Ch. 14 Foam Equipment and Systems

Question 1

Reasons for Increase in Use of Foam

Answer 1

-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

Question 2

Principles of Foam

Answer 2

• 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)

Question 3

Class B Fuels

Answer 3

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

Question 4

Foam Proportioning

Answer 4

-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

Question 5

Foam Proportioning:
Induction

Answer 5

-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

Question 6

Foam Proportioning:
Injection

Answer 6

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

Question 7

Foam Proportioning:
Batch Mixing

Answer 7

-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

Question 8

Foam Proportioning:
Premixing

Answer 8

-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

Question 9

How Foam is Stored

Answer 9

• 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

Question 10

Class A Foam

Answer 10

-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

Question 11

Class A Proportioning

Answer 11

-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

Question 12

Application of Class A Foam

Answer 12

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

Question 13

Class B Foam

Answer 13

-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

Question 14

Class B Proportioning

Answer 14

-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

Question 16

Foam Expansion

Answer 16

• 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

Question 17

Rates of Application

Answer 17

• 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

Question 18

NFPA 11

Answer 18

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

Question 19

Regular Protein Foams

Answer 19

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

Question 20

Flouroprotein Foam

Answer 20

-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

Question 21

Film Forming Fouroprotein Foam (FFFP)

Answer 21

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

Question 22

Aqueous Film Forming Foam (AFFF)

Answer 22

• 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

Question 23

Low Energy Foam Proportioning System

Answer 23

-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

Question 24

High-Expansion Foam

Answer 24

• 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

Question 25

In-Line Foam Eductor

Answer 25

-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

Question 26

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

Answer 26

-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

Question 27

Foam Nozzle Eductor

Answer 27

-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

Question 28

Self-Educting Master Stream Foam Nozzle

Answer 28

- 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

Question 29

Installed In-Line Eductor Systems

Answer 29

- 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

Question 30

Around-the-Pump Proportioners

Answer 30

- 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

Question 31

Bypass-Type Balanced Pressure Proportioners

Answer 31

- 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

Question 32

Variable-Flow Variable-Rate Direct Injection Systems

Answer 32

- 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

Question 33

Variable-Flow Demand-Type Balanced Pressure Proportioners

Answer 33

- 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

Question 34

Batch Mixing

Answer 34

-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

Question 35

High Energy Foam Generating Systems/CAFS | advantages/disadvantages foam and air rates

Answer 35

- 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

Question 35

Foam: Smooth Bore Nozzles

Answer 35

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

Question 36

Foam: Fog Nozzles

Answer 36

- 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

Question 37

Air-Aspirating Nozzle

Answer 37

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

Question 38

Foam Application Techniques

Answer 38

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

Question 38

Medium-and High-Expansion Foam Generating Devices

Answer 38

- 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

Question 39

Foam Application Techniques: Direct Application

Answer 39

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

Question 40

Foam Application Techniques: Roll-On Method

Answer 40

-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

Question 41

Foam Application Techniques: Bank-Down Method

Answer 41

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

Question 42

Foam Application Techniques: Rain-Down Method

Answer 42

-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

Question 43

Foam: Environmental Impact

Answer 43

-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

Question 44

NFPA 1150

Answer 44

Standard on Foam Chemicals for Fire in Class A Fuels

Question 45

Durable Agents

Answer 45

- "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%