NSRP Refinery and Petrochemical Complex Project Coarse QRA Bidder 1. Prepared for Foster Wheeler Energy Ltd by ABS Consulting Ltd.

Transcription

1 NSRP Refinery and Petrochemical Complex Project Coarse QRA Bidder 1 Prepared for Foster Wheeler Energy Ltd by ABS Consulting Ltd. Report N o R01 February 2011

2 DOCUMENT APPROVAL SHEET Project N o : Report N o : R01 Report Title: NSRP Refinery and Petrochemical Complex Project Coarse QRA Bidder 1 Client: Foster Wheeler Energy Ltd Contact: Ken Smith ABS Consulting Limited This document and any information or descriptive matter set out herein is subject to copyright and/or design right ownership. All rights reserved. No part of this document, nor any information or descriptive matter within it, may be disclosed, loaned, reproduced, copied, photocopied, translated or reduced to any electronic medium or machine readable form or used for any purpose whatsoever without the written permission of the Company, except in accordance with established contract conditions pertaining to the production of this document ISSUE DATE PREPARED REVIEWED APPROVED 1 DRAFT 03/02/11 Matthew Hart (Project Engineer) Xin Hao (Project Engineer) Pradeep Prakash (Project Manager) 1 11/02/11 Matthew Hart (Project Engineer) Xin Hao (Project Engineer) Pradeep Prakash (Project Manager) 2 15/02/11 Matthew Hart (Project Engineer) Xin Hao (Project Engineer) Pradeep Prakash (Project Manager) 3 22/02/11 Matthew Hart (Project Engineer) Pradeep Prakash (Project Manager) Pradeep Prakash (Project Manager) 4 24/02/11 Matthew Hart (Project Engineer) Pradeep Prakash (Project Manager) Pradeep Prakash (Project Manager) Page 2 of 96

3 DOCUMENT REVISION HISTORY ISSUE DESCRIPTION Issue 1 DRAFT First Draft issue for client comment. Issue 1 Updated Jetty Area and incorporated client comments from DRAFT. Issue 2 Incorporated client comments from Issue 1 Issue 3 Incorporated client comments from Issue 2 Removed the future Jetty from the study. Page 3 of 96

4 EXECUTIVE SUMMARY ABS Consulting Ltd (ABSC) preformed a quantitative risk assessment QRA for the proposed NSRP refinery in Nghi Son, Vietnam for the FEED stage of the project for Foster Wheeler Energy Ltd (FWEL). The results of the study [14], in addition to the site buildings risks, were used to check the risks to the nearby villages and the adjacent road users. Based on those risks appropriate actions were recommended. Following on from previous work, the Client has now solicited definitive design proposals from various bidders. This study has assessed the risks to the site buildings for the new proposed layout from Bidder 1 by updating the previous study [14]. All the previous assumptions remain the same. The three stage process for BRA is aimed at providing a structured risk assessment such that the complexity of assessment is commensurate with the magnitude of the problem. Stage 1 is the occupancy filtering step. At this stage, buildings which are not occupied or are not significant for the safety of the operation are eliminated from the assessment. For stage II, worst credible consequences are simulated and the buildings which are unaffected by the modelled hazards or for which simple mitigations can be designed are eliminated. All the buildings which are occupied or functionally significant AND are affected by the postulated hazards are then taken to Stage III risk assessment process where not only the magnitude of the hazard but the frequency is taken into account to calculate the risks to building occupants. Where risks are higher than the accepted criteria, mitigations are considered to lower the risks to acceptable levels. Of the on site buildings, 48 were assessed in the Stage 1 preliminary building screening as being At Risk, due to their occupancy and functionality requirements. The building risk assessment concluded that all occupied buildings at this site are shown to have negligible Individual Risk (IR) due to explosion and fire. Detailed recommendations for the mitigations for each building considered within the assessment in Section 7.2 and are based on industry general practice. This risk assessment does not account to any mitigation that may already be in place such as local deluge or passive fire protection on vessels. In addition to the risk mitigations outlined, due attention should be paid to ensuring that a robust escape and evacuation plan is in place within the overall emergency preparedness for the site. The public risk was analysed on a societal risk perspective by the use of an F-N curve. Societal risk is a measure of the collective risk to which a certain population is subjected as a whole. It is usually depicted in form of a so-called FN curve, which shows the frequency (F), that a given number, N people or more (hence N+) will be exposed to lethal consequences. Based on the results of the study, it can be seen that there is the potential for thermal heat radiation to impact the adjacent road. Fire risk (BLEVE) is predicted to affect the neighboring villages. By inspecting the F-N curves presented previously, it can be seen that the risks to the villagers at the east side are unacceptable. Detailed recommendations for the mitigations for each building considered within the assessment in Section 8 and are based on industry general practice. This risk assessment does not account to any mitigation that may already be in place such as local deluge or passive fire protection on vessels. In addition to the risk mitigations outlined, due attention should be paid to ensuring that a robust escape and evacuation plan is in place within the overall emergency preparedness for the site. Page 4 of 96

5 It is recommended that relocation of the villages should be considered as one of the mitigation options. The risks to the adjacent road, south of the plant, should be mitigated by the use of a 500m barrier, and if possible traffic control measures. It should be noted that this QRA presents the hydrocarbon releases risk results only; occupational risk, non-hydrocarbon events (e.g. dropped objects etc), external events (e.g. structural failure due to extreme weather, fatigue etc), structural events (e.g. structural failures, etc), and Transportation accidents are excluded from the scope of this study. It is assumed that the plant and buildings at the site will be designed to withstand the appropriate seismic loading such that the hydrocarbon release frequencies are unaffected. In cases where the plant design takes seismic risk into account, it is usual practice to ignore the seismic considerations from the QRA. Page 5 of 96

6 ABSC ACPH ALARP ARU BLEVE BRA CAM CDU CMU DOM ERPG ESD FEED FWEL GOHDS HAZID HCDS HMU HVAC IR IRPA InAlk KEC KHDS LC LFL LPG LSIR NAC NSRP PHA P&ID PFD LIST OF ACRONYMS ABS Consulting Ltd Air Changes per Hour As Low As Reasonably Practicable Amine Regeneration Unit Boiling Liquid Expanding Vapour Explosion Building Risk Assessment Congested area Assessment Methodology Crude Distillation Unit Concrete Masonry Units Design, Operation, Maintenance Emergency Response Planning Guidelines Emergency Shutdown Front End Engineering and Design Foster Wheeler Energy Limited Gas Oil Hydrodesulphuriser Unit Hazard Identification Hydrogen Compression and Distribution System Hydrogen Manufacturing Unit Heating, Ventilation and Air Conditioning Individual Risk (or Incident Radiation) Individual Risk Per Annum Indirect Alkylation Units Kuwait Export Crude Kerosene Hydrodesulphuriser Unit Lethal Concentration Lower Flammable Limit Liquefied Petroleum Gas Location Specific Individual Risk Naphtha and Aromatics Complex Nghi Son Refinery and Petrochemical Preliminary Hazard Analysis Piping and Instrumentation Diagram Process Flow Diagram Page 6 of 96

7 PPU PRU QRA RHDS RFCC R2P2 SHU SRU SWS TGT UPS SCEs ppm VCE Polypropylene Unit Propylene Recovery Unit Quantitative Risk Assessment Residue Hydrodesulphuriser Unit Residue Fluid Catalytic Cracker Unit Reducing risks, protecting people Selective Hydrogenation Sulphur Recovery Unit Sour Water Stripper Units Tail Gas Treating Uninterrupted Power Supply Safety Critical Elements parts per million Vapour Cloud Explosion Page 7 of 96

8 CONTENTS Page Document Approval... 2 Revision Record... 3 Summary... 4 List of Acronyms... 6 Contents... 7 List of Tables... 9 List of Figures List of Appendices INTRODUCTION GENERAL METHODOLOGY DESCRIPTION OF FACILITY Plant Description Process Units Buildings STAGE 1 ASSESSMENT Screening Criterion Occupancy Screening Functionality Screening Stage One Results STAGE 2 ASSESSMENT (CONSEQUENCE ANALYSES) Explosion Analyses Credible Explosion Hazards CAM Assessment Review of Hazard Consequences Fire Analysis Credible Fire Hazards Boiling Liquid Expanding Vapour Explosion (BLEVE) Hazards Toxic Analysis Credible Toxic Hazards Review of Hazard Consequences Stage II Screening STAGE 3 ASSESSMENT (RISK ANALYSIS) Model Development Page 8 of 96

9 6.2 SHEPHERD Parameters Equipment Count and Leak Frequencies Design, Operation & Maintenance Factors Probability of Emergency Shutdown Building Performance Fire & Toxic Hazard Modelling Fatality Probabilities Ignition Probabilities Building Protection Features Fire Resistance of Buildings Boiling Liquid Expanding Vapour Explosion (BLEVE) Scenario Risk Acceptance Criteria Individual Risks Evaluation of Building Risks Explosion Risks Fire Risk RISK ASSESSMENT On Site Risk Off-site Risk Villages to the East of the site Road to the South of the site CONCLUSIONS & RECOMMENDATIONS Buildings at the site Off-site Population Villages to the East of the site Road to the South of the plant UNCERTAINTY IN QRA REFERENCES...96 List of Tables Table 1 Stage 1 Assessment Table 2 - Maximum Credible Explosion Hazard Table 3 - Maximum Credible Fire Hazard Table 4 Toxic Gas (H2S) Dispersion modelling results for the 150mm hole size Table 5 - Leak Frequencies used within the Process Blocks Table 6 - Definition of Shell building types used in SHEPHERD Page 9 of 96

10 Table 7 -Vulnerability dependence on damage thresholds Table 8 - Definition of damage categories Table 9- Fatality Probabilities from Exposure to Fires and Toxins Table 10 Immediate Ignition Probabilities Table 11 Delayed Ignition Probabilities Table 12 - Levels of Building Protection against Fire & Toxic Hazards Table 13 - Thermal Radiation Limits for Structures and Plant Table 14- Summary Explosion Damage for the 10-4 /yr Hazard Table 15 Frequency of 15kW/m 2 at buildings Table 16 - Summary Occupancy Risk Values Table 17 Overall Risk to Functionally Significant Buildings Table 18 Recommendations Table 19 Recommendations Functional Significant Buildings Table 20 Recommendations vulnerability List of Figures Figure 1 - Proposed Location [Image taken from Google Earth] Figure 2 NSRP Main Plant Plot Plan [6] Figure 3 NSRP Plant Plot Plan (Jetty area) [7] Figure 4 2 nd Stage Buildings Figure 5 Maximum Credible Overpressures Main Plant Figure 6 Maximum Credible Overpressures Jetty Area Figure 7 Maximum Potential Incident Radiation Flux Contours Main Plant Figure 8 Maximum Potential Incident Radiation Flux Contours Jetty Area Figure 9 BLEVE Fireballs Diameters Figure 10 ERPG Levels Figure 11 ERPG Contours for the SRU Figure 12 SHEPHERD Model Main Plant Figure 13 SHEPHERD model Jetty Area Figure 14 Building vulnerability by type Page 10 of 96

11 Figure 15 - Levels of Risk and ALARP Figure 16 Flammable Gas Frequency across the Main Plant Figure 17 Flammable Gas Frequency across the Jetty Area Figure 18 - Frequency of Overpressure Exceeding 100 mbar Main Plant Figure 19 - Frequency of Overpressure Exceeding 100 mbar Jetty Area Figure 20 - Frequency of Overpressure Exceeding 30 mbar Main Plant Figure 21 - Frequency of Overpressure Exceeding 30 mbar Jetty Area Figure 22 - Explosion Risk Plot for Building Type B2 Main Plant Figure 23 - Explosion Risk Plot for Building Type B2 Jetty Area Figure 24 - Explosion Risk Plot for Building Type B4 Main Plant Figure 25 - Explosion Risk Plot for Building Type B4 Jetty Area Figure 26 - Explosion Risk Plot for Building Type B5 Main Plant Figure 27 - Explosion Risk Plot for Building Type B5 Jetty Area Figure 28 - Cloud Fire Frequency Contour Plot Main Plant Figure 29 - Cloud Fire Frequency Contour Plot Jetty Area Figure 30 - Frequency Contour Plot for Heat Flux above 15kW/m 2 Main Plant Figure 31 - Frequency Contour Plot for Heat Flux above 15kW/m 2 Jetty Area Figure 32 BLEVE Risk Plot Figure 33 F-N Curve (Villagers only) Figure 34 Total Fire and Explosion Risk Contour Level Main Plant Figure 35 Total Fire and Explosion Risk Contour Level Jetty Area Figure 36 Proposed concrete wall and traffic warning/control Page 11 of 96

12 1 INTRODUCTION ABS Consulting Ltd (ABSC) preformed a coarse quantitative risk assessment (QRA) for the proposed NSRP refinery in Vietnam for the FEED stage of the project for Foster Wheeler Energy Ltd (FWEL). The results of the study [14], in addition to the site buildings risks, were used to check the risks to the nearby villages and the adjacent road users. Based on those risks appropriate actions were recommended. Following on from the earlier work, the Client has now solicited definitive design proposals from various bidders. This study assesses the risks to the site buildings, for the new proposed layout from Bidder 1 by updating the previous study [14], by incorporating the new information in the risk model. For this assessment all the previous assumptions about the process conditions, release frequencies, ignition probabilities, etc remains the same. The results of the revised risk assessment study are detailed within this report. Although unchanged from the previous study [14], for the sake of completeness the general methodology adopted for this study is described in Section 2. Section 3 provides a general description of the facility. Section 4 presents the results of the Stage 1 assessment. Section 5 deals with the Stage 2 consequence modelling with Stage 3 risk analysis being covered in Section 6. Section 7 presents the Risk Assessment, where the risks are compared to the risk acceptance criteria. Section 8 presents the conclusions and suggests suitable risk mitigation measures for accomplishing them or showing that the risks are As Low as Reasonably Practicable (ALARP). Finally, discussion on the QRA uncertainties is presented in Section 9. Page 12 of 96

13 2 GENERAL METHODOLOGY The methodology adopted for the BRA follows the recommendations of in the American Institute of Petroleum s Recommended Practice API RP 752 [1]. The assessment follows a three step process. The philosophy of the stepped approach is to perform as simple an analysis as is consistent with the hazards. For example if the building is not occupied or is not significant from the plant operation aspect then no further assessment is needed. If the building is occupied or is functionally significant then the next consideration is to check if the building is subject to a credible hazard and if simple mitigation is feasible to mitigate the effects. No further assessment is needed if the occupied or functionally significant building is not subject to a credible major hazard or the effects of the hazard can be mitigated in a cost effective manner. Where the building is occupied or functionally significant and is subject to a credible hazard which cannot be easily designed out or mitigated, a risk assessment is undertaken to check if the risks to the building occupants are acceptable or the frequency of significant damage to unoccupied but functionally significant building is reasonably low. Based on the risk assessment, cost effective and proportional mitigation options can be devised. The QRA has been performed based initially on the three steps of the BRA methodology that are summarized below: 1. Stage 1: A screening assessment based on building occupancy and its functional significance. Only buildings considered to be occupied or functionally significant are taken to the Stage II assessment. This is generally undertaken by the plant and confirmed by the consultant. 2. Stage 2: This phase involves analysis of worst credible consequences of the potential hazards to assess building vulnerability for explosions, fires, flammable and toxic gases. Only buildings considered to be vulnerable to the assessed hazards need to be taken to the 3 rd stage of assessment. 3. Stage 3: The 3 rd stage of assessment involves calculation of risk to the building occupants and where risks are high considers risk reduction measures. 4. In addition to the standard building risk assessment, the risks to the offsite population were also assessed using the societal risk criteria for which the F-N curves were generated. The tool used for the stage 2 consequence modelling was Shell FRED V 5.1 which is a suite of Fire, Release, Explosion and Dispersion models used to predict the consequences of the accidental or design release of product from process, storage, transport or distribution operations [3]. For the stage III risk assessment Shell SHEPHERD V2.1 was used. The Shell SHEPHERD Risk Tool forms a family of graphical risk integrators. The tool has been developed to carry out fit-forpurpose Quantified Risk Assessment (QRA) for a broad range of onshore industrial sites such as Refineries, Gas plants, Chemicals plants, LPG distribution sites, pipeline systems etc. SHEPHERD is used to systematically build up risk contributions starting from a release and working through ignition sources to the calculation of the effects of cloud fires, jet fires, toxic gas and explosions. Escalation to other parts of the plant via vessel failure through explosion over-pressure and/or flame engulfment is handled automatically. The input required includes the mass flow rate and dispersion distances to lower flammable limit in process blocks or point sources [4]. Page 13 of 96

14 3 DESCRIPTION OF FACILITY 3.1 Plant Description The NSRP Refinery and Petrochemical Project will process 200,000 BPSD of imported Kuwait Export Crude (KEC) oil. The fuels section of the refinery includes Residue Hydrodesulphurisation and Residue Catalytic Cracking as the main upgrading units. The refinery is integrated with petrochemical production. The Aromatics plant produces Paraxylene and Benzene. A key product from the Residue Cracker is Propylene which is used to produce Polypropylene product [5]. The products produced include the following: LPG Gasoline 92/ 95 RON Kerosene / Jet A-1 Diesel Premium and Regular Paraxylene / Benzene Polypropylene Sulphur The refinery is situated in Nghi Son, Tinh Gia District, Thanh Hoa Province, Vietnam (approx. 200 km south of Hanoi) - See Figure 1. Figure 1 - Proposed Location [Image taken from Google Earth] The NSRP Project includes all process units and associated utility, offsite and infrastructure facilities to support the refinery operation. Page 14 of 96

15 Complete utility facilities designed to meet the refinery s demands for cooling water, fuels, power, steam, water, instrument and plant air, inert gas, etc. Offsite facilities including tankage for feedstocks plus intermediate and final products as well as systems for import and export of feed and products. Other offsite facilities including flare, effluent treatment, firewater, interconnecting piping and pipelines, etc. Marine facilities include an SPM/ Crude import line and product loading jetties Process Units The complex will comprise the following licensed processing blocks: The following unit description were based on the Refinery Design basis overall [5] supplied by FWEL. Refinery Process Units Crude Distillation Unit (CDU) LPG Recovery Unit Saturated LPG Treater Unit Kerosene Hydrodesulphuriser Unit (KHDS) Gas Oil Hydrodesulphuriser Unit (GOHDS) Residue Hydrodesulphuriser Unit (RHDS) Residue Fluid Catalytic Cracker Unit (RFCC) Propylene Recovery Unit (PRU) RFCC LPG Treater Unit RFCC Light Gasoline Treater Unit Selective Hydrogenation (SHU) and Indirect Alkylation Units (InAlk) Hydrogen Manufacturing Unit (HMU) and Hydrogen Compression and Distribution System (HCDS) Sour Water Stripper Units (SWS) Amine Regeneration Unit (ARU) Sulphur Recovery Unit (SRU) and Tail Gas Treating (TGT) Petrochemical Process Units Naphtha and Aromatics Complex (NAC) Polypropylene Unit (PPU) Page 15 of 96

16 Offsite Systems Crude Oil Import, Storage and Pumping System Inter Unit Storage and Pumping System Product Component Storage and Pumping System Product Storage and Pumping System Slop Storage and Pumping System Product Truck Loading System Sulphur Forming and Storage Unit Utility Systems Demineralised water system, Raw water/potable systems Cooling water system, Steam Power generation system, Flue gas Desulphurisation, Plant air/instrument Air System, Nitrogen System Fuel Oil System Fuel Gas System Flushing oil system Chemical Supply Electricity and steam is generated at the Cogeneration plant Buildings In all 59 buildings have been identified on the plant layout (See Figure 2 and Figure 3). On the previous study [14] ABSC numbered these buildings consecutively from number 1 to number 66. To allow direct comparison this system has been retained. These buildings are tabulated in Table 1. Page 16 of 96

17 Figure 2 NSRP Main Plant Plot Plan [6] Page 17 of 96

18 Figure 3 NSRP Plant Plot Plan (Jetty area) [7] Page 18 of 96

19 4 STAGE 1 ASSESSMENT The scope of the Stage one assessment is to carry out a building screening exercise in order to eliminate buildings of no safety concern (unoccupied and not functionally significant) from the risk assessment process. The stage I screening has been completed by FWEL using the API 752 [1] criteria described below; 4.1 Screening Criterion Occupancy Screening For the purposes of occupancy screening a building is considered occupied if the building occupancy load is 300 or more man-hours per week or if during peak occupancy, 5 people or more are routinely expected in the building for at least one hour. If this criteria is exceeded the building is selected for second stage (Stage 2) analysis Functionality Screening A stage-two building evaluation is required if a building is functionally significant. A building is defined as functionally significant if either: People are expected to remain or take refuge in the building during an emergency. Possible reasons for people to remain in a building include a lack of suitable evacuation options or the need for occupants to perform emergency shutdown procedures. The building is required for emergency response, such as fire stations or clinics. The building is necessary for continued operation of plant units that may be able to continue to operate or may be unaffected by an incident in another area. This includes control buildings, process interface buildings (PIBs), or substations that control or provide power to multiple process units. The economic impact on operations of loss of buildings is significant. 4.2 Stage One Results A summary of the occupancy details is provided in Table 1 along with whether the building is functionally critical or required to provide shelter during an emergency. Previously the buildings were numbered 1 to 66. The building numbering system has been retained within this study to facilitate a direct comparison. However, please note that numbers 17, 29, 35, 47, 61, 63 and 64 have not been used as they were either missing on the plot plan [6] or have been revised. Twelve building are assessed as being occupied and thirty eight as functionally significant. Six buildings are both occupied and functionally significant. Eleven building have been screened out as being neither occupied nor functionally significant. The buildings taken to the second stage of this assessment are shown in Figure 4. Page 19 of 96

20 Table 1 Stage 1 Assessment Project Building Number Building Name Peak Occupancy Total Occupancy (hr/week) Functionally Significant 5 people or more routinely expected in the building for at least an hour? High Occupancy (>300 man-hours per week) Carry Forward For Stage 2 1 Administration Building Yes Yes Yes Yes 2 Canteen No Yes Yes Yes Yes 3 Medical Center Yes Yes Yes Yes 4 Main Guard House Yes Yes Yes Yes 5 Central Control Room Yes Yes Yes Yes 6 CCR Oil Movements 0 0 Yes No No No 7 Laboratory No Yes Yes Yes 8 Maintenance Workshop No Yes Yes Yes 9 Warehouse No Yes Yes Yes 10 Central Chemical Store No No No No 11 Central Catalyst Store No No No No Page 20 of 96

21 Project Building Number Building Name Peak Occupancy Total Occupancy (hr/week) Functionally Significant 5 people or more routinely expected in the building for at least an hour? High Occupancy (>300 man-hours per week) Carry Forward For Stage 2 12 Canteen No No Yes Yes Yes 13 Fire Station Yes No Yes Yes 14 Main Substation SS-M Yes No No Yes 15 Emergency Generator 0 0 Yes No No Yes 16 Truck Loading Office No No No No 18 SS- U Yes No No Yes 19 SS-O Yes No No Yes 20 SS- U Yes No No Yes 21 SS- P Yes No No Yes 22 SS- P Yes No No Yes 23 SS-P Yes No No Yes 24 SS-P Yes No No Yes Page 21 of 96

22 Project Building Number Building Name Peak Occupancy Total Occupancy (hr/week) Functionally Significant 5 people or more routinely expected in the building for at least an hour? High Occupancy (>300 man-hours per week) Carry Forward For Stage 2 25 SS- P Yes No No Yes 26 SS- P Yes No No Yes 27 SS- P Yes No No Yes 28 SS- P Yes No No Yes 30 SS-P Yes No No Yes 31 SS-U Yes No No Yes 32 SS-O Yes No No Yes 33 SS-U Yes No No Yes 34 SS-O Yes No No Yes 36 ISB Yes No No Yes 37 ISB Yes No No Yes 38 ISB Yes No No Yes Page 22 of 96

23 Project Building Number Building Name Peak Occupancy Total Occupancy (hr/week) Functionally Significant 5 people or more routinely expected in the building for at least an hour? High Occupancy (>300 man-hours per week) Carry Forward For Stage 2 39 ISB Yes No No Yes 40 ISB Yes No No Yes 41 ISB Yes No No Yes 42 ISB Yes No No Yes 43 ISB Yes No No Yes 44 ISB Yes No No Yes 45 ISB Yes No No Yes 46 ISB Yes No No Yes 48 ISB Yes No No Yes 49 ISB Yes No No Yes 50 ISB Yes No No Yes 51 ISB Yes No No Yes Page 23 of 96

24 Project Building Number Building Name Peak Occupancy Total Occupancy (hr/week) Functionally Significant 5 people or more routinely expected in the building for at least an hour? High Occupancy (>300 man-hours per week) Carry Forward For Stage 2 52 ISB Yes No No Yes 53 ISB Yes No No Yes 54 ISB Yes No No Yes 55 Local Guardhouse No No No No No 56 Jetty Area Guardhouse No No Yes Yes 57 Operator Shelter No1 0 0 No No No No 58 Operator Shelter No2 0 0 No No No No 59 Solid Product Warehouse 0 0 No No No No 60 Jetty Area Admin/Control Building Yes Yes Yes Yes 62 Jetty Area Workshop 0 0 No No No No 65 Jetty Area Storage Building 0 0 No No No No 66 Crude Oil Terminal Spares Warehouse 0 0 No No No No Page 24 of 96

25 Figure 4 2 nd Stage Buildings Page 25 of 96

26 5 STAGE 2 ASSESSMENT (CONSEQUENCE ANALYSES) 5.1 Explosion Analyses Credible Explosion Hazards The flammable gas accumulating in a congested region and subsequent delayed ignition results in an explosion. So for an explosion to occur there should be a source of flammable release near a congested area. Considering both the PFD and the plot plan, the following potential sources of explosion were identified for explosion consequence modeling. CDU LPG Recovery and Treater Unit KHDS GOHDS RHDS RFCC PPU SHU and Ind Alk HMU HCDS NAC Berth Area Tanks pumping system Fuel gas system CAM Assessment For the congested areas in the Aromatics Complex, RFCC Unit and Hydrogen Manufacturing plant, the parameters were derived using Shell s guidelines and based upon the plot plans provided. For the remaining units an engineering judgment was use to set this parameters as more detailed plot plants weren t available at the time of this assessment Review of Hazard Consequences The maximum credible overpressure and impulse for each building is provided in Table 2. Page 26 of 96

27 Table 2 - Maximum Credible Explosion Hazard Building Number Building Name Overpressure (psi) Impulse (psi-ms) 1 Administration Building Canteen No Medical Center Main Guard House Central Control Room Laboratory Maintenance Workshop Warehouse Canteen No Fire Station Main Substation Emergency Generator SS- U SS-O SS- U SS- P SS- P SS-P SS-P SS- P SS- P Page 27 of 96

28 Building Number Building Name Overpressure (psi) Impulse (psi-ms) 27 SS- P SS- P SS-P SS-U SS-O SS-U SS-O ISB ISB ISB ISB ISB ISB ISB ISB ISB ISB ISB ISB ISB ISB ISB Page 28 of 96

29 Building Number Building Name Overpressure (psi) Impulse (psi-ms) 52 ISB ISB ISB Jetty Area Guard House Jetty Area Admin/Control Building Figure 5 and Figure 6 shows the maximum credible overpressure values. Page 29 of 96

30 Figure 5 Maximum Credible Overpressures Main Plant Page 30 of 96

31 Figure 6 Maximum Credible Overpressures Jetty Area Page 31 of 96

32 5.2 Fire Analysis Credible Fire Hazards The following list summarises the main potential fire sources for fire consequence modeling: CDU LPG Recovery and Treater Unit KHDS GOHDS RHDS RFCC PPU SHU and Ind Alk HMU HCDS NAC Berth Area Storage Tanks and pumping system Spheres Propane loading Fuel Gas system Figure 7 and Figure 8 show the maximum potential incident radiation flux contours. Page 32 of 96

33 Figure 7 Maximum Potential Incident Radiation Flux Contours Main Plant Page 33 of 96

34 Figure 8 Maximum Potential Incident Radiation Flux Contours Jetty Area Page 34 of 96

35 5.2.2 Boiling Liquid Expanding Vapour Explosion (BLEVE) Hazards The potential BLEVE hazards identified are listed below. A consequence modeling has been undertaken for these BLEVE scenarios. Product storage (Spheres) LPG Loading True BLEVEs are associated with liquid gases such as propane which are stored as liquid by keeping them under pressure at temperatures far in excess of the boiling points of the material. For example the boiling point of propane is -42 o C. Being kept at an ambient temperature of 30 o C represents a very large temperature difference for this liquid. Therefore, an increase in the temperature for the liquid from a relatively small fire would tend to rapidly increase the pressure as the material tries to return to a gaseous state. The material could go into a superheated state, and, given the sudden loss of containment when the shell of the containing vessel fails due to the applied heat load and loss of strength, the superheated liquid would instantly vaporize causing a rapid expansion in volume (of the order of 100s of times the liquid volume) giving rise to the fireball that is inherent in the BLEVE event. The maximum fireball diameter contours are show in Figure 9. Page 35 of 96

36 Figure 9 BLEVE Fireballs Diameters Page 36 of 96

37 A summary of the Maximum Incident Radiation flux from the modeled fire scenarios for each building is given in Table 3. Table 3 - Maximum Credible Fire Hazard Building Number Building Name Max. Incident Radiation (kw/m 2 ) 1 Administration Building Negligible 2 Canteen No1 Negligible 3 Medical Center Negligible 4 Main Guard House Negligible 5 Central Control Room 4 7 Laboratory Negligible 8 Maintenance Workshop 4 9 Warehouse 4 12 Canteen No2 Negligible 13 Fire Station Negligible 14 Main Substation SS-M Emergency Generator SS- U SS-O04 Negligible 20 SS- U SS- P09 >50 22 SS- P07 >50 23 SS-P02 >50 24 SS-P06 >50 Page 37 of 96

38 Building Number Building Name Max. Incident Radiation (kw/m 2 ) 25 SS- P03 >50 26 SS- P04 >50 27 SS- P01 >50 28 SS- P08 >50 30 SS-P05 >50 31 SS-U SS-O03 >50 33 SS-U02 >50 34 SS-O ISB ISB-013 >50 38 ISB-03 >50 39 ISB-011 >50 40 ISB-06 >50 41 ISB-05 >50 42 ISB-04 >50 43 ISB-02 >50 44 ISB-12 >50 45 ISB-01 >50 46 ISB-10 >50 48 ISB-08 >50 Page 38 of 96

39 Building Number Building Name Max. Incident Radiation (kw/m 2 ) 49 ISB-07 >50 50 ISB-18 >50 51 ISB-17 >50 52 ISB ISB ISB-19 >50 56 Local Guardhouse Jetty Area Negligible 60 Jetty Area Admin/Control Building Toxic Analysis Credible Toxic Hazards The following list summarises the locations of potential sources for toxic gas release and thus included in consequence modeling: CDU SWS ARU SRU RFCC GOHDS KHDS RHDS Page 39 of 96

40 5.3.2 Review of Hazard Consequences The hazard distances for toxic H 2 S gas from maximum credible release scenarios were calculated for each of the three Emergency Response Planning Guide (ERPG) values and are provided in Table 4. Table 4 Toxic Gas (H2S) Dispersion modelling results for the 150mm hole size Downwind distance (m) ERPG1 ERPG2 ERPG3 Unit (0.1 ppm) (30 ppm) (100 ppm) D5 Weather F2 Weather D5 Weather F2 Weather D5 Weather F2 Weather SRU 086/087/ RFCC SWS GOHDS KHDS CDU ARU RHDS Note: The dispersion modeling was performed for two Pasquill-Gifford categories: D5: atmospheric stability class D with 5m/s wind speed. F2: atmospheric stability class F with 2m/s wind speed. The Emergency Response Planning Guidelines (ERPGs) are intended to be a planning tool to help anticipate human adverse health effects to the general public caused by toxic chemical exposure. The ERPGs are three-tiered guidelines, with a common denominator: 1 hour exposure duration. The levels are defined as follows in Figure 10: Page 40 of 96

41 Figure 10 ERPG Levels In this assessment the AIHA ERPG-2008 values were adopted to investigate the potential for off-site adverse effects to humans due to toxic H 2 S exposure [10]. ERPG-1: 0.1 ppm ERPG-2: 30 ppm ERPG-3: 100 ppm Figure 11 shows the ERPG-2 and 3 contours to the Amine Acid gas on the SRU unit considering a 150mm hole size release for D5 condition. Page 41 of 96

42 Figure 11 ERPG Contours for the SRU Page 42 of 96

43 5.4 Stage II Screening From the review of the credible hazards modeled, it is apparent that most of the buildings taken to stage II screening are subject to significant fire and /or explosion hazard. Conservatively therefore all the buildings considered in the stage II assessment have been retained for the Stage III risk assessment. 6 STAGE 3 ASSESSMENT (RISK ANALYSIS) 6.1 Model Development The SHEPHERD model was updated using the plot plans [6]. The mass and energy balance was used to define the process condition within each of the main plant items so that process specific fluid could be used in the consequence assessment. The plot plans and other documents were used to define the process areas for the QRA and also used to define the congested areas. A plot of the SHEPHERD model is given in Figure 12 and Figure 13. The offsite area to the west, South and East are termed areas A, B and C respectively. Page 43 of 96

44 Figure 12 SHEPHERD Model Main Plant Page 44 of 96

45 Figure 13 SHEPHERD model Jetty Area Page 45 of 96

46 6.2 SHEPHERD Parameters Equipment Count and Leak Frequencies The main plant items were identified and grouped depending on the fluid composition, with process pressure and process temperature in the same order of magnitude into process blocks, which were entered into the Shell SHEPHERD model. The model uses the Multiple Object as a single place holder for defining more than one process block in the model to reduce the number of physical objects drawn in the model. Using the generic parts count (e.g. vessels or compressors), a distribution of flanges and connections etc are applied internally within the SHEPHERD model based on a distribution defined by Shell. Each of the flanges, connections and fittings etc associated with a generic piece of equipment thus provides the leak source and associated frequency. The leak frequencies are generally based on the generic data from the Hydrocarbon Leak and Ignition Database, EP Forum Risk Assessment Data Directory, EP Forum Report No. 11.8/250, E&P Forum, (1996) [8]. The leak frequencies for the LPG filling station used are generally accepted on the onshore industry. A summary of the leak frequencies used is presented in Table 5 below. Table 5 - Leak Frequencies used within the Process Blocks Holes Size Leak Type Leak Frequency/ year Process LPG Process Blocks 10mm Flange Leak 1.5x mm Seal Leak (pump) 7x x mm Fitting Leak 2.35x mm 100mm Connection Leak Pipe Leak (*1/D) 3.8x x LPG Filling Station 10mm General E-01 25mm General E-04 50mm General E mm General E-02 Page 46 of 96

47 6.2.2 Design, Operation & Maintenance Factors The failure rate data applied in the study represents industry average values, although in order to take plant condition into account within the risk calculation, SHEPHERD allows for the effectiveness of prevention and shutdown measures to be taken into account. Factors including design, operation and maintenance (DOM) are considered. A DOM factor is used by SHEPHERD and is applied to account for the effectiveness of the prevention measures, categorised as high, average or low. In order to obtain a site-specific failure frequency, the average value is modified using the input DOM factor. In selecting a low effectiveness, the failure frequency is multiplied by the DOM factor and divided by the DOM factor for high effectiveness. Hence selecting the average does not change the failure frequency value. For the base case quantitative risk assessment, the effectiveness of the design, operation and maintenance was assumed to be average. Therefore, the industry average failure rate data was used Probability of Emergency Shutdown Inventory isolation time (response time) is assumed to be 20 minutes after start of a release except for the RFCC for which inventory isolation within 5 minutes with a 50% probability and isolation following fire detection with a probability of 80% is assumed. This assumption affects the only the escalation potential, all the releases are modelled Building Performance A number of studies have sought to generate guidance on building damage and collapse, and consequent fatality rates, for different categories of buildings. Some studies have considered both the overpressure and impulse resulting from the explosion, while others have only correlated the effects against the overpressure. Analytical tools have also been developed to assist with this analysis. The work reported here is based on the results of the 1995 Petroleum and Chemical Processing Industry Technology Co-operative report on Conventional Building Blast Performance Capabilities. API RP-752 [1] defines a set of building classifications included within Shell SHEPHERD Exceedance, given in Table 6 [4]. Table 6 - Definition of Shell building types used in SHEPHERD Shell Building Type Description B1 Wood, temporary buildings, trailers B2 Steel frame with metal siding B3 Brick/un-reinforced masonry (load bearing wall) B4 Steel or concrete frame with masonry fill or cladding B5 Blast resistant (reinforced concrete) B6 Brick/moderately reinforced masonry load bearing Page 47 of 96

48 Shell Building Description Type B7 Steel frame building with pre-cast walls and concrete roof B8 Custom type specify the design free-field overpressure at 100ms pulse duration Each building type has its own unique resistance to blast damage. The blast damage resistance of various building types is shown in Figure 14. Overpressure Versus Vulnerability Peak Incident Overpressure (psi) B1,B2 & B4 B5 B6 B Probability of Serious Injury/Fatality Figure 14 Building vulnerability by type The Co-Operative has also suggested a relationship between vulnerability and building damage level. These are given in Table 7. Page 48 of 96

49 Table 7 -Vulnerability dependence on damage thresholds Vulnerability Damage level interface /2A 0.1 2A/2B 0.3 2B/ / /5 The definition of blast damage levels from the Co-Operative study are given in Table 8. Table 8 - Definition of damage categories Discrete damage level Brief description Full description 1 Minor damage Onset of visible damage. Repairs are only needed for cosmetic reasons. Building is reusable following an explosion. 2A Moderate damage Localised building damage. Building performs function and can be used; however, major repairs are required to restore integrity of structural envelope. Total cost of repairs is moderate. 2B Moderate damage Widespread building damage. Building cannot be used until major repairs are completed. Total cost of repairs is significant, approaching replacement cost of building. 3 Major damage Building has lost structural integrity and may collapse due to environmental conditions (i.e. wind, snow, rain). Total cost of repairs exceeds replacement cost of building. 4 Collapse Building fails completely. Repair not feasible. Page 49 of 96

50 Discrete damage level Brief description Full description 5 Annihilation Occupant survival is not possible. 6.3 Fire & Toxic Hazard Modelling Within the SHEPHERD fire and toxic model a number of user defined probabilities are required which have an influence on the calculation of the individual risk contours. These are described in the following sections. As well as these requirements, the model also requires results from the consequence assessment e.g. mass flow rate, LFL distance and distance to 1% fatalities due to exposure to a toxic substance Fatality Probabilities The fatality probabilities used for a person located outside are listed in Table 9. Table 9- Fatality Probabilities from Exposure to Fires and Toxins Consequence Fatality Probability Flame engulfment (>50kW/m 2 ) 1 Thermal radiation (>10kW/m 2 ) 0.7 Toxic Gas Based on probit functions published in the TNO Purple Book (CPR18). H 2 S Probit = ln(C 1.9 t) where t is the exposure time in minutes set at 30 min and C is the calculated concentration in mg/m 3. It is highlighted that the fatality risk from exposure to the effects of fires and toxics will be different for people depending on the location of the person from the hazard and if they are inside or outside a building, due to the protection afforded by the building, i.e. lower hazard frequency within the building. For instance anyone outdoors caught within a flash fire (the LFL envelope) would be killed (i.e. fatality probability of 1), but if adequately protected from the flames indoors may not be Ignition Probabilities The immediate ignition probabilities adopted in this assessment were derived from Cox Lees and Ang Classification of Hazardous Locations [9] who have related the probability of ignition of release of flammable material and discharge rate. These probabilities are those given in Table 10. Page 50 of 96

51 Table 10 Immediate Ignition Probabilities Leak Rate (kg/s) Gas Probability of Ignition Liquid < > A site background ignition probability of 1E-4/m 2 of the facility was adopted for this assessment, in order to address the potential for delayed ignition with the fire modelling. For the offsite urban location a probability of ignition of 0.25E-4/m 2 as suggested by the UKHSE has been adopted. The additional ignition probability for the road to the south of the site is based on the traffic conditions assuming that a vehicle represents a probability of ignition of 0.1. For explosion modelling, the exceedance module has been used which requires a delayed ignition probability to be specified. The delayed ignition probability used for explosion modelling is given in Table 11. Table 11 Delayed Ignition Probabilities Leak Rate (kg/s) Gas Probability of Ignition Liquid < > Building Protection Features People located inside buildings will be protected to some extend from external hazards depending on the type of building construction. These building protection levels are used to modify the probability of fatality and are explained in Table 12. Page 51 of 96

52 Table 12 - Levels of Building Protection against Fire & Toxic Hazards Protection Description Level of protection used for all buildings Combustible Gas Protection (%) This is the effectiveness (%) of the protection provided against the ingress of combustible gas. 0% (Building Types B1) 50% (Building Types B2,B3,B4,B6+) 90% (Building Type B5) Flame Protection This is the effectiveness (%) of the protection provided against jet flame impingement. 0% (Building Types B1) 90% (Building Types B2,B3,B4,B6+) 90% (Building Type B5) Flux Protection This is the effectiveness (%) of the protection provided against thermal radiation. 0% (Building Types B1) 90% (Building Types B2,B3,B4,B6+) 90% (Building Type B5) Toxic Gas Protection To estimate the toxic gas concentration within a building the number of air changes per hour is required. This concentration is used in the probability equation to estimate the fatalities due to toxic gas exposure 0 ACPH (Building Types B1) 2 ACPH (Building Types B2,B3,B4,B6+) 2 ACPH (Building Type B5) Fire Resistance of Buildings Impairment of structural integrity is defined as loss of ability to support the buildings and facilities. This may be due to loss of stability or structural failure due to fire or explosion. Accordingly, loss of integrity within one hour of the following is considered: Structural integrity, including the supporting structure, Life support integrity, including prevention and mitigation of smoke and gas ingress, and Command support integrity. Page 52 of 96

53 Table 13 provides details of design limits for various types of structure and plant. Table 13 - Thermal Radiation Limits for Structures and Plant Thermal Radiation Intensity (kw/m 2 ) Thermal Limit 37.5 Intensity at which damage is caused to process equipment and tanks 25 Intensity at which non-piloted ignition of wood occurs Intensity at which cable insulation degrades 15.6 Intensity at which operators are unlikely to be performing and where shelter is unavailable. 14 Intensity which normal buildings should be design to withstand 12 Intensity at which plastics may begin to melt Boiling Liquid Expanding Vapour Explosion (BLEVE) Scenario The failure time for the pressurised liquid gas vessel such as product spheres from flame impingement resulting in a BLEVE was taken as 10 minutes, which is considered to be accepted practice within the industry. 6.4 Risk Acceptance Criteria The purpose of risk assessment is to aid decision making and in order to do this some form of criteria is required. In many cases risk assessment is used for comparative purposes or to identify areas or scenarios that present the greatest risk so that risk reduction can be carried out in a sensible and cost effective way. The use of risk assessment, however, must be performed with care, because of the uncertainties inherent in the assessment. Furthermore there is no clear consensus with respect to the values of tolerable or unacceptable risks, as this varies between organisations and countries. The parameter used as a measure of risk in this study is the Individual Risk (IR) Individual Risks Individual risks involve the definition of the following elements: An upper risk level, beyond which risks are deemed unacceptable; A lower risk level, below which risks are deemed not to warrant concern; and An intermediate region between the upper and lower levels where risk reduction measures are required to achieve a level deemed to be As Low As Reasonably Practicable (ALARP). The ALARP risk review process is illustrated in Figure 15. Page 53 of 96

54 UNACCEPTABLE REGION INTOLERABLE LEVEL (Risk cannot be justified save in extraordinary circumstances) Tolerable only if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement gained ALARP REGION (Risk is undertaken only if a benefit is desired) Benchmark representing the standard to be met by new plant Tolerable if cost of reduction would exceed the improvement gained BROADLY ACCEPTABLE REGION Necessary to maintain assurance that risk remains at this level (No need for detailed working to demonstrate ALARP) NEGLIGIBLE RISK Figure 15 - Levels of Risk and ALARP This assessment uses the following framework as agreed with FWEL: For Industrial workers >10-3/year - Level at which mitigation of risk is required, Page 54 of 96

55 For general population >10-3/year but <10-5/year - Level at which risk reduction should be considered (i.e. ALARP region), <10-5/year - Level at which further risk reduction need not be considered. >10-4/year - Level at which mitigation of risk is required, >10-4/year but <10-6/year - Level at which risk reduction should be considered (i.e. ALARP region), <10-6/year - Level at which further risk reduction need not be considered 6.5 Evaluation of Building Risks Explosion Risks The flammable gas frequency for the site is shown in Figure 16 and Figure 17. Figure 18 to Figure 21 show the frequency of exceeding an overpressure of 100 mbar and 30 mbar respectively. The explosion risk to the workers is dependent on the protection afforded by various building as is thus dependent on building types. Figure 22 and Figure 23, Figure 24 and Figure 25, Figure 26 and Figure 27 show the explosion risks to building types B2, B4 and B5 respectively. All the occupied buildings at this site are shown to have very low explosion risk. Table 14 summarizes the over-pressure and anticipated damage from a 10-4 per year explosion scenario. Table 14- Summary Explosion Damage for the 10-4 /yr Hazard Building Number Building Name Building classification (B1-B7) 10-4 Peak Overpressure (psi) Explosion Damage (10-4) 1 Administration Building B4 0.2 Minor, Level 1 2 Canteen No1 B4 0.2 Minor, Level 1 3 Medical Center B4 0.2 Minor, Level 1 4 Main Guard House B4 0.2 Minor, Level 1 5 Central Control Room B5 0.3 Minor, Level 1 7 Laboratory B4 0.2 Minor, Level 1 8 Maintenance Workshop B2 0.3 Minor, Level 1 9 Warehouse B2 0.2 Minor, Level 1 12 Canteen No2 B4 0.2 Minor, Level 1 Page 55 of 96

56 Building Number Building Name Building classification (B1-B7) 10-4 Peak Overpressure (psi) Explosion Damage (10-4) 13 Fire Station B4 0.2 Minor, Level 1 14 Main Substation B5 0.4 Minor, Level 1 15 Emergency Generator B5 0.4 Minor, Level 1 18 SS- U04 B4 0.3 Minor, Level 1 19 SS-O04 B4 0.2 Minor, Level 1 20 SS- U01 B4 0.4 Minor, Level 1 21 SS- P09 B4 1.0 Minor, Level 1 22 SS- P07 B4 1.1 Minor, Level 1 23 SS-P02 B4 1.1 Minor, Level 1 24 SS-P06 B4 0.7 Minor, Level 1 25 SS- P03 B4 0.9 Minor, Level 1 26 SS- P04 B4 3.5 Minor, Level 1 27 SS- P01 B4 0.5 Minor, Level 1 28 SS- P08 B4 0.5 Minor, Level 1 30 SS-P05 B4 0.8 Minor, Level 1 31 SS-U03 B4 0.6 Minor, Level 1 32 SS-O03 B4 0.3 Minor, Level 1 33 SS-U02 B4 0.0 Minor, Level 1 34 SS-O01 B4 0.1 Minor, Level 1 36 ISB-014 B5 0.3 Minor, Level 1 37 ISB-013 B5 0.4 Minor, Level 1 Page 56 of 96

57 Building Number Building Name Building classification (B1-B7) 10-4 Peak Overpressure (psi) Explosion Damage (10-4) 38 ISB-03 B5 0.9 Minor, Level 1 39 ISB-011 B5 0.9 Minor, Level 1 40 ISB-06 B5 1.5 Minor, Level 1 41 ISB-05 B5 0.8 Minor, Level 1 42 ISB-04 B5 0.8 Minor, Level 1 43 ISB-02 B5 1.7 Minor, Level 1 44 ISB-12 B5 0.5 Minor, Level 1 45 ISB-01 B5 0.5 Minor, Level 1 46 ISB-10 B5 0.5 Minor, Level 1 48 ISB-08 B5 0.6 Minor, Level 1 49 ISB-07 B5 0.8 Minor, Level 1 50 ISB-18 B5 0.6 Minor, Level 1 51 ISB-17 B5 0.2 Minor, Level 1 52 ISB-15 B5 0.1 Minor, Level 1 53 ISB-16 B5 0.3 Minor, Level 1 54 ISB-19 B5 0.0 Minor, Level 1 56 Jetty Area Guard House B4 0.0 Minor, Level 1 60 Jetty Area Admin/Control Building B5 0.0 Minor, Level 1 Page 57 of 96

58 Figure 16 Flammable Gas Frequency across the Main Plant Page 58 of 96

59 Figure 17 Flammable Gas Frequency across the Jetty Area Page 59 of 96

60 Figure 18 - Frequency of Overpressure Exceeding 100 mbar Main Plant Page 60 of 96

61 Figure 19 - Frequency of Overpressure Exceeding 100 mbar Jetty Area Page 61 of 96

62 Figure 20 - Frequency of Overpressure Exceeding 30 mbar Main Plant Page 62 of 96

63 Figure 21 - Frequency of Overpressure Exceeding 30 mbar Jetty Area Page 63 of 96

64 Figure 22 - Explosion Risk Plot for Building Type B2 Main Plant Page 64 of 96

65 Figure 23 - Explosion Risk Plot for Building Type B2 Jetty Area Page 65 of 96

66 Figure 24 - Explosion Risk Plot for Building Type B4 Main Plant Page 66 of 96

67 Figure 25 - Explosion Risk Plot for Building Type B4 Jetty Area Page 67 of 96

68 Figure 26 - Explosion Risk Plot for Building Type B5 Main Plant Page 68 of 96

69 Figure 27 - Explosion Risk Plot for Building Type B5 Jetty Area Page 69 of 96

70 6.5.2 Fire Risk The frequency of cloud fire, frequency contour plots for heat flux exceeding 15kW/m 2 and BLEVE frequency plots are shown in Figure 28, Figure 29, Figure 30, Figure 31 and Figure 32 respectively. Page 70 of 96

71 Figure 28 - Cloud Fire Frequency Contour Plot Main Plant Page 71 of 96

72 Figure 29 - Cloud Fire Frequency Contour Plot Jetty Area Page 72 of 96

73 Figure 30 - Frequency Contour Plot for Heat Flux above 15kW/m 2 Main Plant Page 73 of 96

74 Figure 31 - Frequency Contour Plot for Heat Flux above 15kW/m 2 Jetty Area Page 74 of 96

75 Figure 32 BLEVE Risk Plot Page 75 of 96

76 The Individual Risk (IR) from fire for the most exposed person within the occupied buildings was found to be negligible. This is based on the building being type B2. Table 15 summarises the frequency of exceeding heat flux of 15kW/m2 at various buildings. Table 15 Frequency of 15kW/m 2 at buildings Building Number Building Name Freq of 15 kw/m 2 1 Administration Building Negligible 2 Canteen No1 Negligible 3 Medical Center Negligible 4 Main Guard House Negligible 5 Central Control Room Negligible 7 Laboratory Negligible 8 Maintenance Workshop Negligible 9 Warehouse Negligible 12 Canteen No2 Negligible 13 Fire Station Negligible 14 Main Substation SS-M01 Negligible 15 Emergency Generator Negligible 18 SS- U04 Negligible 19 SS - O04 Negligible 20 SS- U01 Negligible 21 SS- P E SS- P E SS-P E SS-P E-03 Page 76 of 96

77 Building Number Building Name Freq of 15 kw/m 2 25 SS- P E SS- P E SS- P E SS- P E SS-P E SS-U E SS-O E SS-U E SS-O01 Negligible 36 ISB-014 Negligible 37 ISB E ISB E ISB E ISB E ISB E ISB E ISB E ISB E ISB E ISB E ISB E ISB E-03 Page 77 of 96

78 Building Number Building Name Freq of 15 kw/m 2 50 ISB E ISB E ISB-15 Negligible 53 ISB-16 Negligible 54 ISB E Local Guardhouse No2 (Jetty Area) Negligible 60 Jetty Area Admin/Control Building Negligible Page 78 of 96

79 7 RISK ASSESSMENT 7.1 On Site Risk This section compares the risks calculated in Section 6 with the acceptance criteria. Table 16 summarises the occupancy risk for each building on the site and compares it against the acceptance criteria defined in Section 6.4. It is highlighted that Table 16 includes the risk contributions for explosion and fire scenarios in order to provide the total risk to particular building occupants. It is noted that toxic risks for the building occupants at the site are not included in accordance with the scope of this work. All the occupied buildings are considered to be exposed to negligible risk from fire and explosion events. Detailed recommendations for mitigations for each building considered within the assessment are provided in Section 8 of this report. Table 16 - Summary Occupancy Risk Values Building Number Building Name Building classification (B1-B7) Tolerability 1 Administration Building B4 Acceptable 2 Canteen No1 B4 Acceptable 3 Medical Center B4 Acceptable 4 Main Guard House B4 Acceptable 5 Central Control Room B5 Acceptable 7 Laboratory B4 Acceptable 8 Maintenance Workshop B2 Acceptable 9 Warehouse B2 Acceptable 10 Central Chemical Store B2 Acceptable 11 Central Catalyst Store B2 Acceptable 12 Canteen No2 B4 Acceptable 13 Fire Station B4 Acceptable 55 Local Guardhouse No1 B4 Acceptable Page 79 of 96

80 Building Number Building Name Building classification (B1-B7) Tolerability 56 Jetty Area Guard House B4 Acceptable 60 Jetty Area Admin/Control Building B5 Acceptable Page 80 of 96

81 Table 17 Overall Risk to Functionally Significant Buildings Building Number Building Name Type Frequency For Damage > 2B Cloud Fire Frequency Frequency of flux greater than 15 kw/m 2 Overall Frequency of Damage Overall Risk 26 SS- P04 B4 Negligible 2.06E E E-02 Mitigate 30 SS-P05 B4 Negligible 2.72E E E-02 Mitigate 47 ISB-09 B5 2.90E E E E-02 Mitigate 45 ISB-01 B5 1.00E E E E-02 Mitigate 27 SS- P01 B4 Negligible 5.38E E E-02 Mitigate 49 ISB-07 B5 Negligible 2.57E E E-02 Mitigate 43 ISB-02 B5 Negligible 2.06E E E-02 Mitigate 28 SS- P08 B4 2.00E E E E-03 Mitigate 40 ISB-06 B5 Negligible 2.36E E E-03 Mitigate 21 SS- P09 B4 5.00E E E E-03 Mitigate 24 SS-P06 B4 Negligible 1.54E E E-03 Mitigate 48 ISB-08 B5 Negligible 1.03E E E-03 Mitigate Page 81 of 96

82 Building Number Building Name Type Frequency For Damage > 2B Cloud Fire Frequency Frequency of flux greater than 15 kw/m 2 Overall Frequency of Damage Overall Risk 38 ISB-03 B5 Negligible 5.15E E E-03 Mitigate 22 SS- P07 B4 2.50E E E E-03 Mitigate 25 SS- P03 B4 Negligible 8.40E E E-03 Mitigate 39 ISB-011 B5 Negligible 1.76E E E-03 Mitigate 33 SS-U02 B4 Negligible 8.22E E E-03 Mitigate 46 ISB-10 B5 1.80E E E E-03 Mitigate 32 SS-O03 B4 Negligible 2.84E E E-04 ALARP 41 ISB-05 B5 Negligible 1.52E E E-04 ALARP 42 ISB-04 B5 Negligible 1.52E E E-04 ALARP 23 SS-P02 B4 2.00E E E E-04 ALARP 44 ISB-12 B5 Negligible 1.31E E E-04 ALARP 50 ISB-18 B5 Negligible 2.68E E E-05 ALARP 51 ISB-17 B5 Negligible 2.31E E E-05 ALARP Page 82 of 96

83 Building Number Building Name Type Frequency For Damage > 2B Cloud Fire Frequency Frequency of flux greater than 15 kw/m 2 Overall Frequency of Damage Overall Risk 54 ISB-19 B5 Negligible 1.46E E E-05 ALARP 20 SS- U01 B4 1.30E E E E-05 ALARP 37 ISB-013 B5 Negligible 5.04E E E-06 Acceptable 31 SS-U03 B4 Negligible 3.49E E E-06 Acceptable 19 SS-O04 B4 2.50E-06 Negligible Negligible 2.50E-06 Acceptable 14 Main Substation SS-M01 B5 Negligible 1.27E-06 Negligible 1.27E-06 Acceptable 15 Emergency Generator B5 Negligible 1.27E-06 Negligible 1.27E-06 Acceptable 36 ISB-014 B5 1.00E-06 Negligible Negligible 1.00E-06 Acceptable 53 ISB-16 B5 Negligible 1.54E E E-07 Acceptable 1 Administration Building B4 Negligible Negligible Negligible Negligible Acceptable 2 Canteen No1 B4 Negligible Negligible Negligible Negligible Acceptable 3 Medical Center B4 Negligible Negligible Negligible Negligible Acceptable 4 Main Guard House B4 Negligible Negligible Negligible Negligible Acceptable Page 83 of 96

84 Building Number Building Name Type Frequency For Damage > 2B Cloud Fire Frequency Frequency of flux greater than 15 kw/m 2 Overall Frequency of Damage Overall Risk 5 Central Control Room B5 Negligible Negligible Negligible Negligible Acceptable 12 Canteen No2 B4 Negligible Negligible Negligible Negligible Acceptable 13 Fire Station B4 Negligible Negligible Negligible Negligible Acceptable 18 SS- U04 B4 Negligible Negligible Negligible Negligible Acceptable 34 SS-O01 B4 Negligible Negligible Negligible Negligible Acceptable 52 ISB-15 B5 Negligible Negligible Negligible Negligible Acceptable 56 Jetty Area Guard House B4 Negligible Negligible Negligible Negligible Acceptable 60 Jetty Area Admin/Control Building B5 Negligible Negligible Negligible Negligible Acceptable Page 84 of 96

85 7.2 Off-site Risk Villages to the East of the site Societal Risk The societal risks are presented in the form of an F-N Curve in Figure 33. The villages are considered to have approximately 320 dwellings with 5 people each on average. The construction of the dwellings is assumed to be basic, affording little protection from fire or toxic gas ingress. The F- N curve shows that the societal risks to the villages from the NSRP are unacceptable. Note: Figure 33 F-N Curve (Villagers only) The risk levels in the F-N curve are represented as follow (See Section 6.4.2) Red Region: Unacceptable; Yellow & Green Region: Acceptable according to UK HSE document R2P2 definition [12]; Green Region: A conservative acceptability criteria used by some companies. R2P2 states that death of more than 50 people in any incident should be less than 1 in 5000 years. The F-N curve is constructed by using a slope of -1 from FN pair of 2x10-4, 50 and Nmax of 1000 [12]. The line is represented by the interface between the RED and YELLOW regions of Figure 33, implying that values within the RED region are unacceptable Individual Risk The Location Specific Individual Risk (LSIR) is shown in Figure 34 and Figure 35. The maximum location specific individual risk (LSIR) at the villages is 5.42x10-3 /year. LSIR represents an individual risk (IR) to an individual who remains at the location at all the time. Considering that the individual could move to different location from high risk to low risk, an occupancy ratio of 0.5 is appropriate thus giving an individual risk (IR) of 2.71E-3 per year. This level of risk is considered unacceptable (>1E-4 is unacceptable for general public). Even if the occupancy ratio is taken as 0.1, i.e. an individual is only in the high risk area for less than 2.5 hours per day, the risks are still unacceptable. Page 85 of 96

86 It may therefore be concluded that the risk to the villages is unacceptable both from individual risk and societal risk perspectives Road to the South of the site Individual Risk The Location Specific Individual Risk (LSIR) for the road is shown in Figure 34. The results show that the maximum LSIR at the road area is 1.88x10-3 /year. The occupancy ratio considered for the road is based on the traffic moving at 60 km/hour and any one individual travelling twice a day, six days per week across the site on this road. Therefore, the maximum individual risk at the road is 1.13x10-5 /year which corresponds to the ALARP region based on the risk tolerability criteria in Section 6.4. This implies that mitigation measures should be considered to reduce risks as long as the cost of such measures is not disproportionate to the benefit. Page 86 of 96

87 Figure 34 Total Fire and Explosion Risk Contour Level Main Plant Page 87 of 96

88 Figure 35 Total Fire and Explosion Risk Contour Level Jetty Area Page 88 of 96

89 8 CONCLUSIONS & RECOMMENDATIONS 8.1 Buildings at the site The results from this coarse QRA indicate that there are a number of buildings at the site that require risk reduction measures. This includes 18 buildings where risk mitigation must be undertaken and 10 buildings where risk mitigation should be considered, and implemented as necessary, in order to demonstrate that the building s risk status is ALARP. Total fire and explosion risk contour level The focus of the Risk mitigation is to reduce the likelihood and/or consequences of explosions/fire on the site. Based on this analysis, the following Table 18 provides a summary of recommendations for refinement of the risk predicted for an area/building or for mitigation of its risk. The recommendations are presented as General, Explosion and Fire. Even though the explosion risk at NSRP is low, it is recommended that best industrial practice should be used and building classification not be downgraded based on the results of this risk assessment. Furthermore, a detailed QRA must be undertaken once detailed plant design is in place to confirm or update the explosion risks in particular which are sensitive to plant congestion but also other risks which are based on the early plant information. At the detailed QRA stage, it may be possible to take account of various mitigations in place such as the water deluge, shutdown and blowdown and risk based inspection and maintenance and regular fugitive emission testing. Table 18 Recommendations Ref. No. Description of Recommendations Options General Recommendations Reduce Event Likelihood L1 L2 L3 L4 L5 L6 Ensure that the design specifications for all plant include performance standards such that plant failure, and thus hydrocarbon release scenarios, will be minimized through design. Reduce the hazard magnitude through the installation of gas (toxic and flammable) detectors with emergency shutdown (ESD) systems within the critical hazard locations. Emergency shutdown valves to be located outside fire impact zone. If the valve is located inside a fire/explosion zone then fire proofing is necessary to provide protection for a specified period of time in line with API Minimize the presence of ignition sources around the process units Where possible, consider leak point minimization for all equipment (e.g. welded, rather than flanged pipe connections, fail safe valves, spring loaded manual valves, flange covers) Implement a risk-based inspection (RBI) and maintenance process such that the plant items that pose the greatest risk to the plant receive the greatest levels of inspection and maintenance Since there is a risk of an event moving onto the public highway, provisions will need to be in place to prevent traffic movement on the highway in the event of a site incident. Page 89 of 96

90 Ref. No. L7 Description of Recommendations Options Toxic and vapour cloud events, generally leave the site periphery it is suggested that a plan will need to be in place to alert the populations to either end of the plant limit in the event of a site incident. Such measures will form part of the Site Emergency Response Plan which is to be detailed during the Detailed design. Reduce Vulnerability Emergency procedures should be put in place and followed if a leak is detected. Good procedures and training for emergency response are essential. V1 V2 Reduce the vulnerability of the building occupants through the avoidance of windows within buildings located within the process areas. Reduce the vulnerability of the building occupants to toxic ingress through the implementation of toxic gas detection and dampers on the HVAC inlet ducts for putting into recycle as well as manual shutdown. Explosion Recommendations V3 V4 V5 V6 V7 Reduce the vulnerability through relocation of road, provide a barrier between road and plant (not always effective for blast but prevents missiles) and reduce congestion near the site boundary. For buildings with cloud fire frequency >1E-4 p.a., positive pressurisation and double doors should be provided in the building. LEL detection should also be incorporated into the ventilation inlets & automatically shutdown the ventilation system providing alarms on LEL detection For buildings with cloud fire frequency between 1E-4 & 1E-5 p.a. self-closing doors with gas tight seals should be provided in addition to LEL detection in the ventilation inlets providing automatic shutdown of the ventilation system and alarms on LEL detection (See Table 28 and Table 29). For Buildings with cloud fire frequency between 1E-5 & 1E-6 p.a., self-closing doors with gas tight seals and LEL monitors alarms and manual HVAC shutdown should be provided. Buildings should be designed to withstand the 10-4/yr explosion overpressure as a minimum Fire Recommendations V8 V9 V10 Reduce the vulnerability of the buildings to flammable gas ingress through the implementation of flammable gas detection and dampers on the HVAC inlet ducts, self-closing doors with gas tight seals and LEL monitors, alarms and manual HVAC shutdown should be provided. As given for explosion Reduce risk to building occupants from fire by ensuring building has safe refuge areas in case of fire and /or the building has adequate fire proofing. Reduce BLEVE risk by insulating vessels, improve depressurisation and vessel deluge. Depressurized the leaking section using blowdown system. Toxic Recommendations Page 90 of 96

91 Ref. No. Description of Recommendations Options T1 The ERPG contours are based on gas dispersion modeling for free field flat terrain. Simple consequence assessment models used in QRA are not appropriate for dealing with complex terrain especially for near field effects. It is recommended that a Computational Fluid Dynamics based H2S dispersion study should be undertaken in the detailed phase of the design to ascertain the toxic risks and if there are any specific areas where high H2S concentrations might develop due to the presence of the mountain to the west of the site. Based on the mitigation options detailed in Table 18, recommendations in respect of explosion risk for each functional but considered unoccupied building were assessed are provided in Table 19. Table 19 Recommendations Functional Significant Buildings Building Cloud Fire Risk LEL Detection Manual HVAC Shutdown Automatic HVAC Shutdown Positive Pressurisation in building and double doors Self Closing Doors with gas tight seals ISB E-03 Yes No Yes Yes No SS- P E-03 Yes No Yes Yes No ISB E-03 Yes No Yes Yes No SS-P E-03 Yes No Yes Yes No ISB E-03 Yes No Yes Yes No ISB E-03 Yes No Yes Yes No SS- P E-03 Yes No Yes Yes No ISB E-03 Yes No Yes Yes No ISB E-03 Yes No Yes Yes No SS-P E-03 Yes No Yes Yes No SS- P E-03 Yes No Yes Yes No ISB E-03 Yes No Yes Yes No SS-U E-04 Yes No Yes Yes No SS- P E-04 Yes No Yes Yes No ISB E-04 Yes No Yes Yes No Page 91 of 96

92 Building Cloud Fire Risk LEL Detection Manual HVAC Shutdown Automatic HVAC Shutdown Positive Pressurisation in building and double doors Self Closing Doors with gas tight seals ISB E-04 Yes No Yes Yes No ISB E-04 Yes No Yes Yes No ISB E-04 Yes No Yes Yes No SS- P E-04 Yes No Yes Yes No ISB E-04 Yes No Yes Yes No SS-P E-05 Yes No Yes No Yes SS- P E-05 Yes No Yes No Yes ISB E-05 Yes No Yes No Yes ISB E-05 Yes No Yes No Yes ISB E-05 Yes No Yes No Yes ISB E-06 Yes No Yes No Yes SS-U E-06 Yes No Yes No Yes Main Substation SS-M E-06 Yes No Yes No Yes Emergency Generator 1.27E-06 Yes No Yes No Yes SS- U E-06 Yes No Yes No Yes SS-O E-07 No Yes No No Yes ISB E-08 No Yes No No Yes Administration Building Canteen No1 Negligible Negligible No No No No No No No No No No Page 92 of 96

93 Building Cloud Fire Risk LEL Detection Manual HVAC Shutdown Automatic HVAC Shutdown Positive Pressurisation in building and double doors Self Closing Doors with gas tight seals Medical Center Main Guard House Central Control Room Canteen No2 Fire Station SS- U04 SS-O04 SS-O01 ISB-014 ISB-15 Jetty Area Guard House Jetty Area Admin/Control Building Negligible Negligible Negligible Negligible Negligible Negligible Negligible Negligible Negligible Negligible Negligible Negligible No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No 8.2 Off-site Population Villages to the East of the site The risk to the villages, both in terms of individual and societal are unacceptable. Assuming that the site location has been decided, the risk from the NSRP site to the villages are such that reasonable measures of reducing risks to an acceptable level could be impractical. The Societal risks can be reduced by reducing the population and reducing the frequency and magnitude of hazards from the site. However, the risk assessment here does not take account of the fact that the villages are in wooded area which is susceptible to fire escalation. In light of this, re-location of the villages to a safer place should be given serious consideration. Page 93 of 96

94 8.2.2 Road to the South of the plant Although the risks to the road users for Bidder 1 option are lower than the FEED study case, the road is nonetheless too close to the Plant boundary. It is prudent to keep the option of a barrier between the Plant and the road as well as traffic control measures. The recommendations to reduce risks to the road users are as follows in Table 20. Table 20 Recommendations vulnerability Ref. No. Description of Recommendations Options Reduce Vulnerability to Offsite Road to the South VR1 VR2 Reduce the vulnerability by adding a barrier along the high risk part of the plant boundary between the plant and the road to the south to prevent direct fire impingement and to reduce heat flux. Reduce risk to road users by early warning on leak and closure of access. It is proposed that a 500m long, 6m high concrete wall designed to withstand 30 mbar side-on overpressure as shown on Figure 36, together with the traffic control measures should provide practical mitigation solution. Control barriers/stop lights Concrete Wall 500m (6m high to withstand 30 mbar overpressure) Control barriers/stop lights Figure 36 Proposed concrete wall and traffic warning/control Page 94 of 96