Chapter 18 Foam Fire Fighting, Liquid Fires, and Gas Fires

Methods to Fire Fighting Foad & Equipment/Materials needed

Foam Fire Fighting

• Separating

  • Barrier between fuel gases & ignition sources

• Cooling

  • Lowers temp. of fuel & adjacent surfaces

• Smothering

  • Prevents air reaching fuel & mixing with vapors & prevents release of flammable vapors

• Penetrating

  • Lowers surface tension of water & allows it to penetrate fires in Class A materials

• Class A Fuels - penetrate

• Class B Fuels - Separates, smothers, cools, suppresses

Class A & B Foams

• Class A Foams

  • Intended for ordinary combustibles

  • Solid fuels - foam blanket/cools fuel stops burn process

  • Lowers surface tension, water penetrates deeper

  • Water released as foam collapses, produces cooling effect

• Class B Foams

  • Intended for flammable liquids

  • Foam blanket prevents or reduces flammable vapor release

  • Especially effective on hydrocarbon fuels/polar solvents

Foam Generation - Proportioning

• Water

• Foam concentrate, foam solution, foam proportioner

Foam Generation - Aeration

• Aeration

• Finished foam

Foam Expansion

• Degree of expansion depends on

  • Type of foam concentrate

  • Accurate mixing of foam in solution

  • Quality foam concentrate

  • Method aeration/sizing bubbles

Foam Concentrates - Nozzles Used

• Fog nozzles

• Air-aspirating foam nozzles

• Medium/high expansion devices

• Apparatus mounted systems

Class A Foam

• Made for Class A fuels/wildland & structural fire

• Surfactants reduce surface tension of water in foam, water penetrate in fuel better

• Coats/insulates fuels, preventing pyrolysis/ignition

Class B Foam

• Prevents ignition, extinguishes & suppresses vapors from fires involving flammable/combustible liquids

  • Hydrocarbon fuels/Polar solvents

• Application rate depends on

  • Type of foam

  • If fuel on fire

  • Type of fuel

  • Fuel spilled or in tank

  • Foam is applied by fixed system or portable equipment

• Foma blanket suppresses vapors from unignited spills

• Foam concentrate supplies should be at the point of proportioning before application

  • Once it starts, should continue until extinguished

  • Stopping/restarting may allow fire to consume foam

Foam Hazards

• Mild irritant to skin/eyes

• Harmful if inhaled/ingested

• Degrade PPE

• Most mildly corrosive

• Environmental concerns

Foam Proportioning

• Water + Foam concentrate = Foam solution

• 3% mix (3 gal. foam + 97 gal. water = 100 gal of 3% foam)

• 6% mix (6 gal. foam + 94 gal. water = 100 gal of 6% foam)

• Selection of a proportioner depends on

  • Foam flow requirements

  • Available/correct water pressure

  • Use for foam

  • Foam agent

• Proportioner not compatible with device can result in unsatisfactory foam/no foam

• Eduction method

  • Hose line → Eductor → Water/Foam solution → Discharge

• Injection method

  • Water → fire pump → tube → meets foam tank → foam pump to tube → discharge

• Premixing method

  • 1 time application

  • Tank emptied/refilled before used again

  • Most class A biodegradable

  • Fire/Wheeled extinguisher, skid-mounted twin-agent unit

Foam Proportioners

• Equipment needed to produce foam stream

• Pump

• Fire hose

• Foam proportioner

• Delivery device (nozzle, gen system)

In-Line Foam Eductors

• Follow manufacturers rules for inlet pressure, max hose lay between eductor/discharge

• Pickup tube connected to eductor low point

• Pickup tube draws foam into water stream

Foam Nozzle Eductors

• Eductor built into nozzle rather than hose

• Foam must be available at nozzle

• Relocating foam containers can be problem

• Supplies may left behind if FF’s retreat

Apparatus-Mounted Proportioners

• In-line eductors

• Around-the-pump proportioners

• Balanced-pressure proportion

Compressed Air Foam Systems (CAFS)

• Mounted on many types of apparatus

• Centrifugal pump provides water

• Direct-injection proportioning system mixes foam/water on discharge side of pump

• Onboard compressor adds air before discharge

Fog vs Foam Nozzles

• Fog nozzles

  • Produce low-expansion, short-lasting foam

  • Foam break into tiny droplets

  • Agitation of water droplets moving through air achieve foam action

  • Some nozzles have aeration attachments to increase aeration

  • Advantages

    • Widely available

    • May allow more flow/patterns

    • Adjustable gallonage of water

    • Faster with preconnected hose

    • Allow margin of safety if foam supply lost

    • Greater reach than foam nozzles

  • Disadvantages

    • Operator error more likely = less foam

    • More equipment/setup time

    • May not have same quality of foam

    • Create look of better flow than actually produced

    • Need maintenance more often if foam used

    • Need to match flow of water with all equipment

    • Don’t provide optimal foam expansion, not best use of foam supply

• Foam nozzles

  • Most effective for low, medium, high expansion foam

  • Inducts air using Venturi effect

  • Designed to provide aeration required to make highest quality foam

  • Best expansion

  • Less stream reach than fog

  • Advantages

    • Produce higher quality foam than Fog nozzle

    • Useful in blanketing ops

  • Disadvantages

    • Not as versatile as Fog nozzle

    • Limited reach compared to other nozzles

Methods of Foam Application

Foam Application Techniques

• Roll-On method

  • Foam stream on ground near front of spill

  • Foam rolls across fuel

  • Continue until extinguished, move to different positions to cover entire pool

  • Only on pool of liquid fuel on open ground

• Bank-Down Method

  • Elevated object near/within area of liquid

  • Foam runs down object onto fuel

  • Primarily on fires in diked pools/storage tanks & spills around damaged transport vehicles

• Rain-Down Method

  • Other 2 methods not feasible

  • Primary manual method on above ground tank fires

  • Foam floats down onto surface

  • Effective to stream 1 area, allow foam to pool, then float out from that point

Operations Involving Liquid & Gas Fuels

Liquid & Gas Fuel Fires

• Flammable liquids

  • Flash points less than 100 F

  • Ignited without being preheated

• Combustible liquids

  • Flash points higher than 100 F

  • Must be heated above flash point before ignition

• Hydrocarbons → Don’t mix with water

• Polar solvents → Mix with water

• Foam → most often to control flammable liquid fires

• Water → cooling agent, mechanical tool, crew protection

• Avoid standing in pools of fuel/contaminated runoff

• PPE can absorb fuel

• Benzene in petroleum product fumes aka carcinogen

Pressurized Vessels

• Propane

  • Liquid petroleum gas (LPG)

  • Stored in pressurized tanks

  • Odorless gas that is heavier than air

  • Ethyl mercaptan added to give it distinct smell

  • Flammable

  • Explosive under right conditions

  • Leak - notify propane company

Valve Control

• Know valve/shutoff being closed and system it affects

• Coordinate with facility personnel supervision

• Gas main valves (vertical = open, horizontal = closed)

Boiling Liquid Expanding Vapor Explosions (BLEVEs)

• Liquid/liquid vessel heated → liquid expands → boiling point → vessel pressure increase → structural integrity fails → contents are released

• PRD allows gases to exit tank

• Safety measures

  • Fight from max distance possible

  • Apply water to upper part of tank, preferably from unattended master stream device

  • Water away from leak

  • Avoid ends of tank

  • Rising sound = leave ASAP

  • Flood outside of tank until fire out

Bulk Transport Fires

• Extinguishment techniques similar to fires in flammable fuel storage facilities

  • Amount of fuel available

  • Possibility of vessel failure

  • Danger to exposures

• Additional challenges

  • Increased life safety risk to FF’s/motorist

  • Less water supply

  • Identifying products, containing spills

  • Instability of vehicle

• Traffic

  • Many incidents handled while traffic passes at normal speed

  • Least 1 lane of traffic & incident lane should be closed during ops

  • Avoid road flares

  • Trained FF’s assigned to direct traffic

• Additional considerations

  • Tires could fail, flammable load can shift

  • Status/limitations of water supply vary

  • May need to protect trapped victims with hose stream

• Determining nature of cargo

  • Bills of lading, manifests, placards, driver

  • Contact shippers/manufactures

• Environmental

  • Prevent runoff of contaminated water, block storm drains

Gas Cylinder Fires

• Fog-stream patterns can be used as crew protection when advancing to shut off valves

• Pressure vessels containing gases are exposed to flame impingement, apply solid stream from max reach

• No angle any safer

Fire in Gas Distribution Systems

• Evacuate ASAP

• Eliminate ignition sources

• Check for gas odor

• Gas burning, flame shouldn’t be extinguished

• Hose stream to protect exposures

• Request hazmat if needed

Prevent Reignition

• Reapply fresh foam for adequate coverage, foam blanket

• Don’t walk, drive, strike foam blanket with solid/straight stream

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