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STAVANGER QRA Lyse LNG Base Load Plant Linde Project No:
Lyse Infra AS Item No:
Lyse Contract No:
2110A11U
61-10156.05.01
Linde Job Code:
Lyse Project No:
STAVANGER
R100
Linde Doc. No:
Lyse Doc. No:
Page
&AA S-CS 1002
R100-LE-S-RS0003
1 of 133
Quantitative Risk Analysis (QRA) Lyse LNG Base Load Plant Train 1
03
ISSUE
03
25.08.2008
Rath
Ralph
22.02.2008 28.12.2007
Revised acc. to Lyse Comments Can Revised acc. to the Comments in Can QRA presentation from 26.02.2008 Revised acc. to the Lyse Comments Can Can
02
ISSUE
02
14.03.2008
01 Rev
ISSUE DRAFT Status
01 Issue
(Lyse)
(Linde)
(Linde)
Rath/Baumgartner Buttinger
Ralph Can
Date
Description
Reviewed
Approved
Prepared
Rath
Buttinger
STAVANGER QRA Lyse LNG Base Load Plant Linde Project No:
Lyse Contract No:
Lyse Infra AS Item No:
2110A11U
61-10156.05.01
Linde Job Code:
Lyse Project No:
STAVANGER
R100
Linde Doc. No:
Lyse Doc. No:
Page
&AA S-CS 1002
R100-LE-S-RS0003
1 of 133
Table of Contents 1.0
Executive Summary...................................................................... 3
2.0 2.1 2.2
Introduction .................................................................................................... 9 Objective of the Study ...................................................................................... 9 General Description of the Approach ............................................................... 9
3.0
General Description of Process and Facilities......................... 13
3.1 3.1.1 3.1.2 3.1.3 3.2 3.2.1 3.2.2 3.3 3.3.1 3.3.2 3.4 3.5 3.6 3.7
Natural Gas Treatment and Gas Liquefaction ................................................ 13 Feed Gas Reception ...................................................................................... 13 Natural Gas Pretreatment............................................................................... 13 NG Liquefaction.............................................................................................. 14 Refrigerant System......................................................................................... 14 Refrigerant Cycle............................................................................................ 15 Refrigerant Storage and Make-Up.................................................................. 15 LNG Storage / LNG Loading .......................................................................... 16 LNG Storage .................................................................................................. 16 LNG Loading .................................................................................................. 16 Fuel Gas System ............................................................................................ 17 Hot Oil System ............................................................................................... 17 Flare System .................................................................................................. 18 ESD and Blowdown System........................................................................... 18
4.0
Study Methodology..................................................................... 20
4.1 4.2 4.3 4.4
Risk Analysis Basics....................................................................................... 20 Definition and Types of Risk........................................................................... 20 Acceptance Criteria ........................................................................................ 21 Hazard Identification....................................................................................... 23
5.0
Data used for the Risk Assessment.......................................... 25
5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.7.1 5.7.2 5.7.3
Scenarios ....................................................................................................... 25 Leak Frequencies ........................................................................................... 26 Release Duration............................................................................................ 27 Atmospheric Conditions.................................................................................. 28 Population Distribution.................................................................................... 28 Ignition Sources.............................................................................................. 29 Consequence Calculations............................................................................. 30 Discharge and Dispersion .............................................................................. 30 Instantaneous Releases ................................................................................. 31 Continuous Releases ..................................................................................... 31
STAVANGER QRA Lyse LNG Base Load Plant Linde Project No:
Lyse Contract No:
Lyse Infra AS Item No:
2110A11U
61-10156.05.01
Linde Job Code:
Lyse Project No:
STAVANGER
R100
Linde Doc. No:
Lyse Doc. No:
Page
&AA S-CS 1002
R100-LE-S-RS0003
2 of 133
5.7.4 5.7.5 5.7.6 5.8
Release Duration............................................................................................ 31 Dispersion ...................................................................................................... 31 Thermal Radiation and Overpressure............................................................. 31 Mitigation Measures taken into Account ......................................................... 32
6.0
Results of the Risk Analysis...................................................... 34
6.1 6.2 6.3 6.4
Risk 1st and 2nd party ...................................................................................... 34 Risk 3rd party .................................................................................................. 39 Location Specific Risk .................................................................................... 45 Overpressure Risk.......................................................................................... 46
7.0
Sensitivity Evaluation................................................................. 50
7.1 7.1.1 7.1.2 7.2 7.2.1 7.2.2 7.3
Sensitivity 1: Pit on the jetty, LNG Storage Tank and the Pentane Tank ................................................................................................. 50 Discussion ...................................................................................................... 50 Comparison with Criteria ................................................................................ 53 Sensitivity 2: Rock Wall towards the public area on the peninsula ................. 53 Discussion ...................................................................................................... 53 Comparison with Criteria ................................................................................ 54 Sensitivity 3: Splitting of process vessels inside the refrigerant cycle into smaller vessels and additional block valves to reduce the volume of inventory loops......................................................................... 54
8.0
Conclusions ................................................................................ 55
9.0
Appendix A: Assumption Sheets .............................................. 56
10.0
Appendix B: Hazard Identification ............................................ 90
11.0
Appendix C: Equipment Count.................................................. 95
12.0
Appendix D: Results of LEAK 3.2 Calculations ....................... 99
13.0
Appendix E: Individual Risk Ranking Report......................... 104
14.0
Appendix F: Details on the Analysis Procedure .................... 127
15.0
References ................................................................................ 132
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
1.0
25.08.2008 Page 3
Executive Summary
Linde Engineering AG (Linde), on the behalf of Skangass AS (Skangass), has conducted a Quantitative Risk Analysis (QRA) of the first train of the new Lyse LNG Base Load Plant, located near Stavanger, Norway. The objective of the study was to determine the level of risk associated with the Lyse LNG Base Load Plant, which is currently being designed, and compare it with the acceptance criteria given by Lyse Infra AS (Lyse).
Approach To achieve this objective, a thorough analysis was made of all hazardous substance inventories and streams within the plant. In particular, all equipment were counted and used as a basis to calculate leakage frequencies. The determination of leakage frequencies was done using the program "LEAK", a proprietary program from Det Norske Veritas (DNV). To achieve this, the whole plant was segmented, four leak size categories were defined, and leakage frequency calculations were performed for the segments based on the categories. Meteorological data as well as population data provided by Lyse were used for study. The data are important for DNV's risk assessment tool PHAST RISK (further SAFETI), which takes into account (when applicable): • • • •
Pool fires, Jet Fires, Flash Fires and Vapour Cloud Explosions.
For the scenarios defined for the Lyse LNG Base Load Plant, the population and the determined ignition source distribution were entered into PHAST RISK and analysed with respect to their contribution to individual risk and to societal risk.
Results PHAST RISK calculates both individual risk and societal risk. The individual risk for 1st, 2nd and 3rd parties are calculated based on these results which are then compared to the acceptance criteria. As expected, the main contribution to the overall risk is due to vapour cloud explosions and flash fires. Individual Risk, 1st and 2nd party Individual risk is a measure of risk to which an individual person is exposed. The individual risk criteria are divided in this analysis into Individual Specific Risk (ISR) and Average Individual Risk (AVR). The 1st party risk is defined as a fatality risk for the Lyse LNG Base Load Plant personnel. Maintenance personnel and operators during supervision rounds are considered to be the most exposed personnel. Fatality risk for the LNG Carrier personnel (Truck, Ship Loading and external contractors) have been considered as 2nd party and are also assumed to be within the most exposed personnel group.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
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The figures 1 and 2 show the calculated individual risk contour lines for the Lyse LNG Base Load Plant. The calculated risk contours of individual risk for the most exposed person is illustrated in Figure 1. The figure shows the contours of the most exposed person to suffer a fatality every 100 000 years (green line), every 1 000 000 years (dark blue line). The risk is illustrated for the most exposed person present in the process plant area, 20 % of their working time per year. 10-5 /yr 10-6 /yr
Figure 1: Most exposed person individual risk contour lines for the Lyse LNG Base Load Plant
The risk contours for the individual risk are also calculated and is illustrated in Figure 2. The figure shows the contours of individual risk for a fatality every 10 000 years (green line), every 100 000 years (dark blue line), etc. The risk is illustrated for 1 person present at any point outside a building in the plant, continuously 8 hours a day, 5 days a week during a whole year (45 weeks).
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
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10-4 /yr 10-5 /yr 10-6 /yr 10-7 /yr 10-8 /yr
Figure 2: Individual risk contour lines for the Lyse LNG Base Load Plant
The Individual Risk (IR) has been extracted from the PHAST RISK risk report: It is calculated for 1 person and for each worker group present at any point in the plant, continuously 8760 hours per year. The Individual Specific Risk (ISR) for 1st and 2nd party, which considers the individual working hours for each group, is given below in Table 1.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
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Table 1: Individual Specific Risk (ISR) for 1st and 2nd party Buildings/Personnel Locations Operator
ISR [year] 1.2 X 10-4
Process Area (Maintenance)
1.2 X 10-4
Truck Loading
6.7 X 10-5
Ship Loading (Jetty)
2.0 X 10-5
Ship Bridge
5.0 X 10-5
Ship Deck
4.8 X 10-5
ISR > 1 X 10-3
Not acceptable
1 X 10-3 < ISR < 1 X 10-6
ALARP
ISR < 1 X 10-6
Acceptable
The Average Individual Risk (AVR) of 5.0 X 10-5 per year for all personnel (1st and 2nd party) is within the ALARP regime, i.e. As Low As Reasonably Practical, which means that the mitigation measures may be applied as long as the respective cost benefit ratio is reasonable. Individual Risk, 3rd party For the Lyse LNG Base Load Plant such mitigation measures have already been applied (e.g. a rock wall "mound" around the LNG tank, the ESD and Blowdown system). The Individual Specific Risk (ISR) for the 3rd party risk is given below in Table 2. Table 2: Individual Specific Risk (ISR) for the 3rd party Personnel Locations Peninsula
ISR [year] 4.6 X 10-8
Hiking Track
2.2 X 10-6
Ferry Terminal_office workers
7.6 X 10-7
Ferry Terminal_industry workers
3.8 X 10-7
Ferry Terminal_passengers
4.0 X 10-7
Energiveien+Risavika_office workers
4.6 X 10-9
Energiveien+Risavika_industry workers
4.6 X 10-9
Container Area_office workers
3.2 X 10-9
Container Area_industry workers
3.2 X 10-9
Rest Companys_office workers
2.8 X 10-14
Rest Companys_industry workers
2.8 X 10-14
Living Quarters
3.5 X 10-10
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
ISR > 1 X 10-5
Not acceptable
1 X 10-5 < ISR < 1 X 10-7
ALARP
ISR < 1 X 10-7
Acceptable
25.08.2008 Page 7
The Average Individual Risk (AVR) of 1.5 X 10-7 per year for people living, working or staying outside the Lyse LNG base load plant does not exceed the acceptance criteria of 1 X 10-5 / year and is within the ALARP regime. Societal Risk, 3rd party Societal risk (or 3rd party 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. The societal risk calculated for the Lyse LNG Base Load Plant is shown below in Figure 3.
Figure 3: Societal risk FN curve for the Lyse LNG Base Load Plant
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
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The minimum and maximum risk criteria are shown in Figure 3 as blue and green lines respectively. Calculations of the external societal risk (e.g. Hiking Track, Peninsula, Industry Area and Ferry Terminal) have shown that this risk for the Lyse LNG Base Load Plant falls into the area between the upper and lower limit line, i.e. the ALARP regime.
Conclusions A careful risk analysis of the first train of the Lyse LNG Base Load Plant has been performed, including a very detailed counting of all pieces of equipment (including all pipelines, vessels and compressors etc.). It has been found that the calculated levels of individual risk for the 1st, 2nd and 3rd parties are in compliance with the criteria set by Lyse. The individual specific risk for 1st and 2nd party for the most exposed person in each group, maintenance and operators, is lower than 1 X 10-3 per year and within the acceptance criteria. The average individual risk for personnel is 5.0 X 10-5 per year and therefore clearly below the acceptance criteria of 1 X 10-4 / year. The individual specific risk for 3rd party for the most exposed population (e.g. hiking track, ferry terminal industry and office workers) is within the ALARP regime. The average individual risk is 1.5 X 10-7 per year and therefore within the lower region of ALARP, close to acceptable in general. The calculated risk for the Peninsula people is acceptable since the rock wall (mound) is taken into account (refer to the Chapter 7.2).
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
2.0
25.08.2008 Page 9
Introduction
Linde is currently performing the design of train 1 of the new Lyse LNG Base Load Plant, located near Stavanger, Norway, on behalf of Skangass. The design of the plant shall conform to EN 1473:2007 "Installation and equipment for liquefied natural gas – Design of onshore installations" [1]. To fulfil EN 1473 a hazard assessment shall be carried out during the design of the plant. A part of this hazard assessment is a risk investigation, in this case using Quantitative Risk Analysis (QRA). This document describes in detail the results and methodology used to obtain the results of the QRA.
2.1
Objective of the Study
The objective of the study was to estimate the level of risk by QRA. The performed QRA covered all essential risks of the new Lyse LNG Base Load Plant as far as they are of relevance and have been determined in the Hazard Identification (HAZID) [Appendix B]. The individual personnel risk and the 3rd party risk are evaluated in this study. The overpressure risk to the plant buildings and equipment (Central Control Room, LNG Tank etc.) and a consequence modelling of worst case scenarios, e.g. hydrocarbon dispersion from the LNG Tank, are included in the calculations.
2.2
General Description of the Approach
QRA is a well established methodology to assess the risks of industrial activities and to compare them with risks of normal activities. Linde has used a QRA methodology as shown in Figure 4. The QRA performed by Linde used the QRA Reports performed by Advantica [2] as a reference. Data Collection This study is based on the following documents: • • • • • • • • • • •
Process Flow Diagrams (PFDs) Heat and Material Balance Process and Instrument Diagrams (P&IDs) Process Description General Plot Plan Mechanical and Process Data Sheets ESD and Blow-down System Concept Lyse LNG Base Load Plant Site conditions Manning Level Table [3]. Acceptance Risk Criteria for Lyse LNG Base Load Plant Development Area Plan and Information from Lyse
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Figure 4: QRA Methodology
Collection and Analysis of Background Data This was an internal Linde exercise to collect information relevant to the QRA study. The leak frequencies for equipment, valves etc. are based on DNV database and included in DNV's proprietary program “LEAK”. Hazard Identification (HAZID) The hazard identification process is important for any risk analysis. A HAZID was been performed prior to the QRA by Linde. A HAZOP study for the main plant has been completed.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Introduction
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Frequency Analysis Failure frequencies were determined for each event in order to perform a probabilistic risk assessment. Generally, a number of techniques are available to determine such frequencies. The approach relies on generic data. This provides failure frequencies for equipment items where data has been obtained from failure reports from a range of facilities. DNV has developed an extensive generic failure frequency database for this purpose, which is compiled in DNV's proprietary LEAK 3.2 software. These leak frequencies are based on the "UK Health & Safety Executive" data for offshore facilities. To reflect the design of the Lyse LNG base load plant, which is a onshore facility and has clean service, new leak frequencies for pipes and process vessels based on the "Purple Book" [6] are implemented in the LEAK Program. The changes are shown in Appendix D. This program was used to determine overall leakage frequencies subsequently used in the risk assessment. Consequence Analysis For each hazard scenario PHAST RISK (Software for the Assessment of Flammable, Explosive and Toxic Impacts) and PHAST (Process Hazard Assessment Software Tool) software was used to determine consequence effect zones for each hazard. The different possible outcomes could be: • • • • • • •
Dispersing of Hydrocarbon Vapour Cloud Explosion Fireball BLEVE Flash Fire Jet Fire Pool Fire.
The CO2/H2S (sour gas) in CO2 wash unit is routed to the regenerative thermal oxidation and then sent to atmosphere at safe location. Dispersion from a leak of CO2/H2S gas cloud due to low operating pressure is not considered as the contribution to the risk is minor compared to the above mentioned outcomes. The particular outcomes modelled depend on source terms (conditions like fluid, temperature, pressure etc.) and release phenomenology. The current understanding of the mechanisms occurring during and after the release is included in state-of-the-art models in the PHAST RISK and PHAST packages. Risk Calculations The outcome of the PHAST RISK analysis are risk terms presented in form of risk contours and FN curves, where the former is a form of location specific individual risk measurement while the latter is a measure for societal (group) risk. The individual risk is the risk for a hypothetical individual assumed to be continuously present at a specific location. The individual at that particular location is expected to sustain a given level of harm from the realization of specified hazards. It is usually expressed in risk of death per year. Individual risk is presented in form of risk contours. Societal Risk is the risk posed to a local community or to the society as a whole from the hazardous activity. In particular it is used to measure the risk to every exposed person, even if they are exposed on one brief occasion. It links the relationship between the frequency and the number of people suffering a given level of harm from the realization of a specified hazard. It is usually referred to a risk of death per year.
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Risk Criteria Risk criteria for both individual risk and societal risk have been discussed with Lyse. These criteria are compared to other risk criterion and to the results of the actual risk assessment for the plant. Risk Assessment Once risks have been determined, they will be assessed against the criteria level and ranked to determine the principal contributors. Ranking enables attention to be focused on the main contributors. This is of particular significance when assessing the viability of different mitigation measures. Risk Mitigation Risk reduction measures concentrate on the major risk contributors identified during risk ranking. Discussion is made on how different risk reduction measures will affect the overall risk level in relation to the ALARP principle (As Low As Reasonably Practical). Report structure The safety studies are documented according to the following report structure: • • • • • • •
Main report The main report summarizes the study data, methodology, the risk results, conclusions and sensitivities Appendix A – Assumptions The main assumptions where the studies are based on are presented in this appendix. Appendix B – HAZID This appendix documents the results of the HAZID workshop in Munich, October 2007. Appendix C – Equipment Count This appendix documents the equipments with their dimensions and inventories used to determine the leak size and – frequency for the risk assessments Appendix D – Result of LEAK 3.2 Calculations This appendix documents the risk leakage frequencies based on the UK HSE databank [4] and the Dutch Purple Book [5] Appendix E – Individual Risk Ranking Report This appendix documents the risk ranking points, for which the individual risk has been calculated Appendix F – Details on the Analysis Procedure This appendix gives details of the actual QRA methodology
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 General Description of Process and Facalities
3.0
25.08.2008 Page 13
General Description of Process and Facilities
The section briefly describes the process and facilities to ensure a common understanding. The description only addresses those parts, which are of relevance to the QRA.
3.1
Natural Gas Treatment and Gas Liquefaction
3.1.1
Feed Gas Reception
Feed gas is received via a pipeline pressure let-down station from the Kårstø NG Plant with a pressure of approx. 180 bara. The pressure is controlled at plant inlet to 111 bara. A Feed Gas Fiscal Metering Station 15-XT-101 including a filtration device for the removal of particles is installed. 3.1.2
Natural Gas Pretreatment
CO2 Wash Unit For CO2 removal from natural gas with the present conditions a chemical wash is the most favourable process. An aqueous amine solution (aMDEA) is utilised as solvent. The CO2 wash unit is a Linde designed unit (contrary to a packaged unit). Material and equipment within the unit are designed and supplied according to Linde Standards and Specifications. The feed gas is first heated in the Feed Gas Heater 20-HA-101 against warm lean solvent and further heated in the Feed Gas Trim Heater 20-HA-103 A/B against warm sweet gas to avoid cold temperatures and to allow for efficient CO2 removal. It enters the Amine Wash Column 20-VE-101 and flows from bottom to top through a random packing. Introduced lean amine flows in the opposite direction extracting the acid gas. The CO2 forms a very weak bond with the alkali. In the top of the column solvent traces are removed by water from the purified gas in some additional trays. The wash water for these trays is recirculated by the Water Circulation Pump 20-PA-101 A/B; a small quantity of water is introduced into the cycle by the Amine Make Up Water Pump 20-PB-102 A/B as fresh water (demin. water) to fulfil the water balance of the amine system. The clean gas exits the wash tower with a CO2 content of max 50 vppm and a temperature of approx. 40°C. It is cooled in heat exchanger 20-HA-103 A/B against Feed Gas to approx. 25°C and leaves the section at a pressure of approx. 109 bara. The loaded amine solution from 20-VE-101 passes via Amine MP Flash Drum 20-VA-102 through the Solvent Heat Exchanger 20-HB-101, where it is warmed up against regenerated solvent and is further routed to the middle section of the Amine Strip Column 20-VE-102. In 20VE-102 the reflux water flows from the top through two packed beds. The CO2 is stripped in hot oil heated Amine Strip Column Reboiler 20-HA-102. The regenerated solvent leaves the column at the bottom via heat exchanger 20-HB-101 and is pumped by the Lean Solvent Pump 20-PA-103 A/B to the top of the Amine Wash Column 20-VE-101 via the Feed Gas Heater 20HA-101 and Lean Solvent Cooler 20-HC-101. Approximately 15 % of the flow is routed through the Cartridge Filter 20-LF-101 to remove particles and then through the Activated Carbon Filter 20-LF-102 for removal of heavy hydrocarbons to prevent foaming.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 General Description of Process and Facalities
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The acid gas leaves the top of column 20-VE-102 after having passed the water wash section, installed for reduction of amine vapour in the acid gas fraction. After cooling in the Amine Strip Column Condenser 20-HC-103 the gas is separated from the condensate in the Amine KO Drum 20-VA-101. The Amine Strip Column Reflux Pump 20-PA-102 A/B delivers the condensate back to the top of column 20-VE-102. The Amine KO Drum 20-VA-101 also allows for removal of heavy hydrocarbons. The sour gas is routed to the Regenerative Thermal Oxidation 20-XT-101 and then sent to atmosphere. The Solvent Storage Drum 20-VS-101 is designed to hold the complete liquid inventory of the plant. In case of foaming anti foam agent can be injected into the solvent from the Anti Foam Package 20-XU-101. Dryer Station The sweet, water oversaturated feed gas from the wash unit is fed to the Feed Gas Water KO Drum 20-VL-111 to remove any free liquid upstream of the driers. The liquid from this vessel is routed back to the Amine MP Flash Drum 20-VA-102 to reduce the water make-up of the CO2 wash unit. The drier station is a two-bed molecular sieve adsorber station with a cycle time of 12 hrs. The natural gas is flowing through one of the Feed Gas Driers 20-VK-111 A/B. The water contained in the natural gas is reduced to a level near to zero where no freezing can occur in the downstream liquefaction section. To reduce the temperature fluctuation of the dry gas, a parallel step of 30 minutes is included, where both drier vessels are on adsorption. The dry feed gas passes the Dry Gas Filter 20-LF-111 to remove mole sieve dust which could affect the performance of the downstream cryogenic process section. During this period the other feed gas drier is heated approx. 9 hrs and then cooled approx. 2 hrs by the regeneration gas stream. Dry feed gas at approx. 106 bara serves as regeneration gas. Heating of the regeneration gas to 210°C is provided in the Regeneration Gas Heater 20HA-111 against hot oil and cooling against ambient air in the Regeneration Gas Cooler 20-HC111, followed by the Regeneration Gas Water KO Drum 20-VL-112 where the water is separated and routed to 20-VE-102. The water saturated regeneration gas is compressed by Regeneration Gas Blower 20-KF-111 and routed back into the feed line upstream of the Feed Gas Driers 20-VK-111 A/B. 3.1.3
NG Liquefaction
After CO2 and water removal the natural gas is routed to the cold part of the process, which consists of three spiral-wound heat exchanger bundles integrated in one shell. Liquefaction and subcooling of the feed gas at high pressure is possible because of absence of heavy hydrocarbon components in the design feed gas. The natural gas from the filter 20-LF-111 is first cooled down to approx. -26°C in the Feed Gas Precooler 25-HX-101. It is then further cooled down in the Feed Gas Liquefier 25-HX-102 and throttled to a subcritical pressure of approx. 20 bara to get pure liquid. Finally the natural gas is subcooled in the Feed Gas Subcooler 25-HX-103 to a temperature of approx. -159°C which is low enough to meet the flow limit of 2000 Sm³/h tank return gas allowed for reinjection into the tailgas pipeline.
3.2
Refrigerant System
The cooling duty required to produce the LNG is provided by a simple but efficient closed mixed refrigerant cycle which consists of nitrogen, ethylene, propane, butane, pentane and a portion of the compressed tank return gas (Linde patent).
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A motor driven geared centrifugal compressor is applied to compress the refrigerant. 3.2.1
Refrigerant Cycle
The refrigerant is withdrawn from the shell side of the precooler 25-HX-101 at a temperature of approx. 20°C and a pressure of approx. 4 bara, i.e. approx. 10°C overheated against saturated conditions. The refrigerant passes the Cycle Compressor Suction Drum 25-VL-101 and is then compressed in the first stage of Cycle Compressor 25-KA-101. After cooling to approx. 25°C and partly condensing against air in the Cycle Compressor Intercooler 25-HC-101 the liquid and gas are separated in the Cycle Compressor Interstage Drum 25-VL-102. The gas is further compressed in the 2nd stage of 25-KA-101 and partly condensed in Cycle Compressor Aftercooler 25-HC-102 at a temperature of approx. 25°C. Liquid formed in 25-HC-102 is separated in the Cycle HP Separator 25-VA-101. The liquid from 25-VA-101 is sent to 25-VL-102 which also serves as a buffer for the heavy components of the MRC. The liquid hydrocarbon stream is routed to 25-HX-101 where it is subcooled to approx. –26°C and then, after being expanded in a Joule-Thomson valve, used for the precooling of the natural gas. The cycle gas from the separator 25-VA-101 is cooled in the precooler 25-HX-101 to the same temperature, partly condensed and fed to the Cold MRC Separator 25-VA-102. The liquid from this separator is subcooled in the liquefier 25-HX-102 to a temperature of approx. –114°C and used as refrigerant for 25-HX-102 after expansion in a Joule-Thompson valve. The vapour from this separator is condensed in 25-HX-102 and subcooled in the subcooler 25-HX-103 to a temperature of approx. –159°C and provides the cooling duty for the subcooling of the natural gas after expansion in a Joule-Thomson valve to approx. 4.7 bara. After expansion to shell pressure the cycle gas streams are warmed up in the common shell side of the cryogenic spiral wound heat exchangers and returned jointly to the suction side of the 1st stage of the Cycle Compressor 25-KA-101 via the suction drum 25-VL-101. 3.2.2
Refrigerant Storage and Make-Up
•
The make-up for the refrigerant system is required mainly due to cycle gas losses via the gas seals of 25-KA-101. The quantities required are adjusted according to the composition readings and the temperatures in the cold part and are provided via flow meters as follows:
•
Pure nitrogen is produced in the Backup Nitrogen Package 61-XT-101 and fed to the make-up header by flow control.
•
The methane rich stream is withdrawn from the discharge of the Tank Return Gas Compressor 59-KB-101 and is fed to the make-up header by flow control.
•
For first start-up, when 59-KB-101 is not in service, the gas is withdrawn downstream of the filter 20-LF-111, expanded and routed to the make-up header.
•
Ethylene is stored in the Liquid Ethylene Tank 58-VS-104. The ethylene is vaporised by the Ethylene Make-Up Heater 58-HE-101. Potential traces of water ant methanol are removed in the Ethylene Drier 58-VK-104. To avoid particles in the refrigerant cycle the ethylene is routed via the Ethylene Filter 58-LF-104 to the make-up header.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 General Description of Process and Facalities
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•
Commercial propane is stored in the Propane Tank 58-VS-101. To assure dry propane, potential traces of water and methanol are removed in Liquid Propane Drier 58-LF-101. To avoid particles in the refrigerant cycle the propane is routed via the Liquid Propane Filter 58-LF-101 to the make-up header.
•
Commercial butane and commercial pentane are stored in the Butane Tank 58-VS103 and in the Pentane Tank 58-VS-102 respectively. To assure dry butane and dry pentane, potential traces of water and methanol are removed in the Liquid Butane/Pentane Drier 58-VK-102. To avoid particles in the refrigerant cycle the butane is routed via Liquid Butane/Pentane Filter 58-LF-102 to the make-up header.
3.3
LNG Storage / LNG Loading
Main Purpose of the LNG Storage (Unit 42) and LNG Loading (Unit 47) is the intermediate storage of LNG prior to loading into LNG Carriers at the Jetty and/or to LNG Trucks at the Truck Loading Bay. The LNG Storage Tank is designed as full containment tank and stores LNG near atmospheric pressure. LNG vapour due to end flash, boil off and cooling of loading lines is routed via the LNG storage tank to the Tank Return Gas Compressors. Warm vapour return from ship and truck loading is routed via the LNG storage tank to the tank return gas compressor to protect the compressor while cold vapour return is sent directly to the compressor. Excess vapours mainly during loading of ships with increased tank temperatures at start of LNG Loading are sent to flare. 3.3.1 LNG Storage Main Purpose of the LNG Storage (Unit 42) and LNG Loading (Unit 47) is the intermediate storage of LNG prior to loading into LNG Carriers at the Jetty and/or to LNG Trucks at the Truck Loading Bay. The LNG Storage Tank is designed as full containment tank and stores LNG near atmospheric pressure. LNG vapour due to endflash, boil off and cooling of loading lines is routed via the LNG storage tank to the Tank Return Gas Compressors. Warm vapour return from ship and truck loading is routed via the LNG storage tank to the tank return gas compressor to protect the compressor while cold vapour return is sent directly to the compressor. Excess vapours mainly during loading of ships with increased tank temperatures at start of LNG Loading are sent to flare. 3.3.2
LNG Loading
There are two LNG Loading Stations foreseen: One for LNG Ship Loading at the Jetty and one for LNG Truck Loading at the LNG Truck Loading bay. 100 % of the produced LNG can be exported via LNG Carriers and approx. 10 % of the LNG production rate can be exported via LNG Trucks. LNG Ship Loading and Ship Vapour Return During LNG Ship Loading the LNG is pumped to the LNG Carriers by means of the LNG Ship Loading Pumps 42-PS-101 A/B, which are installed in the LNG Storage Tank 42-TR-101.
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The LNG from the LNG Ship Loading Pump is routed via the LNG Ship Loading Line and the LNG Ship Loading Arm 47-MU-101 to the manifold of the LNG Carrier at the Jetty. The normal loading rate of the LNG Ship Loading Pump is 1000 m³/h. The flow rate is controlled by the variable speed of the electric motor. Vapour Return from the LNG Ship will be received at a pressure of approx. 1.1 bara at the presentation flange of the ship's manifold and is routed via the LNG Ship Vapour Arm 47-MV101 and the LNG Vapour Return Line to the LNG Storage Tank 42-TR-101 or to the Tank Return Gas Compressor 59-KB-101 depending on the temperature. Warm Vapour Return is cooled to tank operating temperature by injecting LNG into the Vapour Return Line. During no ship loading operation, the LNG Ship Loading Line is kept cold by continuously circulating LNG by means of one LNG Truck Loading Pump 42-PS-102 A/B via the LNG Recirculation Line and the LNG Loading Line back to the LNG Storage Tank 42-TR-101. This is done to keep the loading system cold and gas free at all times, to allow immediate start up of ship loading after arrival of a LNG Carrier. LNG Truck Loading and Truck Vapour Return During LNG Truck Loading the LNG is pumped to the LNG Truck by means of the LNG Truck Loading Pumps 42-PS-102 A/B, which are installed in the LNG Storage Tank 42-TR-101. The LNG from the LNG Truck Loading Pumps is routed via the LNG Truck Loading Line and the LNG Truck Loading Hose 47-MU-102 to the LNG Truck at the LNG Truck Loading Bay. During loading of LNG Trucks (normal loading rate per pump: 65 m³/h) both LNG Truck Loading Pumps can be used. Vapour Return from the LNG Trucks will be received at the connection point of the Truck Vapour Return Hose 47-MV-102 and is routed via the Vapour Return Hose and the Vapour Return Line to the LNG Storage Tank 42-TR-101 or to the Tank Return Gas Compressor 59KB-101 depending on the temperature. Warm Vapour Return is cooled to tank operating temperature by injecting LNG into the Vapour Return Line. During no truck loading operation, the LNG Truck Loading Line is kept cold by continuously circulating LNG by means of one LNG Truck Loading Pump 42-PS-102 A/B via the LNG Truck Loading Line and the LNG Recirculation Line back to the LNG Storage Tank 42-TR-101. This is done to keep the loading system cold and gas free at all times, to allow immediate start up of Truck loading after arrival of a Truck.
3.4
Fuel Gas System
LNG vapour due to endflash, heat input, cooling of loading lines, ship loading and truck loading is compressed in the Tank Return Gas Compressor 59-KB-101. Part of the tank return gas is routed to the fired Hot Oil Heater as fuel gas. Approx. 2000 Sm³/h is sent to local grid as Sales Gas. For initial start-up and for backup purpose gas from the grid can be used as fuel gas.
3.5
Hot Oil System
The hot oil system supplies the process heat for the plant at two temperature levels. Two cycles are provided, a medium temperature cycle for regeneration of the amine and a high temperature cycle for the heating of the regeneration gas.
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The heat for both cycles is provided by the Fired Hot Oil Heater 52-FA-101, a direct fired heater supplied by fuel gas. In this heater the hot oil is heated to approx. 260°C to supply heat for the Regeneration Gas Heater 20-HA-111. This high temperature cycle is pressurized by the Hot Oil Cycle Pump I 52-PA-101 A/B. The required heat for the regeneration of the amine in the Amine Strip Column Reboiler 20-HA-102 is withdrawn from the high temperature cycle downstream of the Hot Oil Cycle Pump I 52-PA-101 and mixed with the cold hot oil downstream of Hot Oil Cycle Pump II 52-PA-102 A/B to limit the maximum temperature to 190°C to avoid degradation of the amine solvent. The hot oil leaves 20-HA-102 with a temperature of approx. 145°C and approx. A small fraction of the flow is pressurized by the Hot Oil Cycle Pump II 52-PA-102 A/B. Most of the hot oil leaving the Amine Strip Column Reboiler 20-HA-102 enters the first hot oil cycle via the balancing line. The balancing line between the two cycles is also used to provide sufficient suction pressure for the two pumps via the Hot Oil Expansion Drum 52-VL-101. The Hot Oil Surge Drum 52-VS-101 is provided to store the total inventory of the system in case of filling or maintenance, and a small Hot Oil Filling Pump 52-PA-103 serves to ease filling of the system. Blanketing for the Hot Oil Unit will be done with pure nitrogen.
3.6
Flare System
The Plant is equipped with two flare headers: •
warm gas flare header which ties in directly at the Flare Stack 54-FC-101
•
cold gas and liquid flare header including the Blow Down Vessel 54-VD-101 for separation of cold liquid and vapour. The vapour is routed to the bottom of 54-FC-101. The liquid is vaporised in the uninsulated Blow Down Vessel 54-VD-101 by ambient heat. In case a warm liquid remains, this liquid can be discharged manually to a barrel.
In addition the low pressure gas from tank and ship loading is routed to the top of the Flare Stack 54-FC-101.
3.7
ESD and Blowdown System
The Emergency Shutdown, Isolation and Depressuring System is used to prevent escalation and to minimise leakage of flammable fluids in case of major plant malfunctions, emergency conditions or damage. The main purpose is to minimise damage by hazards such as fires, unconfined vapour cloud explosions (UVCE) or a boiling liquid expanding vapour explosion (BLEVE) due to bursting vessels. Those hazards may follow on excessive leakage of flammable fluids. After a leakage or fire is detected and localised by the fire and gas alarm system and indicated in the central control room, the Emergency Shutdown, Isolation and Depressuring System will be activated via push-buttons by the operator from CCR. After activation, the plant will be blocked in automatically by means of remote-actuated valves (e.g. Emergency Shutdown Valves - ESV) and selected rotating equipment (eg cycle compressor) will be shut-down. Subsequently the Emergency blow-down System can be activated by the operator. The Emergency blow-down System is depressurising the whole plant (exclusive of LNG-Tank) to the flare system by remote actuated Blow-down Valves (BDV). The system can be operated from a separate control panel (ESD panel) in the central control room (CCR) and allows remote actions from safe location in case of emergency.
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Stop Feed, Energy Input and Export Streams For the LNG process plant all feed streams and energy inputs into the depressurizing areas can be shut off. Units transferring energy to a safe place are kept in operation for continuous energy removal. All export streams (e.g. tail gas) will be shut-off. Depressurizing Philosophy According to contract and EN 1473, the isolated sections shall be depressurised to •
50 % of design pressure in 15 minutes or to
•
7 barg in 30 minutes
The higher flow is counting. Units and Equipment without Depressurizing Facilities Basis for selection of depressurizing sections is the maximum operating or settle out pressure and not the mechanical design pressure, which is for other reasons sometimes well above the maximum operating pressure (compare API RP 521). The following units and equipment have no depressurizing facilities: •
MDEA regeneration; operates at low pressure (appr.1 barg)
•
Feed gas Liquefaction passage in 25-HZ-101 (mass of each passages is below 1000 kg limit, the passage is well protected in the shell, the consequence is considerably low)
•
LNG storage; operates at low pressure (appr. 250 mbarg)
•
LNG Ship, LNG piping and LNG Truck Loading system (subcooled liquid at low pressure)
Basis input to QRA As basis for the QRA a reaction time from first fire&gas alarm until the operator initiates the ESD and blowdown system is assumed to be 600 seconds. As an average value a depressurisation time of 900 seconds shall be used in the QRA (refer to Assumption Sheet RA-4 in Appendix A).
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4.0
4.1
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Study Methodology
Risk Analysis Basics
Risks are commonly incurred and accepted in everyday life. There are many different types of risk including risk to life and health, risk to the environment and economic risks, which may impair the survival of a company. The risk R is commonly described by its two dimensions, i.e. the consequence of an accidental event C and the frequency of this event (F): R=CxF The actual risk values can be manifold due to the different types of consequences, which might arise from an accident. It could be a financial loss due to downtime and damage in terms of money per event, a certain number of fatalities or certain damage to the environment, which may also lead to a certain financial loss due to the cost resulting from decontamination etc. The economic loss is very often influenced by the fact that certain accidents will lead to damages in the neighbouring parts of the plant. The frequency of an event usually is a composite magnitude, e.g. for an ignited gas leak the primary leak frequency will be multiplied by the conditional probability of igniting the gas cloud resulting from the leak. Under certain conditions, even more conditional probabilities may factor into this product to yield the total frequency of a certain event, e.g. the probability of in-time detection of a flammable cloud or the conditional probability, that certain isolation measures (e.g. ESD and Blowdown System) work, when required.
4.2
Definition and Types of Risk
It has become common in the process industries to quantify risk to people in terms of •
1st party risk, i.e. the risk to onsite personal
•
2nd party risk, i.e. the risk to external contractors
•
3rd party risk, i.e. the risk, to which the site external population is exposed.
Further to this one differentiates individual risk, i.e. the risk, to which a single person is exposed, and societal or group risk, i.e. the risk to which a certain group of people are exposed. Details are given in Table 3. Table 3: Types of Risk Type of Risk 1st party individual specific risk
Details Risk to onsite personnel, based on the most exposed person at risk, i.e. operators.
1st party average individual risk
Risk based on the individual specific risk and is calculated as average risk to onsite personnel.
2nd party individual specific risk
Risk to external contractors, based on the most exposed person at risk, i.e. LNG carrier, external maintenance personnel.
2nd party average individual risk
Risk based on the individual specific risk and is calculated as average risk to external contractors.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Study Methodology Type of Risk 3rd party individual specific risk
Societal (3rd party) risk
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Details Risk to offsite population expressed as the fatality risk per year. Individual risk is calculated under the assumption that the exposed person is present unprotected at the same location for 24 hours per day over 365 days per year. In case of Individual Specific Risk the actual duration of the presence is taken into account. Risk to a group of people outside of the plant. Societal risk usually is quantified in form of the so-called FN curve, specifying the frequency F (per year), that N or more persons are affected by lethal consequences.
Acceptance Criteria
The risk in this QRA study is discussed in terms of individual risk and societal risk. The Individual Specific Risk for 1st, 2nd and 3rd party has been defined by Lyse. The 3rd party risk is also calculated as FN Curve and compared with the societal risk acceptance criteria based on UK HSE Societal Risk Criteria. The acceptance criteria defines for the following personnel categories: •
1st party, i.e. personnel working for the Lyse LNG Base Load Plant facility.
•
2nd party, i.e. LNG Carrier personnel (Truck, Ship Loading and external contractors) can be affected by operation activities.
•
3rd person, i.e. offsite population.
Note: occupational accidents have been not included in the acceptance criteria and therefore are not considered in the QRA. 1st and 2nd party Individual specific risk (ISR) is specified as ISR = Σ (Effective Frequency x Occupancy x Vulnerability), where "Occupancy" is a factor which relates the time for which a person is exposed to work hazards (in hours) to the total number of hours within a year (8760). For sake of simplicity we assumed, that a typical operator works in 8 hour shifts for 5 of 7 days per week, i.e. his annual working hours are 45 weeks x 5 days x 8 hours = 1800 hours per year. He is 20% of his working time outside. The effective frequency is calculated 0.2 x outdoor frequency + (1-0.2) x indoor frequency. Hence the occupancy factor is 1800 / 8760 = 0.20. For the definition of vulnerability please refer the Appendix F. The acceptance criterion for Individual Specific Risk (ISR) for the most exposed person for 1st and 2nd party is expressed as the yearly probability for loss of life. The ISR is acceptable for < 1 X 10-6 per year, the risk level above 1 X 10-3 per year becomes unacceptable. The region in between is the ALARP area. The Average Individual Risk (AVR) is specified as follows: AVR = Σ (ISR x Number of personnel) / Σ Number of personnel The AVR shall not exceed 1 X 10-4 per year, the risk level under 1 X 10-6 per year is acceptable. The region in between is the ALARP area.
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If no individual specific risk (ISR) is found to be above 1 X 10-4 per year, the AVR criteria is fulfilled. 3rd party (Societal Risk) Individual specific risk (ISR) is specified as ISR = Σ (Effective Frequency x Occupancy x Vulnerability), where "Occupancy" is a factor which relates the time for which a person is exposed to hazards (in hours) to the total number of hours within a year (8760). For sake of simplicity we assumed, that a person on the peninsula stays for 4 hours 2 of the 7 days per week in the summer (4 month) and 2 hours at 2 days per week in the winter, i.e. his annual presence hours are (16 weeks x 2 days x 4 hours) + (32 X 2 days X 2 hours) = 256 hours per year. He is staying 100% outside. The effective frequency is calculated with a location fraction of 1 outdoor frequency. Hence the occupancy factor is 256 / 8760 = 0.03. The acceptance criterion for Individual Specific Risk (ISR) for the most exposed person for 3rd party is also expressed as the yearly probability for loss of life. The ISR is acceptable for < 1 X 10-7 per year, the risk level above 1 X 10-5 per year becomes unacceptable. The region in between is the ALARP area. The Average Individual Risk (AVR) is specified as follows: AVR = Σ (ISR x Number of people) / Σ Number of people The AVR shall not exceed 1 X 10-5 per year, the risk level under 1 X 10-7 per year is acceptable. The region in between is the ALARP area.
Societal risk for 3rd party is presented as the probability or frequency of accidents of different extent. The Figure 5 below states the acceptable and not-acceptable range of the yearly frequency (F) – consequence (number of fatalities N or larger) – diagram and shows the acceptance criterion based on UK HSE Societal Risk Criteria. It also indicates an area where the company shall actively seek to reduce the risk based on the ALARP principle.
Figure 5: UK HSE Societal Risk Criteria
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Hazard Identification
The study has been based on identified major inventories of flammable and explosive materials in the LNG Base Load Plant units, together with major lines connecting the inventories. Information on inventories, stream compositions, operating conditions and locations has been based on the available drawings and further information. In addition the results of the hazard identification of Hazard Study (HAZID) (Appendix B) were used. The investigations were verified on the basis of operating procedures, P&IDs and the knowledge provided by LINDE. In the HAZID, only those hazards are identified, which might lead to a leakage of hydrocarbons and a subsequent fire or explosion. Other hazards with operational consequences have been discussed in the normal HAZOP study. The basic results of the HAZID are shown in Table 4 . Table 4: HAZID Summary Hazard Hydrocarbon (gas / liquid or two phase) leaks outdoors
Hydrocarbon (HC gas / liquid or two phase) leaks in buildings
Non-hydrocarbon fire Non hydrocarbon chemical leak or fire
Loss of power Loss of instrument air Loss of safety systems Loss of control system
Treatment in QRA Included in QRA in four event classes of very large, large, medium and small leak at various locations in the individual areas. This hazard covers the majority of flammable leakage scenarios. Not included in the QRA Buildings containing HC: - The buildings are specified with explosion group zone 1; therefore the risk of internal explosion is reduced. - The protective effect of the building is not considered in the SAFETI calculation (conservative consideration). Buildings containing no HC: - Gas entering in a building is presented by adequate gas detection and closing the air-intake. Not included in the QRA as of minor importance. Involved chemicals (e.g. MDEA etc.) have a minor contribution to risk due to quantities; hence they are not of relevance in this QRA. Not included in the QRA since failure leads to fail safe conditions. Not included in the QRA since failure leads to fail safe conditions. Not included in the QRA since failure leads to fail safe conditions. Not included in the QRA since failure leads to fail safe conditions.
Occupational accidents
Not included in the QRA as this is identical to general petrochemical facilities and known to be marginal
Natural environmental impact (extreme weather, earthquake, etc) Pipeline rupture
Not included in the QRA due to low risk contribution.
Pipeline exposed/free span
Included as a potential cause for leaks.
Pipeline dented Excessive pipeline expansion
Included as a potential cause for leaks. Included as a potential cause for leaks.
Included in the QRA.
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Study Methodology Hazard Reduced pipeline thickness
Treatment in QRA Included as a potential cause for leaks.
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Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Data used for the Risk Assessment
5.0
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Data used for the Risk Assessment
This section informs about the basic data and detailed assumptions which were used for the calculations and the individual steps taken to arrive at the risk picture.
5.1
Scenarios
For the purpose of this QRA the plant was analysed with respect to its hydrocarbon content. Units without relevant hydrocarbon content were excluded from the further analysis. These scenarios consider releases of hydrocarbons from small, medium, large or very large leaks in pipe work or equipments. This leaves the following units for further consideration as shown in Table 5 and Figure 6: Table 5: Units covered in this QRA Unit
Inventory Loop No. used in fig. 6
Designation
20
IL1
Feedgas Purification
20
IL2A
NG Liquefication Gas
25
IL2B1
NG Liquefication Liquid_103 bar System
25
IL2B2
NG Liquefication Liquid_19 bar System
59
IL3A
LNG Storage Return Gas
42
IL3B
LNG Storage
47
IL4
LNG Truck Loading
47
IL5A
LNG Ship Loading Tank Top
47
IL5B1/2/3
LNG Ship Loading Line
47
IL5C
LNG Ship Loading Jetty
25
IL6A1
Refrigeration Gas System_4 bar System
25
IL6A2
Refrigeration Gas System_18 bar System
25
IL6A3
Refrigeration Gas System_40 bar System
25
IL6B1
Refrigeration Liquid 25-HX-101/103 System
25
IL6B2
Refrigeration Liquid 25-VA-101 System
25
IL6B3
Refrigeration Liquid 25-VA-102/25-HX-102 System
25
IL6B4
Refrigeration Liquid 25-VL-102 System
58
IL7
Propane Storage
58
IL8
Pentane Storage
58
IL9
Butane Storage
58
IL10A
Ethylene Storage Gas System
58
IL10B
Ethylene Storage Liquid System
20/52
IL11
Hot Oil System
15
IL12
Feedgas Fiscal Metering
59
IL13
Tailgas Fiscal Metering
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The solvent regeneration system has not been taken into account in this QRA due to its comparably small inventories. A leak of MDEA from process equipment or piping leads to a release of CO2 loaded MDEA to dike area and pit, which does not impose a relevant hazard to people. The units can be isolated by ESD and Blowdown system or are directly connected to another area, which can be isolated.
Figure 6: Process Areas defined for this QRA (numbers see Table 5)
For these areas an equipment count was performed (refer to Assumption Sheet FA-1 in Appendix A) and considering: • • • •
Equipment (vessels, pumps, heat exchangers, compressors etc.) Valves (actuated and non-actuated) Pipelines Small bore fittings, Flange connections (partly, based on the Dutch Purple Book [5])
All equipment has been listed with their respective operating characteristics. These data have been used to calculate the overall leak rates for the individual areas. Details are contained Appendix C.
5.2
Leak Frequencies
The leak frequency modelling is based on DNV’s leak frequency database LEAK 3.2 and Purple Book. The leak types and sizes are shown in Table 6:
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Table 6: Leak types and sizes Leak Type Small Medium Large Very Large (Full Bore Rupture)
Leak range [mm] 1 – 10 10-50 50-100 > 100
Leaks with equivalent diameter below 1 mm are not considered as they do not contribute substantially to the overall risk.
5.3
Release Duration
The duration of a release is closely linked to the type of detection and isolation. Table 7 lists typical times involved for various alternatives: Table 7: Typical Duration Times based on DNV database Description
Duration for Detection and Isolation [s] Gas detector which auto closes ESD/automatic valve (XSFV). 120 Gas detector with isolation by manual valve closure. 960 Gas detector with isolation by remotely operated closure of control valve. 660 Detection by operator and initiation of ESD & Blowdown System 600 Gas detector with isolation by remotely operated closure of ESD. 360 Process trip which auto closes ESD. 360 Process alarm with isolation by manual valve closure. 1200 Process alarm with isolation by remotely operated closure of control valve. 900 Process alarm with isolation of feed by remotely operated closure of control max. 1800 valve. Duration determined by either inventory of material (max 1800s) or valve closure time (900s). Process alarm with isolation of feed by remotely operated closure of ESD. max. 1800 Duration determined by either inventory of material (max 1800s) or valve closure time (600s). Process alarm with isolation by remotely operated closure of ESD. 600 Detection by field operator, remote area, with manual isolation. 2700 Detection by field operator, remote area, with isolation by remotely operated 2400 control valve. Detection by field operator, remote area,, with isolation by remotely operated 2100 ESD. Detection by field operator routine patrol, with manual isolation. 1500 Detection by field operator routine patrol, with isolation by remotely operated 1200 control valve. Detection by field operator routine patrol, with isolation by remotely operated 1200 control valve. Duration determined by either inventory of material (max 1800s) or valve closure time. Detection by field operator on routine patrol with isolation of feed by remotely 900 operated closure of ESD. Duration determined by either inventory of material (max 1800s) or valve closure time. Detection by field operator on routine patrol, with isolation by remotely operated 900 ESD.
The Lyse LNG Base Load Plant is equipped with a fire and gas detection system and remotely operated ESD valves, control valves, compressor and pumps. The reaction time is 600 s for
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detection and initiation of ESD & Blowdown System by the operator, e.g. shut-off of main feed and product streams via ESD valves and tripping of main machines. An average blowdown time of 900 s is used in the calculation (refer to Assumption Sheet HC-2 and RA-4 in Appendix A).
5.4
Atmospheric Conditions
Weather data have been taken from the site conditions document [6]. For the wind rose data for Sola, refer to Assumption Sheet MI-2 in Appendix A. Table 8 summarises the results, where an angle of 0 degrees presents a wind originating from the North. Table 8: Weather data for Lyse LNG Base Load Plant Stability Class Wind [m/s] F - 1.5 D- 6 D - 12 Sum
Percentage Wind direction [degrees] 292.5337.5 22.5337.5 -22.5 67.5 1.99 0.961 1.012 14.71 7.09 7.47 2.79 1.346 1.417 19.49 9.397 9.899
67.5112.5 1.633 12.04 2.293 15.966
112.5157.5 1.335 9.89 1.878 13.103
157.5202.5 0.501 3.69 0.702 4.893
202.5247.5 0.807 5.96 1.13 7.897
247.5292.5 1.977 14.57 2.76 19.307
Wind speed classes have been used ranging from 1.5 m/s to 12 m/s, whereas for atmospheric stability Pasquill classes ranging from D (neutral) to F (stable) have been selected. The atmospheric stability is considered to be neutral during the day and stable during the night. For the calculations 8 wind directions have been used.
5.5
Population Distribution
For the Lyse LNG Base Load Plant facility, a work day is divided into three shifts; a day shift, an afternoon shift and a night shift, each lasting 8 hours (Assumption Sheet MI-3 in Appendix A). The relevant figures listed in Table 9 and Table 10:
Table 9: Onsite Population (1st and 2nd party) Buildings / Areas Administration Building Maintenance Truck Loading Ship Loading (Jetty) Ship Deck Ship Bridge
Personnel / People Day (per Shift) Night Total Number 3 1 7 2 1 5 4 2 10 1 1 3 2 2 6 8 8 24
The personnel in the administration building do the daily operation and supervision of the plant. Table 10: Off-site Population (3rd party) Areas Peninsula Hiking Track Ferry Terminal_office workers
Personnel / People Day Night 16 (in non-work day) 0 8 (in a non-work day) 0 100 2
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Data used for the Risk Assessment Areas Ferry Terminal_industry workers Ferry Terminal_passengers Energiveien+Risavika_office workers Energiveien+Risavika_industry workers Container Area_office workers Container Area_industry workers Rest Companys_office workers Rest Companys_industry workers Living Quarters
5.6
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Personnel / People Day Night 10 0 1500 0 400 5 559 0 10 1 50 0 1139 10 715 0 60 60
Ignition Sources
Release of flammable fluid may have many event outcomes, depending on the timing and type of ignition. For example, a release may ignite immediately at the point of release, or it may ignite after the cloud has been dispersing for two minutes, or after the cloud has been dispersing for five minutes, or it may not ignite at all. If it ignites, it may give either explosion effects or different types of fire effects depending on the type of release (e.g. jet fire, fireball, pool fire or flash fire). Each of the outcomes will have different risk effects because each produces an effect zone of a different size and intensity, at a different location. The risk effects for a flammable release will depend on the timing, location and nature of ignition. For example, if an instantaneous release ignites immediately it will produce a hazard zone at the point of release, whereas if it ignites after the cloud has started to disperse, it will produce a hazard zone at the point of ignition. If the ignition produces a fireball, the intensity of the effects within the zone will be different from those for an ignition which produces a flash fire, or for an ignition which produces an explosion. The different outcomes are presented in the form of event trees (Assumption Sheet RA-1 in Appendix A). Each outcome in an event tree can be assigned a probability, and the program performs the risk calculations for all of the event tree outcomes that are relevant to a particular flammable model. The ignition probability within PHAST RISK is definable according to the respective site knowledge. The immediate ignition probability is directly specified. A default value of 0.3 is used, which would only apply to very large flammable gas releases in a large industrial complex. The delayed ignition probability for any failure case is a calculated value within PHAST RISK, which is based on the defined ignition sources on site, with a unique value for each release case and release direction. The calculation is based on the strength, location and presence factor of all ignition sources specified, and the size and duration of the dispersing flammable vapour cloud. PHAST RISK assumes "diffuse ignition background" (which could be understood as e.g. traffic illumination, cameras etc.), i.e. ignition may occur even if no specific ignition sources are given. Plant specific ignition sources, which have been taken into account are listed in Table 11 and their ignition probability have been discussed in Assumption Sheet RA-2 Appendix A.
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Table 11: Ignition Sources in Lyse LNG Base Load Plant Ignition Source Flare 54-FC-101 Fired Heater for Hot Oil 52-FA-101 Regenerative Thermal Oxidation (RTO) (Incinerator) 20-XT-101 Electrical Substation Traffic (Truck Loading) Parking External Population
To model the conditional probabilities for the ignition resulting into different types of fires and explosion, an event tree of the type shown in Figure 7 has been used:
Figure 7: Event tree used for fire and explosion modelling
For the probabilities in this event tree, standard setting as used normally in PHAST RISK have been applied (most values taken from the Dutch Purple Book [5]).
5.7
Consequence Calculations
The analysis of potential consequences following loss of containment is carried out as the first stage of the risk analysis. Consequence analysis involves the estimation of rates of release in the event of loss of containment and prediction of the potential consequences. 5.7.1
Discharge and Dispersion
Material can be released to the atmosphere because of a failure in the containment system. The magnitude of a release depends primarily on the size of the leak in the system, the phase of the material and the operating pressure. For modelling purposes, releases are usually categorized as either instantaneous or continuous. As the analysis is concerned with major acci-
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dent hazards, only releases from equipment and releases from holes giving an excess of a release rate of 0.1 kg/s have been included. 5.7.2
Instantaneous Releases
If a catastrophic failure of the shell of a vessel occurs the contents would be released very quickly (instantaneously). This type of failure has been modelled as a hemispherical cloud centred on the release location. 5.7.3
Continuous Releases
Releases of liquids and gases from pipes or equipment items were estimated using basic release rate calculations assuming a fixed value of discharge coefficient. The value of discharge coefficient used (0.65) is taken from a range of values (typically 0.5 to 0.8) which represent various pipe- and equipment configurations. The release rate calculations were performed using PHAST 6.53.1. The calculated release rate was assumed to be constant throughout the release duration. 5.7.4
Release Duration
The release duration depends on the upstream inventory and the means for detection and subsequent isolation of the release. The release duration has been assumed (refer to Assumption Sheet RA-4 in Appendix A) to be limited by the upstream inventory up to a maximum duration of 1500 s (600 s detection time and 900 s automatic or remotely activated ESD and Blowdown closure time) for small and medium sized leaks. For large and very large leaks an isolation time of 600 s has been used. By all size of leaks, the rest flow of fluids from the upstream system, which will be released before the isolation valves closes (in 600 s), is also considered in the PHAST calculation. 5.7.5
Dispersion
When a vapour cloud is generated, either instantaneously or continuously, there may be a substantial degree of mixing of air with the released material. Dispersion was modelled using PHAST version 6.53.1. To allow for destruction of momentum due to impingement of releases or upwind and downwind releases, 50% of releases were modelled as free-field horizontal releases and 50% were modelled as ‘impinged’ releases. The dimensions of impinged releases were determined assuming that the clouds were cylindrical in shape, but with the same volume as a horizontal release. 5.7.6
Thermal Radiation and Overpressure
On ignition of a flammable cloud, different types of combustion can occur depending on the particular circumstances. It is normal to characterize the combustion in various ways and for the purpose of this analysis, flash fires, jet fires, pool fires, fireballs and explosions have been considered. In the event of a flammable release from containment which is not ignited immediately, a hydrocarbon vapour/air mixture is formed. The concentration of hydrocarbon in the cloud, as progressive dilution with air takes place, is estimated using the dispersion model. The direction and extent of drift of the cloud is influenced by the prevailing weather conditions. The cloud
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remains capable of ignition providing the concentration is above the lower flammable limit (LFL). On ignition, a flame front passes at slow speed throughout the flammable cloud and a flame stabilizes near to the point of release as either a jet or pool fire. A flash fire does not produce high levels of overpressure outside the cloud, but inside the cloud there can be isolated regions of overpressure which could lead to equipment or building damage. Levels of thermal radiation which are potentially fatal, are produced within, and for a very small distance outside the LFL envelope. Jet fires are usually the consequence of a momentum dominated release resulting from an immediately ignited release or from a flash fire that burns back to the point of release. This type of fire has been included in the SAFETI calculations. Under certain circumstances the flame travelling through a hydrocarbon/air cloud can accelerate and attain a significantly higher flame speed than that associated with a flash fire. This high flame speed also generates an overpressure wave. This phenomenon is referred to as a vapour cloud explosion (VCE). Experimental work and observations on incidents have confirmed that in order for a flame to accelerate from a low speed to a high speed, some form of congestion is necessary, e.g. a gas cloud within a plant area. Flame acceleration does not occur if the cloud is in the open air, e.g. a cloud over open ground, and indeed if a high speed flame exits from a congested region into an open region, flame deceleration occurs. Vapour cloud explosions are characterized by the production of levels of overpressure which can cause damage to equipment and destruction of buildings well beyond the flammable cloud boundary. Although any person within the flammable cloud is likely to be fatally injured, direct human fatalities from blast outside the flammable cloud are unlikely. Most casualties beyond the cloud envelope arise indirectly, i.e. from crush injuries in collapsed buildings or injuries from fragments. PHAST RISK uses a modified version of the TNT equivalent model to describe the consequences of VCE. This model considers a typical congestion. As there is unconfined space between the process area and the administration building, the results for explosion overpressure towards the administration building and installation outside battery limit can be considered conservative.
5.8
Mitigation Measures taken into Account
The present concept takes into account various mitigation measures, which are presented in the Assumption Sheets as indicated in Table 12:
Table 12: Risk Reducing Measures No.
Risk Reducing Measure
1
Loading frequency consideration
Assumption Sheet No. HC-9
2
Welded Pipes in Feed Gas and LNG service
FA-1
3
Full containment LNG Storage Tank
FA-3
4
Explosion Protection
RA-2
5
Design of the flare stack
RA-6
6
Fire and Gas Detection
RA-3
7
ESD/Blowdown System
RA-4
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No.
Risk Reducing Measure
8
Appropriate measures
Assumption Sheet No. RA-2, RA-6
9
Active and Passive Fire Protection
RA-7
10
Escape Ways
RA-8
11
Safe Haven
RA-8
For further reduction of the risk to ALARP additional risk reduction measures are evaluated by means of sensitivity calculations in Chapter 7.0.
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6.0
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Results of the Risk Analysis
This section presents the results of the risk calculations using PHAST RISK with the assumption specified in the previous sections. Risk to people is described in terms of individual risk for 1st, 2nd, 3rd party and societal risk 3rd party.
6.1
Risk 1st and 2nd party
Individual Risk, 1st and 2nd party The subsequent Figure 8 and Figure 9 show the calculated individual risk contour lines for the Lyse LNG Base Load Plant. The figures 8 and 9 show the calculated individual risk contour lines for the Lyse LNG Base Load Plant. The calculated risk contours of individual risk for the most exposed person is illustrated in Figure 8. The figure shows the contours of the most exposed person to suffer a fatality every 100 000 years (green line), every 1 000 000 years (dark blue line). The risk is illustrated for the most exposed person present in the process plant area, 20 % of their working time per year.
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10-5 /yr 10-6 /yr
Figure 8: Most exposed person individual risk contour lines for the Lyse LNG Base Load Plant
The risk contours for the individual risk are also calculated and is illustrated in Figure 9. The figure shows the contours of individual risk for a fatality every 10 000 years (green line), every 100 000 years (dark blue line), etc. The risk is illustrated for 1 person present at any point outside a building in the plant, continuously 8 hours a day, 5 days a week during a whole year (45 weeks).
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10-4 /yr 10-5 /yr 10-6 /yr 10-7 /yr 10-8 /yr
Figure 9: Individual risk contour lines for the Lyse LNG Base Load Plant
The figure shows the contours of individual risk for a fatality every 10 000 years (green line), every 100 000 years (dark blue line) etc. The risk is illustrated for 1 person present at any point outside a building in the plant, continuously 8 hours a day, 5 days a week during a whole year (45 weeks). The risk is higher closer to the process area and above 1 fatality every 10 000 years. The other plant areas, e.g. LNG Tank is between the 1 fatality per 10 000 year and 100 000 year risk contour. The frequency of overpressure at the control room is calculated [refer Chapter 6.4]. The Central Control Room is designed for an explosion load of 200 mbar. The risk contributions (pies) for 1st and 2nd party are illustrated in Figure 10, Figure 11, Figure 12 and Figure 13 and based on calculated individual risk (IR) and include gas and liquid leaks from all leak sizes of the various inventory loops, which are indicated in the risk ranking report (ref. Appendix E) and reflect the indoor (respectively outdoor) risk that the exposed person is present unprotected at the same location for 24 hours per day over 365 days per year.
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IRindoor = 4.9 X 10-8 /yr Other 1%
LNG Ship Loading Jetty 43%
Refrigerant System 56%
Figure 10: Risk contributors to personnel in administration building
Propane Storage 7%
Other 5%
IRoutdoor= 2.9 X 10-3 /yr
Ethylene Storage 6%
Pentane Storage 7% Refrigeration System 47% Butane Storage 6%
Feedgas Purification 22%
Figure 11: Risk contributors to personnel in process area
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Data used for the Risk Assessment
Butane Storage 3%
Other 6%
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IRoutdoor= 9.9 X 10-4 /yr
Propane Storage 10%
Feedgas Purification 47%
Refrigeration System 23%
Ethylene Storage 11%
Figure 12: Risk contributors to personnel at jetty
IRoutdoor= 8.2 X 10-4 /yr
Other 9%
LNG Storage Tank Top 4%
Refrigerant System 11%
Feedgas Purification 46% Ethylene Storage 6%
Propane Storage 6%
Truck Loading 18%
Figure 13: Risk contributors to personnel at truck
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The main individual risk to onsite personnel comes from the refrigerant system and feedgas purification. Individual Specific Risk, 1st and 2nd party The Individual Specific Risk (ISR) for 1st and 2nd party, which considers the individual working hours for each group, is given below in Table 13. Table 13: Individual Specific Risk (ISR) for 1st and 2nd party Buildings/Personnel Locations Operator
ISR [year] 1.2 X 10-4
Process Area (Maintenance)
1.2 X 10-4
Truck Loading
6.7 X 10-5
Ship Loading (Jetty)
2.0 X 10-5
Ship Bridge
5.0 X 10-5
Ship Deck
4.8 X 10-5
Criterion (ISR)
1 X 10-3
The most exposed 1st party person will be an operator. He is presumed to be 20% of his time in the process area and exposed to a potential accident when he is at work, i.e. 1800 hours per year. The “indoor” individual risk in administration building is 4.9 X 10-8 per year. The “outdoor“ individual risk in process area is 2.9 X 10-3 per year. The Individual Specific Risk is calculated by the following equation, (0.2 x 2.9 X 10-3) + (0.8 x 4.9 X 10-8 ) X 1800/8760 = 1.2 X 10-4 per year. Hence the 1st party individual specific risks for the most exposed person lower than 1 X 10-3 per year and within the acceptance criteria. The Average Individual Risk (AVR) of 5.0 X 10-5 per year for all personnel (1st and 2nd party) is within the ALARP regime.
6.2
Risk 3rd party
Individual Risk, 3rd party The distribution of the external population (3rd party) is shown in Figure 14:
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Residential Area
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Living Quarters En er giv eie n+ Ri sa Co vik nt a Ar ain ea er
Rest Companys
Ferry Terminal Peninsula
Hiking Track
Figure 14: Representative external population (Peninsula, Hiking Track, Ferry Terminal, Container Area, Energiveien&Risavika, Rest Companys, Residential Area and Living Quarters)
Figure 15 shows the Lyse LNG Base Load Plant location.
LNG plant location
LNG plant location
Figure 15: The LNG Base Load Plant location
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The risk contributions (pies) for 3rd party are illustrated in Figure 16, Figure 17 and Figure 18 and based on calculated individual risk (IR) and include gas and liquid leaks from all leak sizes of the various inventory loops, which are indicated in the risk ranking report (ref. Appendix E) and reflect the indoor (respectively outdoor) risk that the exposed person is present unprotected at the same location for 24 hours per day over 365 days per year.
IRoutdoor= 7.6 X 10-5 /yr
Propane Storage 38%
Other 6%
Refrigeration System 15%
Ship Loading Tank Top 22%
Butane Storage 2% Pentane Storage Ship Loading Jetty 4% Feedgas Purification Ethylene Storage 2% 5% 6%
Figure 16: Risk contributors to people at Peninsula and Hiking Track
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IRoutdoor= 7.9 X 10-6 /yr
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Other 9%
Truck Loading 6%
Refrigeration System 27%
Ship Loading Jetty 4%
Feedgas Purification 9%
Ethylene Storage 9% Ship Loading Tank Top 14% Pentane Storage 6% Propane Storage 16%
Figure 17: Risk contributors to other external population (Ferry Terminal, Container Area, Energiveien&Risavika, Rest Companys and Living Quarters)
The main individual risk to offsite personnel comes from the LNG storage tank top (ship loading tank top), refrigerant system and propane storage.
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IRoutdoor= 9.7 X 10-10/yr
Ship Loading Tank Top 49%
Refrigeration System 51%
Figure 18: Risk contributors to the Residential Area
Individual risk for people in residential area is negligible (9.7 X 10-10 per year). Worst case assessment shows, there is no credible scenario that a flammable gas cloud above LFL (lower flammable limit) can reach the residential area. Individual Specific Risk, 3rd party The Individual Specific Risk (ISR) for the 3rd party risk is given below in Table 14.
Table 14: Individual Specific Risk (ISR) for the 3rd party Personnel Locations Peninsula
ISR [year] 4.6 X 10-8
Hiking Track
2.2 X 10-6
Ferry Terminal_office workers
7.6 X 10-7
Ferry Terminal_industry workers
3.8 X 10-7
Ferry Terminal_passengers
4.0 X 10-7
Energiveien+Risavika_office workers
4.6 X 10-9
Energiveien+Risavika_industry workers
4.6 X 10-9
Container Area_office workers
3.2 X 10-9
Container Area_industry workers
3.2 X 10-9
Rest Companys_office workers
2.8 X 10-14
Rest Companys_industry workers
2.8 X 10-14
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Data used for the Risk Assessment Personnel Locations Living Quarters
ISR [year] 3.5 X 10-10
Criterion (ISR)
1 X 10-5
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The Average Individual Risk (AVR) of 1.5 X 10-7 per year for people living, working or staying outside the Lyse LNG base load plant does not exceed the acceptance criteria of 1 X 10-5 / year and is within the ALARP regime, close to acceptable in general. Societal Risk, 3rd party The societal risk calculated for the Lyse LNG Base Load Plant is shown in Figure 19.
Figure 19: Societal risk FN curve for the Lyse LNG Base Load Plant
The minimum and maximum risk criteria are shown in Figure 19 as blue and green lines respectively. Calculations of the external societal risk (e.g. Hiking Track, Peninsula, Industry Area and Ferry Terminal) have shown that this risk for the Lyse LNG Base Load Plant falls into the
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area between the upper and lower limit line, i.e. the ALARP regime. For the Lyse LNG Base Load Plant such mitigation measures have already been applied (refer to Chapter 5.8 and 7.0).
6.3
Location Specific Risk
It has been suggested by Skangass, that the location of the 1 X 10-5 per year contour is a suitable measure to use for the outer extent of a “safety zone” around the site. Certain activities, such as smoking, starting open fires and camping would not be allowed in this region. Such a designation is consistent with the use of the 1 X 10-5 per year contour by the HSE in the UK to mark the extent of the “inner zone” around a site where future residential developments would be prohibited. Figure 20 shows in relation to the safety zone the 1 X 10-5 per year risk contour.
safety zone contour 10-5 /yr (individual risk contour)
Figure 20: Location of safety zone in relation to the calculated individual risk contour of 1 X 10-5 per year
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6.4
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Overpressure Risk
To assess the effectiveness of mitigation measures, overpressure risk contours are calculated for the potential overpressure design in the Lyse LNG Base Load Plant. In view of the probabilistic nature of a QRA, also peak overpressure reached at a certain location will occur at this location with a certain frequency (per year), i.e. overpressure is of probabilistic nature itself. Therefore overpressure risk calculations have been performed using PHAST RISK. Peak overpressure is of relevance for the design of buildings, in which personnel will be protected against the consequences of pressure waves. Depending on the design and reinforcement of the building it will provide more or less protection for people. In Reference 7 and 8, overpressure fatality probabilities for various peak overpressures have been determined for various building types (so-called BEAST and CIA types). The selection of the respective pressure to be considered is motivated by the vulnerabilities of populations in various building types as shown in Table 15 for some of the building types:
Table 15: Overpressure vulnerabilities in various building types [7, 8] Overpressure Fatality Probabilities Building Type Beast1 Beast2
Beast3
Beast5 Beast7 Beast10
Beast11
Beast12
CIA3
Description of Building Type
30 - 70
70 - 110
110 - 150
150 - 300
300 - 500
> 500
0.0001
0.01
0.065
0.279
0.488
0.488
0.0001
0.01
0.017
0.221
0.668
0.668
0.0001
0.02
0.282
0.282
0.788
0.788
0.00005
0.02
0.02
0.083
0.988
0.988
0.0001
0.0001
0.017
0.171
0.488
0.488
0.02
0.838
0.838
0.838
0.838
0.838
0.0001
0.025
0.322
0.322
0.988
0.988
0.00005
0.00005
0.02
0.322
0.988
0.988
0.010
0.036
0.081
0.267
0.575
0.740
mbar Steel framed structure with metal panels for roof and wall cladding Steel framed structure with metal wall panels and a reinforced concrete roof Steel framed structure with unreinforced masonry (CMU or brick) infill walls (non-load bearing) and a reinforced concrete or metal roof. Steel framed building with reinforced concrete walls panels and a reinforced concrete roof deck Pre-engineered metal structure Unreinforced masonry building with load bearing walls and a reinforced concrete roof. Reinforced concrete frame structure with unreinforced masonry infill walls and a reinforced concrete roof. Reinforced concrete frame structure with reinforced masonry infill walls and a reinforced concrete roof Typical domestic building, 2 storey brick walls timber floor
Whereas 30 mbar represents a threshold for fatalities, overpressures exceeding 500 mbar tend to lead to 50 % and more fatalities in most building types. Table 15 may be used to select the appropriate reinforcement method for a building to reduce the fatality rate and thus achieve risk mitigation where required. Figure 21 and Figure 22 show the various frequency contours for the different overpressure values. Frequency values are shown for 50 and 70 mbar. Overpressure curves above 70 mbar have not been found.
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10-4 /yr
Figure 21: Frequency contours for 50 mbar
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10-4 /yr
Figure 22: Frequency contours for 70 mbar
These results can be used to specify the Design Accidental Load (DAL) (refer to the Linde Document &AA-S-SD-1002) in conjunction with the following content of Table 16.
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Table 16: Building and Plant Effects at Specified Consequence Levels Consequence Flash Fire
Consequence Level Lower flammable limit
Vapour cloud explosion and subsequent overpressure
500 mbar
300mbar
150 mbar
110mbar
70 mbar
Fireball
30 mbar Within fireball 2 1.333
1000(kW/m ) Pool Fire/Jet Fire
20kW/m
2
12kW/m2
s
Effects on Building/Plant Ignition of easily ignitable materials which are exposed, e.g. flammable vapour vents, etc., plastics, fabrics etc. Secondary fires are possible but unlikely. Process vessels and pipe work likely to be damaged. Unstrengthened buildings likely to be demolished. Threshold of significant damage to process vessels and pipe work. Unstrengthened buildings likely to be significantly damaged/partly demolished. Plant damage is insignificant except for inherently weak structures e.g., empty atmospheric storage tanks. Structural damage to domestic type buildings could be anticipated. Superficial damage would be expected with failure of unsupported walls and all windows broken. Onset of plant damage for inherently weak structures. Virtually all windows broken. Superficial damage to buildings. Plant damage unlikely and only slight superficial damage to buildings of brick construction. Most windows broken and the glass is likely to cause injury to some people within the buildings. Glass broken, but no fatalities anticipated. Building is likely to be ignited. People in the open air would be killed. The threshold of fatality for people exposed. People inside buildings will not be fatally injured. Carbonaceous material will not ignite spontaneously but could be ignited with a pilot flame. Pain experienced on unprotected skin within 2s. People outdoors will be unlikely to be able to reach a place of safety No significant damage to buildings of conventional constructions. People should be able to safely remain in a building subject to this level of thermal radiation. Pain experienced on unprotected skin within a few seconds, but workers with protective overalls and able to move in any direction will have a good chance of reaching a place of safety.
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7.0
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Sensitivity Evaluation
In order to evaluate the effectiveness of further risk reduction measures the following sensitivity calculations have been carried out. Table 17: Sensitivity Cases Case No. 1
Pit on the jetty, LNG Storage Tank and the Pentane Tank
Assumption Sheet No. HC-6
2
Rock Wall around the LNG Storage Tank
RA-6
3
Splitting of cooling up medium tanks into smaller sections in order to reduce inventory
7.1
Sensitivity 1: Pit on the jetty, LNG Storage Tank and the Pentane Tank
Sensitivity
In this sensitivity calculation a bound around the “LNG Ship Loading Jetty”, the “LNG Storage Tank” and the “Pentane Storage Tank” is modelled. The design dimensions of pit are implemented as a bound around leaking equipment and shown in the table below: Bound LNG Ship Loading Jetty LNG Storage Pentane Storage Tank 7.1.1
Height [m] 0.25 1.8 0.9
Area [m2] 104 10.2 23.6
Discussion
This assumption affects the Pool Fire risk. This risk mitigation measure reduces the pool spreading and thus the heat radiation. Pit on the Jetty Early Pool Fire without a bound
Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Sensitivity Evaluation
Early Pool Fire with a bound
Pit around the LNG Storage Tank Early Pool Fire without a bund
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Quantitative Risk Analysis, Lyse LNG Base Load Plant, Train 1 Sensitivity Evaluation
Early Pool Fire with a bund
Pit around the Pentane Storage Tank Early Pool Fire without a bund
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Early Pool Fire with a bund
7.1.2
Comparison with Criteria
As shown ich chapter 7.1.1 the flame heat radiation impact is significantly reduced by a bound. As the contribution of pool fire from Jetty, LNG Storage- and Pentane Tank is small, this positive effect of the bounds is only marginally reflected by the calculated ISR (Individual Specific Risk). However, in order to reduce the risk to ALARP, it is decided to design the plant with a pit for the “LNG Ship Loading Jetty”, the “LNG Storage Tank” and the “Pentane Storage Tank”. This is considered in the risk results presented in Chapter 6.0. 7.2
Sensitivity 2: Rock Wall towards the public area on the peninsula
In this sensitivity calculation all fire vulnerabilities for the peninsula people have been reduced for 80% due to expected radiation effect zone from fires. 80 % of release sources are at lower than the rock wall. 7.2.1
Discussion
The heat radiation in case of fire at the LNG Tank will be reduced towards the public area on the peninsula, thus reduced the risk.
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7.2.2
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Comparison with Criteria
Table 18: ISR for people on the Peninsula
Criteria 1X10-7/year 100 mm) Releases from pipelines, flanges, pumps etc. are modelled as liquid, gas, or two-phase releases. Where an inventory comprises significant liquid and gas sections, e.g. in a vessel, then both are modelled. The representative release height for all cases is taken 1 m; except for the LNG Tank, where 30 m are applied, since the leak sources (flanges) by the LNG Tank are expected on the tank top. Release rates are assumed to be constant throughout the release duration time and calculated with isolation (ESD System), and with blowdown (see Assumption Sheet RA-4). According to EN 1473, the isolated sections shall be depressurised to 50 % of design pressure in 15 minutes or to 7 barg in 30 minutes. Based on this, the calculated time to detect and initiate is 600 s. An average blowdown time of 900 s is used in the calculation. Release rates of gas systems with small gas volume are limited by flow controlled gas supply. Liquid release rates are limited by pump rates. However, the times to detect will vary, depending on leak size, release rate, location of release, etc. In practice, some releases may be isolated much quicker, but it is assumed that this represents a “realistic worst case” value. Implication of assumption: Releases of hydrocarbons affect the fire and explosion risk. Reference: Prepared by: Internal Verification:
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Stavanger LNG Base Load Plant
Date: 2008.07.313
Assumption No.: Subject Area: Topic:
Revision: 1
HC-3
Hazard Identification/Consequence Analysis Hydrocarbon Releases
Assumption/Rule Set Outdoor Releases of hydrocarbons (gas/liquid or two phases) are considered from the counting equipment (see Assumption Sheet FA-1). Hole sizes are defined in Assumption Sheet HC-2. Release duration time is based on the fire and gas detection and ESD&Blowdown System (see Assumption Sheets RA-3 and RA-4). Hydrocarbon leaks in buildings, which contain Hydrocarbons, are defined as explosion group zone 1 and are assumed to have a minor contribution to risk compared to outdoor releases due to forced ventilation. Hydrocarbon entering in a building is prevented by adequate gas detection and closing the air-intake. Therefore Hydrocarbon leaks in buildings are not analysed, but are discussed qualitatively (see Appendix B: Hazard Identification). Implication of assumption: Outdoor hydrocarbon releases affect the fire and explosion risk. The buildings are specified with explosion group zone 1. Gas entering in a building is prevented by adequate gas detection and closing the air-intake. Therefore the risk of internal explosion is not considered. Reference: Prepared by: Internal Verification:
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Stavanger LNG Base Load Plant
Date: 2008.05.26
Assumption No.: Subject Area: Topic:
Revision: 0
HC-4
Hazard Identification/Consequence Analysis Gas Dispersion
Assumption/Rule Set The gas dispersion is calculated by the UDM model implemented in the PHAST / PHAST RISK software. This model considers only free field dispersion, so that any local air stream effects at equipment/ buildings are not included in the dispersion calculation. Dispersion generally is modelled as horizontal releases. A representative gas cloud size to 50% of lower flammable limit (LFL fraction) has been used to determine the magnitude / extent of flash fires / explosions. Implication of assumption: Gas dispersion affects the consequence calculations associated with the fire and explosion risk. Reference: Prepared by: Internal Verification:
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Stavanger LNG Base Load Plant
Date: 2008.05.26
Assumption No.: Subject Area: Topic:
Revision: 0
HC-5
Hazard Identification/Consequence Analysis Gas Fire Modelling
Assumption/Rule Set Gas fires resulting from ignited hydrocarbon releases are modelled as jet fire, flash fire and fire ball for each release scenario. For unimpinged gas releases the jet fire is calculated using the Shell model. The original Shell model uses the Chamberlain correlation for calculation of the flame length as function of the release rate, which was developed for near-vertical vapour-phase releases. This correlation was modified by Cook et al. to describe the shape of jets that contain liquid. Therefore the option DNV Recommended has been used, that means the PHAST / PHAST RISK program will use the correlation that is most appropriate for the release-conditions. For impinged releases the fireball diameter is calculated from the release rate using the correlation given in Dutch Yellow book. For delayed ignition the flash fire limit is the distance to ½ LFL. Implication of assumption: This assumption affects the fire risk. See also the assumption sheet RA-6. Reference: Methods for the calculation of physical effects (Yellow Book), CPR14E Sign: CAN Date: 2008.05.26 Prepared by: Sign: Date: 2008.05.26 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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Date:
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Stavanger LNG Base Load Plant
Date: 2008.07.31
Assumption No.: Subject Area: Topic:
Revision: 1
HC-6
Hazard Identification/Consequence Analysis Liquid Fire Modelling
Assumption/Rule Set Fires resulting from ignited liquid releases are modelled as a pool or a jet fire. Pool fire dimensions are modelled using the spill rate to compute pool development with allowance for burning (if ignited) or boil off. The maximum pool sizes are defined either by hitting a dike wall or by reaching a minimum thickness. The minimum thickness depends on surface and is set by the PHAST / PHAST RISK program to 5 mm for a concrete surface. For pool fires the effects are calculated for an early and late ignition. The late pool fire is assumed to occur when the pool reaches its maximum radius. For early pool fires pool size evolution is based on ignition occurring at 10 sec. Jet flame lengths and radiation effects distances are calculated as per gas fires (refer to HC5). The bund around the pentane tank is implemented in the calculation. The effect of an LNG pit at the storage tank and at the jetty is implemented in the LNG PLANT QRA calculations as a bund around the tank (Inventory Loop 3B) and around the jetty (Inventory Loop 5C), since the PHAST RISK program can not directly simulate such a pit. The bunds limit the pool spreading. Implication of assumption: This assumption affects the fire risk. The LNG pool fires around storage tank and around the jetty loading are limited by a pit in each case (modelled as bund). This reduces the pool spreading and thus the heat radiation. Reference: Prepared by: Internal Verification:
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HC-7
Hazard Identification/Consequence Analysis Vapour Cloud Explosion Modelling
Assumption/Rule Set The TNT model is used to calculate vapour cloud explosion effects. The explosion efficiency is set to 10 %. For gases lighter than air an air burst is assumed. For gases heavier than air a ground burst is taken into account. Then the PHAST / PHAST RISK program multiplies the explosion efficiency by factor two, to account for the effects of reflection on the overpressure. The flammable mass is calculated as mass between LFL and UFL. The explosion location criterion is the cloud front (1/2 LFL fraction). Vapour cloud explosion effects are calculated if the minimum explosion energy of 5 x 10^6 kJ (DNV default value) is exceeded. Implication of assumption: This assumption affects the explosion risk. Reference: Prepared by: Internal Verification:
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HC-8
Hazard Identification/Consequence Analysis Non-Process
Assumption/Rule Set Non-process events include: loss of utilities (failure leads to fail safe conditons), utilities releases, non-hydrocarbon fires (e.g. transformer fire in electrical/instrument room). They are not included in the LNG PLANT QRA due to their low frequency and low consequence and active and passive fire protection , but discussed qualitatively (see Appendix B: Hazard Identification). Implication of assumption: This assumption has none impact on fire and explosion risk in the LNG PLANT QRA. Reference: Prepared by: Internal Verification:
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HC-9
Hazard Identification/Consequence Analysis Loading Frequency
Assumption/Rule Set Loading operations are assumed to be 1 cargo ship loading every 5th day (filling time 6h) and truck loading 10 times in a day (filling time 1.2 h). Implication of assumption: This assumption reduces the release and ignition probabilities. Reference: Prepared by: Internal Verification:
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HC-10
Hazard Identification/Consequence Analysis Ship Transport Accidents
Assumption/Rule Set Types of accidents are not a part of LNG PLANT QRA. A ship collision risk assessment is recommended (important risk). As it has an impact on third party population risk. A ship collision with jetty could be significant with respect to 1st risk. Implication of assumption: This assumption could have impact on fire and explosion risk in the LNG Plant. Collision incidents per port visit - while mooted at jetties, berths etc or within locks, enclosed harbours etc. is 3.7 X 10-5 [LMIS database]. Therefore, such accidents can be neglected. Reference: Lyod’s Maritime Information Services (LMIS). Sign: CAN Date: 2008.07.31 Prepared by: Sign: Date: 2008.07.31 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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HC-11
Hazard Identification/Consequence Analysis Occupational Risk
Assumption/Rule Set The occupational accidents have been not included in the acceptance criterion, and are therefore not considered in the LNG Plant QRA. Implication of assumption: This assumption has none impact on harm/death risk in the LNG Plant QRA. Reference: OGP, Safety Performance Indicators – 2006 data, Report no. 391, June 2007 Section 2.2 & 4.1 Sign: CAN Date: 2008.05.26 Prepared by: Sign: Date: 2008.05.26 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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FA-1 Frequency Analysis Inventory Count
Assumption/Rule Set For each inventory the leak frequencies are estimated using a full parts count of the equipment shown on the P&ID. Typically this includes: • Flanges (not to consider in welded pipelines) • Valves • Small bore fittings • Pipelines • Pressure vessels • Heat exchangers • Pumps • Compressors • Atmospheric Tanks Equipment counts assumptions are detailed below: • Drums and other vessels that are primarily gas (e.g. cycle compressor interstage drum) or liquid (e.g. cold MRC separator) are conservatively treated as 100% gas or liquid, respectively • Relief valves to flare and blow down valves are counted as normal valves and assumed to be closed in normal operation. Therefore downstream equipment are not considered • Flanges and small bore fittings in pipelines are not counted since the failure of flanges is included in the failure frequency of the pipeline [Purple Book] • For jetty, a double flange per valve connections and associated flanges are counted • Flanges and small bore fittings at vessels and at the LNG Tank are not counted since their failure frequencies are included in the failure frequency of the vessels and tanks [Purple Book] Further details are given in Appendix C: Equipment Count. Implication of assumption: The amount of inventories as leakage sources affects the release frequency. Reference: Guidelines Risk calculations (Purple Book) BEVI Module C, Version 3.0 Date 1 January 2008: Modelling specific BEVI categories. BEVI is the abbreviation of the decree implementing the SEVESO directive. Sign: CAN Date: 2008.06.02 Prepared by: Sign: Date: 2008.06.02 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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FA-2 Frequencies Analysis Frequency Database
Assumption/Rule Set As Linde AG has not received a database from the Client, the leak sizes and- frequencies, are calculated with DNV Software Leak 3.2. The generic failure data used as the basis of the frequency analysis is the UK HSE Offshore Hydrocarbon Release Statistic 1992-2006, or HCRD [Ref. A]. This is a DNV recommended database for Hydrocarbon releases. To reflect the LNG plant, which is considered a clean service and an onshore facility, leak frequencies for pipelines, vessels and the LNG Storage Tank are applied as given in the Purple Book [Ref. B]. Accordingly, failures of flanges in pipelines or at vessels are included in the failure frequency of the pipeline or of the vessel (see Assumption Sheet FA-1). Further details are given in Appendix D: Results of Leak 3.2. Calculations. Implication of assumption: Key influence on the risks (i.e. risk is directly proportional to frequency). Reference: A: HSE, 2000. Offshore Hydrocarbon Release Statistics, 1999, Offshore Technology Report OTO 079, HSE Offshore Safety Division (OSD), January 2000. B: Guidelines Risk calculations (Purple Book) BEVI Module C, Version 3.0 Date 1 January 2008: Modelling specific BEVI categories. BEVI is the abbreviation of the decree implementing the SEVESO directive. Sign: CAN Date: 2008.05.26 Prepared by: Sign: Date: 2008.05.26 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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FA-3 Frequencies Analysis Leak Frequency (LNG Storage Tank)
Assumption/Rule Set Acc. to EN 1473 roof collapse/tank collapse is considered negligible for full containment tanks. Therefore, a very large leak (full rupture) associated with the full containment LNG tank is not considered in Inventory Loop 3A “LNG Storage Return Gas” (refer to the Assumption Sheet HC-1). Further details are given in Appendix D: Results of Leak 3.2. Calculations. Implication of assumption: The leak frequency is directly proportional to risk. Reference: Prepared by: Internal Verification:
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RA-1 Risk Assessment Event Tree Probabilities
Assumption/Rule Set The development of a release is largely defined by the stage at which ignition occurs, where the immediate and delayed ignition may give an explosion, or a flash fire, or a fireball. These different developments are represented in a diagram called an “event tree”, and the probabilities for the developments are known as “event tree probabilities” or “event tree parameters”. The sum of the probabilities for Fireball, Flash Fire, Explosion and Pool Fire alone is usually 100%. An example risk model event tree for a continuous release with rainout (with probability of a pool fire) is shown in Figure 23. Figure 23: Example Risk Model Event Tree Structure
1.0
0.6
1.0 0.3* 1.0
0.6 0.4
0.15
* The default probability of immediate ignition (0.3) has not been used to account the effects of fluid properties (e.g. reactivity) and source strength on the ignition probability. If no immediate ignition occurs, the program models the dispersion of the cloud through a succession of time steps until it has diluted below a hazardous concentration. At each time step the program models the effects of delayed ignition of the cloud, calculating the probability of delayed ignition by considering the ignition sources (see the Assumption Sheet RA-2) within the flammable area of the cloud during that time-step.
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Implication of assumption: The event tree is a key aspect of the QRA model and affects of fire and explosion risk depending on the timing and type of ignition. Reference: Prepared by: Internal Verification:
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RA-2 Risk Assessment Ignition Sources – Probabilities
Assumption/Rule Set The ignition sources are defined by ignition probability and time period. The ignition probability is the probability that the ignition source will ignite a flammable cloud if the cloud is exposed to the source for the specified time period, which is assumed 10 s (default value in PHAST RISK). The expected ignition sources and their probabilities are listed in following table: Ignition Source Speed Flare 54-FC-101 Fired Heater for Hot Oil 52-FA-101 H2S Conventer (Incinerator) 20-XT-101 Electrical Substation Traffic (Truck Loading) Maintenance Traffic Parking Area Traffic
Ignition Probability
Traffic Density
Average
[Fraction] 0.5 0.1 0.1 0.1 0.1 0.1 0.1
[day]
[kph]
10 1 20
30 30 20
It is assumed that all electrical equipment will be EX-safe (Explosion Protection). Due to fire and gas detection, the Regenerative Thermal Oxidation (RTO) Incinerator and all the not exsafe units will be isolated by closing the damper at the air inlet. Therefore the ignition probabilities have been reduced to 0.1 expect for the flare. The flare pilots will burn with a pilot flame continuously. Due to the fact that the flare pilots are installed 70 m above ground and the assumption that only 50 % of flammable gas clouds will disperse to this height, the flare ignition probability has been reduced from 1 to 0.5. The reduced ignition fractions may reduce the delayed ignition probabilities on the event trees, which are depends on the ignition fractions (e.g. Assumption Sheet RA-1). The default value assigned within PHAST RISK for the ignition source associated with people corresponds to 1.68 x 10-4 per person per second of cloud exposure. This value has been derived to account for the probability of ignition associated with people in general, and includes an allowance for smoking and general human behaviour associated with residential areas. The ignition probability of personal within the LNG Plant would be zero (except the truck and maintenance traffic), with no smoking. Immediate ignition for material properties of the released material have been taken into account and shown in table below: Class (Material) immediate
source-continuous
Average/high reactivity 100 kg/s Low Reactivity 100 kg/s
source-instantaneous
10,000 kg/s 10,000 kg/s
probability of ignition 0.2 0.5 0.7 0.02 0.04 0.09
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Implication of assumption: This assumption affects of fire and explosion risk depending on the timing and type of ignition. The ignition probabilities due to ex-safe design and fire and gas detection reduce the fire and explosion risk. Reference: Prepared by: Internal Verification:
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RA-3 Risk Assessment Fire and Gas Detection
Assumption/Rule Set The fire and gas detection depends on the location and magnitude of the event, the number, location of detectors and their PFD (probability of failure on demand). However, the basis design of the LNG Plant considers a sufficient fire and gas detection (refer to the Linde Document &AA S-PC-1004 Fire Protection Concept and &AA S-ZA-1003 Fire & Gas Detection Plan). The F&G System is considered in the QRA by prevention / mitigation of Hazards either automatic or manual actions activated upon gas detection: • Automatic shutdown of the following ignition sources (refer to Assumption Sheet RA-2) : o Regenerative Thermal Oxidation (RTO) (Incinerator) 20-XT-101 o fired heater (Hot-oil unit) 50-XT-101 • Manual activation of the Emergency Shutdown, Isolation and Depressuring System via push-buttons by the operator in the CCR. The F&G detection system is the basis of the ESD- and Blowdown duration time (see the Assumption Sheet RA-4). Implication of assumption: This assumption affects the release duration. Reference: Prepared by: Internal Verification:
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RA-4 Risk Assessment ESD/Blowdown System-Duration Time
Assumption/Rule Set The initial release rate [in kg/s] is calculated within the PHAST RISK discharge model and set constant during the representative release duration time. In reality, the internal pressure is reduced and this reduces the release rate. If the initial release rate is very large, the release duration time will be short. Low release rates will compensate with the representative release duration time, which is typically of 1500 s and shown in Figure 2. Figure 24: Refrigerant Depressurizing Calculation pressure
P1
A1
A1 ~ A2
A2
900 s
time Time used in QRA model as max. release duration at constant release rate after initiation of ESD and Blowdown
According to EN 1473, the isolated sections shall be depressurised to 50 % of design pressure in 15 minutes or to 7 barg in 30 minutes. Based on this, the calculated time to detect and initiate is 600 s followed by an average blowdown time of 900 s. Implication of assumption: This assumption affects release the release rates and duration times. Reference:
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RA-5 Risk Assessment Vulnerabilities
Assumption/Rule Set A given accident may lead to fatalities both indoors and outdoors depending on each hazardous effect. The lethality factors are given for individual and socitial risk calculations and shown in Figure 3. Figure 25: Default values based on Purple Book set in General Risk Parameters in PHAST RISK
Some of this default values have been changed based on the mitigation measures by the assumption sheets RA-6 and RA-8. Implication of assumption: The risks are directly influenced by the impact and fatality assumptions, which quantify the severity of the consequences. Reference: Guidelines Risk calculations (Purple Book) BEVI Module C, Version 3.0 Date 1 January 2008: Modelling specific BEVI categories. BEVI is the abbreviation of the decree implementing the SEVESO directive. Sign: CAN Date: 2008.00.02 Prepared by: Sign: Date: 2008.06.02 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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RA-6 Risk Assessment Heat Radiation Mitigation
Assumption/Rule Set The impact of heat radiation from fires to the peninsula depends on the height of the release sources. 80% of all release sources (vessels, pipework and the LNG Storage Tank) are at a lower level than the rock wall. The heat radiation effect zones are simplified shown in figure below. The heat radiation effects are expected at the rock wall top. It is confirmed by the Client that no people will enter the rock wall top, which will be ensured by appropriate measures.
Therefore all fire vulnerabilities for the peninsula people have been reduced in the General Risk Parameters (default vulnerabilities in Assumption Sheet RA-5) for 80% (i.e. outdoor vulnerability factor for fire is reduced from 1 to 0.2).
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For a more detailed evaluation of this effect, CFD calculations would be required. Implication of assumption: This assumption reduces the risk to people on the peninsula. (Refer to the Table 2 “Individual Specific Risk (ISR) for the 3rd party”) Reference: Prepared by: Internal Verification:
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RA-7 Risk Assessment Active and Passive Fire Protection
Assumption/Rule Set Active Fire Protection: All vessels and piping are protected by the water application like monitors, hydrants. Passive Fire Protection: Fireproof insulation for supporting steel structures shall be provided to protect the plant and fire fighting personnel against the effect of support failure in case of fire. Fireproof insulation is needed within fire hazardous areas. For details, refer to the Linde Document &AA S-PC-1004 Fire Protection Concept. To consider the Stavanger LNG Base Load Plant being an onshore plant with clean service etc. the leak frequencies for piping, the LNG storage tank and pressure vessels given in the Dutch Purple Book have been applied. But additive to that no credit for active and passive fire protection can be taken, as leakage failure rates given in the HSE database as well as failure rates given in the purple book consider only initial leakages, but not secondary leakages due to heat ingress caused by fire radiation. Implication of assumption: This assumption prevents the escalation risk. Reference: Guidelines Risk calculations (Purple Book) BEVI Module C, Version 3.0 Date 1 January 2008: Modelling specific BEVI categories. BEVI is the abbreviation of the decree implementing the SEVESO directive. Sign: CAN Date: 2008.07.31 Prepared by: Sign: Date: 2008.07.31 Internal Verification: BAUMGARTNER/RATH Comment from Lyse: Approved by Lyse:
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RA-8 Risk Assessment Escape Ways and Safe Haven
Assumption/Rule Set Escape Ways: Escape ways are considered to be state of the art in hydrocarbon processing plants Therefore no credit is taken to account. Safe Haven: The probability of death within the building will depend on the vulnerabilty of the building in the first instance and given a level of damage how vulnerable the occupants are to the combined hazards. The control room is designed for dynamic resistance pressure of 200 mbar and may verify a overpressure vulnerabilty factor of 0.322. Therefore, the Heavy Explosion Damage value in the General Risk Parameters (default vulnerabilities) has been changed from 1 to 0.322 for the administrative personal (refer to the Assumption Sheet RA-5 and the table in the QRA Issue 02). Implication of assumption: This assumption affects the fire and explosion risk. Reference: Prepared by: Internal Verification:
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Revision: 0
MI-1 Miscellaneous Acceptance Criteria
Assumption/Rule Set The below tables and figures summarize the Acceptance Risk Criteria for Stavanger LNG Base Load Plant given by the Client.
Acceptance Risk Criterion for Stavanger LNG Base Load Plant Individual Risk (Pr År) 1st and 2nd party risk 3rd party risk Individual specific risk (ISR) for most exposed person Avarage individual risk (AVR)
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