IFSTA Chapter 14 Foam Equipment Flashcards
How is Firefighting foam produced
Foam Concentrate, water and air must be educted or injected at the correct ratios
Foam Concentrate
Raw foam liquid in its storage container before being combined with water and air
Foam Proportioner
Device that injects the correct amount of foam concentrate into the water stream
Foam Solution
Mixture of foam concentrate and water without air
Foam
Completed product after air is introduced into the foam solution
What are class B fires divided into
Hydrocarbons: Crude Oil, Fuel Oil, Gasoline, Benzene and Kerosene (Specific gravity <1)
Polar Solvents: Alcohol, Acetone, ketones, and esters (miscible)
Class B foams are designed solely for use on ____________ and are not effective on ____________ regardless of concentration
Hydrocarbon fuels not effective on polar solvents
some foams intended for polar solvents may be used on hydrocarbon fuels under manufacturer instructions
What is Proportioning
The act of mixing of fresh/salt water with foam to form a solution
Most firefighting foams are formulated to mix with what percent water
94 to 99.9
Four Basic methods of proportioning foam
Inductions
Injection
Batch Mixing
Premixing
What is Class A foam concentrate composed of
Hydrocarbon surfactants that reduce the surface tension of water allowing penetration
Properly stored foam has a shelf life of?
20 years
Commonly used percentages for different scenarios when proportioning Class A foam
Fire Attack and Overhaul:
Exposure Protection:
Any Application with air aspirating Nozzle:
CAFS:
Fire attack and overhaul .2 to .5% with Fog Nozzle
Exposure Protection .5 to 1% with fog nozzle
Any Application with Air Aspirating Nozzle: .3 to .7%
CAFS: .2 to .5%
What Does application rate refer to
Minimum amount of foam solution that must be applied to a fire per minute per square foot
What is Synthetic Class B foam made out of
Fluorosurfactants
What shelf life does Class B foam have
20 to 25 years
To what percentages are Class B foams proportioned to
One to Six Percent
Hydrocarbon Fuels: 1 to 3%
Polar Solvents: 3 to 6%
What is Foam Expansion
Increase in volume of foam solution once it has been aerated
Per NFPA 11 what do the different foam expansion ratios contain?
Low: 20:1 finished foam to foam solution
Medium: 20:1 to 200:1
High: 200:1 to 1000:1
Formula to calculate the application rate available from a specific nozzle
Nozzle Flow Rate / by the area of the fire
When AFFF is applied to a hydrocarbon fuel what occurs
How does the foam HEAL
Air/Vapor excluding film is released ahead of the foam blanket
Blanket of Foam spreads across surface providing insulation
As water is released from the aerated foam blanket more film is released giving the foam the ability to “HEAL”
How does AR-AFFF foams work
How should it be applied
Applied to polar solvents, a membrane is created over the fuel which separates the water into the foam blanket.
Should be applied gently to a fuel product in order to allow the membrane to form
Different types of foam proportioning eductors
In-Line Eductors
Foam Nozzle Eductors
Self Educting master stream nozzles
When using an In-line Eductor what pressure percent must not be exceeded on the discharge side of the eductor
Discharge pressures must not exceed 70% of the eductor inlet pressure. This creates back pressure
How do you calculate back pressure on an in-line eductor
Nozzle Pressure + FL between eductor and nozzle + elevation pressure
Step to take after a foam operation using an inline eductor
Use a bucket of water to immerse the foam pick up tube and induct water for atleast 1 minute
What height should the foam concentrate inlet to the eductor be from the liquid surface of the concentrate
should not be more than 6 feet between foam inlet and liquid surface of concentrate
What must be the same between the nozzle and the eductor to operate successfully
Attack nozzle and eductor must have the same GPM
How does a bypass proportioning system work
In bypass mode a valve directs water through a second chamber of the eductor that contains no orifice or restrictions
To activate foam being used a valve is directed to divert water through the eductor
In a bypass proportioning system what is included in the system to ensure proper foam concentrates are applied
A metering valve is present at the valve that activates with water running through eductor
How is an around the pump system built
How many gpms of water is allowed to flow to create the foam drawing Venturi effect
A small return water line containing an eductor and a control valve is connected to the discharge side of the pump back to the intake side.
The valve allows between 10 to 40 gpm to flow through the piping creating a Venturi that draws foam from onboard tank
Once mixed it enters the intake side of the pump
(CAFS) system contains what type of air compressor, pump and proportioner
how does it operate
Rotary Air Compressor, a standard centrifugal pump, a direct injection proportioner is attached to the discharge side of the pump
Once concentrate is mixed with water compressed air is added before being discharged from the apparatus to the hose line
Benefits of CAFS generated foam
Reach of the fire stream is longer
Produces small uniform air bubbles (very durable)
Adheres to fuel surfaces
resists heat longer
What airflow from compressor when using CAFS produces dry foam of up to 100 gpm?
2 cubic ft/minute of airflow per gpm
