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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

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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.


Fire streams

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.


Fire streams

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)


Proportioning2

Proportioning


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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