ECD FCA-22 - Applications; Components; How It Works

FCA‐22InstructionManual
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GeneralDescription
Application
TheFCA‐22isdesignedforuseindrinkingwater,industrialcoolingandrinsewaterorothersamplesof
freshwaterthatusechlorineintherangeof0‐20ppmasadisinfectant.ChlorineexistsinwaterasapH
dependent mixture of hypochlorous acid and hypochlorite ion. The sum of these two componen
ts is
referredtoasFreeChlorine,sometimesResidualFreeChlorine.
Organic chlorine compounds and chlor a mines, Bound Chlorine, are not detected by the FCA‐22. Other
measurement techniques are required for samples containing these bound chlorine chemicals. Bound
ChlorineplusFreeChlorineequalsTotalChlorine.TheFCA‐22doesnotmeasur
eTotalChlorine.
Parts
The FCA‐22 is a complete system for measuring Free Chlorine. The panel mounted system includes a
ConstantHeadFlowController(CHFC),FreeChlorinesensor(FCS)andFlowCell,pHsensor(PHS10)and
FlowCellandtheC22Analyzer.
SimplysupplypowertotheC22Analyzerandplum
bthesampleline in
andthedrainlineoutandtheFCA‐22isreadytouse.
Howitworks
TheFreeChlorine Sensor (FCS)isan amperometric sensorwitha PTFE membrane,goldcathode and a
silver/silverchlorideanode.
TheC22analyzerappliesafixedvoltageacrosstheelectrodesan
dmeasuresthecurrentflow.
Hypochlorousacid (HOCl)diffuses throughthePTFEmembraneandisreduced(gainselectrons)by the
gold cathode to chloride ion. Silver on the anode is oxidized (donates electrons) to silver chloride
completingthecurrentloop.Withstabletemperatureandsampleflow,thecurrentflowisproportional
tothefreechlorinecon
centration.
Manycompetitivechlorinesensorsrequireserviceonamonthlyorbimonthlybasis.TheFCSuses alarge
surface area  anode, combined with a large volume of electrolyte and a small cathode to provide
operationalcyclesofuptoayearwithoutrefilling.Th
ereplaceabl
ePTFEmembraneisalsodesignedfor
long term stability. A special support grid maintains a constant tension between membrane and the
cathode minimizing effects caused by varying pressures  and flow.Replacing the PTFE membrane and
rechargingtheelectrolyteiseasilyaccomplishedwithouttheuseoftools.
TheCHFCmaintainsaconstant sample flow tothepH and Chlorineflowcells. Pressure regulatorsand
rotameters are not neede
d to maintai
n a constant flow rate, the CHFC provides trouble free sample
conditioningbetwee n10and80gal/hr.
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