Chapter 2 • Manner of operation of a Purging unit
User Manual Series F-BO-AFE70
2
Manner of operation of a Purging unit
Typical structure of a system, consisting of fire detection control panel, aspirating smoke detector,
Purging unit, compressed-air supply and sampling pipe.
Fig. 2:
Depiction of the structure of a system with an Automatic Purging Unit F-BO-AFE70 as well as
the required components and connections
A … Automatic Purging Unit F-BO-AFE70
B … Compressed-air supply
C … Aspirating smoke detector; in the above diagram an ASD with one pipe is shown, note that
for each pipe system a separate Purging unit is needed.
D … Fire detection control panel
E … Power supply line. Both the Purging unit as well as the ASD must be supplied with 24VDC.
F … Transmission of the fault message of the ASD to the fire detection control panel
G … Transmission of the fire alarm of the ASD to the fire detection control panel. The connection
can be established – as shown in the figure above – by means of a conventional line or via
loop modules.
H … The fire detection control panel actuates or activates the F-BO-AFE70
I … Air filter (optional), which can be located before the Purging unit. As a result, on the one
hand the Purging unit is protected against contamination, and on the other hand every Pur-
ging process also cleans the filter. If this is not possible (for example, because the filter case
is not pressure-resistant), the filter must be located between the Purging unit and the aspir-
ating smoke detector.
J … Check valve
2.1
General
Aspirating smoke detectors use a low negative pressure to continuously sample air through aspira-
tion holes of a sampling pipe that is laid in a room or building, and direct the air samples to a cent-
ral measuring element (the evaluation unit) in order to examine the sample for various characterist-
ics (e.g., the smoke concentration).
Over the operating time, continuously aspirating the ambient medium through the relatively small
aspiration holes and a pipe network with a relatively small cross-sectional area leads to an accumu-
lation of contaminations which can change the aspirated air flow and can even result in the meas-
urement failing completely. In order to prevent this contamination, dirty pipe networks and filter
systems should be regularly cleaned („purged“) by means of compressed air.
For this purpose, clean compressed air is manually or automatically led into the pipe network
and/or the filter system at intervals. In order to protect the evaluation unit of the aspirating smoke
detector against damage caused by exposure to compressed air, in conventional Purging units first a
valve isolates the evaluation unit from the pipe network, and then compressed air is led into the
pipe network through a second valve that is connected to a T-piece.
I56-4252-010
D200-104-00
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Summary of Contents for F-BO-AFE70 Series
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