Maintenance Schedule - Hach pHD Sensor User Manual

Maintenance
Personal injury hazard. Only qualified personnel should conduct the tasks described in this section of the manual.

Maintenance schedule

Maintenance task
Clean and inspect the sensor
Replace the standard cell solution and salt bridge
Replace the sensor
Clean the sensor
Chemical hazard. Always wear personal safety protection in accordance with the Material Safety Data Sheet for
the chemical that is used.
Examine the sensor periodically for debris and deposits. Clean the sensor when there is a buildup of
deposits or when performance has degraded.
Pre-requisites: Prepare a mild soap solution with a non-abrasive dishwashing detergent that does
not contain lanolin. Lanolin leaves a film on the electrode surface that can degrade the sensor
performance.
1. Turn off the flow.
2. Loosen the lock ring and remove the pH sensor from the flow cell.
3. Rinse the sensor with a stream of clean, warm water. If debris remains, carefully wipe the entire
measuring end of the sensor with a clean, soft cloth to remove the loose contaminate buildup.
Then rinse with clean water.
4. Soak the sensor for 2 to 3 minutes in the soap solution.
5. Use a soft bristle brush and scrub the entire measuring end of the sensor, thoroughly cleaning the
electrode and salt bridge surfaces.
6. If surface deposits remain, soak the measuring end of the sensor in dilute acid, such as muriatic
acid (or other dilute acid), for a maximum of 5 minutes.
Note: The acid should be as dilute as possible, not stronger than 3% HCL. Experience will determine which
acid to use and the appropriate dilution ratio. Some stubborn coatings may require a different cleaning agent.
Contact technical support.
7. Rinse the sensor with water and return to the soap solution for 2 to 3 minutes to neutralize any
remaining acid.
8. Rinse the sensor with clean water.
9. Calibrate the sensor in a beaker using a reference solution(s).
10. Install the pH sensor in the flow cell and tighten the lock ring.
C A U T I O N
Frequency
90 days
(The pH sensor may need to be cleaned more often
depending on water quality.)
3 to 6 months
4-5 years
W A R N I N G
English 15