Chp 14 Flashcards
Foam used more because
Bigger hazmats
New foam is easier to use by structure and wildland
Proportioners are better, easier to put in pumpers
Helps reduce water if water is limited
Mechanical foam
Produced by physical agitation of concentrate, water and air
Most common
Aeration
Put air into foam solution to create bubbles that give finished foam
Foam concentrate
Starting point
Can be protein, synthetic, aqueous film forming, high expansion or alcohol
Foam proportioner
Second step
Injects correct amount of foam concentrate into the water stream
Makes foam solution
Foam
Completed product after air is introduced
Foam solution + air
For use on Class A or B
Protein,
Class B fuels
Hydrocarbons: crude oil, benzene, kerosene, specific gravity <1
Polar Solvents: alcohol, acetone, ketones, esters, miscible and conduct electricity
Modern fuels with 15% solvent additives treat as polar solvents
Class B foam only works on hydrocarbons
Foam works by
Separating: fuel and fire
Cooling: the fuel and adjacent surfaces
Smothering: vapors
Initial blanket excludes oxygen then as it breaks down into water it cools and runs off, taking product with it
Proportioning
Can mix with fresh or salt water
Mix per mfg
Mix from 0.1 - 6%
Class A 0.1 - 1%
Proportioning Methods
Induction: Pressure of water to draft concentrate by passing through a venturi device called an eductor, through a pickup tube
Injection: External pump forces concentrate into firestream at correct amount (fixed systems)
Batch mixing: Dumping concentrate (usually A) into a tank. Inaccurate and shuts down lines when tank is empty. B has to be stirred
Premixing: mixed in the container, portable and wheeled extinguishers, can use with CAFS
Foam storage
Pails: 5 gal, non corrosive, airtight, easy to store
Barrels: 55 gal, usually just for storage, can put on a trailer
Totes: 275 gal, storage for ARFF or wildland, can be on a trailer
Apparatus tanks: 20-200 gal, tender up to 8000 gal and no water
Foam concentrates
Some are A and B but most are one or the other
Class A foam
Hydrocarbon based surfactants or wetting agents that reduce surface tension
Used on structure, wildland, coal, tire storage and others
When used with CAFS (entrains lots of air) makes excellent insulation
20 yr shelf life, buy in bulk
Don’t flow directly into lakes
Corrosive on skin
0.1 - 1.0 %
Class A foam nozzles
Fog
Aerating foam
Medium and high expansion devises
CAFS with most nozzles including solid stream
Produce more stable foam at 1.0% than 0.5%
Class A proportioning
Fire attack and overhaul with fog: 0.2 to 0.5
Exposure protection with fog: 0.5 to 1.0
All with air aspirating foam nozzle: 0.3 to 0.7
All with CAFS: 0.2 to 0.5
Application rate definition
Minimum amount of foam solution applied to unignited fire, spill, or spill fire to control vapor emission or extinguish the fire
Take GPM/square ft to calculate
Determine in pre incident planning
Application of class A
Areas needing max penetration
Vertical surfaces: dry foam clings well
Surface of fuel: cling and penetrate
Foam breakdown affected by
Heat of fire
Size of flames
Ambient temp
Prevailing winds
Class B Foam
Made of synthetic (Fluorosurfactants) or protein (animal) base
Store in cool place, 10 yr life protein, 20-25 for synthetic
Usually cant mix but AFFF and fluoroprotein can be mixed immediately before use, mil spec mixed anytime
Class B proportioning
1 to 6 %
Can depend on fuel hydrocarbon 1 to 3%, polar solvents 3 to 6%
Foam expansion
Low medium or high depends on Type of concentrate Accurate proportioning Qualify of concentrate Method of aeration NFPA 11 finished foam to solution, low: 20:1, medium 20:1 to 200:1, high 200:1 to 1000:1
Rate of class B application
Set by NFPA 11, Depends on: Type of concentrate If the fuel is on fire (requires more) Hydrocarbon or polar solvent If fuel is contained or not Once you start, mus apply continuously from uphill upwind so make sure at the beginning that you have enough, or fire may consume a portion of the blanket Apply uphill upwind
1-Regular protein foams
Protein hydrosolate plus additives to prevent freezing
From hooves, horns and feathers
Good heat stability and burnback resisitance
Not as fluid
Shorter shelf life
More rare
2-Fluoroprotein Foam
Protien foam with synthetic fluorchemical surfactant added
Makes it flow better and has longer lasting vapor suppression
Popular
Add Ammonia salts to work with alcohol for 15 min
3-Film forming fluoroprotein foam
Combines 2-fluroprtein foam’s long heat resistance with 5- AFFF’s for quick knockdown
Can be alcohol resistant
4-Aqueous film forming foam
Most common synthetic
Fluorochemical and hydrocarbon surfactants for high boiling point
Creates thin film over fuel specifically:
Vapor suppression film is released before the blanket
Fast Moving blanked spreads across fuel for insulation
Drains and fill in holes where blanket was disturbed
4.5-Alcohol resistant AFFF
For use on polar solvents
Creates a membrane over the fuel, separates water in the foam from alcohol in the product
3 to 6% concentrate
Also used on hydrocarbons at 1 to 6%
Aspirating nozzles are best to create and preserve membrane
Put on gently to help membrane form first
High expansion foam
Detergent base, low water content Less runoff, less water damage Used in cellars and coal mines Class A Industrial hazards
Two types of proportioners
Venturi
Pressurized injects set ratio into water
In line foam eductor
Low energy proportioner
Mfg for pressure and distance
Gpm must not exceed rated capacity
Pressure at discharge side can’t exceed 70% of inlet pressure (back pressure)
Too high or too low pressure makes lean or rich mixture
Flush for 1 minute
Eductor inlet within 6”
Nozzle and eductor must have same gpm rating
1-Foam nozzle eductor
Low energy proportioner
Nozzle with an eductor
Foam must be at the nozzle
2-Self educting master stream foam nozzle
Low energy proportioner
For flows >350 gpm up to 14000 gpm
Lower pressure drop
Jet ratio controller can locate 3000’ from nozzle and elevation of 50’, proportions at 66.5% then in line eductor from MS drops it to 3%
3-App mounted in line eductor
Same as portable
Foam can come from bucket or onboard tank
Bypass proportioner can reduce FL across eductor when just flowing water
Usually for class B
4-Around the pump proportioner
App mounted, Most common
10-40 gpm of water from the tank flows through an inline proportioner to create venturi to get foam then dumped back to pump inlet
Old ones can only work off tank water
5-Bypass type balanced pressure proportioner
Large mobile app like ARFF
Monitors demand for foam and adjusts concentrate supplied by a separate foam pump for each discharge
Most accurate
6-Variable flow variable rate direct injection system
Positive displacement foam pump injects concentrate into the water flow so supplies all discharges with foam
Monitors hoselines to maintain consistent quality of foam
0.1 to 3%
Class A or B, not alcohol resistant
Atmospheric pressure fed foam tanks
7-Variable flow demand type balanced pressure proportioner
Both fixed and mobile
Variable speed drives foam pump and monitors the flow of foam
Ready to pump, no flushing and can go to any number of discharges
Batch mixing
Only done with Class A
Not good 24 hrs after mixing
Foam can remove lube
Last resort
CAFS
High energy Stream reaches farther Small, uniform, durable bubbles Good adherence good heat resistance More expensive, maint, training 0.1 to 1% 10:1 expansion ratio
Smooth bore nozzles
Only work with CAFS
Good reach
Fog nozzles
Apply low expansion short duration foam blanket
2:1 to 4:1 expansion
Best for AFFF and Class A not fluoroprotein or polar solvents
Air aspirating foam nozzle
Induct air into the foam solution
Good for Class A and only ones for protein and fluoroprotien concentrates
Max expansion, worst reach
Medium and high expansion foam generators
Water aspirating: same as other foam nozzles just bigger with screens
Mechanical Blower: uses a fan instead of water, good for total flooding
Create high air content from 20:1 to 200:1
For high expansion foam 200:1 to 1000:1
Problems with foam fire streams
Not matching eductor and nozzle flow Air leaks, lack of suction Clogged proportioning equipment Attack line too long Too much elevation to nozzle Mixed concentrates
Foam application techniques
Direct application: class A Roll on: Class B Bank down: Class B Rain down: Above ground storage tanks
Durable agents
gelling agents: superabsorbent liquid polymers absorb 100x their weight in water
Slippery
Expensive
Trap water instead of air in the bubbles
Non toxic
Can stick to walls for 24 hrs and be rehydrated with a fine mist
Class A application rate
Same minimum required flow rate for water
