Low Expansion Foam

1
Low Expansion Foam

• NFPA 11
• class B
• flammable liquids, FP lt 1000F
• combustible liquids FP gt 1000F
• forms blanket
• 2-D horizontal surface
• tank farms, airports etc.

2
Expansion Ratio

• Classification Range
• Low expansion up to 201
• Medium 201 to 1001
• High 2001 to 10001

3
Components of Foam

• Air
• within bubbles
• most of volume
• Concentrate
• to be mixed with water
• final concentration 3 or 6
• Water
• water concentrate solution

4
Types of Foam

• Protein
• older type
• no film
• from animal protein
• little in use now

5
Types of Foam

• Fluoroprotein
• better than protein
• forms film

6
Types of Foam

• Aqueous Film Forming Foam
• AFFF
• most common for fuels
• thin film
• not for alcohols

7
Types of Foam

• Alcohol Resistant
• also Alcohol type
• for small alcohols
• methanol, ethanol etc
• from membrane bewteen water and foam

8
Types of Foam

• Chemical
• chemically generated foam
• obsolete

9
Proportioning Methods

• To mix concentrate with water
• either 3 or 6 concentrate in water
• 3 mechanisms
• Venturi proportioner
• Pressure proportioner
• Balanced pressure proportioner
• skip details

10
Types of Systems

• Mobile
• fire dept. trucks
• Semi-Fixed
• permanent piping, foam makers
• mobile concentrate and pump

11
Types of Systems

• Fixed
• Subsurface injection
• Surface application
• seal protection for floating roofs
• dike protection

12
Sub-Surface Injection

• Fixed roof storage tank
• foam applied below surface
• floats to surface
• gentle, uniform application
• fluoroprotein foam
• has good fuel-shedding properties

13
Sub-Surface Injection-design

• 1. Calculate fuel surface area
• A ( ?)( r)2
• 2. Determine application rate (R) and discharge
  time (T)
• see 3.8

14
Sub-Surface Injection-design

• 3. Calculate discharge rate (D) and foam
  concentrate quantity (Q)
• D (A) x (R)
• Q (A) x (R) x (T) x ()
• 4. Determine the number of subsurface
  application outlets
• see 3.9

15
Sub-Surface Injection-design

• 5. Determine supplementary requirements
• number of hoses (see 3-10)
• discharge time (see 3-11)
• 6. Calculate supplementary discharge rate (Ds)
  and foam quantity (Qs)
• Ds (N) x (50 gpm)
• Qs (N) x (50 gpm) x (Ts) x ()

16
Sub-Surface Injection-design

• Total requirement for concentrate
• Qtotal Q Qs
• see example 3.1

17
Surface Application

• Fixed discharge units
• on rim of tank

18
Surface Injection-design

• 1. Calculate fuel surface area
• A ( ?)( r)2
• 2. Determine application rate (R) and discharge
  time (T)
• see 3.14
• note difference between types I and II

19
Surface Injection-design

• 3. Calculate discharge rate (D) and foam
  concentrate quantity (Q)
• D (A) x (R)
• Q (A) x (R) x (T) x ()
• 4. Determine the number of surface application
  outlets
• see 3.15

20
Surface Injection-design

• 5. Determine supplementary requirements
• number of hoses (see 3-10)
• discharge time (see 3-11)
• 6. Calculate supplementary discharge rate (Ds)
  and foam quantity (Qs)
• Ds (N) x (50 gpm)
• Qs (N) x (50 gpm) x (Ts) x ()

21
Surface Injection-design

• Total requirement for concentrate
• Qtotal Q Qs
• see example 3.2

22
Seal ProtectionFloating Roof Tanks

• No vapour space
• gap at edge of roof a problem
• seal spans gap

23
Floating Roof Tanks-design

• 1. Calculate fuel surface area
• A total roof area - unprotected roof area
• A ( ?)( r1)2 - ( ?)( r2)2
• 2. Determine application rate (R) and discharge
  time (T)
• R .30 gpm/ft2
• T 20 min.

24
Floating Roof Tanks-design

• 3. Calculate discharge rate (D) and foam
  concentrate quantity (Q)
• D (A) x (R)
• Q (A) x (R) x (T) x ()
• 4. Determine the spacing of outlets
• see text

25
Floating Roof Tanks-design

• 5. Determine number of discharge devices
• N C/S
• N number
• C circumference (? x diameter)
• S maximum spacing

26
Floating Roof Tanks-design

• 6. Determine supplementary requirements
• number of hoses (see 3-10)
• discharge time (see 3-11)
• 7. Calculate supplementary discharge rate (Ds)
  and foam quantity (Qs)
• Ds (N) x (50 gpm)
• Qs (N) x (50 gpm) x (Ts) x ()

27
Floating Roof Tanks-design

• Total requirement for concentrate
• Qtotal Q Qs
• see example 3.3

28
Dike Protection

• To contain tank farm

29
Dike Protection- Design

• 1. Calculate dike surface area
• A dike length x dike width
• 2. Determine application rate (R) and discharge
  time (T)
• R .10 gpm/ft2 fixed outlets
• R .16 gpm/ft2 monitors
• T 30 min., flamm. liquids
• T 20 min., comb. liquids

30
Dike Protection- Design

• 3. Calculate discharge rate (D) and foam
  concentrate quantity (Q)
• D (A) x (R)
• Q (A) x (R) x (T) x ()
• 4. Determine the number of discharge devices
• every 30 ft
• N (2L 2W)/30
• see 3.4

31
Aircraft Hangers

• omit

32
Truck Loading Rack
33
Truck Loading Rack

• Hazards

34
Truck Loading Rack

• Strategy

35
Truck Loading Rack

• Design