Endress+Hauser Oxymax COS22 Series - Page 24

Maintenance Oxymax COS22
24 Endress+Hauser
10.4.1 Replacing sealing rings
The sealing ring must be replaced if visibly damaged. For replacement, use only original
sealing rings.
The following O-rings can be replaced:
• Sealing ring for shaft sleeve: item 4 →  23
• Sealing ring for process: item 8
If the sealing ring on the membrane body (item 5) is damaged, you must replace the entire
membrane body.
10.4.2 Replacing electrolyte
The electrolyte is used up slowly during operation. This is caused by electrochemical
substance reactions. In de-energized state, no substance reactions take place, and the
electrolyte is not used up. The operating time of the electrolyte is shortened by diffusion of
dissolved gases such as H
2
S, NH
3
or high concentrations of CO
2
.
Theoretical operating time at p
O2
= 210 mbar and T=25 ˚C (77 ˚F)
COS22-*1 (standard sensor): > 1.5 years
COS22-*3 (trace sensor): > 3 months
L
CAUTION
The standard electrolyte is a strong irritant
Danger of severe skin and eye irritation
‣
Be absolutely certain to observe the corresponding workplace safety regulations.
‣
Wear protective clothing, gloves and goggles when handling the electrolyte.
‣
In case of eye contact: Remove contact lenses, flush eyes with water for a few minutes
and contact a doctor.
‣
In case of skin contact: Take off wet clothing immediately, wash the skin or take a
shower.
Generally, the following applies:
• Changing the electrolyte is mandatory if the membrane body is detached.
• Sensors operated close to the zero point consume hardly any chemical electrolyte. The
electrolyte does not have to be replaced for a long period.
• Sensors operated at high partial oxygen pressures (> 100 hPa) consume a significant
amount of electrolyte. The electrolyte has to be replaced frequently.
• 25 ml electrolyte are enough to fill the membrane body approx. 15 times.
Draining the electrolyte
1. Remove the sensor from the medium.
2. Clean the outside of the sensor.
3. Hold the sensor vertically and unscrew the shaft sleeve.
 The membrane body is either in the shaft sleeve or is still on the glass portion
with the anode and cathode.
4. Remove the membrane body. For this purpose, use the tool provided to push out the
membrane body.
5. Drain the membrane body and flush it with potable water.
Top up the electrolyte and install the membrane body
1. Fill fresh electrolyte from the supply bottle into the membrane body.
2. Remove all air bubbles from the electrolyte by tapping the side of the membrane body
(using a pen or pencil, for example).
3. Hold the sensor vertically and carefully push the membrane body, filled with
electrolyte, on the glass portion.