Foam was first used
to extinguish flammable liquid fires in the early 1900s when
foam was generated by mixing solutions of sodium bicarbonate
and aluminum sulphate containing a foam-stabilizing agent.
This was known as `Chemical foam' and was still frequently
used in extinguishers until quite recently.
Although larger systems were made for tank fire protection the sheer size of
the systems and the problems of maintenance made them both costly and unsatisfactory.
The general use of foam began to grow rapidly in the 1930s with the development
of foaming agents and foam generating equipment, which could produce foam in
relatively simple equipment by entering air. The foam so produced was known
as `mechanical foam' to distinguish it from `chemical foam'.
Unlike other extinguishing agents – water, dry chemical, CO2 etc… a
stable aqueous foam can extinguish a flammable or combustible
liquid fire by the combined
mechanisms of cooling, separating the flame/ignition source from the product
surface, suppressing the vapors and smothering. It can also secure for extended
periods of time.
Most foam applications are associated with the protection of potentially
large flammable liquid risks and although these may be characterized in many
ways.
it is probably most useful to consider them under these headings:
 Large
spill fires
Deep
fuel, contained fires
Fires
in water miscible liquids.
The different types of fixed foam systems are generally used to
protect the hazards like:
Aircraft
hangers
Warehouse
systems
Truck & Rail
loading systems
Storage
tanks
Dike
/Spill protection
Etc…
The different types of foam concentrates
that are generally used in these systems are:
High
Expansion foam concentrates (to be used in High expansion fixed foam systems)
Produced
from 1% to 2% aqueous solution of a synthetic foaming agent.
Low
Expansion foam concentrates
Protein
foaming agents
Fortified
mechanical foams (FP)
Aqueous
Film Forming agents (AFFF)
Alcohol
resistant type foaming agents (AR)
Initiating
Device circuits cause alarm in the panel considered as INPUT.
Panel then switch on the OUTPUT
Circuits and relays to raise an alarm. These alarm sounders
/ strobes shall be silenced by Alarm silence switch. If the
cause for the alarm restores to normal. " RESET" the
panel to bring back to "NORMAL", "DRILL" SWITCH
is used to test the output devices whenever required. Sounders
/ strobes may be inhibited during the drill, not alarm the
public during testing as auxiliary 24VDC Supply shall be
used for 4 wire detectors which need additional power than
detector line. RMOD shall be used for gas release or fire
protection valve controls. City tie module is for external
annunciation through telephone.
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