Metex 8760CLP Total Free Chlorine & pH Analyzer - Manual (Page 34)

AQUAMETRIX INC.
1-800-742-1413 www.aquametrix.com
34
Monthly Maintenance
Remove the sensor from the flow cell, rinse in water, remove any significant deposits, and then check by
calibration in 7 pH for offset and then 4 pH or 10 pH buffer for slope.
If the calibration turns up a caution or error message in the 8760CL analyzer, then follow the
appropriate solution. Also, refer to Troubleshooting section.
If the calibration is good, keep a log of the pH offset and slope at each monthly calibration.
The pH sensor is now ready to return to service.
Yearly Maintenance
Check the pH offset log. If the pH offset has changed more than 30 mV over the past year, it may need
to be chemically cleaned – follow the Chemical Cleaning of Sensor procedure.
Check the pH slope (efficiency) log. If the efficiency has dropped below 85%, it may need to be
chemically cleaned and restored – see Chemical Cleaning of Sensor and/or Restoring Electrode
Response in the Troubleshooting section.
After all the above checks, plus chemical cleaning and/or restoring procedures, follow the monthly
maintenance procedure. Start a new log with the improved values.
When to Clean Sensors
Various factors can affect the pH reading; scale, biological growth, oil, wax, gum, etc., all reduce the
area for hydrogen ion to react with the glass. Biological microbe growths can also produce local pH
environments inside their growth deposit, which can be quite different from the true process pH.
Periodic cleaning of pH sensors will remove these deposits, restore the pH glass surface, reference
junction and thus the pH accuracy.
Mechanical Cleaning of Sensor
The sensor will require cleaning if sludge, slime, or other deposits build up in the internal cavities of the
sensor.
Wherever possible, clean with a soft brush and detergents. General debris, oils, films, biological
growths, and non-tenacious deposits can be removed in this way.
Use a soft flat brush and a beaker or bucket of water with a good liquid detergent. Take care not to
scratch the pH electrode glass surface; it is thin, fragile and easily broken.
All the wetted surfaces of plastic body sensors should be washed with a soft cloth. This will return their
appearance to like-new condition and remove sites for buildups to occur.
When to Chemical Cleaning
After mechanical cleaning, as above, check the sensor against a pH buffer. If the sensor is still not
developing the pH reading properly in the pH buffer, proceed to the Chemical Cleaning procedure;
otherwise return the sensor to the process.