This document discusses liquefied petroleum gas (LPG) and liquefied natural gas (LNG), focusing on their fire behavior and control. It notes that LPG and LNG are clean fuels but are also hazardous due to their flammable properties. When released, they can cause pool fires, jet fires, boiling liquid expanding vapor explosions (BLEVE), or unconfined vapor cloud explosions (UVCE) depending on ignition. The document outlines past LPG and LNG incidents and lessons learned. It describes different types of fires and appropriate firefighting methods like dry chemical powder, foam, and water depending on the situation. Special characteristics of LNG fires are also highlighted.

1. LPG/LNG - Fire Behaviour and
Control
New Delhi
National Work-shop on Challenges of Fire Risks in
New Millennium
24 - 25 August, 2000
H P Singh
Dy. General Manager (S&EP)
Indian Oil

2. Energy Consumption
Per capita Energy Consumption in Metric Tonnes
of Oil Equivalent
World 1.5
India 0.3
USA 6.3
Europe 3.1
China 0.7

3. Supply/Demand of Petroleum
Products
YEAR Petroleum Natural
Products Gas
(MMT) (MMSCMD)
2001-02 111 151
2006-07 148 231
2011-12 195 313
2024-25 368 391
15 MMTPA LNG import by 2007

4. LPG/LNG
 Clean Fuel
 Use of LPG in transport sector permitted
 Stricter emission norms will enhance use of
LPG/LNG
Growth rate of Petroleum Sector is around 6%.
LPG demand is expected to increase by 15%.
Natural Gas growth rate is expected to be 11%.

5. Natural Gas
 Domestic supply of Natural Gas is almost
stagnant
 Demand has to be met by large scale import
 Import route
- Pipeline
- LNG (1/600 times volume reduction)
Considering the present political scenario and
energy security imperatives, LNG is the only route
available atleast in medium term

6. LPG/LNG
Success in use of LPG/LNG
depends
on
Safety and Reliability
in
Storage, Transportation and
handling

7. Hazardous Properties of LPG
 Mixture of Propane & Butane
 Colourless & Odourless : difficult to identify
 Vapour Pressure : 16.87 kg/cm2 (max.) at 65 0C
: about 9 kg/cm2 at 38 0C
 Boiling Point : -40 0C - readily vapourises on leakage
 Vapour density : 2.5 kg/m3 (Air 1.29 kg/m3)
Heaviour than air, so vapour cloud settle in the ground
level and travel considerable distance

8. Hazardous Properties of LPG
 Flash Point : - 104.4 0C
 Explosive range in air
Lower 1.9 % by Vol.
Upper 9.5 % by Vol.
 Auto-ignition Temperature : 405 0C
LPG vapour is always much above flash point so highly
hazardous.

9. Hazardous Properties of LNG
 Contains mainly Methane. Typical composition is as
under:
(% Vol)
Methane : 90 - 93
Ethane : 3 - 5
Propane : 2 - 2.5
Butane : 0.4 - 0.5
Pentane : 0.05 - 0.1
Nitrogen : 0.9 - 1.2

10. Hazardous Properties of LNG
 Colourless & Odourless : difficult to identify
 Boiling Point : -161.5 0C - readily vapourises on
leakage
 Molecular wt. of LNG is 17.5 and is much lighter than
air.
 Liquid Density : 450 kg/m3
Since vapour is lighter than air, it diffuses quickly.
LNG is stored at (-) 168 0C. At low temperature, LNG
vapour is heavier than ambient air and hence can
form vapour cloud. This cloud duration will not be
high.

11. Hazardous Properties of LPG
 Explosive range in air
Lower 6.3 % by Vol.
Upper 11.9 % by Vol.
 Auto-ignition Temperature : 537 0C
LNG (Methane) is a flammable gas in ambient condition
and hence highly hazardous.

12. Hazardous Properties of LPG/LNG
 Gas to liquid volume ratio :
LPG : 250
LNG : 600
 Volume of flammable mixture per unit volume of liquid:
LPG : 12000
LNG : 10800

13. Fire Behaviour
Fire is a rapid self sustaining oxidation process
accompanied by evolution of heat and light of
varying intensity.
Supply of fuel, oxygen and heat in right proportion
along with uninhibited combustion chain reaction is
essential for fire to continue.
Fire Fighting is actually the process of breaking up
the combustion chain reaction.

15. Explosion
Generally fuel and oxygen is premix (Vapour cloud)
Combustion reaction is very fast. Rate is not delayed for
bringing fuel and oxygen together.
Rapid increase in pressure characteristic.
LPG/LNG quickly transform into gas on release and as
such can explode.

16. BLEVE
Boiling Liquid Expanding Vapour Explosion
 Major container failure
 Container contains liquid at a temperature above its
boiling point
 Container fails due to excessive pressure :
 Liquid full
 Temperature of the liquid increases and no relief
valve
 Un-wetted portion of the shell gets heated up and
metal loses its strength. Vessel ruptures with
disasterous effect. Fire ball results.

17. LPG Liquid
LPG Vapour

18. BLEVE
 Relatively less number of fragments are generated
 Fragments fly as missile by the energy released by the
expanding gas. Speed of these fragments are very high
and cause extensive damage to life and property.
 60% of the expanding energy of LPG is converted to
kinetic energy. Maximum initial velocity is
- Horton Sphere : 200 m/sec
- Bullet : 150 m/sec
 In case of LPG, distance reached by fragments are as
under:
- Horton Sphere : 600 M
- Bullet : 1200 M
Fragment from one BLEVE can initiate a BLEVE in the nearby second vessel.

19. UVCE
Unconfined Vapour Cloud Explosion
 Release of flammable vapour in atmosphere
 Mixing with air
 Totally within flammable range or the outer layer is
within flammable range
 Delayed ignition
 Flash Fire of UVCE depending on quantity and mixing
with air
 High pressure lasts only fraction of a second. Persons
are not killed due to blast.
 Secondary effects cause death and destruction.

20. UVCE
Over Pressure Likely Damage
(Bar)
o.3 Heavy (90 % houses destroy)
0.1 Repairable (10 % houses damage)
0.03 Damage of glass
0.01 Crack of windows

21. LPG : Incidents
BLEVE OF LPG Cylinder
 1983 in Sakurbasti LPG Bottling Plant.
 LPG Cylinder body valve leaks. Vapour cloud forms.
 Contractor labour attempts to light ‘beedi’.

22. LPG : Incidents
BLEVE OF LPG Bulk Tank Truck
 07.08.94, near Bhusaval. LPG TT overturn.
 Liquid/vapour line got damaged and LPG started
leaking
 Impingement of LPG jet to metallic surface of the
vessel.
 Static electricity acted as source of ignition.
 BLEVE of LPG TT.
 Loud sound upto 3 KM. Vessel fragments into 4 parts.
One piece traveled upto 350M.
 Truck driver alerted the local people and stopped
traffic on the National Highway. Hence, no casualty.

23. LPG : Incidents
BLEVE OF LPG Bulk Tank Truck
 14.01.96, near Godhra (Gujarat). LPG TT head on
collision with other truck (soyabean husk) at 0445
hrs.
 LPG leakage from safety valve. Fuel tank of TT
damaged and HSD spill on the road.
 A matador hits the liquid/vapour line. LPG started
leaking. Vapour cloud forms.
 Probably somebody in the matador lights match-
stick for light. Result is ignition of vapour cloud. Fire
in the safety valve which impinges on the top surface
like a jet.
 BLEVE of LPG TT.
 Vessel fragments into 3 parts. One dished end
traveled upto 80 M.
 7 persons died.

24. LPG : Incidents
BLEVE in LPG Storage Facility
 19.11.84, Sun Juan, Mexico City. PEMEX lPG storage
and distribution facility.
 Series of explosions and fires.
 500 killed. 7200 injured of which 144 died in hospital.
39000 homeless.
 Facility consists 6 Horton Spheres, 48 Bullets. 11000
m3 LPG at the time of the incident.
 One pipeline (8”) from refinery leaks. Vapour cloud is
formed which moves 100 M and reaches a ground
flare.
 Explosion took place. Recorded in the seismograph
of Mexico City University (30 KM away).
 Flame impingement caused rupture of
spheres/bullets. Result is BLEVE.

25. LPG : Incidents
BLEVE in LPG Storage Facility
 Only 4 bullets remained on support.
 2 HS did not explode but collapsed through buckling
of their legs.
 One fragment traveled upto 1200 M.
 Houses were completely destroyed upto 300 M.
Some of the shortcomings observed:
 Fire Water capacity - inadequate
 Fire Pump-House within 50 M of the LPG storage
 Spheres and Bullets nor provided with Water Spray
 Supports were not fire-proofed
 Spheres and Bullets were spaced very closely.
 Settlement were very close to the facility.

26. LPG : Incidents
Fire/explosion in LPG Storage Facility of a Refinery
 14.09.97, 06.40 AM, LPG storage facility of an Indian
refinery.
 Fire/explosion took place.
 60 persons killed. 27 storage tanks and 15 buildings
including Fire Station and process control room
destroyed LPG storage area damaged.
 LPG was being unloaded from a tanker. Line-fill water
was displaced into a Hortonsphere.
 Problems experienced during water draining. LPG
comes out from the sphere through the water drain
line.
 Vapour cloud forms. It was detected by Operating
personnel.

27. LPG : Incidents
 Small fire in a process unit occurred at that time.
Either this fire or Canteen acted as a source of
ignition.
 Massive explosion and subsequent fire took place.
Major lesson learnt :
 Water draining of LPG vessel is an extremely
hazardous activity. Competent operating person
must be present during water draining.

29. LNG : Incidents
 20.10.44. Cleveland Ohio, USA. LNG storage tank
ruptures. LNG vapour ignites and intense fire result.
Liquid LNG flows through Storm water sewer and
explode.
 128 killed. 200-400 injured. Facility closed down.
 Esat Ohio Gas Company liquefy Natural Gas during
low demand and store which is gassified and
supplied during peak period.
 Metallurgy of the vessel (low carbon steel) was
unsuitable. Vibration or seismic shock might have
developed crack.
Major lesson learnt :
 Provision of dyke is essential for LNG storage..

30. LNG : Incidents
 06.10.79. Cove Point, USA. Explotion occurred in
electrical substation of an LNG facility.
 1 operator killed and 1 injured. Extensive damage to
the substation..
 LNG leaked through an inadequately tightened LNG
pump electrical penetration seal, vapourised,
passed through 200 ft of underground electrical
conduit and entered the substation.
 Normal arcing in the substation caused explosion.
Major lesson learnt :
 Gas detectors to be provided to all buildings of LNG
facility..

31. LPG/LNG : Types of fires
 LPG leakage
 Small - evaporate (heat from ground and surrounding air)
 Large - evaporation and accumulation of liquid on ground
 Immediate ignition
 Pool Fire
 Jet Fire
 BLEVE
Heat Flux Damage Effect
(kw/m2)
5.0 Skin burns in 30 seconds
12.6 Minimum for ignition of wood
31.5 Destruction of metal structures
Heat flux of jet fire is very high (300 - 400 kw/m2). Can cause
extensive damage to pipelines, vessels and equipment.

32. LPG/LNG : Types of fires
 Delayed ignition
Released liquid evaporate and disperse.
Dispersion depends on density of gas and
meteorological conditions (wind speed & temperature)
LPG vapour is heavier and tend to spread in radial
direction due to gravity. Gas pool with certain
height and diameter results. At a distance from the
gas pool, dispersion takes place according to
atmospheric stability and equilibrium is reached.
So the area in which concentration within the
explosive limits does not extend far outside the
edge of the gas pool.
On ignition, vapour cloud burns very quickly.
Anybody inside the cloud burnt to death. Duration
is short. No major thermal damage. Damage is
primarily caused by pressure wave.

33. RELEASE
OF LPG
Immediate
Ignition
Vapourisation
Dispersion
Delayed
Ignition
No Effect
BLEVE
Flare
Pool Fire
DAMAGE
Pressure
Wave
Flash Fire Explosion
DAMAGE
No
Yes
No
Yes
No
Yes

34. LPG/LNG : Types of fires
Some special features of LNG:
 Small leak will immediate vapourise.
 In case of large spillage, rapid vapourisation takes
place for 20-30 seconds. Then vapourisation takes
place near the boiling point of Methane (- 161.5 0C). At
this temperature, Methane is heavier than ambient air.
 In case of immediate ignition, momentary flash fire
occur. There is no over pressure. In case of delayed
ignition, initial burning rate is very high, then the heat
incident on liquid generates enough vapour to sustain
burning and steady-state is achieved. There is no
blast over pressure.
Fire fighting operation shall not add hot fire fighting
agent to the liquid pool.

36. LPG/LNG : Types of fires
 LNG burns with a clear flamme but LPG flames are
smoky.
 Smoke shrouds flame from target and reduces
emissive power of flame surface.
- LNG: 150 - 200 kw/m2
- LPG: 20 kw/m2
Smoke may appear in LNG fire only when pool
diameter is large and most of the fuel has been
consumed so that proportion of higher hydrocarbons
are increasing rapidly.

37. Fire control & mitigation measures
HALON
 Halon is excellent fire fighting agent for gas fires bit
cannot be used due to environmental considerations.
DCP
 Dry Chemical Powder (DCP) is very effective for small
fires. Large fires cannot be extinguished as
application will be difficult.
 Even small fire should not be extinguished fully, if
fuel cannot be completely isolated. Vapour cloud is
more dangerous than small fire.
 Potassium-bi-carbonate based powders are more
effective than Sodium-bi-carbonate based powders.

38. Fire control & mitigation measures
FOAM
 Good quality, high expansion foam (1:500) reduces
intensity of fire greatly.
 Foam alone cannot extinguish the fire as LPG/LNG
fires generate enough heat to generate sufficient
vapour to sustain combustion at the foam surface.
 Foam aids vapourisation of LNG. Heating effect of
foam is detrimental.
 Foam generation facility has to be near the fire.
 Foam cannot flow more than 50 M.
 Depending on the situation, foam can be used on
LNG fire. It will quickly freeze at the interface. Fire
intensity reduces to a great extent. Remaining fire
can be extinguished with DCP.

39. Fire control & mitigation measures
WATER
 High specific heat and cheaply available in large
quantity. Effectively used for cooling and radiation
exposure protection.
 Medium velocity water spray systems shall be
provided in the storage and handling facility for
exposure protection. It has to be automatic.
 High speed, high volume water spray is effective for
dispersion of vapour cloud. Water droplet heats the
vapour and natural buoyancy helps dispersion.
Water shall not be applied to ignited or unignited
LPG/LNG liquid.

40. Fire control & mitigation measures
Some special features of LNG:
 Since vapourisation reduces automatically to a great
extent after few seconds, zone of flammable mixture
is limited. So dyke must be provided to restrict spill
area.
 Burning characteristic and radiant heat output of LNG
pool fire is almost similar to gasoline fire. LNG
burning rate is no more than gasoline on weight
basis.
 Once fire fighting operation starts, it shall extinguish
the fire totally in one go otherwise the fire fighting
agent will reach the liquid pool and generate more
vapour.
 Since autoignition temperature is high, chance of
reignition is low.

41. Fire control & mitigation measures
Formation of vapour cloud is a dangerous occurrence.
If size is large, probability of finding an ignition source
is near certain. Ignition source is so varied, it will be
practically impossible to exclude all source particularly
in industrial situation. All care should be taken to
prevent loss of containment.
While designing facilities, following OISD codes may be
referred:
 OISD-STD-144 : LPG Bottling Plant Operations
 OISD-RP-158 : Storage and Handling of Bulk LPG
 OISD-STD-163 : Process Control Room Safety
 OISD-STD-194 : Storage and Handling of LNG

42. Fire control & mitigation measures
Some of the important measures to be adopted are as
under:
 Automatic Water Spray System.
 Fire proofing of supports of LPG vessels. LPG vessels
may be fire proofed so that more time is available to
arrange for evacuation and taking preventive
measures.
 New LPG facilities shall be mounded type so that
chance of BLEVE is negligible.
 Remote Operated Valve (ROV) for isolation.
 Blast resistant type control room.

43. Fire control & mitigation measures
Do’s
 Evacuate all persons form vapour cloud.
 Approach fire from up wind only.
 Activate ROV to isolate storage.
 Start water spray system for nearby facilities also.
 Keep portable DCP extinguisher near LPG/LNG
handling facilities.
 Water draining from LPG pressurised storage must be
done by competent person.
Don’ts
 Do not allow naked flamme, smoking, welding/cutting
etc. near LPG/LNG facility
 Do not extinguish the fire completely unless fuel can
be isolated.

44. Thank You