Foam Enhancement

The application of foam, whether it is via a foam-enhanced sprinkler system, a high expansion foam generator or something in between has a wide spectrum of uses across a bewildering array of fire scenarios.

Water alone will not, in general, extinguish fires involving flammable gases, liquefied flammable gases, and flammable liquids having flash points below 200° F (93° C). The sprinkler and deluge systems (linked to relevant section) outlined can be foam enhanced by installing foam equipment including a foam concentrate supply to discharge a foam/water solution through the particular outlet devices.

Various systems are in common use and each is individually tailored to suit the risk and economically designed to suit the clients' budget. Examples include:

Choices	Typical Application
Foam Enhanced Sprinkler System	Process hazards, petro-chemical and pharmaceutical plant.
Low Expansion Foam	Flammable and combustible liquids in floating roof tanks, sub-surface injection or tank farm bund protection.
Medium Expansion Foam	Combustible solids up to a height of 3m or for external tank farm bunds.
High Expansion Foam	Partial or total flooding of warehouses or aircraft hangars, basements, or areas with significant firewater run-off containment problems. Carousel storage or retrieval systems.
Fixed Roof Tank Protection Systems	Foam Pourers or sub-surface foam systems
Floating Roof Tank Protection Systems	Foam pourer systems

The above list is not exhaustive please consult us for further information regarding the various systems available.

Fire fighting foam is an aggregate of gas-filled bubbles formed from aqueous solutions of specially formulated liquid agent concentrates.

Since foam is lighter than flammable and combustible liquids, it floats on the fuel surface producing a continuous blanket that suppresses fire by separating flammable vapours and oxygen.

There are numerous types of foam that are selected for specific applications according to their properties and performance.

Some foams are thick, viscous and form tough heat resistant blankets over burning liquid surfaces; other foams are thinner and spread more rapidly. Some foams are capable of producing a vapour sealing film of surface-active water solution in a liquid surface.

The main consideration in the selection of foam concentrate is usually:

• Speed of extinction - the initial flame knockdown characteristics of a foam will usually be determined by its fluidity
• Burn back and re-ignition assistance - the stability of a finished foam against direct heat (flame) impingement and its life
• Fuel tolerance - the ability to resist or discourage fuel mixing during foam application and resist ignition.

Special foam concentrates are necessary for application on water miscible fuels such as alcohols, ketones, etc...

Foam is water bearing and therefore also cools the fuel surface.

The induction of foam concentrate into a fixed water extinguishing system such as a fire sprinkler, water deluge, foam pourer or hydrant installation will optimise the effectiveness of the system and enhance the speed of extinguishment or control.

The crucial element is choosing the most appropriate medium for the fire hazard.

Foams inherent characteristics of vapour suppressant, cooling medium and oxygen depletion means that it can work on all fronts of the fire triangle and is therefore the most effective choice for flammable liquid fire scenarios.

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