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RISK-BASED DESIGN TOOLS FOR
PROCESS FACILITIES
Peiwei Xin
M.Eng, Oil and Gas Engineering
Memorial University of Newfoundland
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Content
Risk-Based Design
Risk-Based Design Tools
• Hazard Identification Tool
• Layout Optimization Technique
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Risk-Based Design
What is risk-based design?
• Incorporate risk-analysis
• Complementary approach to traditional design
• Cost-effective
• The ultimate goal is to make the total risk meet the
following criterion:
Rdesign ≤ Racceptable
• Design for safety
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Risk-Based Design
What does a risk-based design process include?
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Risk-Based Design
Research Objective
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Risk-Based Design
Research Objective
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Dynamic Hazard Identification and Scenario
Mapping Using Bayesian Network
Part I
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Dynamic Hazard Identification
Hazard identification
• Hazard identification and risk assessment
• Answers what can go wrong
• Methods of hazard identification
• Dynamic hazard identification
Hazard and hazard scenarios
• Hazard scenario can be a single event or combination of
events
• Hazard scenario depicts the evolution of hazards
• Hazard evolution is linear progression
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Dynamic Hazard Identification
Bayesian Network (BN)
• Graphic modeling tool
• Consisted of a qualitative part and a quantitative part
• Mapping interdependence among random variables
Why Bayesian?
• Types of hazards and their causes can be represented by propositional
variables with multiple states in a BN;
• Directed edges help to encode causal relations in the evolution of
hazards
• Deterministic and probabilistic evidence represent situations in real
practice and effectively solve problems brought by uncertainties
• Assign the most credible hazards a probability ranking
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Methodology of Constructing
Dynamic HAZID Model
• Step 1: Create hazard scenarios
• Step 2: Identifying nodes
• Step 3: Classifying nodes
• Step 4: Mapping causal relations among nodes
• Step 5: Assigning conditional probability tables (CPTs)
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Create hazard scenarios
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Generic Dynamic HAZID Model
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Model Validation
Study 1: Chevron Richmond Vapour Fire
Source:http://www.csb.gov/chevron-refinery-fire/
Study 2: Vapour cloud explosion Source:http://www.csb.gov/cai-/-arnel-chemical-plant-explosion/
Study 3: Ammonia toxic release Source:http://www.csb.gov/millard-refrigerated-services-ammonia-release/
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Model Validation – Study 1
Simulation Results (Vapor Fire, California, 2012)
Carbon Steel Pipe
(Light Gas Oil)
Sulfidation
Corrosion Pipe Rupture
Vapour
Release
Vapour Cloud
Formation Vapor Fire
Ignited
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Model Validation – Study 1 Simulation Results (Vapor Fire, California, 2012)
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Model Validation – Study 2
Simulation Results (VCE, Danvers, 2006)
Human Error Steam Valve
Open
Flammable Liquid
Overheating
Vapour
Release
Vapour Cloud
Formation VCE
Ignited
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Model Validation – Study 2 Simulation Results (VCE, Danvers, 2006)
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Model Validation – Study 3
Simulation Results (Toxic Release, Alabama,2010)
Refrigeration Coil Hydraulic
Shock Rupture
Toxic Ammonia
Release Toxicity
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Model Validation – Study 3 Simulation Results (Toxic Release, Alabama,2010)
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Sensitivity Analysis
Simulation Results
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Sensitivity Analysis – Fire & Explosion
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Sensitivity Analysis – Pressure
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Sensitivity Analysis – Pressure
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Sensitivity Analysis – Material
Strength and Overflow
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Sensitivity Analysis – Material
Strength and Overflow
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Sensitivity Analysis -Conclusion
• Confinement has the largest influence on the occurrence
of a fire or explosion, and a high confinement condition
more likely results in an explosion scenario.
• Pressure influences the type of fire to a great extent.
• Material strength and an overflow of equipment influence
the probability of explosion significantly, with the material
strength having larger influence.
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Layout Optimization of A Floating Liquefied
Natural Gas Facility Using Inherent Safety
Principles
Part II
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Content
Introduction of Floating LNG facility
Floating LNG topside deck design
Inherent safety method
Layout Optimization
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Floating LNG Facility
What are Floating LNG facilities ?
• Floating, production, storage, offloading (FPSO)
What are the advantages?
• Long distance transportation & multi-location
• Inaccessible area Accessible
• Solution to marginal areas
• Environmental advantages
Source: http://theenergycollective.com/celinerottier/189491/will-
floating-lng-revolutionise-natural-gas-industry
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FLNG Topside Deck Design
Importance of Layout
• Decide arrangement of Area and Equipment
• Affect complexity of Piping System
• Access of Plant & Emergency Response Plan
• Routes of Hazard Propagation
Topside Deck Design
• LNG Process Selection
• Process Area Design
• FLNG Topside Deck Design
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Liquefaction Process
Dual Mixed Refrigerant Liquefaction Process
• Adopted by Shell and Sakahalin Projects
• Dual Mixed Refrigerant Cycles
• Pre-mixed refri-cycle (PMR) cools natural gas to -30˚
• Mixed refri-cycle (MR) cools natural gas to -160˚
• High Efficiency &Large Capacity
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Liquefaction Process Dual Mixed Refrigerant Cycle:
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Liquefaction Process Dual Mixed Refrigerant Cycle:
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FLNG Topside Deck Design Process Area Design:
• What if add storage area, living quarter, water treatment, and
control room?
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FLNG Topside Deck Design Topside Layout:
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Layout Evaluation Method
Inherent Safety Method
• Inherently eliminate and mitigate hazards
• Inherent guidewords of layout assessment
• Attenuation
• Simplification
• Limitation
• Index-based approach (Tugnoli, Khan, &Amyotte, 2008; Khan & Amyotte, 2004& 2005)
• Domino Hazard Index
• Integrated Inherent Safety Index (I2SI)
• Cost index
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Layout Evaluation Method
Layout Evaluation Calculation Method:
References: Tugnoli, A., Khan, F., Amyotte, P., & Cozzani, V., 2008, “Safety Assessment in Plant Layout Design Using Indexing Approach: Implementing Inherent
Safety Perspective: Part 1–Guideword Applicability and Method Description,” Journal of hazardous materials, 160(1), pp. 100-109.
Tugnoli, A., Khan, F., Amyotte, P., & Cozzani, V., 2008, “Safety Assessment in Plant Layout Design Using Indexing Approach: Implementing Inherent Safety
Perspective: Part 2–Domino Hazard Index and Case Study,” 160(1), pp. 110-121.
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Layout Optimization
Comparison of Domino Hazard Index (DHI):
Comparison Results
• Safety measures can effectively prevent or mitigate hazard escalation.
• Less likely for separate modules to suffer hazard escalation (Domino
hazard).
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Layout Optimization
Comparison of Integrated Inherent Safety Index (I2SI):
No. Unit DI PHCI HCI ISI I2SI Base Option ISI I2SI Option 2 ISI I2SI Option 3
1 Absorber 35.7 56 22 5.00 0.36 12.25 0.87 12.24 0.87
2 Distiller 35.7 56 22 5.00 0.36 12.25 0.87 12.24 0.87
3 Cooler 26.5 46 22 5.00 0.39 23.43 1.85 23.43 1.85
4 Common Header 26.5 30 22 5.00 0.26 12.25 0.63 12.24 0.63
5 PMR Suction Drum1 26.5 40 22 5.00 0.34 1.89 0.13 1.73 0.12
6 PMR Suction Drum2 26.5 50 22 5.00 0.43 1.89 0.16 1.73 0.15
7 PMR Compressor1 34.7 56 26 5.00 0.31 7.15 0.44 21.21 1.32
8 PMR Compressor2 34.7 56 26 5.00 0.31 7.15 0.44 21.21 1.32
9 Cooler for Comp.1 26.5 46 22 5.00 0.39 21.21 1.67 21.21 1.67
10 Cooler for Comp.2 26.5 46 22 5.00 0.39 5.76 0.45 31.11 2.46
11 Cooler1 26.5 46 22 5.00 0.39 21.21 1.67 21.21 1.67
12 PMR Receiver 26.5 44 22 5.00 0.38 5.76 0.43 32.66 2.47
13 Heat Exchanger1 26.5 52 22 5.00 0.45 1.89 0.17 11.49 1.03
14 Heat Exchanger2 26.5 52 22 5.00 0.45 1.89 0.17 10.10 0.90
15 Expansion Valve1 26.5 46 16 5.00 0.54 1.89 0.21 12.24 1.33
16 Expansion Valve2 26.5 54 24 5.00 0.42 1.89 0.16 12.24 1.04
17 MR Phase Seperator 20.2 44 16 5.00 0.68 23.43 3.19 142.86 19.43
18 Heat Exchanger3 20.2 52 22 5.00 0.58 10.13 1.18 10.10 1.18
19 Heat Exchanger4 20.2 52 22 5.00 0.58 10.13 1.18 10.10 1.18
20 Expansion Valve3 20.2 54 24 5.00 0.56 23.43 2.61 23.43 2.61
21 Expansion Valve4 20.2 54 24 5.00 0.56 10.13 1.13 10.10 1.12
22MR Compressor Suction
Drum20.2 54 22 5.00 0.61 10.13 1.23 10.10 1.23
23 MR Compressor 30.6 58 28 5.00 0.34 10.13 0.69 10.10 0.68
24Cooler for
MRCompressor 20.2 38 14 5.00 0.67 10.13 1.36 10.10 1.36
25 Cooler2 30.6 48 24 5.00 0.33 10.13 0.66 10.10 0.66
Option 2 Option 3Base Option
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Layout Optimization
Comparison of Integrated Inherent Safety Index (I2SI):
Comparison Results
• I2SI values are generally higher for the equipment in Option 3
compared to the other two.
• Option 3 has the largest extent applicability of inherent safety.
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Layout Optimization
Comparison of Cost Index:
Cost of Loss
No. Module Base Option($) Option 2($) Option 3($)
01 GT Module 5.09E+10 4.60E+10 4.60E+10
02 PMR Module 1 9.80E+10 9.22E+10 8.96E+10
03 PMR Module 2 7.60E+10 7.31E+10 6.79E+10
04 MR Module 1.24E+11 1.21E+11 1.13E+11
Total saving 1.65E+10 1.62E+10
Comparison Results
• Option 3 has best cost-effective performance compared to the others.
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Layout Optimization
Comparison of Cost Index:
Base Option Option 2 Option 3
No. Module Cost of
Conventional
Safety (1000$)
Cost of Inhernt
Safety (1000$)
Cost Saving
(1000$)
Cost of Inhernet
Safety (1000$)
Cost Saving
(1000$)
01 GT Module 872 428 444 428 444
02 PMR Module 1 1250 960 290 762 488
03 PMR Module 2 1120 1780 -660 872 248
04 MR Module 1670 3350 -1680 2250 -580
Total saving -1606 Total Saving 600
Comparison Results
• Option 3 has best cost-effective performance compared to the others.
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Conclusion
Risk-based Tool Part I:
• Dynamic hazard identification methodology is presented
• Generic model is developed
• Accommodate information update and realize real-time hazard
identification
Risk –based Tool Part II:
• Perform layout optimization using inherent safety method
• Safety measures and modules segregation can effectively prevent
hazard escalation
• Inherent safer design makes plant inherently safer and have better
cost-performance
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Future Work
• Integrate updating mechanisms into a Bayesian network
• Adopt more previous accident cases to extract historical data for
updating conditional probability tables.
• Conduct probability analysis and consequence
• Account for the impact of environmental forces on FLNG layouts.
• Further study the feasibility of the proposed FLNG topside layout
• compared to other existing naval architectures.
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Contributions
• Xin, P., Khan, F., & Ahmed, S. (2016). Dynamic Hazard Identification and
Scenario Mapping Using Bayesian Network. Paper under review of Process
Safety and Environmental Protection.
• Xin, P., Khan, F., & Ahmed, S. (2015). Layout Optimization of a Floating
Liquefied Natural Gas Facility Using Inherent Safety Principles. Paper
accepted at Journal of Offshore Mechanics and Arctic Engineering.
• Xin, P., Ahmed S., Khan, F., (2015). Inherent safety aspects for layout
design of a floating LNG facility. International Conference on Ocean,
Offshore, and Arctic Engineering (OMAE), St John’s, ASME.
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