Firefighting Foam

Foam Equipment and Systems

UEF Foam is Effective on Combustible Metals

Class D fires involve combustible metals such as aluminum,

magnesium, titanium, sodium, and potassium.

Fires involving combustible metals require specialized techniques and extinguishing agents that have been developed to deal with these types of fires, such as UEF Foam

A Class D extinguisher or a Class D powder is also

recommended for fires involving combustible metals.

Foam is Effective on Pressurized Gases

Foam is effective on fires involving pressurized gases. These materials are usually stored as liquids, but are normally vapor at ambient temperature.

To be effective, foam must set up as a two-dimensional blanket on top of a pooled liquid.

Examples of pressurized gases include:

• propane,

• butane,

• vinyl chloride, and

• butadiene.

How Foam Works

Foam can control and extinguish flammable liquid fires in a number of

ways. Foam can:

• exclude oxygen from the fuel vapors and thus prevent a flammable

mixture,

• cool the fuel surface with the water content of the foam,

• prevent the release of flammable vapors from the fuel surface, and

• emulsify the fuel (some environmental foams).

Foam is Effective on Three-Dimensional Fires

A three-dimensional fire is a liquid-fuel fire in which the fuel is being discharged from an elevated or pressurized source, creating a pool of fuel on a lower surface.

UEF Foam is effective at controlling three-dimensional flowing fires.

UEF Foam is not Effective on Class C Electrical Fires

Class C fires involve energized electrical equipment; water conducts electricity.

Since foam contains 99 percent water, it is not safe for

use on this type of fire. In some cases, foam concentrate is even more conductive than water.

Class C fires can be extinguished using nonconductive extinguishing agents such as a dry chemical, carbon dioxide (CO2), or halon.

The safest procedure for this type of situation is to de-energize the equipment if possible and treat it as a Class A or Class B fire

UEF Foam is Effective On:

UEF Foam is effective on all types of fires. It is important to know the type of fire and the fuel involved. UEF Foam is effective on:

• Class C fires,

• three-dimensional fires,

• pressurized gases, and

• Class D fires.

Proportioning Rates

Foam equipment and Systems

Firefighting Foam

BFD Proportioning Rates

Expressed as a percentage

0.5% = 0.5 unit of concentrate to 99.5 units of water

Foam Equipment and Systems

What is Foam Effective On?

Foam is effective at suppressing vapors and extinguishing Class B fires.

Class B fires are defined as fires involving flammable or

combustible liquids.

For the purposes of this discussion, Class B products are divided into two categories: hydrocarbons and polar

solvents.

Finished Foam - Completed product after the foam solution reaches the nozzle and air is introduced into the solution (aeration).

Foam Eductors - Type of foam proportioner used for mixing foam concentrate in proper proportions with stream of water to produce foam solution.

Why Use Foam?

Many extinguishing agents are effective on flammable liquids.

However, foam is the only agent capable of suppressing vapors and

providing visible proof of security. Reasons to use foam include:

• A foam blanket on an unignited spill can prevent a fire.

• The suppression of vapors prevents them from finding an ignition

source.

• Foam can provide post-fire security by protecting the hazard until it

can be secured or removed.

• Foam can provide protection from flammable liquids for fire and

rescue personnel during emergency operations.

Foam Equipment and Systems

Fall 2014

Hydrocarbons

Most hydrocarbons are byproducts of crude oil or have been extracted from vegetable fiber.

Hydrocarbons have a specific gravity of less than

1.0 and therefore float on water.

Examples of hydrocarbon fuels include:

• gasoline,

• diesel,

• jet propellant (JP4),

• heptane,

• kerosene, and

• naptha.

Foam Equipment and Systems

Foam Tetrahedron

Foams used today are primarily of the mechanical type. This means

that before being used, they must be proportioned (mixed with water)

and aerated (mixed with air).

Four elements are necessary to produce a quality foam blanket. These

elements include:

• foam concentrate,

• water,

• air, and

• aeration (mechanical agitation).

Foam Equipment and Systems

Polar Solvents

Polar solvents are products of distillation or products that have been

synthetically produced. Polar solvent fuels are miscible, that is they

will mix with water. Polar fuels have a varying attraction for water. For

example, acetone has a stronger affinity for water than does rubbing

alcohol.

Polar solvent fuels are usually destructive to foams designed for use on

hydrocarbons. Specially formulated foams have been developed for use

on polar solvents.

Some examples of polar solvent fuels include:

• ketones,

• esters,

• alcohol including ethyl-alcohol (ethanol),

• amine,

• methyl tertiary-butyl ether (MTBE), and

• acetone.

UEF- Novacool UEF Foam, a multi-purpose fire extinguishing foam, replaces aqueous film-forming foams (AFFF) and ozone-depleting halon gases, which release both toxic hydrofluoric acid and fluorocarbons into the environment during use.

Air-Aspirating Foam Nozzle- Foam nozzle designed to provide the aeration required to make highest quality of foam possible.

Foam Proportioning Systems

A number of ways exist to proportion foam.

These include:

• line eductors,

• self-educting nozzles,

• pressure systems, and

• pump proportioning systems.

What is Foam?

As defined in National Fire Protection Association (NFPA) 11,

low-expansion foam is:

“…an aggregate of air-filled bubbles formed from aqueous solutions

which is lower in density than flammable liquids. It is used principally

to form a cohesive floating blanket on flammable and combustible

liquids, and prevents or extinguishes fire by excluding air and cooling

the fuel. It also prevents reignition by suppressing formation of

flammable vapors. It has the property of adhering to surfaces, which

provides a degree of exposure protection from adjacent fires.”

In-Line Eductors

In-line eductors are some of the least expensive and simplest pieces of proportioning equipment available

For this reason, they are perhaps the most common type of foam proportioner used in the fire service.

Some advantages include:

• low cost,

• minimal maintenance, and

• simple operation.

Eductors

Eductors use the venturi principle to pull foam into the water stream.

The flow of water past the venturi opening creates a vacuum that draws the concentrate through the metering valve.

The metering valve controls the amount of concentrate allowed to flow into the water stream.

The ball check valve prevents water from flowing back into the pickup tube and the concentrate container.

Major elements of the eductor setup include foam concentrate supply, water supply, eductor arrangement, metering valve, pickup tube, and foam solution discharge.

Two common types of eductors are in-line eductors and bypass

eductors.

Air Aspirating Nozzles

Air aspirating nozzles are foam generating nozzles that mix air and atmospheric pressure with foam solution .

These nozzles produce an expansion ratio of between 8:1 and 10:1 and produce a good-quality, low-expansion foam.

Non-Air Aspirating Nozzles

A disadvantage of aspirating and non-air aspirating nozzles is that you must have additional equipment in order to generate foam. In addition,the gallonage setting on the nozzle must match the set flow for the eductor. It is important to understand the benefits of both types of nozzles in order to select the most appropriate one.

Application Techniques

Proper application is critical for foam. The key to foam application is to apply the foam as gently as possible to minimize agitation of the fuel and creation of additional vapors.

The most important thing to remember is to never plunge the foam directly into the fuel. This will agitate the fuel and create additional vapors.

Bounce-Off

The bounce-off method is effective if there is an object in or behind the spill area.

The foam stream can be directed at the object, which will

break the force of the stream, allowing the foam to gently flow onto the fuel surface.

Bank-In

When no obstacles exist to bounce the foam off, firefighters should

attempt to roll the foam onto the fire. By hitting the ground in front of

the fire, the foam will pile up and roll into the spill area.

This technique is particularly effective with non-air aspirating fog

nozzles. The mechanical agitation of the foam hitting the ground will

help to aerate the foam.

Rain-Down

An alternative application technique is the rain-down method.

The nozzle is elevated and the foam is allowed to fall over the spill as gently as possible.

Warning! Never plunge a stream of foam directly into fuel!