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<6. INSPECTION AND MAINTENANCE>
6-2
IM 12F5A2-01E
CAUTION
Do not touch the rotating shaft brush, slip ring, or the indicator electrode surface.
(7) Mount the electrode assembly cover and restore the electrode assembly in the measuring
tank. Tightly secure the assembly using the two fixing screws.
(8) Turn the converter power switch ON and confirm that the indicator electrode revolves
normally. Also confirm that the concentration display presents an approximately proper
value.
(9) Mount the converter cover.
In addition, after the electrode is polished, perform running-in operation for one hour or
longer. Then, calibrate span without fail.
Note: Polish the electrode surface (gold electrode) by following the instructions below when it has become corrugated or deformed
from the original shape (about 3 mm in diameter).
Polish the electrode surface with sandpaper (about #600) until the surface becomes finally rounded. Then, polish it with
sandpaper (about #2000), and lastly with polishing powder (alumina). Make sure the electrode surface is clean and then install
the indicator electrode. Reduce the amount of ceramic beads if the electrode has deformed greatly. The ceramic beads should
be filled up to 5 mm under the bottommost notch of the beads case when the indicator electrode is inserted.
6.1.2 Glass Beads and Measuring Tank Cleaning
If the glass beads are contaminated, cleaning effect deteriorates. Periodically clean the glass
beads and the measuring tank.
The procedure follows:
(1) Turn OFF the converter power switch. Stop sample water supply.
(2) Remove the two fixing screws of the electrode assembly and secure the assembly to the
holding studs.
(3) Remove the beads case from the measuring tank with the rubber packing attached. In this
case, exercise care so as not to drop glass beads into the measuring tank.
(4) Clean the inside of the measuring tank using a brush with detergent on it. Use dilute
hydrochloric acid if manganese or iron adheres. Do not use organic solvent.
After cleaning, completely wash out the detergent (or acid) using clean water or sample
water.
(5) Move the glass beads to another vessel and clean them using dilute hydrochloric acid.
After that, completely wash out the acid using clean water or sample water. For the beads
case and rubber packing, remove dirt using detergent or dilute hydrochloric acid. After that,
completely wash out the detergent or acid using clean water or sample water.
(6) Set the beads case to the rubber packing and load the cleaned glass beads in the 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. Glass beads are worn in long-term use, thereby
reducing the ability of polishing indicator electrode.
For optimum polishing, the new glass beads are normally filled up to the bottommost notch
of the beads case when the indicator electrode is inserted (See Figure 4.2). The polishing
ability cannot be recovered by replenishing the beads only by volume reduced by wear.
(7) Restore the beads case and rubber packing in the measuring tank.
(8) Restore the electrode assembly to the measuring tank and secure it using the two fixing
screws.
(9) Supply sample water. Turn ON the converter power switch. Confirm that the indicator
electrode normally revolves and the concentration display presents approx. the proper
value. Finally, mount the converter cover.
The cleaning effect of the glass beads deteriorates owing to abrasion of the beads
themselves over prolonged use. Recommended practice is to replace the beads once or
twice a year.