YOKOGAWA FC400G, User Manual, Page: 72 / 91

< 8. Maintenance >
8-3
IM 12F5A1-01E
8.1.2 Cleaning the Ceramic Beads and Measuring Tank
Contaminated ceramic beads reduces the effects of cleaning of the indicator electrode, and may
possibly cause electrode contamination.
Clean the ceramic beads periodically. Also, simultaneously clean the measuring tank.
Clean them as follows:
(1) Turn OFF the power switch provided in the power line or remove the fuse provided, in the
converter to stop the free available chlorine analyzer.
Note: Be alert to the fact that even if the fuse is removed, live voltage remains on one side of the AC power line.
(2) Unscrew two screws fixing the electrode mechanism block to remove the mechanism block
from the measuring tank.
(3) Remove the beads case, containing the ceramic beads, from the measuring tank. In so
doing, remove the beads case cover together with the beads case.
(4) Clean the measuring tank.
Using a brush and neutral detergent, sufficiently remove contamination from the measuring
tank. For adhesion of manganese or iron, use diluted hydrochloric acid. Finally, wash off the
detergent from the measuring tank using water.
Note: Never attempt to use organic solvent for cleaning,
(5) Pour the ceramic beads into another container, remove contamination using diluted hydro
chlorine acid, and sufficiently wash the beads with water.
(6) Clean beads case, and beads case cover.
For the beads case and beads case cover, clean both in the same manner as measuring
tank cleaning in item (4).
Note: The beads case cover may turn whitish during prolonged use; however, it causes no functional problem.
(7) Set the beads case cover onto the beads case and pour the cleaned ceramic beads into
the beads case. If the beads have obviously become smaller in size (much smaller than a
diameter of 1.7 to 2.3 mm), replace them with new ones.
Ceramic beads are worn in long-term use, thereby reducing the ability of polishing indicator
electrode. The ceramic beads should be entirely replaced once every year.
For optimum polishing, the new ceramic beads are normally filled up to the bottommost
notch of the beads case when the indicator electrode is inserted. (The polishing ability
cannot be recovered by replenishing the beads only by volume reduced by wear.)
(8) Return the electrode mechanism block in place and firmly tighten the two fixing screws.
(9) Turn ON the power switch (or return the fuse in place) to restart operation.
8.1.3 Calibration
After polishing the indicator electrode, calibrate the zero point and span in the manner described
in Chapter 7.
It is recommended that calibration be conducted every month in the initial stage of FC400G
operation to determine the degree of contamination on the indicator electrode. This may be a
guidance for determining appropriate maintenance intervals.