INSTRUCTION MANUAL
MODEL 212R
THERMAL CONDUCTIVITY
ANALYZER
DANGER
HIGHLYTOXICANDORFLAMMABLELIQUIDSORGASESMAYBEPRESENTINTHISMONITORINGSYSTEM.
PERSONALPROTECTIVEEQUIPMENTMAYBEREQUIREDWHENSERVICINGTHISSYSTEM.
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TIMEEVENAFTERTHEPOWERISTURNEDOFFANDDISCONNECTED.
P/NM73212
11/29/07
ECO#07-0182
ONLYAUTHORIZEDPERSONNELSHOULDCONDUCTMAINTENANCEAND/ORSERVICING. BEFORE
CONDUCTINGANYMAINTENANCEORSERVICINGCONSULTWITHAUTHORIZEDSUPERVISOR/MANAGER.
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Thermal Conductivity Analyzer
Table of Contents
Model 212R
1 Introduction
1.1 Method of Analysis.......................................................5
1.2 Sensitivity ....................................................................6
1.3 Stability ........................................................................6
1.4 Special Consideration .................................................6
1.5 Physical Configuration.................................................6
2 Installation
2.1 Location .......................................................................7
2.2 Electrical Requirements & Connections ......................7
2.2.1 Primary Power ...............................................8
2.2.2 Signal Output .................................................8
2.2.3 Regulating Transformer..................................8
2.2.4 Completion & Inspection................................9
2.3 Gas Requirements & Connections...............................9
2.3.1 Reference Gas...............................................10
2.3.2 Zero Gas ........................................................10
2.3.3 Span Gas.......................................................10
2.3.4 Installation of Cylinder Supplies ....................11
2.3.5 Sample Pressure ...........................................11
2.3.6 Interconnecting Lines.....................................11
2.3.7 Vent Lines ......................................................12
3 Startup
3.1 Preliminary...................................................................12
3.2 Reference Gas Flow ....................................................13
3.3 Zero Gas Flow .............................................................13
3.4 Warmup........................................................................13
3.5 Zero Standardization ...................................................13
3.6 Span Standardization ..................................................14
3.7 Bypass .........................................................................14
3.8 Sample Mode...............................................................15
4 Routine Operation
4.1 Flowrate .......................................................................15
4.2 Supporting Gas Supplies.............................................16
3
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Thermal Conductivity Analyzer
Model 212R
4.3 Standardization............................................................16
5 Periodic Maintenance
5.1 Heater Fan ...................................................................17
6 Troubleshooting
6.1 Preliminary...................................................................17
6.1.1 Electrical Checks ...........................................17
6.1.2 Sampling System Checks..............................18
6.1.3 Summary of Preliminary Checks....................18
6.2 Loss of Zero Control.....................................................18
6.2.1 Dynamic Balance Procedure .........................19
6.3 Correct Operation.........................................................20
6.4 Incorrect Operation.......................................................21
6.4.1 Analyzer Leak Check.....................................21
6.4.2 Temperature Control Check ...........................22
7 Calibration Data
7.1 Ranges ........................................................................24
7.2 Output Signal ...............................................................25
7.3 Span Setting ................................................................25
7.4 Recommended Accessory Gases................................25
7.4.1 Reference Gas...............................................25
7.4.2 Zero Gas ........................................................25
7.4.3 Span Gas.......................................................26
Appendix
A
Recommended 2-Year Spare Parts List .......................26
A
Drawing List .................................................................27
A Specifications...................................................................... 28
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Thermal Conductivity Analyzer
Model 212R
1.
INTRODUCTION
1.1
Method of Analysis.
The Model 212R compares the thermal conductivity of a sample gas to
that of a fixed composition reference gas and produces an electrical output
signal that is calibrated to represent the difference between the two gases.
Due to the nonspecific nature of thermal conductivity measurement,
standard gases of known composition will be required to calibrate the ana-
lyzer. The accuracy of the analysis will be dependent on the accuracy to
which the composition of the standard gases is known.
The measuring unit is a four element hot wire cell that forms one-half of
an alternating current bridge circuit. Two of the hot wire elements are ex-
posed to the sample gas, and two to the reference gas. The other half of the
bridge circuit is formed by the center tapped secondary winding of a trans-
former.
With reference and zero standardization gas flowing, the bridge circuit
is balanced at one end of the measurement range. A span standardization gas
containing a known concentration of the component of interest is then
introduced into the sample path, and the resulting error signal generated by
the now unbalanced bridge circuit is calibrated to represent the span gas
mixture. The concentration of the component of interest in the span gas is
predicated by the specified ranges of the analysis. After the instrument has
been standardized the electrical error signal is directly related to the compo-
nent of interest content of the sample gas.
The magnitude of the measuring bridge error signal is much too small to
drive an indicating or recording instrument. A 100:1 step-up transformer,
followed by an electronic amplifier stage, is utilized to amplify the error
signal to an acceptable amplitude for demodulation. The signal is then
conditionedappropriatelytodriverecordingequipment.
5
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Thermal Conductivity Analyzer
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1.2
Sensitivity.
Differencesinthermalconductivitythatproduceameasuringbridgeerror
signalof 0.25microvoltswillbesensedbytheanalyzer.
1.3
Stability.
Internalvariables,otherthanthesamplegas,thatcouldproducevariations
intheoutputsignalarecarefullycontrolledbytheModel212R. Zerodriftis
approximately2%ofthefinerangeina24hourperiodofoperation;further-
more,thedriftisbidirectionalwithaproperlyinstalledanalyzerandisrelatedto
grosschangesinambienttemperature. Thevariables,bothinternalandexternal,
thatcanaffectthestabilityoftheanalyzerwillbedealtwithindetailintheinstal-
lationandtroubleshootingsectionsofthismanual.
1.4
Special Consideration.
ConsiderationofUsingthe212RtoMeasureH2,ormeasureothercompounds
in H2. H2 in the gas state can be assume of one tow states, para H2, or ortho
H2. EachhasitsownThermalConductivityValue. Thesedifferbyabout10%
fromoneanother.
Sothismustbetakenintoconsiderationwhenattemptingtousethe212RonH2
streams.
WewouldrecommendoneconsultWikipedia.comorothersourcestolearn
moreaboutthesetwostatesofH2andhowthethermalconductivityofthegas
streamvarieswiththestate.
IfforinstanceoneisusingpureH2asareferencegas,andthisgasisinthepara
stateassociatedwithcryogenicH2recentlyvaporized,andthisisthencompared
tocylinderH2whichmaybeinadifferentstate,thenconsiderablemeasurement
errorscanresult.
ContactTeledyneforfurtherguidanceorinformationonyourspecificapplica-
tion.
1.5
Physical Configuration.
Theanalyzerishousedinasheetsteelcasethatisdesignedtoflushmount
withinanequipmentpanel. Electricalcontrols,aswellasanintegralgascontrol
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Thermal Conductivity Analyzer
Model 212R
panel,arelocatedimmediatelybehindahingedfrontaccessdoor.Theanalyzer
issuitableforinstallationinashelterednon-hazardousarea.
Arecordingand/orindicatingdevicewillberequiredtotransducethe
electricaloutputsignalintoreadableinformation.
2.
INSTALLATION
2.1
Location.
Theanalyzershouldbepanelmountedinanuprightpositioninanarea that
is notexposedtothefollowingconditions:
1. Directsunlight.
2. Drafts of air.
3. Shock and vibration.
4. Temperatures other than that one would expect to see in
airconditioned, temperature controlled office of lab enviroment.
The 212Rshouldnotbemountedoutdoorsorsubjecttemperature fluc-
tuationsbeyond2or3degrees.
Theanalyzershouldbeplacedascloseaspossible,subjecttotheafore-
mentionedconditions,tothesamplepoint.
Outlinediagramsofbothunitswillbefoundinthedrawingsection.After
thecutouthasbeenmadeintheequipmentpanel TAIrecommendsthatthe
analyzerbeusedasatemplatetolayoutthefourmountingholes.Suchaproce-
durewillcompensateforsheetmetaltoleranceerrors.
2.2
Electrical Requirements and Connections.
Provisionshavebeenmadetoaccommodatethethreeexternalcircuit
connectionsrequiredbytheanalyzer. Accessholesononesideoftheanalyzer
case(seeOutlineDiagram)areprovidedfortheinstallationoftheconduitand
electricalwiring. Allthreecustomerconnectedcircuitsaretobeterminatedon
thebarrierterminalstripidentified“TS1”.
Toinstalltheconduitandwiring,theinnerhorizontallyhingedpanelmustbe
opened (to open the panel, turn the fastener screw at the top of the Panel a 1/4
turnccw).Whileinstallingtheconduitandwiringbecarefulnottodisturbthe
foaminsulationliningtheinteriorofthecaseanymorethanisabsolutelyneces-
sary.
7
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Thermal Conductivity Analyzer
Model 212R
IMPORTANT: The foam lining the interior of the analyzer is an
integral part of the environmental temperature
control system. Removal or destruction of this
lining will result in erratic instrument perfor-
mance.
2.2.1 Primary Power.
Asourceofsinglephase,105to125volt,60cyclepowerwillberequired
tooperatetheanalyzer. Themaximumpowerconsumptionoftheanalyzeris
500watts.
NOTE: The analyzer is also available for 50 cycle operation
with special modifications and accessories.
RefertotheInterconnectionDiagraminthedrawingsectionofthemanual
andconnectthepowerandgroundwiringasshown. Besuretopolarizethe
powerserviceconnectionsasindicated. Whenconnectingthewires,donot
leaveanexcessiveamountofslackwithintheanalyzer. Twovacuumtubesare
locatedjustbelowthewiringareaandthewiringshouldbeinstalledtobewell
clearofthem.
2.2.2 Signal Output.
Connectatwoconductorshieldedcablebetweentheanalyzerandrecord-
ingequipment. Besuretoobservetheproperpolarityatbothinstruments.
Connecttheshieldofthecableontheindicatedterminalattheanalyzeronly,and
cutbackandinsulatetheshieldattherecorder.
NOTE: Connecting the shield at both ends of a cable when
dealing with low level circuits can create a ground
loop between two instruments. Improperly installed
shielding can produce more noise in a low level circuit
than no shielding at all.
2.2.3 Regulating Transformer.
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Thermal Conductivity Analyzer
Model 212R
Runthecableattachedtothetransformerunitinthroughtheaccesshole
that is equipped with the cable clamp and terminate it as specified on the
interconnectiondiagram.
2.2.4. Completion and Inspection.
After the electrical connections have been completed, slide any excess
slack back into the conduits so that the installed wiring is not in contact with
the components mounted on the analyzer chassis.
Removethethreefoamstripsthataretapedtotheinsideoftheanalyzer
doorandusethemtostufftheconduitopenings. Itisimportantthatthese
openings be as well sealed as possible.
Checktoseethatthetemperaturecontrolprintedcircuitboard,andall
vacuumtubesarefirmlyseatedintheirrespectivesockets.
Closeandlatchthecontrolpanel. Thereshouldbenofurtherneedtohave
accesstotheinterioroftheanalyzer. Allcontrolsandadjustmentsarearranged
sothattheycanbemanipulatedwithoutdisturbingthedelicatetemperature
equilibriumoftheinstrumentinterior.
2.3
Gas Requirements and Connections.
Beforeattemptinginstallationofthesampleandsupportinggaslinesand
accessoriesgivecarefulconsiderationtothefollowingimportantinstallation
notes.
Note #1: Itisabsolutelynecessarythatallconnectionsandcomponents
inthegascontrolsystemaheadofthemeasuringcellbeleak
free. TowardthatendTAIhastestedtheintegralsampling
systemunderpressurewithasensitiveleakdetectorand
certifiesthattheanalyzerisleakfree.
Note #2: Usenosolderconnectionsinthesystem. Solderingfluxes
outgas into the sample lines and produce erratic output
readings. Acid type soldering fluxes actually attack and
permanently change the characteristics of the detector cell
measuringelements.
Note #3: All sample system tubing should be new and clean. Many
gases and vapors are absorbed by dirt or oxide coatings on
tubing walls. These gases and vapors are released as the
ambient temperature rises. Because of the high sensitivity of
the analyzer, this absorption-desorption phenomenon can
9
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Thermal Conductivity Analyzer
Model 212R
causealargefluctuationinoutputsignal.Forbestresults,use
electropolished SS tubing
Note #4: Becauseofthediffusionofairthroughcompositionmaterials,
only dual stage SS regulators with metallic diaphragms should
be used in conjunction with the sample and supporting gas
supplies.
Note #5: Regulatorsmustbethoroughlypurged(burped)priortouse.
2.3.1 Reference Gas.
Acylinderofgasoffixedcompositionisrequiredasthereferencefor
comparisonwiththesamplegas. Atotallackofimpuritiesinthereference
would be ideal but is not necessary. An impurity concentration of up to 50%
ofthenarrowestrangeofinterestistolerable. Theexactcompositionofthe
referencegasisacademicaslongastheuseriscertainthatitfallswithinthelimits
specifiedinSection7ofthemanual. Theimportantconsiderationisthatthe
compositionofthereferencegasremainunchangedwheninuse.
NOTE: When it becomes necessary to replace the reference
gas, the analyzer will have to be recalibrated.
2.3.2 Zero Gas.
A supply of gas, composed of the background gas of the analysis and
the lowest attainable concentration of impurity, will be required to standard-
ize one end of the ranges of interest. The composition of the zero gas must
be known to the same exactitude expected of the analysis. TAI suggests that
the gas be obtained from a supplier that will certify its composition. Recom-
mendations as to the composition of the gas will be found in Section 7 of the
manual.
2.3.3 Span Gas.
A supply of gas, composed of the background of the analysis plus a
known concentration of the component of interest, will be required to stan-
dardize the sensitivity of the analyzer. Again, the composition of the gas
must be known to the same order of accuracy expected of the analyzer.
Analysis and certification of the composition is desirable. Specific recom-
mendations governing the composition of the span gas will be found in
Section 7 of the manual.
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Thermal Conductivity Analyzer
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2.3.4 Installation of Cylinder Supplies.
Thereferenceandstandardgascylindersshouldbeinstalledasclosetothe
analyzeraspossible. Eachcylindershouldbeprovidedwithadualstage,
metallicdiaphragm,pressurereducingregulator. Wheninstallingtheregulators,
crackthecylindervalveopensothatgasisflowing. Thisprocedurewillprevent
airfrombeingentrappedintheregulator,andeliminateacommonsourceof
supportinggascontamination. Improperinstallationofacylinderregulatorcan
appreciablychangethecompositionofastandardgas.Airtrappedintheregula-
torwilldiffusebackintothecylinder,andtheimpurityconcentrationofthe
compositionwillbealtered. Whendealingwiththezerogas,thealterationofthe
compositioncanbesignificant.
Onceinstalled,priortouse,theregulatorsforreference,spanandzero
gasesmustbepurgedbyalterativelypressuringthefirststage,withthesecond
stageoff,thenbleedingoutthefirststagebyopeningthesecondstage,backand
forth severaltimes.
Note: Make sure to close the cylinder prior to bleeding the first stage
through the second.
2.3.5 Sample Pressure.
Thesamplepointshouldbeequippedwithametallicdiaphragmpressure
regulatorandthepressurereducedtobetween10and50psig. Theregulator
shouldbeinstalledasclosetothesamplepointaspossibletominimizesample
linelagtime.
2.3.6 Interconnecting Lines.
Theinletandventconnectionsareidentifiedontheanalyzeroutlinedia-
gram. Theconnectionsarestainlesssteel1/8"femalepipecouplingsthatare
braisedintoagasconnectorbarmountedwithintheanalyzer. Thebraisedpipe
couplingwasselectedasatransitionsothatthetorquegeneratedduringinstalla-
tionoftheexternalsystemwouldbeisolatedfromtheinternalsystem. Bulkhead
typefittingscanbeaccidentlytwisted,andleakspromotedinhardtoreachareas
withintheanalyzer. TAIsuggeststhat1/4"tubingandadapterfittingsbeused
throughouttheexternalsamplingandsupportinggassystem.
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Thermal Conductivity Analyzer
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2.3.7 Vent Lines.
Thesamplepath,referencepath,andanintegralbypasssystemventfrom
separateportsattherearoftheanalyzer. Whereverpossible,TAIrecommends
thatthegasesbepermittedtoventdirectlytotheatmosphere.Ifitisnecessary
tocarrythesegasestoaremoteareathefollowingprecautionsmustbeob-
servedwheninstallingtheventlines:
1) Theventlinesmustbe1/4"tubingorlargersothatnobackpressure
resultingfromrestrictedflowisexperiencedbythemeasuringcell.
2) Thesampleandreferencepathsmustventintoanareathatexperi-
ences the same ambient pressure conditions.
3) Theambientpressureattheventlocationshouldundergonomore
thannormalbarometricpressurefluctuations.
4) Theventlinesmustbeinstalledsothatwateranddustcannotaccu-
mulate in them.
Apressuredifferentialexistingatthecellbetweenthereferenceandsample
willresultinacorrespondingchangeinoutputsignal. Thereferenceandsample
pathflowmetersarelocatedupstreamfrom thecellsothatbothcellpathscan
ventdirectlytoatmosphere. Therandombounceofthefloatsintheflowmeters,
whenlocateddownstreamfromthemeasuringcell,canproduceupto5%noise
ontheoutputsignal.
3.0
3.1
STARTUP
Preliminary.
The following preliminary steps should be accomplished before apply-
ing power or starting gas flow.
1. Check the integral gas control panel and be sure that all valves are
closed (fully cw). Do not jam the sample, reference, and bypass
meteringvalves.
2. Place the “RANGE” switch on the #2 position.
3. Set the “SPAN” control to the reading recorded in Section 7 of the
manual.
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Thermal Conductivity Analyzer
Model 212R
4.Determinewhatthesamplepressureisandsettheoutputpressureof
the cylinder gas supplies to agree with the sample pressure. This
procedure, although not absolutely necessary, will minimize flow
adjustments when the sample path is switched to the various inputs.
5. Turn the analyzer and recorder power switches to “ON”.
3.2 Reference Gas Flow.
Openthereferencegasthrottlevalveadjacenttothe “Ref.Flow”meter,
andsetthevalveforanindicatedflowrateofbetween0.1and0.3scfh. Since
theactualsettingisnotcritical,TAIsuggeststhattheflowbesetat0.1scfhto
conservethereferencegassupply.
3.3
Zero Gas Flow.
Openthe“ZERO”valve(ccwuntilareleaseintensionisfelt),andadjust
thethrottlevalvetotherightofthe“SAMPLEFLOW’flowmeterforanindi-
catedflowrateof0.3scfh.
3.4
Warmup.
Awarm-upperiodoftwenty-four(24)hoursisrecommendedtostabilize
theinterioroftheanalyzeratthecontroltemperaturelevel. Untilthemeasuring
celltemperaturehasequilibratedwiththecontroltemperature,theoutputsignal
willdrift.
Duringthewarmupperiod,checktherecorderperiodically. Asthedrift
rate decreases, increase the sensitivity by moving the range switch towards
Range #1.
IMPORTANT:
ThezerocontrolwillhavelittleornoeffectuntilRange#1isreached.Ifthe
recorderisoffscaletowardselectricalzero(negativesignal)after24hoursof
runningonzerogas,usetheprocedureoutlinedinSection6.2. Thedriftratewill
decreaseexponentially. Whentherateofchangeslowstoapproximately1%
perhour,placethe“RANGE”switchonposition#1andreadjustthe“ZERO”
controlsothattherecorderisreadingmidscale. Donotattempttocalibratethe
analyzeruntiltherecorderindicationstabilizes.
3.5
Zero Standardization.
13
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Thermal Conductivity Analyzer
Model 212R
Aftertheanalyzerstabilizesadjustthe"ZERO"controluntiltherecorder
indicatestheimpurityconcentrationofthezerogascomposition. Besurethat
therangeswitchisonposition#1andthatthesamplepathflowrateis0.3scfh.
NOTE if the"ZERO" or "FINE ZERO" pot runs out of adjustment and
the analyzer can not be calibrated, set this pot back to mid-scale. Then use
the "COURSE ZERO" pot to readjust the zero calibration as close as pos-
sible to zero calibration. And last use the "ZERO" ot "FINE ZERO" pot to
fine adjust the zero calibration.
3.6
Span Standardization.
Afterthezerohasbeenstandardized,switchtheselectorvalveto"Span",
andresetthesamplepathflowrateto0.3scfh. Therecordershouldcometo
balanceon,orcloseto, thecompositionofthespangas.
Theanalyzerisfactorycalibratedtomakesurethattheoutputislinearover
allthreerangesofinterest. Calibrationisachievedwithmixingblocktechnique
andthespansettingrecordedinSection7isderivedatthattime.
Iftheanalyzerperformedasdescribedinthewarm-upprocedure(Section
3.4),andfailstocloselyapproximatethecompositionofthespangas,thereis
groundsfordoubtingthespangasmixture. Becauseofthedifficultyinvolvedin
obtainingpreciseanalysisofsmallamountsofimpuritiesincylindergas,and
becauseoftheeasewithwhichthegascanbecontaminatedsubsequentto
analysis,anylargeerrorinresponsetothespangasshouldbesuspect. Insucha
caseTAIrecommendsthattheanalyzerbeoperatedattherecommendedspan
settinguntilthespangasisreanalyzed.
Ifadjustmentofthespancontrolisnecessarytocompensateforminor
discrepanciesbetweentherecordedsettingandthespangasreading,TAI
suggeststhatthezeroandspan proceduresberepeateduntilnofurtheradjust-
mentisrequired.
3.7
Bypass.
Theintegralgascontrolpanelfeaturesabypassflowmeterandthrottle
valve that is located downstream from the input manifold (see the analyzer
piping schematic in the drawing section). The bypass system can be used to
speed the response of the analyzer to changes in the process. The bypass
flowmeter will indicate flowrates that are a factor of ten greater than the
sample path flowmeter. TAI recommends that the bypass system be used
whenever the sample path is switched and particularly after using the span
gas. The time required for the analyzer to stabilize on an impurity concentra-
tion within the limits of Range #1, after having been exposed to a concentra-
tion within the limits of Range #3, is not a function of cell response which is
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Thermal Conductivity Analyzer
Model 212R
virtuallyinstantaneous. Recoveryisafunctionofhowlongittakestopurgethe
samplingsystemupstreamfromthecell.Acceleratingthesamplepathflowrate
willspeedtheresponse.
NOTE:
TAI recommends that some bypass flow be permitted
at all times. The bypass throttle meter is a part of the
input manifold. Being so located means that the
throttle valve lies between the sample side of the cell
and atmosphere.
Without some bypass flow it is possible that atmo-
sphere could diffuse into the sample line. Do not
attempt to use the throttle valve as a shut off valve.
Jamming the valve will damage the metering needle.
3.8Sample Mode.
Aftertheanalyzerhasbeenstandardized,switchtheselectorvalveto
"Sample". Set the bypass flow so that the float is visibly elevated from the
bottom of the tube and then readjust the sample flowrate to 0.3 scfh. No
furtheradjustmentsarerequired.
NOTE: Although the bellows type valves used in the input
manifold are among the best available, TAI suggests
that the span gas be turned OFF at the cylinder when
not in use, and the span line relieved of pressure
before closing the analyzer span valve. Such a proce-
dure will eliminate any possibility of the span gas
diffusing into the sample path of the analyzer. Nor-
mally, the recommended span gas composition con-
tains a component of interest content of 3/4 the coars-
est range of analysis. The component of interest
content of the sample gas, on the other hand, is usu-
ally well within the finest range of analysis. Instrument
sensitivity in Range #1 is 100 times greater than in
Range #3. The user can readily see what even a
minute rate of span gas diffusion would do to the
validity of a Range #1 analysis.
4.
ROUTINE OPERATION
Flowrates.
4.1
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Thermal Conductivity Analyzer
Model 212R
Thereferenceandsampleflowratesshouldbecheckeddaily. Theinstru-
mentissomewhatflowsensitive. OperatingonRange#1achangeinflowrateof
0.1scfhwillcauseacorrespondingchangeinsensitivityoffrom1to20%of
scale. Onthecoarserranges,thechangeinsensitivitywouldbeundetectable.
Thesamplepathflowrateshouldbemaintainedat0.3scfh,thereference
pathflowrateat0.1scfh,andthebypassflowmeterfloatshouldbeslightlyabove
thebottomoftheindicatorglass.
4.2 Supporting Gas Supplies.
Supportingcylindergassuppliesshouldbecheckedfrequentlyonaroutine
basiswithparticularattentionfocusedonthereferencegas. Asparecylinderof
referencegasshouldbeavailableatalltimes. Whenthecylinderpressuredrops
below100psigthereferencesupplyshouldbereplacedastheoperationofthe
regulatorisquestionableatpressuresbelowthispoint.
Whenreplacingsupplycylinders,besuretobleedthegasthroughthe
cylinder valve while installing the pressure regulator (see Section 2.3.4). It is
also advisable to check the connections with soap water whenever a supply
cylinder is changed.
4.3
Standardization.
Theanalyzermustbecompletelyrestandardizedwheneverthereference
gassupplyisreplaced. Barringunforeseendifficultieswiththeanalyzer,re-
standardizationshouldnotbenecessarybetweenreferencecylinderreplacement
periodsiftheanalyzerisruncontinuously. Iftheanalyzerisshutdownforlong
periodoftimeusethestartupprocedure(initsentirety)whenoperationistobe
resumed.
NOTE: TAI strongly recommends that the analyzer run con-
tinuously with gas flowing in both the sample and
reference paths. During inactive periods arrange the
input manifold so that zero gas is flowing. Gas sup-
plies can be conserved by reducing the sample and
reference path flowrates to less than 0.1 scfh and
closing off the bypass flow completely.
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Thermal Conductivity Analyzer
Model 212R
Duetothedelicatebalanceofthethermalconductivitycellemployedinthe
analyzer,exposuretotheatmosphereinanuncontrolledtemperatureenviron-
mentisundesirable. Afterextendedshutdownperiodsmanydaysofoperation
mayberequiredfortheanalyzertore-stabilize.
5.
PERIODIC MAINTENANCE
Heater Fan.
5.1
Theheaterfanistheonlycomponentwithintheanalyzerthatrequires
periodic attention. Whenever the reference gas is replaced the motor bear-
ings will require a few drops of light machine oil. Since oiling the fan motor
necessitatesopeningtheinnerdooroftheanalyzer,theinstrumentwillrequirethe
necessarytemperatureequilibratingtimeafterthedoorisclosed. Withzerogas
flowingbesurethattheanalyzerhasstabilizedontheRange#1positionbefore
re-standardizationisattempted.
6.
TROUBLE SHOOTING
6.1
Preliminary.
Iftheanalyzerissuspectedofincorrectoperation,asapreliminaryto
evaluation, always arrange the input manifold so that zero gas is flowing
through the sample path of the analyzer. Never attempt to evaluate the
performance of the instrument with sample gas flowing.
Analysisbythermalconductivityisnonspecificinnature. Athermalcon-
ductivityanalyzerwiththefinerangesensitivityoftheModel212Rwill respond
tomanyinfluencingfactorsotherthanthecomponentofinterest;particularly
whenoperatedatRange#1sensitivity.
It is necessary, therefore, to eliminate as many external variables as
possible if the performance of the analyzer is to be assessed. Programming
the analyzer for zero gas places both paths of the measuring cell on relatively
reliablecylindergassources.
6.1.1
Electrical Checks.
17
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Thermal Conductivity Analyzer
Model 212R
Checktoseethatboththeanalyzerandrecorderarebeingfurnished
electrical power. Check to see that the analyzer and recorder fuses are intact.
Check all electrical connections outside of the analyzer.
6.1.2 Sampling System Checks.
Besurethatthereisanadequatesupplyofreferencegasandthatthe
sample and reference path flowrates are correct. Check to see that there are
no obstructions in the vent paths from the analyzer. Check all external
plumbing connections for leaks with soap water.
6.1.3 Summary of Preliminary Checks.
Theanalyzerinnerdoorshouldnotbeopenedandnoadjustments,beyond
manipulationofthenormallyusedcontrols,shouldbemadeuntilalltheafore-
mentionedpreliminarieshavebeencompletedandanynecessaryremedial
repairseffected.
6.2
Loss of Zero Control.
IflossofzerocontrolonRange#1isexperiencedduringinitialstartupor
afterthereferencegassupplyhasbeenchanged,thedynamicbalanceprocedure
mustberepeated.
Lossofzerocontrol,undersuchcircumstances,indicatesthattheimpurity
concentrationwithinthereferencegasisdifferentthanthatofthegasusedduring
factorycheckout(orthepreviouscylinder)anddoesnotinitselfindicatea
defectiveanalyzer.
Theanalyzerwasadjustedatthefactorytohaveazerobalanceatcloseto
themidpointofthezerocontrolpotentiometer(dualdialreadingof500)witha
commonsourceofhighpuritycylindergassupplyingboththesampleand
referencepathsofthecell. Iftherecorderisoffscaleandcannotbereturned
withthezerocontrol,thedynamicbalanceproceduremustbeemployedto
restorecontrolbeforefurtherconclusionsastoinstrumentperformancecanbe
made.
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Thermal Conductivity Analyzer
Model 212R
6.2.1
Dynamic Balance Procedure.
Themeasuringbridgecircuit(seeschematic)incorporatestwo 10 turn
potentiometersthatareutilizedtocompensateforminutedifferencesinthe
resistive and reactive properties of the hot wire elements and the center
tapped secondary of the bridge transformer in the reference and zero gas
relatedtotheapplication.
Thepotentiometersareofthescrewdriveradjustmenttypeandare
equippedwithshaftlockingassembliesthathavebeenfactoryadjustedtocreate
enoughfrictionsothattheshaftwillnotchangepositioninshipment.Thepotenti-
ometersarelocatedontheamplifierchassis,andarecontrolledthroughtwo
holesidentified“RESISTIVE”and“REACTIVE”ontheinnercontrolpanel.
DO NOT OPEN THE INNER PANEL OF THE ANALYZER TO
GAIN ACCESS TO THESE CONTROLS. The balance adjustments
should not be disturbed if the analyzer is not up to operating temperature.
Correct bridge balance can only be achieved at operating temperature be-
cause of the inherent thermal junctions within the potentiometers themselves.
The minute voltages produced by contact between the dissimilar materials
within the potentiometers are effectively balanced out in the procedure when
it is accomplished at operating temperature. Because the voltage generated
by these junctions varies with temperature, and because the analyzer will
resolve a 0.25 microvolt change in bridge voltage, temperature stability is a
mandatory prerequisite to the dynamic balance procedure.
To restore zero control within the limits of Range # 1, employ the
followingProcedure:
1) Withzerogasflowing,adjustthesampleandreferencegasflowme-
terstothesamevaluebetween0.1and0.3scfh.
2) Set the ZERO potentiometer to 500.
3) Connectavoltmetertotheinstrumentsignaloutput. Connectan
oscilloscope to the probe point an d set the sweep rate to 5
milliseconds. Set the voltage level so ± 15 volts can be read.
4) If a reading of +15 or –15 volts is indicated on the oscilloscope
with the RANGE switch set to Range # 1 the instrument is
significantly unbalanced. Set to Range #2 and proceed to step 4).
If the voltage is lower in magnitude than + or – 15 skip down to
step 6).
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Thermal Conductivity Analyzer
Model 212R
5) Usingascrewdriverthathasashaftdiameterof1/8”andashaft
length of at least 6”, turn the “Reactive” balance adjustment all
the way counterclockwise (CCW) until the potentiometer stop
pointisreached. Turntheadjustmentbackclockwise(CW)5full
turnstocentertheadjustment.
6) Turnthe“Resistive”balanceadjustmentallthewayclockwise(CW)
untilthepotentiometerstoppointisreached.
7) Slowly turn the “Resistive” adjustment until the output reaches its
lowest value. If the reading is negative adjust to the most nega-
tivevaluepossible.
8) Turnthe“Reactive”balanceadjustmentslowlyCWandCCWto
obtain the lowest possible output value. Again, if the reading is
negative adjust to the most negative value possible.
9) Repeat steps 6) and 7) until the output value is as low as these
adjustments can make it.
10) Detunetheinstrumentbyturningthe“Resistive”balanceadjust
ment ½ turn CW. This will bring the signal out of the baseline
noise, which could otherwise cause non-linear response at the
low concentration end.
NOTE: Due to minute differences between measuring cells
and the electronics in the bridge circuit found in vari-
ous instruments, some analyzers will have to be bal-
anced at a point higher than 10% of scale while others
can be balanced even closer to electrical zero. The
10% of scale recommended in step 6 of the procedure
is an arbitrary starting point. If the bridge circuit can
be easily balanced at this signal level, the procedure
should be repeated at a point even closer to electrical
zero. Conversely, if balance cannot be accomplished
at 10% of scale, the operator will have to select a
higher recorder set point for the procedure. In any
case, the object is to accomplish dynamic balance
with the lowest magnitude of analyzer cutout signal
attainable with the analyzer at Range #1 sensitivity.
6.3
Correct Operation.
If a stable recording is achieved when the analyzer is operated on zero
gas, erratic performance must be attributed to the customers sampling system
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Thermal Conductivity Analyzer
Model 212R
orincorrectinstrumentinstallation. Thefollowingconditionscanproducean
erratic output from the analyzer:
1) Installationinanareathatissubjecttolargechangesinambient
temperature, direct sunlight, drafts from wind, blowers, or air condi-
tioners. Any of the foregoing conditions will produce a bidirectional
(diurnal)variationinoutputsignal.
2) Sample gas with a moisture content of 10 ppm or greater. Again, the
outputwillvarybi-directionalitywithambienttemperaturechanges.
Ifthesamplegasisknowntohaveafairlyhighmoisturecontenta
dryershouldbeinstalledinthesampleline.
3) Eventhesmallestleakanywhereinthesamplingsystemupstream
from the analyzer, a small leak at a fitting, valve, or regulator, will
cause almost constant variation in analyzer output. The resulting
signaldriftwouldbeerraticandcouldbeeitherbi-directionalor
unidirectional.
4) Acidinthesamplingsystem(solderingfluxes)willproducecontinu-
ous, uncontrollable, unidirectional output signal drift. Sample tubing
that has been treated with descaling chemicals, if subject to above
ambient temperatures, will outgas continuously. Any form of acid in
the sampling system will outgas at high temperatures and attack the
hot wire elements of the cell.
5) Composition materials (diaphragms, tubing, etc.) in the sampling
system will produce erratic, unpredictable changes in output signal
level because of their permeability to gases other than the sample.
The nylon tubing normally used in quick disconnect type sampling
systems will produce diurnal output signal excursions in the order of
10 to 20% of the fine range of analysis.
6.4
IncorrectOperation.
Iftheanalyzerisnotstableonzerogas,andthesupportinggasinstallation
hasbeenmadeandcheckedinaccordancewithsections2and3,thefollowing
proceduresshouldbeemployed.
6.4.1 Analyzer Leak
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Thermal Conductivity Analyzer
Model 212R
Checkaspreviouslystated,theanalyzersentiresamplingsystemhasbeen
checkedunderpressurewithaleakdetector. However,iftheexternalsystem
checksoutandtheinstrumentisdisplayingalargediurnaloruni-directionaldrift,
theinteriorsamplingsystemshouldbecheckedforleaks.Donotopenthe
analyzerinnerdoor. Usethefollowingprocedure:
1)
2)
Acquireasourceofcylinderheliumandthroughadualstage
regulator connect it to a length of 1/8" tubing.
Open the outer door of the analyzer and insert the tubing be-
tween the edge of the sample control panel and the outer case.
CAUTION: Do not insert the tubing along the edges of the
larger swing-down control panel as there is danger of
obstructing the fan or short circuiting the electronics.
The end of the tubing should be shaped into a curve
so that the foam lining is not overly disturbed and the
tubing should only be inserted a couple of inches into
theinterior.
3)
Start the helium flowing. Keep the flowrate low so as not to
disturbthetemperatureequilibriumoftheanalyzerinterior.
4)
Observe the recorder. If any leaks are present in the interior
sampling system, the recorder will be driven off scale in one
direction or the other. NOTE: The analyzer should be on Range
#1 and the zero control adjusted so that the recorder is reading
mid-scale. The direction the recorder indication moves is a
function of the type of zero and reference gas being used (which
varies per application) and which path of the sampling system
(sample or reference) the leak is located in. If the recorder
responds to an atmosphere of helium within the analyzer, all
connections inside the analyzer must be checked.
6.4.2 Temperature Control Check.
Theinteriortemperatureoftheanalyzerisregulatedtoaconstantvalueto
within.002degreescentigrade. Theactualtemperaturecontrolpointvaries
slightlyperapplicationandisafunctionofthecomponentsusedinthepropor-
tionaltemperaturecontrolcircuit.
Iftherecorderisdisplayingalargediurnalrecordingthatisrelatedtothe
timeofdayintermsofthedifferentialbetweendayandnightambienttempera-
ture,troubleinthetemperaturecontrolcircuitryisindicated. Again,thissymp-
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Thermal Conductivity Analyzer
Model 212R
tommustbeevidentwithzerogasflowing. Ifthissymptomisdisplayedonly
whenthesampleisflowing,theproblemisrelatedtoone(ormore)ofthefive
(5)pointsoutlinedinsection7.3.
Tocheckthetemperaturecontrolcircuit,usethefollowingprocedures:
1)
WiththepowerswitchON,openthecontrolpaneldoorand
check to see if the fan is running. If it is not, check the left hand
fuse. This fuse protects the entire temperature control circuit
(see schematic). If the fuse will not hold, a short circuit is
indicated. Disconnecttheprintedcircuitcardandreplacethe
fuse. If the fuse holds (as indicated by the fan running) the
printed circuit card will have to be replaced.
NOTE:Unlesscompetentelectronictechniciansareavailable,TAI
recommendsthatareplacementprintedcircuitcardbeordered
and the existing board returned to the factory for repair. Repair
charges (out of warrantee) will be based on time and material.
A schematic of the proportional temperature control card is
included among the drawings at the rear of the manual.
2)
Ifthefusewillnotholdwiththeboardremoved,a short isindi
cated in the fan, the heater resistors, or the interconnecting
wiring. Withtheboardremoved,checkwiringandcomponents
for short circuits.
3)
Ifthefanisrunning,connectanACvoltmeteracrossanyoneof
the heater resistors on the fan assembly (the meter should be set
to read 50 VAC). In a properly operating circuit, the meter
should read approximately 47 volts (heater control full on) as the
control panel is open and the thermistor should be demanding
maximum heater voltage. If no voltage is present, either the
circuit card or the thermistor probe is faulty. Isolate the problem
byfirstdisconnectingthecircuitboardfromitssocketandwith
anohmmetercheckbetweenterminals5and6ofterminalstrip
TS2. Ifareadingisobtained(disregardactualresistance)the
thermistorisintactandanewcircuitcardwillbenecessary. If
no reading is obtained, a new probe assembly will be required.
4)
Ifapproximately47VACismeasuredacrosstheheaterresis-
tors, a runaway, or correct, circuit is indicated. To determine
which is the case, hold a soldering iron in close proximity (1/2")
totheendofthethermistorprobeandobservethemeter.
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Thermal Conductivity Analyzer
Model 212R
CAUTION: Do not touch the thermistor probe with the iron. The
end of the probe is tied and taped to the sample tubing
below the cell cover. If the meter reading suddenly
drops to zero, remove the soldering iron immediately.
After the area around the thermistor cools, the voltage
across the heater resistors should again climb to 47
volts. Such action indicates a properly functioning
heater circuit. If the meter stays in the 47 volt region,
the circuit card will have to be replaced.
7.0 CALIBRATION DATA FOR MODEL 212R
SERIAL NUMBER: 195929
7.1
Ranges.
Therangesoftheanalyzerare:
RangeSwitchPosition#1:
Range Switch Position #2:
0-50,000 ppm N2 in H2
0-5000 ppm N2 in H2
Range Switch Position #3:
0-500 ppm N2 in H2
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Thermal Conductivity Analyzer
Model 212R
7.2
Output Signal:
Outputcoincideswith100%analysis.
4mA
=
=
=
=
0 ppm N2 in H2
20mA
50,000 ppm N2 in H2 - Range #1
5000 ppm
500 ppm
N2 in H2 - Range #2
N2 in H2 - Range #3
7.3
7.4
Span Setting: 555
Recommended Accessory Gases.
H2 Purity
H2 Purity
ZeroGas
99.999
Reference Gas
SpanGas
99.999
350-450 ppm N2 in H2
7.4.1 Reference Gas.
Withaequivalentimpurityoflessthan3%ofrange1. Theimpurityratio
mustremainconstant.Whenthereferencegassupplyisreplaced,theanalyzer
mustbere-standardized.
7.4.2 Zero Gas.
Becauseofthedifficultiesinvolvedinobtainingagasinpureform,thezero
gasmustbepurchasedfromasupplierwhowillcertifythecylinderastoits
content. Theequivalentimpurityconcentrationofthegasmustbelessthan3%
ofrange1. Whenthezerogasisintroducedforstandardization,therange
switchmustbeinRange1,andthezerocontrolsetsuchthattherecorder
indicatesthezerogasimpurity.
IMPORTANT:Atstartup, besurethatthespancontroldialissettothe
numberrecordedinSection7.3.
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Thermal Conductivity Analyzer
Model 212R
7.4.3 Span Gas.
Containinganequivalentimpurity. Again,thespangasmustbeprocured
fromasupplierwhowillcertifyitscomposition. Therangeswitchmustbein
range3whenthespangasisintroduced.
IMPORTANT: Theaccuracyoftheanalysisisdirectlyrelatedtothe
usersknowledgeofthespangascomposition.
ReferenceandSampleFlowrates 0.3SCFH
Bypass Flowrate 3.0 SCFH
NOTE:
Cylinder and sample stream pressure settings must
be adjusted in order to maintain the above flowrates
when switching from one sample to another.
RECOMMENDED SPARE PARTS LIST
QUANTITY PART NO.
DESCRIPTION
1
1
1
1
A-6251
A-6981
F-45
MeasuringCellBlockAssembly
ProportionalTemperatureControl
SampleFlowmeterTube
F-22
SampleFlowmeterBypassTube
Aminimumchargeappliestoallsparepartorders.
IMPORTANT: Ordersforreplacementpartsshouldincludethepart
number,themodelandserialnumberoftheanalyzerinwhichtheyaretobe
used.
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Thermal Conductivity Analyzer
Model 212R
Ordersshouldbesentto:
TELEDYNE Analytical Instruments
16830ChestnutStreet
City of Industry, CA 91749-1580
Phone (626) 934-1500, Fax (626) 961-2538
TWX (910) 584-1887 TDYANYL COID
Web:
Drawing List
B-73356
D-73212
A-72035
C-73085
C-73088
Outline Diagram
Final Assembly
Piping Diagram
Main PCB Schematic
Power Supply PCB Schematic
Replacement Parts Order Information
A minimum charge of $150.00 is application to all spare parts
orders.
Important:Ordersforreplacementpartsshouldincludetheart
number(ifavailable)andthemodelandserialnumberoftheinstrument
forwhichthepartisintended.
TeledyneAnalyticalInstruments
16830Chestnutstreet
CityofIndustry,Ca91748-1580
Telephone:(626)961-2538
(626) 934-1500
Fax:
(626) 961-2538
(626) 934-1651
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Thermal Conductivity Analyzer
Model 212R
APPENDIX
Specifications:
Ranges: Three decade ranges: Minimum Full scale(ppm)
20ppmHydrogenbalanceArgon
25 ppm Hydrogen balance Nitrogen, Air
100ppm NitrogenbalanceArgon,Helium
100ppmHeliumbalanceAir
150ppmNitrogen,CarbonMonoxidebalanceHydrogen
200ppmOxygenbalanceArgon
Range ID:
3 range ID contacts
Local Range ID LED’S
Detector: Thermal conductivity sensor
Signal Output: 0-1VDC negative ground
4-20maDC Isolated ground
Accuracy:
±2%fullscaleformost binarymixture
atconstanttemperature.±5%ofFull
Scaleoveroperatingtemperature(once
temperatureequilibriumhasbeen achieved)
Operating
Temperature:
20 – 30°C (68° F to 85° F)
Sample
Requirement:
Sample:0.3SCFH
Reference:0.1SCFH
Display:
Mounting:
DigitalLEDreadout(3½Digit)
Flushpanelmount.
Response Time:
90%offullscalelessthen60seconds.
Formostapplication.
Stability:
Lessthen2%fullscaledriftover24
hours
Power
requirement:
110VAC,50/60Hz (220VACoptional)
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