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pumping and aerial apparatus driver/operator handbook 3rd edition > Ch. 14 Foam Equipment and Systems > Flashcards

Ch. 14 Foam Equipment and Systems Flashcards

1
Q

Reasons for Increase in Use of Foam

A

-Magnitude and frequency of hazardous material incidents
-Newer foam concentrates are more easily used
-Improvements in design of foam proportioning units
-Help reduce water usage

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2
Q

Principles of Foam

A
  • Mechanical foams-
    -Most common used
    -Must be proportioned (mixed with water) and aerated (mixed with air)
    -Foam concentrate, water, and air must be educted or injected in correct ratio
  • Foam concentrate- Raw foam liquid in its storage container
  • Foam proportioner- Injects correct amount of foam into water stream
  • Foam solution- Mixture of foam and water before introduction of air
  • Foam- Completed product after air is introduced (finished foam)
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3
Q

Class B Fuels

A

Hydrocarbons- Oil, gasoline, benzene, kerosene, petrol based and have specific gravity less than 1
-Class B foams used on hydrocarbons

Polar Solvents- Alcohol, acetone, ketone, have specific gravity greater than 1
-known as miscible liquids, mix with water, use of alcohol-resistant foam (AR-AFFF) is needed

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4
Q

Foam Proportioning

A

-The act of mixing of water and foam concentrate to form foam
-proportioned THICK for exposures/fire breaks, THIN for easier penetration to surface of fuel
-can be mixed with fresh or salt water
-Must be proportioned at percentage specified by manufacturer
-Mix with 94 to 99.9 percent water
-3 percent foam is 3 parts foam 97 parts water
-Proportioned 4 ways
-Induction -Batch mixing
-Injection -Premixing

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5
Q

Foam Proportioning:
Induction

A

-Uses the pressure of water stream to induct (draft) foam concentrate
-Passes stream of water through a venturi device
-Uses pick up tube to pick up foam from container

Eductor- portable proportioning device that injects foam into water device

Pick up tube- solid or flexible tube to transfer foam from container to eductor

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6
Q

Foam Proportioning:
Injection

A

-Uses external pump to force foam concentrate into fire stream
-Most common in apparatus mounted or fixed fire protection system

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7
Q

Foam Proportioning:
Batch Mixing

A

-Foam concentrate is poured directly into a tank of water
-Commonly used with class A foam
-Class B foam tank must be circulated to ensure proper mixing
-must be thoroughly flushed after use

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8
Q

Foam Proportioning:
Premixing

A

-Premeasured portions of foam and water are mixed in a container
-Used with portable and wheeled extinguishers
-Discharged from pressurized tank using compressed air
-Once used, must be flushed and refilled before used again

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9
Q

How Foam is Stored

A
  • Pails
    -5-gallon plastic pails
    -Easily stored on apparatus
    -Remain airtight
    -Educted directly from pail
  • Barrels
    -55-gallon plastic barrels
    -Bulk storage
  • Totes
    -275-gallon container
    -ARFF, wildland, or industrial facilities
  • Apparatus Tanks
    -Have foam concentrate tanks piped directly to system
    -Municipal range from 20-200 gallons
    -Foam pumper or tenders may carry 8,000 gallons or more, must be air tight
    -Smaller foam concentrate tanks located above the fire pump
    -Larger tanks may be directly adjacent to the apparatus water tank
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10
Q

Class A Foam

A

-Use of structure, wildland, coal, tire storage, and other fires
-Better penetration/effectiveness than water
-Hydrocarbon surfactants- reduce the surface tension of water in the foam
-May be used with fog, aerating nozzles, and medium/high expansion devices, and CAFS w/ most nozzles
-Shelf life of 20 years
-Direct skin contact should be avoided (Corrosive effect)
-Minimum flow rate for water

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11
Q

Class A Proportioning

A

-Class A may be mixed with percentages as little as 0.1 to 1.0 percent
-Most foam nozzles produce stable foam at 1.0 percent
-Fire attack and overhaul with fog 0.2 to 0.5 percent
-Exposure protection with fog 0.5 to 1.0 percent
-Any application with air aspirating nozzle 0.3 to 0.7 percent
-Compressed air 0.2 to 0.5 percent

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12
Q

Application of Class A Foam

A

Application rate- Refers to minimum amount of foam solution that must be applied to fire, per minute, per square foot

Areas that require maximum penetration- Wet foam will penetrate class A fuels

Vertical surface- Dry foam forms a rigid coating that adheres well

Surface of fuel- Ability to cling and penetrate the surface of a fuel

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13
Q

Class B Foam

A

-Flammable and combustible liquids
-also used to suppress unignited vapors

-Consist of synthetic or protein base
-Synthetic foam is made of fluorosurfactants (20-25 years)
-Protein foam is made from animal protein (10 years)
-Protein foams are considered safer
-Mil-spec can be mixed at any time with no adverse effect

-brands of foam should NOT be mixed together except when mixed together immediated before use with similar types

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14
Q

Class B Proportioning

A

-Class B foams are mixed in proportion from 1 to 6 percent
-The correct proportion is found outside of each container
-Hydrocarbons are normally 1 to 3 percent
-Polar solvents are 3 to 6 percent

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15
Q
A
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16
Q

Foam Expansion

A
  • The method used to aerate foam will create varying degrees of expansion based on:
    -Type of foam concentrate used
    -Accurate proportioning of foam to solution
    -Quality of the foam concentrate
    -Method of aeration
  • Low foam expansion 20:1
  • Medium foam expansion 20:1 up to 200:1
  • High foam expansion 200:1 up to 1000:1
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17
Q

Rates of Application

A
  • Rate foam is applied depends on several variables
    -Type of concentrate
    -Whether or not fuel is on fire
    -Type of fuel involved (hydrocarbon vs. polar solvent)
    -Whether fuel is contained or uncontained
  • Before you start application of foam, ensure sufficient amount of foam and equipment are available to achieve objective
  • Application should continue till extinguishment is complete from uphill and upwind
  • Polar solvents may require different application rate based on type of solvent
  • To calculate the application rate available from specific nozzle
    -Divide flow rate by the area of fire250 gpm nozzle on 1,000 sq ft fire
    250 gpm/1,000 sq ft = 0.25 gpm per ft
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18
Q

NFPA 11

A
  • Standard for Low, Medium, and High-Expansion Foam
  • Outlines the variables invloved and application rate requirements for many possible scenarios
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19
Q

Regular Protein Foams

A

-10 year shelf life
-Derived from animal protein
-Has a good heat stability
-Degrades quicker in storage than synthetic foam

20
Q

Flouroprotein Foam

A

-20-25 year shelf life
-Combination of protein and synthetic foam
-Provides longer lasting vapor suppression
-May be made alcohol resistant which is effective for 15 minutes

21
Q

Film Forming Fouroprotein Foam (FFFP)

A

-Long lasting heat resistance
-Capabilities of (AFFF) for quick knockdown
-Also available in alcohol resistant formulation

22
Q

Aqueous Film Forming Foam (AFFF)

A
  • Most commonly used foam
  • Flourochemical surfactants reduce surface tension of water in foam one degree that a thin film is formed to spread across the fuel product
  • Alcohol Resistant AFFF is commonly used on polar solvent
    -AR-AFFF creates a membrane which separates the water in the foam blanket
    -applied gently
    -Aspirating nozzles are generally best for preserving the membrane
23
Q

Low Energy Foam Proportioning System

A

-Operated by one of two basic principles:
-Venturi effect created by pressure of a water stream flowing through a restricted orifice inducts (draft) foam concentrate into water stream
-A pressurized proportioning device injects foam concentrate into water stream at a set ratio and as a higher pressure than the water flow

24
Q

High-Expansion Foam

A
  • Contain detergent base and low water content
  • Provides less runoff and minimizes water damage
  • Common Applications:
    -Concealed space fire
    -fixed extinguishing systems
    -Class A fire
25
Q

In-Line Foam Eductor

A

-Designed to be attached to pump panel discharge or connected in hose lay
-The inline eductor uses venturi principle to draft foam concentrate into water stream
-Foam becomes less viscous when heated

26
Q

Guidelines to achieve properly proportioned finished foam on In-Line Foam Eductor

A

-Flow in gallons per minute through educator must not exceed rated capacity
-Discharge side of educator must not exceed 70 percent of educator inlet pressure
-Concentration will only be accurate if Inlet pressure at the eductor is correct (150-200psi)
-Low pressure will not create venturi
-High pressure concentration may be too rich, rapidly depleting resources
-Eductor properly maintained, run bucket of water through pickup tube for at least one minute
-Metering valves must be set to draw correct percentage
-Eductor should be no more than 6 feet above concentrate
-Nozzle and educator must have same gpm rating

27
Q

Foam Nozzle Eductor

A

-Operates under same principal as in-line educator
-Eductor is built into the self-educting nozzle
-Requires that foam is available where the nozzle is operated

28
Q

Self-Educting Master Stream Foam Nozzle

A
  • Uses modified venturi design to draw concentrate into its water stream
  • Pickup tube is located in the center bore of nozzles
  • Deployed when flows exceed 350 gpm (capable of 14,000 gpm)
  • Advantage is pressure drop is much lower (10 percent or less)
    -allows for much greater reach capabilities
  • Jet ratio controller allows supply at a seperate location as far as 3,000 feet away (Supply master stream)
    -proportions concentrate to 66.5%
    -then further proportioned to 3% at nozzle
29
Q

Installed In-Line Eductor Systems

A
  • operates under same principles as portable in-line eductors
    -only difference is it’s fixed
  • Bypass proportioner is installed to reduce friction loss
    -a valve directs flow through second chamber to allow the switch from water flow to foam
  • Not effective on Class A foam operations
30
Q

Around-the-Pump Proportioners

A
  • Most common type of installed proportioners used in modern fire apparatus
  • Open position valve allows 10 to 40 gpm
  • Disadvantages:
    -older models may only work with onboard tank water
    -inability to pump both foam and water simultaneously
  • Prevention of excess foam use- close bypass valve when line is not flowing
31
Q

Bypass-Type Balanced Pressure Proportioners

A
  • Used on large mobile apparatus such as ARFF vehicle
  • one of the most accurate methods
  • Ability to monitor demand for concentrate and adjust
  • Ability to flow water and foam simultaneously
    -Has a foam concentrate line supplied by separate foam concentrate pump connected to each discharge outlet
32
Q

Variable-Flow Variable-Rate Direct Injection Systems

A
  • ability to proportion any flow rate or pressure with equipment’s design limits
  • able to adjust to changes in water flow as nozzles are opened or closed
  • compatible w/ high energy foam systems (CAFS)
  • Operate off power supplied by the apparatus electrical system
    -some larger units use combo of electric and hydraulic
  • Ratio controlled by speed of a positive displacement pump that inject foam into water flow
    -Rates from 0.1 to 3 percent
  • Class A and Class B foam
    -AR-AFFF not usable
    -Drawback foam flowing in one discharge all discharges are foam
33
Q

Variable-Flow Demand-Type Balanced Pressure Proportioners

A
  • Pump/Demand system
    -consists of variable speed mechanism driven electrically or hydraulically
    -operates foam concentrate pump
  • Flow of concentrate matches the pressure demand
  • water/foam can be discharged simultaneously
  • Requires no flushing afterwards
34
Q

Batch Mixing

A

-Simplest method of proportioning
-Only used in Class A foam concentrate
-Class A do not retain their foam properties when mixed with water for more than 24 hours
-AFFF will stay suspended in solution for extended period of time

35
Q

High Energy Foam Generating Systems/CAFS

advantages/disadvantages
foam and air rates

A
  • Introduce compress air into foam solution
  • CAFS are designed to flow foam through preselected discharges
  • Advantages:
    -allows greater distances than ordinary foam/water streams
    -adheres to fuel surface and resists heat longer
    -hoselines weigh less
  • Disadvantages:
    -price and maintenance costs
    -may have eratic hose reaction
    -Require additional training
  • Proportion rate of 0.1-1%
  • 2 ft³/min of airflow per gallon/min of foam solution produces dry foam of up to 100gpm
    -substantial amount of foam at 10:1 ratio
  • most use airflow rate of 0.5-1.0 ft³/min
    -allows adequate drainage from the blanket to wet the fuel
35
Q

Foam: Smooth Bore Nozzles

A

-Limited to application of Class A foams from a CAFS
-Provides effective stream with excellent reach
-oriface no greater than half of hose diameter

36
Q

Foam: Fog Nozzles

A
  • May operate fixed flow, selective flow, or automatic fog nozzles when applying a low expansion foam blanket
  • Expansion ratio 2:1 up to 4:1
  • most efficient w/ AFFF and Class A Foam
    -AR-AFFF may be used on hydrocarbons
    -not acceptable for fluorprotein foams
  • Not for incidents with polar solvents
  • foam aeration attachments added to increase aspiration
37
Q

Air-Aspirating Nozzle

A

-Induct air into the foam solution
-Only used with protein and Fluoroprotein concentrate
-Provide maximum expansion but reach is limited
-Larger and longer

38
Q

Foam Application Techniques

A

Direct-application method
Roll-on method
Bank-down method
Rain-down method

38
Q

Medium-and High-Expansion Foam Generating Devices

A
  • 2 basic types
    -Water aspirating and mechanical blower
  • Medium Expansion- 20:1 to 200:1
  • High Expansion- 200:1 to 1000:1
  • Water Aspirating
    -Larger and longer
    -Back portion of nozzle is open for airflow
    -End of nozzle has screen that break up foam and mix with air
  • Mechanical Blowers
    -only high expansion
    -look very similar to smoke ejectors
    -Blowers force air into the foam
    -Well suited for incidents requiring total flooding they produce foam with very high air content
39
Q

Foam Application Techniques:
Direct Application

A

-For Class A foam
-Applying finished foam directly onto burning material

40
Q

Foam Application Techniques:
Roll-On Method

A

-Class B Foam
-Direct stream on the ground near front edge of burning liquid
-Foam will then roll across surface of fuel
-Use only for pool of liquid fuel on open ground

41
Q

Foam Application Techniques:
Bank-Down Method

A

-Class B Foam
-Foam is directed onto a vertical surface and allowed to run down and spread across the pooled fuel product

42
Q

Foam Application Techniques:
Rain-Down Method

A

-First two methods are impractical due to elevation
-Fire stream into the air above the fire, allowing the foam to gently rain down on surface of fire
-Incident involving aboveground storage tank

43
Q

Foam: Environmental Impact

A

-Destruction of vegetation and aquatic life
-Biodegradability determine by rate at which bacteria can degrade foam
-Decomposition results in the consumption of oxygen
-No foam should be discharged into any body of water
-NFPA 1150 Standard on Foam Chemicals for Fire in Class A Fuels

44
Q

NFPA 1150

A

Standard on Foam Chemicals for Fire in Class A Fuels

45
Q

Durable Agents

A
  • “gelling agents”
  • Retain their fire retarding properties longer than Class A foam
  • May be airdropped via tank or helicopter
  • Will adhere to vertical structure surfaces up to 24 hours
  • When used as extinguishing agent:
    -ratio: 1:100
    -Fireline: 1.5-2%
    -Structural protection: 2-3%

pumping and aerial apparatus driver/operator handbook 3rd edition (20 decks)

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