2. Is there adequate flow to the overflow sampler? Excess sample should be flowing
down the inside tube of the overflow sampler.
3. Does the reagent contain the correct amount of potassium iodide? See the table.
Expected range, ppm as Cl
2
Amount of KI needed per 5
gallons of vinegar Part number
0-5 ppm 25 grams 24164-00
0-10 ppm 50 grams 24164-01
0-20 ppm 2 x 50 grams 24164-01
4. Was the comparison or calibration sample tested as soon as it was taken? Chlorine
solutions can be unstable. Test the sample immediately after collecting it. Avoid
exposing the sample to sunlight.
5. Is the membrane fouled or coated? A dirty membrane inhibits diffusion of iodine
through the membrane, reducing sensor current. Clean the membrane by rinsing it
with a stream of water from a wash bottle. Wipe gently with a soft tissue.
6. Are the reagent and sample pumps running? If a pump is not running, check the fuse
and replace it if necessary. See Table 10-2 for part numbers. If the fuse is okay,
replace the pump.
7. Are all tube fittings tight? Pay particular attention to the luer fittings that connect
the tubing to the pumps.
8. Does the pump tubing element need replacing? Remove the tubing from the pump
and inspect it. If the tubing appears permanently pinched or deformed, replace the
tubing. Refer to Section 10.3.4 for instructions on how to remove and replace the
tubing elements. The expected life of a tubing element is about one year.
9. Is the sample flow to the sensor about 11 mL/min? If the sample flow is too low, the
total chlorine reading will be low. If the flow is too high, the ratio between the
sample flow and reagent flow will be too high, and there might be insufficient
reagent to properly react with the total chlorine in the sample. To check sample
flow:
a. Turn off the reagent and sample pumps.
b. Disconnect the luer fitting on the discharge of the sample pump. See A in
Figure 11-1.
c. Hold a small beaker under the discharge port.
d. Start the sample pump and collect sample for two minutes.
e. Measure the volume of sample collected in the beaker. After two minutes, the
volume should be about 22 mL.
10. Is the reagent flow about 0.2 mL/min? If the reagent flow is too low, there might be
insufficient acetic acid to lower the sample pH and insufficient potassium iodide to
react with total chlorine in the sample. To check reagent flow:
a. Turn off the reagent and sample pumps.
b. Disconnect the reagent tubing at the injection tee. See B in Figure 11-1.
c. Place the end of the tubing in a 5 mL graduated cylinder.
Troubleshooting
92 Rosemount TCL
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