INTERNATIONAL FIRE FIGHTER 31
INDUSTRIAL
T
o be effective, a foam firefighting system
requires that a number of pieces of carefully
matched hardware work together in unison
to deliver a combination of water and foam in the
desired proportions. If any one of these fail to
perform, the firefighting effectiveness of the
system will, at best, be impaired, at worst, be
totally eliminated.
The failure of a firefighting system would be
disastrous in any circumstances, but as most foam
systems are used to protect high-hazard, high fuel
load and potentially explosive facilities, the conse-
quences could be commercially, environmentally
and from a life-safety standpoint, nothing short of
catastrophic. Such scenarios exist in a number
of industries, most notably in the petrochemical,
aviation, marine, the utilities and the mass transit
sectors.
Put in its very simplest form, firefighting foam is
made up of three ingredients: water; the foam
concentrate; and air. The proportioning of the
foam occurs when foam concentrate is mixed with
a flowing stream of water to form a foam solu-
tion. This is mixed with air � the term normally
used is aspirated � to produce foam that is a stable
mass of tiny, air-filled bubbles with a lower density
than oil, petrol or water, allowing it to easily flow
over the surface of the fire's fuel.
Balanced pressure proportioning
Although there are several methods of proportion-
ing, fixed foam systems typically use what is
known as balanced pressure proportioning for
inducing the foam concentrate into the feed water
line, so called because the foam concentrate
pressure is balanced with the water pressure at the
proportioner inlets. This allows the proper amount
of foam concentrate to be metered into the water
stream over a wide range of flow rates and pres-
sures. Because balanced pressure proportioning
equipment is capable of continuously generating
large volumes of foam, these systems are com-
monly used to protect tank farms, jetties, chemical
processing plants, offshore platforms, aircraft
hangars, and loading racks.
There are two types of balanced pressure pro-
portioning equipment. One type is used in foam
pump systems, while the other is used in conjunc-
tion with bladder tanks. Both ensure accurate
foam delivery to fire monitors and deluge systems.
By Peter Kristenson
Senior Manager,
Product Management
Team, for SKUM foam
hardware at Tyco Fire
Suppression & Building
Products
A Sense of
Proportion
In a foam firefighting installation, the delivery hardware is every bit as important
as the foam concentrate. If it lets you down at the critical moment, the care and
attention you have lavished on concentrate selection will have been wasted, and
you may well be staring disaster in the face.

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