Chapter 28 Class B Fires

Question 1

What is a flammable liquid?

Answer 1

The US DOT and TDG define a flammable liquid as one that has a flashpoint below 60.5 °C whereas NFPA and WHMIS define it as one that has a flashpoint below 37.8 °C.

60.5°C is a value that is used globally and recognized by the UN.

Question 2

Fires in open-topped oil tanks 3 Specific conditions

Answer 2

Boilover
Slopover
Frothover

Question 3

may occur spontaneously during fires in open-top tanks containing most types of crude oils and some synthetic heavy oil mixtures. This may occur when an explosion, usually caused by lightning, blows off the roof of a tank.

Answer 3

Boilover

Question 4

can result when a water stream is applied to the surface of a burning oil, provided the oil is viscous and its temperature exceeds the boiling point of water.

Answer 4

Slopover

Question 5

refers to the overflowing of a container, not on fire, when water boils under the surface of viscous hot oil.

Answer 5

Frothover

Question 6

Safety-Relief Devices

Answer 6

Safety- or Pressure-Relief Valves
Rupture Discs (Bursting Discs)
Fusible Plugs (Fuse Plugs or Melt Plugs)

Question 7

are usually a part of the cylinder held closed by a spring.

Answer 7

Safety- or Pressure-Relief Valves

Question 8

are discs, usually of metal, that burst and release the gas when the pressure of the cylinder reaches a certain level.

Answer 8

Rupture Discs (Bursting Discs)

Question 9

are activated by temperature rather than pressure. They are used in situations where heat could cause an explosive chemical reaction and are designed to release the gas before the hazardous reaction can begin.

Answer 9

Fusible Plugs (Fuse Plugs or Melt Plugs)

Question 10

Cylinders with manual control valves are equipped with either

Answer 10

a hand wheel or stem valve.

Question 11

Gas cylinder colour coding

Answer 11

Green/Silver - Oxygen
Blue - Nitrous Oxide
Orange - Cyclopropane
Brown - Helium
Red - Ethylene
Grey - Carbon Dioxide

Question 12

five common methods for containers to breach and spill their contents

Answer 12

disintegration,
runaway cracking
attachments open up
puncture
split/tear.

Question 13

Container breach usually results in release of the contents. This release may happen slowly or quickly through…

Answer 13

detonation
violent rupture
rapid relief
spill/leak.

Question 14

13 Gases are lighter than air: Acronym – “4H MEDIC ANNA”

Answer 14

Hydrogen
Helium
Hydrogen Cyanide
Hydrogen Fluoride
Methane
Ethylene
Diborane
Illuminating gas
Carbon monoxide
Acetylene
Neon
Nitrogen
Anhydrous ammonia

Question 15

What is the vapor density of dry air

Answer 15

1

Question 16

Container release types

Answer 16

hemispheric
cloud
plume
cone
stream
pool
irregular

Question 17

3 Basic types of pressure vessels

Answer 17

• Cylinders
• Tanks
• Lines

Question 18

Relief valve is venting due to:

Answer 18

● Overfilling
● Temperature difference
● Malfunction

Question 19

BLEVE

Answer 19

(Boiling Liquid Expanding Vapor Explosion)

Question 20

__________ __________ is lighter than air, so it will rise and diffuse rapidly in open areas; in confined spaces, it will rise and collect from the ceiling downward. If you are using a gas detector in a confined area, sample the highest possible point in the room.

Answer 20

Natural Gas

Question 21

Natural gas concentrations of between __________ and __________ are explosive. In its compressed form (CNG), it is subject to a boiling liquid expanding vapor explosion (BLEVE).

Answer 21

5%, 15%

Question 22

Transmission lines carry gas
from processing plants to local distribution centers. Gas in these lines is carried at pressures of…

Answer 22

700 to 9900 kPa (100 to 1440 psi)

Question 23

Class ‘B’ Fire Foam Percentages and Applications:

Answer 23

1.0%: On Shallow Hydrocarbon spills (such as gasoline, crude oil, diesel, aviation kerosene)
3.0%: On severe hydrocarbon (as above) and Polar solvent (alcohols, ketones, ethers) fires– products that mix with water)
Up to 6% for Hazmat vapor suppression (if required)

Question 24

4 Methods FOAM is Proportioned

Answer 24

Induction = In-Line Eductor (Old Pumps)
Injection = External Pump to force Foam into the fire stream.( New Salisbury Pumps)
Batch-Mixing = Pour the Foam directly into the Pump’s Tank
Premixing = Used in Fire Extinguishers

Question 25

2 Types of Foam Application Systems

Answer 25

Manual System = Eductor & Playpipe Automatic System = Built into the new Salisbury Pump

Question 26

Describe methods by which foam prevents or controls a hazard.

Answer 26

● Separation – Foam can be utilized to create a barrier between the fuel and the fire. ● Suppression – A blanket of foam robs a fire of its oxygen source and helps prevent the release of flammable vapors that might ignite. ● Cooling – As it breaks down into water, foam lowers the temperature of the fuel and nearby exposures.

Question 27

Explain principles by which foam is generated.

Answer 27

● Proportioning ● Foam generation ● Distribution.

Question 28

List the characteristics, uses and limitations of firefighting foams.

Answer 28

● The physical structure of foam is unstable – it can be broken down by physical force such as a water hose stream, or by some of the very chemicals you are trying to combat. ● Foam breaks down and vaporizes in the presence of heat and flame, so it must be applied in large quantities to compensate for this loss. ● Foam use in electrical fires is drastically limited because the solution is conductive. ● Foam can only be used on horizontal surface fires or in restricted spaces. ● Weather conditions, such as high winds, rain and extreme cold can greatly reduce the usefulness of foam.

Question 29

List different foam stream application techniques.

Answer 29

● Roll-on Method (Splashing) ● Bank-down Method (Baffle) ● Rain-down Method (Lobbing)

Question 30

List the characteristics of pressurized flammable gases.

Answer 30

● Pressure ● Diffusivity (tendency to spread freely) ● Low boiling points ● Colorless and/or odorless ● Creates static electricity when flowing

Question 31

List specific permanent markings on every gas cylinder.

Answer 31

● designed service pressure ● serial number ● inspection codes ● identification of the cylinder manufacturer ● empty (tare) weight ● date of testing and retesting.

Question 32

Give examples of safe havens before approaching flammable gas cylinder fires

Answer 32

1. Ground cover 2. Low lying areas (ditches, gullies) 3. Buildings 4. Treed areas 5. Fire pumper or truck, and, as a last resort, 6. Fog nozzle stream.

Question 33

What is LPG?

Answer 33

Liquid Petroleum Gas