Sensor Installation Handbook Preface 3rd edition - Siemens ...

Flow velocity · Air
54
Flow velocity Air
Formula:
dg = Equivalent diameter
The pressure-tapping point must not be located
in turbulent air. Ensure sufficiently long settling-zones
upstream and downstream of the
tapping point.
A settling-zone consists of a straight section of
pipe or duct, with no obstructions.
Fan-belt monitoring
The differential pressure across the fan is only
suitable for fan-belt monitoring.
■ Negative connection (–) on suction side
use copper tube
■ Positive connection (+) on discharge side:
use Pitot tube
Flow monitoring
Flow detectors (electrothermal)
Electrothermal flow detectors must be installed
in a zone with a high flow velocity, e.g. where
pipes narrow.
Differential pressure
Do not monitor flow or differential pressure
where flow resistance is variable, e.g. at filters,
cooling coils, fans etc. Suitable locations:
heating coils, silencers, baffles, attenuators.