Pumping Apparatus Driver/Operator — Lesson 15 Pumping Apparatus Driver/Operator Handbook, 2 nd Edition Chapter 15 — Foam Equipment and Systems

Pumping Apparatus Driver/Operator — Lesson 15

Pumping Apparatus Driver/Operator Handbook, 2nd Edition

Chapter 15 — Foam Equipment and Systems

Pumping Apparatus Driver/Operator

15–2

Learning Objectives

1.List the reasons why foam and durable agents have increased in use in recent years.

2.Match to their definitions terms associated with the foam-making process.

3.Select facts about the principles of foam.(Continued)


15–3

Learning Objectives

4.Explain how foam extinguishes and/or prevents fire.

5.Answer questions about foam proportioning.

6.List the four basic methods by which foam may be proportioned.

(Continued)


15–4

Learning Objectives

7.Select facts about how foam is stored.

8.Answer questions about Class A foam.

9.Explain the common guidelines for performing various applications with Class A foams.

(Continued)


15–5

Learning Objectives

10. List the type of Class A foam required for given situations.

11. Select facts about Class B foam.

12. List the variables that determine the rate of application of Class B foam.

(Continued)


15–6

Learning Objectives

13. List the application rates of Class B foam for common fire scenarios.

14. Explain how to determine the application rate available from a nozzle.

15. Calculate foam application rates.

(Continued)


15–7

Learning Objectives

16. Select facts about specific foam concentrates.

17. List the three things that happen when Aqueous Film Forming Foam (AFFF) is applied to a hydrocarbon fire.

18. List the three basic applications of high-expansion foams.

(Continued)


15–8

Learning Objectives

19. Describe the two principles by which foam proportioning devices operate.

20. Answer questions about portable foam proportioners.

21. List the operating rules when using eductors.

(Continued)


15–9

Learning Objectives

22. Answer questions about apparatus-mounted foam proportioning systems.

23. Distinguish between advantages and limitations of compressed-air foam systems (CAFS).

24. Identify characteristics of various portable foam application devices.

(Continued)


15–10

Learning Objectives

25. Install an in-line foam eductor and operate a high expansion foam generator.

26. Select from a list the reasons for failure to generate foam or for generating poor quality foam.

27. Match to their definitions various foam application techniques.

(Continued)


15–11

Learning Objectives

28. Answer questions about the environmental impact of foam concentrates and solutions.

29. Select facts about durable agents.


15–12

Why Foam and Durable Agents Have Increased in Use Recently

• Magnitude and frequency of hazardous materials incidents requiring foam for control

• New advances in foam concentrate technology that have provided products which are more easily used by municipal and wildland firefighters

(Continued)


15–13

Why Foam and Durable Agents Have Increased in Use Recently

• Technological improvements in foam proportioning equipment and systems that make their inclusion in the construction of new fire apparatus, or the retrofitting of existing apparatus, feasible for many fire departments


15–14

Foam Terms

• Proportion — To mix with water

• Aerate — To mix with air

• Foam concentrate — The raw foam liquid in its storage container before being combined with air and water

(Continued)


15–15

Foam Terms

• Foam proportioner — The device that introduces foam concentrate into the water stream to make the foam solution

• Foam solution — The mixture of foam concentrate and water before the introduction of air

• Foam — The completed product after air is introduced into the foam solution


15–16

Principles of Foam

• To produce quality fire fighting foam, foam concentrate, water, air, and mechanical aeration are needed.

(Continued)


15–17

Principles of Foam

• Proper aeration should produce uniform-sized bubbles to provide a longer lasting blanket. A good foam blanket must maintain cover over either Class A or Class B fuels for the required period of time.

(Continued)


15–18

Principles of Foam

• Some foams are now available that are rated for use on fires in both Class A and Class B fuels.

• If a department still has single-class foam only, each must be matched to the fuel for which it was formulated.

(Continued)


15–19

Principles of Foam

• Class B fuels– Hydrocarbons — Petroleum based and float on

water; Class B foam is effective as an extinguishing agent.

Examples: Crude oil, fuel oil, gasoline, benzene, naphtha, jet fuel, and kerosene

(Continued)


15–20

Principles of Foam

• Class B fuels– Polar solvents — Flammable liquids that mix with

water; foam can be effective, but only in special alcohol-resistant formulations

Examples: Alcohol, acetone, lacquer thinner, ketones, and esters

(Continued)


15–21

Principles of Foam

• Class B foams designed solely for hydrocarbon fires will not extinguish polar solvent fires regardless of the concentration at which they are used. However, many foams that are intended for polar solvents may be used on hydrocarbon fires, but this should not be attempted unless the manufacturer of the particular concentrate being used says this is permissible.

(Continued)


15–22

Principles of Foam

CAUTION! Failure to match the proper foam concentrate with the fuel can result in an unsuccessful extinguishing effort and could endanger firefighters.


15–23

How Foam Extinguishes and/or Prevents Fire

• Separating — Creates a barrier between the fuel and the fire

• Cooling — Lowers the temperature of the fuel and adjacent surfaces

(Continued)


15–24


• Suppressing (sometimes referred to as smothering) — Prevents the release of flammable vapors and therefore reduces the possiblity of ignition or reignition

(Continued)


15–25



15–26

Foam Proportioning

• Describes the mixing of water with foam concentrate to form a foam solution

• For maximum effectiveness, foam concentrates must be proportioned at the specific percentage for which they are formulated. This rate is clearly marked on the outside of the foam container.

(Continued)


15–27

Foam Proportioning

• Most fire fighting foam concentrates are intended to be mixed with 94 to 99.9% water.

Example: When using 3% foam concentrate, 97 parts water mixed with 3 parts foam concentrate equals 100 parts foam solution.

(Continued)


15–28

Foam Proportioning

• Class A foams are not proportioned as other foams. Their percentage can be adjusted (within limits) to achieve specific objectives.– Dry (thick) foam suitable for exposure

protection and fire breaks require higher percentage of foam.

– Wet (thin) foam that rapidly sinks into a fuel’s surface can be adjusted to a lower percentage. (Continued)


15–29

Foam Proportioning

• The selection of a proportioner depends on the foam solution, foam requirements, available water pressure, cost, intended use, and the agent to be used.

(Continued)


15–30

Foam Proportioning

• Proportioners and delivery devices are engineered to work together. Using a foam proportioner that is not compatible with the delivery device can result in unsatisfactory foam or no foam at all.


15–31

Methods by Which Foam May be Proportioned

• Induction

• Injection

• Batch mixing

• Premixing


15–32

Induction

• Uses the pressure energy in the stream of water to induct (draft) foam concentrate into the fire stream

• Is achieved by passing the stream of water through a venturi device called an eductor

Examples: In-line eductors and foam nozzle eductors

(Continued)


15–33

Induction


15–34

Injection

• Uses an external pump or head pressure to force foam concentrate into the fire stream at the correct ratio in comparison to the flow


15–35

Batch Mixing

• Is the simplest method of mixing foam concentrate and water

• Occurs when an appropriate amount of foam concentrate is poured into a tank of water

• Is commonly used to mix foam within a fire apparatus water tank or a portable water tank

(Continued)


15–36

Batch Mixing

• Is common with Class A foam but should only be used as last resort with Class B foam

• May not be effective on large incidents – When the tank becomes empty, the foam attack

lines must be shut down until the tank is filled with water and more concentrate is added

• Requires that the pump and associated piping must be thoroughly flushed after use


15–37

How Foam is Stored

• Foam concentrate is stored in a variety of containers, depending on the procedural manner in which the foam is generated and delivered. The four common foam concentrate storage methods include pails, barrels, 275 gallon (1 100 L) tote tanks, and apparatus tanks.


15–38

Pails

• Are usually 5-gallon (20 L), made of plastic

• Are perhaps the most common containers used by the muncipal fire service to receive and store foam concentrate

• Are durable and are not affected by the corrosive nature of foam concentrates

(Continued)


15–39

Pails

• May be carried on the apparatus in compartments, on the side of the apparatus, or in topside storage areas

• May be airtight to prevent a skin from forming on the surface


15–40

Barrels

• Are used for larger quantities of concentrate

• Are usually 55-gallon (220 L) plastic or plastic-lined barrels or drums

• Are most common in industrial applications

(Continued)


15–41

Barrels

• May be carried directly to the emergency scene or may need to be transferred to pails or apparatus tanks for transport to the point of application


15–42

Totes

• Are 275-gallon (1 100 L) containers used for bulk storage of foam concentrate

• Are used for large quantities of foam, such as in aircraft rescue and fire fighting (ARFF), industrial, or wildland firefighting applications


15–43

Apparatus Tanks

• Are found on municipal and industrial pumpers, foam tenders, and ARFF apparatus

• Eliminate the need to use separate pails or barrels

(Continued)


15–44

Apparatus Tanks

• Vary in type, location, and design– Smaller foam tanks are located directly

above the fire pump area.– Newer designs incorporate foam tanks as

an integral cell within the water tank– Some apparatus have an additional pump

and connection nearer ground level for refilling the concentrate tank.

(Continued)


15–45

Apparatus Tanks

• Vary in type, location, and design– Large foam concentrate tanks may be

directly adjacent to the water tank.– Foam tenders and some industrial foam

pumpers have a large tank that contains foam concentrate and no water tank.

(Continued)


15–46

Apparatus Tanks

• Must be airtight

• Should have a pressure vacuum vent

• Range from 20 to 200 gallons (80 L to 800 L)

• May carry 8,000 gallons (32 000 L) or more of concentrate


15–47

Class A Foam

• Is intended for use on Class A fuels

• Is effective for fires in structures, wildland settings, coal mines, tire storage, and other incidents involving deep-seated fuels

WARNING! Use Class A foam only on Class A fuels. It is not specifically formulated for fighting Class B fuels.

(Continued)


15–48

Class A Foam

• Is the formulation of hydrocarbon surfactants that reduce the surface tension of the water in the foam solution. Reducing the surface tension provides better penetration of the water, thereby increasing its effectiveness.

(Continued)


15–49

Class A Foam

• May be used with fog nozzles, aerating foam nozzles, medium- and high-expansion devices, and compressed-air foam systems using almost any nozzle

• Has a shelf life of as much as 20 years if properly stored

(Continued)


15–50

Class A Foam

• Is used in such small percentages in solution that harm to the environment is not usually a concern; however, there is some evidence that the concentrate may slightly affect aquatic life, so direct application into bodies of water is not recommended

(Continued)


15–51

Class A Foam

• Has corrosive and supercleaning characteristics, so direct skin contact should be avoided. Properly flushing application equipment after use is also recommended


15–52

Proportioning Class A Foams

• Some Class A foam concentrates are mixed in proportions of 0.1% to 1.0%. As the expansion ratios are increased, the expansion and drainage characteristics of the foam change.

(Continued)


15–53

Proportioning Class A Foams

• Most foam nozzles produce more stable foams at 1.0% concentration than at 0.4% or 0.5% concentrations.

• Using percentages greater than 0.5% with standard fog nozzles does not appear to increase fire fighting performance.


15–54

Performing Various Applications with Class A Foams

• Fire attack and overhaul with standard fog nozzles– 0.2% to 0.5% foam concentrate

• Exposure protection with standard fog nozzles– 0.5% to 1.0% foam concentrate

(Continued)


15–55

Performing Various Applications with Class A Foams

• Any application with air aspirating foam nozzles– 0.3% to 0.7% foam concentrate

• Any application with compressed air foam systems– 0.2% to 0.5% foam concentrate


15–56

Application of Class A Foam

• Areas requiring maximum penetration– Wet foam is very fluid and is desirable for

these areas.

• Vertical surfaces– Dry foam is a rigid coat that adheres well.

Its slow drainage rate allows it to cling to surfaces for extended periods.

(Continued)


15–57

Application of Class A Foam

• Areas requiring a balance of penetration and clinging ability– Medium foam has the ability to blanket and

wet the fuel equally well.


15–58

Class B Foam

• Is used to extinguish fires involving flammable and combustible liquids

• Is used to suppress vapors from unignited spills of flammable and combustible liquids

• May be applied either with standard fog nozzles or with air-aspirating foam nozzles

(Continued)


15–59

Class B Foam

• May be proportioned into the fire stream via apparatus-mounted or portable foam proportioning equipment

• Is manufactured from either a synthetic or protein base

(Continued)


15–60

Class B Foam

• Protein-based foams– Are derived from animal protein– Have a shelf life of about 10 years– Are generally safer for the environment

• Synthetic-based foams– Are made from fluorosurfactants– Have a shelf life of 20 to 25 years


15–61

Proportioning Class B Foam

• Today’s Class B foams are mixed in proportions from 1% to 6%.

• Some multipurpose foams designed for use on both hydrocarbon and polar solvent fuels can be used at different concentrations, depending on which of the two fuels they are used on.

(Continued)


15–62

Proportioning Class B Foam

• Older polar solvent mechanical foam concentrates were designed to be used at concentrations of 6% or greater. These concentrates are not commonly found in use today.


15–63

Foam Expansion

• The increase in volume of foam solution when aerated

• The method of aerating results in varying degrees of expansion, which depends on:– Type of foam concentrate used– Accurate proportioning of the foam concentrate in

the solution– Quality of the foam concentrate– Method of aspiration


15–64

Rate of Application for Class B Foam

• Depends on– Type of foam concentrate used– Whether or not the fuel is on fire– Type of fuel (hydrocarbon/polar solvent)

involved– Whether the fuel is spilled or in a tank; if

the fuel is in a tank, the type of tank will have a bearing on the application rate.

(Continued)


15–65


• Hydrocarbon fuel spill fires (nondiked) using portable extinguishing equipment– Protein and fluoroprotein foams —

0.16 gpm/ft2 (6.5 [L/min]/m2) for 15 minutes– ARFF and FFFP — 0.10 gpm/ft2

(4.1 [L/min]/m2) for 15 minutes

(Continued)


15–66


• Polar solvent fuel spill fires (nondiked) using portable extinguishing equipment– Between 0.10 and 0.20 gpm/ft2

(4.1 [L/min]/m2 and 8.2 [L/min]/m2), depending on the manufacturer’s UL listing

(Continued)


15–67


• Hydrocarbon fuel fires in fixed roof storage tanks using portable extinguishing equipment– 0.16 gpm/ft2 (6.5 [L/min]/m2)


15–68

Determining the Application Rate from a Nozzle

• Divide nozzle flow rate by area of the fire– A 250 gpm [1 000

L/min] nozzle on a 1,000-square-foot (100 m2) fire equals a rate of 0.25 gpm per square foot (10 [L/min]/m2)


15–69

Regular Protein Foams

• Are derived from naturally occurring sources of protein such as hoof, horn, or feather meal

• Have good heat stability and resist burnback

• Are not as mobile or fluid on the fuel surface as are other types of low-expansion foams

(Continued)


15–70

Regular Protein Foams

• Degrade faster in storage than do synthetic foams

• Are rarely used in the fire service today


15–71

Fluoroprotein Foam

• Is derived from protein foam concentrates to which fluorochemical surfactants are added

• Flows more easily than regular protein foam

(Continued)


15–72

Fluoroprotein Foam

• Provides a strong “security blanket” for long-term vapor suppression

• Can be formulated to be alcohol resistant by adding ammonia salts; this foam maintains its alcohol-resistive property for about 15 minutes


15–73

Film Forming Fluoroprotein Foam (FFFP)

• Is based on fluoroprotein foam technology with aqueous film forming foam (AFFF) capabilities

• Incorporates AFFF benefits for fast fire knockdown with the benefits of fluoroprotein foam for long-lasting heat resistance

• Is available in an alcohol-resistant formulation


15–74

Aqueous Film Forming Foam (AFFF)

• Is the most commonly used foam today

• Is completely synthetic

• Consists of fluorochemical and hydrocarbon surfactants combined with high boiling point solvents and water

(Continued)


15–75


• When applied to a hydrocarbon fire, three things occur:– An air/vapor-excluding film is released

ahead of the foam blanket.

– The fast-moving foam blanket then moves across the surface and around objects, adding further insulation.

(Continued)


15–76


• When applied to a hydrocarbon fire, three things occur:– As the aerated (7:1 to 20:1) foam blanket continues to

drain water, more film is released, giving AFFF the ability to “heal” over areas where the foam blanket is disturbed.


15–77

Alcohol-Resistant AFFF

• Are usually used at 3% or 6% on polar solvents and 1% or 3% on hydrocarbons– Those used at 3% on hydrocarbons and 6% on

polar solvents are called 3 by 6 concentrates.

– Those used at 3% on both types of fuels are called 3 by 3 concentrates.

– Those used at 1% on hydrocarbons and 3% on polar solvents are called 1 by 3 concentrates.

(Continued)


15–78

Alcohol-Resistant AFFF

• Create a membrane over polar solvent fuels, rather than a film; this separates the water in the foam blanket from attack of the solvent

• Should be applied gently so that the membrane can form first

• Should not be plunged into the fuel, but sprayed over the top


15–79

High-Expansion Foams

• Are special-purpose foams

• Have a detergent base

• Have a low water content, which minimizes water damage

(Continued)


15–80


• Have three basic applications:– In concealed spaces such as basements,

coal mines, and other subterranean spaces– In fixed-extinguishing systems for specific

industrial uses (rolled or bulk paper storage)– In Class A fire applications

(Continued)


15–81


• Have expansion ratios of 200:1 to 1,000:1 for high-expansion uses and 20:1 to 200:1 for medium-expansion uses


15–82

Foam Proportioning Devices

• Although the process of foam proportioning sounds simple, failure to operate even the best foam proportioning equipment as designed can result in poor quality foam or no foam at all.

(Continued)


15–83

Foam Proportioning Devices

• In general, foam proportioning devices operate by one of two basic principles:– The pressure of the water stream flowing through

a restricted orifice creates a venturi action that inducts (drafts) foam concentrate into the water stream.

– Pressurized proportioning devices inject foam concentrate into the water stream at a desired ratio and at a higher pressure than that of the water.


15–84

In-Line Foam Eductors

• Are the most basic type of foam proportioner

• Are designed to be either directly attached to the pump panel discharge or connected at some point in the hose lay

(Continued)


15–85

In-Line Foam Eductors

• Must follow manufacturer's instructions about inlet pressure and the maximum hose lay between the eductor and the appropriate nozzle

• Use the Venturi Principle to draft foam concentrate into the water stream


15–86

Venturi Principle

• As water at high-pressure passes through a restriction, it creates a low-pressure area within the eductor.

• The low-pressure area creates a suction effect (called the Venturi Principle).

• The educator pickup tube is connected to the eductor at this low-pressure point.

(Continued)


15–87

Venturi Principle

• Atmospheric pressure forces foam concentrate into a pickup tube and into the water stream, creating a foam/water solution.


15–88

Operating Rules to Observe When Using Eductors

• The eductor must control the flow through the system.

• The pressure at the outlet of the eductor must not exceed 65 to 70 percent of the eductor inlet pressure.

(Continued)


15–89


• Foam solution concentration is only correct at the rated inlet pressure of the eductor, usually 150 to 200 psi (1 050 kPa to 1 400 kPa).

• Eductors must be properly maintained and flushed after each use.

(Continued)


15–90


• Metering valves must be set to match foam concentrate percentage and the burning fuel.

• The foam concentrate inlet to the eductor should not be more than 6 feet (2 m) above the liquid surface of the foam concentrate (Continued)


15–91


• For nozzle and eductor to operate properly, both must have the same gpm (L/min) rating.

• The eductor, not the nozzle, controls the flow.

• If the nozzle has a lower flow rating than the eductor, the eductor will not flow enough water to pick up concentrate.

• Using a nozzle with a higher rating than the eductor also gives poor results.


15–92

Foam Nozzle Eductors

• Operate on the same principle as the in-line eductor, but the eductor is built into the nozzle rather than into the hoseline

• Require the foam concentrate to be available where the nozzle is operated; if the foam nozzle is moved, the foam concentrate also needs to be moved

(Continued)


15–93

Foam Nozzle Eductors

• Compromise firefighter safety; firefighters cannot move quickly, and they must leave their concentrate behind if they are required to back out for any reason


15–94

Self-Educting Master Stream Foam Nozzles

• Are used where flows in excess of 350 gpm (1 400 L/min) are required

• Are available with flow capabilities of up to 14,000 gpm (56 000 L/min)

• Use a modified venturi design to draw foam concentrate into the water stream

(Continued)


15–95

Self-Educting Master Stream Foam Nozzles

• Advantage — A much lower pressure drop (10% or less) than typically associated with standard foam nozzle eductors, allowing for greater stream reach capabilities

• May use a jet ratio controller (JRC) to supply foam concentrate to a self-educting master stream nozzle


15–96

Jet Ratio Controller (JRC)

• A type of in-line eductor that allows the foam concentrate supply to be as far away as 3,000 feet (900 m) from the self-educting master stream foam nozzle

• Allows an elevation change of up to 50 feet (15 m).

(Continued)


15–97


• Is supplied by a hoseline from the same fire pump that is supplying other hoses to the nozzle

• Flow of water to it represents about 2½ percent of the total flow in the system

(Continued)


15–98


• As with a standard in-line eductor, as water flows through the JRC, a venturi draws concentrate through the pickup tube and into the hoseline. The difference is that the JRC proportions the concentrate at a 66½ percent solution.

(Continued)


15–99


• This rich solution is then pumped to a self-educting master stream foam nozzle where it is further proportioned with the water supplied by the fire pump down to a discharge proportion of 3%. To achieve a proper proportion, it is important that the JRC and nozzle match.


15–100

Installed In-Line Eductor Systems

• Use the same principles of operation as do portable in-line eductors, but are attached to the apparatus pumping system

• Should follow the same precautions as portable in-line eductors regarding hose lengths, matching nozzle and eductor flows, and inlet pressures

(Continued)


15–101


• Have foam concentrate supplied from either pickup tubes inserted into 5 gallon (20 L) pails or from foam concentrate tanks installed on the apparatus

• Include a special version called a bypass proportioner that is used to reduce the friction loss across the eductor

(Continued)


15–102


• Are most commonly used to proportion Class B foams


15–103

Around-the-Pump Proportioners

• Are one of the most common types of built-in proportioners installed in mobile fire apparatus today

(Continued)


15–104

Around-the-Pump Proportioners

• Consist of a small return (bypass) water line connected from the discharge side of the pump back into the intake side of the pump

• Are rated for a specific flow and should be used at this rate


15–105

Disadvantages of Around-the-Pump Proportioners

• The pump cannot take advantage of incoming pressure. If the inlet water supply is any greater than 10 psi (70 kPa), the foam concentrate will not enter the pump intake. Some newer units are capable of handling intake pressures of up to 40 psi (280 kPa).

(Continued)


15–106


• The pump must be dedicated solely to foam operation. An around-the-pump proportioner does not allow plain water and foam to discharge from the pump at the same time.

(Continued)


15–107


• When lines are shut down, water can still circulate through the eductor adding more concentrate than needed. To avoid this, the bypass valve should be closed when no water is flowing.


15–108

Bypass-Type Balanced Pressure Proportioners

• Are one of the most accurate methods of foam proportioning

• Are most commonly used in large-scale mobile apparatus applications such as airport crash vehicles and refinery fire fighting apparatus

(Continued)


15–109


(Continued)


15–110


• Advantages– Its ability to monitor the demand for foam

concentrate and to adjust the amount of concentrate supplied.

– Its ability to discharge foam from some outlets and plain water from others at the same time.

(Continued)


15–111


• Apparatus equipped with these proportioners have a foam concentrate line connected to each fire pump discharge outlet.

• This line is supplied by a foam concentrate pump separate from the main fire pump.

(Continued)


15–112


• The foam concentrate pump draws the concentrate from an onboard tank.

• This pump is designed to supply foam concentrate to the outlet at the same pressure at which the fire pump is supplying water to that discharge.

(Continued)


15–113


• The pump discharge and the foam concentrate pressure from the foam concentrate pump are jointly monitored by a hydraulic pressure control valve that ensures the concentrate pressure and water pressure are balanced.

(Continued)


15–114


• The orifice of the foam concentrate line is adjustable at the point where it connects to the discharge line.

• If 3% foam is used, the orifice is set to 3% of the total size of the water discharge outlet.

• If 6% foam is used, the orifice is set to 6% of the total size of the water discharge outlet.

(Continued)


15–115


• Limitations– Its need for a foam pump with PTO or other

power source– Bypass of concentrate in this system can

cause heating, turbulence, and foam concentrate aeration


15–116

Variable-Flow Variable-Rate Direct Injection Systems

• Operate off power supplied from the apparatus electrical system

• Are controlled by monitoring the water flow and controlling the speed of a positive displacement foam concentrate pump, thus injecting concentrate at the desired ratio

(Continued)


15–117


• Allow full flow through the fire pump discharges because there are no flow-restricting passages in the proportioning system

• Provide foam concentrate rates from 0.1% to 3%

(Continued)


15–118


• Have a control unit with a digital display that shows the current water or foam solution flow rate, the total amount of water or solution flowed to this time, the current foam concentrate flow rate, and the amount of foam concentrate used to this time

(Continued)


15–119


• Can be used with all Class A foam concentrates and many Class B concentrates

• CANNOT be used with alcohol-resistant foam concentrates


15–120

Advantages of Variable-Flow Variable-Rate Direct Injection Systems

• Their ability to proportion at any flow rate or pressure within the design limits of the system

• The system automatically adjusts to changes in water flow when nozzles are either opened or closed

(Continued)


15–121

Advantages of Variable-Flow Variable-Rate Direct Injection Systems

• Nozzles may be either above or below the pump, without affecting the foam proportioning

• May be used with high-energy foam systems


15–122

Disadvantage of Variable-Flow Variable-Rate Direct Injection Systems

• The foam injection point must be within the piping before any manifolds or distribution to multiple fire pump discharges. This means that if foam solution is flowing through one pump discharge, only foam solution can be flowed through any other discharge that is plumbed to that discharge manifold.


15–123

Variable-Flow Demand-Type Balanced Pressure Proportioners

• Are versatile systems

• Have a variable-speed mechanism, which is either hydraulically or electrically controlled, that drives a foam concentrate pump; the pump supplies concentrate to a Venturi-type proportioning device built into the water line

(Continued)


15–124

Variable-Flow Demand-Type Balanced Pressure Proportioners


15–125

Advantages of Variable-Flow Demand-Type Balanced Pressure Proportioners

• The foam concentrate flow and pressure match system demand

• No recirculation back to the foam concentration tank

(Continued)


15–126

Advantages of Variable-Flow Demand-Type Balanced Pressure Proportioners

• System is maintained in a ready-to-pump condition and requires no flushing after use

• Water and/or foam solution can be discharged simultaneously from any combination of outlets up to rated capacity


15–127

Limitation of Variable-Flow Demand-Type Balanced Pressure Proportioners

• The fire pump discharges have ratio controllers, thus pressure drops across the discharge are higher than those on standard pumpers.


15–128

Batch-Mixing

• Is the simplest means of proportioning foam

• Is simply pouring an appropriate amount of foam concentrate into a tank of water

(Continued)


15–129

Batch-Mixing

• Occurs when the driver/operator pours a predetermined amount of foam concentrate into the tank via the top fill opening at the time foam is needed; the pump is operated normally, and foam is discharged through any hoseline that is opened

(Continued)


15–130

Batch-Mixing

• Means that the size of the water tank and the proportioning percentage of the foam concentrate dictate how much concentrate must be poured into the water tank

• Is only used with regular AFFF (not alcohol-resistant AFFF concentrates) and Class A concentrates

(Continued)


15–131

Batch-Mixing

• Can be done at any time, anywhere, and with any equipment, and eliminates the need for costly foam proportioning equipment

(Continued)


15–132

Batch-Mixing

Note: Apparatus water tanks, pumps, and associated piping should be thoroughly flushed with fresh water after any pumping operation in which a foaming agent was batch-mixed in the vehicle’s water tank. The flushing operation must be conducted according to the MSDS supplied by the foam manufacturer.


15–133

Disadvantages of Batch-Mixing

• Class A foam solutions do not retain their foaming properties if mixed in the water for more than 24 hours, and there may be further degradation, depending on the product used

• Froth may form when the water tank is refilled

(Continued)


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• Foam solutions are solvents, so they can remove lubricants from ball valve seals

• All the water onboard the apparatus is converted to foam solution

(Continued)


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• Does not allow for continuous foam discharge because the stream has to shut down while the apparatus tank is refilled

• It is difficult to maintain the concentrate ratio unless the water tank is completely emptied each time


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History of Compressed-Air Foam Systems (CAFS)

• Instead of using air cylinders, as was popular in the 1970s, the U.S. Bureau of Land Management added a rotary air compressor to a standard fire department pumper.

(Continued)


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History of Compressed-Air Foam Systems (CAFS)

• This system uses a standard centrifugal fire pump to supply the water. Once the foam concentrate and water are mixed to form a foam solution, compressed air is added to the mixture before it is discharged from the apparatus and into the hoseline.


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Advantages of CAFS

• A considerably longer fire stream than streams from low-energy systems

• Produce uniformly sized, small air bubbles that are very durable.

• The foam adheres to the fuel surface and resists heat longer than low-energy foam.

(Continued)


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Advantages of CAFS

• Hoselines containing high-energy foam solution weigh less than hoselines containing low-energy foam solution or plain water.

• A CAFS provides a safer fire suppression action that allows effective attack on the fire from a greater distance.


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Disadvantages of CAFS

• A CAFS adds expense to a vehicle and adds to the maintenance that must be performed on the vehicle.

• Hose reaction can be erratic if foam solution is not supplied to the hoseline in sufficient quantities.

(Continued)


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Disadvantages of CAFS

• The compressed air accentuates the hose reaction in the event the hose ruptures.

• Additional training is required for personnel who are expected to make a fire attack using a CAFS or who will operate CAFS equipment.


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Characteristics of CAFS

• Most apparatus equipped with a CAFS are also designed to flow plain water should the choice be made to do that.

• The fire pump used on a CAFS-equipped fire vehicle is a standard centrifugal fire pump.

(Continued)


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• The foam proportioning system is a type of automatic, discharge-side proportioning system.

• Foam eductors are typically not used because they are not designed to work at either the 0.1% or 1% eduction rates or the variable flow rates required for Class A foams.

(Continued)


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• Variable-flow rate sensing proportioners are necessary to ensure that foam concentrate is supplied to the fire stream at the proper rate.

• In general, 2 cubic feet per minute (cfm)(0.06 m3/min) of airflow per gallon minute of foam solution flow produces a very dry foam at flows of up to 100 gpm (400 L/min) of foam solution.

(Continued)


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• Most structural and wildland fire attacks using CAFS are done with an air flow rate of 0.5 to 10.5 cfm (0.015 m3/min to 0.03 m3/min).

CAUTION! To protect fire attack teams, nozzle flow rates (gpm, L/min) should be the same for Class A foam application as for plain water.


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Portable Foam Application Devices

• While standard fire fighting nozzles can be used for applying some types of low-expansion foams, it is best to use nozzles that produce the desired result (such as fast-draining or slow-draining foam).


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Handline Nozzles

• Any nozzle that one to three firefighters can safely handle and that flows less than 350 gpm (1 400 L/min)

• Smooth bore nozzles

• Fog nozzles

• Air-aspirating foam nozzles


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Smooth Bore Nozzles

• Are limited to Class A, CAFS applications

• Provide an effective fire stream that has maximum reach capabilties

• When using, disregard the standard rule that the discharge orifice of the nozzle be no more than one-half the diameter of the hose


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Fog Nozzles

• Break the foam solution into tiny droplets and use the agitation of water droplets moving through air to achieve the foaming action

• Have expansion ratios between 2:1 and 4:1

(Continued)


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Fog Nozzles

• Are best when used with regular AFFF and Class A foams, but may be used with alcohol-resistant AFFF foams on hydrocarbon fires

• Cannot be used with protein and fluoroprotein foams and should not be used on polar solvent fires

(Continued)


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Fog Nozzles

• Some have foam aeration attachments that can be added to the end of the nozzle to increase aspiration of the foam solution

• Some have an adjustable sleeve that allows them to convert to air-aspirating nozzles


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Air-Aspirating Foam Nozzles

• Induct air into the foam solution by a venturi action

• Are the only type of nozzles that can be used with protein and fluoroprotein concentrates

(Continued)


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Air-Aspirating Foam Nozzles

• May also be used with Class A foams in wildland applications

• Provide maximum expansion of the agent

• Have less stream reach than that of a standard fog nozzle


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Master Stream Foam Nozzles

• Large-scale flammable and combustible liquid fires are beyond the capabilities of handlines. Master stream nozzles are required to deliver adequate amounts of foam in these situations. (Continued)


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Master Stream Foam Nozzles

• Standard fixed-flow or automatic-fog master stream nozzles may be used to deliver foam, when necessary.

• Large-scale industrial foam apparatus and AFFF vehicles may be equipped with special aerating foam master stream nozzles.


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Medium- and High-Expansion Foam Generating Devices

• Produce a high-air-content, semistable foam– Medium-expansion — Air content ranges from 20

parts air to 1 part foam solution (20:1) to 200 parts air to 1 part foam solution (200:1)

– High-expansion — Ranges from 200:1 to 1,000:1

• Water-aspirating type

• Mechanical blower type


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Water-Aspirating Type

• Is similar to other foam-producing nozzles except that it is much larger and longer

• Has a back that is open to allow airflow

• Pumps foam solution through the nozzle in a fine spray that mixes with air to form a moderate-expansion foam

(Continued)


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Water-Aspirating Type

• Has a screen on the end that further breaks up the air and mixes it with water

• Typically produces a lower-air-volume foam than do mechanical blower generators


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Mechanical Blower Type

• Is similar in appearance to a smoke ejector

• Operates on the same principle as the water-aspirating nozzle except that the air is forced through the foam spray by a powered fan instead of being pulled through by water movement

(Continued)


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Mechanical Blower Type

• Produces foam with a high air content and is typically associated with total-flooding application

• Is limited in use to high-expansion foams


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Reasons for Failure to Generate Foam or for Generating Poor Quality Foam

• Failure to match eductor and nozzle flow, resulting in no pickup of foam concentrate

• Air leaks at fittings that cause loss of suction

• Improper cleaning of proportioning equipment that results in clogged foam passages

(Continued)


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• Partially closed nozzle that results in a higher nozzle pressure

• Too long a hose lay on the discharge side of the eductor

• Kinked hose

(Continued)


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• Nozzle too far above eductor (results in excessive elevation pressure)

• Mixing different types of foam concentrates in the same tank, which can result in a mixture too viscous to pass through the eductor


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Various Foam Application Techniques

• Direct-application method– Finished Class A foam in applied directly

onto the material that is burning.

(Continued)


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• Roll-on method– Directs Class B foam stream on the ground

near the front edge of a burning liquid pool or spill. The foam then rolls across the surface of the fuel. Foam application continues until it spreads across the entire surface of the fuel and the fire is extinguished or the vapors suppressed.

(Continued)


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• Roll-on method

(Continued)


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• Bank-down method– Class B foam

stream is directed onto a vertical surface, allowing foam to run down onto and spread across surface of the fuel.

(Continued)


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• Rain-down method– Directs stream of

Class B foam into the air above fire and allows foam to gently rain down onto surface of fuel.


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Environmental Impact of Class A and Class B Foam Concentrates and Solutions

• The primary concern is the impact of finished foam after it has been applied to a fire or spill.

• The biodegradability of these foams in either solution or concentrate is determined by the rate at which environmental bacteria dissolve or degrade the foam.

(Continued)


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Environmental Impact of Class A and Class B Foam Concentrates and Solutions

• The decomposition of these foams results in the consumption of oxygen. In waterways, a reduction in oxygen can kill water-inhabiting creatures and vegetation.

• Foam concentrates, solutions, or finished foam should not be discharged into any body of water.


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Environmental Impact of AFFF Concentrate

• Environmental issues revolve around glycol ethers and perfluoroctylysulfonates (PFOS). Foam manufacturers are trying to find alternatives to these chemicals.


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Durable Agents

• Are the term used for a number of different water additives used as extinguishing agents and for pretreating structures threatened by fires spreading toward them

• Retain their fire retarding properties longer than Class A foam

(Continued)


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Durable Agents

• Are also known as gelling agents, fire blocking gels, and aqueous fire fighting gels

• Are used in the same way as Class A foam, but are chemically and structurally quite different

(Continued)


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Durable Agents

• Are different from Class A foam in that they:– Are water-absorbent polymers rather than

hydrocarbon-based surfactants like Class A foams– When mixed with water, form minute polymer

bubbles that are filled with water; Class A foams form tiny water bubbles that are filled with air

– Are considerably more expensive– Make surfaces to which applied very slippery

(Continued)


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Durable Agents

• Are normally siphoned from a container with an eductor, but in an emergency can be batch-mixed in the apparatus water tank

• Can be used for fire extinguishment, line construction, or structure protection

(Continued)


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Durable Agents

• Can be applied through hoselines with any standard fire nozzle, including master stream appliances, or dropped by air tankers or helicopters

• Are normally applied at a ratio of 1:100 or a 1 percent solution in water for fire extinguishment

(Continued)


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Durable Agents

• Are normally applied at 1½ to 2 percent for line construction; at 2 or 3 percent for structure protection

• Can be repeatedly rehydrated with a fine water mist to extend their protection for several days


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Summary

• Advances in foam technologies combined with a greater need for foam application have increased the use of foaming agents by fire departments throughout North America.

(Continued)


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Summary

• Regardless of the type of foam system used by a particular fire department, it is the responsibility of the driver/operator to deliver properly proportioned foam solution to the nozzle or nozzles applying the foam.

(Continued)


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Summary

• To fulfill this responsibility, driver/operators must be familiar with the type of foam system their department uses, along with its capabilities and limitations.

(Continued)


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Summary

• Driver/Operators must know how to introduce foam into the system, maintain its flow for as long as necessary, and troubleshoot any problems that develop while the system is in operation.

(Continued)


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Summary

• In addition, the driver/operator must know how to properly flush the system after use, and maintain the foam system in a state of constant readiness.


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Discussion Questions

1.Why have foam and durable agents increased in use in recent years?

2.Name the three ways in which foam extinguishes and/or prevents fire.

3.What are the four basic methods by which foam may be proportioned?

4.Name various ways in which foam is stored.

(Continued)


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Discussion Questions

5.Explain how to determine the application rate available from a nozzle.6.What are the three things that happen when AFFF is applied to a hydrocarbon fire?7.What are the three basic applications of high-expansion foams?8.Describe some reasons for failure to generate foam or for generating poor quality foam.

Documents

Pumping Apparatus Driver/Operator — Lesson 15 Pumping Apparatus Driver/Operator Handbook, 2 nd Edition Chapter 15 — Foam Equipment and Systems