3660 and 3661 Positioners
Instruction Manual
Form 5265
March 2006
28
11B3925-B/DOC
Figure 23. Type 3660 Bypass Valve
the flapper, be sure the end of the flapper engages
the grove in the end of the screw, and that the
flapper spring (key 10) sets into the V-notches of the
flapper.
9. With the flapper (key 9) in place, visually ensure
that it is aligned parallel to the cover plate assembly
(key 8) as shown in figure 22. Realign if necessary
by repositioning the flapper spring (key 10). The
flapper alignment affects the performance of the
positioner. Be careful not to damage the lapped
surfaces on the cover plate and nozzle.
10. Reinstall the range spring (key 30). Push the
feedback lever assembly (key 19) back into position
and retighten the retaining screw (key 19P).
11. With the output at supply pressure, check the
output diaphragm assembly joints for leaks.
12. Refer to the Calibration section for the
calibration procedure.
Disassembling and Assembling the
Bypass Valve
WARNING
Refer to the Maintenance WARNING at
the beginning of this section.
During the following bypass valve disassembly and
assembly procedures, refer to figure 23, unless
otherwise indicated.
1. Remove all pressure from the positioner.
Disconnect the supply, instrument and output tubing.
2. Remove the two cheese head screws (key 47).
Lift the bypass valve from the positioner being
careful not to loose the three O-rings (key 49).
3. Remove the plastic wire tie (key 79) and retaining
ring (key 46).
4. Using a gentle pulling and turning motion, slide
the bypass lever assembly (key 42) from the bypass
body (key 41).
5. Inspect the O-rings (keys 43, 44, 45 and 49) for
nicks and wear, and replace as necessary. When
installing new O-rings (keys 43, 44 and 45) on the
shaft of the bypass lever assembly, lubricate them
sparingly using lubricant (key 48).
6. Install the bypass lever assembly (key 42) into
the body assembly (key 41) using a gentle turning
and pushing motion to avoid nicking an O-ring.
7. Install the retaining ring (key 46).
8. Install the three O-rings (key 49) into the body
assembly (key 41) and then carefully attach the body
assembly to the positioner using the two cheese
head screws (key 47).
9. Turn the bypass lever (key 42) to the appropriate
POSITIONER or BYPASS position, and secure with
the plastic wire tie (key 79).
10. Reconnect the supply, instrument and output
tubing, and turn on pressure to the positioner.
Replacing the Type 3661 Converter
Module
Refer to figure 25 for key number locations. After
replacing the converter module, re-calibrate the
positioner.
1. Remove the cover and disconnect the input
signal wires from the terminal strip.
2. Loosen the two captive screws securing the
converter to the positioner housing, and lift out the
converter module (key 100).
3. When replacing the converter module, the
restrictor assembly (key 35) also should be replaced.
Before the restrictor assembly can be removed,
remove the positioner from the actuator. Refer to the
Removing the Positioner from the Actuator section.
4. Remove and replace the restrictor assembly (key
35). This assembly is marked with the letters EP on
the removal screw. For location purposes, the same
letters appear on the back of the positioner case.
