Hach 6120118 - Manual (Page 34)

34
Maintenance
6.2 Cleaning the Sensor
CAUTION
Before cleaning with acid, determine if the chemical reaction between the acid and
the sample will create a hazardous chemical reaction. (For example, do not put a
sensor that is used in a cyanide bath directly into a strong acid for cleaning
because this chemical combination may produce poisonous cyanide gas.)
DANGER
Acids are hazardous. Always wear appropriate eye protection and clothing in
accordance with material safety data sheet recommendations.
1. Clean the exterior of the sensor with a stream of water. If debris remains remove
loose contaminate buildup by carefully wiping the entire measuring end of the sensor
with a soft clean cloth. Rinse the sensor with clean, warm water.
2. Prepare a mild soap solution of warm water and dish detergent or other non-abrasive
soap that does not contain lanolin.
Note: Lanolin will coat the glass process electrode and can adversely affect sensor performance.
3. Soak the sensor for 2 to 3 minutes in the soap solution.
4. Use a small soft-bristle brush and scrub the entire measuring end of the sensor,
thoroughly cleaning the electrode and reference junction surfaces. If surface deposits
cannot be removed by detergent solution cleaning, use muriatic acid (or other dilute
acid) to dissolve them. The acid should be as dilute as possible, do not use 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. For
assistance, contact
Technical and Customer Service (U.S.A. only) on page 39 .
5. Soak the entire measuring end of the sensor in dilute acid for no more than 5 minutes.
Rinse the sensor with clean, warm water then place the sensor back into the mild
soap solution for 2 to 3 minutes to neutralize any remaining acid.
6. Remove the sensor from the soap solution, and rinse the sensor again in clean, warm
water.
7. After cleaning, always calibrate the measurement system. Refer to section 4.7 on
page 25 or section 4.8 on page 29 .