18
7 SG9H 70 en
4.7.5 Fail-safe active
When the SwitchGuard detects serious device failure (set-
point, valve position and control signals) it enters fail-safe
mode, which drives the control valve into the position
defined in the parameter controller fail action (
PFA
). Fail-
safe mode is indicated by the display as seen in Fig 21. The
error message is displayed until the cause of error is elimi-
nated and the SwitchGuard unit is restarted, i.e. the power
loop is momentarily disconnected.
4.8
HART write protection
The SG9000H 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 communication circuit
board under the Local User Interface module, Fig. 22.
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 SwitchGuard valve
controller depend on the service conditions, for instance,
the quality of instrument air. Under normal service condi-
tions there is no requirement for regular maintenance.
When maintaining the SwitchGuard 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 11, unless other-
wise stated.
The SwitchGuard SG9000H includes the following modules:
prestage unit (120), spool valve (420), communication cir-
cuit board with optional position transmitter (215) and con-
troller 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 cover 100. In
the event of failure the whole module must be changed.
The module retrofit must be assembled in a clean, dry envi-
ronment. On reassembly apply a thread-locking compound
(for instance, Loctite 243) and tighten the screws firmly.
5.1
Opening and closing of the cover
Open SG9000H cover (100) by opening the M4 screw
(107) first until it is not anymore attached to the
housing (2). Then turn the cover counterclockwise
until it can be removed.
Close the cover (100) in reverse order. Mount it first
on top of the housing (2) and then turn it clockwise
until threads are tight and the screw (107) is facing
the spring (111) in the housing (2). Tighten the M4
screw (107).
5.2
Prestage
5.2.1 Removal
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 con-
nector board (182). Unscrew the M4 screws (139, 2
pcs.) and lift up the prestage unit (120). Remove the
O-ring (140).
Fig. 21
Failsafe display
Fig. 22
HART write protection
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12
ON
Ex d NOTE:
Maintenance of the parts of the flameproof enclosure
is not allowed!
Device type SG9000H_E6_:
Housing (2), Cover (100), Shaft assembly (11), Limit switch
housing (300).
NOTE:
Whenever any maintenance operations have been done
for the SG9000H, the device should be calibrated and
tuned.
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.
