Emerson TCL instruction manual Sensitivity is low or readings are low

MODEL TCL	SECTION 11
	TROUBLESHOOTING

11.5.3 Sensitivity is low or readings are low

1.Does the reagent carboy contain reagent? Is the reagent uptake tubing below the level of the reagent? Has potassium iodide been added to the acetic acid (vinegar) reagent?

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,	Amount of KI needed	Part number
ppm as Cl2	per 5 gallons of vinegar
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 unsta- ble. 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, reduc- ing 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 neces- sary. 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 10.3.3 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.

d.Start the reagent pump and collect reagent for ten minutes.

e.Note the volume of reagent collected in the graduated cylinder. After ten minutes the volume should be about 2 mL.

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