dew point & compressed air - rotronic...• high cost in purge air is reduced • some hdd...

DewPoint&CompressedAir

Helping you make a better measurement.

BruceMcDuffee MichaelBoetzkes

WebinarPresenters&HumidityExperts

Agenda&TakeawaysAgenda• DefinitionofDewPoint• PressureEffect• ISOAirClasses&Dryers• DesiccantDryersandEfficiency• WaterinAir– practicalexample• Summary

Takeaways• Understandingtheparameterhelpstomakeabettermeasurementandpreventwater.

• Learnthecauseofliquidwaterinthesystem.

• Understandhowpressureaffectsthemeasurement.

• Understanddryerperformanceanddewpoint.

DefinitionofDewPointTemperature

• Dewpointtemperatureisthetemperatureatwhichwatervaporwillbegintocondense.

• Thetemperatureatwhichamoistgasissaturatedoveraplanesurfaceofpureliquidwater.

Note– Dewpointtemperaturedoesnotchangeastemperaturechanges.

WhataboutFrostPoint?

• Thetemperatureatwhichamoistgasissaturatedoveraplanesurfaceofpureice.

• Whichoneareyoumeasuring?• Whichonemattersincompressedair?

Note– Dewpointislowerthanfrostpoint (byabout4Cat-40).

WhyIsDewPointTemperaturesoImportant?

• Waterincompressedaircausesproblems.

• IfDp reachesambienttemperature,condensationoccurs.

• Dewpointtemperaturechangeswithpressureandwithdryerperformance.

PressureEffectsonDewPoint

Ruleofthumb:• Aspressureincreases,dewpointtemperaturerisesandapproachessaturation.

• Aspressuredecreases,dewpointtemperaturegoeslowerandtheairbecomesdryer(relativelyspeaking)

PressureDewPointvs AtmosphericDewPoint

• PressureDewPointisthedewpointattheactualpressure.

• AtmosphericDewPointiswhatthatdewpointwouldbeiftheairwereexpandedtoatm pressureor0psig.

• Knowwhatyourhygrometerisreporting– pressureDp orAtm Dp.

Comments&Questions

Ifwedon’tgettoyourquestion today,we’llrespondviaemailafterthewebinar.

WhereShouldyouMeasureDewPoint?

AirClassification- ISO8573.1(pressuredewpointonly)Class Particles

max inmicronsDewPoint C DewPointF Oil

mg/m3

1 0.1 -70 -94 0.012 1 -40 -40 0.13 5 -20 -4 14 15 3 38 55 40 7 45 >56 - 10 50 -

HeatlessDesiccantDryersDewPoint

DewpointDemandSwitching• Heatlessregenerativedryers• Highcostinpurgeairisreduced• SomeHDDconsumeupto15%oftheirratedcapacityinpurgeairwithoutDDS.

For example:• If a dryer is rated for -40 Dp at 1000 cfm, it requires

150cfm just for purge air.• This is equal to a 35HP compressor running 24/7 just to

purge the dryer.

PracticalExamples

1. Dewpoint=38F;airlinegoesoutsidein30F;frozenwater

2. Dewpointinstrumentreads-20FDp;whatistruepressureDp?

3. PressureDp=+38Fat70psig;atmDp =-2F• Increasepressureto150psig;PressureDp=+55F

Comments&Questions

Ifwedon’tgettoyourquestion today,we’llrespondviaemailafterthewebinar.

NextWebinarsProductWebinar– RotronicWirelessDataLoggerTuesday,March22nd1:00PMEDTRegisteratwww.rotronic-usa.com/product-webinars

ProductWebinar– LowDewPointProbeTuesday,April5, 1:00PMEDTRegisteratwww.rotronic-usa.com/product-webinars

Helpingyoumakeabetterhumiditymeasurement– andmore.

Transmitters,portablemetersandloggersfor:

• Humidity• CarbonDioxide• LowDewPoint• WaterActivity• DifferentialPressure• MonitoringsystemsforcGMP• ISO17025calibrations(humidityandtemperature)

Postwebinarsurvey

Thankyou!email:info@rotronic-usa.comUSandSouthAmerica:www.rotronic-usa.comCanada:www.rotronic.caOutsideAmericas:www.rotronic.com

Futurewebinarregistrations:www.rotronic-usa.com/humidity-webinars

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