Replacing The Electronic Circuit Board; Pilot/Actuator Assembly; Action; Removing The Pilot/Actuator Assembly - Emerson Fisher 846 Instruction Manual

Type 846 and Model 3311
CORRECT POSITION
INCORRECT POSITION
A6653/IL
Figure 6-6. Positioning the Pressure Sensor
with the cavity in the module subassembly. The
current design does not require the sensor seal
washer; therefore, the sensor seal washer may be
discarded when switching from the previous design
electronic circuit board to the current design.

Replacing the Electronic Circuit Board

1. Verify that the circuit board is green for assembly
into a direct action unit, or red for assembly into a
reverse action unit.
2. Ensure that the three O-rings are in the proper
position. The small O-ring is positioned in the
beveled O-ring gland of the module subassembly.
The two sensor O-rings are each positioned on the
shoulders of the sensor. They should be lightly
lubricated with silicone grease.
3. Ensure that the pressure sensor is correctly
positioned against the manifold. The pressure
sensor should be centered and in contact with the
manifold, as shown in figure 6-6.
4. Position the circuit board on the module
subassembly. Ensure that the circuit board mounting
holes match those on the module subassembly.
Place the three long screws in the mounting holes
adjacent to the pressure sensor.
5. Place the two short screws in the remaining
mounting holes. Tighten the three long screws first,
then tighten the remaining two screws.

Pilot/Actuator Assembly

The pilot/actuator assembly is located at the bottom
of the module final assembly, as shown in figure 6-1.
It is a unitized assembly consisting of the coil,
magnet, and spring of the actuator, and the deflector
and nozzles of the pilot stage. Two O-rings are part
of the pilot/actuator assembly. Table 6-1 shows the
O-ring sizes. They are located in the beveled O-ring
6–6
ELECTRONIC
CIRCUIT
BOARD
MANIFOLD
SOLID STATE
PRESSURE SENSOR
ELECTRONIC
CIRCUIT
BOARD
MANIFOLD
ALIGNMENT
KEY
RUBBER
DIAPHRAGM
MOUNTING
SCREWS
A6654/IL
Figure 6-7. Pilot/Actuator Assembly (Bottom View)
glands of the module subassembly, adjacent to the
nozzles. The pilot/actuator assembly is held in place
by four mounting screws.

Action

A blue rubber diaphragm under the deflector bar and
nozzle area identifies the direct action pilot/actuator
assembly. A red diaphragm under the nozzle area
identifies the reverse action pilot/actuator assembly.
Figure 6-7 shows the bottom view of the
pilot/actuator assembly.

Removing the Pilot/Actuator Assembly

To remove the pilot/actuator assembly, disengage
the four mounting screws, and gently pull the
assembly out of the module subassembly. To aid
removal, the pilot/actuator framework may be gently
gripped with a pair of pliers.
WARNING
Personal injury or property damage
could result from an uncontrolled
process. Do not attempt to remove the
pilot/actuator assembly by gripping or
pulling on the deflector or nozzles.
Doing so could alter the alignment or
disable the deflector/nozzle
mechanism.
Inspect the assembly for a buildup of foreign
material. The nozzle passageways should be clear,
and the deflector should be clean. The deflector can
be cleaned by spraying it with-contact cleaner.
Clean the nozzles by gently inserting a wire with a
maximum diameter of 0.38 mm (0.015 inches).
Instruction Manual
Form 5739
February 2002