Actuator Removal; Seal And O-Ring Replacement - Fisher 685 Instruction Manual

685 Piston Actuator
May 2013

Actuator Removal

The following procedure is for the removal of the actuator from a valve.
1. Disconnect the cylinder tubing from the upper and lower heads (keys 1 and 9) and positioner.
Note
Refer to the appropriate instruction manual for any maintenance or adjustments that need to be made on the positioner.
2. Break the stem connection by removing hex head cap screws (key 20) and lock washers (key 10) from the stem
connector (key 18).
3. Refer to the Actuator Mounting section of this manual for instructions on mounting and installing the actuator onto
a valve
Seal and O­ring Replacement
The following procedure is for the replacement of the internal piston seals, bearing seals, and O­rings.
1. Complete Actuator Removal procedures above.
2. Remove the lower head (key 9) from the yoke (key 21) by removing hex head cap screws (key 20) and lock washers
(key 10).
3. Loosen tie bolt hex nuts (key 11) in a crisscross pattern. Remove tie rod hex nuts and lock washers (key 10).
4. Remove lower head (key 9) from cylinder (key 4) and place onto a flat surface with the O­ring side facing up.
5. Extract bearing assembly (keys 12, 13, 14, and 15) from lower head (key 9) by removing the bearing retaining ring
(key 16).
6. Remove the piston wiper seal (key 15), O­ring (key 13), and quad seal (key 12) from the bearing (key 14).
7. Clean bearing (key 14) with a light degreaser, if needed.
8. Lightly grease the new O­ring (key 13) and quad seal (key 12), then install onto bearing (key 14). Without grease,
install a new piston wiper seal (key 15) onto the bearing.
9. Reinstall bearing assembly (keys 12, 13, 14, and 15) into lower head (key 9) and secure in place with the bearing
retaining ring (key 16).
10. Remove the O­ring (key 2) from the lower head (key 9) and clean the groove with a light degreaser.
11. Lightly grease the new O­ring (key 2) and install on lower head (key 9).
12. Remove tie bolts (key 3) from upper head (key 1).
13. Lift piston assembly (keys 5, 6, 7, 17, and 19) out from cylinder (key 4) and place on a flat surface.
14. Remove the wear ring (key 6) and quad seal (key 7) from the piston (key 5).
15. Thread locking compound is applied to the threads by the manufacturer during initial assembly. As a result,
disassembly will require heating to loosen the thread locking compound. To remove the piston rod O­ring (key 19),
heat the piston assembly using a torch and unthread the piston rod (key 17) from the piston (key 5).
16. After the piston rod (key 17) has completely cooled, remove the piston rod O­ring (key 19). Clean the piston rod
O­ring groove with a light degreaser. Lightly grease a new piston rod O­ring and install onto the piston rod.
17. Reinstall piston rod (key 17) onto piston (key 5) using thread locking compound.
18. Clean piston seal grooves. Install new lightly greased quad seal (key 7) onto piston (key 5).
8
Instruction Manual
D103626X012