Operating Information; Selection Criteria - Burkert 8626 Instructions De Service

3

OPERATING INFORMATION

3.1

Selection criteria

Of decisive importance for the selection of MFC are:
• the compatibility of the parts contacted by the medium with the gas to be
controlled;
• the correct choice of flow index, which is essentially defined by the nominal
diameter of the actuator;
• for optimum control behaviour, good adjustment of the nominal diameter to
the pressure conditions, the desired maximum flow rate and the other flow
resistances in the installation.
Dimensioning guidelines may be given on the basis of flow indices that refer to
standardized conditions of pressure, temperature and medium properties. For fluidic
components, the k
The k value is the flow rate of water (T = 20°C) through a component in m
V
pressure difference Dp = 1 bar.
The Q value used in pneumatics is the flow rate of air in l
Nn
pressures up and downstream of the fluidic element are p
and the inlet medium temperature T
flow rate under standard conditions (1013 mbar, 273 K) and gives a mass flow.
Q value and k value are related by the equation
Nn v
NOTE In the following, for the characterization of MFC and installation, we
use their flow indices k
MFC refers to its k
Operating Instructions-No. 801 147
value and the Q value are in widespread use.
V Nn
= 293 K. The volume flow is recalculated to the
1
Q [l /min] = 1078* k
Nn N
and k
Vs
value when the valve is fully open).
V
when the absolute
N
= 7 bar and p
1 2
3
[m /h]
V
(the second subscript s for the
Va
3
/h at a
= 6 bar
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