Combustible liquid fire (TF6)
5.3.1 Heat detector
The Siemens heat detectors trigger an alarm at temperatures ranging from approx.
60
o
C to 85
o
C. In addition, depending on the parameter set, the FDT241 and
FDT221 react to a rapid increase in temperature.
For TF6 the ceiling construction, ambient temperature, ventilation and a number of
other factors have a very great influence on heat development at the ceiling. Due
to this fact and the recommendation to "only carry out acceptance fire tests with
spirit in very specific situations" the size of the fire is not divided among the
individual detectors with the corresponding parameter sets.
The following table shows the size of fire required to trigger an alarm in detectors
which react at 85
°
C.
The values are based on the following conditions:
– Temperature underneath the ceiling must always be below 125
°
C
– Duration of fire approx. five minutes
– The sides of the room are roughly 1.5 times longer than the height
– Airflow approx. 0.5m/s
Room height
[m]
Container size
[m
2
]
Amount of ethyl alcohol
[l] (filled to a height of 10mm)
4 0.2 2
7 0.5 5
10 1.0 10
Tab. 5 Amount of ethyl alcohol for heat detectors
Damage If possible do not use test fire 6 to avoid the risk of damage!
The performance of heat detectors can be tested quickly and safely with the RE6T
detector tester.
5.3.2 Flame detector
In addition to the distance between the detector and fire, the size of fire that can be
detected by a flame detector depends very much on the detection principle, the
evaluating device and the level of sensitivity to which the detector has been set.
The required fire size for the FDF241 and FDF221 is calculated as follows:
A = 0.25 x (D / C)
2
A = surface area of the container [m
2
]
D = distance from detector to fire [m]
C = constant for detector sensitivity
(normal = 23 / high = 46)
18
Building Technologies 009977_b_en.doc
Fire Safety & Security Products 10.2007
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