17
4.7.4 Fail-safe active
When the ND9200H detects serious device failure (set-
point, valve position and control signals) it enters fail-
safe mode, which drives the control valve into the posi-
tion defined in the parameter controller fail action (
PFA
).
Fail-safe mode is indicated by the display as seen in Fig
19. The error message is displayed until the cause of
error is eliminated and the ND9200H unit is restarted, i.e.
the power loop is momentarily disconnected.
4.8
HART write protection
The ND9200H is delivered from the factory with the
default set as HART write protection OFF. Reading and
changing parameters is allowed. HART protection may
be enabled with a switch (DIP1) located on the commu-
nication circuit board under the Local User Interface
module, Fig. 20. Changes that may influence the valve
position cannot be made using the FieldCare software or
HART hand held when switch no. 1 (on the left-hand side
of the switch block) is ON.
5
MAINTENANCE
The maintenance requirements of the ND9200H 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 ND9200H ensure that the supply
air is shut off and pressure is released. In the following
text the numbers in brackets ( ) correspond to the part
numbers in the exploded view as shown in Chapter 10,
unless otherwise stated.
The ND9200H valve controller includes the following
interchangeable modules: prestage unit (120), spool
valve (193), communication circuit board with optional
position transmitter (215) and controller circuit board
with position and pressure sensors (210 ).
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.
5.1
Prestage
5.1.1 Removal
❑
Loosen the M8 stop screw (110) in the position
indicator (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 (180). Unscrew the M4
screws (139, 2 pcs.) and lift up the prestage
module. Remove the O-ring (140).
5.1.2 Installation
❑
Place a new O-ring (140) into the groove in the
housing 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 cor-
rect position. Tighten the screws (139) evenly.
❑
Push the prestage 2-pole wire connector into the
socket on the spool sensor board. The wire con-
nector can only be fitted in the correct position.
Replace the inner cover (39) and tighten the M3
screws.
Fig. 19
Failsafe display
Fig. 20
HART write protection
ITION SENSOR FAILURE
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12
ON
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.
Содержание ND9200H
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