pH Probetype pH Reiner

Operating Instructions

386-5 e

Contents1 Preface2 General instructions2.1 Operatingrange2.2 Warningscontainedintheoperatinginstructions2.3 Notesondeliveries2.4 Transportandstorage2.5 Warrantynotes2.6 Notesonreturndeliveries2.7 GlassTesting3 Safety3.1 Properuse3.2 Qualifiedpersonnel4 Technical description4.1 Featuresandproperties4.2 Measuringprinciple4.3 Constructionandfunction4.4 Electrolytereservoir4.5 Referenceelectrode4.6 Electrolyte4.7 Threadadapter4.8 Installationadapter4.9 Technicaldata5 Technical characteristics of measurement5.1 Slopeofthemeasuringchain5.2 Zeropointofthemeasuringchain5.3 Intersectionofisotherms5.4 Resistanceofthemeasuringchain5.5 Diaphragmresistance5.6 Measuringvariance5.7 Alkalierror5.8 TimeresponsetopHchange5.9 Timeresponsetotemperaturechanges6 Application limits6.1 Chemicalresistance6.2 Temperature6.3 pHrange6.4 Pressure6.5 Inappropriateproducts

7 Installation and electrical connection of the probe

7.1 Installationoftheprobe7.2 Installingtheelectrolytereservoir7.3 Electricalconnectionoftheprobe7.4 Equipotentialbonding7.5 pHReinerconnectioncord7.6 ListofpHtransmittersapprovedby

Pfaudler8 Start-up and calibration8.1 Preliminarynote8.2 Reconditioningtheprobe8.3 Disinfectingtheelectrolytesystem8.4 Fillingtheelectrolytereservoirandvent-

ingoftheprobe8.5 SettingthepHtransmitterparameters8.6 Whatismeantbycalibration?8.7 Calibrationmethods8.8 CalibrationbydatainputatthepH

transmitter8.9 Two-pointcalibration8.10 Single-pointcalibration8.11 Automaticcalibration8.12 Compressedairsetting9 Operation and maintenance9.1 Recalibration9.2 Replacingtheelectrolytebottle9.3 Electrolyteconsumption9.4 Cleaningandsterilizationoftheprobes9.5 Troubleshooting9.6 Sparepartslist

Annex A Installation adapter assembly

TYPE ELAUGUST 2006

2 ©PfaudlerGmbH

pH Probetype pH Reiner

1 PrefaceTheseoperatinginstructionsaredesignedtofamiliarizeuserswiththeequipmentofthepHprobeanditsuse.

The operating instructions should beaccessible to the operating and main-tenancepersonnelinordertoensurethatallnecessary information isavailable foranyassemblyandmaintenancework.

Byknowingtheseoperating instructions,youcanavoiddamagetothemeasuringequipmentandensuretrouble-freeopera-tion.

The information contained in theseoperatinginstructionscorrespondstothestateoftheartatthetimeitisprintedandisprovidedtothebestofourknowledge.We reserve the right to include anyimprovements, amendments and newdevelopments in the operating instruc-tions without prior notice. The actualdesign of products may differ from theinformation provided in the operatinginstructions if warranted by technicalmodifications resulting from productimprovements. The proposal submittedbyPfaudlerforaconcreteapplicationwillbebindinginthiscase.

Thelatesteditionwillalwayssupersedeallpreviousones.

The present operating instructions aremade available to our customers andinterestedpartiesfreeofcharge.Reprintsandcopiesaswellastransformationintoelectronicforms,inwholeorinpart,shallrequireourwrittenapproval.

Allrightsreserved.

2 General instructions

2.1 Operating rangeTheglassteelpHReinerprobesareusedto measure the pH value of a solution.ThepHvalueisameasureofthestrengthof an acid or an alkali solution. The pHReinerprobecanbeinstalleddirectlyinapipelineorareactor.Pleaserefertoourpublications206and615fordetailscon-cerningtheresistanceofglass.

m Never operate this measuring device outside its permissible oper-ating conditions.

2.2 Warnings contained in the operating instructions

m In these operating instruc-tions, the danger symbol is used to draw your attention to especially important safety instructions. Com-pliance with these instructions is mandatory, because adherence to the instructions can avoid severe damage to people and/or equipment.

2.3 Notes on deliveriesTherespectivescopeofdeliveryisspeci-fiedontheshippingdocumentsattachedto theshipmentandcorrespondsto thevalidpurchaseagreement.

Checkthat the itemsdeliveredarecom-pleteandintact.

Ifpossible,keepthepackingmaterialforre-useforpossiblereturnshipments.

2.4 Transport and storageTheprobeshouldonlybetransportedandstoredinitsclosedoriginalpackaging, ifpossible.Where this is not possible, theprobemust be protected against shockand impacts. In order to guarantee anas-new condition of the probe,maintainthefollowingstorageconditions:dryanddust-free as well as steady temperatureandventilation.Theprobesdonotneedany preservatives, they are resistant tonormalenvironmentalinfluences.

Ifitistobestoredforprolongedperiodsof time, the probe must be protectedfrom drying out. For this purpose, thebigger protective cap provided mustbe filled with demineralized water andfittedtotheprobetip.Thesmallprotec-tive cap providedmust be fitted to thehose connector at the probe tip. In theeventofprolongedservice interruptions,the probe may also remain inside theempty container or the empty pipeline.However, the electrolyte reservoir mustremain connected and pressurized forthispurpose.

Drystoragebasicallydoesnotaffectthefunctionof theprobe. Its characteristicsaremaintainedinanycase.However,thezeropointmaybesubjecttoslightchangewhichmayresultinameasuringerrorof0.2pHmax.Thiserrorcanbecorrectedbyreconditioningtheprobe(refertoSect.8.2).Duringoperationoftheprobe,thiserrorwillalsodisappearafterafewhours.

Ifaprobeisimmersedinliquid(product),the pH transmittermust not be discon-nected from mains for more than 1-2days.Otherwise,polarizationatthemea-suringelectrodemayresultinazerodriftwhichmayeventuallybeoutsidetheset-ting range of the pH transmitter.Wherelongerdisconnection frommainscannotbe avoided, the measuring circuit mustbe interrupted. This canbe achievedbyunscrewingtheconnectorfromtheprobeorseparatingtheconnectionatthetrans-mitter.

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pH Probetype pH Reiner

2.5 Warranty notesAnywarrantyclaimsshallnotbeextendedorlimitedbytheinformationcontainedinthepresentoperatinginstructions.

Fortheexactwarrantyconditions,pleaserefer to the Terms of Sale of PfaudlerWerkeGmbHasamended.

2.6 Notes on return deliveries Before sendingusedprobes toPfaudlerWerkeGmbHorthirdpartiesforrepairorotherpurposes,allpartsmustbecleanedanddecontaminated.

To protect our staff and for insurancereasons, your return shipment must beaccompanied by a clearance certificateonwhichyouconfirmthattheprobewasproperly cleaned and decontaminated.Youmayobtainaformsheetforthispur-posefromusonrequest.

2.7 Glass TestingThecustomaryhigh-voltagesparktestofthe glass lined surface is not permittedforthemeasuringprobes!

Before performing a high-voltage sparktest on the reactor, the probemust beprotected against damage by electricalormechanicalinfluences.Theentireglassliningoftheprobescanbemonitoredus-ingthePfaudlerglasstestingequipmentof the types Corrosion Detector (port-able)orGlasSparker®.Whenmonitoringareactorwithoneoftheseglasstesters,theintegratedprobesarealsomonitoredautomatically.

Depending on the conductivity of theproduct, the accuracy of the measure-ment is influencedbyaglasstester.Forthis reason, itmustbeensured that themeasurementandglasstestingfunctionsdo not operate at the same time.Glassmonitoringmust be switched off duringmeasurement.

©PfaudlerGmbH

3 Safety

3.1 Proper useAnyuseoftheprobeforpurposesotherthan described in the present operatinginstructionswilladverselyaffectthesafetyand functioningof themeasuringdeviceandisthereforenotallowed.

It is important to note the valid safetyregulations concerningelectrical installa-tions.

m Do not practice any working methods which may endanger safety.

3.2 Qualified personnelTheprobemayonlybeinstalled,operatedandservicedbyauthorizedpersonnelwithspecialskills inmeasuring technologyandinstrictcompliancewiththeseoperatinginstructions as well as the valid provi-sions.

Thefailuretoobservethese instructions– nomatterwhetherintentionallyorneg-ligently–releasesPfaudlerWerkeGmbHfromallliabilityandwarrantyclaims.

4 Technical description

4.1 Features and propertiesThepHprobe“pH Reiner”maybeusedwithin a broad range of industrial pHmeasurements. It has been specificallydesignedforapplications inthepharma-ceuticalandfoodindustry.Theseapplica-tionsmakehighdemandsonthehygienicconditionandsterilizationcapabilityofthemeasuringequipmentused,aswellastheaccuracy and stability of the measuredvalues. These requirements are satisfiedbypHReinertoaveryhighdegreeduetothefollowingfeaturesandproperties:n Those parts of pH Reiner that are incontact with product are glassedwith PPG = Pfaudler PharmaGlas oraremade of stainless steel. PPG is aglass type that has been optimizedforapplications in thepharmaceuticalindustry.Formoredetails,pleasereferto publication 615. The O-rings usedare made of EPDM and have beenapprovedforfoodapplications(FDA).

n The pH Reiner probe is suitable forCIP(clean-in-place)andSIP(sterilize-in-place)processes.

n The electrolyte used for pH Reiner isfilledintoinfusionbottlesundersterileconditions. The bottles are equippedwith a septum (partition wall) whichensuresthesterileuseofthebottles.

n The entire electrolyte system of pHReinercanbeeasilycleanedanddisin-fectedwitha70percentethanolsolu-tion.

n ThelengthanddiameterofpHReinerprobescorrespondto thedimensionsof commercially available glass elec-trodes.As theprobe is availablewithvarious threador installationadapters,itcanbeeasilyattachedtoallconven-tionalprocessports.

4 ©PfaudlerGmbH

n ThesensorareaofpHReinerisapprox.10cm2andthusmuchlargerthanthesensor areaof glass electrodes.As aresult, accurateandwell reproduciblepHmeasurementsareobtainedeveniftheprobeiscontaminated.

n DuetothespecialpHglass,andincon-nectionwith thederivationmethodofthePfaudlerpHprobes,thepHReinerprobe is characterized by high long-term stability. This ensures accuratereproducibility of themeasured valueswithout subsequent calibration evenafterCIPorSIPprocesses.

n Thediaphragmdoesnotgetcontami-nated due to the overpressure in theelectrolytesystem.Thisensuresaccu-ratepHmeasurementsand long-termstability.

n Duetoitsrobustconstructionandthemetallic probe body, the probe canbe installed in pipelines and reactorsdirectly and without any disturbing,expensiveprotective reinforcement.Ahighflowvelocityattheprobeisdesir-able because it ensures self-cleaningof the probe. Based on the robustconstruction of the probe, it has averylongusefullife.SimilarpHprobesmadebyPfaudleroftenreachausefullifeofseveralyears,dependingontheirapplication.

4.2 Measuring principleThepHvalueisameasureofthehydrogenionactivityaH+inasolution.ThepHvalueisdefinedasthenegativelogarithmofthehydrogen ion activity aH+. Of practicalimportance is thepHvalue in the rangebetweenpH0andpH14.Thatis,pH0isastrongacid,pH14isastrongalkali,andpH7isneutral.

ThepHReinerprobesoperateaccordingto the principle of potentiometry, i.e. apH-dependentpotential isbuiltupatthepHprobethatissubjecttothehydrogenion activity in an aqueous solution. ThispotentialisderivedandevaluatedbyapHtransmitter.

The actual sensor of the pH Reinerprobes consists of pH-sensitive glass.At thephase limitbetweenthepHglassandthemeasuredsolution,theso-calledgellayer,anionexchange(hydroxilation)takesplace in thecourseofwhichalkaliions of the pH glass are replaced withhydrogenionsofthemeasuredsolution.Thethicknessof thegel layer isapprox.5-150 nm. The pH-dependent potentialbuildingupinthegellayeristransferredbyaionicconductortoametalderivativelayerlocatedbelowthepHglass.

The pH sensor is a phase boundarystructurebetweentwochemicallydistinctsubstanceswithaliquidphaseandasolidphase.Suchaphaseboundarystructureisreferredtoasahalf-cell.Thepotentialof a half-cell, which is also called phaseboundaryorGalvanipotential,cannotbemeasured directly because a measuringinstrument would constitute anotherphase boundary in the measuring loopwhosepotentialinturnwouldbeunknown.Forthisreason,thepotentialofahalf-cellcanonlybedeterminedbyaseriescon-nectionofa secondhalf-cell. The “liquidphases” of the half-cells are connectedviaadiaphragm.Thesecondhalf-cell,theso-called reference electrode, supplies adefined,constantpotentialduetoitsveryconstruction.TheseriesconnectionofthepHelectrodeandthereferenceelectrodeprovidesameasuringsignalthatconsistsofthesumofthevariable“pHpotential”and the constant “reference potential”.ThemeasuredsignalissuppliedtoapHtransmitterforevaluationthroughappro-priateconnections.

Figure1 pHReiner

MT0076_1E

1 Socket(Variopin)andcable2 Connector(Variopin)3 Probehead4 Self-lockingcouplingandelectrolytehose

5 Self-lockinghoseconnector6 Referenceelectrode(integratedinprobehead)

7 Ventingplug8Ventingoutlet9 Threadadapter

10 Probetube,glasslinedwithPPG 11 Pt1000(integratedinprobetube) 12 Rhodiumelectrode 13 pHsensor(pHglass) 14 Grounddiaphragm

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pH Probetype pH Reiner

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4.3 Construction and function

The pH Reiner probe consists of two principal components:n Measuring proben Reference system

The measuring probeconsists of a glasslined steel tube (10).The pH sensor (13) and the diaphragm(14) are fittedtooneendofthetube.The probe head (3) and the installationadapter(9)are locatedattheotherendofthetube.

The pH sensor consists of pH-sensitiveglass, which will also be referred to as“pH glass”inthismanual,andwhichhasbeen fused around theperimeter at theendofthetube.Thesensorareaisapprox.10 cm2. The metallic derivative layer islocatedbelowthepHglasswhichensureshigh-resistance insulation between thederivativelayerandtheprobetube.

The combination of the pH glass and the metal derivative layer results in the pH-sensitive measuring elec-trode.

Thepotentialofthemeasuringelectrodeis transmitted to the connector at theprobeheadbyafused-in,insulatedstainlesssteeltape

Above the pH glass, there is a rhodiumelectrode (12) that serves as productground. This electrode allows for sym-metrical measurement, and thus forcontinuousimpedancemonitoringofthemeasuringandreferenceelectrode.

The diaphragm, which is also called agroundor split diaphragm, is locatedatthetipoftheprobetube.Ithasthetaskofmakingaconductiveconnectionbetweenthe reference system and the product

©PfaudlerGmbH

whilepreventingtheproductandtheelec-trolytefrommixing.Thediaphragmcon-sists of a ground ceramicpuck and theprobetubeendwhichisglass-coatedandgroundinside.Theceramicpuckisshrink-fittedintotheendoftheprobetube.Thecontact area between the ceramic puckand thegroundglass surface forms thediaphragm gap. As the diaphragm gapallowspenetrationofelectrolyteandtheoutside of the diaphragm is in contactwithproduct,theelectrolytelineprovidesa conductive linkbetween the referencesystemandtheproduct.

Inside the probe tube, the electrolyte isguided through an insulated supply linefrom the probe head to the diaphragm.Theelectrolytelinecanbeventedthroughaventingplugattheprobehead.

A 6-pole connector (2) located on theprobe head provides for connection oftheprobetothetransmitter.Connectionismadeusing thepHReinerconnectioncord.Theelectrolytehoseisconnectedtoaself-lockingswivelconnector(5)locatedatthesideoftheprobehead.Theventingplug(7)forventingtheprobeis locatedbelowthisconnector.

A thread adapter (9) below the probeheadisusedtoscrewtheprobeintotheprocessport.

Allmetalpartsareconnectedtoacontactinsidetheconnectorattheprobeheadinordertoensuregroundingof theprobe.The probe is linked to the equipotentialbondingsystem(grounded)via thiscon-tactand thepHReinerconnectioncord,refertoSection7.4.

The reference systemconsists of the electrolyte reservoir andthereferenceelectrode.

The electrolyte reservoir comprises apressure vessel made of stainless steelwhich holds an infusion bottle made ofPE. This bottle contains the electrolyte.Theelectrolytereservoirisinstalledsepa-ratelynexttotheprobeonlocation.Thereservoir is linked to theprobeheadbya PTFE hose (electrolyte hose) includedin the delivery. The electrolyte reservoirmust be permanently pressurized withcompressed air. This is to ensure thatelectrolyte can permanently reach thediaphragmandfinallytheproductthroughtheelectrolyte line.Thepermanentelec-trolyte diffusion is designed to avoidcontaminationofthediaphragm.Further-more, it preventsproduct fromenteringtheelectrolytelinethroughthediaphragmgapandcontaminatingthediaphragm.

Thereferenceelectrode(6)isinstalledintheelectrolytelineinsidetheprobeheadand is linked to theelectrolyte reservoirthroughthePTFEconnectionhose.

The combination of the measuring electrode and the reference elec-trode and their conductive connec-tion through the electrolyte line, diaphragm and product forms the measuring chain

Whentheprobeisimmersedintheprod-uct,themeasuringchainsuppliesahigh-resistance, pH-dependent potential thatis converted by a suitable pH transmit-ter into a standard signal (4-20mA) inproportiontothepHvalue.

ThemeasuredpHvalue is influencedbythe product temperature because theslopeof ameasuring chain dependsonthe temperature according to Nernst‘sconstant(refertoSect.5.1).ThepHReinerprobe is equipped with a Pt1000 (11)thatisusedtomeasuretheproducttem-peratureinsidethetransmitter.Therefore,thetemperature-dependentslopechangeofthesensorcanbeautomaticallycom-pensatedbythetransmitter.

pH Probetype pH Reiner

6 ©PfaudlerGmbH

4.4 Electrolyte reservoirTheelectrolytereservoiroperatesaccord-ingtothefollowingprinciple:APEbottle(infusion bottle) containing electrolyte isplaced intoapressurevessel.When thebottle is installed, a hollow needle pen-etrates the septum (rubber plug) of thebottle.Thepressurevesselisclosedandpressurized with compressed air. Thepressure inside the vessel squeezes thesoftPEbottletogether,andelectrolyteispressedoutthroughtheneedle.

TheelectrolytereservoirofthepHReinerprobebasicallyconsistsofa2-piececon-tainermadeofstainlesssteel (1,3)andaplastic insert(4).Theupperandlowerpartofthecontainerareheldtogetherbyaclamp(2).Theplastic insert is locatedin the lowerpartof thecontainerwhereit isfixedinplacewithaunionnut(13).Belowtheunionnut,thereisathreadedjoint (14) which serves the followingfunctions:n Thehollowneedlethat ispushed intotheelectrolytebottle(8)isfastenedtothisjoint.Inordertoreplacetheneedle(6),thejointmustberemovedbeforetheoldneedle canbepulledout andthenewneedlecanbeinserted.

n If the electrolyte bottle is to bereplaced, first the pressure vesselmust be de-pressurized. This is doneby opening the threaded joint byapprox.2-3turns.

A self-locking coupling (7) is providedatthebottomoftheplastic insertwhichservesforconnectingtheelectrolytehose.The followingpartsarealsoattached tothebottompartofthepressurevessel:n Straight male union made of PVDFDN 4/6, G 1/4” with O-ring (11), forcompressed-airconnection

n Steelanglebarforinstallationatawallorpipeline(9)includinggroundtermi-nal(10)

n Female union for level monitoring(option)(12)

Figure2 Electrolytereservoir

MT0075_1E

1 Electrolytereservoir,upperpart2 Clamp3 Electrolytereservoir,lowerpart4 Plasticinsert5 Septum(rubberplug)6 Hollowneedle7 Self-lockingcoupling8 Electrolytebottle9 Mountingplate

10 Compressed air connection with return valve for plastic hose 6mm (OD) 11 Electrolyte monitoring

–empty messageusingultrasound(refertosparepartslistoption)

12 Unionnutforplasticinsert 13 Threadedjointforhollowneedleandventing 14 Self-lockingconnectorwith

electrolytehose

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pH Probetype pH Reiner

The electrolyte reservoir has been de-signed for easy replacementof the elec-trolytebottlewithoutaffecting thesterilepropertiesoftheelectrolytesystem.

Theelectrolytereservoirisapprovedforamax.internalpressureof7bar.

Optional levelmonitoring isavailable fortheelectrolytereservoir.

7©PfaudlerGmbH

4.5 Reference electrodeAsilverchlorideelectrodeisusedasrefer-enceelectrode,lettersymbol:AgAgCl.

The measuring chain zero when usinga silver chloride electrode is reached atapprox.8.65±1pH.ThezeropointofpHReinerisnotidenticaltotheisothermpointwhichisfoundat1.0±1pH.There-fore,thetransmitterselectedshouldofferindependent,freeparameterizationofthezeropointand the isothermpoint (refertoSect.5.2and5.3).

Theguaranteedlifeofthesilverchlorideelectrode amounts to 24 months fromthe date of delivery. However, its actuallifeismuchlongerinmostcasesandusuallyequalsthatofthepHReinerprobe.

The reference electrode is permanentlyinstalledintheprobehead.ThereferenceelectrodemayonlybereplacedbyPfaudler.

4.6 ElectrolytePotassiumchloride,3-molKCl,pH4withaninhibitoradditive,isusedaselectrolyteforpHReiner.Theelectrolyteisfilledinto1literPEbottles(infusionbottles)understerile conditions which are supplied byPfaudler. These bottles are completelyplacedintheelectrolytereservoir.

Only Pfaudler electrolyte may be used in order to guarantee the fault-less function of the probes for a long period of time.

IfKClshouldbeinappropriate,e.g., ifnochloridemayentertheproductor ifKClreactswiththeproduct,itisalsopossibletouseanotherelectrolyte.Insuchacase,however,itisabsolutelynecessarytocon-tactPfaudler.

4.7 Thread adapterThethreadadapterislocatedrightbelowtheprobehead. Its purpose is to screwthe pH Reiner probe into the local pro-cessport.Theadapterconsistsofarota-tablestainlesssteelringwithanexternalthread. The following thread sizes areavailable:n M20x1.5n PG13.5n 3/4“n 1“

Using these thread adapters, pH Reinercan be directly screwed into the corre-spondingprocessportsthatarealsocus-tomary for glass electrodes. The neces-sarygasketsbetweentheprobeandtheprocessportmustbeorderedseparatelybecause they dependon the installationconditionsonlocation.

Threadadapterswithother thread sizesare also available on request subject totechnicalcoordination.

4.8 Installation adapterThethreadadapterslistedinSection4.7arenotsuitableforallprocessportsfoundinpractice.Therefore,specialinstallationadapters are available for the followingprocessports:n PfaudlerAsepticweldednozzlesDN30

n IngoldweldednozzlesDN25n Variventadapters

The connection thread of the threadadapterisalwayssizeM20x1.5.

All necessary gaskets are suppliedtogether with the installation adapter.Installationadaptersinotherdesignsarealsoavailableonrequestsubjecttotech-nicalcoordination.Forassembly,refertoAnnexA.

pH Probetype pH Reiner

Figure3 Insertingthebottle

8 ©PfaudlerGmbH

4.9 Technical data

Slopeofthemeasuringchain: 56-59mV/pHat25°C*Zeropointofthemeasuringchain: 8.65±1pH*Isothermpointofthemeasuringchain: 1,0±1pH/440mV*Potentialofthemeasuringchain: +600to–400mVInternalresistanceofthemeasuringchain: 109-1010Ωat25°CDiaphragmresistance: approx.20-200kΩInsulationresistance: ≥1012ΩInternalcapacitance(withconnectioncord): ≤5nFInternalinductance(withconnectioncord): negligibleAllowableworkingtemperature: -5 to +140 °C (higher temp. on demand)

Allowableworkingpressure: –1/+6barMax.ambienttemperature: 50°CTemperaturemeasurement Pt1000Thermalshockresistance: ∆­T=120°CResistance: refertoFig.6

*forexactvalues,refertotestreport

5 Technical characteristics of measurement

5.1 Slope of the measuring chainTheslopeSofapHprobeisdefinedasfollows:

S = ∆­E/∆pH

∆E = changeinpotentialofthepHprobe

∆pH =pHchangeofthemeasuredsolution

ThetheoreticalslopeofapHprobeisap-prox. 59.2mV/pHat25°C. In practice,this value is not reached due to designandmanufacturingrestrictions.TheslopeofapHReinerprobeisapprox.57.5mV/pHat25°C.Inordertocomparetheslopeoftheprobewiththatofotherprobes,thevalue isalwaysspecifiedwith respect tothestandardtemperatureof25°C.

Due to the physical properties of themeasuringelectrode(pHglass),theslopeof the probe is temperature-dependent.TheslopechangesaccordingtoNernst‘s constantata rateof0.1983 mV per 1 °C and per 1 pH.

This temperature influence canbe com-pensatedbythemodernpHtransmittersused today. For this purpose, the trans-mitter must measure the temperatureof themeasured solution (product) andthemostimportantcharacteristicsoftheprobe – slope, zero point and isothermpoint – must be programmed into thetransmitter (parameterization) (refer toSect.8.5).

Eachprobeistestedandmeasuredpriortodelivery.Themeasuredslopeisspeci-fied in the test report supplied togetherwith the probe (nominal value). Thenominal slope value must be input intothe transmitter in the course of calibra-tioninordertocalculateandcompensatethetemperature-dependentpHvalueshift(temperaturecompensation).

pH Probetype pH Reiner

Figure4 Installationsizes

MT0081_1

274

120

46

12,3[mm]

withoutinstallationadapter

withinstallationadapter

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Theslopeisrecalculatedduringeachtwo-pointcalibrationprocess.Thenewvaluecalculatedwillthenbeusedbythetrans-mitter for temperature compensationduringthecurrentpHmeasurement.

The slope of glassed pH probes remains constant during the entire life of the probe, i.e. the probes are not subject to aging. Therefore, recalibrating the pH Reiner probe regularly is not nec-essary if the measuring loop is prop-erly insulated.

5.2 Zero point of the measuring chain

The measuring chain zero is the pHwith a measuring chain voltage of zero(totalpotential). The totalpotentialbasi-callyconsistsofthesumoftheindividualpotentialsofthemeasuringandreferenceelectrode. The zero point is decisivelyinfluencedbythetypeofreferenceelec-trode,andthusthepotentialoftherefer-enceelectrode.

Asilverchlorideelectrodeisusedasref-erence electrode for pHReiner, refer toSection4.5.

Themeasuringchain zerowhenusingasilver chloride electrode is reached atapprox.pH8.65±1= pH0.

Eachprobeistestedandmeasuredpriorto delivery. The measured zero pointis indicated in the test report suppliedtogetherwith theprobe (nominalvalue).The nominal zero point value must beinputintothetransmitterinthecourseofcalibrationinordertocalculateandcom-pensate the temperature-dependent pHvalueshift(temperaturecompensation).

Thezeropointisrecalculatedduringeachcalibrationprocess.Thenewvaluecalcu-latedwillthenbeusedbythetransmitterfortemperaturecompensationduringthecurrentpHmeasurement.

©PfaudlerGmbH

5.3 Intersection of isothermsIfthetotalpotentialofameasuringchainisplottedasafunctionofthepHvalueofameasuredsolution(product)foracer-tain, constant temperature of themeas-uredsolutioninadiagram,astraightlineis obtained which is also referred to as“isotherm”.Theslopeof the isotherm istemperature-dependent (refer to Sect.5.1). For this reason, two isothermsdeterminedattwodifferentproducttem-peratures each have a different slope(ascending gradient), and therefore acommonintersection.Theintersectionoftwo isotherms is referred to as the iso-therm intersection, or isotherm point inthismanual.

ThecoordinatesoftheisothermpointarereferredtoaspHisandUis.

Figure5 Isothermintersection

MT0072_1E

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IsothermpointUis=approx.440mV,pHis=approx.1.00pH

ZeropointpH0=approx.8.65pH

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Characteristicsofsilverchlorideelectrode(AgAgCI)

pH Probetype pH Reiner

The isotherm point of the pH ReinerprobesisreachedatpH1.0±1=pHis. For the exact value applicable to therespectiveprobe,pleaserefertothetestreport.This value remainsconstantdur-ingthewholelifeoftheprobe.

ThevalueofUisisapprox.440mVwhenusingasilverchlorideelectrode.For theexact value applicable to the respectiveprobe,pleaserefertothetestreport.

The isotherm point must be input intothe transmitter in the course of calibra-tioninordertocalculateandcompensatethetemperature-dependentpHvalueshift(temperature compensation). Dependingon the transmitter used, oneof the twocoordinatesUisorpHismustbeenteredasisothermpoint.Sometransmittersalsorequiretheinputofbothvalues.

10 ©PfaudlerGmbH

5.4 Resistance of the measuring chain

Short response times depend on the low-estpossible resistanceof themeasuringelectrodes. The resistance of themeas-uring electrodemust be lower than theinsulationresistancebetweentheconduc-tor electrode and the probe body. Thisrequirement is met by a relatively low-resistancepHglassincombinationwithahigh-resistanceprotectiveglasslayer.Theglassteelprobebodyisgroundedfordis-sipatingelectricalleakagefields.

Resistance at 25 °CMeasuringelectrode: 109-1010ΩReferenceelectrode: 5-10kΩInsulation: ≥1012Ω

5.5 Diaphragm resistanceThe resistance of the diaphragm is20-200 kΩ. The diaphragm has beenground to ensure the minimum perme-ability (leakage rate) of the electrolyte.Basedontheoverpressureintheelectro-lytesystem,thedangerofcontaminatingthediaphragmisverylow,andthesameappliestotheriskofdiffusionpotentialsbuildingupatthediaphragm.

Inaqueousmedia,theinfluenceofthedia-phragmresistanceonthetotalpotential,andthusthepHvalue,isextremelysmallorevenzero.

5.6 Measuring varianceDuring final testing in the factory, theexact values of the isotherm point, Uisand pHis, are measured and specifiedin the test report. If the exact values ofthe isotherm point are entered in thetransmitter,themeasuringvariancedoesnotexceed±0.05pH.Thisvalueisonlyachieved,however, if theallowableoper-atingconditionsaremaintained.

5.7 Alkali errorThe allowable measuring range is inbetween the lowest pH value andpH10.Above pH 10, the alkali error producesa deviation that increases with tempera-ture and the Na+ concentration. ThealkalierrordoesnotoccurifnoNa+ionsarepresent.WithK+ions(e.g.ammonia),mea-surementcanbeperformeduptopH14.

5.8 Time response to pH changeElectrochemicalprocessesatthesurfaceofthemeasuringelectrodeandthetimeconstantofthemeasuringloopdeterminethe time response of the probe to pHchanges. Up to strong alkali values, theelectrochemical equilibrium is reachedvery fast, so that the influence of theelectrical components of the measuringloopontheresponsetimesisofgreatestimportance.

Thedisplay’sresponsetosuddenchangesofthepHvaluegenerallydoesnotaffectthemeasuringprocess.Thefinalvalueisnormally reached after a few seconds.Only above pH 8 it takes a little longertoreachthefinalvalue.Thisdelay,whichisalsocommonwithglasselectrodes, iscausedbyionexchangeprocessesattheelectrodesurface.

5.9 Time response to temperature changes

ThepotentialofthepHprobeshouldset-tle with the smallest possible hysteresiseveninthecaseofproducttemperaturechangesduringpHmeasurement.

Due to its very design, the measuringchain responds faster to temperaturevariationsthanthePt1000intheprobe.The resultingmaximumdeviation is lessthan0.1pHatatemperaturechangeof1°C/minorless.However,theexactiso-thermpointofthemeasuringchainmusthavebeenentered inthetransmitter forthispurpose.

pH Probetype pH Reiner

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6 Application limits

6.1 Chemical resistanceGlassisconsideredtoberesistantiferosionis lessthan0.1mmperyear.This isanaverage value which is determined inexperiments toDIN-ISOandrepresentedinso-calledISOcorrosioncurves(refertoFig.6).TheresistanceofourpHprobesdependsontheyellowpH-sensitiveglass(pHglass)becausetheresistanceofthisglass is slightly lower than that of ourPfaudler PPG glass. Exact determina-tions concerning the resistance cannotbemadeunlesstheapplicationisknownandcorrosiontestsweremade.Formoredetails,pleaserefertoourPublication614,“Pfaudlercompoundglassteelmaterials”.

6.2 TemperatureThe allowable product temperaturedepends on the pH. The maximumadmissibleproducttemperatureis140°C.For the permissible temperature range,pleaserefertoFig.7.

At product temperatures above 100°C,thepressureinsidetheelectrolytesystemmustbehigher than thevaporpressurein order to avoid boiling of the electro-lyte.Otherwise,vaporbubblesmayoccurwhichresultinafailureoftheprobe.

Duetotherisingresistanceofthemeas-uringelectrodewithfallingtemperaturesand the associated delayed displayresponse,thelowertemperaturelimitis0°C.However, based on the composition oftheelectrolyte,thepHprobesmayremaininsidethereactordowntoatemperatureof–5°C.Onrequest,specialelectrolytesare available which enable the probesto remain inside the reactoror thepipedown to a temperatureof–30°C.How-ever,thepHcannolongerbemeasuredreliablyatfrosttemperatures.

TheglassedpHprobeisresistanttothermalshockup toa∆Tofmax.120°C (tem-peraturedifferencebetweenproductandprobe).

©PfaudlerGmbH

160

140

120

100

80

60

40

20

01 2 3 4 5 6 7 8 9 10 11 12

pH

°C

Figure6 ISOcorrosioncurveofpHglass

Figure7 ApplicationrangeofthepHprobes

Applicationrangewithameasuringaccuracyof:<±0.1pHwith0.1nNa+

MT0017_1E

pH Probetype pH Reiner

12 ©PfaudlerGmbH

6.3 pH rangeForthepermissiblepHapplicationrange,pleaserefertoFig.6.Limitationsarebaseonthechemicalresistance(refertoSec-tion6.1)andthealkalierror(refertoSec-tion 5.7). After having been used in thestrongalkalirange,thesettingbehavioroftheprobes issloweddownwhenreturn-ingtotheneutralrange.InrangesbelowpH8,theproberegeneratesveryquickly.

Examples of proper pressure settings:1.Pressureinsidethereactor: 4 bar max.Vaporpressure: 1 baratanoperatingtemperatureof100°CMinimuminternalpressure: 4.5 bar

2. Pressureinsidethereactor: 2 bar max.Vaporpressure: 4 baratanoperatingtemperatureof140°CMinimuminternalpressure: 4.5 bar

6.4 PressureProbesaresuitableforanoperatingpres-sureof–1to+6bar.

Theelectrolytereservoirisapprovedforamax.internalpressureof7bar.

Duringoperation,thepressureinsidetheelectrolytesystemshouldbeatleast0.5barabovethemaximumpossibleoperat-ingpressureorthetemperature-depend-entvaporpressureof theprobe.This istoensure thatnoproductcanenter theprobe or contaminate the diaphragm.Furthermore, it is ensured that thediaphragmgap isalways incontactwithelectrolyte.Apressureregulationsystemisnotnecessary.Oncesettothehighestprocesspressure,theinternalpressureoftheprobedoesnothavetobereadjusted.Thedifferentialpressuremaybegreaterthan0.5 bar up to6 barmax., thiswillcauseincreasedelectrolyteconsumption.

6.5 Inappropriate productsReliablepHmeasurementsarenotpossi-bleinwater-freeproducts(watercontent<1%).

All fluorine-containing products belowpH6leadtostrongcorrosion.

Strongly hygroscopic products and theapplication of dry nitrogen to an emptyreactororpipelinewilldrainthegellayer,leadingtoalossoftheslope,whichcanbe corrected by reconditioning the pHprobe(refertoSection8.2).

m If the probe is subject to process pressure inside the reactor or the pipeline, it must be ensured that the pressure inside the electro-lyte system is permanently at least 0.5 bar above the process pressure. Otherwise, there is a risk of product entering the probe through the dia-phragm gap and clogging or contami-nating the electrolyte line.

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7 Installation and electrical connection of the probe

7.1 Installation of the probeTheprobemaybeinstalledbothinreac-tors and in pipelines. It is important tomaintainsufficientclearancebetweentheprobeandanybuilt-inpartsaswellasthereactororpipelinewall.

The probe is screwed into the existingprocessportusingtheproper threadorinstallationadapter(refertoSect.4.7and4.8).

Theprobe isavailable ina single lengthonly.

ThepHReinerprobemaybeinstalledinanyorientationbecausetheoverpressurein the electrolyte reservoir ensures thatelectrolytemayflowfromtheelectrolytereservoir totheprobe,regardlessoftheorientationoftheprobe,atalltimes.

7.2 Installing the electrolyte reservoir

The electrolyte reservoir is installed ver-tically and as close as possible to theprobe,max.distance5m.

The electrolyte reservoir and the probeheadarelinkedbyaPTFEhose(electro-lytehose) included in thedelivery (deliv-ered length 5m). One end of the hoseis equipped with a self-locking couplingandtheotherendwithaself-lockingcon-nector.Plugthecouplingontotheprobeheadandtheconnectorontotheelectro-lytereservoir.Thehosemaybecuttotheappropriatelength.

Connect the electrolyte reservoir to thecompressedairsupplyusingapressure-reducing fitting.Connection to thepres-surevesselismadeusingathreadedjointmadeofPVDFDN4/6G1/4”.Thepressureinside the pressure vessel must be atleast0.5barabove themaximumproc-esspressure.Formoredetailsconcerningtheproperpressuresetting,pleaserefertoSection6.4.

©PfaudlerGmbH

7.3 Electrical connection of the probe

Fortheelectricalconnectionoftheprobeto the transmitter, please refer to thecircuitdiagramandtheoperatinginstruc-tionsofthetransmitterused.Thecircuitdiagrams for the transmitters approvedbyPfaudlermaybeobtainedfromusonrequest.

UsethepHReinerconnectioncord(refertoSect.7.5)forlinkingtheconnectorattheprobeheadandthetransmitter.

Connectingthecables:Properlypositionthesocketoftheconnectioncordontheconnector of the probe head and pressconnectorstogether.Manuallytightentheunionnutonthesocket.

ForthecoreassignmentofthepHReinerconnectioncord,pleaserefertoSection7.5.

m In order to avoid any type of potential loss, please ensure that no moisture can enter the connector or the socket. If necessary, dry both parts using a hair dryer or hot-air fan.

Figure8 ConnectiondiagramofpHReiner

MT0073_2E

1 Compressedairornitrogen2 pHReinerconnectioncord3 pHtransmitter4 Supplyvoltage5 Signaloutput6 Equipotentialbonding7 Compressedairregulator(notincludedindelivery)

1

4

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2

6

3

7

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7.4 Equipotential bonding

A Installation within a plant which basically consists of metallic parts – reactor, pipeline and nozzles –with a high conductivity.

In such plants, separate equipotentialbonding of the probe is not necessary.Equipotential bonding (grounding) oftheprobebodyisensuredbythemetal-lic link between the installation adapterandtheinstallationnozzle.Thegraywirecontained intheconnectioncord(probebody)neednotbeconnectedtothetrans-mitter. The cable shield (green/yellowwire)mustbeconnectedtothetransmit-ter’s equipotential bonding terminal. Nogeneraldescriptionof theexact locationof theequipotentialbondingterminalonthe transmitter to which the green/yel-lowwiremustbeconnectedcanbegivenat this point because this terminal maydiffer in design depending on the typeof unit and itsmanufacturer. The circuitdiagrams for the transmitters approvedby Pfaudler (refer to Sect. 7.6)may beobtainedfromusonrequest.

Theelectrolytereservoirmustbeconnectedseparately to the equipotential bondingsystemoftheplantorgrounded.

pH Probetype pH Reiner

B Installation within a plant whose principal elements – reactor, pipe-line and nozzles – are made of plastic or other non-conductive materials, or have been coated with non-conductive materials, such as glassteel.

In such plants, separate equipotentialbondingof theprobemustbeprovided.Allmetalpartsoftheprobe(probebody)areconnectedtopin“C” insidethecon-nector at the probe head. Equipotentialbonding is achieved by connecting thegraywireof theconnectioncord (probebody) to the equipotential bondingterminal of the transmitter. The cableshield (green/yellow wire)must also beconnectedtothetransmitter’sequipoten-tialbondingterminal.Nogeneraldescrip-tionoftheexactlocationoftheequipoten-tialbondingterminalonthetransmittertowhichthegrayandthegreen/yellowwiresmustbeconnectedcanbegivenat thispointbecausethisterminalmaydifferindesigndependingonthetypeofunitanditsmanufacturer.Thecircuitdiagramsforthe transmitters approved by Pfaudler(refertoSect.7.6)maybeobtainedfromusonrequest.

Theelectrolytereservoirmustbeconnect-edseparatelytotheequipotentialbondingsystemoftheplantorgrounded.

7.5 pH Reiner connection cordThepHReinerconnectioncord isapre-fabricatedcable that isusedto transmitallelectricsignalsandfunctionsfromtheprobetothetransmitter.Thecableisspe-cificallydesignedfortransmissionofveryhigh-impedance signals. As a standard,the cable is available in lengths of 3 or5m.Cablelengthsofmorethan5mmayadverselyaffecttheresponsebehaviorofthepHReinerprobe.

Aspecialsocketisfittedtoonecableendwhichfitsintotheconnectorontheprobehead. The other cable end has beenstripped of the insulation. Connect theindividualwires to the transmitter termi-nals.Forthepinassignment,pleaserefertoTable1.

Belowtheheat-shrinkabletube,a220nFcapacitorhasbeenfittedtothestrippedcable end which is connected in serieswiththewiredesignedforthecableshield(green/yellowwire).A470nF capacitorhas been installed in the probe headwhich is connected in series with theterminal for theprobebody (graywire).The purpose of these capacitors is toinhibit low-frequency compensation cur-rentswhichmightbepresentifbothcableendsare connected to theequipotentialbondingsystem.

Forequipotentialbonding,adistinctionmustbemadebetweentwodifferenttypesofinstallation.

15©PfaudlerGmbH

Connector pin Conductor color Function

A black pHsensor

B red Referenceelectrode(coaxialshield)

C gray Probebody

D blue Rhodiumelectrode

E white Pt1000

F green Pt1000

S green/yellow Cableshield

Table 1 Assignment of cores of the pH Reiner connection cord

7.6 List of pH transmitters approved by Pfaudler

OnlysuitableequipmentmaybeusedaspHtransmitterswhichmusthavethefol-lowingfeatures:n Symmetricalhigh-impedanceinputs,Ri≥1012Ω

nIt must be possible to set the zeropoint and the isotherm point of theprobefreelyandindependently.

Forprogrammingthetransmitters,pleaserefertothemanufacturers‘operatinginstruc-tions.

m If a probe is immersed in the product, the pH transmitter must not be disconnected from mains for more than 1-2 days. Otherwise, polarization may result in a zero drift and the need for calibration. Where longer disconnection from mains cannot be avoided, the measuring circuit must be interrupted. This can be achieved by unscrewing the con-nector from the probe or separating the connection at the transmitter.

*thenominalzeropointandthenominalslopecanbeparameterized**Rosemount

pH Probetype pH Reiner

Figure9 Connectiondiagram

MT0079_2

A

B

C

D

E

F

220nF

A

B

C D

E

F

16 ©PfaudlerGmbH

8 Start-up and calibration

8.1 Preliminary noteWhen the probe has been installed andconnected as described in Section 7,start-upiscarriedoutinseveralsteps:tReconditioning of the probe (refer toSect.8.2).

tCleaning and disinfection of the elec-trolyte system (refer to Sect. 8.3).This process is required for sterileapplicationsonly.

tFilling the electrolyte reservoir andventing of the probe (refer to Sect.8.4).

tParameterizationofthetransmitter(re-fertoSect.8.5).

tCalibrationoftheprobe(refertoSect.8.6-8.11).

The individual stepswill be explained indetailbelow.

8.2 Reconditioning the probeNewprobesaswellasprobesthathaveremained dry for prolonged periods oftimemaybe subject to slightmeasuredvaluedeviationsduringstart-up.Thisde-viationmaybecorrectedbyrecondition-ing the probe. By reconditioning, a gellayerisbuiltuponthesurfaceofthepHglass.Thisgellayerisanimportantcondi-tionforaccurateandstablepHmeasure-ments.Cleaningandsterilizingthereactororthepipelinecontainingtheprobepriortostart-upwillbesufficienttoreconditiontheprobe.Additionalreconditioningisnotnecessary.

Therearetwowaysofreconditioningtheprobe:n Watering of the probe for 12-24hours.

Or,ifthereconditioningprocessistobeaccelerated:n Immersing the probe into water at70-100°C for approx. 30 min orvaportreatmentfor10-15min.

Theprobecanbereconditionedinsideoroutsidethereactororthepipeline.

8.3 Disinfecting the electrolyte system

Forsterileapplications,theentireelectro-lytesystemcanbedisinfectedpriortotheactualstart-up.Thisprocessisperformedwitha70%ethanolsolution.Emptybot-tles with a septum (rubber plug) whichcanbeinsertedinthepressurevesselareavailable from Pfaudler. The probe usermustfillthebottleswithethanolhimself.

The permitted ambient temperature oftheelectrolytereservoiris0to+50°C.

Disinfection process:tOpen clamp on the electrolyte res-ervoir and take off the upper part. Ifthe electrolyte reservoir was alreadypressurized, itmustbedepressurizedbeforehand(refertostep7).

tPlace the bottle in themiddle of thelowerpartof theelectrolyte reservoirwiththeseptum(rubberplug)pointingdownward. The septum is penetratedbythehollowneedlelocatedatthebot-tomoftheelectrolytereservoir.

tReinstall the upper part of the ves-selandclose theelectrolyte reservoirtightlyusingtheclamp.

tApplyapressureof3barmin.totheelectrolytereservoir.

tOpen the venting plug on the probeheadbyapprox.oneturnandleaveitopenuntilapprox.50-100mlofetha-nolhaveemerged.Thenclosethevent-ingplugagainmanually.

tAllowtheethanol toreact forapprox.2-5min.

tShut off the compressed air supplyand de-pressurize the electrolyte reservoir. This is done by openingthe threaded joint at the bottom oftheplasticinsertbyapprox.2-3turnscounter-clockwise. When the electro-lytereservoirhasbeende-pressurized,immediately close the threaded jointagainmanually.

tOpenclampontheelectrolytereservoir,takeofftheupperpartandremovetheethanolbottle.

m Caution! After disinfection, the probe should be filled with elec-trolyte as soon as possible (refer to Sect. 8.4)!

m For sterile applications, those parts of the probe that are in contact with product must be sterilized by suitable methods. (refer to Sect. 9.4). As the pH Reiner probe is SIP-com-patible, it is not necessary to remove the probe from the reactor/pipeline for sterilization.

8.4 Filling the electrolyte reservoir and venting of the probe

The electrolyte line must be free frombubbles in order to ensure a faultlesselectrical connection between the refer-enceelectrodeandthediaphragm.

3molKCl,pH4,withaninhibitoradditiveisusedaselectrolyte(refertoSect.4.6).

The permitted ambient temperature oftheelectrolytereservoiris0to+50°C.

m Only Pfaudler electrolyte may be used in order to guarantee the faultless function of the probes for a long period of time and without dam-aging the ground diaphragm.

Process of filling and ventingtOpen clamp on the electrolyte res-ervoir and take off the upper part. Ifthe electrolyte reservoir was alreadypressurized, itmustbedepressurizedbeforehand(refertoSect.8.3,step7).

tRemove red cap from the electrolytebottle. Place the bottle in themiddleof the lower part of the electrolytereservoir with the septum (rubberplug)pointingdownward.Theseptumis penetrated by the hollow needlelocatedatthebottomoftheelectrolytereservoir. For sterile applications, theseptummustbedisinfectedwithetha-nolbeforehand.

tReinstall the upper part of the ves-selandclose theelectrolyte reservoirtightlyusingtheclamp.

tApplyapressureof3barmin.totheelectrolytereservoir.

pH Probetype pH Reiner

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tOpen the venting plug on the probehead by approx. one turn and leaveit open until the electrolyte emergeswithoutanybubbles. If theelectrolytelinewasdisinfectedbefore,approx.50-100mlofelectrolytemustemerge,de-pendingonthehoselength.Thenclosetheventingplugmanuallyandcleantheentireareacarefullywithwater.

tSet the necessary operating pressureat the electrolyte reservoir as de-scribedinSection6.4.

8.5 Setting the pH transmitter parameters

The probe-specific characteristics, suchasslope, zeropointand isothermpoint,aswellastheuser-specificsettingsmustbeenteredinthetransmitter(parameter-ized)beforecalibrationcanbecarriedout.Thecharacteristicvaluesareindicatedinthetestreportsuppliedtogetherwiththeprobe.Someoftheparameterstobeen-tered are summarized in the list below.This listdoesnotclaim tobecomplete.Fortheparameterstobeentered,pleaserefertotheoperatinginstructionsofthetransmitter used and the user’s require-ments. The parametersmay be enteredin parameter input mode or in calibra-tionmode,dependingonthetransmitterused.

Parameter Value setting Option selected

Slope Entervaluefromtestreport –

Zeropoint Entervaluefromtestreport –

Isothermpoint Entervaluefromtestreport –

Quantitytobedisplayed – pH

Temperaturecompensation – automatic

Temperaturesensor – Pt1000

Currentoutput 0-20mAor4-20mA pHormV

Table 2 Parameterization

8.6 What is meant by calibration?Calibration is defined as the adjustmentofthetransmittertothecharacteristicofthepHprobe.

The measuring chain of the pH probesupplies a potential that depends on thepH value of the product. The transmittermeasuresthispotentialandcalculatesthecurrentpHfromthemeasuredvalue.Thepotentialofthemeasuringchain,andthusthe pH, is influenced by various factors,suchasthecurrentpotentialoftherefer-enceelectrodeorinevitablespecimenvari-ance.Thesefactors,someofwhichcannotbedetectedbytheirverynature,arelargelyeliminatedbycalibratingtheprobe.

8.7 Calibration methodsThe following calibration methods areusedinpHmeasurementtechnology:n Calibration through data input at thetransmitter(refertoSect.8.8).

n Two-point calibration (calibration using2buffersolutionsofidenticaltempera-tures,refertoSect.8.9).

n Single-point or product calibration(calibrationwithproduct,refertoSect.8.10).

n Automatic calibration (refer to Sect.8.11).

We recommend performing two-pointcalibrationinthecourseofinitialstart-upandafterprolongedserviceinterruptions.Theindividualmethodsandtheirsuitabil-ityforpHReinerwillbedescribedinthefollowingsections.

8.8 Calibration by data input at the pH transmitter

Thiscalibrationmethodisusedwheneveraquickfunctiontestoftheprobeistobeperformed and/or if no highmeasuringaccuracyisrequired.

Process of calibration through data inputDepending on the transmitter used, thecalibrationand/orparameterizationmodemustbeactivatedandthecharacteristicvaluesof theprobe indicated in thetestreportmustbeentered.Whenthecalibra-tionmodehasbeenexited, theprobe isreadyforuse.

However, this calibration method doesnot guarantee faultless functioning or adefined accuracy of the probe. For thisreason,werecommendperformingatwo-pointcalibrationassoonaspossibleaftercalibrationbydatainput.

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8.9 Two-point calibrationTwo-point calibration is the calibrationmethodthatisusedmostfrequentlywithpHprobesbecausethemeasuringaccu-racyachievablewiththismethodistotallysufficient formostpracticalapplications,andagood functionalcontrolof thepHmeasuringequipmentisachieved.

Foratwo-pointcalibration,thepHvalueoftwodifferentbuffersolutionsismeasuredonebyoneatthesametemperature.ThemeasuringchainpotentialmeasuredeachtimeisthenassignedtotherelevantpH.Based on the two potentials measuredandtakingintoaccountthecurrenttem-perature,theslopeandzeropointvalueswill be recalculated by the transmitter.Then,automatictemperaturecompensa-tionisperformedbythetransmitterusingthesenew,calculatedvalues.

Some preparations have to be madebeforetheactualcalibrationcanbestarted.n AconstantpHmeasurementrequiresastateofequilibriumatthediaphragm,i.e. an evenly moistened ground sur-face. For this purpose, the electrolytereservoirmustbepressurizedapprox.1 hour prior to the beginning of thecalibration.

n In order to reach the highest possi-bleaccuracy in theadjustment to themeasuring chain characteristic, thepH values of the twobuffer solutionsshoulddifferbyatleast3pH.Werec-ommend using buffer solutions pH7 and pH 2 for two-point calibrationof the pH Reiner probe. Calibrationshould preferably be started with thebuffersolutionpH7.Ifalimitedmeas-uringrangeissufficient,abuffersolu-tionpH3orpH4.01mayalsobeusedforthesecondmeasuringpoint.

n The probe should be removed fromthe reactor/pipeline for calibration.Placetheprobeinasuitableplasticba-sin.Inordertoensuregroundingoftheprobe,theprobemustbeimmersedinthebuffersolutiondowntothethreadorinstallationadapter.

Process of two-point calibrationtReconditiontheprobeandrinseitwithdistilledwater.

tFilltheplasticbasinwiththefirstbuffersolutionpH7andimmersetheprobeinto the buffer solution down to theadapterbecausethebuffersolutionisgroundedviatheadapter.

tActivate the calibration mode at thetransmitter.ThenselecttheTwo-point calibrationmodeandenterthepHofthefirstbuffersolution.

tWait until the measured value dis-played has stabilized and then startthecalibrationprocess.Themeasuringchainpotentialdetermined isnowas-signedtopH7.

tWhen the first calibration step hasbeen completed, rinse themeasuringprobe and the plastic basin with dis-tilledwater andfill thebasinwith thesecondbuffersolution.

t Immersetheprobedowntotheinstal-lation adapter into the second buffersolutionpH2(optionallyalsopH3orpH4.01).The two buffer solutions should havethesametemperature.Ifthisisnotthecase,waituntilthetemperaturedisplayhassettledatastablevalue.

tEnterthepHvalueofthesecondbufferinthetransmitter.

tWait until the measured value dis-played has stabilized and then startthe calibration process. The meas-uring chain potential determined isnowassigned topH2 (or3or4.01,respectively).

tExitcalibrationmode.tTwo-point calibration should be veri-fiedafter1-2weeksby a single-pointcalibrationusingproduct.

8.10 Single-point calibrationSingle-pointorproductcalibrationisper-formedinordertoverifyapHmeasure-mentorforqualityassurancepurposes.

Process of single-point calibrationTakeaproductsamplefromtheprocessusing a suitable device. Then determinethepHvalueof this samplewith the re-quireddegreeofaccuracyusingamanualtester or in the lab. Compare the refer-encevaluethusdeterminedtothevaluedisplayed on the transmitter. The valuedisplayedcanbecorrectedasfollows intheeventofminordeviations:Activate the calibration mode at thetransmitter.Thenselect theSingle-point calibrationmodeandenterthereferencevalue measured manually. When exitingcalibration mode, the measuring chainpotentialisassignedtothelastmeasuredpHvalue.

Intheeventofmajordeviations,werec-ommendperforminga two-pointcalibra-tionorcheckingtheentirepHmeasuringequipment(refertoSect.8.9).

8.11 Automatic calibrationVarious pH transmitters offer automaticcalibration. In this mode, the transmit-terwilldetectthepHvalueofthebuffersolutionswithatoleranceof±0.5pH.Inordertoenablethetransmittertodetectthe buffer solutions, depending on theprobetypeused,thezeropointandslopevaluesdeterminedbythefirstautomaticcalibrationprocessmustbeenteredman-uallyinthetransmitter.Pleaserefertotheoperating instructions of the transmitterusedfortheinputofthetwocharacteris-ticvaluesinthetransmitter.

pH Probetype pH Reiner

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8.12 Compressed air settingFor details concerning the proper com-pressedairsettingattheelectrolyteres-ervoir,pleaserefertoSection6.4.

m If the probe is subject to proc-ess pressure inside the reactor or the pipeline, it must be ensured that the pressure inside the electrolyte sys-tem is permanently at least 0.5 bar above the process pressure. Other-wise, there is a risk of product enter-ing the probe through the diaphragm gap and clogging or contaminating the electrolyte line.

9 Operation and maintenance

9.1 RecalibrationSinceglasslinedpHprobesarenotsub-jecttoaging,recalibrationisactuallynec-essary only if calibration intervals havebeen prescribed, if the potential of thereferenceelectrodehaschanged,or ifameasuring error is suspected.Neverthe-less,werecommendverifyingthecalibra-tion approx. every 6 months in normaloperation.When recalibrating theprobe,you reach a good reproducibility of themeasuredvalue if youperforma single-point calibration with the product to bemeasured.Foradescriptionofthesingle-pointcalibrationprocess,pleaserefertoSection8.10.

9.2 Replacing the electrolyte bottle Inorder toensure faultlessoperationofthemeasuringprobe,theelectrolyte linemust always be filledwithelectrolyte.Therefore,theelectrolytebottleshouldbereplacedbeforeitisentirelyempty.

Before opening the electrolyte vessel it must be vented by turning the lower plastic thread of the electrolyte connection. Please rotate counter clockwise.

Only Pfaudler electrolyte may be used in order to guarantee the fault-less function of the probes for a long period of time.

It is recommended to activate theHOLDfunctionof the transmitterbefore replac-ingtheelectrolytebottle.ThisisdesignedtoensurethatthelastpHvaluemeasuredis maintained while the bottle is beingreplaced until the HOLD function isdeacti-vated.

As a rule, the electrolyte bottleshould only be replaced at aproducttemperature of less than 80°C and without process pres-sure. Ifthis is not possible, it should bereplacedasquicklyaspossible.

ProceduretShutoffthecompressedairsupplyandde-pressurizetheelectrolytereservoir.This isdonebyopening the threadedjointatthebottomoftheplasticinsertby approx. 2-3 turns counter-clock-wise. When the electrolyte reservoirhas been de-pressurized, immediatelyclose the threaded joint again manu-ally.

tOpen clamp on the electrolyte reser-voir, take off the upper part and re-movetheemptyelectrolytebottle.

tRemoveredcapfromthefullelectro-lytebottle.Placethebottleinthemid-dleofthelowerpartoftheelectrolytereservoirwiththeseptum(rubberplug)pointingdownward.Theseptumispen-etratedbythehollowneedlelocatedatthebottomoftheelectrolytereservoir.Forsterileapplications,thehollownee-dleandtheseptummustbedisinfect-edwithethanolbeforehand.

tReinstall the upper part of the ves-selandclose theelectrolyte reservoirtightlyusingtheclamp.

tApplyapressureof3barmin.totheelectrolytereservoir.

tOpen the venting plug on the probehead by approx. one turn and leaveit open until the electrolyte emergeswithout any bubbles. Then close theventing plug manually and clean theentireareacarefullywithwater.

tSet the necessary operating pressureat the electrolyte reservoir as de-scribedinSection6.4.

9.3 Electrolyte consumptionAt a differential pressure of 0.5 bar, aconsumptionof0.01to0.02ml/h is tobeexpected.Ifahigherdifferentialpres-sureispresent,theconsumptionmayriseto0.2ml/h.We recommendcontactingourmeasuring technologydepartment ifahigherconsumptionisnoticed.

pH Probetype pH Reiner

Figure10 Removingtheelectrolytebottle

m

20 ©PfaudlerGmbH

9.4 Cleaning and sterilization of the probes

Glass is largely insensitivetocontamina-tion. Itwillbesufficient tocheck thepHglassandtheareaof thediaphragmforproduct traces at certain time intervals.Whenyouobservemeasuringerrorsoraslowsettingbehavior,theprobemustbecleaned.Inmostcases,contaminatedare-ascanbecleanedwithwater,asolventoraliquid,non-abrasivedetergentforstain-lesssteelproducts.Donotuseanymetal-lic or abrasivematerials.When cleaningtheprobesmanually,a5-20%acid,suchasHClmaybeusedtoremovedepositsorproductfilms, if thiscleaningprocessiscarriedoutatambienttemperature.Donotuseanyfluorine-containingacidsbe-causetheystronglyattackglass.

m When handling acids, please make sure to observe the accident prevention regulations applicable to hazardous substances and their use.

CIP processesTheprobemayalsobecleanedinsidethereactor or the pipeline by the so-calledCIP method (clean-in-place). The follow-ingmediaarepermittedforcleaningtheprobe:n 1.5-2% alkaline solution, max. 85°C,max.1h

n 1.5%acid(HNO3),60°C,max.15min.n Steam134°C,max.2h.

The plant operator will define the typeandprocedureoftheCIPprocess.

ForCIPprocessesitmustbeensuredthattheadmissiblealkaliandacidconcentra-tions aswell as themaximum tempera-ture or cleaning time are not exceeded.Otherwise,thepHglasswouldbesubjectto increased corrosion. Corrosion dou-bles with every 10°C of a temperatureincreasewhenusingalkalis for cleaning.

Bycleaningwithalkalimedia,thegellayeronthesurfaceofthepHglassisdamaged.Thiswillresultinazeropointdriftwhichwill cause a short-term measuring vari-anceofupto0.5pH.Thezeropointdriftcan be corrected by reconditioning theprobe. Reconditioning (regeneration) isperformedbyasubsequentCIPprocessusing water or steam. Figure 11 showsthebehavioroftheregenerationtimeandthe measuring variance with respect tovariouscleaningagents.Alkalicleaningisperformedusing2percentNaOHat85°C.

ThepHReinerprobeisresistanttother-mal shock up to a ∆T of max. 120°C(temperaturedifferencebetweenproductandprobe).

If the probe had not been sufficientlyreconditioned, a slight zero point driftmayoccurafterthefirstcleaningprocessbecausenostablegellayerhadbeenbuiltupatthesurfaceofthepHglasspriortocleaning. This zero point drift must becorrectedbysubsequentsingle-pointcali-brationinthetransmitter.

SIP processesThe probe may also be sterilized in-side the reactor or the pipeline by theso-called SIP method (sterilize-in-place).The following media are permitted forsterilizingtheprobe:n Productn Watervaporn Alcoholsolutionsn Asepticsolutions

The plant operator will define the typeandprocedureoftheSIPprocess.

ThepHReinerprobeisresistanttother-mal shock up to a ∆T of max. 120°C(temperaturedifferencebetweenproductandprobe).

If the probe had not been sufficientlyreconditioned,aslightzeropointdriftmayoccur after the first sterilizationprocessbecausenostablegellayerhadbeenbuiltupatthesurfaceofthepHglasspriortosterilization.Thiszeropointdriftmustbecorrectedbysubsequentsingle-pointcali-brationinthetransmitter.

Figure11 ReconditioningthepHReinerprobeaftercleaningwithalkali

MT0078_1E

135°CSteam

95°CWater

80°CWater

25°CWater

∆ pH0,1

0

–0,1

–0,2

–0,3

–0,4

–0,50 10 20 30 40 50 60 70 80

Regeneration time (min)after30minCIPusing2percentNaOHat85°C

pH Probetype pH Reiner

21©PfaudlerGmbH

9.5 Troubleshooting

pH Probetype pH Reiner

Malfunction Cause Remedy

Display oscillates when touching the electrolyte hose a Insufficientlyvented Venting

Identical display with different buffer solutions a PoreinthepHglass(productisincontactwiththederivativelayer)

RepairbyPfaudler

b Cableortransmitterinputdefective Replacement

Zero driftZero point no longer in permitted rangeZero drifts when venting the probe

a Referenceelectrodeexhaustedordefective HavePfaudlerreplacereferenceelectrode

b Defectivecableorinsulationfaultcausedbymoisture

Checkcable,replaceifnecessary,Removemoisturewithhotairblower

Slope too low or very slow response a Limeorotherdeposits DeterminepotentialatpH3andpH7Slope≥55mV/pHat25°CKeepprobefor30minin10%HClsolution,rinseinwaterandmeasureagain

b Ifacidtreatmentisnotsuccessful InspectionbyPfaudler

c Insulationfaultduetomoisture Checkcableandreplaceifnecessary,removemoisturewithhotairblower

22 ©PfaudlerGmbH

pH Probetype pH Reiner

9.6 Spare parts list

Spare parts for the probe Part no.ThreadadapterM20madeof1.4404 595841-ThreadadapterPG13.5madeof1.4404 5958411Threadadapter3/4“madeof1.4404 5958412Threadadapter1“madeof1.4404 5958413

Spare parts for Ingold adapterInstallationadapterDN25/M20 2556071Spacertube16x1.5,length69mm,madeof1.4571 595921-SupportringforspacertubemadeofPTFE 595922-UnionnutG11/4“madeof1.4571 032126-O-ring10.0x2.5mmmadeofEPDM K07896-O-ring20.0x2.5mmmadeofsilicon 024333D

Spare parts for Pfaudler aseptic adapterInstallationadapterDN30/M20 2556081Spacertube16x1.5,length69mm,madeof1.4571 595921-SupportringforspacertubemadeofPTFE 595922-UnionnutG11/4“madeof1.4571 032126-O-ring10.0x2.5mmmadeofEPDM K07896-O-ring23.39x3.53mmmadeofEPDM 024365D

Spare parts for the electrolyte reservoir Part no.Electrolytereservoir,complete,withoutlevelmonitoring 595879-Electrolytereservoir,complete,withlevelmonitoring 5958791-PlasticinsertmadeofPOM,complete 5958722-ClampgasketDN100madeofPerbunan(NBR) 026799-O-ring28.0x4.0mmmadeofsilicon,blue K09691-Hollowneedlemadeofstainlesssteel 055301-O-ring8.0x1.5mmmadeofsilicon,transparent K07852-Electrolytehose4.0x1.5,length5m,madeofPTFE, 595988-prefabricated,includingconnectorandcouplingElectrolytehose4.0x1.5,length5m,madeofPTFE, 0273591withoutconnectorandcouplingConnector,self-locking,madeofEPDM 026927-Coupling,self-locking,madeofEPDM 026360-StraightmaleunionwithO-ringDN4/6,G1/4”,madeofPVDF 027375-ClosingplugM12x1mmmadeofPVDF 256463-O-ring10.0x2.0mmmadeofViton 024105D

other spare parts Part no.Electrolyte3molKCl,sterile,1literplasticbottle 595925-1literplasticbottle,empty,tobefilledwithethanol 595929-Demineralizedwater,sterile,1literplasticbottle 595928-pHReinerconnectioncord,3m,withVariopincoupling,black K07891-pHReinerconnectioncord,5m,withVariopincoupling,black K07892-

23©PfaudlerGmbH

TYPE ELAUGUST 2006

24 ©PfaudlerGmbH

Figure12 Installationadapterassembly

Annex AInstallation adapter assembly

ThepHprobecanbefittedtovariousin-stallationadapters

m When handling the probe, please avoid hitting the sensor with steel or stone because the glass may get damaged.

Procedure:tpH-Reinerwithoutadapterscrew. 1

The adapter screw – M20 part no.595841 –must be pushed onto thesensorheadandfastenedtotheprobeheadusingfourM3headlesssetscrewsinthegrooveontheprobehead. 2

t2 pce PTFE support rings, part no.595922-. 3

tPushthe1stPTFEsupportringontotheprobe. 4

tPushthespacertubeontotheprobe. 5 tFitbothpartstotheadapterscrew. 6 tPush the second support ring tothescrewandpressitintothespacertube. 7

tPlacetheO-ring10x2.5inpositionandrollittoitsposition. 8

t Ifnecessary,pushasuitableunionnutfor fastening the installation adapterontotheassembly. 9

tCarefullypush the installationadapteronto the probe. The assembly of theinstallationadaptersalwaysfollowsthesameprocedure,regardlessofthetypeofadapter.10

tHold down the adapter screw andfirmly tighten the installation adapterclockwise.11

If the O-ring has been sufficiently pre-stressed,thegapwillbeclosed.12

1

2

3

4

5

6

25©PfaudlerGmbH

Annex AInstallation adapter assembly

8

9

10

12

11

7

Figure13

26 ©PfaudlerGmbH

Notes

27©PfaudlerGmbH

Notes

The information provided in this documentation corresponds

to the state of the art at the time of printing. It is published

in good faith. However, we will accept no warranty claims

based on the information provided in this documentation. We

reserve the right to include improvements, amendments and

new findings in this documentation without prior notice. The

actual design of products may deviate from the information

contained in the calatoge if technical alterations and product

improvements so require. The proposal made by Pfaudler for

a concrete application will be binding in such cases.

The present documentation is made available free of charge

to our customers and other interested parties. The right to

print or copy this documentation, or any parts there of, or to

convert the same into electronic form shall be subject to our

written permission.

All rights reserved by us.

Pfaudler Werke GmbH

P.O. Box 1780 D-68721 Schwetzingen

Pfaudlerstraße D-68723 Schwetzingen

Phone +49 6202 85-233

Telefax +49 6202 85-273

E-mail info@pfaudler-instrumentation.com

www.pfaudler-instrumentation.com