Burkert Type 8709 - Manual (Page 15)

15
System Description
proportional valve 5.3.
The LFC uses direct acting, lifting-armature, proportional valves as actuating elements, taken from the Bürkert
range of valves.
The low-friction guide of the valve armature ensures (in conjunction with the PWM control) a continuous, mainly
linear characteristic, as well as high response sensitivity. Both are important for the optimum functionality of the
LFC closed control circuit.
The orifices of the valves are based on the required nominal flow-rate Q
nom
, the pressure conditions in the appli-
cation and the density of the operating fluid.
A proportional valve is selected by the manufacturer on the basis of this data, so that the flow-rate coefficient k
V
of
the LFC (according to the flow-rate equations at the specified pressure conditions) allows a maximum flow-rate of
at least the required nominal flow-rate Q
nom
.
If the device is operated within the specified pressure range, the proportional valve simultaneously takes
over the sealing function together with the control function.
In the case of special, hard seal materials, the seal function could not be ensured. In this case an addi-
tional shut-off valve may be required.
The LFC or LFM is typically calibrated to units which are useful for low flow-rates such as l/h or ml/min.
english
Type 8718, 8719 / 8708, 8709