Element 2 - Principles Of Fire And Explosion

Question 1

What are the components of a fire triangle

Answer 1

Fuel
Oxygen
Heat

Question 2

Endothermic reaction

Answer 2

Absorbs heat from the surroundings. Requires energy for the reaction to take place.

Question 3

Exothermic reaction

Answer 3

Releases energy in the form of heat light or sound.
Causes increase in temperature.
Can occur spontaneously.
May produce heat quickly and can cause explosions.
Combustion is an exothermic reaction

Question 4

Stages of combustion

Answer 4

• Induction - vapours mix with air.
• Ignition
• Fire growth - direct, convection, conduction, radiation.
• Steady state
• Decay - fuel or oxygen consumed.

Question 5

Flashpoint

Answer 5

The lowest temperature at which a liquid gives off sufficient vapour to form of flammable vapour/ air mixture.

Question 6

Fire point

Answer 6

The temperature at which a fuel will continue to burn after ignition for at least 5 seconds

Question 7

Ignition point

Answer 7

The temperature to which a material has to be heated for sustained combustion to be initiated by pilot source

Question 8

Auto ignition temperature

Answer 8

The lowest temperature at which a substance will ignite without any additional ignition source

Question 9

Vapour density

Answer 9

The mass of vapour per unit of volume.

Question 10

Relative vapour density

Answer 10

The density of the Vapour relative to the density of some standard material, usually air.

Question 11

Vapour pressure

Answer 11

The Pressure exerted by vapour when the liquid and vapour are equilibrium. example: such as in a closed vessel

Question 12

Minimum ignition energy

Answer 12

The minimum energy that will ignite a flammable fuel/ air mixture.

Question 13

Safe storage of LPG cylinders

Answer 13

In a well-ventilated place in open air.
Away from occupied buildings, boundaries and sources of ignition and heat
Properly secured and uprights.

Question 14

Safe storage of LPG in bulk pressurized tanks

Answer 14

• Sufficient distance between them and buildings or sources of ignition
• Sufficient ventilation
• Tanker access from a dedicated flat parking area
• Security to protect from unauthorised access.
• Impact protection for motorway traffic.
• Emergency arrangements for leakage or fire.

Question 15

Classification of fires

Answer 15

Class A: solids
Class B: liquids 
Class C: flammable gases 
Class D: metals 
Class f: high temperature cooking oils and fats

Question 16

Causes of Fire growth and spread

Answer 16

• Fuel characteristics - Ease of ignition, Heat of combustion, Fluidity of liquid.
• Fuel seperation
• Containment - open or in building.
• Room dimensions

Question 17

Structural Factors that influence fire growth rates and smoke movement

Answer 17

Building Design - gaps in doors, ceilings walls
Insulated core panels - Fire rated insulation.
Internal linings.
Construction materials - brick, steel, timber.
Ventilation levels - natural or forced.
Contents of the premises - furnishings

Question 18

Methods of heat transfer

Answer 18

Conduction.
Convection
Radiation
Direct burning

Question 19

Categories of explosion

Answer 19

Detonation - supersonic

Deflagration - subsonic

Question 20

Gas and vapour explosions

Answer 20

Confined vapour cloud explosion.
Unconfined vapour cloud explosion.
Boiling liquid expanding vapour explosion.

Question 21

Classifications under EU CLP regulations (No. 1272/ 2008)

Answer 21

• Flammable liquid - flashpoint 23°C - 60°C.
• Highly flammable - flash Point below 23°C and boiling point above 35°C.
• Extremely flammable - flash point below 23°C boiling point less than 35°C.

Question 22

Flammable (explosive) limits

Answer 22

Lower flammable (explosive) limit - minimum concentration of fuel in air.
Upper flammable (explosive) limit - maximum concentration of fuelled air.

Question 23

Methods of preventing or controlling the ignition

Answer 23

Equipment designed for use inflammable atmospheres.
Plant designed to maintain vapours below LFL.
Proper storage of flammable and combustibles.
Good Housekeeping.
Information instruction and training.
Safe systems of work.
Inerting.

Question 24

Lining material properties that might increase fire spread.

Answer 24

Ignitability.
Right surface flame spread and Heat release.
Amount of smoke produced when ignited.
Tendency to produce flaming droplets.

Question 25

Properties that lining material should have to limit spread of Fire

Answer 25

Resistance to ignition.
Resistance to spread of Fire.
Low smoke production.
Slow rate of Fire growth
Examples: exposed brick/ blockwork, mineral fibreboard, plasterboard and skim, concrete and stone.

Question 26

Conditions required for a gas explosion to occur

Answer 26

• Presence of a combustible gas becoming airborne mixing with air.
• Concentration of gas lies between the flammable limits.
• Atmosphere contains sufficient oxygen to support combustion.
• Ignition source with sufficient heat energy.

Question 27

Preventing explosions

Answer 27

Good Housekeeping.
Ventilation.
Safe storage and handling of explosive material.
Control of detonation sources.
Cooling.

Question 28

Rules for safe storage and handling of explosive material.

Answer 28

Identification of explosive and potentially explosive chemicals.
Correct labelling.
Keep explosives away from ignition sources.
Designated area for explosive chemical use.
Periodic checking of chemicals that could be come over pressurised.
Ensuring workers are thoroughly trained.

Question 29

Venting systems to prevent explosion

Answer 29

Pressure relief valves.
Bursting discs.
Venting panels.

Question 30

Preventing Dust explosion

Answer 30

Sealing joints to prevent escape of dust.
Exhaust ventilation on dust filters.
Regular maintenance plant equipment.
High standard of housekeeping.
Insulating hot surfaces. 
Using intrinsically equipment.
Bonding to Earth.