buradan - Yangın

TÜYAK BİLDİRİLER KİTABI
2009 PROCEEDINGS BOOK
There are four techniques to disable the fire triangle:
w Separation;
w Choking;
w Cooling;
w Chemical inhibition;
The separation technique consist of the separation of unburnt
combustive from the burning one, it is substantially a mechanical
system which isolates parts of area with fire resistant boundaries.
The choking technique works on a chemical basis and consists of
removing the combustive agent from the surrounding atmosphere
by covering the burning part with covers or injecting inert gasses
such as CO 2 (carbon dioxide) and N 2 (nitrogen).
The cooling method subtracts energy to the fire reducing the
temperature below the lightening point of the combustive,
subtraction of energy could be done by heating the cooling agent
or due to chemical transformation.
The chemical inhibition effects chemically the combustive reducing
it’s capacity to react with the oxygen.
Except few particular cases where there are chemicals, the most
frequent extinguishing elements are:
w Water;
w Foam;
w Carbon dioxide;
w Powder.
Water is the most spread extinguishing agent as it is generally
available and low cost. Water works with two of the above
mentioned principles, it reduces the temperature by it’s evaporation
and in most of the circumstances also reacts with the combustible
reducing the available oxygen. Water is not indicated for gasses, low
density liquids, metals and compositions with very high lightening
points, chemical agents that react with water (peroxides, chlorides,
...), electric components under continuous tension, areas where
temperature is lower then 0°C.
Foam is produced with water, inert gas and tensioning additives.
Principle of this extinguishing element is the chocking by covering
the burning surfaces with the foam and cooling due to the water
evaporation. Basically has the same limitation of simple water with
the addition to be avoided with chemicals that can react with the
tensioning additives reducing the emulsioning capacity with the
inert gas.
Carbon dioxide reduces the density of reacting oxygen and with
it’s expansion from liquid state to gas state cools the surrounding
atmosphere. Could be used for gasses fires as well. As carbon
dioxide is not toxic there aren’t any special counter indication but
the location needs to be ventilated before entering given the risk
of asphyxiation.
Powders provide a choking action to the fire, and even more when
heated with the production of carbon dioxide. There are different
type of powders depending on the type of potential combustible
available but they are generally alkali based mixtures. Suited for all
kind of applications with the right choice of powder mixture.
The application of the above described methods and elements
encompasses:
4
TÜYAK 2009
w Hydrants;
w Extinguishers;
w Sprinkler;
w Water mist;
Hydrants are to be used with water pressurized systems, located
internally or externally of buildings have hoses that permits the
operator to move within a certain area of action. The externally
installed hydrants are located at a safe distance for which the water
jet can reach the fire without putting the operator in harm. If the
available pressure of the system (generally the municipal water
supply) is not enough to cover the flow and pressure demand,
a booster pumping unit needs to be provided. Hydrants are non
automatic tools – trained personnel is needed.
Extinguishers can be filled with Powder or inhibiting gasses,
pre-pressurized are located in the risky areas. Extinguishers are
generally not designed to put out a fire a fire but they can be useful
to extinguish the beginning of a major fire. These are not automatic
instruments – an individual needs to use it upon need.
Sprinkler systems are made of a water pressurized pipe network
and related attached sprinklers. A sprinkler has the function to
open the port when a set temperature is reached.
Ceiling
Cup
Retainer
Generally the nozzle closing element is a piece of glass filled with
liquid, with the heating of it the liquid brakes the glass and opens
the nozzle, the water starts to flush out and a deviator spreads the
water jet around it covering an area of about ........... In case the
water source could not guarantee a sufficient pressure and flow,
a booster pumping unit needs to be provided. It is a full automatic
system as in the case of presence of pressurizing pumping units,
there are pressure sensors that monitor any eventual pressure
drop in the system and start the pumps automatically guarantying
a sufficient flow.
Water mist technique is a direct descendant of the sprinkler
systems, the pressure within the system is higher and enables the
nozzle (differently shaped) to produce a mist output of water.
3. Reliability
In accidents such as fires we all need to have full reliance on the
equipments that are intended to protect our lives in the first place
and our either private or public possessions in the second place. A
technologic product has the most chances to fail when the required