Hach-Lange 1720E Low Range Turbidimeter - Manual (Page 30)

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Maintenance
6.4 Cleaning
6.4.1 Cleaning the Photocell Window
Occasional cleaning of the photocell window is required. The frequency will depend on the
nature and concentration of dissolved and suspended solids in the sample. Biological
activity is a primary factor in mineral scale deposit on the window and the amount differs
with sample temperature. In general, more growth will occur in warm temperatures and
less in cold.
Note: Do not disassemble the photocell assembly. It contains liquid.
Note: Take care to not scratch the photocell window.
Inspect the photocell window often to determine cleaning needs. Remove any organic
growth or film on the photocell window before standardization or calibration. Use a cotton
swab and isopropyl alcohol or a mild detergent (such as Liqui-nox
® ) to remove most
sediment and dirt. Mineral scale buildup may require cleaning with a mild acid applied with
a cotton swab followed by a detergent wash. Do not use abrasive cleaners.
6.4.2 Cleaning the Turbidimeter Body and Bubble Trap
Sediment may collect in the turbidimeter body after extended use. Noise (fluctuation) in
the reading could indicate the need to clean the body and/or bubble trap. The 1720E
bubble trap and bottom plate may be removed to make cleaning easier. Drain and clean
the turbidimeter body before each calibration. Establish a regular schedule or perform
cleaning as determined by visual inspection.
Cleaning the Turbidimeter Body
Note: The turbidimeter body, bubble trap, and detector must be cleaned before each calibration.
1. Turn off sample flow to the turbidimeter body.
2. Remove the head assembly and bubble trap cover from the body. Remove the bubble
trap by lifting it vertically. Set it aside to be cleaned separately.
3. Drain the body by removing the plug from the bottom of the body.
4. Replace the drain plug and fill the body to the weir with cleaning solution. This
cleaning solution can consist of dilute chlorine solution (25 mL of household bleach in
3.78 liters of water) or a laboratory detergent such as Liqui-nox (1 mL detergent in
1 liter of water).
5. Use a soft brush to clean the inside surfaces of the body.
6. Remove the drain plug again and thoroughly flush the turbidimeter body with
ultra-filtered deionized water. Clean and replace the plug.
Cleaning the Bubble Trap
1. Prepare a cleaning solution (as in step 4 above) in a container large enough to
submerge the entire bubble trap.
2. Using a test tube brush such as Cat. No. 690-00, clean each surface.
3. Rinse the bubble trap thoroughly with ultra-filtered deionized water and reinstall it in
the turbidimeter body.