Calculate Detection Distance - Siemens FDF241-9 Technical Manual

Planning
4
Defining the place of installation

4.2.1 Calculate detection distance

32 | 66
Building Technologies
Fire Safety
The maximum detection distance of a flame detector depends on the following
factors:
Detector sensitivity
Fire size
Directional sensitivity
Fuel
Various correction coefficients therefore need to be taken into account when
calculating the maximum detection distance.
Formula for calculating maximum detection distance d
Gg
´ ´
d = S K
Gb
d Detection distance
S Correction coefficient for detector
sensitivity
Gg Fire size wanted
The correction coefficients for calculating the detection distance are described in
the following sections.
The detection distance is reduced by up to 15 % by films of oil or water on the
flame detector's protective glass.
Correction coefficient S for detector sensitivity
The table below shows the correction coefficients for detector sensitivity. Only
select 'High' detector sensitivity if there are no deceptive phenomena.
Detector sensitivity
Normal
High
Fire size wanted Gg
The fire size wanted Gg is the minimum size of the fire that is to be detected. The
smaller the fire, the shorter the detection distance. Choose the basic area of the
fire in m for Gg.
2
Basic fire size Gb
The basic fire size Gb is constant and is 0.25 m
´
F
Gb Basic fire size
K Correction coefficient for
directional sensitivity
F Correction coefficient for fuel
Correction coefficient S
23
46
.
2
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2018-06-28