Hach-Lange 3400 sc - Manual (Page 27)

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Section 5 Maintenance
DANGER
Only qualified personnel should conduct the tasks described in this section of the
manual.
5.1 Maintenance Schedule
5.2 Cleaning the Sensor
CAUTION
Before cleaning with acid, determine if any hazardous reaction products could
form. (For example, a sensor used in a cyanide bath should not be put directly into
a strong acid for cleaning because poisonous cyanide gas could be produced.)
Acids are hazardous. Wear appropriate eye protection and clothing in accordance
with Material Safety Data Sheet recommendations.
Keep the sensor clean to maintain measurement accuracy. The time between cleaning
(days, weeks, etc.) is affected by the characteristics of the process solution and can only
be determined by operating experience.
1. Clean the exterior of the sensor with a stream of water. If debris remains, wipe with a
soft, wet cloth.
2. Remove most contaminate buildup by carefully wiping the inner electrode rod, and the
concentric outer electrode tube (inner and outer surfaces) with a soft clean cloth. Then
rinse the sensor with clean, warm water.
3. Prepare a mild soap solution using warm water and dishwashing detergent or similar.
4. Soak the sensor for 2 to 3 minutes in the soap solution.
5. Use a soft brush, cotton swab, or pipe cleaner to scrub the entire measuring end of the
sensor, thoroughly cleaning the electrode surfaces.
6. If detergent solution cleaning cannot remove surface deposits, use muriatic acid (or
another dilute acid) to dissolve the deposits. Soak the sensor in dilute acid no more
than 5 minutes.
Note: The acid should be as dilute as possible, but yet strong enough to clean. Experience will help
determine which acid to use and how dilute it can be. Some stubborn coatings may require a
different cleaning agent. For assistance in these difficult cases, contact Technical Consulting
Services.
7. Rinse the sensor with clean, warm water and then place the sensor back into the mild
soap solution for 2 to 3 minutes to neutralize any remaining acid.
8. Rinse the sensor in clean, warm water.
Maintenance Task 90 days Annually
Clean the sensor 1
1 Cleaning frequency is application dependent. More or less frequent cleaning will be appropriate in some applications.
x
Calibrate Sensor (if required by regulatory agency) Per the schedule mandated by your regulatory agency.