Part 2.5 Dispersion Modeling Using ALOHA

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1 Part 2.5 Dispersion Modeling Using ALOHA Dr. Arshad Ahmad 1

2 Software Commonly used for Risk Analysis Software SAFETI SFU CAFTAN ETRA HAZSEC. HAZTRAC. PHAST. WHAZAN EFFECTS. DAMAGE PC-FACTS. ASAP FMECA ANEX Application Onshore Risk Analysis. Offshore Risk Analysis. Fault Tree Analysis. Event Tree Analysis. HAZOP Study. HAZOP Recommendation Tracking. Consequence Analysis. Consequence Analysis. Consequence (Effects) Modeling. Consequence (Damage) Modeling. Failure & Accident Databank. Event Tree Analysis. Failure Mode Effects & Criticality Analysis. Life Time Analysis & Failure Estimation.

3 Software Commonly used for Risk Analysis Software ALOHA CLASS RISK CURVES RISKA T E&P FORUM FACTS OREDA FRED EAHAP Application Consequence Analysis Hazardous Area Risk & Classifications TNO Individual & Group Risk computations Risk Analysis model of Health & Safety Executives, UK Hydrocarbon Leak & Ignition Database. TNO Frequency Estimation Database DNV Frequency Estimation Database Consequence Analysis software of Shell, UK Consequence modeling software of Energy Analysts Inc. US)

4 What is CAMEO? CAMEO is computer software primarily used: For chemical emergency planning For chemical response; and For regulatory compliance The overall CAMEO system is a suite of three separate, integrated software applications: CAMEO (Computer aided management of emergency operation) MARPLOT (Mapping application for response and planning of local operational task) ALOHA (Areal locations of hazardous atmosphere) Developed by: EPA s Chemical Emergency Preparedness and Prevention Office NOAA s Hazardous Materials Response and Assessment Division

5 CAMEO Answers Questions What hazards are at this site? Where is the hazard located? What is the chemical? What specific hazard(s) does it present? How can the hazard be mitigated?

6 Toxic Release Inventory Cameo Module Relationships Chemicals in Inventory/ Transit Storage Locations Chemical Information Facilities Screening & Scenarios Incidents Routes Special Locations Contacts Census Data Resources

7 ALOHA

8 What is ALOHA Air hazard modeling program Predicts how quickly chemical will escape from a tank, puddle, gas pipeline etc Model how gas travel downwind (include neutrally buoyant and heavy gas dispersion) Model fire and explosion (pool, jet, flash, BLEVE, VCE) Produces threat zone estimate, showing area of hazards (toxicity, thermal radiation) Threat zones can me mapped into MARPLOT, Google maps, Google earth 8

9 Example of ALOHA s Output Threat Zones Concentration at a point 9

10 GIS Compatible Output 10

11 Fire and Explosion

12 Pool Fire 12

13 Pool Fire 13

14 Jet Fire 14

15 Jet Fire 15

16 BLEVE Fireball Model 16

17 BLEVE Fireball Model 17

18 Flash Fire & Vapor Cloud Explosion Model 18

19 Flash Fire & Vapor Cloud Explosion Model Vapor cloud explosion major assumptions: Uses Baker-Strehlow-Tang methodology Flammable mass (0.9LEL - UEL) Explosion efficiency Detonation 100% Deflagration 20% Ignition options Hard ~10 6 Joules Soft ~1 Joule 19

20 Flash Fire & Vapor Cloud Explosion Model Vapor cloud explosion major assumptions: (cont.) Congestion options High area blockage ratio > 40% Low area blockage ratio < 10% 20

21 Flash Fire & Vapor Cloud Explosion Model 21

22 Example: Facility Siting Case Study 22

23 Example: Facility Siting Case Study Release through 3-inch relief valve leading to: Jet fire Flash fire Vapor cloud explosion Failure of storage vessel engulfed in flames leading to: BLEVE fireball 23

24 Facility Siting Case Study Jet Fire Results 24

25 Facility Siting Case Study Jet Fire Results 25

26 Facility Siting Case Study Jet Fire Results 26

27 Facility Siting Case Study Jet Fire Results 27

28 Facility Siting Case Study Jet Fire Results 28

29 ALOHA Scenario In a transportation accident at km 182 of Southbound North-South Expressway in Nilai, a 9000 Gallon tank truck carrying ammonia overturns and shears off a flange whose diameter is 4 inches. The size of the tank is 24 feet long and 8 feet in diameter. The tank contains liquid, which is stored at ambient temperature. The fill density of the tank is 75% by volume. The sheared-off flange creates a circular opening of about 3 inches in diameter, and it is located at 30% of the way to the top of the tank. At the time of the accident, the wind direction is NE (i.e. blowing from NE), the wind speed is 3 m/s, measured at 10 m height. The accident occurred on a highway near a small village. The weather is partly cloudy, 80% relative humidity, and the temperature is 32 degrees Celsius. 29

30 Dispersion Modeling 30

31 Meteorology and Boundary Layer Wind factors Vertical temperature structure & stability Surface roughness Meteorological instrumentation 31

32 Source Term, Dilution & Plume Rise Release parameters from source Release parameters of the chemical Plume rise Release height for buoyant sources Volume & area point sources Building effects 32

33 Dispersion of Neutrally Buoyant Gases The plume is not rising nor sinking Equal probability of spreading in different directions Neutrally buoyant gases are described using Gaussian statistics or normal distributions 33

34 Dispersion of Heavy Gases Types of heavy gases Gravitational spreading Phases of heavy gas dispersion Release Transition Dispersion 34

35 End of Lecture 35

ALOHA. Example Scenarios. September 2016

ALOHA. Example Scenarios. September 2016 The CAMEO Software Suite ALOHA Example Scenarios September 2016 National Oceanic and Atmospheric Administration Office of Response and Restoration Emergency Response Division Seattle, Washington E N V