Quantitative Risk Assessment of BS-VI Projectenvironmentclearance.nic.in/writereaddata/online/Risk...BS-VI Project at IOCL Guwahati Refinery Quantitative Risk Assessment Report Number

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INTERNATIONAL RISK CONTROL ASIA LLP

[An ISO 9001:2015 Certified Company]

Quantitative Risk Assessment of

BS-VI Project For

Indian Oil Corporation Limited

Guwahati Refinery

Client’s Name: Indian Oil Corporation Limited (IOCL)

Project Title: QRA for BS-VI Project at IOCL Guwahati Refinery

IRCA Document Number: IRCA-IOCL-QRA-20171808-01

1 29-08-2018 Revised, incorporating

Client comments Sufiyan Ansari R. Krishnan Rajneesh Kumar

0 16-07-2018 Issued for Review /

Comments Sufiyan Ansari R. Krishnan Rajneesh Kumar

Revision Issue Date Reason for Issue Prepared by Reviewed by Approved by IRCA

BS-VI Project at IOCL Guwahati Refinery Quantitative Risk Assessment

Report Number IRCA-IOCL-QRA-20171808-01 Rev 1 Aug 2018

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Contents

1. INTRODUCTION ............................................................................................................................1.1

2. STUDY OBJECTIVE .......................................................................................................................2.1

3. PROCESS DESCRIPTION ..............................................................................................................3.1

4. STUDY METHODOLOGY .............................................................................................................4.1

5. STUDY INPUTS ..............................................................................................................................5.1

6. RISK ANALYSIS RESULTS ..........................................................................................................6.1

7. CONSEQUENCE ANALYSIS ........................................................................................................7.1

8. CONCLUSIONS & RECOMMENDATIONS .................................................................................8.1

Attachment I : QRA Assumption Sheets

Attachment II : Failure Cases Input to QRA

Attachment III : Consequence Analysis Graph



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Executive Summary

Indian Oil Corporation Limited is considering production of 100% BS-VI compliant MS and HSD from Guwahati Refinery to meet guidelines established in Auto Fuel Policy 2025. As a part of this objective, revamp of Hydrotreater Unit (HDT), ISOM Unit, Hydorgen Unit (HGU) and IndaDeptG units have been considered. IndeSelctG Unit and MS Auto Blender Units have been considered as new facilities.

IOCL being an organization with high standards of safety, health and environment management, wishes to ensure the process risks associated with the installation / modification of existing equipments are properly assessed to ensure that risk levels are kept as low as reasonably practicable. IOCL has therefore engaged M/s International Risk Control Asia (IRCA), Mumbai, to carry out a Quantitative Risk Analysis (QRA) for BS-VI Project at Guwahati Refinery.

Individual Risk

The overall iso–risk contours representing location-specific individual risk (LSIR) for BS-VI Project at Guwahati Refinery are shown in Figure 1.

Figure 1: Overall iso-risk contours

The highest location-specific individual risk contour in unit is of 10-4 per year.



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The maximum LSIR in the units are listed in Table 1.

Table 1: Maximum Location-Specific Individual Risk (LSIR)

SR. NO.

AREA / UNIT MAXIMUM LSIR

(PER YEAR)

1. IndeselectG unit area 6.00E-04

2. HGU unit area 5.00E-04

3. HDT unit area 4.40E-04

4. ISOM unit area 4.20E-04

5. MS Auto Blending Unit area 1.50E-04

Individual risk to worker

The Location-specific individual risk (LSIR) is risk to a person who is standing at that point 365 days a year and 24 hours a day. The personnel in BS-VI units are expected to work in 8 hour shift as well general shift. The actual risk to a person i.e. “Individual Specific Individual Risk” (ISIR) would be far less after accounting for the time fraction a person is expected to spend at a location.

ISIR Area = LSIR x (8/24)(8 hours shift) x (Time spend by an individual / 8 hours)

The maximum ISIR in the units are listed in Table 2.

Table 2: Maximum Individual-Specific Individual Risk (ISIR)

SR. NO.

AREA / UNIT MAXIMUM ISIR

(PER YEAR)





5. MS auto blender unit 1.25E-05



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From the results shown above, the maximum individual risk to worker is estimated as 5.00 x 10-5 per year. ALARP Summary & Comparison of Individual risk with Acceptability Criteria

The objective of this QRA study is to assess the risk levels with reference to the defined risk acceptability criteria and recommend measures to reduce the risk level to as low as reasonably practicable (ALARP). The comparison of maximum individual risk with the risk acceptability criteria is shown in Figure 2. The individual risk of 5.0 x 10-5 per year for worker is in the ALARP Level.

Figure 2: Individual Risk

Max. Individual Risk to Plant Personnel: 5.00 E-05 per year

(Negligible Risk) Max. Individual Risk to Public:

< 1.0 E-06 per year



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Societal Risk The Societal Risk parameter for BS-VI Project is shown in Figures 3 in the form of an FN curve. The results of FN curves show that the risk is in “ALARP” region.

Figure 3: FN Curve for Group Risk at BS-VI project units



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Top Risk Contributors (Group Risk)

The significant risk contributions from different units based on results available from DNV PHAST RISK software (PHAST RISK (also known as SAFETI) is a software of DNV-GL which is used for Quantitative Risk Assessment studies) are shown in Table 3.

Table 3: Top Risk Contributors

Sr. No. Section Name Section Tag No. Risk

Contribution (%)

1 HDT Unit

1.1 Stripper Feed-Bottom Exchanger, Reactor Effluent-Stripper Feed Exchanger, Stripper

49-E-07, 49-E-08, 49-C-02

9.06

1.2 Backwash Surge Drum, Backwash Pump

49-V-21, 49-P-15A/B 3.30

1.3 Feed Filter, Feed Preheat Exchanger, Feed Surge Drum

49-G-01, 49-E-01, 49-V-02

2.08

1.4 Diesel / Kerosene Transfer Pump 49-P-01A/B 1.76

1.5 Feed Coalescer 49-V-01 1.67

1.6 Stripper overhead Pump 49-P-06A/B 1.67

2 HGU Unit

2.1 Naptha Feed Pump 48-P-01A/B 3.91

2.2 Low Temperature Shift Reactor, BFW Preheater-I, Demin Water Preheater

48-R-05, 48-E-06, 48-E-08

2.30

2.3 Cold Condensate Separator 48-V-08 2.29

2.4 Naptha Booster Pump 48-P-04A/B 2.16

2.5 Naptha Fuel Booster Pump 48-P-05A/B 2.11

3 IndeselectG unit

3.1 Feed Filter, Feed Coalescer 04-G-801A/B, 04-V-801

6.55

3.2 H2 Stripper, Stripper Feed Bottom Exchanger, Splitter Feed Cooler

04-C-801, 04-E-808, 04-E-807A/B

4.07

3.3 Feed/Reactor Effluent Exchanger, 04-E-809A/B, 04-E- 2.54



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Contribution (%)

Reactor Feed Preheater, Electric Heater KOD, Electric Heater

802, 04-V-808, 04-EH-801

3.4 SDS Reactor 04-R-801 1.86

3.5 Feed Pump 04-P-801A/B 1.52

4 ISOM Unit

4.1 Deisopentaniser Reflux Drum 56-V-125 12.04

4.2 Deisopentaniser Column including reboiler-liquid side plus Deisopentaniser feed preheater

56-C-114, 56-E-129, 56-E-128

9.04

4.3 Deisopentaniser Bottom Pump including Deisopentaniser feed preheater

56-P-120A/B, 56-E-128

7.26

4.4 Deisopentaniser Overhead Pump including Deisopentaniser isomerate cooler

56-P-121A/B, 56-E-131

5.13



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CONCLUSIONS & RECOMMENDATIONS

The maximum risk to persons working in the BS-VI units area is 5.00 x 10-5 per year which is in ALARP level (refer Yellow band in risk acceptability criteria). The risk to Public is in due to the proposed BS-VI project is in “Broadly Acceptable level”. Societal risk is also in “ALARP Level”. The following recommendations are made to keep the risk level in broadly acceptable level.

Recommendations 1. It is necessary to provide extensive fire and gas detection system in the Units. Philosophy for

operation of fire and gas detection system to isolate the relevant sections should be clearly defined and the operating personnel should be trained for proper use of this safety system. Fire & Gas detection system normally covers (a) areas containing potential leak sources such as large number of flange joints, valves, pumps, etc. and (b) pressure vessels containing significant inventory of light hydrocarbons which are vulnerable to BLEVE/ fireball hazards.

2. It is recommended to have necessary provision for emergency stop of all major transfer pumps

from control room in the event of major leak / flash fire there should be an SOP established for clarity of actions to be taken in case of fire / leak emergency. The details of Pumps are as follows:

Charge Pump (49-P-03A/B), Stripper Bottom Pumps (49-P-05A/B) in DHT Unit, Naptha Booster Pump (48-P-04A/B), Naptha Feed Pump (48-P-01A/B) in HGU unit, Feed Pump (04-P-801A/B) in IndeselectG Unit and Deisopentaniser Bottom Pump (56-P-120A/B) in ISOM unit.

3. The emergency response plan of the refinery to be updated to cover the BS-VI units.



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1. INTRODUCTION

Guwahati Refinery is the country’s first refinery of Indian Oil Corporation Limited (IOCL) serving the nation since 1962. Built with Rumanian assistance, the Refinery with initial capacity of 0.75 MMTPA was designed to process Ingenuous Assam crude. The refining capacity was subsequently enhanced to 1.0 MMTPA. With INDMAX, the ISOSIV and Hydrotreater the Refinery was able to produce eco-friendly fuels.

Quality LPG, Motor Spirit, Aviation Turbine Fuel, Superior Kerosene Oil, High Speed Diesel and Raw Petroleum Coke are the products of this Refinery. With ISOM Project commissioned in 2010, the MS produces here complies to BS-III specifications and so does the HSD, thus meeting the Auto Fuel Policy of the Government of India.

Indian Oil Corporation Limited is considering production of 100% BS-VI compliant MS and HSD from Guwahati Refinery to meet guidelines established in Auto Fuel Policy 2025. As a part of this objective, revamp of Hydrotreater Unit (HDT), ISOM Unit, Hydorgen Unit (HGU) and IndaDeptG units have been considered. IndeSelctG Unit and MS Auto Blender Units have been considered as new facilities.

IOCL being an organization with high standards of safety, health and environment management, wishes to ensure the process risks associated with the installation / modification of existing equipments are properly assessed to ensure that risk levels are kept as low as reasonably practicable. IOCL has therefore engaged M/s International Risk Control Asia (IRCA), Mumbai, to carry out a Quantitative Risk Analysis (QRA) for BS-VI Project at Guwahati Refinery.

IRCA has carried out hazard and risk analysis studies for a large number of oil & gas installations and chemical plants over the past eight years including 15 MMTPA Paradip Refinery Project of IOCL.

This document presents IRCA's report on QRA study of BS-VI Project at Guwahati Refinery.



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2. STUDY OBJECTIVE

This study aims for quantitative assessment of process risks due to BS-VI project at IOCL Guwahati Refinery. The risk covered in this study is mainly risk to people due to release of material by loss of containment resulting in fire, explosion or toxic dispersion. The risk to life is calculated as “Individual Risk” and “Group Risk”. Individual Risk: It is represented by iso-risk contours, which show the geographical distribution of risk to an individual. It is assumed that the individual is continuously present at that location, out of doors and does not shelter or try to escape. Group Risk: it is represented by FN curves, which show the cumulative frequency distribution of accidents causing different numbers of fatalities. The FN curve therefore indicates whether the Group risk to the facility is dominated by relatively frequent accidents causing small numbers of fatalities or low frequency accidents causing many fatalities. The main objectives of this study are:

To establish the risk levels, compare them with appropriate risk acceptability criteria to determine the suitability of the development, and suggest necessary risk reduction measures so that the risk is as low as reasonably practicable.

To estimate the extent of potential damage due to fire, explosion or toxic release resulting from credible leak scenarios so as to ensure that the necessary measures for damage reduction are incorporated in the system design.

To provide necessary inputs for preparing on-site and off-site emergency plans The scope of this QRA study is to cover all the new / existing equipments coming under BS-VI projects. as shown in plot plan for DE-02002-00-16-101 Rev-06 for HDT unit & HGU unit, 44AC2700-04/L.01/0001/A1 Rev-0 for IndeselectG unit and 44AC2700-56-L.01-0001-A1 Rev-A for ISOM unit.



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3. PROCESS DESCRIPTION

3.1 HDT Unit (Revamp)

Indian Oil Corporation Limited (IOCL) has an existing HDT Unit at Guwahati Refinery in Guwahati, Assam, India. The HDT Unit was designed to process 600 KTPA of blended feed containing Straight run Kerosene II, Straight run Gasoil, Coker Kerosene and Coker Gasoil during Diesel operation and blend of Straight run Kerosene I & II streams during Kerosene operation in blocked mode. The design objective was to reduce the diesel product sulfur content to 500 wt.-ppm (max) when operating in “Diesel Mode” along with achieving ATF and Kerosene product properties when operating in “ATF/PCK Mode of operation”. Indian Oil Corporation Limited (IOCL) is considering production of 100% BS-VI compliant low sulfur diesel from Guwahati Refinery. IOCL is considering capacity revamp of existing Hydrotreater Unit (DHT Unit) from a capacity of 600 KTPA to 800 KTPA to produce diesel with less than 8 wt.-ppm sulfur conforming to the BS-VI specifications. The unit shall be capable of hydrotreating feed blend of SR Heavy Naphtha, SR Kerosene-I, SR Kerosene-II & SRGO streams from CDU, Heavy Coker Naphtha, Coker Kerosene & Coker Gas Oil streams from DCU, and TCO from Indmax FCC unit for production of BS-VI Diesel. The objectives of the current revamp are as under:

Operate the DHT Unit at 133% of original design capacity (i.e. 0.8 MMTPA). Achieve Diesel Product sulfur specification of 8 wt. ppm. Produce BS-VI Aviation Turbine Fuel (ATF) and Pipeline Compatible Kerosene (PCK) from SR

Kerosene-I feed in blocked out mode of operation. Achieve a cycle length of 36 months

3.2 HGU Revamp

The Hydrogen plant is revamped for Indian Oil Corporation Ltd. (IOCL) refinery at Guwahati, India. The hydrogen generation unit is based on steam reforming technology of TechnipFMC using either Assam Crude Naphtha or Import Crude Naphtha as primary feed. For achieving the required feed flexibility, a pre-reforming step is applied upstream the reforming using Kvaerner’s technology. For the purification of raw hydrogen after the shift conversion, Pressure Swing Adsorption (PSA) process is applied to produce the high purity hydrogen product. The unit behavior and its performance has been also simulated for the foreseeable operational as well as upset modes.

3.3 IndeSelectG Unit

The indeSelectG Unit shall process gasoline from INDMAX unit as well as the distillate of the new DCU CG splitter. The objective of the unit is basically to saturate the dioefins present in the feed gasoline as well as the shifting of lower molecular weight sulphur to higher molecular weight sulphur compounds so that the sulphur content in the top cut from the three cut splitter of the indeSelectG unit is reduced so that it can be sent directly to the MS pool meeting BS-VI sulphur specifications.



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3.4 ISOM Revamp (De-Isopentanizer section, DIP)

The main objective of Deisopentaniser (DIP) project is to increase the capacity of ISOM unit by 20% by recovering isopentane component from ISOM feed. Deisopentaniser column primarily separates out the isopentane component, already present in the feed. The top product from the DIP, being a high RON stream, is directly blended with product coming from De-Isohexaniser column of ISOM unit and the combined stream viz. Isomerate is sent to the MS pool. The bottom product is routed to the existing ISOM reactors for isomerization. Naphtha Hydrotreater (NHT) section of ISOM unit is designed for treating ISOM feed i.e., Light Naphtha Stream and Heart cut stream from 3-cut splitter for removal of impurities (e.g. sulfur, nitrogen, oxygen, metals etc.) from ISOM feed. NHT reactor effluent is routed to the stripper via HDT separator drum. The purpose of stripper is to remove H2S, H2 and light hydrocarbons from the product stream. Presently, Stripper bottom is directly routed to ISOM Feed Surge Drum through Sulfur guard bed. DIP feed System In order to process Stripper bottom hydrotreated naphtha in the new Deisopentaniser column, a new 3” tapping downstream of the tube side outlet of stripper feed bottom exchanger is taken. A new control valve is provided in DIP feed line to control column feed flow in cascade with stripper bottom level. A new selector switch is provided to toggle between existing control valve and new DIP feed control valve. The feed under flow control goes to the double pipe feed preheat exchanger (Feed vs column bottom) and is fed to the Deisopentaniser column for splitting. Deisopentaniser Column Refer to the Process flow diagram document number for the main process scheme, process control, operating conditions etc. The preheated feed enters the DIP column. DIP column consists of 81 trays with feed tray being # 39 from top. This column is equipped with a vertical thermosyphon reboiler at the bottom, heated by De-superheated steam. This reboiler controls 79th tray temperature by controlling the steam flow to the reboiler through steam control valve. The bottom product is drawn from DIP Column bottom under level control. Column bottom pump discharge is routed to feed preheater and then further cooled in the trim cooler before routing it to the ISOM feed surge drum. Column overhead vapor is condensed through air cooler to around 55°C and is routed to the reflux drum. A part of it after pumping through reflux cum product pump is returned back as reflux to the column under flow control, set by reflux drum level. Isopentane rich stream is drawn by the same pump from the reflux drum and is routed to MS pool via water cooler. DIP Top product flow is controlled by flow control valve, which is cascaded with either n-Pentane analyser or 6th tray temperature of column. A selector switch is provided to toggle between analyser control and temperature control. DIP column top pressure is controlled by pressure control valve, located at the inlet of air cooler. A hot vapor bypass with differential pressure control valve is also provided to maintain the pressure of reflux drum. Flare control valve is also provided on the reflux drum for removal of non-condensable, if any.



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The column and reflux drum are provided with pressure safety valves. The discharges from all the pressure safety valves are routed to the existing flare header of ISOM unit. Two nos. PSVs (one in line, one stand-by) with bypass line are provided at DIP column whereas single PSV with bypass line has been provided for the reflux drum. Operation philosophy The Deisopentaniser unit is designed to operate at 6.75 TPH with 50% turn down ratio. The column is also designed for a separate check case with lighter feed composition. Feed / bottom heat exchanger is provided for feed preheating & heat recovery from the bottom stream. DIP column feed is controlled by flow control valve cascaded with existing stripper bottom level controller. In case of DIP section outage due to any eventuality, stripper level can still be controlled by existing flow control valve. A soft selector switch is provided for this purpose. DIP column top pressure is controlled by pressure control valve, located at column overhead line. A hot vapour bypass differential pressure control valve is also provided for maintaining reflux drum pressure. Flare control valve on reflux drum is given for removal of non-condensable during any upset condition. Isopentane in the feed stream is separated & collected at column top and is routed directly to the existing MS pool. Online analyser is provided at overhead line to monitor slippage of n-pentane in the overhead stream & accordingly product draw is maintained by flow control valve. Overhead product can also be drawn based on 6th tray temperature of DIP. A soft selector switch is provided for selection of the best control system. Isopentane in column bottom stream is minimized by maintaining 79th tray temperature. Accordingly temperature controller controls amount of steam flow to the reboiler by flow control valve. Column bottom stream is routed to the existing ISOM feed surge drum via flow control valve cascaded with column level controller.



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3.5 Indadept G revamp

The INDAdeptG unit comprises of two main sections: Adsorption Section Regeneration Section

A brief process description of both these sections is given below. Operation of the Adsorption and Regeneration sections is controlled by a number of solenoid valves which are operated with the help of a PLC based control system. The PLC based system will operate (open /close) the solenoid valves at a preset time and condition. 3.5.1 ADSOPRPTION SECTION

This section can be further divided into three main sections: FEED PREPARATION AND HEATING SECTION Heavy Cut Gasoline from three cut splitter of ISOM unit is received at 160oC and 9.0 kg/cm2 pressure at the BL of INDAdeptG unit. Feed is also received from the storage tanks in offsite area. Feed received from the offsite tankage shall be available at 9.0 kg/cm2 and 40oC. The mixed feed from both the sources will pass through a filter (57-G-01A/B) to remove solid particles, passed through coalescer (57-V-01) before being stored in the feed surge drum (57-V-02) of INDAdeptG unit. Feed is received through flow controller (FV-1102) from the ISOM unit and on level controller (LV-1101A/B) from the feed surge drum (57-V-02). Feed naphtha is pressurized with the help of naphtha feed pump (57-P-01A/B) to 23.0 kg/cm2 and fed to reactor feed / effluent exchangers (57-E-01A/F) mixed with recycle hydrogen from recycle gas compressor (57-K-01A/B). The mixture of naphtha and hydrogen is heated to 263oC by the hot reactor effluent exiting reactor (57-R-02A/B) at 315oC. The total naphtha gets converted into vapor at the outlet of the exchanger. The naphtha vapor and hydrogen mixture is further heated to 300oC in an electric feed heater (57-EH-01) and fed to metal guard (57- R-01) to trap the metals coming in with the feed naphtha. The feed from the metal guard is fed at the top of one of the two reactors (57-R-02A/B) i.e. the reactor which is operating under adsorption mode. During this period the other reactor will be operating in regeneration mode. REACTOR SECTION The reactor section consists of two reactors in parallel. At any time one of the reactor will be operating in adsorption mode and other in regeneration mode. After a time interval of 120 hrs there is switch in the mode of operation of reactors. The feed consisting of a mixture of vaporized naphtha and recycle hydrogen at 300oC and 20.0 kg/cm2 is fed at the top of the reactor operating in adsorption mode and flows down the catalyst bed. When the reactor 57-R-02A is operating in adsorption mode the solenoid valves UV-1304, 1305 at the inlet to the reactor, quench solenoid valve UV-1408 and reactor outlet solenoid valve UV-1401 & 1402 will be in open position. All other solenoid valves connected to this reactor, both at the inlet and outlet shall be in closed position. Since during this period reactor 57-R-02B will be in regeneration mode the solenoid valves UV-1307 & 1308, on naphtha feed line, at the inlet to the reactor, quench solenoid valve UV-1508 and reactor outlet solenoid valve UV-1501 & 1502 will be in closed position.



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Each reactor consists of two adsorbent beds. Reactor temperature is controlled at 300oC at the inlet to 2nd adsorbent bed with the help of recycle hydrogen quench. Quench gas flow is controlled with the help of TIC – 1405 for the reactor 57-R-02A and with TIC-1505 for the reactor 57-R-02B. The reactor catalyst beds temperature is monitored with the help of a number of thermocouples. A number of alarms for high temperature of the catalyst bed, during different modes of operation i.e. Adsorption, Coke/Sulfur combustion and Catalyst Activation, are also provided. The pressure drop in the reactor as indicated by PDI 1401 / 1404 for the reactor 57-R-01A and PDI 1501 / 1504 for the reactor 57-R-01B respectively. PRODUCT AND HEAT RECOVERY SECTION The reactor effluent, in vapor form, is cooled to about 173oC in reactor feed / effluent exchanger (57-E-01A/F) by exchanging heat with the feed naphtha and recycle hydrogen mixture. Wash water is mixed with the cooled reactor effluent from 57-E-01A/F. Wash water is added with the help of metering type wash water pump 57-P-03A/B. The mixture is further cooled/ condensed in reactor effluent air condenser (57-A-01) and in reactor effluent trim cooler (57-E-02) to 45oC. DM water is received under level control (LV-2001) wash water surge drum (57-V-06). The cooled two phase mixture of hydrocarbon and hydrogen enters cold separator (57-V-03), where desulphurised naphtha is separated from the gases which mainly consist of hydrogen and light hydrocarbons. Water is separated in the water boot of the cold separator and drained under level control (LIC-1601) to SWS unit. Recycle Gas Section The gases separated in the cold separator (57-V-03) consist of mainly hydrogen and light hydrocarbon gases. These gases are compressed in recycle gas compressor ( 57-K-01A/B ) to 22.2 kg/cm2 and recycled to reactor, after it is mixed with feed naphtha at the inlet of 57-E-01A/F. Flow controller FIC-1301 at the recycle line of compressor controls the flow of recycle hydrogen to be mixed with the feed naphtha. Quench gas flow is controlled by FIC-1401 & 1501 for reactor 57-R-02A and 57-R-02B respectively cascaded through temperature controllers TIC-1405 and 1505. Makeup hydrogen is added at the suction of the compressor through FIC-1801. Naphtha Stabilization The naphtha separated in the cold separator will have light ends. These light ends are removed by flashing the naphtha in cold separator to naphtha flash drum 57-V-04 which is operating at 1.5 kg/cm2 pressure (floating with flare). The flashed naphtha from the bottom of naphtha flash vessel is pumped to storage with the help of naphtha product pumps (57-P-02 A/B). A product trim cooler (57-E-08) is used to cool down the pumped naphtha to 40 OC. REACTOR SWITCHOVER After 120 hours of operation the adsorbent of the reactor 57-R-02A which was operating in adsorption mode will get exhausted and sulfur break-through will occur. Simultaneously the other reactor 57-R-02B which was under regeneration will become ready to receive the naphtha feed. Reactor will be at 3000C and pressurized to 20 kg/cm2 with hydrogen. Now is the time for switch over of reactors which will be carried out in controlled manner so that the section downstream of reactor doesn’t get disturbed. The reactor 57-R-02B will be taken in line to receive the feed naphtha. Solenoid valve UV- 1307 & 1308 at the inlet to the reactor will be opened. The feed gas will start flowing into the reactor. After few



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seconds the solenoid valves UV-1501 and 1502 at Reactor 57-R-02B outlet will open. Once the reactors and downstream equipments are stabilized at these the two reactors in line, the switch over of the reactors from 57-R-02A to 57-R-02B, will be completed by closing the solenoid valves UV-1304 & UV-1305 at the inlet to the reactor, quench solenoid valve UV-1408 and the reactor outlet solenoid valves UV-1401 and UV-1402. Reactor 57-R-02B will now operate in adsorption mode for next 120 hours. 3.5.2 REGENERATION SECTION

The reactor 57-R-02A will undergo regeneration in the following steps. The expected time of completion of each activity is also indicated:

Activity Time, hrs Depressurization 1N2 purging 5Coke / Sulfur combustion 88N2 purging 5Activation 20Pressurization 1

The start and stop of each activity of regeneration will be controlled with the opening and closing of a set of solenoid valves. REACTOR DEPRESSURIZATION The reactor 57-R-02A will be at 20 kg/cm2 and 315 – 330oC at the end of adsorption mode of operation. The reactor which is full of naphtha vapors and hydrogen gas, will be depressurized in a controlled manner to 2.6 kg/cm2 so as to complete the depressurization activity in 1 hr. Depressurization of the reactor will be carried in two steps to maximize the recovery / utilization of HC and hydrogen of the reactor. In the first step the reactor will be depressurized to fuel gas header which is at 4.0 kg/cm2 pressure. During this stage the pressure of the reactor will reduce to 6.0 kg/cm2. In the second step the reactor shall be depressurized to flare which is at 1.7 kg/cm2 pressure. During this stage the pressure of the reactor will reduce to 2.6 kg/cm2. The depressurization of the reactor shall be started by opening of solenoid valve UV-1403 & UV-1404 at the reactor outlet and UV-2104B on the by-pass line of UV-2104A and UV-2104C and UV-2201 connecting the reactor to Fuel gas header. When the differential pressure as indicated by DPT-2104 is 2.0 kg/cm2 the solenoid valve UV-2104B shall close and UV-2104A on the main depressurization line shall open to complete the depressurization of the reactor to 6.0 kg/cm2. When the differential pressure as indicated by DPT-2104 is 0.2 kg/cm2, the solenoid valve UV-2201will close. After about 30 seconds time delay solenoid valve UV-2202 will open to depressurize the reactor to Flare. When pressure in the reactor shall get depressurized to 2.6 kg/cm2, the solenoid valve UV-2202 & 2104A, 1403 & 1404 will close and depressurization is complete. The depressurization gases are cooled in HC recovery air cooler, (57-A-02) to 55oC. The naphtha in the gases will condense and is separated in recovered HC receiver (57-V-07). The uncondensed gases consisting of mainly hydrogen will be sent to either fuel gas header or to flare.



Page | 3.7

Since the naphtha recovered will be in small quantity, the recovered HC receiver (57-V-07) has been designed to store naphtha recovered for a number of depressurizations. This naphtha shall be routed to CBD. It is expected that the reactor depressurization shall be completed in 1 hour. REACTOR PURGING At the end of 1hr time of depressurization of the reactor, the solenoid valves UV-2104 A, B and C on the reactor depressurizing line shall close and depressurization is complete. Now, the next step is purging of reactor to bring the H2/HC concentration in the reactor below 2000 ppmv, before carrying out combustion of coke & sulfur deposited on the adsorbent. Purging of the reactor shall be carried out by pressurization and depressurization method. Nitrogen of purity 99.99% shall be used for pressurization of the reactor to 6.0 kg/cm2 and then depressurized to 2.6 kg/cm2 to flare header. Reactor purging is expected to be complete in 10 pressurization and depressurization cycles. For pressurization of the reactor, the Solenoid valve UV-2101B on bypass line of UV–2101A, UV-1306 on the reactor 57-R-02A inlet line shall open. When the differential pressure indicated by DPT-2101 is 2.0 kg/cm2 the solenoid valve UV-2101B will close. UV- 2101A shall open to pressurize the reactor to 6.0 kg/cm2. When the differential pressure indicated by DPT-2101 is 0.2 kg/cm2 and reactor pressure has reached to 6.0 Kg/cm2 the solenoid valves UV-2101A and UV-1306 will close. After few seconds solenoid valves UV-1403 & 1404 on reactor outlet line, UV-2105B on the bypass line of UV-2104A, UV-2105C and UV-2202 on the vent line connecting to flare header shall open to depressurize the reactor to flare header. When the differential pressure indicated by DPT-2105 is 2.0 kg/cm2 the solenoid valve on the bypass line UV-2105B shall close and solenoid valve on main depressurization line UV- 2104A will open. When the differential pressure as indicated by DPT-2105 is 0.2 kg/cm2 the solenoid valve UV-1403, 1404 & 2104A will be closed and the reactor pressurization to 6.0 kg/cm2 will start again. The above mention steps of reactor pressurization and depressurization shall be repeated 9 more times (total 10 cycles) to bring down the hydrocarbon and hydrogen level to less than 2000 ppmv level. After achieving the desired hydrocarbon and hydrogen level inside the reactor, the reactor will be pressurized to ~ 6.0 kg/cm2 with nitrogen. At the end of purging cycle the solenoid valves UV-1306, 1403, 1404, 2101A/B, 2104A/C, 2105B & 2202 shall be closed. In order to maintain adsorbent at high temperature of 300 – 350oC hot nitrogen is used for pressurization. Electric N2 heater 57-EH-02 is used for heating the nitrogen. Unless and until the concentration of H2 / HC drops below 2000 ppmv as determined by manual sampling & analysis, the next step, which is combustion of coke and sulfur, will not start i.e. it will over-ride the signal given to open solenoid valves to proceed to next step of coke / sulfur combustion even though the 10 purging cycles have been completed. The hot mixture of N2, and hydrogen / HC exiting the reactor during purging shall be cooled in HC recovery air condenser (57-A-02). The cooled gas mixture is sent to flare. It is expected that N2 purging shall be completed in 5 hours. COKE / SULFUR COMBUSTION After nitrogen purging, the next step involves combustion of sulfur, hydrogen and coke deposited on the catalyst. This will be carried out using nitrogen containing 0.2-1.0 % oxygen by vol. The combustion gas (N2, CO2 and O2 mixture) flows in a closed loop with the help of recycle combustion gas



Page | 3.8

compressor (57-K-02A/B). Hot gas at 400oC is used for combustion. In the combustion process gases like SO2, SO3, H2O and CO2 are produced. These acidic gases (SOx) are removed by caustic scrubbing unit. Dry / oil free instrument air is added to circulating combustion gas to bring O2 content to the desired level. Circulating combustion gas is pressurized in the compressor (57-K-02A/B), heated and recycled to the reactor. Coke / Sulfur Combustion Combustion of coke, sulfur and entrapped hydrogen shall be carried out in the following four steps.

1. Heating of Adsorbent to 400oC & Pressurize the reactor to 9 kg/cm2 2. Combustion of Coke, sulfur and entrapped hydrogen, phase - I 3. Combustion of Coke, sulfur and entrapped hydrogen, phase - II 4. Complete burnout

REACTOR PURGING On completion of combustion of coke, sulfur and entrapped hydrogen, the reactor purging will be started again as explained earlier ( after reactor depressurization step ), to bring down the oxygen content of the reactor below 2000 ppmv level, so that activation of the catalyst with hydrogen can be started. The pressurization is carried out with nitrogen at elevated temperature of 350–400oC and 6.0 kg/cm2 pressure as explained in earlier section. For depressurization solenoid valves UV-1403 & 1404 on reactor outlet line, UV-2108B on the bypass line of UV-2108A, UV-2108C and UV-2304 on the combustion purge line vented to atmosphere at safe location shall open to depressurize the reactor. When the differential pressure indicated by DPT-2106 is 2.0 kg/cm2 the solenoid valve on the bypass line UV-2108B shall close and solenoid valve on main depressurization line UV- 2108A will open. When the differential pressure as indicated by DPT-2106 is 0.2 kg/cm2 the solenoid valve UV- 1403, 1404 & 2108A will be closed and the reactor pressurization to 6.0 kg/cm2 will start again. The above mention steps of reactor pressurization and depressurization shall be repeated 9 more times (total 10 cycles) to bring down the oxygen level to less than 2000 ppmv level. Venting to safe location shall be routed through purge gas pipe(finned) and solenoid valve UV-2304. Manual sampling and analysis of the purge gas to be done to ensure that oxygen concentration is below 2000 ppmv. Unless the oxygen content drops below 2000 ppmv, the next step for activation of the adsorbent will not be initiated, in-spite of nitrogen purging step continuing for 5 hrs i.e. it will over-ride the signal for opening of solenoid valves for start of activation. After achieving oxygen concentration below 2000 ppmv the reactor is pressurized with nitrogen to 6 kg/cm2. It is expected that purging of the reactor will be completed in 5 hrs time and solenoid valves UV-1306, 1403, 1404, 2101A/B, 2108A/B/C, 2304 and 2305 shall get closed on completion of purging. CATALYST ACTIVATION On completion of the purging of the reactor, the activation of the adsorbent with hydrogen is started. Activation of the adsorbent involves exothermic reduction of adsorbent metal oxides, formed during combustion step, with hydrogen to form water and activated metal. The activation of the catalyst is carried out with a recycle gas mixture of hydrogen and nitrogen at 400-450oC and 10.0 kg/cm2 pressure. Hydrogen concentration in this mixture is raised slowly from 0.2% to 1% (v/v). The gas mixture is circulated with the reactor with the help of recycle activation gas compressor (57-K-03). Recycle activation gas compressor is started on recirculation with itself and is



Page | 3.9

pressurized to 11.2 kg/cm2. Once the discharge pressure of 11.2 kg/cm2 is achieved the compressor discharge is lined up-to reactor 57-R-02A to pressurize the reactor to 10.0 kg/cm2. The solenoid valves UV-2103, reactor inlet solenoid valve UV-1306 will be opened. When the reactor pressure is reached to 10 kg/cm2 then UV-1403, 1404 & 2109 at the reactor outlet are opened and activation gas circulation with the reactor is started. The pressure at the suction of the compressor is maintained with the help of PIC-2704 by admitting nitrogen from the pressure control valve PV-2802B or venting to flare through PV-2801A. The temperature of the activation gas entering the reactor will be raised by exchanging heat with the hot reactor effluent in activation gas effluent exchanger (57-E-06A/B/C) and electric activation gas heater (57-EH-04) through TIC-2709. During startup activation gas will be heated to 400oC with the help of electric activation gas heater (57-EH-04). After about 15-30 minutes of opening of UV-1403 & 1404, the solenoid valve UV-2701 on the hydrogen line to the suction of the compressor 57-K-03 will open. Hydrogen flow to the suction of the compressor is provided in a controlled manner with the help of flow control valve FV-2701 which in turn is cascaded with TDIC-1432 provided on reactor 57-R-02A. Reactor effluent gases will be at 450oC. Hot effluent gases will exchange heat in activation gas effluent exchanger (57-E-06A/B/C) thereby heating activation gas feed. Hot effluent gases will be further cooled by activation effluent air cooler (57-A-04) and activation effluent trim cooler (57-E-07) to 45oC. Since water is a product of activation of the adsorbent the cooled effluent gases are fed to activation gas compressor KOD (57-V-10) where condensed water will be separated. Gas from KOD shall enter recycle activation gas compressor and is pressurized to about 11.2 kg/cm2 before being recycled to reactor. For achieving good activation, the catalyst temperature in the bed should be maintained at about 400oC. The temperature can be maintained with the help of activation gas temperature at the inlet to reactor as well as hydrogen content of the gas. The hydrogen content of the gas is controlled with the help of TDIC-1432 provided at the reactor 57-R-02A. The TDIC-1432 controls the hydrogen content of the gas mixture at the desired value by controlling the flow of hydrogen through the flow control valve FV-2701. During adsorbent activation initially the temperature difference across the reactor as indicated by TDIC - 1432 will rise, stabilize and then fall. The temperature rise across the bed is to be controlled to a maximum of 50oC. When the temperature rise across the bed falls below 10oC the catalyst activation is complete. It is expected that activation of the adsorbent will be completed within 20 hrs of time. Close hydrogen make up line UV-2701. The reactor is to be cooled to 300oC by continuation of activation gas circulation with no hydrogen addition. The temperature of the activation gas at the inlet to the reactor shall be controlled by electric activation gas heater (57-E-04). Once the reactor temperature of 300oC is achieved, the reactor is to be depressurized to remove nitrogen from the reactor. Stop recycle activation gas compressor 57-K-03 and close UV-2103, 1306 at the reactor inlet and UV-1403, 1404 and 2109A/B at reactor outlet. Open UV-1403, 1404 and UV-2105B on the bypass line of UV-2104A, UV- 2104C and UV-2202 to depressurize the reactor to flare. When DPT-2105 shows a differential pressure of 2.0 kg/cm2, UV-2104B will close and UV-2104A will open. When DPT-2105 shows a differential pressure of 0.2 kg/cm2, UV-2104A/C and UV-2201 will close and reactor pressure will be about 2.6 kg/cm2. The hot gases exiting from the reactor are first cooled in HC recovery air condenser (57-A-02) to 55oC and then go to flare. It is expected that depressurization of the reactor will be completed in 30 minutes.



Page | 3.10

PRESSURIZATION In this stage the reactor (57-R-02 A) is pressurized with hydrogen to 20 kg/cm2 and get ready to switch over. UV-1409 and UV-1408 on the quench line will be opened. Recycle gas will start to circulate inside the reactor 57-R-02A to pressurize the reactor from 2.5 kg/cm2 to 20 kg/cm2. When the pressure of the reactor is reached to 20 kg/cm2 as indicated by PI-1401, pressurization is complete. UV-1409 and Uv-1408 will be closed. Pressurization will be completed within an hour. Now the reactor is ready for switch over to adsorption stage.

3.6 MS Auto Blending

Automation of on-line blending is carried out by receiving all streams from the tank-farm, measuring the flow of each stream, obtain the approximate qualities of these streams from data base, run blend Optimizer and BPC taking into consideration analyser output, cost of different cutter stocks, cutter stock availability and quality and control the flow of key component streams. Before starting the batch, system will take tank heels quality and quantity into consideration. If the blend header runs into out of controllability, the system will keep track of tank composite quality and take necessary action to correct the tank quality before closing the batch. In case of failure of analysers, property prediction software will replace analyser and batch will be prepared by meeting the specification. All the blending streams after joining together in the blending manifold will be routed to product tanks through static mixer. On line analyser NIR (Near Infra-Red) or ASTM type analyses properties of blended product and give output directly to BPC. Flow control valves are provided for all the streams for controlling the flow through BPC/BRC. The streams are taken from the tanks through individual tank pumps.



Page | 4.1

4. STUDY METHODOLOGY

4.1 Quantitative Risk Analysis

The five normal components of a Quantitative Risk Assessment (QRA) study are: Hazard, (or failure case) identification Failure frequency estimation Consequence calculations Risk calculation (Risk Summation) Risk assessment (using an acceptability criteria)

Figure 4.1 below shows the relationship of each step and the additional external data requirements.

Figure 4.1: Classical Approach of QRA

PlantData

DeriveFailureCases

CalculateFrequencies

CalculateConsequences

GenericFailure Rate

Data

MeteorologicalData

SafetyManagement

Factor

CalculateRisks

AssessRisks

IgnitionData

PopulationData



Page | 4.2

This QRA study has been carried out by IRCA using the DNV software package PHAST RISK (earlier known as SAFETI) current Version 6.7. 4.1.1 Collection of Data

The total data requirement can broadly be put in five categories as under: Plant data Generic failure rate data Meteorological data Population data Ignition source data

The plant data are derived from the description of facilities (PFDs, P&IDs, Lay out plans etc.). 4.1.1.1 Failure Case Identification and Definition

The first stage in any QRA is to identify the potential accidents that could result in the release of the hazardous material (oil & gas in this study) from its normal containment. This is achieved by a systematic review of the facilities together with an effective screening process. PHAST software can model toxic and flammable effects based on properties of the material. Sectionalization For the purpose of defining the failure scenarios to be considered in risk analysis, the plant is divided into sections containing significant inventory of hazardous material with defined isolation arrangement (shut-down valve, remote operated valve, NRV, pump etc.). Averaged process conditions and composition for the section will be used in the analysis. Where relevant (e.g. Separator), release of gas and liquid from the section will be considered separately. Defining process materials PHAST has provision to define mixtures of pure components. This feature is used to define mixtures to represent the process streams relevant to the study for modelling releases from the sections. Selection of leak sizes There is a possibility of failure associated with each mechanical component of the plant (vessels, pipes, pumps or compressors). These are generic failures and can be caused by such mechanisms as weld failure, corrosion, vibration or external impact (mechanical or overpressure). The range of possible releases for a given component covers a wide spectrum, from a pinhole leak up to a catastrophic rupture (of a vessel) or full bore rupture (of a pipe). It is both time-consuming and unnecessary to consider every part of the range; instead, representative failure cases are generated. For a given component these should represent fully both the range of possible releases and their total frequency. The range of leak sizes considered for QRA is listed in Table 4.1.



Page | 4.3

Table 4.1: Representative Leak Sizes for QRA

Leak Type Representative hole Size (mm) Small leak 3 Medium leak 10 Large leak 50 Rupture 100

For each identified failure case, the appropriate data required to define that case are input to the PHAST RISK package. When the appropriate inputs are defined, PHAST RISK calculates the source terms of each release, such as the release rate, release velocity, release phase and drop size. These source term parameters then become inputs to the consequence modelling. Alternatively, PHAST RISK allows these source terms to be input directly. 4.1.1.2 Failure frequency data

Leak frequency for each leak size will be estimated using generic leak frequency data available in the latest publication ‘Risk Assessment Data Directory’ by International Association of Oil & Gas Producers (OGP), UK. The database contains generic leak frequencies for various categories of pipes, flanges, valves, pressure vessels, process equipment, instrument fittings etc. The leak frequencies are available for different leak sizes.

First calculate the failure frequencies for each leak size and then create a table for each of the failure case

For each case, count the number of each type of item (valve, flange, equipment etc.) in the plant section from P&I diagrams and layout drawings.

Insert the failure frequencies for each type of item. Multiply by the number of items to obtain the frequency for each item type and leak size. Sum the frequencies for each leak size over all the items to give the case frequencies for each

leak size in the plant section. 4.1.1.3 Meteorological data

The following weather data are required for QRA. Ambient temperature, relative humidity Wind speed, wind direction and atmospheric stability in the form of wind rose data indicating the

annual probability distribution.

4.1.1.4 Population data

The quantitative risk assessment using PHAST RISK is concerned with risk of fatality due to exposure to toxic and flammable effects following the accidental release of hazardous material from the plant. In PHAST RISK, the population distribution in and around the plant is to be defined on the site map drawing.



Page | 4.4

4.1.1.5 Ignition source data

The following ignition sources are generally encountered in process plants. Fired heaters, boilers Ordinary electrical equipment such as transformers, switchgear room High voltage transmission lines Transportation – roads and railway lines Workshops, garages, restaurants etc. Residential buildings

Data on the ignition sources in and around the plant are based on the plot plan and site map drawings. 4.1.2 Risk Calculation

The final estimation of risk is carried out by PHAST RISK package based on the input data detailed above. Each failure case is analysed to determine its impact (in terms of fatalities). Effect zone information generated by consequence analysis is combined with meteorological, ignition source and population data. Event tree conditional probabilities leading to a particular outcome and frequency information, extracted from the original failure case description, are used to determine the level of risk for the specific failure case under analysis. PHAST RISK generates the required standard forms of risk measure. It calculates both individual risk at grid points and the societal group risk of each incident outcome. To calculate group or societal risk, the total number of fatalities for each release case, event tree outcome, weather type and wind direction must be calculated. The frequencies of all those combinations contributing to the same number of fatalities must be added. The PHAST RISK package allows these results to be presented in the form of an FN group risk curve. An FN curve is a graph, which plots the frequency of N or more fatalities per year (F) against the number of fatalities (N). It is conventional that this information is presented on a log-log plot.



Page | 4.5

4.1.3 Risk Presentation

The risk levels associated with the facilities will be presented in the following standard forms:

Individual risk contours which show the geographical distribution of risk to an individual. Group risk (FN) curves which show the cumulative frequency (F) distribution of accidents

causing different numbers (N) of fatalities. The FN curve therefore indicates whether the societal risk to the facility is dominated by relatively frequent accidents causing small numbers of fatalities or low frequency accidents causing many fatalities.

4.1.3.1 Risk Assessment

The final, and most significant, step in the process is the assessment of what the calculated risk levels portray. Risk assessment is a process by which the results of a risk analysis are used to make judgments, either through relative risk ranking of risk reduction strategies or through comparison with risk targets (criteria). Where risk criteria have been issued by the regulatory authority, it is possible for interested parties to assess the calculated risk levels against these criteria. The risk assessment stage determines whether the risks are tolerable, or if risk mitigation measures are required to reduce the risk to a level, which can be considered to be as low as reasonably practicable (ALARP). 4.1.3.2 Risk Tolerability Criteria

A risk analysis provides measures of the risk resulting from a particular facility or activity. However, the assessment of the acceptability or otherwise of that risk is left to the judgement and experience of the people undertaking and/or using the risk analysis work. The normal approach adopted is to relate the risk measures obtained to acceptable risk criteria. A quantitative risk analysis produces only numbers, which in themselves provide no inherent use. It is the assessment of those numbers that allows conclusions to be drawn and recommendations to be developed. The assessment phase of a study is therefore of prime importance in providing value from a risk assessment study. Individual risk Criteria The acceptability criteria for individual risk to workers and members of the public have been defined recently by IOCL for its project as shown in Figure 4.2.



Page | 4.6

Figure 4.2: Individual Risk Criteria for IOCL

(Negligible Risk)



Page | 4.7

Group Risk Criteria – FN Curves

The acceptability criteria for societal risk have been defined recently by IOCL for its earlier Project (QRA report no.: IRCA-IOCL-QRA-20121332-01 for IOCL Paradip Refinery Project) as shown in Figure 4.3.

Figure 4.3: Societal Risk Criteria for IOCL

(Negligible Risk)



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4.2 Consequence Analysis

Consequence analysis has been carried out using the DNV PHAST software latest version 6.7. PHAST is a software package developed by DNV, which provides a standard and validated suite of consequence models which can be used to predict the effects of a hydrocarbon release. Consequence analysis provides quantitative information about the flammable effects and toxic gas dispersion resulting from release of material due to loss of confinement. Flammable effects When the dispersing cloud containing flammable material above LFL concentration comes into contact with ignition source, there is potential for the following.

Jet fire Pool fire Flash fire Vapour cloud explosion

Jet Fires

Jet fires are usually associated with releases of gas. They have high momentum and high heat flux radiation levels. At high release rates, the jet becomes highly turbulent, entrains more air and burns hotter. The flame will stabilize on or near the point of release and will have a torch or fan-like appearance, depending on the type of release. The primary method for controlling jet fires is by isolation and blow-down of the inventory to starve the fire of fuel, with passive fire protection, as appropriate, to prevent escalation. Pool Fires

Pool fires may occur in any area where flammable liquids are stored. It should be noted that the fuel pool is not necessarily static and can spread or contract with respect to the leak rate of the hydrocarbon and its burning rate, and according to any slope of the underlying surface. Leaking liquid hydrocarbons will be removed from the immediate area by the hazardous open drains system, reducing the available fuel inventory and therefore reducing the potential size and duration of any pool fire. Pool fires have little or no momentum and lower heat fluxes than jet fires. They may be adequately controlled using a solution of firewater and fire fighting foam. A pool fire cannot be quickly eliminated by isolating the fuel supply alone. Flash Fires

Where a gas cloud develops in an unconfined environment and where ignition is delayed, a flash fire can occur where rapid combustion occurs through the cloud similar to an explosion, but with little overpressure. The speed of combustion is also much less than in an explosion.



Page | 4.9

4.3 Explosions

Delayed ignition of a gas cloud can result into explosion. The overpressures generated by explosion have the potential to damage buildings/structures and cause secondary fires. Toxic Gas Dispersion

Release of toxic compounds (H2S & Chlorine) resulting in a toxic vapour cloud, before it becomes sufficiently diluted to no longer be considered toxic. 4.3.1 Event Identification

There are a large number of fire, explosion and toxic dispersion events that could occur. The consequence analysis has focused on those events that would have a significant effect on the safety of personnel and assets. 4.3.2 Inventory Identification

The process and storage units are sub-divided into discrete isolatable systems. The approach used was to review the process and relevant utility P&IDs and to identify the sections containing large inventory of hazardous material that can be isolated by operation of valves. Each section is then characterized by the following parameters required for consequence modelling:

Mass of flammable material in the process/ storage section (oil/ gas) Pressure, temperature and composition of the material Hole size for release

4.3.3 Release Size Definition

Releases from process equipment can be of any size from very small releases (1 mm flange leak) to large releases (catastrophic rupture of a large pressure vessel or flow line). In order to obtain only the results of consequence analysis for specific release scenarios, it is necessary to model these cases directly in PHAST. For example, consequence analysis using leak sizes of 50.8 mm (2 inches) and normally prevailing weather conditions are used for review of layout, emergency escape routes, location of emergency systems etc. taking into account the effects of fire and explosion due to accidental releases. Performing consequence analysis using PHAST provides graphical results plotted on site map in addition to tabular results. The Refinery complex involves the handling and processing of both flammable and toxic materials. Loss of containment of pressurized flammable gases could lead to fire or a vapour cloud explosion. Whilst a loss of containment of toxic materials such as hydrogen sulphide on site could lead to health risks associated with toxic exposure.



Page | 4.10

Release of flammable or toxic materials to the atmosphere can lead to one of the following: Immediate ignition of released vapour resulting in a Jet Fire. Spreading of flammable vapour with the wind until its lower flammability limit is reached or an

ignition source found, which will result in a Flash Fire or explosion. Spillage of flammable liquid on the ground resulting in formation of a pool of liquid, which will

evaporate taking heat from the ground surface thereby forming a flammable atmosphere above the pool. Ignition of this atmosphere will result in a pool fire.

Explosion of a confined/unconfined vapour cloud will generate over-pressure. Release of toxic compounds resulting in a toxic vapour cloud, before it becomes sufficiently

diluted to no longer be considered toxic.

4.4 Damage Criteria

Flash Fire Flammable vapour, after loss of containment, will normally spread in the direction of the wind. If it finds an ignition source before being dispersed to below its Lower Flammability Limit (LFL), a Flash Fire is likely to result and the flame may travel back to the source of the release. Any person caught in a Flash Fire is likely to suffer fatal burn injuries. Therefore, in this consequence analysis, the distance at which LFL is achieved is calculated to indicate the area which may be affected by a Flash Fire.



Page | 4.11

Thermal Radiation Thermal radiation due to a pool fire or jet fire may cause various degrees of burns on human bodies or damage to objects, such as piping or equipment. Table 4.2 tabulates thermal radiation intensities and their damage effect in case of an incident.

Table 4.2: Damage due to incident radiation intensities

Intensity Radiation (kW/m²)

Type of Damage

37.5 Sufficient to cause damage to process equipment

32 Maximum allowable radiation intensity on thermally protected and pressurised storage tank

25 Minimum energy required to ignite wood at infinitely long exposure (non-piloted)

12.5 Minimum energy required for piloted ignition of wood, melting of plastic etc.

8 Maximum allowable radiation intensity on thermally unprotected and pressurised storage tank

4 Sufficient to cause pain to personnel if unable to reach cover within 20 seconds; however, blistering of skin (1st degree burn) is unlikely

1.6 Intensity insufficient to cause discomfort for long exposures

0.7 Equivalent to Solar Radiation

Thermal hazard distances to 37.5 kW/m², 12.5 kW/m² and 4 kW/m² radiation intensity are considered in consequence analysis. For thermal hazards over 37.5 kW/m² escalation may occur. For thermal hazards of 12.5 kW/m² or higher combustibles on buildings may spontaneously ignite. For thermal hazards of 4 kW/m² or higher personnel injury may occur. Storage tank farm The possible damage effect from the Tank Farm may manifest itself in the following ways:

Damage due to thermal radiation from tank fire and dyke fire Damage due to Flash Fire owing to flammable spill in dyke

These may affect people and property within and outside the facilities.



Page | 4.12

Although 37.5 kW/m² incident radiation intensity level is hazardous for adjacent tanks, while deciding the layout for tank spacing consideration, a maximum of 32 kW/m² radiation intensity is permitted on adjacent thermally protected tanks (e.g. with water sprinklers or insulation etc.) and a maximum of 8 kW/m² is permitted on adjacent thermally unprotected tanks. For this study, it is assumed that for a tank fire, the peak level of radiation intensity is not reached suddenly. It will take some time for a tank fire to grow to full size. For fixed roof tanks, the roof will have to be blown off before the full diameter fire can develop. Similarly, for floating roof tanks, a fire initially starts as a rim fire. If this can be sensed and tackled immediately, spreading into a large fire can be avoided. However, for the purpose of this study, a full tank fire has been considered. Incident radiation intensity of 4 kW/m² on a public road beyond the perimeter of the facility has been specified as the criterion to judge the acceptability of the current layout under this scenario. Explosion In the event of a flammable gas cloud being ignited, an explosion can occur. The resultant blast wave will have damaging effects on plant and buildings failing within the overpressure contours. The human body, can by comparison, withstand higher overpressure. However, injury can occur from collapse of buildings or structures.

Explosion overpressure damage effects relating to building type are shown in Table 4.3.

Table 4.3: Damage effects of blast overpressure

Building type Overpressure (psig)

Consequences

B1: Wood-frame trailer or Shack

0.2 Onset of serious damage 1.0 Isolated building overturned; temporary building

complexes partially destroyed. B2: Steel Frame / metal siding or pre-engineered building

>1.5 Sheeting is ripped off. Internal walls damaged. >2.5 Cladding & walls damaged, but building frame

stands. >5.0 Complete building collapse.

B3: Un-reinforced masonry bearing wall building

1.0 Walls collapse. 1.5 Total building collapse.

B4: Steel or concrete framed with reinforced masonry infill or cladding

1.0 Wall damage. 2.0 Roof slab may collapse. 2.5 Total building collapse.

B5: Reinforced concrete or masonry shear building

2.0 Very minor damage.

4.0 Roof and walls will deflect under loading and internal wall damage.

6.0 Major damage and possible collapse.



Page | 4.13

Damage effects due to 5 psi, 3 psi, 1 psi and 0.5 psi in terms of distance from the overpressure source are used in this consequence analysis. For overpressures of 5 psi or greater blast resistance will be required for buildings that are required to survive the event (e.g. buildings providing refuge or performing shutdown/ emergency functions). Buildings potentially experiencing pressures greater 0.5 psi should not have external glass. Buildings located within the zone between the 5 psi overpressure and the 1 psi overpressure contours may require some degree of blast protection. This should be assessed on a case by case basis by the relevant building designer. Toxic Release The aim of the toxic risk study is to determine whether the operators in the plant, people in occupied buildings and the public are likely to be affected by toxic substances. Toxic gas cloud dispersion to the Immediately Dangerous to Life and Health Concentration (IDLH) limit is normally considered to determine the extent of the toxic hazard created as the result of loss of containment of a toxic substance. The IDLH values available in current NIOSH publication are used for consequence analysis. In addition, the short term exposure limits currently specified in the Second Schedule of Factories Act, “Permissible Levels of Certain Chemical Substances in Work Environment” are also considered in consequence analysis mainly to identify the areas where awareness to the toxic hazard is to be developed. The toxic materials and concentrations normally used in consequence analysis are shown in Table 4.4.

Table 4.4: Toxicity values

Chemical IDLH

Concentration (ppm)

STEL Concentration

(ppm) Ammonia (NH3) 300 35

Carbon monoxide (CO) 1200 400 Chlorine (Cl2) 10 3 Hydrogen sulphide (H2S) 100 15 Sulphur dioxide (SO2) 100 5

STEL = Short Term Exposure Limit = A short-term exposure limit (STEL) is the acceptable average exposure over a short period of time, usually 15 minutes as long as the time-weighted average is not exceeded. In the scope of the present study for BS-VI project, toxic gas dispersion is not significant.



Page | 4.14

Consequence Analysis General Input to PHAST Consequence analysis is carried out using the current version 6.7 of PHAST software package of DNV. The study file for consequence analysis will be basically the same as that used for QRA by PHAST Risk. The input data for materials and process conditions will be the same for the models. Weather parameters considered for consequence analysis are listed in Table 4.5.

Table 4.5: Weather Parameters for Consequence Analysis

Wind speed, m/s 3 5

Atmospheric stability class D D

Ambient temperature, C 30 30

Relative humidity, % 80 80

Results of consequence analysis such as intensity radii for jet fire and pool fire, flash fire envelope, explosion overpressure radii and toxic cloud footprint are plotted on the site map. In addition, tabular results are also provided as output from PHAST.



Page | 5.1

5. STUDY INPUTS

The total data requirement for QRA can broadly be put in five categories as under:

Plant data Generic failure rate data Population data Meteorological data Ignition source data

5.1 Plant Data

QRA study conducted is based on the data available from current engineering documents developed for the BS-VI Project in IOCL Guwahati Refinery. These documents are listed in Table 5.1.

Table 5.1: Reference Documents

Sr. No Document / Drawing Document Drawing No.

1 Facilities Description Provided by IOCL

2 Process Flow Diagrams

For HDT Unit: 9019865-110-01-PFD to 12-PFD For HGU Revamp: 074221C001-PFD-0010-001 to 015 Rev-00 For indeselectG Unit: A964-04-0102 and 0103 Rev-00 For ISOM Unit: 56-5FD-2A Rev-01

3 Material Balance Provided by IOCL

4 Piping & Instrumentation Diagrams

For HDT unit: 9019865-120-01-PID to 36-PID Rev-01 For HGU : 74221C001-PID-0010-000 to 002 Rev-00, 074221C001-PID-0020-001 to 021 Rev-00, 074221C001-PID-0040-001 to 005 Rev-00 For indeselectG Unit: A964-04-1181 to 1192 REV 0 For ISOM unit: 1715-56-1192 to 94



Page | 5.2

Rev-0, 07-3040-056-14/17 Rev-7

5 Plot plan/ Equipment Layout

For HDT unit: 9019865-MISC-01 to 02 Rev 00 For HGU unit: 074221C001-DW-0051-002-06 & 074221C001-DW-0051-003-06 For indeselectG unit: 44AC270004L010001 Rev-0 For ISOM Unit: 44AC2700-56-L.01-0001-A1_A & 44AC2700-56-L.01-0002-A1_A

6 Layout Plan of Guwahati Refinery TS-00-150 Rev-19



Page | 5.3

5.2 Generic Failure Rate Data

Generic leak frequency data published by International Association of Oil & Gas Producers (OGP) are used in this QRA study. An extract from OGP Risk Assessment Data Directory - Report No. 434 (March 2010) used in present study is reproduced in the Table 5.2.

Table 5.2: Failure Frequencies (OGP Data)

Equipment Overall Failure Frequency [per year]

Equipment/ Item

Minor Leak Medium Leak Major Leak Full bore Rupture Total

[ 3 mm] [10 mm] [25 mm] [100 mm] [>100 mm]

Process Pipe < 2" 9.00E-05 3.80E-05 2.70E-05 1.6 E-4

Process Pipe < 6" 4.10E-05 1.70E-05 7.40E-06 7.60E-06 7.3 E-5

Process Pipe < 12" 3.70E-05 1.60E-05 6.70E-06 1.40E-06 5.90E-06 6.7 E-5

Flanges < 2" 4.40E-05 1.80E-05 1.50E-05 7.7 E-5

Flanges < 6" 6.50E-05 2.60E-05 1.10E-05 8.50E-06 1.1 E-4

Flanges < 12" 9.60E-05 3.90E-05 1.60E-05 3.20E-06 7.00E-06 1.6 E-4

Manual Valves < 2" 4.40E-05 2.30E-05 2.10E-05 8.8 E-5

Manual Valves < 6" 6.60E-05 3.40E-05 1.80E-05 1.10E-05 1.3 E-4

Manual Valves < 12" 8.40E-05 4.30E-05 2.30E-05 6.30E-06 7.80E-06 1.6 E-4

Actuated Valves < 2" 4.20E-04 1.80E-04 1.10E-04 7.1 E-4

Actuated Valves < 6" 3.60E-04 1.50E-04 6.60E-05 3.30E-05 6.1 E-4

Actuated Valves < 12" 3.30E-04 1.40E-04 6.00E-05 1.30E-05 1.80E-05 5.6 E-4

Instrument Connections 3.50E-04 1.50E-04 6.50E-05 5.7 E-4

Process (Pressure) Vessels 9.60E-04 5.60E-04 3.50E-04 2.80E-04 2.2 E-3

Pumps - Centrifugal 5.10E-03 1.80E-03 5.90E-04 1.40E-04 7.6 E-3

Pumps - Reciprocating 3.30E-03 1.90E-03 1.20E-03 8.00E-04 7.2 E-3

Compressor-Reciprocating 4.50E-02 1.70E-02 6.70E-03 2.00E-03 7.1 E-2

Heat Exchanger 2.20E-03 1.10E-03 5.60E-04 2.60E-04 4.1 E-3

Coolers 1.00E-03 4.90E-04 2.40E-04 1.10E-04 1.8 E-3

Filters 2.00E-03 1.00E-03 5.20E-04 2.60E-04 3.8 E-3



Page | 5.4

5.2.1 The Approach to Calculate Failure Frequency

First calculate the failure frequencies for each leak size and then create a table for each of the failure case

For each case, record the number of each type of item. Insert the failure frequencies for each type of item. Multiply by the number of items to obtain the frequency for each item type and leak size. Sum the frequencies for each leak size over all the items to give the case frequencies.

For this study the whole plant is divided into number of sections. The philosophy is to consider isolatable sections. Once the items counts are completed, frequency analysis is performed for different hole sizes envisaged in each process section. The Assumption Sheet summarizing the parameters forming basis for this QRA study is presented in Attachment-I. Details of the failure cases with estimated leak frequencies are presented in Attachment-II titled “Failure Cases Input to PHAST RISK”.

Section No. Section description Material Process conditions (pressure, temperature) Inventory Leak frequency for selected hole sizes



Page | 5.5

5.3 Meteorological Data

The consequences of releases of flammable materials into the atmosphere are strongly dependent upon the rate at which the released material is diluted and dispersed to safe concentrations. The rate of dispersion is dependent on the meteorological conditions prevailing at the time of release, particularly the wind speed and the degree of turbulence in the atmosphere. The wind direction is also of importance as it determines the direction in which the cloud of material will travel. Meteorological data are thus required at two stages of the risk analysis. Firstly, various parts of the consequence modelling require specification of wind speed and atmospheric stability. Secondly, the impact calculations require wind-rose frequencies for each combination of wind speed and stability specified. The primary requirement is to choose a suitable number of combinations of wind speed ranges and stabilities for the dispersion modelling and thermal radiation calculations. These combinations must reflect the full range of observed variations in these quantities; at the same time it is neither necessary nor computationally efficient to consider every combination observed. The procedure used is therefore to group these combinations into representative weather classes which together cover all conditions observed. The classes chosen must be sufficiently different to produce significant variations in dispersion modelling. These critical conditions are, in general, for short-duration releases, high wind speed and, for long duration releases, low wind speed with stable stratification. Whilst speed and direction are clear in definition, stability is not a widely used term. Stability is determined by the temperature gradient in the lowest tens of metres of the atmosphere; this in turn depends on the heating (in the day) or cooling (at night) at the ground and on the mean wind speed. The stability determines the degree of turbulence in the atmosphere and hence of mixing-in of air to a released gas cloud by ambient turbulence: very unstable conditions (occurring in the middle of a calm, sunny day) lead to much turbulence and hence rapid dispersion while very stable conditions (occurring on a clear night) inhibit turbulence and hence dispersion. Stability is conventionally classified by Pasquill stability classes, denoted A to F. Table 5.3 shows the typical split of Pasquill Stability categories according to surface wind speed and atmospheric conditions.

Table 5.3: Definition of Pasquill Stability Classes

Surface Wind Speed (m/s)

Insolation Day Time

Night Sky

Strong Moderate

Thinly Overcast

<3/8 Cloud

< 2 A A/B - - 2-3 A/B B E F 3-5 B B/C D E 5-6 C C/D D D > 6 C D D D



Page | 5.6

Atmospheric stability categories A (very unstable), D (neutral) and F (stable) are described below. Category A (very unstable) occurs typically on a warm sunny day with light winds and almost cloudless skies when there is a strong solar heating of the ground and the air immediately above the surface. Bubbles of warm air rise from the ground in thermals. The rate of change (decline) of temperature with height (lapse rate) is very high. Category D (neutral) occurs in cloudy conditions or whenever there is a strong surface wind to cause vigorous mechanical mixing of the lower atmosphere. Category F (stable) occurs typically on a clear, calm night when there is a strong cooling of the ground and the lowest layers of the atmosphere by long wave radiation. There is a strong inversion of temperature (i.e. warm air over cold air).

The wind rose diagram for Guwahati is shown in Figure 5.1.

Figure 5.1: Wind Rose Diagram for Guwahati Refinery

The distribution of wind direction and wind speed established for this study is shown in Table 5.4.

Table 5.4: Meteorological Data (Day/Night)

Wind speed Stability

Class

Temp RH Wind Direction (From)

(m/s) C % N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW

1.5 D 30 80 0.04 0.03 0.12 0.02 0.03 0.00 0.00 0.00 0.03 0.03 0.02 0.01 0.04 0.01 0.03 0.01

3 D 30 80 0.01 0.02 0.09 0.02 0.01 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.03 0.01 0.01 0.00

Total 0.05 0.05 0.21 0.04 0.04 0.00 0.00 0.00 0.04 0.04 0.03 0.01 0.07 0.02 0.04 0.01



Page | 5.7

5.4 Population Data

This QRA study covers the fatality risk to people by exposure to flammable and toxic hazards. The data for distribution of people in the plant area have been provided by IOCL. The population distribution considered for BS-VI Project QRA is shown in Table 5.5.

Table 5.5: Distribution of People in and around units

AA) Population in and around HDT Unit

S. No. Description No. of Persons Day Night

1. Shift-in-Charge 2 1 2. Panel Operator 2 1 3. Field Operator 4 2 4. General Shift Officer 2 0

BB) Population in and around HGU Unit



CC) Population in and around INDESELECT-G Unit



DD) Population in and around DEISOPENTANISER Unit





Page | 5.8

Outside Unit Population


1. Substation Building North side of HDT unit

2 2

2. Control Room North side of HDT unit

100 20

3. Operator Room east side of HGU unit

30 8

4. New operator room east side of HGU unit

30 8

5. Proposed substation for INDESELECTG Unit

2 2

6. Fire station near proposed substation for INDESELECTG Unit

24 9

7. Old control room north side of INDESELECTG Unit

9 9

8. Contractor Shed north west side of deisopentaniser unit

0 0

9. Maintenance building west side of INDESELECTG Unit

14 0

10. Project CELL office west side of INDESELECTG Unit

0 0

11. Operator around tanks (T-23 /29) 0 0 12. Operator around tanks (T-2/4) 0 0



Page | 5.9

Ignition Source Data

If a flammable release is not ignited immediately, then its chance of ignition is dependent upon the presence of ignition sources that may be in the vicinity. The probability of immediate ignition, however, is normally due to the nature of the release (e.g. a release due to external impact is likely to be ignited immediately due to heat caused by friction). If an ignition source is not reached, or the ignition source is insufficient to ignite the release, then the release will have no impact. In order to address delayed ignition, PHAST RISK requires information about the distribution of ignition sources in the vicinity of the plant, together with information about their ignition strength. Several different types of ignition source are possible, such as fired heaters, boilers, workshops (welding), motor vehicles and people. Other ignition sources must be individually defined. Each source can be defined as a point source (e.g. a boiler), an area source (e.g. a workshop) or a line source (e.g. a road). For every source the probability of it being present at any given time must be defined along with its ignition strength. For example, a fired heater in a refinery would be continuously present and would have a high probability of igniting a flammable cloud as soon as the cloud passed over it. The ignition sources defined in the BS-VI projects units are shown in Table 5.6.

Table 5.6: Ignition Sources at BS-VI units

Description

Ignition Probability (Fraction)

Operating Probability (Fraction)

Sub-Stations 0.4 1 Switch Gear Room 0.4 1 Transformers 0.2 1



Page | 6.1

6. RISK ANALYSIS RESULTS

6.1 Individual Risk

Figure 6.1.1 shows the iso–risk contours representing Location specific individual risk (LSIR) due to BS-VI project and its associated facilities on the next pages. The highest risk contour in BS-VI project area is of 10-4 per year which is in HGU unit , HDT unit, ISOM unit and IndeselectG unit.. However, this does not mean that there is an intolerable risk to the workers in the above units. In fact the actual risk to any one worker will be far less than the maximum in this area considering the fraction of time the individual is present there. MS Auto Blending Unit The highest risk contour in MS Auto Blending unit area is of 10-4 per year. However, this does not mean that there is an intolerable risk to the workers in the above units. In fact the actual risk to any one worker will be far less than the maximum in this area considering the fraction of time the individual is present there. Refer Figure 6.1.2 that shows iso–risk contours representing Location specific individual risk (LSIR). IndadeptG Unit: As existing IndadeptG revamp is for reliability improvement purpose and not for capacity increase therefore there is no additional risk associated with change in IndadeptG revamp. For base risk please refer QRA report of IndadeptG Unit (Report No. IRCA-IOCL-QRA-20121345-01 Rev-1)



Page | 6.1

Figure 6.1.1: Iso-Risk Contours for BS-VI Project – Overall



Page | 6.2

Figure 6.1.1a: Iso-Risk Contours near HDT/HGU units – Enlarge view



Page | 6.3

Figure 6.1.1b: Iso-Risk Contours near ISOM unit – Enlarge view



Page | 6.4

Figure 6.1.1c: Iso-Risk Contours near indeselectG unit – Enlarge view



Page | 6.5

Figure 6.1.2: Iso-Risk Contours for MS Auto Blending unit – Overall



Page | 6.1

It is seen in the above figures that contour for 10-6 per year due to BS-VI Project does not extend beyond the refinery boundaries. As such, individual risk to members of the public is found to be in ‘Broadly Acceptable (Negligible Risk)’ level. The highest location-specific individual risk contour in BS-VI area is of 10-4 per year. The maximum LSIR in different areas are listed in Table 6.1.1.

Table 6.1.1: Maximum Location-Specific Individual Risk (LSIR) at BS-VI area

SR. NO.

AREA / UNIT MAXIMUM LSIR

(PER YEAR)





5. MS Auto Blending Unit area 1.50E-04



Page | 6.2

6.1.1 ALARP Summary & Comparison of Individual Risk with Acceptability Criteria

The Location Specific Risk (LSIR) i.e. risk to a person who is standing at that point 365 days a year and 24 hours a day. The people in plant are expected to work in 8 hour shift as well general shift. The actual risk to a person “Individual Specific Individual Risk” (ISIR) would be far less after accounting the time fraction a person spent at location.

ISIR Area = LSIR x (8/24)(8 hours shift) x (Time spend by an individual / 8 hours)

The comparison of maximum individual risk with the risk acceptability criteria is shown in Figure 4.1.

IndeselectG Unit area:

The maximum LSIR in this area is 6.0 x 10-4 per year. The personnel in this area work on 8 hour shift. During the shift, an individual person is expected to be present for about 2 hours on the average. The individual-specific individual risk (ISIR) is estimated as follows.

ISIR IndeselectG unit area = 6.0 x 10-4 x (8/24) x (2/8) = 5.00 x 10-5 per year

This is below the unacceptable individual risk criteria (10-3 per year) and falls in the ALARP region.

HGU Unit area:


ISIR HGU unit area = 5.0 x 10-4 x (8/24) x (2/8) = 4.16 x 10-5 per year


HDT Unit area:


ISIR HDT unit area = 4.4.0 x 10-4 x (8/24) x (2/8) = 3.66 x 10-5 per year


ISOM Unit area:


ISIR ISOM unit area = 4.20 x 10-4 x (8/24) x (2/8) = 3.50 x 10-5 per year




Page | 6.3

MS Auto Blending unit area:


ISIR IndeselectG unit area = 1.5 x 10-4 x (8/24) x (2/8) = 1.25 x 10-5 per year

This is below the unacceptable individual risk criteria (10-3 per year) and falls in the ALARP region. The maximum ISIR in the units are listed in Table 6.1.2.

Table 6.1.2: Maximum Individual-Specific Individual Risk (ISIR)

SR. NO.

AREA / UNIT MAXIMUM ISIR

(PER YEAR)





5. MS auto blender unit 1.25E-05

From the results shown above, the maximum individual risk to plant personnel is estimated as 5E-05 per year. This is below the unacceptable individual risk criteria (10-3 per year) and falls in the As Low As Reasonably Practical (ALARP) Region.



Page | 6.4

ALARP Summary & Comparison of Individual Risk with Acceptability Criteria

The objective of this QRA study is to assess the risk levels due to BS-VI project units with reference to the defined risk acceptability criteria and recommend measures to reduce the risk level to as low as reasonably practical (ALARP). The comparison of maximum individual risk with the risk acceptability criteria is shown in Figure 6.1.2. The individual risk to members of the public is in Broadly Acceptable region (Negligible Risk) The individual risk of 5.00 x 10-5 per year for plant personnel at BS-VI units is in the ALARP region.

Figure 6.1.2: Individual Risk

Max. Individual Risk to Worker: 5.00 E-05 per year

Max. Individual Risk to Public: < 1.0 E-06 per year

(Negligible Risk)



Page | 6.5

6.2 Societal Risk

The Societal Risk parameter for BS-VI Project is shown in Figures 6.4 in the form of an FN curve. The results of FN curves show that the risk is in “ALARP” region.

Figure 6.2.1: FN Curve for Group Risk at BS-VI project units



Page | 6.6

6.2.1 Top Risk Contributors (Group Risk)

The significant risk contributions from equipment in the BS-VI units based on results available from PHAST Risk are shown in Table 6.2.1.

Table 6.2.1: Top Risk Contributors


Contribution (%)

1 HDT Unit

1.1 Stripper Feed-Bottom Exchanger, Reactor Effluent-Stripper Feed Exchanger, Stripper

49-E-07, 49-E-08, 49-C-02

9.06

1.2 Backwash Surge Drum, Backwash Pump

49-V-21, 49-P-15A/B 3.30

1.3 Feed Filter, Feed Preheat Exchanger, Feed Surge Drum

49-G-01, 49-E-01, 49-V-02

2.08

1.4 Diesel / Kerosene Transfer Pump 49-P-01A/B 1.76

1.5 Feed Coalescer 49-V-01 1.67

1.6 Stripper overhead Pump 49-P-06A/B 1.67

2 HGU Unit

2.1 Naptha Feed Pump 48-P-01A/B 3.91

2.2 Low Temperature Shift Reactor, BFW Preheater-I, Demin Water Preheater

48-R-05, 48-E-06, 48-E-08

2.30

2.3 Cold Condensate Separator 48-V-08 2.29

2.4 Naptha Booster Pump 48-P-04A/B 2.16

2.5 Naptha Fuel Booster Pump 48-P-05A/B 2.11

3 IndeselectG unit

3.1 Feed Filter, Feed Coalescer 04-G-801A/B, 04-V-801

6.55

3.2 H2 Stripper, Stripper Feed Bottom Exchanger, Splitter Feed Cooler

04-C-801, 04-E-808, 04-E-807A/B

4.07



Page | 6.7


Contribution (%)

3.3 Feed/Reactor Effluent Exchanger, Reactor Feed Preheater, Electric Heater KOD, Electric Heater

04-E-809A/B, 04-E-802, 04-V-808, 04-EH-801

2.54

3.4 SDS Reactor 04-R-801 1.86

3.5 Feed Pump 04-P-801A/B 1.52

4 ISOM Unit

4.1 Deisopentaniser Reflux Drum 56-V-125 12.04

4.2 Deisopentaniser Column including reboiler-liquid side plus Deisopentaniser feed preheater

56-C-114, 56-E-129, 56-E-128

9.04

4.3 Deisopentaniser Bottom Pump including Deisopentaniser feed preheater

56-P-120A/B, 56-E-128

7.26

4.4 Deisopentaniser Overhead Pump including Deisopentaniser isomerate cooler

56-P-121A/B, 56-E-131

5.13



Page | 7.1

7. CONSEQUENCE ANALYSIS

7.1 Scenarios

The scenarios for consequence analysis have been identified as listed in Table 7.1.1.

Table 7.1.1: Scenarios

Case No.

Description Jet Fire

Pool Fire

Flash Fire

VCE

A HDT Revamp Unit

1. Diesel / Kerosene Transfer Pump -25 mm Leak

2. Feed Coalescer -25 mm Leak

3. Backwash Surge Drum, Backwash Pump -25 mm Leak

4. Feed Filter, Feed Preheat Exchanger, Feed Surge Drum -25 mm Leak

5. Charge Pump -25 mm Leak

6. Cold Combined Feed Exchanger, Hot Combined Feed Exchanger, Combined Feed Heater -25 mm Leak

7. Reactor 1 -25 mm Leak



10. Reactor Effluent Condenser, High Pressure Separator -25 mm Leak

11. Stripper Feed-Bottom Exchanger, Reactor Effluent-Stripper Feed Exchanger, Stripper -25 mm Leak

12. Stripper Bottom Pumps -25 mm Leak

13. Feed Preheat Exchanger, Product cooler, Product Coalescer pre filter, Product Coalescer -25 mm Leak

14. Caustic Wash Tower, Sand Filter, Salt Drier -25 mm Leak

15. Recycle gas Compressor KOD, Recycle Gas Compressor -25 mm Leak

16. First Stage Suction Drum, Second Stage Suction Drum, Makeup Gas Compressor -25 mm Leak



Page | 7.2

Case No.


Pool Fire

Flash Fire

VCE

17. Stripper Receiver -25 mm Leak

18. Stripper overhead Pump -25 mm Leak

19. Stripper Off gas KOD, NET gas Compressor, Net Gas KOD -25 mm Leak

B HGU Revamp

20. Naptha Booster Pump -25 mm Leak

21. Naptha Feed Surge Drum -25 mm Leak

22. Naptha Feed Pump -25 mm Leak

23. Feed Gas KOD -25 mm Leak -

24. Feed Gas Compressor, Discharge Dampener Vessel -25 mm Leak -

25. Feed Preheater / Vaporizer, Feed Preheater, Hydrogenerator -25 mm Leak -

26. Desulfuriser -25 mm Leak -

27. Pre-reformer Feed Preheater, Prereformer -25 mm Leak -

28. Reformer Feed Preheater, Reformer -25 mm Leak -

29. Technip Parallel Reformer -25 mm Leak -

30. Process Gas Boiler, High Temperature Shift Reactor, Steam Superheater, BFW Preheater-II -25 mm Leak -

31. Low Temperature Shift Reactor, BFW Preheater-I, Demin Water Preheater -25 mm Leak -

32. Hot Condensate Separator, Process Gas Air cooler, Process Gas Trim Cooler -25 mm Leak -

33. Cold Condensate Separator -25 mm Leak -

34. PSA Unit -25 mm Leak -

35. Naptha Fuel Booster Pump -25 mm Leak

36. Coker Naptha Fuel Surge Drum -25 mm Leak



Page | 7.3

Case No.


Pool Fire

Flash Fire

VCE

37. Coker Naptha Fuel Pump -25 mm Leak

C IndeselectG Unit

38. Feed Filter, Feed Coalescer -25 mm Leak

39. Feed Surge Drum -25 mm Leak

40. Feed Pump -25 mm Leak

41. Feed/Reactor Effluent Exchanger, Reactor Feed Preheater, Electric Heater KOD, Electric Heater -25 mm Leak

42. SDS Reactor -25 mm Leak

43. Separator Drum -25 mm Leak

44. Recycle Gas Compressor KOD -25 mm Leak

45. Recycle Gas Compressor discharge -25 mm Leak

46. H2 Stripper, Stripper Feed Bottom Exchanger, Splitter Feed Cooler -25 mm Leak

47. Stripper Reflux Drum -25 mm Leak

48. Stripper Reflux Pump -25 mm Leak

D ISOM Unit

49. Deisopentaniser Column including reboiler-liquid side plus Deisopentaniser feed preheater -25 mm Leak

50. Deisopentaniser Column vapour side -25 mm Leak

51. Deisopentaniser Reflux Drum -25 mm Leak

52. Deisopentaniser Overhead Pump including Deisopentaniser isomerate cooler -25 mm Leak

53. Deisopentaniser Bottom Pump including Deisopentaniser feed preheater -25 mm Leak



Page | 7.4

Consequence Analysis Results Results of the consequence analysis for the scenarios covered in this study are summarized in Table 7.1.2. The Consequence analysis Graph are placed in Attachment-III



Page | 7.1

Table 7.1.2 Consequence Analysis - Scenario Result

Case No.

Case Description

Wind speed & Pasquill stability

Flash fire distance

Jet fire Thermal radiation distances (m)

Pool fire Thermal radiation distances (m)

Overpressure distances (m)

(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5

kW/m2 0.5 psi 1 psi 3 psi 5 psi

1 Diesel / Kerosene Transfer Pump -25 mm Leak

3D - NR NR NR 44.62 23.05 NR - - - -

5D - NR NR NR 46.78 25.68 NR - - - -

2 Feed Coalescer -25 mm Leak

3D - NR NR NR 54.01 24.18 NR - - - -

5D - NR NR NR 58.26 25.76 NR - - - -

3 Backwash Surge Drum, Backwash Pump -25 mm Leak

3D - NR NR NR 57.58 25.34 NR - - - -

5D - NR NR NR 62.43 26.70 NR - - - -

4 Feed Filter, Feed Preheat Exchanger, Feed Surge Drum -25 mm Leak

3D - NR NR NR 65.98 28.79 NR - - - -

5D - NR NR NR 71.68 29.75 NR - - - -

5 Charge Pump -25 mm Leak

3D - NR NR NR 41.12 23.34 11.85 - - - -

5D - NR NR NR 42.63 26.40 13.13 - - - -

6

Cold Combined Feed Exchanger, Hot Combined Feed Exchanger, Combined Feed Heater -25 mm Leak

3D 40.97 35.57 19.89 14.22 NA NA NA 14.22 8.14 4.06 3.22

5D 38.45 35.42 19.66 14.72 NA NA NA 14.31 8.19 4.08 3.23



Page | 7.2

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


7 Reactor 1 -25 mm Leak 3D 47.31 42.3 23.86 17.17 NA NA NA 11.66 6.76 3.47 2.79

5D 77.83 42.18 24.34 18.60 NA NA NA 11.62 6.74 3.46 2.78


5D 73.32 40.40 23.43 17.92 NA NA NA 11.53 6.69 3.44 2.77


5D 70.90 39.19 22.81 17.46 NA NA NA 11.43 6.64 3.41 2.75

10 Reactor Effluent Condenser, High Pressure Separator -25 mm Leak

3D 6.68 NR NR NR 41.82 23.36 11.55 27.78 15.47 7.20 5.50

5D - NR NR NR 43.36 26.64 12.83 - - - -

11

Stripper Feed-Bottom Exchanger, Reactor Effluent-Stripper Feed Exchanger, Stripper -25 mm Leak

3D 88.42 42.16 24.33 17.20 54.10 23.84 NR 9.28 5.47 2.91 2.39

5D 70.25 41.99 24.12 16.12 57.56 25.40 NR 9.29 5.48 2.92 2.39

12 Stripper Bottom Pumps -25 mm Leak

3D 91.55 43.37 25.02 17.53 22.81 15.70 9.72 9.03 5.34 2.86 2.34

5D 75.38 43.24 24.84 16.40 22.87 16.55 11.48 9.02 5.33 2.85 2.34

13 Feed Preheat Exchanger, Product cooler, Product 3D - NR NR NR 56.90 24.64 NR - - - -



Page | 7.3

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


Coalescer pre filter, Product Coalescer -25 mm Leak

5D - NR NR NR 61.81 26.14 NR - - - -

14 Caustic Wash Tower, Sand Filter, Salt Drier -25 mm Leak

3D - NR NR NR 87.19 38.04 NR - - - -

5D - NR NR NR 93.14 37.66 NR - - - -

15 Recycle gas Compressor KOD, Recycle Gas Compressor -25 mm Leak

3D 25 28.50 16.62 12.20 NA NA NA 25.74 14.37 6.73 5.15

5D 23.27 27.83 17.11 13.57 NA NA NA 25.96 14.49 6.78 5.19

16

First Stage Suction Drum, Second Stage Suction Drum, Makeup Gas Compressor -25 mm Leak

3D 12.78 10.01 6.84 3.87 NA NA NA 17.93 10.15 4.92 3.84

5D 11.57 9.54 6.56 2.22 NA NA NA 17.90 10.13 4.91 3.84

17 Stripper Receiver -25 mm Leak

3D - NR NR NR 40.56 23.46 11.38 - - - -

5D - NR NR NR 42.03 26.75 12.63 - - - -

18 Stripper overhead Pump -25 mm Leak

3D - NR NR NR 41.34 23.40 11.65 - - - -

5D - NR NR NR 42.76 26.58 12.89 - - - -

19

Stripper Off gas KOD, NET gas Compressor, Net Gas KOD -25 mm Leak

3D 12.17 8.91 6.07 3.05 NA NA NA 17.24 9.78 4.76 3.72

5D 11.00 8.55 5.60 1.07 NA NA NA 17.18 9.74 4.75 3.72



Page | 7.4

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


20 Naptha Booster Pump -25 mm Leak

3D 0.22 NR NR NR 19.17 13.29 9.35 - - - -

5D 0.16 NR NR NR 19.04 14.10 11.21 - - - -

21 Naptha Feed Surge Drum -25 mm Leak

3D 0.38 NR NR NR 41.83 23.36 11.56 - - - -

5D - NR NR NR 43.35 26.64 12.83 - - - -

22 Naptha Feed Pump -25 mm Leak

3D - NR NR NR 21.96 15.15 9.59 - - - -

5D - NR NR NR 22.04 16.04 11.45 - - - -

23 Feed Gas KOD -25 mm Leak

3D 14.37 9.84 6.01 3.10 NA NA NA 8.94 5.29 2.84 2.33

5D 10.63 9.51 5.84 2.56 NA NA NA 8.97 5.31 2.84 2.34

24 Feed Gas Compressor, Discharge Dampener Vessel -25 mm Leak

3D 23.80 16.71 9.91 7.28 NA NA NA 10.36 6.06 3.17 2.57

5D 19.70 16.39 10.03 7.36 NA NA NA 10.40 6.08 3.18 2.58

25

Feed Preheater / Vaporizer, Feed Preheater, Hydrogenerator -25 mm Leak

3D 21.32 19.47 9.52 NR NA NA NA 10.66 6.22 3.23 2.62

5D 17.53 19.28 9.77 NR NA NA NA 10.68 6.23 3.24 2.63

26 Desulfuriser -25 mm Leak 3D 21.19 19.37 9.46 NR NA NA NA 10.65 6.22 3.23 2.62



Page | 7.5

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


5D 17.44 19.18 9.70 NR NA NA NA 10.68 6.23 3.24 2.62

27 Pre-reformer Feed Preheater, Prereformer -25 mm Leak

3D 17.60 17.80 9.84 7.19 NA NA NA 11.04 6.42 3.33 2.68

5D 15.78 17.47 9.84 7.19 NA NA NA 11.13 6.47 3.34 2.70

28 Reformer Feed Preheater, Reformer -25 mm Leak

3D 18.36 17.05 9.40 5.98 NA NA NA 13.71 7.86 3.94 3.13

5D 18.30 16.81 9.19 5.85 NA NA NA 13.85 7.95 3.97 3.16

29 Technip Parallel Reformer -25 mm Leak

3D 20.65 18.06 9.99 6.43 NA NA NA 13.58 7.79 3.91 3.11

5D 21.29 17.84 9.80 6.36 NA NA NA 13.71 7.87 3.94 3.13

30

Process Gas Boiler, High Temperature Shift Reactor, Steam Superheater, BFW Preheater-II -25 mm Leak

3D 24.63 15.63 7.67 NR NA NA NA 14.97 8.55 4.23 3.34

5D 22.15 15.55 7.60 NR NA NA NA 14.97 8.55 4.23 3.34

31

Low Temperature Shift Reactor, BFW Preheater-I, Demin Water Preheater -25 mm Leak

3D 28.68 16.55 8.24 NR NA NA NA 14.96 8.54 4.23 3.34

5D 25..14 16.51 8.19 NR NA NA NA 14.95 8.54 4.23 3.34

32

Hot Condensate Separator, Process Gas Air cooler, Process Gas Trim Cooler -25 mm Leak

3D 32.26 17.01 8.53 NR NA NA NA 14.66 8.38 4.16 3.29

5D 27.63 16.99 8.49 NR NA NA NA 14.66 8.38 4.16 3.29



Page | 7.6

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


33 Cold Condensate Separator -25 mm Leak

3D 38.28 18.43 9.41 2.24 NA NA NA 12.93 7.45 3.76 3.00

5D 29.46 18.38 9.34 2.43 NA NA NA 12.93 7.44 3.76 3.00

34 PSA Unit -25 mm Leak 3D 40.49 19.31 10.73 6.96 NA NA NA 13.10 7.54 3.80 3.03

5D 41.65 19.15 10.55 6.97 NA NA NA 13.17 7.57 3.82 3.04

35 Naptha Fuel Booster Pump -25 mm Leak

3D 0.08 NR NR NR 17.86 12.52 9.26 - - - -

5D 0.05 NR NR NR 17.60 13.13 10.72 - - - -

36 Coker Naptha Fuel Surge Drum -25 mm Leak

3D - NR NR NR 46.99 23.02 NR - - - -

5D - NR NR NR 49.45 25.63 NR - - - -

37 Coker Naptha Fuel Pump -25 mm Leak

3D 0.19 NR NR NR 14.58 10.51 8.39 - - - -

5D 0.13 NR NR NR 14.06 10.61 9.07 - - - -

38 Feed Filter, Feed Coalescer -25 mm Leak

3D 36.20 25.57 14.90 10.29 36.11 23.11 10.14 8.06 4.81 2.63 2.18

5D 31.16 25.49 14.55 9.77 37.46 25.79 11.27 7.90 4.73 2.60 2.16

39 Feed Surge Drum -25 mm Leak 3D 36.20 25.57 14.90 10.29 36.11 23.11 10.14 8.06 4.81 2.63 2.18



Page | 7.7

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


5D 31.16 25.49 14.55 9.77 37.46 25.79 11.27 7.90 4.73 2.60 2.16

40 Feed Pump -25 mm Leak 3D 36.20 25.57 14.90 10.29 36.11 23.11 10.14 8.06 4.81 2.63 2.18

5D 31.16 25.49 14.55 9.77 37.46 25.79 11.27 7.90 4.73 2.60 2.16

41

Feed/Reactor Effluent Exchanger, Reactor Feed Preheater, Electric Heater KOD, Electric Heater -25 mm Leak

3D 36.20 25.57 14.90 10.29 36.11 23.11 10.14 8.06 4.81 2.63 2.18

5D 31.16 25.49 14.55 9.77 37.46 25.79 11.27 7.90 4.73 2.60 2.16

42 SDS Reactor -25 mm Leak

3D 36.20 25.57 14.90 10.29 36.11 23.11 10.14 8.06 4.81 2.63 2.18

5D 31.16 25.49 14.55 9.77 37.46 25.79 11.27 7.90 4.73 2.60 2.16

43 Separator Drum -25 mm Leak

3D 36.20 25.57 14.90 10.29 36.11 23.11 10.14 8.06 4.81 2.63 2.18

5D 31.16 25.49 14.55 9.77 37.46 25.79 11.27 7.90 4.73 2.60 2.16

44 Recycle Gas Compressor KOD -25 mm Leak

3D 3.16 NR NR NR NA NA NA 7.48 4.50 2.50 2.09

5D 2.71 NR NR NR NA NA NA 7.09 4.26 2.41 2.02

45 Recycle Gas Compressor discharge -25 mm Leak

3D 5.05 NR NR NR NA NA NA 10.22 5.98 3.13 2.55

5D 4.35 NR NR NR NA NA NA 9.93 5.82 3.07 2.50



Page | 7.8

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


46

H2 Stripper, Stripper Feed Bottom Exchanger, Splitter Feed Cooler -25 mm Leak

3D 47.77 24.82 13.34 5.84 31.56 21.06 10.11 7.43 4.48 2.49 2.08

5D 40.84 24.76 13.31 5.99 32.31 22.73 11.59 7.34 4.43 2.47 2.06

47 Stripper Reflux Drum -25 mm Leak

3D 2.68 NR NR NR 41.56 23.46 11.41 16.35 9.29 4.55 3.57

5D - NR NR NR 42.88 26.81 12.61 - - - -

48 Stripper Reflux Pump -25 mm Leak

3D 0.008 NR NR NR 11.82 8.65 7.22 - - - -

5D 0.004 NR NR NR 10.20 7.68 7.22 - - - -

49

Deisopentaniser Column including reboiler-liquid side plus Deisopentaniser feed preheater -25 mm Leak

3D 38.45 22.60 12.74 8.18 34.77 22.63 10.15 7.28 4.39 2.45 2.05

5D 33.85 22.50 12.72 7.84 35.98 25.00 11.42 7.14 4.31 2.42 2.03

50 Deisopentaniser Column vapour side -25 mm Leak

3D 11.30 NR NR NR NA NA NA 7.31 4.41 2.46 2.06

5D 9.39 NR NR NR NA NA NA 7.29 4.40 2.46 2.05

51 Deisopentaniser Reflux Drum -25 mm Leak

3D 45.70 28.55 15.13 5.22 41.07 23.21 10.51 10.78 6.29 3.26 2.64

5D 38.34 28.53 15.08 5.64 42.59 26.72 11.77 10.75 6.27 3.26 2.64

52 Deisopentaniser Overhead Pump 3D 46.49 28.41 16.23 11.74 41.07 23.21 10.50 10.29 6.02 3.15 2.56



Page | 7.9

Case No.

Case Description


Flash fire distance




(m) 4

kW/m2 12.5

kW/m2 37.5

kW/m2 4

kW/m212.5

kW/m237.5


including Deisopentaniser isomerate cooler -25 mm Leak

5D 39.28 28.30 16.20 11.11 42.59 26.72 11.77 10.27 6.00 3.14 2.55

53

Deisopentaniser Bottom Pump including Deisopentaniser feed preheater -25 mm Leak

3D 37.01 20.25 11.34 6.94 32.03 21.29 10.13 7.05 4.26 2.40 2.01

5D 32.78 20.17 11.34 6.68 32.78 23.06 11.55 6.89 4.18 2.36 1.99



Page | 8.1

8. CONCLUSIONS & RECOMMENDATIONS

The maximum risk to persons working in the BS-VI units area is 5.00 x 10-5 per year which is in ALARP level (refer Yellow band in risk acceptability criteria). The risk to Public is in due to the proposed BS-VI project is in “Broadly Acceptable level”. Societal risk is also in “ALARP Level”. The following recommendations are made to keep the risk level in broadly acceptable level.

8.1 Recommendations

1. It is necessary to provide extensive fire and gas detection system in the Units. Philosophy for

operation of fire and gas detection system to isolate the relevant sections should be clearly defined and the operating personnel should be trained for proper use of this safety system. Fire & Gas detection system normally covers (a) areas containing potential leak sources such as large number of flange joints, valves, pumps, etc. and (b) pressure vessels containing significant inventory of light hydrocarbons which are vulnerable to BLEVE/ fireball hazards.

2. It is recommended to have necessary provision for emergency stop of all major transfer pumps

from control room in the event of major leak / flash fire there should be an SOP established for clarity of actions to be taken in case of fire / leak emergency. The details of Pumps are as follows:

Charge Pump (49-P-03A/B), Stripper Bottom Pumps (49-P-05A/B) in DHT Unit, Naptha Booster Pump (48-P-04A/B), Naptha Feed Pump (48-P-01A/B) in HGU unit, Feed Pump (04-P-801A/B) in IndeselectG Unit and Deisopentaniser Bottom Pump (56-P-120A/B) in ISOM unit.

3. The emergency response plan of the refinery to be updated to cover the BS-VI units.

Attachment – I Assumption Sheets

GUWAHATI REFINERY – QUANTITATIVE RISK ASSESSMENT

Document Number IRCA-IOCL-QRA-20171808-01 Rev 1 Aug 2018

Page 1 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-001 Subject: Study basis STUDY BASIS

Drawings and Documents The QRA study is based/or referenced on the following drawings/ Documents.

Sr. No Document / Drawing Document Drawing No.

1 Facilities Description Provided by IOCL

2 Process Flow Diagrams

For HDT Unit: 9019865-110-01-PFD to 12-PFD ; For HGU Revamp: 074221C001-PFD-0010-001 to 015 Rev-00 ; For indeselectG Unit: A964-04-0102 and 0103 Rev-00 ; For ISOM Unit: 56-5FD-2A Rev-01

3 Material Balance Provided by IOCL

4 Piping & Instrumentation Diagrams

For HDT unit: 9019865-120-01-PID to 36-PID Rev-01 ; For HGU : 74221C001-PID-0010-000 to 002 Rev-00, 074221C001-PID-0020-001 to 021 Rev-00, 074221C001-PID-0040-001 to 005 Rev-00 ; For indeselectG Unit: A964-04-1181 to 1192 REV 0 ; For ISOM unit: 1715-56-1192 to 94 Rev-0, 07-3040-056-14/17 Rev-7

5 Plot plan/ Equipment Layout

For HDT unit: 9019865-MISC-01 to 02 Rev 00 ; For HGU unit: 074221C001-DW-0051-002-06 & 074221C001-DW-0051-003-06 ; For indeselectG unit: 44AC270004L010001 Rev-0 ; For ISOM Unit: 44AC2700-56-L.01-0001-A1_A & 44AC2700-56-L.01-0002-A1_A

6 Layout Plan of Guwahati Refinery TS-00-150 Rev-19

Justification/ Comments: Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 2 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-002 Subject: Software tools SOFTWARE TOOLS Following software tools are used for this QRA

PHAST RISK - 6.7 (DNV Software, UK) for Onshore QRA Software

PHAST – 6.7 (DNV Software, UK) for Consequence analysis Justification/ Comments: IRCA has the current version PHAST 6.7 under AMC with DNV Software. Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 3 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-003 Subject: Generic Database for leak frequency and leak sizes LEAK FREQUENCY Following leak frequency database is used for this QRA

Risk Assessment Data Directory - Report No. 434 published by “International Association of Oil & Gas Producers” (OGP)

LEAK SIZE

Leak Type Representative hole Size (mm) Small leak 3

Medium leak 10

Large leak 50

Rupture 100

Justification/ Comments: The leak sizes considered for QRA are aligned with the leak sizes available in Risk Assessment Data Directory - Report No. 434 published by International Association of Oil & Gas Producers (OGP). The above leak sizes correspond to Pin hole leak, Flange leak, Large leak and Rupture. Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 4 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-004

Subject: Impact criteria for thermal radiation from jet fire/ pool fire & Impact criteria for explosion overpressure

THERMAL RADIATION CRITERIA

Event Description

Thermal radiation intensity

Effect

Jet fire / Pool fire 4 kW/m2 Heat instantly in areas where emergency actions lasting several minutes may be required by the personnel without shielding but appropriate clothing.

12.5 kW/m2 Significant chances of fatality for extended exposure. High chance of injury

37.5 kW/m2 Significant chances of fatality for people exposed instantaneously.

Flash fire LFL concentration Fatal for the people in the flammable cloud path.

EXPLOSION ANALYSIS CRITERIA

Event Description

Overpressure value Effect

Explosion overpressure

0.5 psi Breakage of glass windows 1 psi Wall damage. 3 psi Cladding & walls damaged, but building

frame stands. 5 psi Major damage and possible collapse.

TOXIC EXPOSURE CRITERIA The probability of death at toxic levels greater than the Toxic Damage Threshold (TDT) is assumed to be 1.0. The probability at toxic level less than the TDT is assumed to be 0. Justification/ Comments: Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 5 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-005

Subject: Release rate, Release orientation and Elevation of release

RELEASE RATE Release rate for various releases will be calculated by the software based on the process data and leak size input. RELEASE ORIENTATION For liquid release orientation will be down impinging on ground and for gas it will be horizontal ELEVATION OF RELEASE As applicable (will be taken from vessel elevation drawing) Justification/ Comments: Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 6 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-006 Subject: Ignition sources & ignition probability IGNITION SOURCES The following ignition sources will be defined from site plan

1. Points such as fired heaters 2. Areas such as electrical substations/ transformers 3. Electrical lines such as HT overhead lines) 4. Transportation lines such as roads, railway lines

IMMEDIATE IGNITION PROBABILITY When modeling in PHAST, the probability of immediate ignition will be specified as “Use Event Trees”. Justification/ Comments: Ignition sources will be strictly controlled in the refinery. As the specific sources of ignition in the site plan, flammable effects will be realistically modelled by using event trees in PHAST. Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 7 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-007 Subject: Ignition Probabilities for QRA IGNITION PROBABILITIES FOR HYDROCARBON RELEASES TO BE USED IN QRA

Release rate (kg/s)

Ignition Probability LPG, Propane, Propylene,

Hydrogen etc. Naphtha/ Gasoline Storage Diesel/ Kerosene/ Fuel Oil/ Crude Storage

Release of flammable gas, vapour or liquid significantly above normal boiling point

in large outdoor plants

Release of flammable liquid not having significant flash fraction if released in large

outdoor tank farm

Release of combustible liquid at ambient conditions (e.g. diesel, fuel oil) in large

outdoor tank farm & low pressure transfer system

1 0.0025 0.0020 0.0010 5 0.0125 0.0030 0.0010 10 0.0250 0.0040 0.0020 20 0.0500 0.0070 0.0030 50 0.1250 0.0200 0.0030

100 0.2500 0.0300 0.0030 200 0.5000 0.0500 0.0030

The ignition probabilities listed in Table above are total ignition probabilities, which can be considered as sum of probabilities of immediate ignition and delayed ignition. The probability of immediate ignition included in the above data is 0.001. For release in process units, probability of immediate ignition is considered as 0.01 based on the value specified in DNV Phast software. Event tree model option will be selected in Phast software with the definition of ignition sources in the plant layout. Justification/ Comments: The ignition probabilities listed are taken from the following Data sheets available in the Report No. 434-6.1 dated March 2010 titled “Ignition Probabilities” published by International Association of Oil & Gas Producers (OGP).

Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative



Page 8 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-008 Subject: Risk Criteria RISK CRITERIA

Individual Risk Criteria The tolerability criteria for Individual Risk for use in QRA are proposed as follows:

1. Boundary between tolerable risk and unacceptable risk for members of the public: 1.0E-04 per year

2. Boundary between tolerable risk and unacceptable risk for workers: 1.0E-3 per year

3. Boundary between broadly acceptable risk and tolerable risk for members of public: 1.0E-06 per year

4. Boundary between broadly acceptable risk and tolerable risk for workers : 1.0E-05 per year

The criteria for individual risk are shown in the following diagram.

(Negligible Risk)



Page 9 of 12

RISK CRITERIA

Societal Risk Criteria The tolerability criteria for Societal Risk for use in QRA are proposed as :

Justification/ Comments: The proposed criteria for individual risk and societal risk are those specified by UK Health & Safety Executive (UK-HSE) in their following documents:

Reducing Risks, Protecting People – HSE’s decision-making process (known as R2P2 document) – Please refer to paragraphs 130, 132 and 136.

Guidance on ALARP decisions in control of major accident hazards (SPC/Permissioning/12) - Please refer to paragraphs 18, 19, 35 and 36.

According to UK-HSE guideline available in the above documents, the upper boundary between Unacceptable and ALARP region passes through the point represented by N = 50 and F = 2.0E-04, and has slope of (-)1. The lower boundary between ALARP and Broadly Acceptable region is 2 orders of magnitude below the upper boundary. Approvals CONTRACTOR Representative R. Krishnan, Principal Engineer, IRCA OWNER Representative

(Negligible Risk)

(Negligible Risk)



Page 10 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-009 Subject: Weather/ Meteorological Data for QRA

WEATHER AND WIND ROSE DATA FOR GUWAHATI REFINERY TO BE USED IN QRA

Wind speed Stability

Class

Temp RH Wind Direction (From)

(m/s) C % N NNE NE ENE E ESE SE SSE S SSW SW WSW W WNW NW NNW

1.5 D 30 80 0.04 0.03 0.12 0.02 0.03 0.00 0.00 0.00 0.03 0.03 0.02 0.01 0.04 0.01 0.03 0.01

3 D 30 80 0.01 0.02 0.09 0.02 0.01 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.03 0.01 0.01 0.00

Total 0.05 0.05 0.21 0.04 0.04 0.00 0.00 0.00 0.04 0.04 0.03 0.01 0.07 0.02 0.04 0.01

Justification/ Comments:




Page 11 of 12

QRA ASSUMPTION SHEET Project No: 20171808 Project Title: Guwahati Refinery – BS-VI Project Assumption No: QRA-010 Subject: Population The data for distribution of people in the plant area have been provided by IOCL. The population distribution considered for BS-VI Project is as follows: AA) Population in and around HDT Unit

S. No. Description No. of Persons

Day Night 1. Shift-in-Charge 2 1 2. Panel Operator 2 1 3. Field Operator 4 2 4. General Shift Officer 2 0

BB) Population in and around HGU Unit



CC) Population in and around INDESELECT-G Unit



DD) Population in and around DEISOPENTANISER Unit





Page 12 of 12

Outside Unit Population


Day Night 1. Substation Building North side of HDT

unit 2 2

2. Control Room North side of HDT unit 100 20 3. Operator Room east side of HGU unit 30 8 4. New operator room east side of HGU

unit 30 8

5. Proposed substation for INDESELECTG Unit

2 2

6. Fire station near proposed substation for INDESELECTG Unit

24 9

7. Old control room north side of INDESELECTG Unit

9 9

8. Contractor Shed north west side of deisopentaniser unit

0 0

9. Maintenance building west side of INDESELECTG Unit

14 0

10. Project CELL office west side of INDESELECTG Unit

0 0

11. Operator around tanks (T-23 /29) 0 0 12. Operator around tanks (T-2/4) 0 0

Justification/ Comments:


Attachment – II

Failure Cases Input to QRA

HDT Revamp:-

Section No.

Section Name Section Description Phase Pressure kg/cm2 g

Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

1 Diesel / Kerosene Transfer Pump

49-P-01A/B Liquid 4.0 40 1.30E-03 3.87E-04 7.42E-05 1.50E-05

2 Feed Coalescer 49-V-01 Liquid 4.0 40 8.88E-04 3.13E-04 7.83E-05 1.00E-05

3 Backwash Surge Drum, Backwash Pump

49-V-21, 49-P-15A/B Liquid 4.0 40 1.76E-03 5.70E-04 1.22E-04 2.50E-05

4 Feed Filter, Feed Preheat Exchanger, Feed Surge Drum

49-G-01, 49-E-01, 49-V-02

Liquid 4.0 65 1.13E-03 4.05E-04 9.31E-05 3.05E-05

5 Charge Pump 49-P-03A/B Liquid 119.8 73 1.63E-03 4.96E-04 1.15E-04 1.50E-05

6

Cold Combined Feed Exchanger, Hot Combined Feed Exchanger, Combined Feed Heater

49-E-02, 49-E-03, 49-F-01 Liquid+V

apour 108 300 1.93E-03 6.90E-04 1.36E-04 6.12E-05

7 Reactor 1 49-R-01 Liquid 99.1 346 7.34E-04 2.81E-04 6.33E-05 8.50E-06



10 Reactor Effluent Condenser, High Pressure Separator

49-AC-01, 49-V-04 Liquid 87.1 60 6.21E-04 2.19E-04 7.34E-05 1.70E-06

11

Stripper Feed-Bottom Exchanger, Reactor Effluent-Stripper Feed Exchanger, Stripper

49-E-07, 49-E-08, 49-C-02

Liquid 7.6 231 1.45E-03 5.03E-04 1.06E-04 2.74E-05

12 Stripper Bottom Pumps 49-P-05A/B Liquid 10.5 224 1.36E-03 4.04E-04 7.92E-05 1.50E-05

13

Feed Preheat Exchanger, Product cooler, Product Coalescer pre filter, Product Coalescer

49-E-01, 49-E-01, 49-V-06

Liquid 8.1 40 1.76E-03 6.86E-04 1.83E-04 7.80E-05

14 Caustic Wash Tower, Sand Filter, Salt Drier

49-V-07, 49-V-08, 49-V-15

Liquid 8.1 40 1.57E-03 6.15E-04 2.43E-04 6.83E-05

15 Recycle gas Compressor KOD, Recycle Gas Compressor

49-C-01, 49-K-01A/B Vapour 110.1 92 1.06E-03 2.50E-04 2.85E-05 1.10E-05

16 First Stage Suction Drum, 49-V-05, 49-V-16, 49-K- Vapour 87.9 124 1.53E-03 4.00E-04 7.00E-05 2.50E-06

Section No.


Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

Second Stage Suction Drum, Makeup Gas Compressor

03A/B

17 Stripper Receiver 49-V-09 Liquid 5.5 38 1.13E-03 4.83E-04 1.61E-04 4.90E-05

18 Stripper overhead Pump 49-P-06A/B Liquid 14 45 1.45E-03 4.35E-04 8.32E-05 1.50E-05

19 Stripper Off gas KOD, NET gas Compressor, Net Gas KOD

49-V-17, 49-K-02A/B, 49-V-14

Vapour 16.7 116 1.11E-03 2.65E-04 4.00E-05 2.50E-06

HGU Revamp:-

Section No.


Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

1 Naptha Booster Pump 48-P-04A/B Liquid 5.0 40 1.47E-03 4.84E-04 3.90E-05 -

2 Naptha Feed Surge Drum 48-V-02 Liquid 7.0 40 5.28E-04 2.46E-04 5.10E-05 2.10E-06

3 Naptha Feed Pump 48-P-01A/B Liquid 36.0 42 1.62E-03 5.58E-04 3.90E-05 -

4 Feed Gas KOD 48-V-01 Vapour 15.0 40 7.54E-04 2.75E-04 1.08E-04 8.10E-05

5 Feed Gas Compressor, Discharge Dampener Vessel

48-K-01A/B, 48-V-11 Vapour 36 86 1.48E-03 4.27E-04 1.18E-04 2.50E-06

6 Feed Preheater / Vaporizer, Feed Preheater, Hydrogenerator

48-E-02, 48-E-24, 48-R-01

Vapour 35.8 352 2.52E-03 9.84E-04 2.29E-04 6.60E-05

7 Desulfuriser 48-R-02A/B Vapour 35.7 355 1.34E-03 4.76E-04 1.44E-04 8.22E-05

8 Pre-reformer Feed Preheater, Prereformer

48-E-22, 48-R-03A/B Vapour 29.9 461 1.12E-03 4.53E-04 1.41E-04 3.64E-05

9 Reformer Feed Preheater, Reformer

48-E-21, 48-F-01 Vapour 28 620 1.98E-03 7.73E-04 1.42E-04 7.11E-05

10 Technip Parallel Reformer 48-R-06 Vapour 28.7 487 8.18E-04 3.55E-04 1.19E-04 3.30E-05

11

Process Gas Boiler, High Temperature Shift Reactor, Steam Superheater, BFW Preheater-II

48-E-04, 48-R-04, 48-E-05, 48-E-07

Vapour 23.9 419 2.33E-03 9.26E-04 1.85E-04 8.13E-05

12 Low Temperature Shift Reactor, BFW Preheater-I, Demin Water Preheater

48-R-05, 48-E-06, 48-E-08

Vapour 22.9 250 1.78E-03 7.12E-04 1.98E-04 9.92E-05

13 Hot Condensate Separator, Process Gas Air cooler, Process Gas Trim Cooler

48-V-07, 48-AC-01, 48-E-09

Vapour 21.3 140 1.63E-03 6.61E-04 1.47E-04 6.95E-05

14 Cold Condensate Separator 48-V-08 Vapour 21.3 40 1.08E-03 3.99E-04 9.24E-05 4.55E-05

15 PSA Unit 48-X-05 Vapour 21.3 40 1.83E-03 6.69E-04 1.57E-04 2.00E-05

16 Naptha Fuel Booster Pump 48-P-05A/B Liquid 0.1 40 1.71E-03 5.78E-04 3.90E-05 1.50E-05

17 Coker Naptha Fuel Surge Drum

48-V-10 Liquid 1.0 40 3.86E-04 1.78E-04 5.10E-05 1.52E-06

18 Coker Naptha Fuel Pump 48-P-03A/B Liquid 2.5 40 1.31E-03 4.23E-04 3.90E-05 1.50E-05

Section No.


Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

19 Natural Gas Booster Compressor discharge

48-K-06A/B Vapour 15 40 1.12E-03 3.05E-04 8.58E-05 2.50E-06

INDESELECT-G Unit:-

Section No.


Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

1 Feed Filter, Feed Coalescer 04-G-801A/B, 04-V-801 Liquid 5.50 106.6 1.65E-03 6.34E-04 1.44E-04 2.00E-05

2 Feed Surge Drum 04-V-802 Liquid 3.50 106.6 5.70E-04 2.16E-04 9.18E-05 1.06E-06

3 Feed Pump 04-P-801A/B Liquid 27.30 107.0 1.96E-03 6.04E-04 1.22E-04 1.50E-05

4

Feed/Reactor Effluent Exchanger, Reactor Feed Preheater, Electric Heater KOD, Electric Heater

04-E-809A/B, 04-E-802, 04-V-808, 04-EH-801

Liquid+ Vapour

22 178 3.06E-03 1.07E-03 2.36E-04 3.60E-05

5 SDS Reactor 04-R-801 Liquid+ Vapour

18 178 2.40E-03 9.27E-04 1.93E-04 7.30E-05

6 Separator Drum 04-V-803 Liquid 17 40 9.71E-04 3.89E-04 7.72E-05 1.31E-05

7 Recycle Gas Compressor KOD

04-V-804 Vapour 19.50 40 1.48E-03 6.32E-04 5.10E-05 2.10E-06

8 Recycle Gas Compressor discharge

04-K-801A/B Vapour 26.20 97.87 2.47E-03 8.31E-04 3.40E-05 1.45E-05

9 H2 Stripper, Stripper Feed Bottom Exchanger, Splitter Feed Cooler

04-C-801, 04-E-808, 04-E-807A/B

Liquid 7.8 150 2.57E-03 8.96E-04 2.23E-04 3.60E-05

10 Stripper Reflux Drum 04-V-805 Liquid 7 40 1.41E-03 5.62E-04 7.50E-05 1.20E-05

11 Stripper Reflux Pump 04-P-802A/B Liquid 7.5 40 1.44E-03 4.71E-04 3.90E-05 1.50E-05

DEISOPENTANISER Unit:-

Section No.


Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

1

Deisopentaniser Column including reboiler-liquid side plus Deisopentaniser feed preheater

56-C-114, 56-E-129, 56-E-128

Liquid 4.00 110 9.68E-04 3.36E-04 8.12E-05 1.12E-05

2 Deisopentaniser Column vapour side

56-C-114 Vapour 3.20 82 7.13E-04 2.57E-04 4.84E-05 9.40E-06

3 Deisopentaniser Reflux Drum

56-V-125 Liquid 2.60 55.00 8.49E-04 3.86E-04 1.30E-04 5.10E-05

4

Deisopentaniser Overhead Pump including Deisopentaniser isomerate cooler

56-P-121A/B, 56-E-131 Liquid 8.70 55.00 1.89E-03 6.13E-04 9.58E-05 2.70E-05

5

Deisopentaniser Bottom Pump including Deisopentaniser feed preheater

56-P-120A/B, 56-E-128 Liquid 8.40 119.4 2.39E-03 8.35E-04 1.67E-04 6.45E-05

MS Auto Blender Unit:-

Section No.


Temperature˚C

Inventory(m3)

Failure Frequency

3mm Leak

10mm Leak

50mm Leak

100 mm Leak

1 Each Manifold - Liquid 8.0 Ambient 1.13E-03 5.56E-04 1.86E-05 4.40E-05

There are 5 manifolds.