1. Low-Expansion Foam System Design
Unit 4
Low-Expansion Foam System Design

2. Standard for Low Expansion Foam
NFPA 11
Standard for Low Expansion Foam

3. Flammable or Combustible???
Which one is safer?
Flammable or Combustible???

4. 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

5. Combustible Liquids
Combustible liquid is defined as a liquid that has a flash point at or above 100ºF

6. 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

7. 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

8. 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

9. Expansion Ratio

10. 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

11. 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

12. The Components of Foam

13. Components of Foam Air Water Foam Concentrate
Contained within Foam bubbles
Water
Delivered at a specified density in GPM/SQ.FT
Foam Concentrate
Injected into the water stream at a specific percentage

14. 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”

15. Types of Foam

16. Types of Foam Protein Foam Fluoroprotein Foam (FFFP)
Aqueous Film-Forming Foam (AFFF)
Alcohol-resistant Foam
Chemical Foam

17. 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)

18. Protein Foam (cont.) Shorter shelf life
More frequent replacement compared to other types of Foam
May not maintain “floating” above the fuel

19. 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

20. Protein-based Foams(Summary)
Ranked by Effectiveness
Film-Forming Fluoroprotein Foam (FFFP)
Fluoroprotein Foam
Protein Foam

21. 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

22. 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

23. Chemical Foams
Depends on chemical reaction within the Foam Solution to create air bubbles (Foam)
Obsolete due to AFFF and FFFP

24. Proportioning Methods

25. 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

26. Types of Proportioners
Venturi /In-Line Proportioner
Pressure Proportioner
Balanced Pressure Proportioner

27. 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

28. 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

29. 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

30. Types of Foam Systems

31. Types of Foam Systems Mobile and Portable Apparatus Semi Fixed Systems
Fixed Foam Systems

32. 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

33. Semi Fixed Systems Permanent Foam makers and outlets
Spaced as needed or required
Piped to a connection
Located a safe distance from hazard
Semi Fixed Piping used in conjunction with mobile or portable foam equipment
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

34. 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.

35. 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

36. Subsurface Injection – Low Expansion Foam Systems

37. 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

38. 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

39. Subsurface Injection Foam Systems (cont.)
High back-pressure foam makers required on both types of subsurface injection types

40. 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

41. 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)

42. 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)

43. 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 (%)

44. Design Methods for Subsurface Injection Foam Systems (cont.)
Step #7-Determine total discharge rate
Dt=D+Ds
Step #8-Determine total foam concentrate quantity
Qt=Q+Qs
Step #9-Hydraulically calculate the system

45. Break

46. Surface Application - Low Expansion Foam Systems

47. 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

48. 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.

49. 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

50. 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

51. Seal Protection for Floating Roof Tanks

52. 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

53. 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

54. 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

55. Dike Protection Low Expansion Foam Systems

56. 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

57. 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

58. 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

59. 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)

60. Dike Protection Low Expansion Foam Systems (cont.)
Step #3
Calculate foam discharge rate
Calculate concentrate quantity
Step #4
Determine # of foam discharge devices required
N=(2L+2W)/30
See page 11-19, NFPA 11

61. Low Expansion Foam Systems for Aircraft Hangars

62. 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

63. 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.

64. 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)
Aspirated foam water nozzles (Air) vs. Non-aspirated sprinklers
Underwing protection (WOM)
Water Oscillating monitors
Supplementary Hose protection

65. Truck Loading Rack Protection

66. 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

67. 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

68. Hazards Associated with Truck Loading Racks (cont.)
Numerous other ignition sources:
Smoking
Electrostatic charges
Truck Battery

69. 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.

70. 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

71. Summary Use Expansion ratio – Low Expansion Components of Foam
Protection of Flammable or Combustible liquids (Two-dimensional)
Expansion ratio – Low Expansion
Up to 20:1
Components of Foam
Foam concentrate, Water, Air
Types of Foam
Protein, Fluoroprotein, AFFF, Alcohol-resistant, and Chemical

72. Summary (cont.) Applications Subsurface injection Surface injection
Seal protection
Dike protection
Aircraft Hangars
Truck loading racks

73. Questions???