buradan - Yangın

TÜYAK BİLDİRİLER KİTABI
2009 PROCEEDINGS BOOK
fire are untouched by the fire. Imagine the destruction if this was a
full warehouse allowed to burn uncontrolled. Remember that this
test was terminated after only 100 seconds.
This test is a perfect demonstration of why full scale fire tests are
necessary. The client’s consultant had done many calculations and
was confident the protection scheme would work but the only way
to be sure is to run a test. Although the test was not cheap it did
prevent an inadequate system from being installed preventing a
potentially much more costly system failure in the real warehouse.
Sprinkler Used In Warehouse
Figure 16. Heat sensitive element in a sprinkler
The sprinklers are installed on pipes which are filled with water
ready and waiting to attack the fire. Each sprinkler has its own heat
sensitive element, a glass bulb or fusible metal link, fixed into the
sprinkler and which holds back the water.
To ensure the sprinkler will not leak 100% of sprinklers are
rigorously tested at pressures well in excess of those they will see
in service.
Figure 17. A specific temparature is needed to start up individual operation
of each sprinkler
This heat sensitive element will ONLY operate when it reaches
a specific temperature with heat from the fire. This means that
only those sprinklers heated up by the fire will operate – not every
sprinkler in the room as often seen on the TV or in movies. They
are not operated by smoke – unless it is accompanied by heat
from a fire!
Figure 18. Water release and distribution of a sprinkler
Once the sprinkler operates the water immediately starts to flow
out from the sprinkler, hitting a deflector which distributes the
water over the fire. As only the sprinklers near the fire operate the
minimum amount of water is used to control the fire. In fact in over
90% of fires in sprinklered buildings are controlled with 4 or fewer
sprinklers.
w Installed at the ceiling
w Installed in racks for very storage
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TÜYAK 2009
w Attack the fire directly
w Also pre-wet goods around the fire to slow the fire down
Figure 19. Typical installation of sprinkler for racks
We have seen that the fire risk in warehouses is severe and in
order to address that risk the sprinkler
system must be designed with all the aspects such as the type of
goods, storage height etc into
account.
As in all sprinkler systems there are sprinklers installed at the
ceiling. With ceiling sprinklers you can protect many warehouse
occupancies, the height will vary on the type of goods and how you
store them but can typically be up to 6 or 7m.
Once you go above these heights you are required to start installing
sprinklers inside the racking. These ‘in-rack’ sprinklers effectively
bring the level of the ceiling down ensuring fast operation and
direct water delivery to the fire. A network of pipes is installed in the
central flue of the rack and sprinklers installed on the pipes. These
in-rack sprinklers must be protected from accidental damage with
guards and also with water shields to prevent water from above
cooling down the sprinkler and preventing it from operating.
Sprinklers used in warehouses operate very quickly, typically in a
full scale test at 13m they may operate only 40-60 seconds after
ignition. The sprinklers work in two main ways to control the fire:
w Water from the sprinkler will travel down the racking and start to
attack the fire directly. The level of control of the fire will depend
on the fire growth, the racking structure and the amount of water
delivered – called the water density. The more risky the fire, the
higher the water density which is applied. For example for a
storage of mattresses on racks to 6m height and protected only
from the ceiling the sprinklers will deliver 17.5 litres per minute to
each square meter of the fire.
w The sprinkler will also spray water onto the goods surrounding
the fire. This slows down the progress of the fire.
It is important to note that although in many cases the sprinklers
will reduce the fire size and may even extinguish it, the fire service
are very much needed to enter the building and ensure the fire
is completely extinguished. All sprinkler systems can provide an
electrical alarm which can be automatically forwarded to the fire
service control centre.