Hach ORBISPHERE 31 Série Manuel D'utilisation Simplifié page 14

6.2 Electrochemical cleaning and regeneration center
The ORBISPHERE 32301 is a very efficient cleaning and regeneration tool for electrochemical
sensors. This tool reverses the electrochemical process that is taking place in the sensor cell during
normal operation. This removes oxidation and at the same time regenerates the surface of the
electrodes. In addition, the regeneration center offers a continuity tester for checking the sensor
electronics.
Use of this tool is recommended for a noticeably extended sensor life. Detailed information on how to
use the cleaning and regeneration center is included in the 32301 Operator Manual.
Note: It is mandatory to use the 32301 Sensor Cleaning and Regeneration Center for servicing electrochemical H
sensors. This process is called dechloridization and rechloridization of the electrodes (see
cleaning on page 17).
6.3 Chemical cleaning: oxygen and ozone sensor cell
Note: Not applicable for H
The following supposes that the sensor has been taken apart. For disassembly and assembly
procedures, see Disassembly and assembly
Conditions
Wear on the membrane, and chemical reactions within the sensor, requires that the sensor be
serviced regularly to restore its original sensitivity. Service includes electrode cleaning and
membrane replacement. A clear sign that a sensor maintenance is required is when measurements
are noticeably less stable than usual, and when a calibration does not improve the situation.
Method description (see following step-by-step procedure)
• Electrochemical cleaning with 32301 (if available)
... when not available or results are insufficient.
... for sensors used in harsh environments (e.g., hydrocarbon industry) or very dirty sensors.
• Anode and cathode chemical cleaning
• Central electrode polishing
• Final rinsing
Note: To eliminate any silver residue that ammonia cleaning cannot remove, it is sometimes required to repeat the
chemical cleaning using nitric acid (HNO
6.3.1 Membrane support cleaning
1. Empty and rinse the electrolyte reservoir
under tap water.
2. Rinse membrane support under water and
wipe it dry.
3. Check for the presence of any residue on the
surfaces. Residue can be removed by
placing the support in a container of nitric
acid (HNO , not over 70% by weight) until it
3
recovers its original appearance (normally
within 30 seconds).
Note: Only use nitric acid to clean very dirty membrane
support.
4. Rinse one minute under tap water and check
again for surface cleanliness.
Nitric acid is dangerous! Please refer to the safety information from your chemical supplier.
6.3.2 Electrodes ammonia cleaning
Note: Only use ammonia to clean very dirty sensors.
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sensors.
2
, not over 70% by weight).
3
C A U T I O N
on page 11.
2
Hydrogen sensor cell