Page 10 - PBL883 ABB Brochure 3KXA843403R4201 OPERATING INSTRUCTIONS (OI/ACL410-EN) (16PP Q4 STITCH)

10 ACL410 | CHLORINE SENSOR | OI/ACL410-EN PILOT BUILD
5 Use of reagent feeder assembly
Measurements of total chlorine require a reagent to be added. Sometimes a reagent buffer is also needed for free residual chlorine measurements. For chlorine dioxide/ozone/ measurements, the sample conditioning is not necessary.
Measurement of free chlorine
Figure 6 identifies allowable pH fluctuations in the sample.
Normally, the measurement of free chlorine with this analyser does not require any sample conditioning. However, when the sample pH is fluctuating or it is very high, pH compensation may need to be enabled, or a pH buffering solution may be required.
When the pH increases over 6.0, the allowable variations decreases to approximately 0.5 pH units or less. The higher the pH value the lower the allowable fluctuations.
In such cases, and always when the sample pH is over 7.5, a special additive is required for pH control. ABB supplies the complete reagent feeder system, able to dose the right amount of buffer solution.
Refer to OI/AWT420 for details on configuring the UIM for pH compensation.
Figure 6 Allowable pH fluctuations in the sample, as a function of the pH value of the sample .
8
7
6
5
4
45678
Legend: SAMPLE pH
• Nohatching=Noreagent/compensationrrequired
• Grey = pH compensation required
• Squares = pH buffers required
Prepare the pH buffer Acetic acid solution
1 Weigh 2430 grams (5.36 lb) of sodium acetate tri-hydrate (CH3COONa-3H20) and dissolve it completely in 4 litres (1 gal) of distilled water.
2 Mix 4800 grams (10.58 lb) of glacial acetic acid (98-100 % CH3COOH). Continue to Stir the contents while you add the sodium acetate mixture from step 1.
3 Mix both solutions thoroughly together.
4 Gradually add distilled water until you make 10 Litres (2.6
gal) of solution.
Note . The pH value of the complete solution is abroughly 4.3 at 20 °C (68 °F).
Measurement of free chlorine
The AW400 measuring cell allows total chlorine measurements by simply conditioning the sample with reagents.
The reagent feeder for total chlorine is supplied with two 30.2 Litres (8 gal) containers. Each container is marked as "Acetic Acid" and "Potassium Iodide and Sodium Hydroxide".
To fill the containers with the prepared solution, do as follwos:
WARNING
Personal Protctive Equipment (PPE) such as gloves and eye protection must be worn when handling chemicals. Observe all health and safety procedures for handling chemicals. Failure to do this could result in serious injury or death.
1 2
Fill the Acetic Acid container with the acetic acid solution prepared in previous steps 1 to 4.
Fill the Potassium Iodide and Sodium Hydroxide container with the solution as follows:
a Dissolve 454 grams (1 lb) of sodium hydroxide pellets in 15.15 Litres (4 gal) of distilled or deionized water.
b When the sodium hydroxide has cooled to an ambient temperature, add the required quanitity of potassium iodide (Table 3).
c Mix the solution by stirring with a PVC or polyethylene rod.
Table 3
ACL410 wiring instructions
Range (ppm)
0 - 0.25
0 - 0.50
0 - 1.0
0 - 2.0
0 - 5.0
Potassium Iodide (g)
37.5 {1.32 oz}
75 {2.64 oz}
150 {5.29 oz}1
300 {10.58 oz}
750 {1.65 lb}
0 - 10.0
1500 {3.30 lb}
pH FLUCTUATIONS