10
7 NE 72 en
5
BASIC ADJUSTMENT
Basic adjustment is made to rotary and butterfly valves.
Please note the procedures in Chapter 4 before the adjust-
ment.
1. Switch on the supply pressure (S) and the input signal (+/-).
Note the correct polarity.
2. Set the input signal at the closed limit of the valve so that
it is 2 % i.e. 0.3 mA higher or lower than the limit value,
e.g. 4 + 0.3 = 4.3 mA or 20 - 0.3 = 19.7 mA. Turn the zero
adjustment nut (61) with a screwdriver or fingers so that
the actuator comes slowly to the closed limit. The valve
should open slightly with a 4 % change in signal, that is
0.6 mA, e.g. 4 + 0.6 = 4.6 mA or 20 - 0.6 =19.4 mA. See Fig-
ures 12 and 13.
3. Set the input signal to the other limit value. The valve
should be entirely open at 100 %, i.e. 20 mA or 0 %, i.e. 4
mA. The valve should start to operate to closed direc-
tion at 98 %, i.e. 19.7 mA or 4.3 mA.
The range, i.e. turning angle, increases by turning the
range adjustment potentiometer (35.6) counterclock-
wise and de-creases by turning clockwise.
4. The zero and range adjustments affect each other, so
stages 2 and 3 must be repeated a few times.
5. Screw on the pointer (32) into place so that the yellow
line is in the direction of the valve closing member.
Tighten the screw (57).
6
α
0
ADJUSTMENT
α
0
adjustment is made to segment and ball valves. This
adjustment takes into account the "dead angle"
α
0
of the
ball valve. The entire signal range is then used for effective
valve opening 90°-
α
0
, see Figure 14.
The same adjustment method can be applied to butterfly
valves in papermills for pulp flow control to avoid the dewa-
tering of the pulp near the closed position of the disc.
Table 4 shows the shift on the circumference of the cam
equal to the "dead angle" of the valve, Figure 15, in various
cam segments (C, E, D).
Please note the procedures in Chapter 4 before the adjust-
ment.
1. Mark the shift in question on the edge of the cam, Fig. 15
and Table 4. Dimensions do not have to be measured if
the dead angle can be reliably noticed from position of
the closing member.
2. Lock the cam so that the roller touches the edge of the
cam plate at the mark. Tighten the locking wheel (30)
and the screw (31).
3. Switch on the supply pressure (S) and the input signal
(+/-). Note the correct polarity.
Fig. 11
Basic and
α
0
adjustments
Fig. 12
Zero and range adjustments
POSITION %
Rising input signal closes valve
Rising input signal opens valve
max 2 %
INPUT SIGNAL %
safety range 2 %
Basic adjustment
α
0
adjustment
U
I
SP
AN
D
zero adjustment (61)
internal feed-back
spring (40)
feed-back spring (41)
terminal card (35)
range adjustment (35, 6)
Fig. 13
Zero and range adjustments
Fig. 14
Shift on circumference of cam equal to dead angle
α
0
= dead angle
segment D
segment C
segment E
shift
Roller contact point when
the ball is completely closed
