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Instruction Manual
D200156X012
4194HA, HB, HC Controllers
July 2018
56
Replacing the Flapper Assembly and Flexure Pivot Assembly
Note
Before starting the following procedure, remove the controller from the case. Perform steps 1 through 7 of the Replacing the
Differential Pressure Unit procedure. Then, perform steps 1 and 2 of the Replacing the Case and Cover procedure.
1. Perform the procedures required in the Note above.
2. Remove the two screws and lift off the proportional band indicator cover.
3. Disconnect link 3 from the set point beam shoe. Refer to figure 5‐9 for link location.
4. Remove the set point beam bias spring. Refer to figure 5‐9 for the spring location.
6. Remove the set point pivot assembly.
7. Disconnect the nut holding the relay nozzle tubing (key 18, figure 5‐9) into the frame.
8. While holding the proportional band knob, remove the screw and washer (keys 19 and 20, figure 5‐12) which holds
the relay nozzle tubing assembly (key 18) to the frame manifold (key 135).
9. Remove the proportional band knob nozzle pivot, relay nozzle tubing assembly, and set point beam assembly from
controller.
10. Disconnect link 2 from the input feedback beam assembly (key 11) shown in figure 5‐7.
11. Disconnect link 4 from the bellows bracket (key 31).
12. Remove the two screws (key 12) that hold the flexure pivot assembly (key 9) to the input feedback beam assembly.
See figure 5‐13 for screw location.
13. Remove the input feedback beam assembly as shown in figure 5‐14.
15. Remove the flexure pivot assembly (key 9).
16. Install the replacement flexure pivot assembly with the four screws (key 10). Do not tighten the screws.
17. Move the flexure pivot assembly towards the relay as far as possible and tighten the four screws (key 10).
18. Place the input feedback beam assembly (key 11) onto the flexure pivot assembly (key 9) with link 4 through the
square hole in the frame.
19. Install the screw (key 12) with the washer (key 13) through the input feedback beam assembly (key 11) into the
flexure pivot assembly (key 9). Do not tighten the screw.
Tighten the screw (key 12). Make sure link 4 does not touch the frame.
Note
The following procedure (steps 22 through 24) adjusts link 2 so it will always be in tension. This eliminates possible instability due
to lost motion.
21. Disconnect link 1 (figure 3‐1) from the drive arm/pivot assembly and manually position the process indicator to 100
percent of the scale. Tape the indicator in position.