8
7 NP 72 en
3
INPUT SIGNAL AND DIRECTIONS OF
OPERATION
Figure 6 assists in choosing the right segment for the cam
plate (29) and position for the changeover piece (46).
3.1
Changeover piece
The function of connection C1 and C2 can be altered by
turning the changeover piece (46). The diagram D (or R)
shown on the protective plate (48) functions when the sym-
bol D (or R) is visible in the lower lefthand corner of the
changeover piece (46).
D = direct, R = reverse.
External changes in the tubes are not needed. Positioner
NP727 is an exception (DIA6HC pilot valve). Then the
changeover piece must always be in position R and the
external tubes mounted in accordance with Fig. 5.
3.2
Cam plate
The figures marked on the cam plate (29) are the signal
ranges expressed as percentages, for example 0-100 corre-
sponds to 0.2–1.0 bar (3-15 psi), or 50-100 to 0.60-1.0 bar (9-
15 psi), see Fig. 6.
The arrows on the cam show the direction it must turn
when the input signal is rising in the cam segment in ques-
tion.
The non-rising segments between the rising segments are
roughly 15-20°.
4
PRELIMINARY ACTIONS FOR THE
ADJUSTMENT
Set the valve’s open and closed limits with the actuator lim-
iter screws; see the valve instruction manual. The changeo-
ver piece (46) and the cam (29) must be in correct positions.
Check the pilot valve size from Table 2.
The adjustment must always be carried out when the sup-
ply pressure has been changed.
Please note that operating of the valve is required during
the adjustment.
4.1
Position of the changeover piece
Choose the position of the changeover piece, D or R, from
Fig. 7 in accordance with the function desired.
Turn the changeover piece (46) when necessary.
Loosen the nuts (49) and remove the protective plate (48).
Pull out the changeover piece (46). Check the O-rings (47, 2
pcs.) and apply silicone grease lightly if needed. Place the
changeover piece (46) and the protective plate (48) in the
case. Tighten the nuts (49) evenly, one after the other.
4.2
Pilot valve
Removal of the pilot valve is unnecessary when the change-
over piece is turned around. For instructions of removal, see
Section 8.2.
4.3
Position of the cam plate
Choose the side, A or B, and the rising segment of the cam
plate from Fig. 7 in accordance with the function desired.
Move the actuator piston to the end where the input signal
has its lower value. Shut off the supply pressure or move the
pilot spool by deflecting the beam (5) gently so that the pis-
ton strokes to the desired limit. The input signal should be
zero or at the lower limit.
Fig. 6
Input signal ranges, the cam plate (29).
50 - 100
0 - 100
0 - 50
B
~ 15°
~ 15°
~ 15°
~ 15°
~ 15°
~ 15°
segment C
segment E
segment D
segment C
segment E
0.2–0.6 bar (3–9 psi)
rising signal opens
0.20–1.0 bar (3–15 psi)
rising signal opens
0.2–1.0 bar (3–15 psi)
rising signal closes
0.60–1.0 bar (9–15 psi)
rising signal closes
0.6–1.0 bar (9–15 psi)
rising signal opens
0.2–0.6 bar (3–9 psi)
rising signal closes
CAUTION:
Do not dismantle a pressurized positioner!
NOTE:
Check that the changeover piece is mounted correctly:
Symbol D or R is visible in the lower left hand corner.
Fig. 7
Mounting the changeover piece
47
49
48
46
45
44
43
Summary of Contents for NB723
Page 19: ...7 NP 72 en 19 ...
