10 C: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; Over Pressure Distances (m)

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Figure 6.5.1.10 D: GTU: Instrument Tapping Failure at IInd Stage Cold Separator Overhead - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.11 A: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Flash Fire Distances (m)

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Figure 6.5.1.11 B: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Jet Fire Distances (m)

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Figure 6.5.1.11 C: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Pool Fire Distances (m)

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Figure 6.5.1.11 D: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; Over Pressure Distances (m)

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Figure 6.5.1.11 E: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.11 F: GTU: Large Hole on the Bottom Outlet of IInd Stage Cold Separator - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.12 A: GTU: Instrument Tapping Failure at HCN Product Pump; Flash Fire Distances (m)

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Figure 6.5.1.12 B: GTU: Instrument Tapping Failure at HCN Product Pump; Jet Fire Distances (m)

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Figure 6.5.1.12 C: GTU: Instrument Tapping Failure at HCN Product Pump; Over Pressure Distances (m)

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Figure 6.5.1.13 A: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; Flash Fire Distances (m)

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Figure 6.5.1.13 B: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; Jet Fire Distances (m)

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Figure 6.5.1.13 C: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; Over Pressure Distances (m)

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Figure 6.5.1.13 D: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.13 E: GTU: Large Hole on the Bottom Outlet of Stabilizer Reflux Drum - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.14 A: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; Flash Fire Distances (m)

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Figure 6.5.1.14 B: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; Jet Fire Distances (m)

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Figure 6.5.1.14 C: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; Over Pressure Distances (m)

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Figure 6.5.1.14 D: GTU: Flange Leakage at Stabilizer Reflux Pump - Toxic; H2S IDLH Distances (m)

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Figure 6.5.1.15 A: GTU: Instrument Tapping Failure at Stabilizer Reflux Drum Overhead - Toxic; Flash Fire Distances (m)

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Figure 6.5.1.15 D: GTU: Instrument Tapping Failure at Stabilizer Reflux Drum Overhead - Toxic; H2S IDLH Distances (m)

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Figure 6.5.2.1 A: ATU: Instrument Tapping Failure at Amine Regenerator Reflux Drum Ovhd.-Toxic; H2S IDLH Distances (m)

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