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DRY
CHEMICAL POWDER TOTAL FLOODING SYSTEM
Description
 Dry
chemical fixed pipe fire suppression systems are self contained
units, designed by factory trained personnel, consisting of
a pressure vessel constructed to ASME standards, nitrogen
cylinders meeting U.S. Department of Transportation standards,
automatic detection devices and electric/pneumatic manual
actuation devices. These systems use dry chemical extinguishing
agents such as PLUS FIFTY B, PLUS FIFTY C, PURPLE K and FORAY;
or special dry powder agents such as MELT-X, LITH X, NA X
and MELT L KYL.
What
extinguishing agents are available & how will they be selected
01
" FOREY "
Phosphate
base dry chemical extinguishing agent for use on all class A,
B & C fires.
02.
" PURPLE - K "
Purple -
K dry chemical is a potassium bicarbonate base dry chemical
agent with AFFF compatibility. Effective on both class B and
class C fires. It is often considered to be the most effective
dry chemical agent on class B hydrocarbon fuels. Several tests
worldwide have proven that " Purple - K " is much more effective
compared to " Monnex ".
03.
" PLUS - FIFTY - C "
Plus Fifty
C is also a sodium bicarbonate based dry chemical agent but
is treated with silicon to ensure foam compatibility. It is
effective on class B and class C fires.
04.
" PLUS - FIFTY - B "
Plus Fifty
B is a sodium bicarbonate based dry chemical for use on class
B and class C fires.
05.
" SPECIAL SCI "
Agents for
special hazards including metal and deep seated fires like LITH
- X, METL - L - X, METL - L - KYL, etc.
How
does the system operates
The
operation sequence and drawing below illustrate the simplicity
of a dry chemical fire suppression system "
- If
a fire breaks out in protected area, the detection system
senses the fire and signals to the automan control system.
- The
automan control system responds instantly and provides a
pneumatic signal to open the valves on the nitrogen cylinders
containing the expellent gas.
- Additionally,
a fully supervised autopulse control system can be incorporated
into the system to provide alarms, remote annunciation,
and shut down of process equipment that could fuel a fire
or otherwise hamper extinguishment.
- The
nitrogen expellent gas flows from the nitrogen cylinders
through pressure regulators and into the dry chemical tank.
- Upon
entering the dry chemical tank, the nitrogen mixes with
or " fluidizes " the dry chemical agent and increases the
pressure within the tank.
- When
the pressure in the dry chemical tank reaches a predetermined
level, a bursting disc ruptures and allows the dry chemical
to flow through the distribution piping.
- The
dry chemical quickly flows through the piping network and
out the nozzles.
- The
nozzles are designed to control the flow, direction and
coverage of the agent to suppress the fire.
What
method of application is recommended
There
are two basic application methods for dry chemical piped system
:
- Total
flooding
- Local
application
Hazard
characteristics will determine which method is most appropriate.
- Total
Flooding
Total flooding is based on the concept of " volume protection
" and involves dispersion of dry chemical throughout the specific
volume. This method is used when the hazard is entirely enclosed.
- Local
application - overhead
Local application overhead is based on " area protection "
where the dry chemical is applied to specific hazard areas
from nozzles mounted overhead. The hazard may be located outside
where total flooding application is inappropriate.
- Local
application - Tank side
Local application tank side is also based on " area protection
" but the dry chemical is applied in a horizontal direction
over the surface. The nozzles are mounted above the liquid
surface to minimise and to use the opposite tank side as a
backdrop.
Discharge
Nozzles
Application
These
nozzles are specifically designed for use in dry chemical
systems. The nozzles are engineered for a specific method
of application and dry chemical discharged rate depending
on the nozzle type and size.
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