| Tweet |
Custom Search
|
|
|
||
 TM 55-1905-223-SDC
reignition. Since water does not mix with these fuels, nor does it stop evolution of flammable vapors, water
alone usually causes flammable fuel fires to spread dangerously.
g. Paper products. Paper products constitute one of the larger fire loads, but if good housekeeping
is observed, there is a low potential for a large fire.
Section VI. EXTINGUISHING AGENTS
6-14.
TYPES OF AGENTS. The extinguishing agents dispensed from hand-held equipment and
which are used on ships are water, carbon dioxide (C02), dry potassium bicarbonate chemical (PKP), and
Aqueous Film Forming Foam (AFFF).
a. Water. Water is, and has long been, the most commonly used extinguishing agent. Water
lowers the temperature of a burning substance below its ignition point. Water brought to bear on a fire can be
in the form of high velocity fog, low-velocity fog or solid stream using the all-purpose nozzle. Extensive fire
tests have shown that the all-purpose nozzle with the low velocity fog applicator is the best nozzle for ship
use. Using water in the form of water fog greatly increases the surface area and consequently the rate of heat
exchange between the burning material and the water. This heat exchange produces steam, which has a
smothering effect on fire.
(1) High-velocity fog. High-velocity fog allows the firefighter to attack the fire from a greater
distance and will cause cool air to be drawn toward the fire past the firefighter. High-velocity fog shields the
fire- fighter from heat, thus protecting from fire exposure. However, the high- velocity fog tip will also introduce
more water, which is not desired in most cases. See FIGURE 6-2. The all-purpose nozzle was designed to
operate at 60 to 100 psi and, when used at the minimum pressure, the high-velocity tip does not perform as
well as the low-velocity fog based on a study conducted by the Navy. The Navy reports a 27-square-foot pan
fire could not always be extinguished using high-velocity fog but could be extinguished consistently using low-
velocity fog. See FIGURE 6-3.
(2) Low-velocity fog. Using a 4-foot low-velocity water fog applicator, the firefighter can reach
over or around obstructions to apply a cooling, smothering blanket of fog on the fire. The all-purpose nozzle,
when equipped with the applicator and fog-head, projects (FIGURE 6-4) a fog having the maximum of
diffusion. The fog pattern from the fog-head is at its most effective dimensions 5 or 6 feet from the tip of the
applicator. It also precipitates and dissolves smoke and fire products while providing a cool path advancing on
the fire. On the LCU, low velocity fog applicators are located at Fire Stations 1 and 2 in the Machinery Space.
Using water in the form of low-velocity fog to put out electrically caused fires is acceptable when two portable
extinguishers have not put out the fire. It is assumed that an effort has been made to deenergize electrical
equipment; however, research has not revealed any cases of electrocution due to the application of a low-
velocity fog on shipboard electrical fires. The primary concern when using water on an electrical fire is
damage to equipment by sea water. Using the low-velocity fog applicator speeds extinguishment, decreases
|
||
|
||
