Risk Management in LNG import terminals andregasification plantsMajor Hazard Accident Risk screening tool for LNGJetties

Presentation Format

• Hazards of LNG

• Accident scenarios associated with LNG Jetties

• Risk Assessment

– Assessing the likelihood of accidental release

– Determining the consequences of LNG releases

• Risk Criteria

• Example application of risk based methodology

• Conclusions

Hazards of LNG

LNG is not Toxic

LNG evaporates rapidly and does not cause Pollution

LNG is not an Explosive material

LNG vapours (methane) are Flammable and releases canresult in;

– Jet fire (ignited pressurised release)

– Pool fire (ignited pool of LNG on land or water)

– Flash fire (ignited cloud of LNG vapours)

– Vapour Cloud Explosion (LNG vapours ignited within confined orcongested areas – unlikely at a jetty).

Flash fire has the potential to affect the greatest distance.

What Do We Mean by Risk ?

Consequence($, Fatalities)

Likelihood(/yr)

RISK($/yr, fatalities/yr)

TolerabilityCriteria

Accident Scenario - Striking

• 3rd party vessels striking canresult in;

– Release from LNG carrier cargotanks if berth is occupied.(Typical cargo tank 9000 Tonnes.)

– Release from jetty pipeworkrecirculation system if berth isnot occupied.

Accident Scenario – Transferrelease

Releases caused by;

• Loading arm failure

• Connection failure

• Ship movement (Ranging).

Quantity releaseddepends on;

• Transfer rate

• Time to isolate

– Detection and isolationsystem

NOTE example is of refrigerated liquefied gas release (not LNG) caused by connection failure.

Consequences of LNG release.

Weather Conditions

Release Scenario Length Downwind (m)

Width Crosswind (m)

Cloud Area (km2)

Transfer Release 1500 kg/sec

560 240 0.1

Instantaneous release from Cargo Tank (9000T) 1680 800 1.3

Transfer Release 1500 kg/sec

950 850 0.8

Instantaneous release from Cargo Tank (9000T)

2430 2400 5.8

Daytime 25 Deg C

5m/sec wind D Stability

Nighttime 0 Deg C

2m/sec wind F Stability

Flammable Cloud Dispersion

If flammable cloud ignites people will be affected. Vulnerabilityassumed to be;

• within cloud, 100% outdoors,10% indoors.• outside cloud or escape before ignition, 0%.

Frequency of releases

• Methodology provides frequencies based on historical datafrom UK ports.

• “Striking” at Jetty - frequency for large releases depends on;

– Number of ships passing the jetty with sufficient energy torupture cargo tanks.

– Vulnerability of the jetty within the Port

– Jetty occupancy

• Transfer release - frequency for large releases depends on;

– Number of cargoes transferred

– Equipment - hoses or hard arms

– Connection type - bolted flange or PERC

– Leak detection and shutdown system - manual or automatic

Risk Criteria Public Domain UK ACDS

Figure 1 FN Criteria Based on ACDS

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1 10 100 1000

Number of Fatalities (N)

Fre

qu

ency

of

Acc

iden

t w

ith

N o

r m

ore

fat

alit

ies

(F)

/yr

Intolerability Limit For Port

Intolerability Limit for Single facility

Intolerability Limit for Jetty.

Containerterminal

500m

2000 Container Ship Movements each way per yr.

Unpopulated Area

Option A

Public Population Density 1400/sq km Day and Night

OnsitePopulation

Density500/sq km Day10/sq km Night

FENCELINE

Option C

Option B

Worked Example Terminal Options

Transfer releases(D5 weather shown)

Striking release from cargo tank (D5weather)

FN curve for 3 Jetty options

Figure A2 FN Curve For Jetty Options

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1 10 100 1000

Number of Fatalities (N)

Fre

qu

ency

of

Acc

iden

t w

ith

N o

r m

ore

fat

alit

ies

(F)

/yr

Intolerability Limit for Jetty.

OPTION A

OPTION B

OPTION C

Risk Reduction Measures

Risk Reduction Measure Effect on Accident Frequency (f)

Effect on Severity of accident, (Number of people affected (N)

Relocation of Jetty to position where striking of LNG carrier is less likely.

Reduces frequency None

Relocation of Jetty to position where striking of LNG carrier not possible.

Eliminates scenario frequency is zero.

Eliminates high value of N associated with this accident.

Upgrading harbour control system e.g. tugs escort all vessels past LNG jetty.

Accident frequency reduced. Will not reduce N

Upgrading of the leak / gas detection and ESD system on the jetty.

Will not reduce accident frequency.

May reduce the extent of dispersion, reducing N.

Relocate LNG Jetty to an area with lower density of population.

Accident frequency may increase or decrease.

Will reduce number of people affected.

Emergency Response Will not reduce accident frequency

May reduce number of people affected.

Conclusions

• The hazardous events on jettieswith the greatest effect distancesare (a) releases of LNG from shipscargo tanks due to striking and (b)transfer releases. In many casespersonnel (workers and public) maybe located within these effectranges.

• The risk based approach is a way ofdemonstrating that personnel withinthe effect distance are not exposedto an undue level of risk.

• It can also be used to compare jettylocation options and evaluate thebenefit of risk reduction measures.