6 Maintenance
OxyMax W COS 71
18
Hauser
6.2
Regeneration
Parts of the sensor will suffer wear and tear during operation.
Suitable action can restore normal operating functionality.
This action includes:
#
Warning!
Before beginning regeneration, switch off the power supply at the transmitter.
6.2.1 Cleaning the gold cathode
The gold cathode only needs to be cleaned when it is visibly soiled or there is a coating
of silver on it.
To clean it, proceed as follows:
•
Unscrew the membrane cap from the membrane body.
•
Carefully clean the gold surface in two stages with the polishing sheet (contained in
scope of supply) until the (silver) coating is fully removed. Use the green sheet first
and then the yellow sheet.
•
Clean the electrode with drinking or distilled water.
•
Fill the membrane cap with fresh electrolyte COY 3-F and screw it back onto the mem-
brane body (up to the stop).
"
Caution!
The
counter electrode and the reference electrode
are covered with a brown silver
bromide layer at the factory.
Do not clean the counter electrode or the reference
electrode under any circumstances!
If the coating is removed as a result of operation, the sensor is unusable and must be
sent in for recoating. In this case, contact your E+H sales office.
6.2.2 Replacing the sealing ring
Replacing the sealing ring (see Fig. 3.8 on page 9, Pos. 2) is only necessary when it is
visibly damaged. For replacement, use only the supplied sealing rings COY 31-OR.
6.2.3 Replacing the electrolyte
During measuring operations the electrolyte COY 3-F is slowly used up because of
electrochemical reactions. No reactions occur in de-energised state and the electrolyte
is not used up.
The theoretical life time of an electrolyte filling for use in air-saturated drinking water at
20°C is max. 2 months. That’s why do not keep the sensor on air for a longer time (e.g.
before or after calibration). With a concentration of 1 mg/l dissolved oxygen the life time
of an electrolyte filling is approx. 1.5 years, it prolongs with less concentrations
accordingly.
If the sensor is used in other media than ultrapure water the electrolyte life time can be
shortened by diffused, dissolved gases such as H
2
S, NH
3
or high concentrations of
CO
2
.
Action
Cause
Cleaning the gold cathode
(Chap. 6.2.1)
Soiled or silver-plated gold cathode
Replacing the sealing ring
(Chap. 6.2.2)
Visual damage to the sealing ring
Replacing the electrolyte
(Chap. 6.2.3)
unstable or implausible measuring signal or electrolyte soiling
Replacing the membrane cap
(Chap. 6.2.4)
Uncleanable membrane
Damaged membrane (hole or overstretch)
Summary of Contents for OxyMax W COS 71
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