32
7 ND90 71 en
6
MAINTENANCE
The maintenance requirements of the ND valve controller
depend on the service conditions, for instance, the quality
of instrument air. Under normal service conditions there is
no requirement for regular maintenance.
When maintaining the ND ensure that the supply air is shut
off and pressure is released. In the following text the num-
bers in brackets ( ) correspond to the part numbers in the
exploded view as shown in Chapter 12, unless otherwise
stated.
The ND valve controller includes the following interchange-
able modules: prestage unit (120), spool valve (193), com-
munication circuit board with optional position transmitter
(215).
In ND9100 and ND7100 the modules are located below the
covers (39) and (43). In ND9200, ND7200 and ND9300 the
spool valve is located on the bottom side of the device
while the other modules are located below the covers (100)
and (39). In the event of failure the whole module must be
changed. The module retrofit must be assembled in a clean,
dry environment. In reassembly apply a thread-locking
compound (for instance, Loctite 243) and tighten the
screws firmly.
6.1
Prestage
6.1.1 Removal
ND9100, ND9400 and ND7100
Open the prestage cover (43) attached with M4
screw (44). Unplug the prestage wire connector on
the spool sensor board. Unscrew the M4 screws (139,
2 pcs.) and lift up the prestage module. Remove the
O-ring (140).
ND9200, ND7200, ND9300
Loosen the M8 stop screw (110) in the position indi-
cator (109) and turn the position indicator from the
shaft (11). Remove the inner cover (39) attached with
M3 screws (42, 3 pcs).
Unplug the prestage wire connector from the spool
sensor board (182). Unscrew the M4 screws (139, 2
pcs.) and lift up the prestage module. Remove the O-
ring (140).
6.1.2 Installation
ND9100, ND9400 and ND7100
Place a new O-ring (140) into the groove on the
spool valve and press the prestage into place. Make
sure the nozzle is guided into the O-ring properly.
The screws guide the prestage body into the correct
position. Tighten the screws (139) evenly.
Push the prestage 2-pole wire connector into the
socket on the spool sensor board. The wire connec-
tor may only be fitted in the correct position. Replace
the prestage cover (43) and tighten the M4 screw
(44).
ND9200, ND7200, ND9300
Place a new O-ring (140) into the groove in the hous-
ing and press the prestage into place. Make sure the
nozzle is guided into the O-ring properly. The screws
guide the prestage body into the correct position.
Tighten the screws (139) evenly.
Push the prestage 2-pole wire connector into the
socket on the spool sensor board. The wire connec-
tor can only be fitted in the correct position. Replace
the inner cover (39) and tighten the M3 screws.
6.2
Spool valve
6.2.1 Removal
ND9100, ND9400 and ND7100
Before removing the spool valve assembly (193) the
prestage (120) must be removed. See 6.1.
Unscrew the M4 screws (47, 3 pcs.), M3 screws (48, 2
pcs.) and M3 screw (49). Remove the spool valve
assembly.
The spool valve may be cleaned if special attention is
paid to a clean environment and proper procedure.
After unscrewing the M4 screws (47, 3 pcs.) the spool
valve may be lifted from the fixture. Hold the ends of
the body with your fingers to avoid dropping the
spool from the body. Clean the spool and the bore of
the body with care. Do not leave any fibres from
cleaning materials in the bore or on the spool. Do
not scratch the mating surfaces of the spool and
body. The restrictor is located under the spool valve
in the fixture. It may be cleaned when the spool
valve is removed.
ND9200, ND7200, ND9300
For spool valve removal it is usually necessary to unmount
the valve controller from the actuator.
Working from the bottom side of the valve control-
ler, unscrew the M4 screws (47, 3 pcs.). Remove the
spool valve cover (61) and the spool valve (193) with
gasket (174). Hold the ends of the body with your
fingers to avoid dropping the spool from the body.
Ex d WARNING (ND9200, ND7200, ND9300):
Service of the cylindrical flameproof joints is not
allowed.
This includes the diaphragm cover (part 171), flame arrester
plunger (part 200), their mating surfaces in the housing
(part 2) and the shaft assembly fixed in the housing
.
NOTE:
The prestage must be handled carefully. In particular the
moving parts of the prestage should not be touched
when the inner cover (39) is not in place.
NOTE:
Each spool valve body has an individual corresponding
spool which cannot be replaced by any other spool. Never
alter the orientation of the spool. The orientation of the
spool is marked on the device, see Fig. 34 and 35.
