Pumping Apparatus Driver Operator (1st Edition)
Chapter 15 - Foam Equipment & Systems
Test Review
NOTICE: No notes have been taken from "steps" in this chapter.
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Chemical foams are those produced as a result of the reaction between two chemicals and are considered
obsolete.

Mechanical foams are those which must be proportioned (mixed with water) and aerated (mixed with air)
before use.

Foam concentrate is raw foam liquid as it rests in a storage container before introduction of air and water.

Foam proportioners are devices that introduce foam concentrate into the water stream to make foam solution.

Foam solution is the mixture of foam concentrate and water before the introduction of air.

Foam (finished foam) is the result of foam concentrate being mixed with water and air introduced into the
solution.

Class B fuels are divided into hydrocarbons and polar solvents.

Hydrocarbons such as crude/fuel oil, benzene, gasoline, naptha, jet fuel, and kerosene are petroleum products
and have characteristics that make them float on water.

Polar solvents such as alcohol, acetone, lacquer thinner, ketones, and esters are flammable liquids and have
characteristics that make them miscible (able to mix) with water.

Class B foams designed "solely" for hydrocarbon fires will NOT extinguish a polar solvent fire regardless of
concentration used.

Foam extinguishes and/or prevents fire by creating a barrier between the fuel and the fire (separating), by
lowering the temperature of the fuel and adjacent surfaces (cooling), and by preventing the release of
flammable vapors with a foam blanket (suppressing/smothering).

Proportioning is the mixing of water with foam concentrate to form a foam solution.

The percentage at which Class A foams are used may be adjusted to fit the situation (higher %=thick foam,
lower %=thin, deeper penetrating foam).

Foam is proportioned by induction, injection, batch mixing, or premixing.

Induction of foam is accomplished by pressure energy passing through a restricted orifice to "educt" foam into
the stream.

The injection method of proportioning foam involves using an external pump or head pressure to force foam
concentrate into a stream of water at a specified ratio.

Batch mixing is the simplest method of mixing foam concentrate with water and is accomplished by adding
foam concentrate directly into a tank of water.

Batch mixing is commonly used with Class A foams but should be used only as a last resort for Class B foams.

The premixing method of proportioning foam involves premeasuring portions of foam concentrate and water
into a container and is commonly used for portable/wheeled extinguishers, skid-mounted agent units, and
vehicle-mounted tank systems.

Premixed foam solutions are commonly discharged from tanks with a compressed inert gas or air and are
limited to a one-time application.

Foam concentrate may be stored in pails, barrels, and in apparatus tanks.

Alcohol resistant foam concentrate, and most other foams, must be stored in air tight containers to prevent a
skin from forming on top of the liquid.

Foam concentrate stored in barrels is typically transferred to smaller pails as needed.

Class A foam is effective for fires in structures, wildlands, coal mines, tire storage, and other similar deepseated fuels.

Class A foam is made of special hydrocarbon surfactants which reduce the surface tensio of the water allowing
better penetration in the fuel.

Class A foams may be used with fog nozzles, aerating nozzles, high/medium expansion devices, and almost
any nozzle, including solid stream nozzles when CAFS systems are used.

As the expansion ratio of a foam increases, the drain time increases as well.

Application rate for foam refers to the amount of foam solution that must be applied to a fire, per minute, per
square foot of fire.

Class A foam produced as a wet foam has a high water content (low foam content) and fast drainage time and
is used when maximum penetration is needed.

Class A foam produced as a dry foam has a high foam content (low water content) and slow drainage time and
is used when the foam is needed to cling to a surface for a prolonged period such as with exposure protection.

Class A foam produced as a medium foam has an equal amount of water and foam concentrate to allow a
balance of penetration and clinging ability.

As foam breaks down (also called drain time), it releases water onto the fuel.

Class B foams are used to extinguish fire or suppress vapors for liquids that are flammable or combustible.

AFFF and FFFP Class B foams may be applied using standard fog nozzles.

Air-aspirating foam nozzles may be used with all types of Class B foams.

Protein foams are derived from animal proteins, while synthetic foam is made from a mixture of
fluorosurfactants.

Foams stored in cool areas will have a greater longevity than those stored in warm areas.

Foam concentrates from different manufacturers should not be mixed together unless they are Mil-Spec foams
or if foams of the same type but from different manufactures will be mixed and used immediately.

Protein-based foams are generally safer for the environment.

Foam expansion is the increase in volume of the foam solution when it is aerated.

The degree of expansion of foam depends on the type of foam used, accurate proportioning, quality of foam
concentrate, and method of aspiration.

The rate of application for foam depends on the foam type used, whether the fuel is on fire, the type of fuel
involved, and whether the fuel is spilled on in a container (including tank condition).

Unignited spills generally require the minimum application rate for the fuel since radiant heat, open flame, and
thermal drafts will not affect the application.

Regular protein foams are derived from protein sources such as hoof, horn, or feather meal and is then
hydrolyzed in the presence of lime and converted to protein hydrolysate that is neutralized.

Regular protein foam may have foam stabilizers, corrosion inhibitors, antimicrobial agents, and/or freezing
agents added.

Regular protein foam has very good heat stability and resists burnback.

Fluoroprotein foam is derived from protein foam concentrates with fluorochemical surfactants added (similar
to AFFF surfactants but at a lower %).

Fluoroprotein foams provide a strong blanket for long-term vapor suppression and may be made alcohol
resistant by adding ammonia salts suspended in organic solvents.

FFFP foam has benefits of fast fire knockdown of AFFF foam and the long-lasting heat resistance of
fluoroprotein foam.

AFFF is a synthetic foam consisting of fluorochemical and hydrocarbon surfactants combined with high
boiling point solvents and water.

The surface tension of fluorochemical surfactants is less than that of hydrocarbons and allows it to spread an
aqueous film over the fuel.

AFFF has the ability to "heal" when the seal of the film is broken.

Alcohol-type AFFF forms a membrane instead of a film.

High-expansion foams have a detergent base and low water content which minimizes water damage.

High expansion foams are used in concealed spaces, fire extinguishing systems and Class A fire applications.

Foam proportioners usually act by induction (using venturi principle) or by injection.

Portable foam proportioners include in-line foam eductors, foam nozzle eductors, and self-educting master
stream foam nozzles.

In-line eductors use the venturi principle to "draft" foam concentrate into the water stream.

The venturi principle is the creation of a low-pressure are by use of a restricted orifice in a device which
creates a suction effect at the low pressure point.

In-line eductors, not nozzles, must control the flow when educting foam.

Foam nozzle eductors use the same principle as in-line eductors, however, the foam concentrate must be
present at the nozzle, making it hard to move around.

Types of apparatus-mounted foam proportioning systems inlclude installed in-line eductors, around-the-pump
proportioners, bypass-type balanced pressure proportioners, variable-flow variable-rate direct injection
systems, variable-flow demand-type balanced pressure proportioners, and batch-mixing.

Installed in-line eductors on apparatus require the same precautions regarding hose length, nozzle/eductor
flows, and inlet pressures, as portable in-line eductors.

Around-the-pump proportioners (most common) consist of a small return (bypass) water line connected from
the discharge side of the pump back to the intake of the pump.

Older around-the-pump proportioners cannot take advantage of incoming pressure and must usually be gated
down to a very low psi.

Bypass-type balanced pressure porportioners are very accurate and are commonly used on ARFF and refinery
vehicles.

Bypass-type balanced pressure proportioners allow water to be pumped from a discharge while discharging
foam from another.

Variable-flow, variable-rate direct injection systems use hydraulic or electric power to inject foam concentrate
which is controlled by monitoring water flow and may be found in high-energy foam systems.

Variable-flow demand-type balanced pressure porportioners consists of a pump (electric or hydraulic) that
pumps foam concentrate to an eductor where it is drafted into the stream.

Batch mixing is generally only used with regular AFFF and Class A foam concentrates.

Batch mixing may cause cavitation of the pump at a later time when water tanks are refilled if tanks are not
cleaned after foam use.

The first high energy foam systems were termed Water Expansion Systems (WES) and Water Expansion
Pumping Systems (WEPS) and used air cylinders for the compressed air.

Compressed Air Foam Systems (CAFS) use a direct-injection foam proportioning system on the discharge side
of the pump that is aerated by compressed air which comes from a rotary air compressor on the apparatus.

Advantages of CAFS systems include considerably longer reach than other foam systems, foam produced
contains uniformly sized (durable) small air bubbles, foam adheres to surfaces and resists heat longer,
hoselines are lighter to handle, and allows effective attack from a greater distance.

Apparatus with CAFS systems may flow water and foam at the same time.

In low-energy foam systems, aeration of foam occurs at the foam nozzle.

Solid bore nozzles may be used with Class A and CAFS foams systems.

Fog nozzles cannot be used with protein or fluoroprotein foams.

Fog nozzles may be used with alcohol-resistant AFFF on hydrocarbon fires but NOT on polar solvent fires
(insufficient aspiration).

Air-aspirating foam nozzles may be used with protein, fluoroprotein, and Class A foams.

Air-aspirating foam nozzles consist of a back that is open to airflow and the end of the nozzle contains screens
to produce a moderate-expansion foam.

Mechanical blower generators are similar to smoke ejectors and produce a very high-expansion foam with high
air content.

Reasons for failure to produce foam include, failure to match eductor and nozzle flow, air leaks at fittings,
improper cleaning, partially closed nozzles, too long a hose lay on the discharge side of the eductor, kinked
hose, nozzle too far above eductor (elevation pressure), and mixing different types of foam concentrate
together (too viscous).

The roll-on method of foam application consists of directing the foam stream near the front edge of the liquid
and allowing the foam to "roll" over the liquid.

The bank-down method of foam application consists of "banking" the foam stream off a stationary object down
onto the surface of the fuel.

The rain-down method of foam application is used to allow foam to gently "rain" down onto the surface of the
fuel.