Gas Fire Hand Out

8/13/2019 Gas Fire Hand Out

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GAS FIRES

Helen Verstraelen

FIRES: what you need to

remember

Fire safety aspects: prevention, protection,detection, combat

Transport of heat

Mecanism of a fire

Flamability, speed of reaction and explosion limits

Fire triangle, fire tetrahedron

Fire risk

Fire development

Fire classes

Causes of fire, fire prevention

Fire detection

Fire fighting: material, methods, installations,

DIFFERENT TYPES OF GASES

LNG: liquefied natural gases:

especially methane; relatively stable

LPG: liquefied petroleum gases:

especially butane and propane

relatively stable

Chemical gases: liquefied inflammable

gases: unsaturated and possible

unstable ex: ammonia, VCM


2/26

CRITICAL TEMPERATURE /

PRESSURE

Critical temperature: the temperatureabove which a gas can not beliquefied, no matter what the pressure.There is no difference between theliquid and the gas: supercritical fluid

Critical pressure: pressure required forliquefaction at the critical temperature

Liquefaction possible by: Cooling down

Compressing (not above criticaltemperature)

Combination cooling and compressing


PRESSURE


PRESSURE

217.7374H2O

31.2

-119

132

critical temperature (C)

73.0CO2

49.7O2

111.5NH3

critical pressure (atm)1 atm = 1.01325 bar

gas


3/26

TRANSPORTATION

Full pressure method: pressurised at

normal temperature. Cargo holds arespherical or cylindrical

Full refrigerated method: low T andpressure just above atmosphericalpressure. Material strength at lowtemperature is important

Semi-refrigerated (semi-pressurised)method: at the boiling temperature andcorresponding pressure

TRANSPORT

TRANSPORT


4/26

METHANE

CH4444

Most important component of LNG

Transported at -165C (boilingtemperature) / 1.04 kg/cm

S.G. liquid: 0.474

S.G. gas: 0.554

Explosion limits: 5.3 - 14%

Flashpoint: low

Self ignition temperature: 595C

Safety and Risks of LNG TransportationSafety and Risks of LNG TransportationSafety and Risks of LNG TransportationSafety and Risks of LNG Transportation

LNG shipping so far has an excellent safetyLNG shipping so far has an excellent safetyLNG shipping so far has an excellent safetyLNG shipping so far has an excellent safetyrecordrecordrecordrecord

No shipboard fatalities over the life of theNo shipboard fatalities over the life of theNo shipboard fatalities over the life of theNo shipboard fatalities over the life of theindustry associated with cargoindustry associated with cargoindustry associated with cargoindustry associated with cargo

No major losses of cargo and only one minorNo major losses of cargo and only one minorNo major losses of cargo and only one minorNo major losses of cargo and only one minorLNG on board fire (lightning strike near ventLNG on board fire (lightning strike near ventLNG on board fire (lightning strike near ventLNG on board fire (lightning strike near ventriser, cargo tanks not affected)riser, cargo tanks not affected)riser, cargo tanks not affected)riser, cargo tanks not affected)

Two groundings resulting in major hullTwo groundings resulting in major hullTwo groundings resulting in major hullTwo groundings resulting in major hullbreaches without cargo lossbreaches without cargo lossbreaches without cargo lossbreaches without cargo loss

BUT you should never rest on your laurels. R&DBUT you should never rest on your laurels. R&DBUT you should never rest on your laurels. R&DBUT you should never rest on your laurels. R&D

programs should continue to search forprograms should continue to search forprograms should continue to search forprograms should continue to search forimprovements.improvements.improvements.improvements.

LNG TRANSPORT

PROPANE

C2222H8888

Transported at -43C / 1.04 kg/cm

S.G. liquid: 0.583

S.G. gas: 1.55

Explosion limits: 2.1 - 9.5%

Flashpoint: - 105C



5/26

BUTANE

C4444H10101010

Transported at - 1C / 1.04 kg/cm

S.G. liquid: 0.602

S.G. gas: 2.9

Explosion limits: 1.8 - 8.5%

Flashpoint: - 60C


LPG

MMMMixtureixtureixtureixture ofofofof gasesgasesgasesgases,,,, mainlymainlymainlymainly propanepropanepropanepropane andandandand butanebutanebutanebutane

SSSStored under pressure totored under pressure totored under pressure totored under pressure to keepkeepkeepkeep itititit in ain ain ain a liquidliquidliquidliquidstatestatestatestate

BBBBoiling pointoiling pointoiling pointoiling point ofofofof LPGLPGLPGLPG varies from aboutvaries from aboutvaries from aboutvaries from about 44C44C44C44Ctotototo 0C,0C,0C,0C, sosososo thethethethe pressure required to liquefy itpressure required to liquefy itpressure required to liquefy itpressure required to liquefy itisisisis considerableconsiderableconsiderableconsiderable

LPG isLPG isLPG isLPG is an attractive fuel for internalan attractive fuel for internalan attractive fuel for internalan attractive fuel for internal----combustion engines because it burns withcombustion engines because it burns withcombustion engines because it burns withcombustion engines because it burns withlittlelittlelittlelittle airairairair pollutionpollutionpollutionpollution andandandand little solid residuelittle solid residuelittle solid residuelittle solid residue,,,, ititititdoesdoesdoesdoes not dilute lubricantsnot dilute lubricantsnot dilute lubricantsnot dilute lubricants, and, and, and, and it hasit hasit hasit has a higha higha higha highoctaneoctaneoctaneoctane rating.rating.rating.rating.

ETHYLENE OXIDE

C2222H4444O

Transported at -11C / 1.04 kg/cm

S.G. liquid: 0.913

S.G. gas: 1.52

Explosion limits: 3 - 100%

Flashpoint: - 57C



6/26


7/26

GAS FIRE

EXPLOSION

Can be mechanical, chemical or nuclear Mechanical: no chemical reaction. Ex:

breaking of vessel containing compressedgas

Chemical: fast exothermic chemicalreaction. Ex: polymerisation, decomposition,fast burning, nuclear..

In case of leakage (gas, liquid) Mixture gas-air and no ignition

Mixture gas-air and immediate ignition: fire

Mixture gas-air and postponed ignition:

explosion

DEFLAGRATION / DETONATION

Deflagration most common

Speed of flames 1 to 1000 m/s (compared

to stationary observer)

Pressure: some bars

Detonation:

supersonic (compared to speed of sound in

non combusted gas in front of the flames)

1500 - 2000 m/s

Shock wave 15 20 bar


8/26

DETONATION

Probability of detonation dependson type of fuel

Very reactive products likehydrogen acetylene or ethylenemight explode when an accidentoccurs

Detonation of a pure mixturemethane / air is not known

POSTPONED IGNITION

Depending on dispersion of gas

cloud

SPECIFIC GRAVITY

Gases transported by ships:

Liquid: lighter than water

Gaseous: often heavier than air, except for

methane, natural gas and ammonia

! Pay attention: influence of

temperature: methane at 110C is as

heavy than air


9/26

SPECIFIC GRAVITY

1.562 at 34C

1.458 at 10 C

0.915 at 60C

0.568 at 104.C

0.599

0.873

0.823

0.464 at 164C

specific gravity liquid to

water (at 25C) or boiling

point

2.486Chlorine - Cl2

2.264Sulfur Dioxide - SO2

1.1763Hydrogensulfide - H2S

0.9683Ethylene(Ethene) -C

2H

4

2.0061Butane - C4H

10

2.6961Benzene- C6H

6

0.596Ammonia -NH3

0.5537 / between 0.6 and

0.7

Methane- CH4

/ natural

gas

specific gravity gas to airgas

DISPERSION OF GAS

DISPERSION OF GAS

Neardeckhouses


10/26

DISPERSION OF GAS

Near

deckhouses

CONTRIBUTING FACTORS

The consequences of a gasfire/explosion depend on: Type of fuel and atmosphere

Dimensions gas cloud and concentration

Mixture

Place of ignition

Power of ignition

Dimension, position and type of venting

Position and dimension of equipment andstructural elements

CONSEQUENCES GAS

LEAKAGE

42 % explosion of gas clouds (inside

and outside)

35 % fire

22 % explosions (uncontrolled

reactions, BLEVES, mechanical

explosions, explosions in equipment

1% evaporation / dilution in air (by

wind)

Garrisson 1988


11/26

PRESSURE JET FIRE

Fire of gas leakage under

pressure : pressure jetfire

VENT MAST FIRE

POOL FIRE

Fire of pool of liquid gaspool fire


12/26

POOL FIRE

Refrigerated transport

About 30% of the leaked product willevaporate; whats left will form a pool

Low temperature may give cracks inthe vessels construction: Spray waterto protect the metal and to avoidheating of the construction

Gas fire: speed of flames 3 x speed offuel fire

POOL FIRE

The flames will be blown away by the

wind

Methane: height flames approximately

3x to 4x diameter pool

Important: reduction of heat effect

Heat will be dangerous over 100C

(electrical isolation will melt at

130C)

POOL FIRE


13/26

POOL FIRE

Pay attention for convection heat(air or water)

Pay attention for radiation heat: Near seat of fire 170 kW/m

Skin problems at 4.7 kW/m

Second degree burns at 6.2 kW/m

Most flammable products catch fire at12 kW/m

FLAMABLE GAS

SENSORS

FLAMABLE GAS

SENSORS

Two ceramic beads (pellistors) withembedded platinum coils are heated to~450C. One pellistor is impregnated with acatalytic material that, at the given

temperature, oxidizes the gas (O(O(O(O2222 must bemust bemust bemust bepresent!!!!)present!!!!)present!!!!)present!!!!) and thus forms additional heatwhich can be detected by measuring theresistance of the platinum coil. Using aWheatstone bridge with a second,deactivated pellistor as a reference, thebridge current is approximatelyproportional to the gas concentration inthe 0%100% range of the lower explosivelimit (LEL).


14/26

FLAMABLE GAS

SENSORS

Advantages: can be calibrated for very largerange of flammable gasses. Methane is often

used for calibration, calculations give resultsfor other gasses, using enthalpy (heatreleased during combustion)

Mixture of flammable gasses: calibrate forleast sensitive gas. That way the detector willerr on the side of safety

Disadvantage:in the presence of lead, sulphur,silicone vapours, halogens the sensor can loseall sensitivity

FLAMABLE GAS

SENSORS

FLAMABLE GAS

SENSORS

The IR measuring principle is based onthe fact that gas molecules are excitedby IR light of a certain wavelength and

so produce vibrations while partlyabsorbing energy from the light.

Compared to the original IR lightintensity, the attenuated intensitywithin a defined fixed optical path is ameasure for the gas concentration. Asecond beam with a wavelength notabsorbed by gas can be used tomeasure the original IR light intensity.


15/26

FLAMABLE GAS

SENSORS

Fluctuation of power of the IR

source, contamination of the mirror

or window, as well as faults caused

by dust or aerosol in the air, affect

the 2 detectors similar

Can be used in a O2 low or free

admosphere!!

FIRE FIGHTING


16/26

FIRE

FIGHTING

FIRE FIGHTING

Water deluge systemfor protection

FIRE FIGHTING

Water monitors


17/26

FIRE FIGHTING

Powderextinghuishing

FIRE FIGHTING

DO NOT EXTINGUISH !!!!! ExceptDO NOT EXTINGUISH !!!!! ExceptDO NOT EXTINGUISH !!!!! ExceptDO NOT EXTINGUISH !!!!! Except

when the seat if the fire is isolatedwhen the seat if the fire is isolatedwhen the seat if the fire is isolatedwhen the seat if the fire is isolatedand the surface is reducingand the surface is reducingand the surface is reducingand the surface is reducing

OROROROR

To safe human life

When the outpouring of the gas can

no longer be controlled by water fog

When fear for expansion exist

FIRE FIGHTING

Goal of fire fighting is thecooling down of: Seat of fire

Dangerous zone downwind (turning of thevessel might be necessary

Equipment exposed to radiation heat

Determine in advance the areas thatneed cooling

Attack the fire from the weather side


18/26

WATER

Seldom used for extinguishing, more for

protection. Never to be used on a liquefied gas pool

(spreading)

Use large jet

Spray a water film on the surfaces thatneed protection

Good housekeeping of the installation isessential (corrosion, ice, salt,...)

EFFECT OF WATER

Extinguishing effect on fire: Cooling: very limited when flashpoint

is lower than the water temperature

Suffocating: volume steam = 1700 xvolume liquid

Emulsification: when not soluble inwater

Dilution: when soluble in water. Use8 20 l/min/m

EFFECT OF WATER

Control of combustion: Even when the fire can not be

extinguished, it can be controlled

Continuous supply of water is necessary:20 l/min/m of the surface on fire

Protection of surfaces: containers: > 10 l/min/m exposed surfaces

superstructure: > 4 tot 10 l/min/m

cables: 12 l/min/m

others: > 10 l/min/m


19/26

EFFECT OF WATER

Prevention of expansion of the fire:

Depending of type of fuel: about 10% of

what is necessary to extinguish the fire

Use the fog position of the nozzles

Immediate availability important

Closed valves need also be cooled

Try to direct the gas cloud and avoid

contact with sources of ignition.

POWDER

3 types often used: Sodium bicarbonate

Potassium bicarbonate

Urea potassium bicarbonate

Very effective for small LNG and LPGfires

Use the powder until all the flames areextinguished

Keep cooling down after extinguishment

POWDER

Gas codes require fixed dry powdersystem which can deliver powder to anypart of cargo area with fixed monitors

and hand held hoses Also jetty manifolds often protectedwith portable or fixed dry powdersystems

Effective for Gas fires on deck

Jet fires on holed pipes

Used for vent mast fires


20/26

POWDER

Every powder has its ownproperties

When used with foam: make surethat the powder does not degradethe foam

When used with water: make surethat the powder does not disolvesin the water

MECHANISM

FIRST:

inhibiting chain reaction (absorption

of free radicals in combustion

process)

Start the reaction by the generation of

active radicals CH2222, OH, O and H

Na en K salts combine with H and OH to

make them rare

Ammonia salts provoke an endothermic

polymerisation reaction

MECHANISM

SECOND: Decrease evaporation by reducing the

radiation heat

Inerting by reducing the oxygen level andwith the production of CO2222

Slowing down the fire due to the formationof a surface film

Negligible cooling effect. Beware forre-ignition. cool down hot surfaceswith water before extinguishing withdry powder.


21/26

POWDER ON BOARD

Never change the type of powder

without consulting the constructor /

designer

Never mix deferent types of powder

Powder can not always be used (not

almighty): not for metal fires, cellulose

nitrate, class A fires if the complete

surface can not be covered with the

fire (no cooling effect)

DISADVANTAGES

When used on electronically equipment,an almost irremovable membrane can beformed at higher T (above 127C) ofhumidity > 50%

Erosion is possible

Visibility almost zero while using powder

Powder can cause breathing difficulties.When used on large surfaces, evacuationis needed

Exercises are necessary for the correctuse of powder

FOAM

Mostly used on surface of pool fires

(when confined in bunded area):

Reduces vaporisation rate

Intensity of the pool fire is limited

Foam depth at least 1 or 2 meter is needed

High expansion foam of about 500 to 1

expansion rate has proven to be the bestfor this purpose


22/26

FOAM

Used on un-ignited pool fires:

Reduces extend of gas cloud Stable foam can freeze at the interface of the

foam-gas cloud and will so reducevaporisation rate. Make sure the right foam isused. If it breaks down into the liquid, it mayincrease the vaporisation rate.

Foam will not extinguish a liquefied gasfire.

Needs to be applied to substantial depth.This is not easy on ships and thereforeonly found on terminals and not on gascarriers.

INERT GAS

Preventional

measures with

IG generator:

Permanently

inerting ofinterbarrier

spaces or

cargo related

spaces

METHANE

CO2

High pressure bottled CO2 in case

of fire in enclosed space

Ventilation stopped, space closed Evacuation needed

CO2 injection produces electrostatic

charging (be aware when used as

precautionary measure in flammable

atmosphere)


23/26

STATIC ELECTRICITY CO2

Incidents:

While attempting to inert a jet fuel tank, byusing a portable CO2 fire extinguisher, anexplosion occurred and killed two navy firemen.

On board a tanker, four people were killed in anexplosion while inerting a naphtha tank usingCO2 cylinders.

In Bitburg, Germany, twenty-nine people werekilled as a result of an explosion whilewitnessing the demonstration of a newlyinstalled CO2 fire-extinguishing system for apartially filled jet fuel tank.

STATIC ELECTRICITY CO2

When liquid CO2 expands up to absolute pressures of lessthan approximately 5 bars, the result is the formation ofsmall particles of solid CO2 (dry ice). As the two-phasesolid/gas flows through the piping, static charges areproduced by the particles rubbing against other particles,between themselves, piping and equipment.

These charges accumulate in the zones that are notearth/grounded at the end of the pipelines, most often invalves and nozzles. The size of these fields, can reachvalues of between 50 and 180 kV/m.

Similarly, static electricity can be generated by the dryice particles after they leave the discharge nozzle.

The pressure and impurities in the CO2, equipmentmaterials in transfer line hoses, etc. all influence the

generation of static electricity.

CO2

Used into safety relief valves or

vent mast fires (after shut down)

CO2 is not a cooling agent.Boundaries must be cooled with

water as re-ignition is possible

with the introduction of oxygen.


24/26

EMERGENCY PROCEDURES

Ship procedures, communication is

vital Plans should deal with:

Missing or trapped personnel

Collision

Grounding

water leakage into hold or interbarrier space

Cargo containment leakage

Cargo connection rupture, pipeline fracture orcargo spillage

Fire in non cargo areas

Fire following cargo leakage

Fire in compressor or motor room


Terminal procedures: Less standardised than on ships

Command of an on-site incident controller,often overtaken by port authority

Incident plans Cargo spillage or fire on board a ship alongside ajetty

Cargo spillage or fire while loading or receivingcargo

Cargo spillage or fire not associated with loadingor receiving cargo


Emergency shut down (ESD)

ship/shore link

Exist on all gas carriers and largeterminals

Communication is essential

Loading: first terminal ESD, then ship

Unloading: first ship ESD, then terminal


25/26


Emergency release systems (ERS) Hand arms

First alarm between predetermined limits

(movements of ships): safe shut down

Second alarm outside these limits:disconnection with limited spillage

2 ball or butterfly valves close in 5 seconds

release coupling opened

arm swings by counter balance

Break-away couplings for hosesFor smaller terminals which work with hoses



Removal of ship from berth Burning ship alongside is less a

hazard if kept alongside where shoreservices can provide assistance

In case of an emergency within theterminal, safe practice to removeship to prevent involvement

Consultation master, terminal, portauthority


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Ship-to-ship transfer Communication between ship

masters vital

One ship can use emergencyresources of other

Sometimes separation better optionto minimise overall risks and allowunobstructed access by fire tugs andsalvage services

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Gas Fire Hand Out

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