Unit 4
Low-Expansion Foam System
Design
NFPA 11
Standard for Low Expansion
Foam
Which one is safer?
Flammable or Combustible???
Flammable Liquids


Flammable liquid is defined as a liquid that
has a flash point below 100ºF and having
a vapor pressure not exceeding 40 psi
What is flash point?


Lower Flammable Limit
What is vapor pressure?

Closed container, vapor-air mixture above the
liquid
Combustible Liquids

Combustible liquid is defined as a liquid
that has a flash point at or above 100ºF
Low-Expansion Foam



“Low-expansion foam systems are used
when a blanket of foam is needed to float
on the horizontal surface of a flammable
or combustible liquid.”
Limited vertical surface protection
Use when Coating and O2 Displacement
are the preferred method of
extinguishment
Low-Expansion Foam (cont.)

Coating



Separates the fuel from the flame
Blocks admission of air to the combustion
process (i.e. oxygen dilution/separation of the
fire)
Cools the surface of the fuel
Low-Expansion Foam (cont.)


Low-Expansion foam is an appropriate
substitute for water when water is heavier
than the Flammable/Combustible liquid
being protected.
Specific gravity
Expansion Ratio
Expansion Ratio

Low Expansion Foam
 Up to 20:1 Typically 8:1

Medium Expansion Foam
 20:1 to 200:1 Typically 100:1
High Expansion Foam
 200:1 to 1000:1 Typically 500:1

Expansion Ratio (cont.)


The expansion ratio of foam is computed
by measuring the volume of the foam
produced after water and air are added
and comparing that volume to the original
volume of foam concentrate used
Low-Expansion Foam = up to 20:1 of the
hazard
The Components of Foam
Components of Foam

Air


Water


Contained within Foam bubbles
Delivered at a specified density in
GPM/SQ.FT
Foam Concentrate

Injected into the water stream at a specific
percentage
Components of Foam (cont.)

Foam concentrate is usually stored in drums or
barrels




1st - the Foam Concentrate is mixed with water to
make a Foam Solution
2nd - the Foam Solution flows through the piping
system to the hazard location
3rd - the Foam Solution is mixed with air (disch.
devices) at the specified rate to make FOAM
“It’s like blowing bubbles”
Types of Foam
Types of Foam





Protein Foam
Fluoroprotein Foam (FFFP)
Aqueous Film-Forming Foam (AFFF)
Alcohol-resistant Foam
Chemical Foam
Protein Foam



Expansion ratio between 8:1 and 10:1
Protein-based animal additives (hooves,
feathers) Hmm, Hmm, Good!…
Can be effective on hydrocarbon fires, but
absorbs fuel and tends to fail, no film

What does hydrocarbon mean?

Organic Compounds that contain only carbon and
hydrogen (i.e. Natural Gas, Petroleum, Coal, etc)
Protein Foam (cont.)



Shorter shelf life
More frequent replacement compared to
other types of Foam
May not maintain “floating” above the fuel
Fluoroprotein Foam


Protein Foam
Contains fluoroprotein additives


Less absorption of fuel
Film-Forming fluoroprotein (FFFP)


More effective than regular Fluoroprotein
Produces a film barrier between the foam and
the fuel
Protein-based Foams(Summary)

Ranked by Effectiveness



Film-Forming Fluoroprotein Foam (FFFP)
Fluoroprotein Foam
Protein Foam
Aqueous Film-Forming Foam
(AFFF)


Synthetic Foam
Recommended for flammable liquids in
storage tanks



Thin aqueous film that separates the foam
from the fuel
Readily available
Foam of choice for many applications
including Aircraft Hangars protection
Alcohol-resistant Foam



Used for the protection of alcohol-based
flammable liquid fires
Effective because the alcohol in the
flammable liquid does not collapse the
foam bubbles (water absorption) like other
foams
Forms a polymeric membrane between
the foam and the fuel
Chemical Foams


Depends on chemical reaction within the
Foam Solution to create air bubbles
(Foam)
Obsolete due to AFFF and FFFP
Proportioning Methods
Proportioning Methods

Foam Concentrate must be mixed with
water by a Foam Proportioner


Ensures proper expansion Ratio and proper
proportions
Example 6% Foam Concentrate

6% Foam Concentrate, 94% Water
Types of Proportioners



Venturi /In-Line Proportioner
Pressure Proportioner
Balanced Pressure Proportioner
Venturi /In-Line Proportioner


Water moves past the metering orifice,
thus creating negative pressure at the
orifice that forces (pulls) Foam
Concentrate into the water stream of the
Venturi
Foam is dependent on metering orifice
size, but is typically 1%, 3%, or 6% mix
Pressure Proportioner

Draws a portion of incoming water stream into
the tank holding the Foam Concentrate



This is done in an effort to pressurize the tank where
the foam concentrate is stored
Collapsible bladder holds the Foam Concentrate
Water increases the amount of pressure on the
bladder tank, thus forcing foam concentrate out
of the bladder and towards the proportioner
Balanced Pressure Proportioner



Uses an atmospheric foam concentrate tank
Uses a pump to pressurize the concentrate and
force it toward the proportioner
A proportioner that balances the pumped
concentrate pressure to the water supply
pressure, mixing the two at the correct ratio
Types of Foam Systems
Types of Foam Systems



Mobile and Portable Apparatus
Semi Fixed Systems
Fixed Foam Systems
Mobile and Portable Apparatus

Fire Departments




Hand (portable)
F.D. Truck
Wheeled Platform (Mobile)
Selection of Foam or Foam Equipment
should match the expected flammable or
combustible liquid
Semi Fixed Systems

Permanent Foam makers and outlets


Spaced as needed or required
Piped to a connection


Semi Fixed Piping used in conjunction with
mobile or portable foam equipment


Located a safe distance from hazard
Mobile or portable foam equipment should be able to
serve multiple semi fixed piping installations
Detection system, continuously attended central
station, on-site fire brigade is recommended
Fixed Foam Systems

This course is focused on Fixed Foam
Systems




Automatic
Self-contained
No manual intervention
Specifically fixed storage tank foam F.P.
and fixed aircraft hangar F.P.
Storage Tank foam fire protection

Four types of protection systems we will
discuss in FET-222




Subsurface injection
Surface application
Seal protection for floating roof tanks
Dike protection
Subsurface Injection – Low
Expansion Foam Systems
Subsurface Injection Foam
Systems

Storage tank w/fixed permanent roof


Prevents the collection of rainwater above or
below flammable/combustible liquid
Foam is applied below the surface of the
liquid, and floats to the top of the fuel
surface
Subsurface Injection Foam
Systems

#1 Dedicated foam line




Piping and nozzles at bottom of tank with nozzles in
the liquid, dedicated solely to foam injection
Nozzle spacing provides uniform disbursement of
foam to surface of the liquid (more gentle and uniform
than surface application of foam)
Not practical for existing tanks
#2 Injection into product (liquid) line


Tapped directly into the tank product line
Practical for existing tanks
Subsurface Injection Foam
Systems (cont.)

High back-pressure foam makers required
on both types of subsurface injection types
Design Methods for Subsurface
Injection Foam Systems

Step #1-Calculate fuel surface area



The circular area of the exposed fuel at the
upper level of the tank
Area=(pi)(r)^2
Step #2-Determine application rate (R)
and discharge time (T)

See Figure 3-8
Design Methods for Subsurface
Injection Foam Systems (cont.)

Step #3-Calculate minimum foam
discharge rate





Foam Discharge rate
Dgpm=(Area) (Rate)
D=foam discharge rate (gpm)
A=tank surface area (Step #1)
R=application rate (See Figure 3-8)
Design Methods for Subsurface
Injection Foam Systems (cont.)

Step #4-Calculate foam concentrate quantity






Foam Concentrate Quantity
Q=(A)(R)(T)(%)
Q=primary foam concentrate quantity (gal)
A=tank surface area (Step #1)
R=application rate (See Figure 3-8)
%=concentrate percentage for foam selected

1%(0.01), 3%(0.03), (6%(0.06)
Design Methods for Subsurface
Injection Foam Systems (cont.)

Step #5-Determine the number of subsurface
foam application outlets


See Figure 3-9
Step #6-Determine supplementary protection
requirements

See Figure 3-10


# of addl. hose streams x 50gpm
See Figure 3-11

(# of addl. hose streams) x (50gpm) x (Operating Time) x (%)
Design Methods for Subsurface
Injection Foam Systems (cont.)

Step #7-Determine total discharge rate


Step #8-Determine total foam concentrate
quantity


Dt=D+Ds
Qt=Q+Qs
Step #9-Hydraulically calculate the system
Break
Surface Application - Low
Expansion Foam Systems
Surface Application Low
Expansion Foam Systems

Surface application discharge devices are
designed to roll a thin blanket of foam over
the surface area of the fuel with fixed
discharge outlets permanently located
above the fuel surface


See Figures 3-12, 13A, 13B in textbook
There are two types of discharge devices
Surface Application Low
Expansion Foam Systems (cont.)

Discharge devices

Type I Outlet Discharge Devices

Designed to deliver foam onto the liquid surface in a very
gentle fashion


Two types
 Porous Tubes – tube overcomes diaphragm pressure and
drops into tank from the Foam Chamber
 Foam Trough – Chute securely attached to the inside of
the tank, “like pouring concrete”
These outlets are designed to extinguish fire with a
minimum of Foam-producing materials.
Surface Application Low
Expansion Foam Systems (cont.)


Discharge devices (cont.)
Type I Outlet Discharge Devices

Considered obsolete because nearly all
currently manufactured foams are suitable for
use with Type II discharge outlets
Surface Application Low
Expansion Foam Systems (cont.)

Discharge devices (cont.)

Type II Outlet Discharge device
Designed to deliver foam (less gently than Type I
Outlets) onto the liquid surface, but to lessen
submergence of the foam and agitation of the
surface
 Commonly called Foam Chambers


Most Foam Chambers are of a Type II discharge outlet
design, since they are normally suitable for use with
modern foams
Seal Protection for
Floating Roof Tanks
Seal Protection for
Floating Roof Tanks

What is a floating roof?

A floating roof floats on the surface of the flammable
liquid, rising and falling as the liquid is added to or
removed from the tank


The floating roof allows no space between the bottom of the
roof and the surface of the liquid, no vapor buildup
What is seal protection?

A system that involves building a dam around the
perimeter of a floating roof and filling the seal area
with low expansion foam
Seal Protection for
Floating Roof Tanks (cont.)

What part of the floating tank gets Foam
protection?

The space between the edge of the floating roof and
the perimeter of the tank



The (weather) seal that covers this area requires Foam
Protection
This involves building a “Dam” of Foam around the perimeter
of the floating roof and the tank
Some cases require Foam Distribution Piping to
penetrate the (weather) seal

Seal must be able to hold the Foam
Seal Protection for
Floating Roof Tanks (cont.)

Spacing of Discharge devices

Top of Seal protection (foam dam)



Foam dam height 12 inches, Outlets-40ft max
Foam dam height 24 inches, Outlets-80ft max
Protection below Seal (pipe penetration of seal)



Mechanical Shoe seal, Outlets-130ft max
Tube seal, Outlets-60ft max typically
Foam dam required when 6 in or less between top of roof
and tube
Dike Protection Low
Expansion Foam Systems
Dike Protection Low Expansion
Foam Systems



Containment dike for tank farms will often
have a supplemental Low Expansion
Foam System
The dike area is flooded with Foam that
will float on top of any flammable liquid
that may have been spilled within the
containment area
See Figure 3-19, Plan view
Dike Protection Low Expansion
Foam Systems (cont.)

A dike protection system may also be
recommended as supplemental protection



fixed cone roof (FCR)
floating roof tank (FRT) dike area
Systems can be portable or mobile under
certain guidelines
Dike Protection Low Expansion
Foam Systems (cont.)

Design Procedure

Calculate dike area




Note: If a tank is installed with its bottom mounted to the floor
of the dike, then the surface area of the tank may be
deducted from the total dike area
Determine application rate and discharge times per
NFPA 11
Calculate foam discharge rate and concentrate
quantity
Determine the number of foam discharge devices
required
Dike Protection Low Expansion
Foam Systems (cont.)


Design Methodology
Step #1


Calculate dike area
Step #2


Determine application rate(outlets & monitors)
Determine discharge times(outlets &
monitors)
Dike Protection Low Expansion
Foam Systems (cont.)

Step #3



Step #4


Calculate foam discharge rate
Calculate concentrate quantity
Determine # of foam discharge devices
required
N=(2L+2W)/30

See page 11-19, NFPA 11
Low Expansion Foam Systems
for Aircraft Hangars
Low Expansion Foam Systems
for Aircraft Hangars


Aircraft that are stored or serviced in an
aircraft hangar contain large amounts of
flammable fuel
Servicing the aircraft offers numerous
opportunities for the spilled fuel to ignite
Low Expansion Foam Systems
for Aircraft Hangars (cont.)

NFPA 409


Standard on Aircraft Hangars
Low expansion foam systems not only
smother flammable liquid pool fires on the
floor, but effectively coat the aircraft skin
with an effective exposure protection
barrier.
Low Expansion Foam Systems
for Aircraft Hangars (cont.)

Hangars are classified by three groups


Group I, Group II and Group III
Aircraft hangar fire protection design can consist
of low expansion foam systems

Ceiling protection (coats skin)


Underwing protection (WOM)


Aspirated foam water nozzles (Air) vs. Non-aspirated
sprinklers
Water Oscillating monitors
Supplementary Hose protection
Truck Loading Rack Protection
Truck Loading Rack Protection





NFPA 11- Standard for Low Expansion Foam
NFPA 16- Standard for the Installation of Deluge
Foam-Water Sprinkler and Foam-Water Spray
Systems
NFPA 16A- Standard for the Installation of
Closed-Head Foam-Water Sprinkler Systems
The point where flammable and combustible
liquids are pumped from storage tanks to a truck
See Figure 3-25, Page 69
Hazards Associated with Truck
Loading Racks




Most dangerous portion of the
manufacture of a flammable or
combustible liquid
Pumping the liquid involves Pressurization
of the hose line that transmits the liquid
Pump could fail
Hose could burst or become dislodged
from the connection to the truck
Hazards Associated with Truck
Loading Racks (cont.)




Numerous other ignition sources:
Smoking
Electrostatic charges
Truck Battery
Fire Protection Strategy for Truck
Loading Racks

Roof protection


Foam-water sprinklers or Foam-water spray nozzles
at the roof of the truck loading rack. Typically, at a
maximum of 100 sq.ft.(10’ x 10’) i.e. Extra Hazard
Goal of Roof Protection

To provide complete protection of the drainage area

The drainage area is the curbed area designed contain
spilled flammable or combustible liquids as it flows towards
floor drains. Note: Drainage area may not always coincide
with the Roof area. The hazard area is always the drainage
area, not the roof area.
Fire Protection Strategy for Truck
Loading Racks




See Figure 3-28
Additional nozzles are aimed directly at
the point of connection of the hose to the
truck
Additional nozzles are aimed beneath the
truck to enable the sweeping of liquid from
beneath the truck
See Figure 3-29
Summary

Use


Expansion ratio – Low Expansion


Up to 20:1
Components of Foam


Protection of Flammable or Combustible liquids (Twodimensional)
Foam concentrate, Water, Air
Types of Foam

Protein, Fluoroprotein, AFFF, Alcohol-resistant, and
Chemical
Summary (cont.)

Applications






Subsurface injection
Surface injection
Seal protection
Dike protection
Aircraft Hangars
Truck loading racks
Questions???