YOKOGAWA FC400G, User Manual, Page: 75 / 91

< 8. Maintenance >
8-6
IM 12F5A1-01E
(2) Remove the two pulleys of the drive shaft (cell motor shaft) and driven shaft (indicator
electrode-mounting shaft).
The driven shaft pulley can be removed by inserting a 2 mm nominal size Allen wrench
(accessory) into the hole in the shaft, which is used as a lock, and unscrewing the end of the
driven shaft. The drive shaft pulley can be removed by unscrewing two set screws using a
1.5 mm nominal size Allen wrench (accessory).
Remove the pulleys together with the drive belt.
(3) Unscrew the screws fixed on the terminal block of Rotating contact. Unplug the cable
terminals of Rotating contact. Remove Rotating contact from Driven shaft. Hold a new
rotating contact, with its metal top facing toward you, while the cable being on your right
side. Then put the driven shaft throught the center hole.
(4) Install the pulleys and drive belt in place.
(Note) Mount drive shaft pulley so that the tip of the shaft can project out 0.3 to 0.7 mm from the end of the pulley.
(5) Install wiring terminals of Rotating contact on the block terminal of Rotating contact. Be sure
that the wiring never contacts the drive belt.
(6) Feed power to FC400G. Confirm that the driven shaft/drive shaft/drive belt/rotates smoothly,
and that there are no abnormal sounds, like vibration or discontinuous noises.
This completes the replacement procedure.
CAUTION
When you shut the cover of electrode mechanism, be careful not to get the cables caught that
run inside the analyzer.
8.2.2 Check / Maintenance / Replacement of Drive Belt
When you polish the indicator electrode, and remove the electrode mechanism block cover for
maintenance, check the drive belt as follows (once in three months recommended).
• Check for powder (from drive belt friction) deposited on motor mounting plate and the like.
As the drive belt ages, and the mating of the teeth on the pulley with the teeth on the drive
belt worsens, the amount of powder deposited increases.
• When the driven shaft pulley is rotated clockwise or anticlockwise, its small “play” causes
the drive pulley to rotate. If the drive belt loosens and cannot transmit enough traction, the “
play” becomes larger.
Once in six months you should perform the following checks and maintenance:
• Check if aging of the drive belt has caused cracking. If there is serious cracking, replace it.
• Check if the drive belt teeth are badly worn. If so, replace it.
• Check if powder from the drive belt is stuck to drive shaft or driven shaft.
If this powder is adversely affecting pulley operation, remove for cleaning. When cleaning
the pulley, also clean powder from the drive belt off the motor mounting plate.
[Replacing the Drive Belt]
When replacing the drive belt, the tension in the drive belt needs to be adjusted or the drive
belt like may be adversely affected. Because this adjustment is rather time - consuming and
troublesome, it is recommended that, where possible - except when the drive belt is no longer
rotating the electrode reliably, and needs to be urgently fixed - the driven shaft assembly and
motor be replaced at the same time as the drive belt.
If you want to replace just the drive belt, refer to Sec. 8.2.3 (12) and (13).