Replacing The Diaphragm; Replacing The I/P Unit Filter; Removing The Positioner - Fisher 4070 Instruction Manual

DIAPHRAGM COVER
SCREW
A7233 / IL
Figure 14. Diaphragm
3. Check the O-rings, then secure and install the pilot
valve assembly to the positioner housing and secure it
with the screw. Make sure that the leaf spring on the
balance arm is properly fitted in the spool groove.
4. Check again to insure smooth operation of the as-
sembly.

Replacing the Diaphragm

Refer to figure 14. For Type 4070 electro-pneumatic
positioners, the I/P unit must be removed to access
the diaphragm.
1. Loosen the four screws and remove the diaphragm
cover.
2. Loosen the screw that secures the diaphragm. Re-
move the diaphragm and washers.
When installing the diaphragm make sure to place one
washer on each side of the diaphragm. Make sure that
the raised circle on the washers is facing the dia-
phragm.
3. Install the screw and tighten.
4. Check the O-ring on the diaphragm cover, then
install and secure the cover with the four screws.
SCREWS
WASHERS DIAPHRAGM
Type 4060 & 4070
FILTER
O-RING
A7234 / IL
Figure 15. Filter Replacement
Replacing I/P Unit Filter
CAUTION
Do not operate the unit without filter
and filter plug installed. Do not attempt
to unscrew filter plug while positioner is
pressurized.
The I/P unit on the Type 4070 positioner is equipped
with a built in secondary filter located on the side of
the I/P unit.
For replacement or inspection, refer to figure 15. Make
sure the positioner unit is not pressurized, then un-
screw the filter plug. Remove the filter and install a
new one into the filter plug . Check the condition of the
O-ring and filter compartment. If moisture is found,
check upstream filters and oil-and-water separators.
Moisture can cause the I/P unit to fail. Reinstall the
filter plug.

Removing the Positioner

1. Shut off supply pressure and process lines to the
positioner.
2. Disconnect pneumatic and, if necessary, electrical
connections.
3. Remove the screws that attach the positioner to
the mounting bracket and remove the positioner.
FILTER PLUG
11