FOAM EXTINGUISHING SYSTEMS
Low Expansion Foam System
Low-expansion foam extinguishing systems can be applied to storage tanks, tanker filling areas and special risk areas containing flammable-flammable liquids. These systems discharge foam bubbles to the liquid surface. Thus, it extinguishes the fire by forming a condensed layer on the cooling and flammable liquid surface.
Foam concentrates developed for these systems are used at a rate of 3%-6%. The foams formed by these concentrates expand from 1 to 20 times their original volume after exiting the sprinklers. They are very effective in two-dimensional liquid fires. Due to their structure, they are lighter than liquid fuels, they cover the liquids and cut off the contact of the flame with oxygen thanks to their high spreading properties, they absorb the heat of the fuel with their heat shrinking properties, the cooled fuel cannot evaporate and cannot be ignited. There are various types. Alcohol resistant (AR-AFFF) type foam concentrate is used in polar liquids.
High Expansion Foam System
Although the tests for the High Expansion foam extinguishing system and the places used are limited, it is a system that shows a high extinguishing performance. Very expanded foams have a volume of 200 to 2000 times their original volume after exiting the ejector. They exhibit very effective extinguishing performance in fires that spread in three dimensions, they are designed to fill the volume. Each manufacturer must use the appropriate foam concentration for their disposal device. In this type of systems, the discharge devices inflate the aqueous foam solution with air directly or by means of a fan and discharge it to the application area.
There are design criteria for its use in aircraft hangars and liquid and storage buildings with the following features.
Foam extinguishing systems can be analyzed as wet-pipe, dry-pipe, pre-reactive and dominant systems. In general, there are system definitions and information in NFPA 11, and the design is made according to NFPA 16 and NFPA 30 codes. Equipment capacity and pipe diameters are determined by hydraulic calculation.
