Replacing The Pilot/Actuator Assembly; Module Subassembly; Terminal Compartment - Emerson Fisher 846 Instruction Manual

Instruction Manual
Form 5739
February 2002
D Insert the wire into each nozzle separately
from the outside as shown in figure 6-8.
D Do not try to put the wire through both nozzles
simultaneously.
D Do not push the wire on the deflector bar.
CAUTION
Do not apply force to the deflector bar
while cleaning the nozzles. Doing so
could alter the alignment or disable
the deflector mechanism.
CAUTION
Do not use chlorinated solvents for
cleaning the pilot/actuator assembly.
The chlorinated solvents will
deteriorate the rubber diaphragm

Replacing the Pilot/Actuator Assembly

1. Verify that the rubber diaphragm under the
nozzle area is blue for pilot/actuators inserted into a
direct action unit, or red for pilot/actuators inserted
into a reverse action unit.
2. Inspect the pilot/actuator assembly cavity in the
module final assembly to ensure that it is clean.
3. Lightly lubricate the two O-rings with silicone
grease, and place them in the beveled O-ring
glands. O-rings between the pilot/actuator assembly
and the module should be installed justified to the
lower portion of the O-ring gland. When properly
positioned, the air passageway should be visible
through the O-ring inside diameter.
DEFLECTOR BAR
WIRE
A6655-1/IL
Figure 6-8. Cleaning the Nozzles
WIRE
PLASTIC HOUSING
4. Prepare to insert the assembly by aligning the
key on the pilot/actuator assembly with the key slot
in the module subassembly.
5. Insert the assembly into the module
subassembly, and engage the four mounting
screws.

Module Subassembly

The module subassembly, shown in figure 6-1,
consists of the module final assembly with both the
electronic circuit board and pilot/actuator assembly
removed. The module subassembly contains the
porting and valving for the booster stage.
The module subassembly is aligned at
the factory and should not be further
disassembled. Disassembling the
module subassembly may result in
performance outside specifications.

Terminal Compartment

The terminal compartment contains the terminal
block, terminal block connection board, span and
zero screws, electrical feedthroughs, and internal
grounding lug, as shown in figure 6-9. The terminal
block connection board is attached to the terminal
block and to the electrical feedthroughs.
Separate test points are provided that have a
10-ohm resistor in series with the signal negative (–)
terminal. The test points allow the input current to be
determined with a voltmeter without disconnecting a
signal lead. A 4 to 20 mA span produces a 40 to 200
mV dc voltage drop across the 10-ohm resistor. The
test points can accommodate different connections,
including alligator clips and E–Z hooks.
Maintenance
Note
6–7