FISCHER PRO-LINE DE90, Operating Manual

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FISCHER Mess- und Regeltechnik GmbH Operation | 5
BA_EN_DE90 73
5.5.3.3.2.1 Explanations for dynamic filter monitoring
Δp Q
Δp
Δp SUP
W
1
2
3
4
5
6
7
Fig. 103: Principle Diagram for Filter Monitoring
1 Zones with variable supply air volume flow rate
2 Supply air pressure control with fan speed control
3 Differential pressure sensor for filter monitoring (
Channel ∆p
)
4 Volume flow sensor (
Channel Q
)
5 Setpoint encoder
6 Differential pressure regulator for filter monitoring
7 Air filter fault message
The air filter in this example has the task of retaining dust impurities from the
outside air. With increasing contamination, the pressure difference measured
above the filter increases. As soon as the pressure difference exceeds the set
limit value, the filter monitoring system signals the contamination of the filter.
This is indicated as a fault.
The volume flow control keeps the air volume flow constant despite increasing
contamination by increasing the fan speed. However, the pressure drop across
the air filter does not only depend on the degree of contamination, but also on
the size of the volume flow.
The pressure drop changes as a square of the volume flow. Therefore a reduc-
tion of the volume flow from 100 % to 50 % means a reduction of the pressure
drop across the filter element from 100 % to 25 %.
20 40 60 80 100
20
40
60
80
100
25
50
Δp [%]
Q [%]
Fig. 104: General filter characteristic curve