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RRA Study of BS VI MS Block Project BPCL Kochi Refinery

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Template No. 5-0000-0001-T2 Rev. 1 Copyrights EIL ¬ All rights reserved

PREFACE

BPCL intends to maximize and upgrade MS processing capabilities to meet BSVI fuel

specifications by 1st April 2020. This document forms a part of EIA report for BSVI quality fuels

production.

Rapid Risk Analysis study identifies the hazards associated with the facility, analyses the

consequences, 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 .......................................................................................................... 6

1.1 INTRODUCTION ............................................................................................................... 6

1.2 APPROACH METHODOLOGY ......................................................................................... 6

1.3 MAJOR OBSERVATIONS & RECOMMENDATIONS ....................................................... 7

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, LOCATION AND VICINITY ................................................................................... 10

3.3 METEOROLOGICAL CONDITIONS ............................................................................... 10

4 HAZARDS ASSOCIATED WITH THE FACILITIES ................................................................ 14

4.1 GENERAL ....................................................................................................................... 14

4.2 HAZARDS ASSOCIATED WITH FLAMMABLE MATERIALS ......................................... 14

4.2.1 LIQUIFIED PETROLEUM GAS ................................................................................ 14

4.2.2 HYDROGEN ............................................................................................................. 14

4.2.3 NAPHTHA AND OTHER HEAVIER HYDROCARBONS .......................................... 15

4.3 HAZARDS ASSOCIATED WITH TOXIC MATERIALS .................................................... 16

4.3.1 HYDROGEN SULPHIDE .......................................................................................... 16

4.3.2 BENZENE ................................................................................................................ 16

4.3.3 TOLUENE ................................................................................................................ 17

5 HAZARD IDENTIFICATION ................................................................................................... 19

5.1 GENERAL ....................................................................................................................... 19

5.2 MODES OF FAILURE ..................................................................................................... 19

5.3 SELECTED FAILURE CASES ........................................................................................ 20

6 CONSEQUENCE ANALYSIS ................................................................................................. 22

6.1 GENERAL ....................................................................................................................... 22

6.2 CONSEQUENCE ANALYSIS MODELLING .................................................................... 22

6.2.1 DISCHARGE RATE ................................................................................................. 22


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6.2.2 DISPERSION ........................................................................................................... 22

6.2.3 FLASH FIRE ............................................................................................................. 22

6.2.4 JET FIRE .................................................................................................................. 23

6.2.5 POOL FIRE .............................................................................................................. 23

6.2.6 VAPOR CLOUD EXPLOSION ................................................................................. 23

6.2.7 TOXIC RELEASE ..................................................................................................... 23

6.3 SIZE AND DURATION OF RELEASE ............................................................................. 23

6.4 DAMAGE CRITERIA ....................................................................................................... 24

6.4.1 LFL OR FLASH FIRE ............................................................................................... 24

6.4.2 THERMAL HAZARD DUE TO POOL FIRE, JET FIRE AND FIRE BALL ................. 24

6.4.3 VAPOR CLOUD EXPLOSION ................................................................................. 25

6.4.4 TOXIC HAZARD ....................................................................................................... 25

6.5 CONSEQUENCE ANALYSIS FOR MS BLOCK .............................................................. 26

6.5.1 NHT .......................................................................................................................... 26

6.5.2 CCR .......................................................................................................................... 27

6.5.3 ISOMERIZATION UNIT ............................................................................................ 28

6.5.4 OFFSITES ................................................................................................................ 30

7 OBSERVATIONS & RECOMMENDATIONS .......................................................................... 31

8 GLOSSARY ............................................................................................................................ 36

9 REFERENCES ....................................................................................................................... 38

ANNEXURE-I: CONSEQUENCE ANALYSIS HAZARD DISTANCES

ANNEXURE-II: FIGURES FOR CONSEQUENCE ANALYSIS OF MS BLOCK

ANNEXURE-II: INDIVIDUAL RISK CONTOUR


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LIST OF TABLES

Table 1: New Proposed Process Facilities under BSVI Project ......................................................................... 9

Table 2: Atmospheric Parameter ..................................................................................................................................... 11

Table 3: Average Mean Wind Speed (m/s) ................................................................................................................. 11

Table 4: % Number of Days Wind From ....................................................................................................................... 11

Table 5: Pasquill Stability Classes................................................................................................................................... 12

Table 6: Weather Conditions .............................................................................................................................................. 13

Table 7: Hazardous Properties of LPG ......................................................................................................................... 14

Table 8: Hazardous Properties of Hydrogen .............................................................................................................. 15

Table 9: Hazardous Properties of Naphtha 15

Table 10: Toxic Effects of Hydrogen Sulphide .......................................................................................................... 16

Table 11: Hazardous Properties of Benzene ............................................................................................................. 17

Table 12: Toxic effects of Benzene ................................................................................................................................. 17

Table 13: Hazardous Properties of Toluene ............................................................................................................... 18

Table 14: Toxic effects of Toluene .................................................................................................................................. 18

Table 15: Size of Release .................................................................................................................................................... 23

Table 16: Damage Due to Incident Thermal Radiation Intensity ..................................................................... 24

Table 17: Damage Effects of Blast Overpressure ................................................................................................... 25

LIST OF FIGURES

Figure 1: BPCLKochi Refinery Site ................................................................................................ 10


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1 EXECUTIVE SUMMARY

1.1 INTRODUCTION

The Kochi Refinery of Bharat Petroleum Corporation Limited (BPCL-KR) located at Ambalamugal,

in Ernakulum District (Kerala), India, was established in 1966 and has been expanded to current

capacity of 9.5 Million Metric tons per Annum (MMTPA) through successive revamps/ new

facilities. It currently has two trains of primary distillation units (CDUI and II), secondary

processing facilities viz VGO-HDS, FCCU, DHDS, petrochemicals like benzene toluene

production facilities and other associated utilities and offsites.

As per Auto Fuel Policy 2025, The Ministry of Petroleum and Natural gas laid down a roadmap for

complete transition to BS IV automotive fuel by the end of 2017 and the transition to BS VI

automotive fuel is slated to take place and completed by 1 April 2020 in the entire country.

Though, in post IREP scenario, BPCL Kochi Refinery will be able to produce BS IV quality MS

and Diesel along with partial production of BS VI products, it will require additional facilities to

achieve BS-VI quality specifications for MS. In view of the above, BPCL intends to maximize and

upgrade MS processing capabilities to meet BSVI fuel specifications by year 1st April 2020.

BPCL intends to maximize and upgrade MS to meet BSVI fuel specifications by 1st April 2020.

This document forms a part of EIA report for BSVI quality fuels production.

1.2 APPROACH METHODOLOGY

RRA study evaluates the consequences of potential failure scenarios, assess extent of damages,

based on damage criteria’s and suggest suitable measures for mitigating the Hazard.

RRA involves identification of various potential hazards & credible or reasonably believable failure

scenarios for various units based on their frequency of occurrence & resulting consequence.

Basically 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.,Catastrophic Rupture of

Pressure Vessels / Large Hole on the outlet of Pressure Vessels. Effect zones for various

outcomes of failure scenarios (Flash Fire, Jet Fire, Pool Fire, Blast overpressure, toxic release,

etc.) are studied and identified in terms of distances on plot plan. Based on effect zones,

measures for mitigation of the hazard/risk are suggested.


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1.3 MAJOR OBSERVATIONS & RECOMMENDATIONS

The major credible failure scenarios are modeled in terms of hydrocarbon release rate,

dispersion, flammability & toxic characteristics and detailed consequence analysis of the

outcomes is presented in the Rapid Risk Analysis (RRA) report. The summary of major

observations & recommendations of RRA study for new MS block is recorded below. Refer

Section - 7 for Observations and recommendations.

High frequency credible failure scenarios for ISOM Unit are modeled. In the event of instrument

tapping failure of charge pumps, 20mm leak in the isomerate product-Stabilizer outlet, it was

observed that LFL is largely restricted within the complex boundary for the most probable wind

conditions. The 5 & 3 psi blast waves may affect adjacent existing NHT/CCR units and upcoming

facilities nearby but may not be realized beyond the complex boundaries. However to mitigate the

onsite consequences, it is recommended:

Provide sufficient number of hydrocarbon detectors within the ISOM unit for early leak

detection and develop procedures for stopping of rotating equipments and quicker

inventory isolation.

The consequences of low frequency (in the order of 1 x10-6 /M-year to 1 x10-7 /M-year) credible

cases of ISOM unit may be included for updation of the existing Disaster Management Plan

(DMP) & Emergency Response Plan (ERP).

In case of the Instrument tapping failure at Separator Pumps and Reformate product pump

instrument tapping failure of CCR unit. The IDLH toxic concentration of 500ppm may be

experienced at chemical ware house, SRR-2, gate house, fire station, QC lab, SRR-3, and

Substation (S/S-1) on the northern and eastern side of the unit with a possibility of crossing the

complex boundary on the northern and southern side and may further be realized beyond the

main road on the eastern side, based on orientation of the leak and the weather conditions

prevailing at the time of release. However, an individual risk assessment of credible leakage

scenarios has shown that IR risk contour of 1 x 10-6/Avg- year, which is considered to

demonstrate broadly acceptable region for public, is within the BPCL complex premises.

Based on preceding observations the following is recommended:

Provide adequate number of hydrocarbon detectors at suitable locations within the unit and at

the periphery of the unit for early leak detection. Also mitigating procedures such emergency

shutdown of rotating equipments and quick isolation of inventories shall be developed as a

part of the Emergency response plan & Disaster Management Plan to address the concerns

of high frequency failure scenarios.

The CCR separator and De-butanizer and reformate may preferably be located to the

western side of the piperack to maintain as much distance as possible from compound wall.


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As the Quality Control lab may be affected by the toxic concentration of Toluene, suitable no.

of breathing apparatus may be provided to be used in case of emergency based on detection

or emergency guidelines.

In the offsites, existing CCR feed Tank YT-903 may be affected by 32 & 8 KW/m2 jet fire radiation

intensities due to NHT feed pump instrument tapping failure. Also the tank YT-903 may be

subjected to direct flame impingement and may lead to escalation. It is recommended to:

Locate the new pumps atleast 40m away from the Tankage so as avoid direct flame

impingement. Review the suitability of active fire protection system of Tank YT-903 for

protection from 32KW/m2 radiation intensity.

The active fire protection system provided for storage tanks (YT-903/905) are to be

regularly checked for prompt action.

As the control room may not be exposed to LFL, but may be partially subjected to blast

overpressures, based on the prevailing site conditions and presence of ignition sources,

ensure suitable mitigation by early leak detection and automated inventory isolation.

Outcomes of the low frequency (in the order of 1 x10-6 /M-year to 1 x10-7/M-year) credible failure

scenarios for various units are recommended to be included for updating of the existing Disaster

Management Plan (DMP) & Emergency Response Plan (ERP).


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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. Typical hazardous consequences include fire,

explosion and toxic releases. The Rapid Risk analysis identifies 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 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 Risk analysis study has been carried out using the risk assessment software program

‘PHAST 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

proposed facilities under BS VI Project. It covers the following facilities of proposed BS VI project

facilities:

Table 1: New Proposed Process Facilities under BSVI Project

S. No. Description Remarks

1. NHT 1. 5MMTPA

2. CCR 0.8 MMTPA

3. ISOM 0.71 MMTPA

4. Tankages

1 NHT feed tank

1 Isom feed

1 CCR feed

5. Feed Pumps

3 No’s NHT feed

2 No’ s Isom Feed

2 No’s CCR feed


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3 SITE CONDITION

3.1 GENERAL

This chapter describes the location of BPCL Kochi Refinery complex and meteorological data,

which have been used for the Rapid Risk Analysis study.

3.2 SITE, LOCATION AND VICINITY

The BPCL Kochi Refinery is located in Ambalamugal, in Ernakulum District (Kerala). The site is

located approximately at Latitude of 9◦58’16″N and longitude of 76◦22’43″E.

Figure 1: BPCL Kochi Refinery Site

3.3 METEOROLOGICAL CONDITIONS

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

released materials. Actual behavior of any release would largely depend on prevailing weather

condition at the time of release.

For the Risk Analysis study, Meteorological data of Kochi has been taken from the QRA report of

facilities at BPCL Kochi prepared by M/s EIL, using the Climatological Tables of Observatories in

India (1961-1990) published by Indian Meteorological Department, Pune.


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Atmospheric Parameters

The Climatological data which have been used for the Risk Analysis study is summarized below:

Table 2: Atmospheric Parameter

Sl. No. Parameter Average Value Considered For Study

1. Ambient Temperature (OC) 27

2. Atmospheric Pressure (mm Hg) 760

3. Relative Humidity (%) 82

4. Solar Radiation flux (kW/m2) 0.7

Wind Speed and Wind Direction

The meteorological data considered for the study has been taken from the IMD Table (Kochi

weather station).

The averages mean speed and the wind from various directions in percentage number of days is

as in table below. It is observed from the IMD data that calm weather is experienced for 12% of

the time in the night and 1.6% in the day time. Predominant wind speed for Kochi is in the range

of 1 m/s to a maximum of 2.5 m/s. The study of oktas (all clouds) shows that the months of April

to November are very cloudy and December to March is moderately cloudy.

Table 3: Average Mean Wind Speed (m/s)

Jan Feb Mar April May June July Aug Sep Oct Nov Dec

1.58 1.7 1.9 2 1.92 1.58 1.47 1.61 1.6 1.5 1.41 1.36

Table 4: % Number of Days Wind From

N NE E SE S SW W NW Calm

Day 3.19 1.1 1.1 1.1 2.13 14.9 45.7 31.89 3.19

Night 9 29 36 9 1.8 1.8 5.4 7.2 9

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.

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


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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 nighttime sky cover have been

identified as prime factors defining these stability categories. Below Table indicates the various

Pasquill stability classes.

Table 5: Pasquill Stability Classes

Surface Wind Speed

(meter/s)

Day time solar radiation Night time cloud cover

Strong Medium Slight Thin < 3/8 Medium 3/8 Overcast >4/5

< 2 A A – B B - - D

2 – 3 A – B B C E F D

3 – 5 B B – C C D E D

5 – 6 C C – D D D D D

> 6 C D D D D D

Source: PHAST Manual A = Very unstable, B = Unstable, C = moderately unstable, D = Neutral, E = moderately stable, F = stable

Source : CCPS Book on A Guide to Quantitative Risk Analysis

Legend: A = Very unstable, B = Unstable, C = Moderately unstable, D = Neutral, E = Moderately

stable, F = stable

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


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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 1F weather condition

(i.e. 1 m/s wind speed and Pasquill Stability F).

Stability category for the present study is identified based on the cloud amount and wind speed.

For risk analysis the representative average annual weather conditions are assessed based on

the following:

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, Pasquill stability category best represented for the

present facilities would be category ‘D’ (neutral).Pasquill Stability F has been considered for

accounting the night time weather.

Table 6: Weather Conditions

Wind Speed Pasquill Stability

1 F

1.5 C/D

2.5 D

Note: For RRA Study Plot Plan (Doc. No.: A870-000-17-44-0001 Rev A) has been used.

The consequence results are reported in tabular form for all the weather conditions and are

represented graphically for worst weather condition.


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4 HAZARDS ASSOCIATED WITH THE FACILITIES

4.1 GENERAL

Refinery complex handles a number of hazardous materials like LPG, Hydrogen, Naphtha and

other hydrocarbons which have a potential to cause fire and explosion hazards. The toxic

chemicals like Benzene and Hydrogen sulfide are also 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 LIQUIFIED PETROLEUM GAS

LPG is a colorless liquefied gas that is heavier than air and may have a foul smelling odorant

added to it. It is a flammable gas and may cause flash fire and delayed ignition.

LPG is incompatible to oxidizing and combustible materials. It is stable at normal temperatures

and pressure. 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 of LPG at temperatures near boiling points would lead to formation of pools

and then pool fire. LPG releases may also lead to explosion in case of delayed ignition.

Inhalation of LPG vapors by human beings in considerable concentration may affect the central

nervous system and lead to depression. Inhalation of extremely high concentration of LPG may

lead to death due to suffocation from lack of oxygen. Contact with liquefied LPG may cause

frostbite. Refer to below table for properties of LPG.

Table 7: Hazardous Properties of LPG

Sl. No. Properties Values

1. LFL (%v/v) 1.7

2. UFL (%v/v) 9.0

3. Auto ignition temperature (°C) 420-540

4. Heat of combustion (Kcal/Kg) 10960

5. Normal Boiling point (°C) -20 to –27

6. Flash point (°C) - 60

4.2.2 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


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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 8: Hazardous Properties of Hydrogen


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.

4.2.3 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.

Spillage of comparatively lighter hydrocarbons like Naphtha may result in formation of vapor

cloud. Flash fire/ explosion can occur in case of ignition. Refer to below table for properties of

Naphtha.

Table 9: Hazardous Properties of Naphtha

S. No. Properties Values

1. LFL (%v/v) 0.8

2. UFL (%v/v) 5.0


4. Heat of combustion (Kcal//Kg) 10,100


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S. No. Properties Values

5. Normal Boiling point (°C) 130 -155

6. Flash point (°C) 38 - 42

4.3 HAZARDS ASSOCIATED WITH TOXIC MATERIALS

4.3.1 HYDROGEN SULPHIDE

Hydrogen sulfide is a known toxic gas and has harmful physiological effects. Accidental release of

hydrocarbons containing hydrogen sulfide poses toxic hazards to exposed population. Refer to

below table for hazardous properties of Hydrogen Sulphide.

Table 10: Toxic Effects of Hydrogen Sulphide

Sl. No. Threshold Limits Concentration (PPM)

1. Odor threshold 0.0047

2. Threshold Limit Value(TLV)(ACGIH) 1

3. Short Term Exposure Limit (STEL)(15 Minutes)(ACGIH) 10

4. Immediately Dangerous to Life and Health (IDLH) level (for 30

min exposure) 100

4.3.2 BENZENE

The hazards associated with benzene are both toxic and flammable hazards. Benzene has a very

low flash point (-11.1°C), indicating that its vapor cloud easily gets ignited. The vapor which is

about to 3 times heavier than air may originate flash fire and explosions.

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 of Benzene

at temperatures near boiling points would lead to formation of pools and then pool fire.

Inhaling very high concentration of Benzene vapors can result in death, while inhalation of lower

concentration can cause drowsiness, dizziness, rapid heart rate, headaches and

unconsciousness. The major effect of exposure to Benzene for a prolonged period (365 days or

longer) may adversely affect bone marrow and cause a decrease in red blood cells leading to

anemia. Benzene is a recognized carcinogenic. Refer to below tables for hazardous properties of

benzene.


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Table 11: Hazardous Properties of Benzene


1. LFL (%v/v) 1.4

2. UFL (%v/v) 8


4. Flash point (°C) - 11.1

5. Heat of combustion (KCAL/Kg) 9700

6. Normal Boiling point (°C) 80

Table 12: Toxic effects of Benzene


1. Odor threshold 0.16-320 ppm

2. Threshold Limit Value(TLV) 1

3. Short Term Exposure Limit (STEL) (15 Minutes) 5

4. Immediately Dangerous to Life and Health (IDLH) level

(for 30 min exposure)

500

5. ERPG 1 : 50

4.3.3 TOLUENE

The hazards associated with Toluene are both toxic and flammable hazards. Toluene has a very

low flash point (4.40C), indicating that its vapor cloud easily gets ignited. 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 of Toluene at temperatures

near boiling points would lead to formation of pools and then pool fire.

Inhaling very high concentration of Toluene vapors can result in death, while inhalation of lower

concentration can cause drowsiness, dizziness, rapid heart rate, headaches and

unconsciousness. The major effect of exposure to Toluene for a prolonged period (365 days or

longer) may adversely affect bone marrow and cause a decrease in red blood cells leading to

anemia. Refer Table below for hazardous properties of Toluene


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Table 13: Hazardous Properties of Toluene


1. LFL (%v/v) 1.1

2. UFL (%v/v) 7.1

3. Normal Boiling point (°C) 111.11

Table 14: Toxic effects of Toluene


1. Threshold Limit Value(TLV) 10

2. Short Term Exposure Limit (STEL) (15 Minutes) 5

3. Immediately Dangerous to Life and Health (IDLH) level

(for 30 min exposure)

500


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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 any chemical or physical condition 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.

Catastrophic Rupture of Pressure vessel

Large hole on outlet of process vessel

“Guillotine-Breakage” of pipe-work

Small hole,cracks or small bore failure (i.e. instrument tapping failure, drains/vents failure

etc.) in piping and vessels.

Flange leaks.

Storage Tank on fire

Leaks from pump glands and similar seals.

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


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Overpressure

Temperature expansion/contraction (improper stress analysis and support design)

Low temperature brittle fracture (if metallurgy is incorrect)

Fatigue loading (cycling and mechanical vibration)

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 (1 x10-4 /year), seal failure (0.6

/year) for pumps, instrument tapping failure(5 x10-4 /year), 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 (The example includes

Large hole on the outlet of pressure vessels (1 x10-6 /M-year to 1 x10-7 /M-year),

Catastrophic Rupture of Pressure Vessels (3 x10-6 /year), etc.)

This approach ensures at least one representative case of all possible types of accidental

failure events, is considered for the consequence analysis. Moreover, the list below

includes at least one accidental case comprising of release of different sorts of highly


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hazardous materials handled in the refinery. Although the list does not give complete failure

incidents considering all equipment’s, units, but the consequence of a similar incident

considered in the list below could be used to foresee the consequence of that particular

accident.

For selected credible failure scenarios and likely consequences for units under BS-VI MS Block ,

refer Section-6.

Note: References of frequencies are taken from:

Classification of Hazardous Locations, A.W.Cox, F.P.Lees and M.L.Ang, Published by the Institution of Chemical

Engineers, U.K.

Loss Prevention in the Process Industries, Hazard Identification, Assessment and Control, Frank.P.Lees, 2nd

Edition, Published by Butterworth-Heinemann, U.K.


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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 behavior 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 vapor 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

modeling for flammable materials are presented LFL quantity.

6.2.3 FLASH FIRE

A flash fire occurs when a cloud of vapors/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 vapor 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 vapor 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,

Benzene, Toluene 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 below1. Leak sizes considered here are

representative hole sizes in the upstream/ downstream circuit of particular equipment for which

failure scenario has been considered.

Table 15: Size of Release

Failure Description Leak Size

Pump seal failure 6 mm hole size

Flange gasket failure 10 mm hole size

Instrument tapping failure 20 mm hole size

1 Refer to Guideline for Quantitative Risk assessment ‘Purple Book’.


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Failure Description Leak Size

Large Hole in the Piping 50 mm, complete rupture of 2” drain line at the Process

vessel outlet

Catastrophic Rupture Complete Rupture of the Pressure Vessels

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 leak2.

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 vapor exposition are discussed.

6.4.1 LFL OR FLASH FIRE

Hydrocarbon vapor 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 AND FIRE BALL

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 16: 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

2 Release duration is based on Chemical Process Quantitative Risk Analysis, CCPS.


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Incident Radiation Intensity

(Kw/M²) Type of Damage

seconds. However blistering of skin (1stdegree 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 modeled using

PHAST.

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 17: 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 modeled 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.


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6.5 CONSEQUENCE ANALYSIS FOR MS BLOCK

This section discusses the consequences of selected failure scenarios for the upcoming BS VI

MS Block and associated offsite facilities. The consequence distances are reported in tabular

form for all weather conditions in Annexure-I and are represented graphically in Annexure-II for

the all failure scenarios in a unit for worst case weather conditions.

6.5.1 NHT

NOTE: Refer Figures 6.5.1.1 to 6.5.1.5 in Annexure-II

Instrument Tapping Failure at Feed Charge Pump: From the results of consequence analysis it is

observed that the LFL hazardous dispersion zone may reach upto 86 m from the source and may

extend beyond the B/L on the southern side. The 37.5 & 12.5 KW/m2 radiation intensities may

have effect distances of 61m and 72m respectively and may cause damage and secondary

effects within the unit. The 5 & 3 psi blast wave may extend up to a distance of 101 m & 110 m

respectively and may partially affect the adjacent VGO/HDS unit to the west and the upcoming

sub-station towards the southern side in case the scenario outcome is realized.

Large hole in the bottom of Reactor Product Separator: From the event outcome of the selected

failure scenario it can be observed that LFL may reach up to a distance of 211 m. The LFL

hazardous zone may extend beyond the plant boundary on the eastern and southern side. The

radiation intensity from 37.5kw/m2 Jet fire may affect a significant portion of the unit. The 5 & 3 psi

blast wave may reach up to a distance of 270 m & 292 m respectively and may cross the complex

boundary on the eastern side. Further affect may be noticed on the adjacent VGO/HDS on the

western side, SWS/ARU, SRU, Fuel oil tanks, S/S-1, SRR-2, gate house on the northern side,

part of new ISOM unit, new SRR and new substation on the southern side.

The toxic H2S impact distance for 100ppm cloud may not be realized in case of this scenario.

Recycle Compressor Instrument Tapping Failure: From the incident outcome analysis, it can be

observed that LFL and the subsequent consequences are largely restricted to the vicinity of the

leak. There may be possibility of localized radiation/blast overpressure damage which may cause

escalation.

Large Hole on bottom outlet of Stripper: From the consequence results and graphs of the selected

failure scenario, it can be observed that LFL may extend up to a distance of 92m and may be

realized beyond the unit boundary. The jet fire radiation intensities of 37.5 and 12.5 kW/m2 may

affect major part of the unit and may cause escalation. The 5 & 3 psi blast wave may reach up to

a distance of 112 m & 120 m respectively and extend beyond the Complex boundary on the

Southern side.

Splitter Reflux Pump Instrument tapping failure: From the consequence analysis of this high

frequency failure scenario, it is observed that LFL may extend beyond plant unit boundaries on


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the northern side of the unit. The jet fire radiation of 37.5 KW/m2 and 12.5 KW/m2 intensities are

restricted within the unit boundary and may cause escalation due to subsequent domino effects,

if realized . The 5 & 3 psi blast wave may reach up to a distance of 154 m & 167 m respectively

and may affect the equipment’s and piping in the unit leading to escalation. The blast waves may

also be realized beyond the complex boundary on the eastern side. The existing SWS/ARU

Substation S/S-1 and VGO/HDS may get affected depending on the prevailing conditions at the

time of release.

6.5.2 CCR


Instrument tapping failure at Separator Pumps: From the incident outcome analysis of this failure

scenario, it is observed that LFL distance of up to 79m may be realized beyond the unit

boundaries. The jet fire thermal radiation intensities of 37.5 and 12.5 kW/m2may be realized up to

a distance of 61 m and 73 m respectively and may lead to localized damage and escalation. In

case of no immediate ignition, the released material is expected to form a pool and the damage

due to radiation of similar intensities as jet fire may cause localized damage. The 5 & 3 psi blast

waves may have an effect zone of 98 m and 91m respectively and may affect the adjacent

VGO/HDS unit. Depending on the location of pump there is a possibility of upcoming ISOM unit

getting affected by these blast waves.

The toluene IDLH concentration of 500ppm may have a maximum effect distance of 491 m and

may affect onsite facilities such as chemical ware house, SRR-2, gate house, QC lab,

maintenance Ware house, SRR-3, and Substation (S/S-1) on the northern and eastern side of the

unit with a possibility of crossing the complex boundary on the northern and southern side and

may be further realized beyond the main road on the eastern side, based on orientation of the

leak and the prevalent weather conditions at the time of release.

In case of ethyl benzene IDLH toxic effect distances of 800 ppm for the worst case scenario may

be realized upto 236m and may affect a majority of facilities mentioned above.

Instrument tapping failure at Net gas compressor 2nd stage: From the graphs and table of incident

outcome analysis it is observed that the consequences are restricted within immediate vicinity of

loss of containment.

Instrument tapping failure in Reformate product pump : From the consequence modeling of the

selected failure scenario, it was observed that LFL may spread up to a distance of 72 m affecting

adjacent unit partially. The jet fire thermal radiation intensities of 37.5 and 12.5 kW/m2 may have

effect distances of 51m and 61 m respectively and may cause localized damage if realized. The

pool fire thermal radiation intensities of 37.5 and 12.5 kW/m2may have effect distances of 30 m

and 37m respectively and may cause localized damage if realized. The 5 & 3 psi blast wave may


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have an effect zone 85 m & 91 m respectively and may cause localized damage and possible

escalation.

The toluene IDLH concentration of 500ppm may have its effect up to a distance of 297 m and

may affect chemical ware house, SRR-2, gate house, QC lab, maintenance Ware house, SRR-3,

and Substation (S/S-1) on the northern and eastern side of the unit with a possibility of crossing

the complex boundary on the northern and southern side and extend beyond the main road on

the eastern side, based on orientation of the leak and the most prevalent weather conditions.

In case of ethyl benzene IDLH toxic effect distances of 800 ppm for the worst case scenario may

be realized upto 176m and may also have an affect on facilities mentioned above.

Large Hole in bottom Outlet of De-butanizer Receiver: From the incident outcome analysis of this

failure scenario, it is observed that LFL distance of up to 117 m may not be realized beyond the

complex boundaries. The radiation intensities of 37.5 KW/m2 and 12 KW/m2 due to jet fire in the

range of 110 m and 94 m respectively may have a bearing on the plant structures and equipment

depending on the orientation of leak and may lead to escalation. The 5 & 3 psi blast waves may

be experienced up to a distance of 138 m & 148 m respectively. The effect of blast waves may be

noticed on the adjacent VGO/HDS on the western side, SWS/ARU, SRU, S/S-1, SRR-2 on the

northern side, if realized.

Instrument tapping failure at De-butanizer Overhead Pumps: From the consequence results and

graphs of the selected failure scenario, it was observed that LFL may spread up to a distance of

47 m and may cross the unit boundary. The jet fire thermal radiation intensities of 37.5 and 12.5

kW/m2 intensity may have an effect zone of 56 m and 48 m respectively and may affect

equipment and structures inside the unit lead to escalation. The upcoming substation on the

southern side may be subjected to these radiation intensities depending upon the siting of the

equipment in the unit. The 5 & 3 psi blast wave effect zone may be realized up to a distance of 56

m & 51 m respectively from the source point possibly affecting the equipment and piping inside

unit leading to domino effects. Further, affect of these blast waves may also be noticed on the

upcoming substation on the southern side.

6.5.3 ISOMERIZATION UNIT


Instrument Tapping Failure at Charge Pump: From the consequence results and graphs of the

selected failure scenario, it was observed that LFL may be realized up to a distance of 87 m from

the point of loss of containment. The jet fire thermal radiation intensities of 37.5 and 12.5

kW/m2may be experienced up to a distance of 61m and 72 m respectively. These hazardous

intensities have a potential to affect major portion of the unit and also affect the adjacent NHT-

CCR unit depending on the release orientation. The 5 & 3 psi pressure wave effect zones can be


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experienced at a distance of 102 m & 110 m respectively from the source point. Units such as

NHT/CCR, VGO/HDS, and Upcoming SRR may be subjected to varying degrees of damage if

realized.

Large Hole on bottom outlet of Separator drum: From the incident outcome of the selected failure

scenario, it was observed that LFL may spread up to a distance of 236 m from the point of loss of

containment and may be realized beyond the complex boundary on the eastern side. The jet fire

thermal radiation intensities of 37.5 and 12.5 kW/m2 may spread up to a distance of 118 m and

141 m respectively may affect the upcoming SRR on the eastern side, adjacent NHT CCR and

VGO/HDS unit partially. The 5 & 3 psi blast wave effect zone may be up to a distance of 277 m &

294 m respectively from the source point and may affect proposed & existing NHT/CCR,

ARU/SWS, F.O tanks, VGO/HDS, Low sulphur diesel tanks in northern side, DHDS Substation,

Control room, S/S-2, SRR-1 on western side, the New boiler house, Nitrogen storage area, air

compressor, Cooling tower, CWPS caustic tank on the southern side. Towards the eastern side

the blast waves may have an effect zone well beyond the complex boundary. The pool fire

thermal radiation intensity of 12.5 kW/m2 may spread up to a distance of 39 m which is not

expected to affect any equipment beyond unit battery limit.

Instrument Tapping Failure at make-up gas Compressor: From the consequence results and

graphs of the selected failure scenario, it was observed that LFL may spread up to a distance of

25 m. The effect of jet fire thermal radiation intensity of 12.5 KW/m2 and 5 & 3 psi blast waves are

largely localized and restricted within the unit with a possibility of a domino effect if the outcome is

realized.

20mm leak at Isomerate Product-Stabilizer outlet line: From the consequence results and graphs

of the selected failure scenario, it was observed that LFL may extend up to a distance of 87 m and

may be realized beyond the unit boundaries. The jet fire thermal radiation intensities of 37.5 and

12.5 kW/m2 may spread up to a distance of 51m and 61 m respectively and may affect the

equipments in the unit and escalate. The 5 & 3 psi blast wave may spread up to a distance of 104

m & 112 m respectively from the source point and may affect the adjacent NHT/CCR units and

upcoming auxiliary facilities. However the blast waves may not be expected to be realized beyond

the complex boundaries.

Instrument Tapping Failure at Stabilizer Reflux Pump: From the consequence results and graphs

of the selected failure scenario, it was observed that LFL may be realized up to a distance of

42 m. The jet fire thermal radiation intensities of 37.5 and 12.5 kW/m2 may be experienced up to a

distance of 46 m and 54 m respectively affecting the equipments and structures within the units.

The 5 & 3 psi blast waves up to a distance of 51 m & 55 m respectively from the point of loss of

containment and may partially affect the equipments in NHT CCR which may result in escalation.


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6.5.4 OFFSITES

NHT Feed Tank on Fire: From the graph of this scenario, it is observed that the pool fire radiation

effect zone of 8KW/M2 may not be expected to affect the adjacent tanks for the prevailing

weather conditions.

Instrument tapping Failure at NHT feed pumps: From the Incident outcome analysis of this

scenario it is observed that the tanks YT-903 may be affected by 32KW/m2 & 8KW/m2 jet fire

radiation intensities. Also the tank YT-903 may be subjected to direct flame impingement which

may lead to hazardous secondary effects. The 5 & 3psi blast waves may affect the existing

control room on the south, the new tank farm, and the existing NHT/CCR feed tank farm if

realized.


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7 OBSERVATIONS & RECOMMENDATIONS

The detailed consequence analysis of release of hydrocarbon in case of major credible scenarios

are modeled in terms of release rate, dispersion, flammability and toxic characteristics, which

have been discussed in detail in the report. The Observations and recommendations arising out of

the Rapid Risk analysis study for units under upcoming MS block are summarized below:

NHT/CCR

Low frequency credible failure scenarios for NHT/CCR units are modeled and it is observed

that for large hole in Stripper bottom(NHT), De-Butanizer receiver(CCR), the radiation &

explosion effect zones may extend beyond the unit battery limits & may affect the nearby

units depending upon the prevalent weather condition and presence of ignition source at the

time of release. In case of Large hole in bottom of Reactor product separator (NHT) the LFL

hazardous zone may extend beyond the Complex boundary on the eastern side. The 5 & 3

psi may affect the adjacent VGO/HDS on the western side, SWS/ARU, SRU, Fuel oil tanks,

S/S-1, SRR-2, gate house on the northern side, new ISOM unit, existing NHT/CCR/ISOM,

upcoming SRR and upcoming substation on the southern side. The blast effects may also be

realized beyond the complex boundary well beyond the main road towards the eastern side

depending on the conditions of prevailing at the time of release. The potential outcomes of

large hole may have a significant impact onsite and offsite. However, Owing to the remote

possibility of realizing the large hole scenario (in the order of 1 x10-6 /M-year to 1 x10-7/M-

year) and its damaging effects. It is recommended to:

Include these scenarios to the already existing Disaster Management Plan (DMP) &

Emergency Response Plan (ERP).

Provide adequate number of hydrocarbon at suitable locations within these units for

early leak detection and inventory isolation.

In case of the Instrument tapping failure at Separator Pumps and Reformate product pump

instrument tapping failure of CCR, the jet radiation effect distances may affect the major part

of the unit and may lead to escalation. The blast overpressures of 5 and 3 psi may impact the

adjacent VGO/HDS, New ISOM, new substation and new SRR based on prevailing wind

conditions and direction of leak. However, the overpressure effects are observed to be largely

restricted within the complex boundaries. The toluene IDLH concentration of 500ppm may

have its effect up to a distance of 423 m and 345m in case of failures at separator pump and

reformate product pump respectively. Based on orientation of the leak and the more prevalent

weather conditions. The toxic affect may be experienced at chemical ware house, SRR-2,

gate house, fire station, QC lab, maintenance ware house, SRR-3, and Substation (S/S-1) on


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the northern and eastern side of the unit with a possibility of crossing the complex boundary

on the northern and southern side and extending beyond the main road on the eastern side.

In order to assess the risk to public due to loss of containment from the toluene containing

streams, risk analysis is carried out. For public, the Individual risk contour of 1 x 10-6/Avg yr

and lower (Negligible risk) is considered to demonstrate broadly acceptable region. From the

preliminary risk evaluation for credible failure cases within NHT/CCR & ISOM, it is seen that

the IR contour of 1 x 10-6 /Avg year (Refer fig 6.5.1.A) is within the complex boundary.

However a detailed Quantitative risk assessment (QRA) shall be carried out at detail

engineering stage for any further analysis.

Based on the above observations the following is recommended.

Provide adequate number of hydrocarbon at suitable locations within the unit and at the periphery

of the unit for early leak detection. Also mitigating procedures such emergency shutdown of

rotating equipments, quick isolation of inventories shall be developed as a part of the Emergency

response plan & Disaster Management Plan to address the concerns of high frequency failure

scenarios.

It is suggested to locate the CCR separator and related equipments, De-butanizer & reformate

pump towards the western side of the piperack to maintain as much distance as possible from

compound wall.

As the Quality Control lab may be affected by the toxic concentration of Toluene, suitable no. of

breathing apparatus may be provided to use in case of emergency based on detection or

emergency guidelines.

ISOM

Low frequency credible failure scenarios for ISOM units are modeled and it is observed that in

the event of large hole on bottom outlet of Separator Drum, radiation& explosion effect zones may

get extended beyond the units battery limits & affect nearby facilities including SRR-2, SRR-

3,Substation, gate house, SRR-3, and Substation (S/S-1), fuel oil tanks, low sulphur diesel tanks

and high sulphur diesel tanks on the northern side of the unit with a possibility of crossing the

complex boundary on the eastern side based on orientation of the leak and the most prevalent

weather conditions. As the possibility of realization of this scenario is extremely remote the

following is recommended.

The scenario may be utilized for Disaster management plant & Emergency Response Plan.


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High frequency credible failure scenarios for ISOM are also modeled. In the event of

instrument tapping failure of charge pumps, 20mm leak in the isomerate product-Stabilizer

outlet, it was observed that LFL may not extend beyond the complex boundary. The 5 & 3 psi

blast wave may affect the adjacent NHT/CCR units and upcoming facilities and may not

extend beyond the complex boundary. Based on the observations the following is

recommended.

Provide sufficient number of hydrocarbon detectors within the ISOM unit for early leak detection and

develop procedures for stopping of rotating equipments and quicker inventory isolation.

OFFSITES

Instrument tapping Failure at NHT feed pumps: From the Incident outcome analysis of this

scenario it is observed that the tanks YT-903 may be affected by 8KW/m2 and 32 KW/m2 jet

fire radiation intensities. Also the tank YT-903 may be subjected to direct flame impingement

and may lead to a domino effect in case of orientation of jet towards the tank. The 5 & 3psi

blast waves may affect the existing control room on the south, the new tank farm, and the

existing NHT/CCR feed tank farm based on the prevailing wind conditions and presence of

ignition sources at the time of leak.

The low operating frequency of the pump may be taken into consideration as a mitigating

factor for reduction in the probability of the realization of this scenario.

Based on the preceding observations the following is recommended:

As existing Tank YT-903 may be subjected to direct flame impingement the new pumps and

any leakage points such as flanges etc., be located atleast 40m away from the tank.

Review the suitability of active fire protection for this Tankage system for protection against

32KW/m2 radiation intensity.

The active fire protection system provided for storage tanks (YT-903/905) are to be regularly

checked for prompt action on actuation.

As the control room may not be exposed to LFL, but may be partially subjected to blast

overpressures, based on the prevailing site conditions and presence of ignition sources,

ensure suitable mitigation by early leak detection and automated inventory isolation.


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a) Recommendations for Construction Safety during execution of the MS Block

Project b) General Recommendations

Proper checking of contract people for smoking or inflammable materials to be ensured at

entry gates to avoid presence of any unidentified source of ignition.

Ensure vehicles entering the Refinery are fitted with spark arrestors, as a mandatory item.

In order to prevent secondary incident arising from any failure scenario, it is recommended

that sprinklers and other protective devices provided on the tanks are regularly checked to

ensure these are functional.

Mock drills to be organized at organization level to ensure preparation of the personnel’s

working in Refinery for handling any hazardous situation.

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.

Ensure usage of safer oxidizing agents (Chlorine free) in Cooling Water circuit.

c) Mitigating Measures

Mitigating measures are those measures in place to minimize the loss of containment event and,

hazards arising out of Loss of containment. These include:

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.

Water spray/curtain system may be utilized as means to restrict the hazardous cloud

movement in case of a leak.

d) Ignition Control

Ignition control will reduce the likelihood of fire events. This is the key for reducing the risk

within facilities processing flammable materials. As part of mitigation measure it strongly

recommended to consider minimization of the traffic movement within the Refinery.

e) Escape Routes

Ensure sufficient escape routes from the site are available to allow redundancy in escape

from all areas.

Ensure sufficient number of windsocks throughout the site to ensure visibility from all

locations. This will enable people to escape upwind or crosswind from flammable / toxic

releases.

Provide sign boards marking emergency/safe roads to be taken during any exigencies.

f) Preventive Maintenance for Critical Equipment’s

In order to reduce the failure frequency of critical equipment’s, the following are

recommended:


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a. High head pumps and Compressors, which are in flammable / toxic services, are

needed to be identified.

i. Their seals, instruments and accessories are to be monitored closely

ii. A detailed preventive maintenance plan to be prepared and followed.

b. Surge Drums & Reflux drums and high inventory vessels whose rupture may lead

to massive consequences are needed to be identified and following to be ensured:

i. Monitoring of vessel internals during shut down.

ii. A detailed preventive maintenance plan to be prepared and followed.

g) Others

Ensure removal of hammer blinds from the process facilities, if any.

Closed sampling system to be considered for pressurized services like LPG, Propylene

etc.

Recommended to use portable HC detector during sampling and maintenance etc.

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.

STEL “Short Term Exposure Limit” is the maximum permissible average

exposure for the time period specified (15 minutes).


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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

1. Classification of hazardous locations, A. W. Cox, F. P. Lees and M. L. Ang, Published by

the Institute of Chemical engineers, U. K.

2. The reference manual, Volume-II, Creemer & Warner Ltd. U. K. (Presently Entec).

3. 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.

4. Loss prevention in the process industries, Hazard identification, Assessment and Control,

Frank. P. Lees (Vol. I, II & III), (2nd edition ) ,Published by Butterworth-Heinemann, U. K.

5. AICHE, CCPS, Chemical process Quantitative Risk Analysis(2nd edition)

6. Guideline for Quantitative Risk assessment, ‘Purple book’.( 2005)


Doc No: A870-17-43-RRA-0001 Rev. No.: 0


ANNEXURE I

CONSEQUENCE ANALYSIS HAZARD DISTANCES

Temp.

(OC)

Press.

(Kg/cm2g)4 KW/m2 12.5 KW/m2 37.5 KW/m2 4 KW/m2 12.5 KW/m2 37.5 KW/m2 2 psi 3 psi 5 psi

1F 86 92 73 61 - - - 119 110 102

1.5C/D 81 89 70 58 - - - 113 105 99

2.5D 84 86 65 53 - - - 112 105 98

1F 212 139 95 66 - - - 316 292 270

1.5C/D 208 135 100 76 - - - 286 267 249

2.5D 248 126 101 91 - - - 328 308 290

1F 26 22 16 NR - - - 33 30 27

1.5C/D 24 22 16 NR - - - 32 29 27

2.5D 21 22 17 6 - - - 32 29 27

1F 91 133 105 89 - - - 129 120 112

1.5C/D 88 128 100 84 - - - 116 108 100

2.5D 89 122 94 77 - - - 116 108 100

1F 121 67 53 45 - - - 181 167 154

1.5C/D 91 65 51 42 - - - 124 117 109

2.5D 77 62 48 39 - - - 101 94 88

1F 80 92 73 61 61 45 38 107 99 91Toluene -491

Ethyl benzene -236

1.5C/D 78 89 70 58 - - - 102 95 88Toluene-424

Ethyl benzene-188

2.5D 82 85 65 54 - - - 112 105 98Toluene- 292

Ethyle Benzene-166

1F 21 16 12 NR - - - 31 28 26

1.5C/D 19 17 12 NR - - - 18 16 14

2.5D 16 17 13 NR - - - 18 16 14

1F 64 76 61 51 56 36 NR 90 84 77Toluene- 297

Ethyl benzene-176

1.5C/D 68 74 58 48 58 40 32 88 81 76Toluene- 264

Ethyl benzene-155

2.5D 73 71 55 45 61 43 33 98 91 86Toluene- 199

Ethyl benzene-120

1F 116 139 111 94 - - - 160 149 138

1.5D 113 134 106 89 - - - 155 145 136

2.5D 118 128 99 82 - - - 155 145 135

1F 47 70 56 48 - - - 61 56 52

1.5C/D 45 68 54 46 - - - 59 55 51

2.5D 44 64 50 42 - - - 59 55 51

18

5.42

Toluene (500ppm), Ethyl

benzene (800ppm)

8.39

Debutanizer Receiver Large Hole on bottom outlet

50

9 37.17

29 13.61

24 0.37

10.4 7.98

Toluene (500ppm), Ethyl

benzene (800ppm)

Reactor Product Separator Large Hole on bottom outlet-toxic 52

Recycle Compressor Instrument Tapping Failure 81 41

21

46.73

0.64

14.57

62.39

105

10 Debutanizer Overhead Pumps

9 41

Instrument Tapping Failure 40

7

8 Reformate Product Pump 20mm leak - Toxic 83

Net Gas Compressor 2nd Stage Instrument Tapping Failure

3

42

6

1 Feed Charge Pump Instrument Tapping Failure 40

2

4 Stripper Bottom Large Hole-toxic 170 18

Separator Pumps Instrument Tapping Failure - Toxic

5 Splitter Reflux Pump Instrument Tapping Failure-toxic 40 6

Unit Sl No. Equipment Failure Case NOTEWeather

Jet Fire (m) Pool Fire (m) Blast Over Pressure (m)Leak Rate

Kg/sFlash Fire

(m)IDLH Conc Distance

(m)

Operating Conditions

CCR

NHT

BPCL Kochi- Consequence Analysis Hazard Distances

Temp.

(OC)

Press.

(Kg/cm2g)4 KW/m2 12.5 KW/m2 37.5 KW/m2 4 KW/m2 12.5 KW/m2 37.5 KW/m2 2 psi 3 psi 5 psi

Unit Sl No. Equipment Failure Case NOTEWeather

Jet Fire (m) Pool Fire (m) Blast Over Pressure (m)Leak Rate

Kg/sFlash Fire

(m)IDLH Conc Distance

(m)


BPCL Kochi- Consequence Analysis Hazard Distances

1F 87 91 72 61 - - - 119 110 102

1.5C/D 82 88 69 58 - - - 113 106 99

2.5D 86 85 65 53 - - - 112 105 98

1F 197 179 141 118 56 37 NR 287 265 245

1.5C/D 194 174 135 112 60 39 NR 270 252 235

2.5D 230 168 127 103 65 41 NR 311 293 276

1F 25 20 15 NR - - - 31 28 26

1.5C/D 22 20 15 NR - - - 30 28 26

2.5D 21 20 15 NR - - - 30 27 25

1F 87 77 61 51 - - - 122 113 104

1.5C/D 76 75 58 49 - - - 101 94 88

2.5D 83 72 55 45 - - - 111 104 98

1F 43 67 54 46 - - - 59 55 51

1.5C/D 41 64 51 44 - - - 58 54 50

2.5D 40 61 48 40 - - - 58 54 50

Temp.

(OC)

Press.

(Kg/cm2g)4 KW/m2 8 KW/m2 32 KW/m2 4 KW/m2 8 KW/m2 32 KW/m2 2 psi 3 psi 5 psi

1F 123 69 54 45 - - - 179 166 154

1.5C/D 87 67 52 43 - - - 113 106 99

2.5D 78 64 49 40 - - - 100 94 88

1F - - - - 54 30 NR - - -

1.5C/D - - - - 59 32 NR - - -

2.5D - - - - 67 36 NR - - -

ISOM

12 Separator Drum Large Hole on bottom outlet

13

40

Stabilizer Rflux Pump 60

Instrument Tapping Failure-toxic

H2 Make-up Compressor

13.63

Instrument Tapping Failure

1815

109 36.9

8.2414.5

8.22

0.77

19.1 57.21

7

Failure Case

5.9516 NHT FEED PUMP Instrument Tapping Failure

Leak RateKg/s

NOTE

40

17 NHT feed tank Tank on Fire 30 0.007 -

OFFSITE

Unit


WeatherFlash Fire

(m)

Jet Fire (m) Pool Fire (m) Blast Over Pressure (m)IDLH Conc Distance

(m)

Isomerate product separator outlet line

Instrument Tapping Failure

20mm leak 40

EquipmentSl No.

14

11 Charge Pumps 40 38


Doc No: A870-17-43-RRA-0001 Rev. No.: 0


ANNEXURE II

FIGURES FOR CONSEQUENCE ANALYSIS OF MS BLOCK

Figure 6.5.1.1 A: NHT: Instrument Tapping Failure at Feed Charge Pump; Flash fire Distances (m)

Figure 6.5.1.1 B: NHT: Instrument Tapping Failure at Feed Charge Pump; Jet fire Distances (m)

Figure 6.5.1.1 C: NHT: Instrument Tapping Failure at Feed Charge Pump; Overpressure Distances (m)

Figure 6.5.1.2 A: NHT: Large hole of Reactor Product Separator ; Flash Fire Distances (m)

Figure 6.5.1.2 B: NHT: Large hole of Reactor Product Separator ; Jet Fire Distances (m)

Figure 6.5.1.2 C: NHT: Large hole of Reactor Product Separator; Over Pressure Distances (m)

Figure 6.5.1.3 A: NHT: Instrument Tapping Failure at Recycle Compressor; Flash Fire Distances (m)

Figure 6.5.1.3 B: NHT: Instrument Tapping Failure at Recycle Compressor; Jet Fire Distances (m)

Figure 6.5.1.3 C: NHT: Instrument Tapping Failure at Recycle Compressor; Over Pressure Distances (m)

Figure 6.5.1.4 A: NHT: Large Hole on bottom outlet of Stripper Bottom; Flash Fire Distances (m)

Figure 6.5.1.4 B: NHT: Large Hole on bottom outlet of Stripper Bottom ; Jet Fire Distances (m)

Figure 6.5.1.4 C: NHT: Large Hole on bottom outlet of Stripper Bottom ; Over Pressure Distances (m)

Figure 6.5.1.5 A: NHT: Instrument Tapping Failure of Splitter Reflux Pump; Flash Fire Distances (m)

Figure 6.5.1.5 B: NHT: Instrument Tapping Failure of Splitter Reflux Pump; Jet Fire Distances (m)

Figure 6.5.1.5 C: NHT: Instrument Tapping Failure of Splitter Reflux Pump; Over Pressure Distances (m)

Figure 6.5.2.1 A: CCR: Instrument Tapping Failure at Separator Pumps - Toxic; Flash Fire Distances (m)

Figure 6.5.2.1 B: CCR: Instrument Tapping Failure at Separator Pumps - Toxic; Jet Fire Distances (m)

Figure 6.5.2.1 C: CCR: Instrument Tapping Failure at Separator Pumps - Toxic; Late Pool Fire Distances (m)

Figure 6.5.2.1 D: CCR: Instrument Tapping Failure at Separator Pumps - Toxic; Over Pressure Distances (m)

Figure 6.5.2.1 D: CCR: Instrument Tapping Failure at Separator Pumps - Toxic; Toluene IDLH Distances (m)-500ppm

Figure 6.5.2.2 A: CCR: Instrument Tapping Failure at Recycle Gas Compressor ; Flash Fire Distances (m)

Figure 6.5.2.2 B: CCR: Instrument Tapping Failure at Recycle Gas Compressor - Toxic; Jet Fire Distances (m)

Figure 6.5.2.2 C: CCR: Instrument Tapping Failure at Recycle Gas Compressor - Toxic; Overpressure Distances (m)

Figure 6.5.2.3 A: CCR : Instrument Tapping Failure in reformate product Pump ; Flash Fire Distances (m)

Figure 6.5.2.3 B: CCR: Instrument Tapping Failure in reformate product Pump - Toxic; Jet Fire Distances (m)

Figure 6.5.2.3 C: CCR: Instrument Tapping Failure in reformate product Pump; Pool fire Distances (m)

Figure 6.5.2.3 D: CCR: Instrument Tapping Failure in reformate product Pump; Overpressure Distances (m)

Figure 6.5.2.3 E: CCR: 20mm Leak in reformate product Pump - Toxic; Toluene IDLH Hazard Distances (m)-500ppm

Figure 6.5.2.4 A: CCR: Large Hole on the Bottom Outlet of De-butanizer Receiver; Flash Fire Distances (m)

Figure 6.5.2.4 B: CCR: Large Hole on the Bottom Outlet of De-butanizer Receiver; Jet Fire Distances (m)

Figure 6.5.2.4 C: CCR: Large Hole on the Bottom Outlet of De-butanizer Receiver; Over Pressure Distances (m)

Figure 6.5.2.5 A: CCR: Instrument Tapping Failure at De-butanizer Overhead pumps; Flash Fire Distances (m)

Figure 6.5.2.5 B: CCR: Instrument Tapping Failure at De-butanizer Overhead pumps; Jet Fire Distances (m)

Figure 6.5.2.5 C: CCR: Instrument Tapping Failure at De-butanizer Overhead pumps; Overpressure Fire Distances (m)

Figure 6.5.3.1 A: ISOM: Instrument Tapping Failure at Charge Pump; Flash fire Distances (m)

Figure 6.5.3.1 B: ISOM: Instrument Tapping Failure at Charge Pump; Jet fire Distances (m)

Figure 6.5.3.1 C: ISOM: Instrument Tapping Failure at Charge Pump; Overpressure Distances (m)

Figure 6.5.3.2 A: ISOM: Large Hole on bottom outlet of Separator Bottom; Flash Fire Distances (m)

Figure 6.5.3.2 B: ISOM: Large Hole on bottom outlet of Separator Bottom; Jet Fire Distances (m)

Figure 6.5.3.2 C: ISOM: Large Hole on bottom outlet of Separator Bottom; Pool Fire Distances (m)

Figure 6.5.3.2 D: ISOM: Large Hole on bottom outlet of Separator Bottom; Overpressure Distances (m)

Figure 6.5.3.3 A: ISOM: Instrument Tapping Failure at Hydrogen make-up gas compressor; Flash Fire Distances (m)

Figure 6.5.3.3 B: ISOM: Instrument Tapping Failure at Hydrogen make-up gas compressor; Jet Fire Distances (m)

Figure 6.5.3.3 C: ISOM: Instrument Tapping Failure at Hydrogen make-up gas compressor; Overpressure Distances (m)

Figure 6.5.3.4 A: ISOM: 20mm leakage at Isomerate Product line; Flash Fire Distances (m)

Figure 6.5.3.4 B: ISOM: 20mm leakage at Isomerate Product line; Jet Fire Distances (m)

Figure 6.5.3.4 C: ISOM: 20mm leakage at Isomerate Product line; Overpressure Distances (m)

Figure 6.5.3.5 A: ISOM: Instrument Tapping Failure at Stabilizer reflux pump; Flash Fire Distances (m)

Figure 6.5.3.5 B: ISOM: Instrument Tapping Failure at Stabilizer reflux pump; Jet Fire Distances (m)

Figure 6.5.3.5 C: ISOM: Instrument Tapping Failure at Stabilizer reflux pump; Overpressure Distances (m)


Doc No: A870-17-43-RRA-0001 Rev. No.: 0


ANNEXURE III

INDIVIDUAL RISK CONTOUR

Figure 6.5.5.1 A: BS-VI: Individual Risk Contours

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