Chapter 15, Foam Equipment And Systems

Question 1

What are the 3 main reasons why the use of foam has increased dramatically?

Answer 1

• frequency of hazmat incidents
• new advances in foam concentrate technology
• improvements in foam proportioning equipment

Question 2

The majority of foams used today are the mechanical type. What 2 steps need to take place to mechanical foams before they can be used as fire fighting foam?

Answer 2

• proportioned (mixed with water)

- aerated (mixed with air)

Question 3

To produce quality foam, what 4 things are needed?

Answer 3

• foam concentrate
• air
• water
• mechanical aeration

Question 4

What is foam concentrate?

Answer 4

Raw liquid foam (before combined with water and air).

Question 5

What is a foam proportioner?

Answer 5

The device that introduces foam concentrate into a water stream to create foam solution.

Question 6

What is foam solution?

Answer 6

The mixture of foam concentrate into water before introduction of air.

Question 7

What is foam?

Answer 7

The completed product after air is introduced to foam solution (finished foam).

Question 8

What are the 2 categories of Class B foam?

Answer 8

• hydrocarbons (gas, crude oil, jet fuel)

- polar solvents (alcohol, lacquer thinner)

Question 9

Class B foam is effective as an extinguishing agent and vapor suppressant because it can do what?

Answer 9

Float on the surface of hydrocarbon fuels.

Question 10

By what method does foam extinguish/prevent fire?

Answer 10

• separating (create barrier between fuel and fire)
• cooling (lowers temp of fuel and adjacent surfaces)
• suppressing (prevents release of vapors; smothers)

Question 11

What is the difference in proportioning Class B foams, compared to Class A foams?

Answer 11

Class B foams MUST be proportioned in the specific percentage they are designed for; Class A foams can be adjusted to higher or lower percentages.

Question 12

What happens when you vary the proportioning percentages of class A foam?

Answer 12

• to produce a dry (thick) foam, adjust concentrate to a higher percentage
• to produce a wet (thin) foam, adjust concentrate to a lower percentage

Question 13

What are the 4 basic methods in which foam may be proportioned?

Answer 13

• induction (water passes through educator, pulls concentrate into water stream
• injection (external pump forces foam concentrate into water stream at the correct ratio)
• batch mixing (appropriate amount of concentrate is poured directly into tank)
• premixing (premeasured water and foam concentrate mixed into a container; portable extinguisher)

Question 14

What are the 4 common methods of storing foam concentrate for municipal/wild land fire?

Answer 14

• pails (5 gallon plastic, airtight)
• barrels (plastic, airtight)
• totes (for bulk purchasing, reduces cost)
• apparatus tanks (piped directly to foam delivery system)

Question 15

Mechanical foam is technically divided into what 2 categories?

Answer 15

• Class A (ordinary combustibles)

- Class B (flammable/combustible liquids)

Question 16

When performing fire attack and overhaul with standard fog nozzles, what percentage of Class A foam concentrate do you use?

Answer 16

.2% to .5%

Question 17

When providing exposure protection with standard fog nozzles, what percentage of Class A foam concentrate do you use?

Answer 17

.5% to 1.0%

Question 18

When using any application of Class A foam with air aspirating nozzles, what percentage of Class A foam concentrate do you use?

Answer 18

.3% to .7%

Question 19

What percentage of Class A foam concentrate is used for any application with compressed air foam system (CAFS)?

Answer 19

.2% to .5%

Question 20

When using Class A foam, areas requiring maximum penetration need what consistency of foam?

Answer 20

Wet foam (high water content, very fast drainage).

Question 21

When using Class A foam for vertical surfaces, what foam consistency is needed?

Answer 21

Dry foam (slow drainage rate makes it cling, resembles shaving cream).

Question 22

When using Class A foam in areas requiring a balance of penetration and clinging ability, what foam consistency is needed?

Answer 22

Medium foam (blankets and wets foam equally well).

Question 23

Class B foam concentrates are manufactured out of what type of materials?

Answer 23

Either a protein base or synthetic base.

Question 24

What percentages are Class B foams proportioned in?

Answer 24

1% to 6% (normally 1 to 3 for hydrocarbons, and 3 to 6 for polar solvents).

Question 25

What is foam expansion?

Answer 25

The increase in the volume of foam solution when it is aerated.

Question 26

What factors play a role in the varying degrees of Class B foam expansion?

Answer 26

- type of foam concentrate used - accurate proportioning of concentrate in the solution - quality of foam concentrate - method of aspiration

Question 27

What variables determine the rate of application of fire fighting foam?

Answer 27

- type of concentrate used - whether or not the fuel is on fire - type of fuel (hydro or polar) - whether fuel is spilled or in a tank

Question 28

What is the most commonly used foam today?

Answer 28

AFFF (completely synthetic).

Question 29

What 3 things occur when AFFF is applied to a hydrocarbon fire?

Answer 29

- vapor-excluding film is released ahead of foam blanket - fast moving foam blanket moves across surface and around objects (more insulation) - as foam blanket continues to drain water, more film is released

Question 30

What are concentrations for alcohol-type AFFF when used on polar solvents?

Answer 30

3% to 6% (create a membrane over fuel instead of a film).

Question 31

How should alcohol type AFFF be applied to the fuel?

Answer 31

Gently, so that membrane can form first (sprayed over top of fuel, not plunged into the fuel).

Question 32

What are high-expansion foams?

Answer 32

Special purpose foams with a detergent base (low water content minimizes water damage).

Question 33

What are the three applications of high-expansion foams?

Answer 33

- in concealed spaces, such as basements - in fixed-extinguishing systems for industrial use (bulk paper storage) - class A fire applications

Question 34

Foam proportioning devices operate under what 2 principles?

Answer 34

- pressure of water streaming through a restricted orifice creates venture action (pulls foam into the stream) - pressurized proportioning devices inject foam concentrate into water stream (at a chosen ratio)

Question 35

How does low-energy foam system operate?

Answer 35

Introduces air into the solution when it reaches, or is discharged from, the nozzle.

Question 36

How does high-energy foam system operate?

Answer 36

Introduces compressed air into the solution before its discharged from the hose line.

Question 37

What are the 3 common types of portable foam proportioners?

Answer 37

- in-line eductors - foam nozzle eductors - self-educting master stream nozzles

Question 38

How does in-line eductor work?

Answer 38

Either directly attaches to pump panel discharge or connected at some point in the hose lay (uses venture to pull foam concentrate into water stream).

Question 39

On the in-line eductor, back pressure must not exceed how much of the eductor inlet pressure?

Answer 39

67 to 70 percent.

Question 40

In order for the eductor and the nozzle to operate correctly, both must have the same gpm rating. Which controls the flow, the eductor or the nozzle?

Answer 40

The eductor controls the flow.

Question 41

How does foam nozzle eductor work?

Answer 41

It is built into the nozzle, instead of the hose line (foam concentrate has to be where the nozzle is operated).

Question 42

How does self-educting master stream nozzle work?

Answer 42

Used where flows in excess of 350 gpm are needed.

Question 43

How does the installed in-line educator system operate?

Answer 43

These are permanently attached to the apparatus pumping system (operates same as portable in-line educator).

Question 44

How does the bypass-type balanced pressure proportioner operate?

Answer 44

Usually found on large scale mobile trucks (airport trucks). Can flow foam and water at the same time.

Question 45

How does variable-flow variable-rate direct injection operate?

Answer 45

Operates off power supplied from trucks electrical system.

Question 46

What is the unique difference with the variable-flow demand-type balanced pressure proportioner?

Answer 46

It is maintained in a ready-to-pump state, requires no flushing after use, water and foam discharged at same time.

Question 47

How does batch-mixing work?

Answer 47

Pour appropriate amount of concentrate into tank (simplest form).

Question 48

What are some advantages of using CAFS?

Answer 48

- much longer reach than low-energy foam - sticks to fuel surface longer, resists heat longer - allows application from a greater distance - hose lines weigh less

Question 49

What type of pump is used foe CAFS system?

Answer 49

A standard centrifugal pump.

Question 50

With LOW ENERGY foam systems, how is aeration and foam discharge accomplished?

Answer 50

By the foam nozzle.

Question 51

How does IFSTA define a hand line nozzle?

Answer 51

Any nozzle that 1 to 3 fire fighters can safely handle and that flows under 350 gpm.

Question 52

What foam applications can smoothbore nozzles be used on?

Answer 52

- class A | - CAFS

Question 53

What types of foam provides the best application when used with fog nozzle?

Answer 53

- AFFF | - Class A

Question 54

How does an air-aspirating foam nozzle operate?

Answer 54

It inducts air into the foam solution by a venture action.

Question 55

What are the 2 basic types of medium and high-expansion foam generators?

Answer 55

- water-aspirating type: large nozzle with screen at the end to further break up foam and mix it with air - mechanical blower: air forced through foam spray by a powered fan (total flooding app, huge discharge)

Question 56

What are the 4 types of foam application methods?

Answer 56

- direct application (Class A foam) - roll-on (direct on ground near front edge of burning spill: Class B foam) - bank-down (spray on wall, flows down wall onto surface of spill; Class B) - rain-down (use on above ground storage tanks; Class B)

Question 57

What is the primary environmental concern of finished foams?

Answer 57

Its impact after it applied to a spill (Class A foams are lethal to fish).

Question 58

What are durable agents?

Answer 58

Water additives used to aid in extinguishment (water wetter), as well as a pretreat for structures threatened by fires.