2. 2
RISK CONCEPT
Risk is defined as the uncertainty of occurrence of
any unforeseen event/activity in relation to the likelihood
that may occur
Risk comprises of two variables
Magnitude of consequences Likelihood of occurrence
3. - The ALARP Principle
Risks are only tolerable provided that :
It can be demonstrated that all
Reasonably Practicable measures
have been implemented to reduce the risks.
A reasonably practicable risk reduction measure is one where
the costs of implementation are not grossly disproportionate
to the risk reduction benefits achieved.
RISK ASSESSMENT AND CRITERIA
4. 4
Hazards
Vapour cloud formation and explosion
Damage due to over pressure
Fires Thermal damage
BLEVE
- Overpressure
- Rocketing tank parts
- Fire ball
5. FIRE:
FIRE IS A CHEMICAL CHAIN
REACTION COMBUSTION PROCESS INVOLVING
A DEFINITE PROPORTION OF FUEL, HEAT AND
OXYGEN, LIBERATING HEAT & LIGHT OF
DIFFERENT CAPACITIES ALONGWITH OTHER
PRODUCTS OF COMBUSTION.
WHAT IS FIRE ?WHAT IS FIRE ?
Fire is a phenomenon which evolve heat and light energy upon burning
a carbonaceous material.
Chemically, it is an exothermic chemical reaction resulting from the
combination heat, fuel and oxygen.
Fire involves rapid oxidation at high temperatures accompanied by the
evolution of highly heated gaseous products of combustion and
emission of visible and invisible radiation
6. FIREFIRE
FIRE IS A RAPID, SELF-SUSTAINED OXIDATION PROCESS ACCOMPANIED BY THE
RELEASE OF ENERGY IN THE FORM OF HEAT AND LIGHT OF VARYING INTENSITY.
FIRE RESULTS FROM THE COMBINATION OF FUEL, HEAT AND OXYGEN. WHEN A
SUBSTANCE IS HEATED TO A CERTAIN TEMPERATURE CALLED THE ‘IGNITION
TEMPERATURE’ THE MATERIAL WILL IGNITE AND CONTINUE TO BURN AS LONG AS
THERE IS FUEL, THE PROPER TEMPERATURE AND A SUPPLY OF OXYGEN (AIR).
7.
8. OxygenOxygen HeatHeat
FuelFuel
OXYGEN SOURCEOXYGEN SOURCE HEAT SOURCESHEAT SOURCES
Approx. 16% Required
Normal air contains 21% of oxygen
Some Fuels contains its own oxygen
supply
GASES
To Reach Ignition Temp.
Open Flame, the Sun,Hot Surface,
Sparks & Arcs, Friction, Chemical
Action, Elec. Energy,& Gas
Compression
LIQUIDS SOLIDS
Natural Gas, Propane,
Butane,Hydrogen,
Acetylene, CO
Gasoline, Kerosene,
Turpentine, Alcohol, Paint,
Varnish, Olive oil, Lacquer
Coal, Wood, Paper,
Cloth, Wax, Grease,
Leather, Plastic, Sugar,
Grain, Hay, Cork
FIRE TRIANGLEFIRE TRIANGLE
11. AN APPROXIMATE ANALYSIS SHOW THAT ABOUT TWO-THIRDS OF THE HEAT RELEASE
PASSES OFF TO THE SURROUNDING ENVIRONMENT AS SENSIBLE HEAT OF THE EFFLUENT,
AND ONE-THIRD AS RADIATIVE HEAT FLUX.
THE MECHANISM OF FIRE
FUEL + OXYGEN + ENERGY FIRE (LIGHT + HEAT + PRODUCTS OF
COMBUSTION).
IF WE REPRESENT A HYDROCARBON BY THE RADICALS ‘R*’ THEN, A FUEL CAN BE
EXPRESSED AS ‘R-H’. DURING COMBUSTION:
R-H + ½ O2 R* + OH*.
THIS OH* RADICAL IS VERY REACTIVE AND WILL REACT WITH FURTHER FUEL MOLECULES TO
CONTINUE THE COMBUSTION PROCESS.
AN APPROXIMATE ANALYSIS SHOW THAT ABOUT TWO-THIRDS OF THE HEAT RELEASE
PASSES OFF TO THE SURROUNDING ENVIRONMENT AS SENSIBLE HEAT OF THE EFFLUENT,
AND ONE-THIRD AS RADIATIVE HEAT FLUX.
Liquid Fuel Can Still Burn When O2 Level Drop to 15%, But Ceases to Burn When it Reaches at 10%.
Solid Fuel Can Still Burn When O2 Level Drop to 6%
12. SCIENCE OF FIRE- FLAME TEMPERATURE
• Red
– Just visible: 525 °C (980 °F)
– Dull: 700 °C (1,300 °F)
– Cherry, dull: 800 °C (1,500 °F)
– Cherry, full: 900 °C (1,700 °F)
– Cherry, clear: 1,000 °C (1,800 °F)
• Orange
– Deep: 1,100 °C (2,000 °F)
• Yellow
– Clear: 1,200 °C (2,200 °F)
• White
– Whitish: 1,300 °C (2,400 °F)
– Bright: 1,400 °C (2,600 °F)
– Dazzling: 1,500 °C (2,700 °F
13. CLASSIFICATION OF FIRE
• wood
• cloth
• paper
• rubber
• many plastics
• Gasoline
• oil
• grease
• tar
• oil-based paint
• lacquer
Solid Cellulose materials
Hydrocarbon Liquids
C
• Ethylene
• Propylene
• Hydrogen
• Other Flammable gases
Flammable Gases
D
• magnesium
• sodium
• potassium
• titanium
• zirconium
• other flammable metals
Combustible metals
14. CLASS
OF FIRE
DESCRIPTION EXTINGUISHING MEDIUM INDIAN
STANDARD
A Fire involving ordinary combustible materials like
wood, paper, textiles, etc. Where the cooling effect
of water is essential for the extinction of fires
• Water 934-1976
940-1976
6234-1971
B Fire inflammable liquids like oils, solvents,
petroleum products, varnishes, paints etc. where a
blanketing effect is essential
• Foam
• carbon dioxide
• dry chemical powder.
933-1976
2878-1976
2171-1976
(4308)-1982
C Fires involving gaseous substances under
pressure where it is necessary to dilute the burning
gas at a very fast rate with an inert gas or powder.
• Carbon dioxide
• dry chemical powder.
• Container is kept cool with
water spray
2878-1976
2171-1976
(4308)-1982
D Fires involving metals like magnesium, aluminum,
zinc, potassium etc. where the burning metal is
reactive to water and which require special
extinguisher media or technique
• Special dry powder TEC 2171-1976
(4861) – 1968
*As per IS:21901979
CLASSIFICATION OF FIRE & SUITABILITY OF EXTINGUISHING MEDIA
15. FIRE EXTINGUISHER-METHOD OF
OPERATION
• The final rule is to always position yourself with an exit or means of
escape at your back before you attempt to use an extinguisher to put
out a fire.
16. FIRE EXTINGUISHER-CARBON DI-OXIDE
• Fire Extinguisher Carbon Di-Oxide
• CLASS B FIRE : Petroleum, Oil, Diesel, Paint, Varnish, Solvent,
Aviation Fuel, Flammable and volatile liquids etc.
• CLASS C FIRE : Flammable Gases,
• Live electrical Equipments, Industrial Gases, Electrical
Installation,
• Power Grid Computer Room etc.
Description BIS Spec. Discharge
Time (sec.)
Jet Length
(M)
Test
Pressure
(kg/cm2)
Co2- 4.5 Kg. 2878 20 - 24 2.5 250
Co2 - 6.5 Kg. 2878 25 - 30 2.5 - 3 250
17. FIRE EXTINGUISHERS –D.C.P
• Suitable For CLASS B & C Fires Involving
Flammable Liquid Petroleum products,
Flammable Gases.
• Work Effectively And Rapidly On
Plastics & Electrical Fires.
Description BIS Spec.
Discharge
Time (Sec.)
Jet Length
(Meters.)
Test
Pressure
kgf/Cm2
DCP– 5 Kg
DCP- 10 Kg
2171
2171
15 – 20
25 – 30
4 – 5
5 – 6
30
30
19. Explosion – rapid expansion of gases resulting in a rapid moving pressure or shock
wave.
Mechanical Explosion – due to failure of vessel with high pressure non reactive gas.
Explosions
• Detonation – explosion (chemical reaction) with shock
wave greater than speed of sound
• Deflagration – explosion (chemical reaction) with shock
wave less than speed of sound
• BLEVE – Boiling Liquid Expanding Vapor Explosion –
when liquid is at a temperature above its atmospheric
boiling point. Vessel ruptures – flammable liquid flashes
and results in a fire/explosion
20. Explosions
• Confined explosion – an explosion occurring
within a vessel or a building. Usually results in
injury to the building inhabitants and extensive
damage.
• Unconfined explosion – an explosion occurring
in the open. Usually results from spill of a
flammable gas spill. These explosions are rarer
than confined since dilution occurs.
21. Understanding Fire and Explosion
Combustion = ƒ (FL, Minimum Ignition Energy (MIE), Surface Area)
Philosophy of Combustion
22. Understanding Fire and Explosion
Fire occurrence step
1. Jet Fire
2. Flash Fire
3. Pool Fire
4. Fireball
23. FRAMEWORK OF RISK ASSESSMENT ON FIRE AND EXPLOSION HAZARDS
Consequences flow diagram
24. Understanding Fire and Explosion
Explosion occurrence step
Explosion
Physical Explosion Chemical Explosion
1. Overpressure
2. BLEVE - Fireball
3. RPT
4. UVCE/CVE
1. Runway reaction
25. Understanding Fire and Explosion
Physical Properties Key Factor of Flammable
1. Boiling Point
2. Vapor Pressure
3. Flash Point
4. Auto ignition
5. Enthalpy of Combustion (ΔHc)
6. Minimum Ignition Energy
7. Density
8. Conductivity of material
9. Size of material
26. Understanding Fire and Explosion
Environmental Properties Key Factor of Fire /Explosion
1. Operational Parameter (Pressure, Flowrate, Temp, etc)
2. Lay-out of unit process/equipment
3. Installation (congested, confined, etc)
4. Source of heat (open fire, conductive heat, static electric, etc)
5. Meteorogical condition (Wind speed, direction, etc)
6. Leakage dimension (bore, rupture, hole, etc)
27. Understanding Fire and Explosion
Impact of Fire & Explosion
1. Breakage the molecular bond
2. Heat Flux / Heat Radition
3. Poisonous Gas
4. Blast Wave/Shock Wave
5. Debris trajectory/projectile
28. • Fixed Fire Protection Systems
• Mobile Fire Protection Systems
• Portable Fire Protection Systems
• Communication system
FIRE PROTECTION SYSTEMS
29. •Fire water reservoirs
•Fire Water Pumps
•Fire water network, hydrants and monitors
•Deluge water spray system.
•Manual water spray system
•Foam system
-Semi-fixed foam pourer system
-Rim-seal foam package system
•Gaseous extinguishing system
•Fire and Gas Detection system.
FIXED FIRE PROTECTION SYSTEMS
30. F&G Field Devices
• Hydrogen Gas detector
• Toxic gas detector – H2S, Chlorine
• Flame detector
• Heat detector
• Gas detector open path
• Linear heat detector
FIRE AND GAS DETECTION SYSTEM
31. FIRE DETECTION
A fire has four stages and detectors are designed depending on
the characteristics of fire at each of these stages. the four stages
are:
• Incipient stage: at this stage there is no significant smoke, heat
or flame. invisible products of combustion are released at this
stage.
• Smoldering stage: the material starts giving out smoke.
however, no flame is seen.
• Flame stage: ignition causes rapid burning, flames become
visible and the volume of smoke given out decreases.
• Heat stage: ignition causes the material to become very hot and
emit heat rays, smoke in small quantity and flame become
prominent. toxic gases produced as a result of combustion are
also given off.
33. Overview
• Elements of Fire Prevention Planning
• Identifying fire hazards
• Prevention Strategy
• Related Training
34. ELEMENTS OF FIRE PREVENTION PLANNING
• List all major fire hazards.
• Proper control of hazardous materials
– including flammable and combustible liquids.
• Control potential ignition sources.
• List fire protection equipment.
• Regular inspection and maintenance.
• Responsible employees for fuel sources.
35. FIRE EMERGENCY TRAINING
• Inform employees of the following:
– Fire hazards in their work area.
– Protection measures specific to them.
– Fire Prevention Plan requirements.
• Portable Fire Extinguisher Training
• Emergency Procedures Training
• Compressed Gas Cylinder Awareness
• Electrical Safety
36. ACTION IN CASE OF FIRE
The following sequence of action is to be taken if one happens to
observe an accidental fire anywhere at a plant site:
• raise an alarm and warn people nearby.
• inform control room and fire station.
• locate suitable first aid fire extinguishers nearby and apply the
extinguisher on the fire.
• Always listen emergency message announcements carefully.
• in case you are not successful in putting out the fire, escape to
a safer place and wait for fire station personnel to arrive.
• Don’t be panic.
• provide assistance to the fire station personnel and security
personnel in case your help is required in evacuation or
removing the injured to the hospital.
