FCL Free Chlorine Measuring System

Feb 21, 2013

FCL Free Chlorine Measuring System
  • COMPLETE SYSTEM INCLUDES sensor, connecting cable, analyzer, and flow controller.
  • CONTINUOUS pH CORRECTION eliminates expensive and messy reagents and troublesome sample conditioning systems.
  • MEASURES FREE CHLORINE IN SAMPLES having pH as high as 9.5.
  • VARIOPOL QUICK-DISCONNECT FITTINGS make replacing sensors easy.
  • FEATURE-PACKED ANALYZER: dual outputs, three fully-programmable alarm relays, two-line display

FEATURES AND APPLICATIONS
The Model FCL free chlorine system is intended for the determination of free chlorine in fresh water. Unlike free chlorine analyzers from other manufacturers, the Model FCL does not use expensive sample conditioning system or messy reagents to control pH. Instead, the analyzer automatically compensates for changes in the pH of the sample. The Model FCL is not intended for the determination of total chlorine or combined chlorine (like monochloramine). Nor, can the FCL be used for the determination of chlorine in seawater.

The Model FCL uses a membrane-covered amperometric sensor. A polarizing voltage applied to a platinum cathode behind the membrane reduces the chlorine diffusing through the membrane and keeps the concentration of chlorine in the sensor equal to zero. The current generated by the cathode reaction is proportional to the rate of diffusion of chlorine through the membrane. Because the concentration of chlorine in the sensor is zero, the diffusion rate and the current are proportional to the concentration of chlorine in the sample.

There is a difficulty, however. Amperometric free chlorine sensors measure only hypochlorous acid. Because free chlorine is a pH-dependent mixture of hypochlorous acid and hypochlorite ion, a change in pH will cause the sensor response to change even though the free chlorine level remained constant. Most manufacturers solve the problem by treating the sample with acid, which lowers the pH and converts hypochlorite ion into hypochlorous acid. The Model FCL avoids the expense and inconvenience of sample conditioning by measuring the pH and applying a correction to the raw chlorine sensor signal. The correction is valid between pH 6.0 and 9.5.

The Model FCL is available in two options: Model FCL-01 with manual pH correction and Model FCL-02 with continuous pH correction. Choose the FCL-01 if the pH varies less than 0.2 or if pH changes are predictable or seasonal. Choose the FCL-02 if the pH varies more than 0.2. To provide the continuous pH correction, the Model FCL-02 requires a separate pH sensor.

Maintenance is fast and easy. Replacing a membrane requires no special tools or fixtures. A screw cap holds the pre-tensioned membrane in place. Replacing the electrolyte solution takes only minutes.

The Model FCL includes the easy-to-use Model 1055 analyzer. The analyzer features two fully programmable 4-20 mA outputs and three fully programmable relays. The back-lit, two line display allows the user to read sample pH and chlorine concentration at a glance.

Valves, rotameters, and pressure regulators to control sample flow are things of the past with the Model FCL. A constant head overflow sampler ensures the correct sample flow to each sensor. To eliminate wiring hassles, quick-disconnect Variopol cable is standard.

Stable free chlorine standards do not exist. The chlorine sensor must be calibrated using the results of a laboratory test run on a grab sample.

Download the FCL Datasheet