Adjustment To The Valve And Application Data - Burkert 8605 KK Instructions De Service

6.3 adjustment to the Valve
and application data
The working range of a valve in a particular application depends greatly on
its nominal size and the prevailing pressure conditions.
In order to adapt the working range optimally to the range of the control
signal, the key values for the effective coil current are set via the operating
unit in such a way that
• the opening of the valve starts at a current value slightly above the lower
key value (I
1
• the full flow rate is achieved at a current value slightly below the upper key
value (I ).
2
The lower key value is the current controlled at the lowest value of the
standard signal (0 V, 0 mA or 4 mA).
The upper key value is obtained at the maximum value of the standard signal
(5 V, 10 V or 20 mA).
Between the two key values, the effective coil current has a linear relation-
ship to the input signal (see Illustration 6-5:
I
I
2
I
1
2 %
Illustration 6-5: Current over standard signal
The working range can also be scaled using the key values I
a way that only a part of the full opening of the valve is covered over the full
range of the standard signal. In particular the flow rate range can be limited
to a smaller value than the valve would permit under the given pressure
conditions.
The zero point cut-off guarantees the leak-tight closing of the valve at input
signals below a given threshold of the input signal (e.g. < 2 % of the limit
value). In this case at values below this threshold, the coil current is set
- in deviation from the line shown in Illustration 6-5 - to zero so that the full
18 - 8605
) and
100 % Standard signal
Current over standard signal
and I
1
).
in such
2