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< 8. Maintenance >
8-7
IM 12F5A1-01E
8.2.3 Check/ Maintenance/ Replacement of Driven Shaft
Assembly
[Checks and Maintenance]
At zero calibration time, operate the indicator electrode and check the following (once in three
months recommended )
• Check if noisier that usual, or if vibration or non - continuous noises.
If sound is abnormal, driven shaft assembly may be bad, or problem may be in motor. Stop
electrode rotation, check if bearing at bottom of driven shaft is gone (see six - monthly check
below).
• Check if vibration in driven shaft or indicator electrode.
Usually the bushing (bearing) at the bottom is the cause. Stop the rotation and check (see
six - monthly check below).
• Manually turn the driven shaft and confirm that it’s as smooth as usual.
If there is any clatter, if drive belt has come off or shaft does not rotate easily, or a rubbing
noise is evident, promptly replace the driven shaft assembly.
[Replacing the driven shaft assembly]
If the bearing has become bad, replace the driven shaft assembly. In principle,this should be
done by Yokogawa’s service facility.
If the user wishes to replace it, the procedure is as follows:
Items (1) to (9) relate to disassembly, and items from (10) onwards relate to reassembly.
(1) Shut off the power fed to the FC400G, then place the electrode mechanism block in the
maintenance position then remove the cover from the electrode part.
(2) Remove indicator electrode and counter electrode.
To remove the indicator electrode, inset the supplied Allen wrench into the socket of the
driven shaft, to stop it from rotating.
Disconnect the three wires connected to the counter electrode, next loosen and remove the
clamp holding the electrode in its holder.
(3) Remove the drive belt. Remove the drive belt with pulleys all together installed onto the
drive shaft.
(4) Remove the rotating contact out of the driven shaft.
(5) Remove the dust protection plate installed to prevent drive belt shavings to enter the
electrode holder in the driven shaft assembly by loosening the two screws.
(6) Remove the plate which holds driven shaft assembly in place with two screws.
(7) Take out the defunct driven shaft out of the motorremove it from motor mounting plate. The
place where the electrode holder base is inserted contains an O-ring. This O-ring and the
counter electrode fixing clamp can be reused.
Note: Even if the O-ring (part no. Y9115XB) is not damaged, it is recommended to replace it after 3 years use.
The following, from item (8) below onwards, is the procedure for reassembly.
When reassembling, observe the following cautions:
• Clean any dirt off parts before reassembling.
• Adjust drive belt tension to 4 N (0.4 kgf).
• When reassembling, make sure that indicator electrode does not make contact with its
base.
(8) Assemble new driven shaft assembly on motor mounting plate. First, install the clamp and
O-ring in the electrode holder in the driven shaft assembly. Next, mount the driven shaft
assembly on the motor mounting plate, taking care not to allow the O-ring to protrude from
the hole in the base.
(9) Mount plate that holds driven shaft assembly in place. Confirm that four pins on plate
surround electrode holder and, as a temporary measure, loosely tighten the two screws in