Bosch FAS-420-TP2 - Page 34

34 en | Planning Aspiration smoke detector LSN improved
2020.04 | 6.1 | F.01U.029.275 Operation guide Bosch Sicherheitssysteme GmbH
If structural circumstances dictate that the pipe system is to be designed asymmetrically, the
following conditions apply:
– The number of air sampling openings and the length of the shortest and longest pipe
branch within the pipe system must not exceed a quantity ratio of 1:2.
– The distance between neighboring air sampling openings on the smoke aspiration pipe
must be equal (should not exceed ±20% deviation).
– The diameters of the air sampling openings are determined separately for each pipe
branch. The diameters depend on the total number of air sampling openings in the pipe
branch in question.
The figure shows a typical U-pipe system with three or six air sampling openings and the air
sampling opening diameters calculated according to Standard Pipe Planning.
A
B
FAS / FCS
2,5
3,4 3,6 3,8
3,0 2,35,25,2 3,0
0,35,2 2,35,25,2 3,0
0,35,2 2,35,25,2 3,0
A Symmetrical pipe system
B Asymmetrical pipe system
Tab.4.1: Example of a symmetrical and an asymmetrical U-pipe system
Pipe diameter
As a rule, the pipe system is created using pipes with an external diameter of 25mm. PVC or
halogen-free pipes can be used. Halogen-free pipes are to be used in preference for
equipment monitoring.
In many applications, greater distances between the aspirating smoke detector and the
aspiration pipe must be bridged. This is done using pipes with greater diameters (40mm),
which guarantees maximum planning (see also Planning for long pipe feed lines, page 56 ).
However, pipes with greater diameters restrict the length of the pipe system.
Branch length
To achieve short transport times for the smoke aerosols in the aspiration pipe and thus quick
detection, it is better to plan several short branches than fewer long ones (preferably U and
double U-pipe system).
Pipe configurations
Depending on the area geometry, five pipe configurations can be selected:
– I-pipe: pipe system without branches.
– U-pipe: pipe system that branches into two pipe branches.
– M-pipe: pipe system that branches into three pipe branches.
– Double U-pipe: pipe system that branches symmetrically into four pipe branches.
– Quadruple U-pipe: pipe system that branches symmetrically into eight pipe branches.