1. Medium- and High-expansion Foam System Design
Chapter 5
Page 166

2. Objectives
Determine appropriate situations for the use of low-expansion, medium-expansion, and high-expansion foam
Discuss the differences in the application and the methods of extinguishment for low- expansion, medium-expansion, and high- expansion foam

3. Objectives
Perform a calculation of a high-expansion foam system to determine the rate of discharge and number of high-expansion foam generators required
Lay out a high-expansion foam system, showing foam fences, generator locations, and piping locations

4. Local Application Medium- And High-Expansion Foam Systems
The majority of medium- and high-expansion foam systems are total flooding systems
Foam fills a volume to a specified height
For local application systems, NFPA 11 specifies minimum design criteria

5. Electrical Clearances For Medium- And High-Expansion Foam Systems
Because foam contains water, application of foam could transmit electricity
Designer must prevent this
The proximity of foam components to live electrical components must be coordinated

6. Electrical Clearances For Medium- And High-Expansion Foam Systems
For altitudes greater than 3300 feet (1000 m), the clearance is required to be increased at the rate of 1% for each 330 feet (100 m) of altitude above 3300 feet (1000 m)
See Table 5-1, Page 168 for electrical clearances

7. Medium-Expansion Foam
The required depth of medium-expansion foam over a protected hazard shall vary as a function of expansion ratio
The depth of medium-expansion foam shall be determined by tests
The rate of discharge of medium-expansion foam shall be determined by tests
The quantity of medium-expansion foam shall be determined by tests

8. Applications For High-Expansion Foam Systems
For hazards in which smothering of a three- dimensional fire or oxygen deprivation of a three-dimensional fire is primary objective
A three-dimensional object requiring high- expansion foam is one that requires foam to be totally flooded and completely covered to an elevation above the highest level of the object requiring protection

9. Applications For High-Expansion Foam Systems
Figure 5-2. Sectional view of a flammable liquid pump protected by a high-expansion foam system

10. Other Applications For High-Expansion Foam Suppression Systems
High-expansion foam systems
Primarily for extinguishment of flammable liquid fires
Should be specified with some degree of caution with respect to personnel safety

11. High-Expansion Foam Systems For Robotic Flammable Liquid Rack Storage
First consideration: personnel
Second consideration: fire protection engineer must determine and solve the performance objectives of the system

12. High-Expansion Foam Systems For Aircraft Hangars
NFPA 409 permits high-expansion foam systems to be specified in lieu of the low- expansion foam systems
Overhead AFFF low-expansion foam systems protect flammable liquid spill fire hazards in aircraft hangars
High-expansion foam may be an answer to EPA concerns about low-expansion foam

13. High-Expansion Foam Systems As Dike Protection
Successful use of high-expansion foam has been employed

14. High-Expansion System Extinguishment Mechanisms
High-expansion foam systems are suitable for the protection of
Class A ordinary combustibles
Class B combustible liquids
Extinguishment is accomplished by
Smothering
Cooling
Insulating
Penetrating

15. Design Of Total Flooding High-Expansion Foam Systems
Total flooding method: completely filling a room or enclosure volume with a fire protection agent
Personnel Considerations for High- Expansion Foam
High-Expansion Foam Components
Determination of High-Expansion Foam Quantity

16. Design Of Total Flooding High-Expansion Foam Systems
Duration of High-Expansion Foam Application (see Table 5-2, Page 181)
Discharge Rate
Number of Generators Required

17. Ex. 5-1: High-Expansion Foam

18. Ex. 5-1: High-Expansion Foam

19. Summary High-expansion foam systems
Primarily for volumetric total flooding of three dimensional objects
Use a foam with an expansion ratio of between 200 to 1 and 1000 to 1
Foam is expanded by a high-expansion foam generator that resembles a large fan

20. Summary
High-expansion foam extinguishes fire by smothering, cooling, insulating, and penetrating
NFPA 11 requires that high-expansion foam be flooded to an elevation exceeding 10% above the highest combustible, or 2 ft. above the hazard, whichever is higher
The rate of high-expansion foam discharge must consider foam breakdown that might occur if a sprinkler system is activated above the area protected by high-expansion foam