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C A K E R N G I N E E R I N G A N D I S K O N S U L T A N T S

A Compilation of Current LNG

Technology

John L. Woodward, Ph.D.

Baker Engineering & Risk

Consultants

San Antonio, TX

and

Robin M. Pitblado, Ph.D.

Det Norske Veritas, Houston, TX

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C A K E R N G I N E E R I N G A N D I S K O N S U L T A N T S

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C A K E R N G I N E E R I N G A N D I S K O N S U L T A N T S

LNG Risk-Based Safety: Modeling and

Consequence Analysis; Woodward

and Pitblado, John Wiley & Sons/

AIChE, 2010, 374 pages

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C A K E R N G I N E E R I N G A N D I S K O N S U L T A N T S

Sampling – Two Year Effort

Updated summary of LNG risk analysis

literature, compilation of data.

Important historical developments in LNG

technology.

Compile experimental data on

evaporation, fires, dispersion; models for

each.

Unresolved technical issues: cascading

failures, fire engulfment of carrier,

mechanism of spread on water, pool fire

Motivation

Proportions of membrane carriers

Two Types of Carriers

Moss Sphere Carriers; high centered

Historic Lessons Learned:

eg Sloshing Damage

Learned cargos must be discharged

completely (with minimal heel), limiting

flexibility.

Historically LNG Carriers Have

Survived Grounding

Claims Made by LNG Opponents

LNG Vapor cloud will be 127 miles long from full tank spill on water; Modern models converged on 1.5 miles.

An LNG tanker holds 3,000,000 gal (11,360 m3) Energy equivalent to 5 Hiroshima atom bombs; Burning rates-> 11 to 31 min cf 100 ms nuclear.

Driving Risk Analyses: Hole Size

EU Project HARDER assembled data from 3000

collisions -> 6.6 to 7.4 knots for two LNG carriers

to penetrate. Pitblado et al used ABAQUS FEM code predicted

penetration energy.

Terrorist threats, CFD modeling

FEM Prediction of Bow Intrusion

from Collision with LNG Carrier

Explosive Laden Boat Attack

Threat

Predicted Penetration of Inner Hull

from Explosive Laden Boat Attack

Three Categories of Spills

Spill Under Water Pressures Inner Hull

After initial P equilibrium, equal volume

exchange flow at constant pressure.

Change in Inflow Mechanism for

Breach Below Water Level

Discharge rate drops as pressure builds,

then constant pressure, equal volume

exchange.

Above Water Level-> Jet

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4

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8

10

0 2 4 6 8 10 12 14 16 18 20

Plume Side View (Fraction LFL, LFL, UFL) for Algeria LNGInner Hull 0.10D +11.05m AboveW, BD/D2.5 Cloud 1 ** Maximum Flammable Mass D:\SS3GDEV\Plant\LNGDEMO.SS3

04/22/2009 SS3G V2.03.0027 DLL:18/04/09 05:50 PM

Ve

rtic

al H

eig

ht (

m)

Downwind Distance (m)

Cloud Centerline UFL LFL .5fraction LFL

Inner hull breach above water level could jet past

outer hull and penetrate into water, increasing

potential for RPT.

Possible Technology Transfer to

Predict RPT Energy

Large RPT energy increase at high spill rate

(Coyote).

Hicks-Menzies model explosion efficiency from

water on molten metal.

Alternate LNG Spread Models

Standard: LNG sinks into water by Δ

Supercritical: LNG skitters on film of

vapor

MODEL Max Pool Radius,

mEvap Time, s

Supercritical 1190 65

Standard 350 324

Ratio

SuperC/Std

3.4 0.20

Pool Fire Modeling Issues

Extrapolation to large pool diameters

leads to very high flames, not yet seen in

nature.

0

100

200

300

400

500

600

0 100 200 300 400 500

Pool D, m

Fir

e L

en

gth

, m

Thomas Gb=0.18 Thomas Gb=0.135

Possible Moorhouse Gb=0.18

Cox & Chitty Gb=0.18

Possible Mechanism Change:

Mass Fire

Coherent Fire Longer

Distance to

5 kW/m2

Mass Fire Shorter Distance to 5 kW/m2

Radiant Flux varies with Pool Size

10 m Pool Diameter, 300

gpm Spill Rate

Montoir Test, 35 m Pool

Diameter on Concrete

Structure of Pool Fires

Swirl and Lighthouse Model (Radiating

Bright Spots)

Pool Fire Models Improving

Three-zone model of Raj accounts for

vertical profile in Surface Emissive Power.

Improves distance prediction to 5 kW/m2.

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0.2

0.4

0.6

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1

0 100 200 300 400

E(z), kW/m2

z/L

E(z) Data1 Data2 Data3 Eave

Modeling Effect of Waves &

Carrier Travel- Limits Hazard Out

of Harbors

LNGMAP model by Spaulding et al shows

spill pool moving with tanker path.

Fire Engulfment of Moss Carrier-

SIGGTO-sponsored CFD work

Heat flux needed to buckle weather cover

with size of breach (inverse to duration of

fire). Only holes < 3 m2 can heat cover to

melt pt.

Future LNG Research Needs:

GAO Survey of Experts

Large-scale tests to establish whether

change of mechanism occurs giving

shorter fire plumes with large pool fires

(mass fire).

Is cascading effect of LNG carrier tanks

even possible? (RPT in double hull

space; Ignition in double hull space;

Fire/cryogenic stressing of structural

members).

Which mechanism best describes LNG

spread on water?