FIRE IT’S CAUSES &

CONTROL

OBJECTIVES:

1. Understand the combustion process.

2. Understand the classification of Fire.

3. Principle of fire extinguishment.

4. Understand fire extinguisher types, operating procedures, capabilities and limitations.

Fire, also known as combustion, is the process of rapid oxidation at high temperatures. This releases hot gases, light, and invisible forms of radiation energy.

Three elements are necessary for initiation of fire:

1. Fuel in the form of vapour, liquid or solid.

2. A source of ignition sufficient to initiate & propagate the fire.

3. Oxygen in sufficient proportion to form a combustible mixture.

FIRE

BASICS OF FIRE

Removal of any side of the triangle or breaking the chain reaction between the transient chemical species formed following ignition will extinguish a fire.

COOLINGSMOOTHERING

STARVATION

FIRE TRIANGLE FIRE TETRAHEDRON

BASICS OF FIRE

Combustion process is observed in two modes.

For flaming combustion to occur, solid or liquid fuel must be

converted into a vapour, which then mixes air and reacts with

oxygen.

Smoldering combustion, on the other hand, involves a reaction

between oxygen and the surface of the fuel: this is a complex

process and in general occurs with solid fuels which char on

heating.

BASICS OF FIRE

Fire extinguishment involves removal or limiting of one or more of the factors described by the fire triangle.

The method of extinguishment of fire may be classified under the following heads:

Principle of Extinguishment of Fire

Starvation : Elimination Of FuelSmothering : Limiting Oxygen SupplyCooling : Limiting Rise Of Temp. Chain Breaking : Limiting Chain Carriers

BASICS OF FIRE

Removal of Fuel

The removal of fuel is not always possible. However, in the case of liquid fuel fires caused by leaking pipes or fittings, the fuel supply should be closed.

It may also be possible to drain the fuel from a burning tank.

It is particularly important to shut off the supply in a gas fire. However, gas could also be left burning in a controlled manner to exhaust itself.

In accommodation spaces, combustible materials should be removed from the vicinity of fire, including any adjacent compartment affected by the heat.

BASICS OF FIRE

Removal of Heat

A reduction in temperature is achieved by the use of a suitable cooling medium, normally water, at a sufficient rate.

Cooling of boundary bulkheads will reduce the possibility of igniting material outside the affected compartment.

Heat can also be absorbed by decomposition of dry powder. The source of power should be cut off in electrical insulation.

BASICS OF FIRE

Removal of Oxygen

Except in those substances that contain their own oxygen, the removal of sufficient oxygen will extinguish a fire.

In fire extinguishing operations, oxygen is extinguished by smothering the fire with a layer of foam.

Oxygen is also cut off during the operation of portable and semi portable carbon dioxide extinguishers and to some extent, during he operation of dry powder extinguishers.

But for CO2 and dry powder, the smothering action is temporary and there is a possibility for re- ignition.

BASICS OF FIRE

The Fire Tetrahedron Model

Fire requires four elements in order to start and continue to burn.

The forth element of fire is a self-sustaining chemical reaction called "combustion" that produces continued heat that serves to keep the fire burning.

To help illustrate that these four elements must occur together in order for a fire to exist, the 4-sided pyramidal shaped tetrahedron model was developed.

Remove any one of these elements from the fire tetrahedron and the fire will not start or, if already burning, will be extinguished.

BASICS OF FIRE

Breaking the Chain Reaction

A fire may be extinguished by breaking the chain reaction between momentary chemical species (radicals) produced on ignition (these species are described as 'transient' since they are not present prior to ignition or in the final products of combustion).

For instance, Halogenated hydrocarbons (Halons) and dry powders attack the structure of the species and prevent their reaction by killing the flame, sometimes in less than one hundredth of a second.

The destruction takes place without any appreciable removal of heat, fuel or oxygen.

However, the remaining three sides of the tetrahedron will still be present and, unless the heat is removed, there is a danger of re-ignition of the concentration of extinguishing agent is not maintained.

BASICS OF FIRE

The term "free radical" or "radical" is used to mean an atom or group in which one of the bonding orbitals is occupied by a single electron. Radicals are normally uncharged.

Free Radical Reaction during fire:

BASICS OF FIRE

Extinguishment Mechanism Of DCP Sodium Bicarbonate: When DCP enters the combustion zone, it

decomposes by the heat of the flame to liberate water, water vapours and carbon dioxide.

2 NaHCO3 ------- Na2CO3 + H2O + CO2 The sodium Carbonate further decomposes to give

Na2CO3 -------- Na2O + CO

Na2O --------- 2NaOH (in presence of H radicals) Sodium Hydroxide produced during last step reacts with H & OH radicals

which are active in fire to give water vapours.

NaOH + H ------- Na + H2O

NaOH + OH ----- NaO + H2O Also

NaO + H ------- NaOH

Na + OH ------- NaOH This way all the H and OH radicals in fire are removed by breaking the chain

reaction and thus extinguish the fire.

BASICS OF FIRE

Different Fire Extinguishing Media:

Sand

Water

Dry Chemical Powder

Inert Gas

CO2 Gas

Steam

AFFF (Aqueous Film Forming Foam)/ ARFFF

Clean Agent System (FM-200)

BASICS OF FIRE

Types of Fire Extinguishers Water The Water Extinguisher extinguishes the fire by cooling the

fuel below its ignition temperature. Water is very effective cooling medium also easily available

everywhere. The water extinguisher is very effective on A class fires but is

ineffective and dangerous on other classes of fire. It must not be used on electrical fires as water is an excellent

conductor of electricity.

Carbon Dioxide Carbon Dioxide (C02) is a colourless, odourless, and tasteless

gas that is heavier than air and does not support life. It is not a toxic gas.

The CO2 extinguisher relies on its ability to displace or dilute the Oxygen around the burning material smothering the fire.  

BASICS OF FIRE

Dry Chemical Powder The Dry Chemical Powder (DCP) fire extinguisher is probably

the most versatile extinguisher available today. DCP extinguishers extinguish fires by smothering, and

interfering with the chemical chain reaction of burning. They provide a rapid knockdown on a range of fires.

DCP mainly contains Potassium or Sodium Bicarbonate with stabilizers.

Foam Fire Extinguisher The Foam extinguisher is suitable for the extinguishments of

class B (flammable liquid) fires. Foam provides a lasting blanket, which floats on

the burning fuel and smothers the fire. In addition to its ability to extinguish fires, the foam

extinguisher can be used as a vapour suppression barrier over spills of flammable liquids.

BASICS OF FIRE

Classes of fire:

Class A fires - are fires involving organic solids (like paper, wood, coal, cloths, dry grass etc.)

Best Extinguishing media-waterClass B fires - are fires involving flammable Liquids

(like Petrol, diesel, kerosene, naphtha etc.) Best Extinguishing media-foam, carbon dioxide, DCP

Class C fires - are fires involving flammable Gasses (like LPG, CNG, NG, H2 gas etc.)Extinguishing media - Carbon dioxide, DCP. The best way to extinguish such fires is by stopping the flow of fuel gas to fire. Container is kept cool with water spray.

Class D fires - Fires involving metals like magnesium, aluminum, zinc, potassium etc. Where the burning metal is reactive to water and which require special extinguishing media.(like Na, K, Mg, Al etc.)Extinguishing media- special dry powder.

BASICS OF FIRE

Classification of FireA Ordinary Combustible Material C Flammable Gases

B Flammable LiquidsD Combustible Metal

D

• gasoline• oil• grease• tar• oil-based

paint• lacquer• flammable

gases

• LPG• H2

• magnesium• sodium• potassium• titanium• zirconium• other

flammable metals

• wood• Cloth• Paper• Rubber• Many

plastics

BASICS OF FIRE

Electrical fire

Electrical fires are not treated as a class of their own, since

any fire involving, or started by, electrical equipment must, in

fact, fall into one of the other categories.

The normal procedure for dealing with an electrical fire is to

cut off electricity and use an extinguishing media appropriate

to what is burning.

BASICS OF FIRE

Common Fire Definitions:

Backdraft -- The beginning of a backdraft occurs from a fire in a structure being poor presence of necessary oxygen. The fire smolders giving off unburned carbon particles and other flammable products. Then, suddenly the smoldering fire is given a sudden influx of oxygen causing combustion to restart possibly at devastating speeds consistent with an explosion.

Flash Point -- The minimum temperature at which a liquid fuel gives off sufficient vapors to form an ignitable mixture with the air near the surface. At this temperature, the ignited vapors will flash but will not continue to burn.

Ignition Temperature -- The minimum temperature to which a fuel in air must be heated to start self sustained combustion without a separate ignition source.

BASICS OF FIRE

• Explosive limits are those concentrations of a vapor or gas in air

below or above which propagation of a flame does not occur on

contact with a source of ignition.

• The Lower Explosive Limit (LEL) is the minimum concentration

below which the vapor air mixture is too lean to burn or explode.

• The Upper Explosive Limit (UEL) is the maximum concentration

above which the vapor air mixture is too rich to burn or explode.

Explosive limits

BASICS OF FIRE

BASICS OF FIRE

BASICS OF FIRE

Classification of Petroleum Products

Class – a : liquid which have flash point below 23oc.

Class – b : liquids which have flash point of 23oc and above but

below 65oc

Class – c : liquid which have flash point of 65oc and above but

below 93oc.

Excluded petroleum : liquid which have flash point of 93oc and above.

LPG do not fall under this classification but form separate category.

BASICS OF FIRE

S. NO.

MATERIAL AUTO IGNITION TEMPERATURE oC

FLASH POINT OC

EXPOSING RANGE VOLUME % IN AIR LOWER LIMIT UPPER LIMIT

1 CRUDE OIL DEPENDS UPON THE NATURE OF CRUDE

19 DEPENDS UPON THE NATURE OF CRUDELEL UEL

2. HYDROGEN 585 GAS 4.1 74.0

3 METHANE 538 GAS 5.0 15.0

4 ETHANE 514 GAS 3.0 12.5

5 PROPANE 466 GAS 2.4 9.5

6 BUTANE 430 GAS 1.5 9.0

7 BENZENE 563 -11 1.3 7.1

8 TOLUENE 536 4.5 1.2 7.2

9 NAPHTHA 288 -18 1.1 5.9

10 GASOLINE 245 -7 1.4 7.6

11 ATF 254.4 38 0.7 5

12 SKO 254 35 0.7 5

AUTO IGNITION, FLASH POINT AND EXPLOSIVE LIMITS OF SOME OF THE PETROLEUM PRODUCTS

S. NO.

MATERIAL AUTO IGNITION TEMPERATURE

FLASH POINT OC

EXPOSING RANGE VOLUME % IN AIR LOWER LIMIT UPPER LIMIT

13 HSD 256 32 0.7 5

14 LDO - 66 - -

15 LSHS 316 66-166 - -

16 HSHS - 65.6-148.9 - -

17 FO 262-407 - - -

18 BITUMEN 485 205 - -

19 RAW COKE - 315.6 - -

20 PHENOL EXTRACT 715 80 - -

21 SLACK WAX 245 198.9 - -

22 MINERAL TURPENTINE OIL

253.3 32.2 - -

23 LPG 405-450 GAS 1.8 9.6

AUTO IGNITION, FLASH POINT AND EXPLOSIVE LIMITS OF SOME OF THE PETROLEUM PRODUCTS

MAJOR REFINERY POTENTIAL HAZARDS

FIRE HAZARD

EXPLOSION HAZARD

ELECTRICAL HAZARD

TOXIC GAS RELEASE HAZARD

HAZARDOUS CHEMICAL HAZARD

OIL SPILLAGE

RADIATION HAZARD

FALL FROM HEIGHT

SOURCE OF IGNITION

IT IS INITIAL RELEASE OF ENERGY TO TRIGGER COMBUSTION (FIRE). IT IS NECESSARY TO UNDERSTAND THE SOURCES OF IGNITION AND TO ELIMINATE THEM TO PREVENT FIRES/EXPLOSIONS IN OUR REFINERY.SOURCES OF

IGNITION EXAMPLE PREVENTIVE MEASURES

ELECTRICAL EQUIPMENT

SPARKS FROM MOTORS, SWITCHES, LAMPS, HOT ELEMENTS AND ELECTRICAL DEFECTS

1. USE OF APPROVED EQUIPMENT

2. FOLLOW NATION ELECTRICAL CODES

3. PROPER MAINT.

FRICTION HOT BEARINGS, MIS-ALLIGNED OR BROKEN M/C PARTS, CHOCKING, JAMMING OF MATERIAL, POOR ADJUSTMENT

PREVENTIVE MAINT. AND PROPER LUBRICATION

OPEN FLAMES CUTTING AND WELDING TORCHES GAS & OIL BURNERS

STRICT COMPLIANCE OF PRECAUTIONS STIPULATED IN THE FIRE PERMIT FOR HOT JOBS.

SOURCES OF IGNITION

EXAMPLE PREVENTIVE MEASURES

SMOKING AS IGNITION

SMOKING BOOTHS IN AREA WHERE COMBUSTIBLE ARE USED

1. SMOKING ONLY IN AREAS PERMITTED.

2. USE OF PRESCRIBED RECEPTACLES FOR CIGARETTE BUTTS

SPONTANEOUS IGNITION

PYROPHORIC IRON, HOT OIL LEAKAGE

1. KEEP PYROPHORIC IRON WET ARE THE TIME WHEN IT IS TAKEN OUT.

HOT SURFACES CONTACT OF COMBUSTIBLE MATERIAL WITHOUT SURFACES, HEATED LINES

1. PROVIDE PROPER INSULATION AND AIR CIRCULATION.

SPARK FROM ENGHINE EXHAUST

POL TRUCKS / DG SET 1. SPARK ARRESTOR ON EXHAUST

SOURCE OF IGNITION

SOURCES OF IGNITION

EXAMPLE PREVENTIVE MEASURES

STATIC ELECTRICITY

DURING SPLASH LOADING AND LOADING AT HIGH VELOCITIES

1. PROPER EARTHING OF EQUIPMENT.

2. DO NOT RESORT TO SPLASH LOADING

3. LOADING VELOCITY SHOULD BE CONTROLLED

LIGHTENING THUNDERSTORM CLOUD BURST

1. PROPER LIGHTING ARRESTOR AND EARTH CONTINUITY.

SOURCE OF IGNITION

FIRE RISK MANAGEMENT

Fire risk is ‘The chance/possibility of loss due to fire’.

Three aspects to deal with fire risk management are:

Fire Prevention

Fire Protection – Active & Passive

Fire Fighting

FIRE PROTECTION IN GENERAL

FIRE PREVENTION :

IT MEANS ADOPTION OF SAFE INHERENT DESIGN AND PROVISIONS AT THE DESIGN STAGE INITIALLY AND SUBSEQUENTLY DEVELOPING SAFE PROCEDURE TO FOLLOW IN THE DAY TO DAY OPERATION. IT IS THE CONCERN OF EVERYBODY WORKING IN THE REFINERY.

FIRE PROTECTION :

IT INVOLVES OF DIFFERENT FACILITIES WHICH SHALL HELP IN IMMEDIATE HANDLING OF FIRE EFFECTIVELY.

FIRE FIGHTING :

IT IS THE PHYSICAL PHENOMENON OF HANDLING THE FIRE WITH THE USE OF FIRE PROTECTION EQUIPMENTS, FACILITIES AS WELL AS WITH THE HELP OF FIRE FIGHTING PERSONNEL WHO HAVE BEEN SPECIFICALLY TRAINED FOR THIS JOB.

Fire Prevention

Objective : to eliminate the occurrence of fire

1. Fire or naked light, matches, petrol or other lighters, cellular phone or any apparatus which is capable of causing ignition is not permitted to be taken within the battery area by any person.

2. No fires shall be lit and no matches ignited in any part of the battery area unless a valid hot work permit has been obtained from the authorized fire permit signatories of the area and registered at the fire station.

3. Smoking is prohibited in all parts of the battery area except in the smoking booths/locations duly approved for this purpose.

4. Cycle lamps, other than dynamo operated , are not allowed in the refinery battery limits. The cyclist will switch off even the dynamo as soon as he enters the plant area.

FIRE RISK MANAGEMENT

5. Ordinary torches will not be used within the battery area. Flame proof torches/lamps of approved manufacturers as supplied by the refinery, shall only be used.

6. All vehicles entering / transporting petroleum products from the refinery must be fitted only with approved type of spark arrestors.

Fire protection (Passive & Active)

Following fire protection facilities shall be provided depending on the nature of the installation and risk involved:

• Fire water system

• Foam system

• Clean agent system

• CO2 system

• DCP extinguishing system

• Detection and alarm system

• Communication system

Passive fire protection system (at the time of construction & installation)

Dyke walls

Safety valves on equipment

Water seal in separators

Rupture disc in process piping

Fire proofing of structures

Fire retardants paints on cables

Fire barriers

Positive pressurization

Flaring / venting

Fire fighting

Objective : to extinguish the fire with minimum loss

It is the last line of the defense. It comes into force when there is actual fire. Main purpose is to extinguish the fire with suitable equipment and materials with an aim to reduce damage due to fire

• Portable fire fighting equipment

• Mobile fire fighting equipment

• Fixed fire fighting systemActive Fire Protection

Fire fighting

Portable fire fighting equipment (First Aid Fire Fighting Equipment)

• DCP Extinguishers.

• CO2 extinguishers.

• Water Extinguishers

• Portable Foam Extinguishers.

• Clean Agent Fire Extinguishers

Fire fighting

Mobile fire fighting equipment

• Foam tenders

• DCP tenders

• Foam Nurser

• Hydraulic Platform- 54 m height

• Trailer fire pump

• Trolley mounted monitors

• Fire fighting hose & other accessories like foam branch, nozzles etc.

• Fire fighting chemicals like foam compound, dry chemical powder etc.

Fire fighting

Fixed fire fighting equipment

• Fire Hydrants

• Fire Monitors.

• High Volume Long Range Monitors.

• Riser

• Sprinkler Systems

• Foam Pourer Systems

DCP Extinguishers

Operating Mechanism Of DCP

Class “A”, “B”, or “C” fires.

2-10 Kg. dry chemical (ammonium phosphate) pressurized to 3.5 – 14 kg/ sq. cm by CO2 gas (8-25 seconds discharge time).

Has pressure gauge to allow visual capacity check.

1.5 – 6 m. maximum effective range.

Extinguishes by smothering burning materials.

Dry Chemical Powder

B Liquids Grease

A Trash Wood Paper

C Gases

Class “B” or “C” fires. 2 / 4.5 / 6.8 / 9 / 22.5 kg CO2 gas at

51 Kg/cm2. Has NO pressure gauge. Capacity

verified by weight. 3-8 ft. maximum effective range. Extinguishes by smothering burning

materials. Effectiveness decreases as

temperature of burning material increases.

Carbon Dioxide (CO2)

B Liquids Grease

A Trash Wood Paper

C Gases

Suitable for Electrical Fire

(1)Squeeze the nozzle

(2) Remove Safety Clip

(3) Strike on top of the cap(4) Direct the

discharge nozzle at the base of Fire in sweeping action

Method of Operation of DCP Fire Extinguishers (10 Kg)

Method of Operation of DCP Fire Extinguishers (10 Kg)

(1)Hold the horn towards Fire

(2) Remove Safety Pin

(3)Rotate knob in anti clock wise.

Caution: On initial discharge of CO2 it may give electric shock momentarily .

Don’t get panic. Open the operating knob intermittently.

Method of Operation of CO2 Fire ExtinguisherMethod of Operation of CO2 Fire Extinguisher

Precaution at the time of Fire Fighting

• Extinguishing agent eliminates one of the vital elements of the fire

• Many types of extinguishers available• Know location of extinguishers • Alarm has been sounded• Building has been evacuated• Fire is small and confined• You can fight the fire with your back toward an escape route• The extinguisher matches the fire type• The extinguisher works effectively• You are properly trained in the use of the extinguisher• You are confident you can put the fire out

Personal hazards

• Smoke and noxious fumes

• Smoke and fumes cause unconsciousness

• Burn