Assessment of Hydrocarbon Explosion and Fire Risks. Professor Jeom Paik. The LRET Research Collegium Southampton, 11 July 2 September 2011

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1 Assessment of Hydrocarbon Explosion and Fire Risks by Professor Jeom Paik The LRET Research Collegium Southampton, 11 July 2 September

2 Assessment of Hydrocarbon Explosion and Fire Risks in Offshore Installations: Recent Advances and Future Trends Prof. Jeom Kee Paik, Director The LRET Research Center of Excellence at Pusan National University, Korea

3 New Paradigm for Robust Design of Ships and Offshore Various Ocean Environmental Phenomena Traditional Design Formula Future Engineering Past Experience First Principles Deterministic Probabilistic Allowable Stress Limit States/Risk m Mathematical Algorithm n φαβγ lim x ζ n! εx+ η r! ( n r)! x 2 i= 1 j= 1 Experimental Investigation

4 Trend in Offshore Oil & Gas Production Systems Fixed type in shallow waters Floating type in deep waters Ship-shaped offshore unit, Semi-sub, Spar, TLP Pipeline infrastructure Multiple functions such as production, storage and offloading

5 FPSO for Oil and Gas Production Vessel (hull), topsides (process facility), mooring, risers/flow lines, subsea, and export system

6 Oil/Gas Leak Resulting in Explosion and Fire Source: HSE

7 Pipe Alpha Accident 6 th July 1988, UK 167 people killed Property damage of 1.4billion US$ Risk based engineering became mandatory since the Pipe Alpha accident

8 Deepwater Horizon Accident 20 th April 2010, Gulf of Mexico 11 people killed, 17 people wounded Environmental damage of approx. 30 billion US$ Oil spill

9 Hydrocarbon Explosions and Fires Hydrocarbons can explode through ignition when combined with an oxidiser (usually air). Thus, when the temperature rises to the point at which hydrocarbon molecules react spontaneously to an oxidiser, combustion takes place. This hydrocarbon explosion causes a blast and a rapid increase in overpressure. Fire is a combustible vapour or gas that combines with an oxidiser in a combustion process that is manifested by the evolution of light, heat, and flame. The impact of overpressure from explosions and that of elevated temperature from fire are the primary concern in terms of the actions that result from hazards within the risk assessment and management framework.

10 Mechanism of Gas Explosion Depending on Topology and Geometry Flame front wrinkled, burning surface greater, increased mixing, faster burning Gas burns Gas expands Turbulence Unburnt gas pushed around obstacles BLAST Gas flow increases Volume increases Larger volume pushes unburnt gas ahead CONGESTION? CONFINEMENT?

11 Factors Affecting Explosions and Fires Wind direction Wind speed Leak rate Leak direction Leak duration Leak position (x) Leak position (y) Leak position (z) Type of oil or gas (molecules) Concentration ratio Temperature of oil or gas (LNG Cryogenic -163 degree C)

12 Risk Based Design Process Hazard identification (Step1) Risk assessment (Step2) Decision making recommendations (Step5) Risk control options (Step3) Cost benefit assessment (Step4)

13 What is Risk? How to Manage Risk? = i i R F C Asset risk - Damage to structures and equipment - Duration of production delay (downtime) Environmental risk - Amount of oil that spills out of the offshore installation Personnel risk - Loss of life i

14 Trends in Risk Assessment Qualitative Quantitative, Experiment Past Experience Simulation Deterministic Probabilistic Specific Scenarios All Possible Scenarios

15 API Procedure for Risk-based Design Assessment complete ensure good practice Method 1 Design according to guidances is sufficient if low consequences are expected Yes Does the facility meet screening criteria? No Establish performance criteria Implement measures to reduce fire and blast risk Modify or select new concept or reassess risk Yes Risk matrix Medium or Higher Reconsider or modify concept or reassess risk with more rigorous approach No Implement measures to reduce fire and blast risk Low Are nominal load cases applicable? No Consider fire and blast risk Event-by-Event Risk matrix Low Method 2 Possibility to omit load assessment in certain cases Yes Assess impact on safety critical elements Are performance criteria met? Method 3 Scenario based load and consequence assessment Medium or Higher Assess load and response for the event Are performance criteria met? Yes Assessment complete for the event Yes No Assessment complete for the facility Yes Are further risk reduction options available? No Redesign

16 Simulation-based Procedure for Risk-based Design A Dead and live loads Nominal loads Design guidance System description A: Limit states based design B: Risk based design Definition of scenarios Loads assessment B Performance acceptance criteria Risk acceptance criteria Design load Consequence Risk evaluation Frequency Risk acceptable Risk unacceptable Mitigation Redesign Design complete

17 Joint Industry Projects

18 EFEF JIP - 27th JIP in the World Explosion and Fire Engineering of FPSOs Coordinators: - Pusan National University, Korea - Nowatec AS, Norway Partners: - DSME, SHI, HHI, ABS, KR, LR - Gexcon, CompuIT, USFOS, UK HSE, NTUA

19 Quantitative Gas Explosion Risk Assessment and Management (1/2)

20 EFEF JIP Procedure for Explosion Risk Assessment and Management (2/2) Selection of credible scenarios involving PDF parameters of leak and environment conditions CAD model Latin hypercube sampling technique Selection of credible scenarios involving PDF parameters of gas cloud condition CFD model 0.01 Large cylindrical vessels (Point 171 ) Gas dispersion analysis Explosion frequency of exccedance (per FPSO year) Explosion CFD simulation Overpressure (MPa) Design loads with exceedance curve Nonlinear consequence analysis under explosion

21 EFEF JIP Fire Risk Assessment and Management (1/2)

22 EFEF JIP Procedure for Fire Risk Assessment and Management (2/2) Selection of credible scenarios involving PDF parameters of leak and environment conditions CAD model Latin hypercube sampling technique CFD model 0.1 Nonlinear consequence analysis under fire Exceedance fire frequency(per FPSO year) Mean temperature (Point41 and Point52) Mean temperature (Point20 and Point31) Temperature(K) Design loads with exceedance curve Fire CFD simulation

23 Applied Example: VLCC Class FPSO Topsides

24 Effect of Gas Cloud Volume on Maximum Overpressure Comparison between EFEF JIP and Existing FPSO Practices EFEF JIP FPSO A FPSO B Overpressure (MPa) Equivalent volume (m 3 )

25 Design Explosion Loads with Exceedance Curves 0.01 Process decks Explosion frequency of exceedance (per FPSO year) Above the middle process deck (Point 161) Top process deck (Point 226 & 274) Solid process deck (Point 76 & 124) Overpressure (MPa)

26 Design Explosion Loads Comparison between EFEF JIP and Existing FPSO Practices Risk accepted load FPSO C, D (MPa) EFEF JIP vs. FPSO C EFEF JIP vs. FPSO D Risk accepted load EFEF JIP (MPa)

27 Design Fire Loads with Exceedance Curves Exceedance fire frequency(per FPSO year) Oil inlet (Point 96) Surrounding separation train1 Gas compressor (Point 75) Temperature(K) Separation train 2 (Point 77)

28 Nonlinear Structural Consequence Analysis Escape Route

29 Trends in Risk Assessment Qualitative Quantitative Experiment Past Experience Simulation Deterministic Probabilistic Specific Scenarios All Possible Scenarios

30 CFD Explosion Simulations (barg)

31 Gas Explosion Tests with or without Water Sprays (1/2) - Importance of Risk Management Without water sprays With water sprays Source: The Steel Construction Institute, Fire and Blast Information Group

32 Gas Explosion Tests with or without Water Sprays (2/2) - Importance of Risk Management 2.0 TNO PI-10, Test 10, LDN Nozzles TNO PI-10, Test 11, MV57 Nozzles TNO PI-10, Test 12, No Deluge Source: The Steel Construction Institute, Fire and Blast Information Group Time (ms)

33 Explosion and Fire Test Facilities under Construction in Korea