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Fire Streams. Module II & III. Fire Hydraulics . Deal with properties of energy, pressure, and water flow as related to fire suppression. . Flow . Volume of water that is being moved Measured in gallons per minute (gpm) Metric measured in liters per minute (lpm) . Pressure .

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fire streams

Fire Streams

Module II & III

fire hydraulics
Fire Hydraulics
  • Deal with properties of energy, pressure, and water flow as related to fire suppression.
slide3
Flow
  • Volume of water that is being moved
  • Measured in gallons per minute (gpm)
  • Metric measured in liters per minute (lpm)
pressure
Pressure
  • Amount of energy in a body or stream of water
  • Measured in pounds per square inch (psi)
  • Metric measured in kilopascals (kPa)
  • Required to push water through a hose or to a higher level
  • Pumps usually provide the pressure.
friction loss
Friction Loss
  • Loss of pressure as water moves through a pipe or hose
  • Loss represents the energy required to push the water.
    • Greater flow in same hose, greater friction loss
    • Smaller hose with same flow, greater friction loss
    • All else equal, loss proportional to distance
elevation pressure
Elevation Pressure
  • Elevation affects water pressure.
  • Elevated water tanks supply pressure to pipes due to elevation.
  • Difference between nozzle elevation and engine elevation affects pressure.
    • Hoses laid downhill have greater pressure.
    • Hoses laid up stairs will have less pressure.
water hammer
Water Hammer
  • Surge in pressure caused by sudden stop in the flow of water
  • Shock wave is transmitted back through the hose.
  • Can damage hose, couplings, and plumbing
  • To prevent, open and close valves slowly.
slide11
Foam
  • Used to fight several types of fires
  • Used to prevent ignition of materials
  • Used to neutralize hazardous materials
  • Produced by mixing foam concentrate with water and air
foam classifications 1 of 2
Foam Classifications (1 of 2)
  • Class A foam
    • Used to fight fires involving ordinary combustible materials
    • Increases effectiveness of water by reducing the surface tension of water
    • Can be added to water streams and applied with several types of nozzles
foam classifications 2 of 2
Foam Classifications (2 of 2)
  • Class B foam
    • Used for class B fires
    • Specific foam varies by type of flammable liquid
    • Separates fuel from the fire
    • Foam blanket must not be disturbed
    • Can be applied to flammable liquid spills to prevent fire
class a foam concentrates
Class A Foam Concentrates
  • From 0.1% to 1% solution
  • “Wet” foam has good penetration properties.
  • “Stiff” foam is more effective when applied for protecting buildings.
class b foam concentrates 1 of 3
Class B Foam Concentrates (1 of 3)
  • Used as either 3% or 6% solution
  • Types of foams should not be mixed.
  • Brands of the same foams should not be mixed.
  • Incompatible mixtures may congeal and plug foam systems.
  • Older foams have environmental hazards.
class b foam concentrates 2 of 3
Class B Foam Concentrates (2 of 3)
  • Protein foams
    • Made from animal byproducts
    • Effective on hydrocarbon fires
  • Fluoroprotein foams
    • Made with same base materials as protein foam
    • Includes a flurochemical surfactant
    • Produce fast-spreading membrane
    • Provide a greater seal against edges of objects
class b foam concentrates 3 of 3
Class B Foam Concentrates (3 of 3)
  • Aqueous film-forming foam (AFFF)
    • Synthetic base
    • Particularly suited for gasoline
    • Seals across surface quickly
    • Excellent vapor suppression ability
  • Alcohol-resistant foam
    • Properties similar to AFFF
    • Won’t dissolve in alcohols and other polar solvents
ways fire fighting foam extinguishes prevents fire
Ways Fire Fighting Foam Extinguishes/Prevents Fire
  • Separating
  • Cooling
  • Smothering
  • Penetrating
terms associated with foam
Terms Associated With Foam
  • Foam concentrate
  • Foam proportioner
  • Foam solution
  • Foam (finished foam)
how foam is generated
How Foam is Generated
  • Foams used today are of mechanical type and before use must be
    • Proportioned
    • Aerated

(Continued)

how foam is generated1
How Foam is Generated
  • Elements needed to produce fire fighting foam

(Continued)

how foam is generated2
How Foam is Generated
  • All elements must be present and blended in correct ratios
  • Aeration produces foam bubbles to form effective foam blanket
foam expansion
Foam Expansion
  • The increase in volume of foam when aerated
  • Method of aerating results in varying degrees of expansion
  • Types of foam
foam concentrates general considerations
Foam Concentrates — General Considerations
  • Foam concentrates must match fuel to which applied
  • Class A foams not designed to extinguish Class B fires
  • Class B foams designed solely for hydrocarbon fires will not extinguish polar solvent fires
class a foam
Class A Foam
  • Increasingly used in both wildland and structural fire fighting

(Continued)

class a foam1
Class A Foam
  • Special formulation of hydrocarbon surfactants
  • Aerated Class A foam coats, insulates fuels, preventing pyrolysis and ignition
  • May be used with variety of nozzles
class b foam
Class B Foam
  • Used to prevent ignition of or extinguish fires involving flammable and combustible liquids

Courtesy of Williams Fire & Hazard Control, Inc.

(Continued)

class b foam1
Class B Foam
  • Used to suppress vapors from unignited spills of these liquids
  • Several types of Class B foam concentrates available

(Continued)

class b foam2
Class B Foam
  • Manufactured from synthetic or protein base
  • May be proportioned into the fire stream through fixed system, apparatus-mounted system, or by portable foam proportioning equipment

(Continued)

class b foam3
Class B Foam
  • Foams such as AFFF and FFFP foam may be applied with standard fog nozzles or air-aspirating foam nozzles

Courtesy of Harvey Eisner.

(Continued)

class b foam4
Class B Foam
  • Rate of application depends on several factors
  • Unignited spills do not require same application rates as ignited spills
  • To be most effective, blanket of foam 4 inches (100 mm) thick should be applied to fuel surface
specific application foams
Specific Application Foams
  • Numerous types of foam available for specific applications
  • Properties of foams vary
proportioning
Proportioning
  • Mixing of water with foam concentrate to form foam solution
  • Most concentrates can be mixed with fresh/salt water

(Continued)

proportioning1
Proportioning
  • For maximum effectiveness, foam concentrates must be proportioned at designated percentage
  • Most fire fighting foams intended to be mixed with 94 to 99.9 percent water

(Continued)

proportioning methods
Proportioning Methods
  • Induction
  • Injection

(Continued)

proportioning methods1
Proportioning Methods
  • Batch-mixing
  • Premixing

Courtesy of Ansul.

foam proportioners general considerations
Foam Proportioners — General Considerations
  • May be portable or apparatus-mounted
  • Operate by one of two basic principles

Courtesy of Conoco/Phillips.

portable foam proportioners
Portable Foam Proportioners
  • Simplest, most common form of proportioning devices
  • In-line foam eductors
  • Foam nozzle eductors
apparatus mounted proportioners
Apparatus-Mounted Proportioners
  • Mounted on structural, industrial, wildland, and aircraft rescue and fire fighting apparatus, as well as on fire boats
  • Three types
compressed air foam systems cafs
Compressed-Air Foam Systems (CAFS)
  • Newer structural engines are equipped with CAFS

(Continued)

compressed air foam systems cafs1
Compressed-Air Foam Systems (CAFS)
  • Standard centrifugal pump supplies water, direct-injection foam-proportioning system mixes foam solution with water on discharge side of pump, onboard air compressor adds air to mix before discharging from engine

(Continued)

compressed air foam systems cafs2
Compressed-Air Foam Systems (CAFS)
  • Unlike other systems, hoseline contains finished foam
  • Advantages
  • Disadvantages
handline nozzles
Handline Nozzles
  • Solid-bore nozzles
  • Fog nozzles
  • Air-aspirating foam nozzles
medium and high expansion foam generating devices
Medium- and High-Expansion Foam Generating Devices
  • Produce foam that is semistable with high air content
  • Medium-expansion foam
  • High-expansion foam
  • Water-aspirating type nozzle
  • Mechanical blower generator
reasons for poor quality foam failure to generate foam
Reasons for Poor-Quality Foam/Failure to Generate Foam
  • Eductor, nozzle flow ratings do not match so foam concentrate cannot induct into fire stream
  • Air leaks at fittings cause loss of suction

(Continued)

reasons for poor quality foam failure to generate foam1
Reasons for Poor-Quality Foam/Failure to Generate Foam
  • Improper cleaning of proportioning equipment causes clogged foam passages
  • Nozzle not fully open, restricting water flow

(Continued)

reasons for poor quality foam failure to generate foam2
Reasons for Poor-Quality Foam/Failure to Generate Foam
  • Hose lay on discharge side of eductor is too long
  • Hose is kinked and stops flow
  • Nozzle is too far above eductor

(Continued)

reasons for poor quality foam failure to generate foam3
Reasons for Poor-Quality Foam/Failure to Generate Foam
  • Mixing different types of foam concentrate in same tank results in mixture too viscous to pass through eductor
roll on foam application method
Roll-On Foam Application Method
  • Directs foam stream on ground near front edge of burning liquid spill
  • Foam rolls across surface of fuel

(Continued)

roll on foam application method1
Roll-On Foam Application Method
  • Firefighters continue to apply foam until spreads across entire surface of fuel and fire extinguished
  • Used only on pool of liquid fuel on open ground
bank down foam application method
Bank-Down Foam Application Method
  • May be employed when elevated object is near/within area of burning pool of liquid or unignited liquid spill
  • Object may be wall, tank shell, similar vertical structure

(Continued)

bank down foam application method1
Bank-Down Foam Application Method
  • Foam stream directed onto object, allowing foam to run down onto surface of fuel
  • Used primarily in dike fires, fires involving spills around damaged/overturned transport vehicles
rain down foam application method
Rain-Down Foam Application Method
  • Used when other two methods not feasible because of size of spill area or lack of object from which to bank foam

(Continued)

rain down foam application method1
Rain-Down Foam Application Method
  • Primary manual application technique on aboveground storage tank fires
  • Directs stream into air above fire/spill, allows foam to float gently down onto surface of fuel
foam hazards to humans
Foam Hazards to Humans
  • Foam concentrates pose minimal health risks to humans
  • May be mildly irritating to skin, eyes

(Continued)

foam hazards to humans1
Foam Hazards to Humans
  • Affected areas should be flushed with water
  • Some concentrates, vapors may be harmful if ingested/inhaled
  • Consult MSDS for specific information
foam hazards to equipment
Foam Hazards to Equipment
  • Most Class A, Class B foam concentrates are mildly corrosive
  • Follow proper flushing procedures to prevent damage
foam hazards to environment
Foam Hazards to Environment
  • Primary impact is effect of finished foam after application to fire/liquid spill
  • Biodegradability of foam determined by rate at which environmental bacteria cause decomposition

(Continued)

foam hazards to environment1
Foam Hazards to Environment
  • Environmental impact of foam concentrates varies
  • In the U.S., Class A foams should be approved by USDA Forest Service

(Continued)

foam hazards to environment2
Foam Hazards to Environment
  • Chemical properties of Class B foams and environmental impact vary on type and manufacturer
  • Protein-based foams safer for environment

(Continued)

summary
Summary
  • Firefighters must know the differences between the classes of foam, how to generate foam, and how to apply foam most effectively
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