YOKOGAWA RC400G, Руководство пользователя

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<1. Outline>
1-3
IM 12F4A1-01E
The sand filter used for the raw and treated water analyzers serves to remove from sampled
water flocks which contaminate electrodes and also iron and manganese ions that liberate
iodine.
Another metering pump is incorporated in the reagent tubing to mix reagent from the reagent
tank with the sample water being fed to the measuring tank at a constant flow rate.
n
Air Tubing System
The “air tubing system” consists of air purge tubing, etc.. The air purge tubing is provided for
preventing the components of electrode drive assembly, the converter, pump drive assembly, etc.
from corrosion due to halogen gases generated from the sample water.
When an air pump is included in the system, it supplies purging air. If no air pump is attached,
connect the system through a regulating valve to a clean and dry air source like instrument air.
n
Cleaning Tubing System
The cleaning tubing system added to the raw treated water analyzers functions to clean filter
sand in the sand filter, the measuring tank and glass beads, and to remove and drain flocks.
Cleaning is automatically carried out by opening and closing the solenoid valve in cleaning water
tubing with sequence signals from the converter. The cleaning water tubing is also provided with
a regulating valve to adjust the cleaning water pressure.
n
Automatic Zero Calibration Tubing System
The residual chlorine analyzer with automatic zero calibration performs zero calibration using an
activated charcoal filter. In the automatic zero calibration, the solenoid valve SV6 is opened and
closed by a sequence signal from the converter.
1.2 Operating Principle of RC400G Residual
Chlorine Analyzer
The measuring object of the RC400G residual Chlorine Analyzer is either free available chlorine
or combined available chlorine.
Free available chlorine exists in the forms of chlorine (Cl
2
), hypochlorous acid (HClO), or
hypochlorite ion (ClO
-
) in water. Combined available chlorine exists in the from of chloramines,
such as trichloramine (NCl
3
) and dichloramine (NHCl
2
), generated through reactions of chlorine
with ammonia nitrogen from contaminants in polluted rivers and other sources.
The residual chlorine analyzer operates on the principle of rotating electrode polarography.
Measurement of free available chlorine content or total residual chlorine content including free
and combined available chlorine contents can be performed by adequate selection of reagent,
electrode and applied voltage.
For measurement of total residual chlorine, reaction of chlorine with sample water added with
potassium iodide (KI) is implemented. Since KI is dissociated into K
+
and I
-
in aqueous solution,
the iodine equivalent to the amount of residual chlorine is liberated as shown in equations (1), (2),
(3) and (4).
Free available chlorine Cl
2
+ 2l
-
l
2
+ 2Cl
-
........................................ (1)
NH
2
Cl (monochloramine) + 2l
-
+ 2H
+
l
2
+ NH
4
Cl ................................ (2)
Combined available chlorine NHCl
2
+ 4l
-
+ 3H
+
2l
2
+ NH
4
Cl + Cl
-
........ (3)
NCl
3
+ 6l
-
+ 4H
+
3l
2
+ NH
4
Cl + 2Cl
-
................ (4)
The iodine concentration (indirectly chlorine concentration) is determined by applying a voltage
across the indicator and counter electrodes to conduct electrolytic reduction of the free iodine and
simultaneously measuring the current.
14th Edition : Jul. 15, 2020