Manufacturer’s Reprint Area Monitor Applications In The ... Library/gas... · damage. Hydrogen...
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CARBON MONOXIDE Coal fines and dust are extremely flammable. “CO monitoring for the presence of Carbon Monoxide is the way to find out soonest whether there is a fire in the making. CO is an odorless, toxic gas that is liberated at the very early stages of incomplete combustion 1 .” Coal Bunker, Silo and Hopper CO levels are often monitored for fire detection purposes using sample draw or in-situ monitoring. Manned Coal handling areas, including tunnels and conveyor rooms, should be monitored for fire detection and worker protection from CO exposure. The OSHA PEL for CO is 50 PPM 2 . Methane and Oxygen deficiency sensors may also be required in these areas. The widespread adoption of Powder River Basin Coal (PRB) has exacerbated fire problems due to its remarkable ease of spontaneous combustion. Some plants inert coal storage vessels with flue gas or CO 2 to prevent fires. This presents an Oxygen depletion hazard in adjoining areas, and should be considered when planning a monitoring strategy. Platforms, walkways and areas around the Boiler are often monitored for CO and Oxygen Deficiency and sometimes H 2 S when high Sulfur coal is being burned. CHLORINE Chlorine, other disinfectants and chemical agents are often used in cooling water to control organic growth and scaling. Chlorine, Chlorine Dioxide and Ammonia are hazardous to employees. Chemical feed and coolant mechanical equipment areas should have dedicated gas monitors for leak detection and annunciation. HYDROGEN Utility Electricity Generators have a pressurized direct or indirect Hydrogen cooling system. Hydrogen conducts heat 7 times better than air and its low density (0.07 versus air of 1.0) minimizes windage losses, making it an ideal coolant. Hydrogen has a flammability range 4% to 74% by volume 2 and detonates (explodes) from 18% to 59% by volume. It is very easily ignited and burns with a pale blue, nearly invisible flame. H 2 can cause serious injury to personnel, as well as severe equipment damage. Hydrogen leaks typically occur at the generator bearing and shaft seals, in the seal oil supply system, H 2 and CO 2 cabinets, valves, fittings and regulators associated with the Hydrogen and CO 2 purging systems. Hydrogen specific gas sensors should be used for leak detection to avoid interference from Methane. Most plants have a battery room which is used for back-up power to critical systems during a power outage. Batteries in discharge produce considerable Hydrogen. It is advisable to monitor for explosive levels of Hydrogen and trigger ventilation when detected. 24 VDC gas detection and ventilation should be employed so that power is available during an outage. HYDROGEN SULFIDE Percent Sulfur levels in Coal can produce hazardous concentrations of Hydrogen Sulfide in areas near the boiler due to casing and flue work leaks. Flue gas clean-up measures such as scrubbers and bag-houses may also produce significant ambient H 2 S. These areas should be evaluated to determine if monitoring is required for personnel safety. H 2 S exposure can stop involuntary breathing, requiring immediate attention. Consult ACGIH 3 or OSHA 2 for acceptable exposure levels. METHANE Methane is the major component of Natural Gas and is much of the gas volatiles in Coal. Natural Gas fired plants typically monitor Methane at the custody transfer and pressure reduction points, above the burners, and on platforms and areas near potential casing leaks in the boiler. Some areas of a coal-fired plant, such as coal tunnels, may require Methane and Oxygen deficiency monitoring. A review of the coal “as received” analysis and tunnel air-change rate will reveal the monitoring requirements. OXYGEN CO 2 is heavier than air and collects in low areas presenting a substantial safety hazard to workers. In locations where Flue gas or CO 2 are used for inerting coal storage vessels, Oxygen deficiency monitors are required. The alarms specified by OSHA are 19.5% and 18% by volume when two alarms are employed. Instrument shelters and other enclosed areas with potential for Oxygen deficiency should have interior monitoring with internal and external indication and annunciation of the hazard. Remote or control room notification is required for all hazard alarms. Note: Personal monitors are not appropriate for this application because they do not sense the hazard until after entry into the shelter. Oxygen monitoring of inerted coal pulverizers and conveying pipes is also practiced. In this case, low Oxygen is desirable in order to prevent combustion or explosion of the pulverize coal. A WORD ABOUT PORTABLE AND PERSONAL GAS MONITORS The advent of miniaturized electronics and gas sensors has resulted in the widespread adoption of portable or personal gas detection. However, the user should be aware that personal monitors must be functionally verified prior to each use! Verification includes confirming a charged battery, proving response to the target gases and verification of alarm operation. In high hazard locations, workers should work in pairs and carry a means of communication. For higher traffic or continuously manned areas, personal monitors may not be the most cost-effective, reliable or accountable solution. SENSIDYNE FM APPROVED SENSALERT SMART GAS SENSORS Sensidyne SensAlert PLUS Smart Gas Sensors bring exceptional performance and reliability to area monitoring. SensAlert PLUS sensors store all operating parameters in non- volatile memory for auto-recognition and set-up by the gas transmitter. They can be shop calibrated and are approved for hot-swapping in the plant, even in a hazardous classified areas. Cumulative exposure, TWA alarms, Predictive Sensor Failure, Intrinsically Safe Sensor Heads, and Sensor Test-On-Demand functions deliver the highest system integrity and accountability for the most demanding applications. Area Monitor Applications In The Power Industry 1 Power Magazine, October 2003, “Fire-protection guidelines for handling and storing PRB coal,” Edward B. Douberly, Utility FPE Group Inc. 2 29 CFR 1910.1000, Table Z1; PEL (Permissible Exposure Limit) is expressed as an 8 hour TWA (Time Weighted Average) 3 American Council of Governmental Industrial Hygienists, 1330 Kemper Meadow Drive, Cincinnati, OH 45240; www.acgih.org Hydrogen-cooled Generator, Courtesy of Siemens Manufacturer’s Reprint
Transcript of Manufacturer’s Reprint Area Monitor Applications In The ... Library/gas... · damage. Hydrogen...
CARBON MONOXIDE Coalfinesanddustareextremelyflammable.“COmonitoringforthepresenceofCarbonMonoxideisthewaytofindoutsoonestwhetherthereisafireinthemaking.COisanodorless,toxicgasthatisliberatedattheveryearlystagesofincompletecombustion1.”CoalBunker,SiloandHopperCOlevelsareoftenmonitoredforfiredetectionpurposesusingsampledraworin-situmonitoring.MannedCoalhandlingareas,includingtunnelsandconveyorrooms,shouldbemonitoredforfiredetectionandworkerprotectionfromCOexposure.TheOSHAPELforCOis50PPM2.MethaneandOxygendeficiencysensorsmayalsoberequiredintheseareas. ThewidespreadadoptionofPowderRiverBasinCoal(PRB)hasexacerbatedfireproblemsduetoitsremarkableeaseofspontaneouscombustion.SomeplantsinertcoalstoragevesselswithfluegasorCO2 topreventfires.ThispresentsanOxygendepletionhazardinadjoiningareas,andshouldbeconsideredwhenplanningamonitoringstrategy. Platforms,walkwaysandareasaroundtheBoilerareoftenmonitoredforCOandOxygenDeficiencyandsometimesH2SwhenhighSulfurcoalisbeingburned.CHLORINE Chlorine,otherdisinfectantsandchemicalagentsareoftenusedincoolingwatertocontrolorganicgrowthandscaling.Chlorine,ChlorineDioxideandAmmoniaarehazardoustoemployees.Chemicalfeedandcoolantmechanicalequipmentareasshouldhavededicatedgasmonitorsforleakdetectionandannunciation.HYDROGEN UtilityElectricityGeneratorshaveapressurizeddirectorindirectHydrogencoolingsystem.Hydrogenconductsheat7timesbetterthanairanditslowdensity(0.07versusairof1.0)minimizeswindagelosses,makingitanidealcoolant. Hydrogenhasaflammabilityrange4%to74%byvolume2anddetonates(explodes)from18%to59%byvolume.Itisveryeasilyignitedandburnswithapaleblue,nearlyinvisibleflame.H2cancauseseriousinjurytopersonnel,aswellassevereequipmentdamage.Hydrogenleakstypicallyoccuratthegeneratorbearingandshaftseals,inthesealoilsupplysystem,H2andCO2cabinets,valves,
fittingsandregulatorsassociatedwiththeHydrogenandCO2purgingsystems.HydrogenspecificgassensorsshouldbeusedforleakdetectiontoavoidinterferencefromMethane. Mostplantshaveabatteryroomwhichisusedforback-uppowertocriticalsystemsduringapoweroutage.BatteriesindischargeproduceconsiderableHydrogen.ItisadvisabletomonitorforexplosivelevelsofHydrogenandtriggerventilationwhendetected.24VDCgasdetectionandventilationshouldbeemployedsothatpowerisavailableduringanoutage.
HYDROGEN SULFIDE PercentSulfurlevelsinCoalcanproducehazardousconcentrationsofHydrogenSulfideinareasneartheboilerduetocasingandflueworkleaks.Fluegasclean-upmeasuressuchasscrubbersandbag-housesmayalsoproducesignificantambientH2S.Theseareasshouldbeevaluatedtodetermineifmonitoringisrequiredforpersonnelsafety.H2Sexposurecanstopinvoluntarybreathing,requiringimmediateattention.ConsultACGIH3orOSHA2 foracceptableexposurelevels.METHANE MethaneisthemajorcomponentofNaturalGasandismuchofthegasvolatilesinCoal.NaturalGasfiredplantstypicallymonitorMethaneatthecustodytransferandpressurereductionpoints,abovetheburners,andonplatformsandareasnearpotentialcasingleaksintheboiler. Someareasofacoal-firedplant,suchascoaltunnels,mayrequireMethaneandOxygendeficiencymonitoring.Areviewofthecoal“asreceived”analysisandtunnelair-changeratewillrevealthemonitoringrequirements.OXYGEN CO2isheavierthanairandcollectsinlowareaspresentingasubstantialsafetyhazardtoworkers.InlocationswhereFluegasorCO2 areusedforinertingcoalstoragevessels,Oxygendeficiencymonitorsarerequired.ThealarmsspecifiedbyOSHAare19.5%and18%byvolumewhentwoalarmsareemployed.
InstrumentsheltersandotherenclosedareaswithpotentialforOxygendeficiencyshouldhaveinteriormonitoringwithinternalandexternalindicationandannunciationofthehazard.Remoteorcontrolroomnotificationisrequiredforallhazardalarms.Note: Personal monitors are not appropriate for this application because they do not sense the hazard until after entry into the shelter. Oxygenmonitoringofinertedcoalpulverizersandconveyingpipesisalsopracticed.Inthiscase,lowOxygenisdesirableinordertopreventcombustionorexplosionofthepulverizecoal.A WORD ABOUT PORTABLE AND PERSONAL GAS MONITORS Theadventofminiaturizedelectronicsandgassensorshasresultedinthewidespreadadoptionofportableorpersonalgasdetection.However,theusershouldbeawarethatpersonalmonitorsmustbefunctionallyverifiedpriortoeachuse!Verificationincludesconfirmingachargedbattery,provingresponsetothetargetgasesandverificationofalarmoperation.Inhighhazardlocations,workersshouldworkinpairsandcarryameansofcommunication.Forhighertrafficorcontinuouslymannedareas,personalmonitorsmaynotbethemostcost-effective,reliableoraccountablesolution.SENSIDYNE FM APPROVED SENSALERT SMART GAS SENSORS SensidyneSensAlertPLUSSmartGasSensorsbringexceptionalperformanceandreliabilitytoareamonitoring.SensAlertPLUS sensorsstorealloperatingparametersinnon-volatilememoryforauto-recognitionandset-upbythegastransmitter.Theycanbeshopcalibratedandareapprovedforhot-swappingintheplant,eveninahazardousclassifiedareas.Cumulativeexposure,TWAalarms,PredictiveSensorFailure,IntrinsicallySafeSensorHeads,andSensorTest-On-Demandfunctionsdeliverthehighestsystemintegrityandaccountabilityforthemostdemandingapplications.
Area Monitor Applications In The Power Industry
1 PowerMagazine,October2003,“Fire-protectionguidelinesforhandlingandstoringPRBcoal,”EdwardB.Douberly,UtilityFPEGroupInc.
2 29CFR1910.1000,TableZ1;PEL(PermissibleExposureLimit)isexpressedasan8hourTWA(TimeWeightedAverage)
3 AmericanCouncilofGovernmentalIndustrialHygienists,1330KemperMeadowDrive,Cincinnati,OH45240;www.acgih.org
Hydrogen-cooled Generator, Courtesy of Siemens
Manufacturer’s Reprint
Pumped Sample-Draw, FlowSwitch&Filter
Division 2 Sensor Mounting Options
RemoteSensor (HighorLow)
Standard Transmitter-Sensor
Assembly
2 or 3-Wire 4-20 mA Available
Description Product No.SensAlertPlus Transmitters 2-Wire GP ...................................820-0201-013-Wire GP ...................................820-0202-01 3-Wire GP, with I.S. Barrier ...........820-0202-043-Wire GP for use w/ relay card2 ...820-0202-032-Wire HD, Div2 ...........................820-0203-01 3-Wire HD, with I.S. Barrier ...........820-0204-04 3-Wire HD, Div2 Standard Dome ..820-0204-013-Wire HD, Div2 Large Dome2 .......820-0204-022-Wire XP, Div1 ...........................820-0205-013-Wire XP, Div1 Standard Dome ...820-0206-013-Wire XP, Div1 Large Dome2 ........820-0206-02
SensAlertPlus Sensors
H2 1000 ppm ................................823-0210-21 CO 500 ppm .................................823-0219-22
O2 Ambient ...................................823-0240-21
SensAlertPlus AccessoriesRelay Card ....................................700-0046-01Moisture Barrier Assembly ............821-0201-01Calibration Cup ............................821-0202-01Rainshield ....................................821-0203-01Remote Sensor Kit for Div. 1 ..........821-0207-02Remote Sensor Kit for Div. 2 ..........821-0207-01Duct Mount Kit .............................821-0209-02Mounting Kit ................................821-0213-01
PPM HYDROGEN INTERFERENT TABLE Gas Exposure Response
CarbonMonoxide 5ppm +1ppm Chlorine 1ppm NoneEthylene 1.3 ppm +1ppm Hydrogen Chloride 5ppm NoneHydrogenCyanide 3 ppm +1ppm NitricOxide 4ppm +1ppm Nitrogen Dioxide 5ppm None SulfurDioxide 5ppm None
CO SENSOR INTERFERENT TABLEGas Exposure Response
Chlorine 1ppm None Ethylene 1.3 ppm +1ppm Hydrogen 1.7ppm +1ppm Hydrogen Chloride 5ppm None HydrogenCyanide 5ppm +1ppm HydrogenSulfide 50ppm +1 ppmNitricOxide 5ppm +1ppm Nitrogen Dioxide 5ppm -1ppm SulfurDioxide 5ppm None
AMMONIA INTERFERENT TABLE Gas Exposure Response
Alcohols 1000ppm NoneCarbon Dioxide 5000ppm NoneCarbonMonoxide 100ppm NoneHydrocarbons % Range None Hydrogen 10,000ppm NoneHydrogenSulfide 10ppm +1 ppm
Area Monitor Installation Suggestions
INTEGRATION STRATEGY IntegratingaProcessandPersonnelprotectiongasdetectionsystemrequiresthatthenotificationandcontrolproceduresmandatedbyCodeandLawbefollowed,includingInsuranceCompanymandates. CompliancewiththeseissuesissimplifiedbyusingaSensidyneControllertoprocessthegassensorinputs,provideannunciationandsupervisorycontrol.A4-ChannelSystemisillustratedbelow.Upto16gassensorsmaybeaccommodatedbyoneController.
GAS SENSOR MOUNTING CONFIGURATIONS Gassensorsarelocatedinthebreathingzone(4to6feetabovefloor)forgasessimilarindensitytoair,includingOxygendeficiency.Forlighterthanairgases,(Methane,AmmoniaorHydrogen),thesensorsmustbepositioned
within12inchesoftheceilingorhighestpointofanenclosedarea.HeavierthanairgaseslikesolventvaporsorHalocarbonrefrigerantsshouldhavethesensorsplacedwithin12inchesofthefloororlowestpointintheenclosedarea.Targetgasdensityandpotentialleaksourcesshouldalwaysbeidentifiedwhenconfiguringagasdetectionsystem. Gassensorsareoftenmountedremotelyfromthetransmitter,whichisnormallykeptateyelevel.Thesesituationsariseduetogasdensityvariationsordifficultaccesslocations.Tubingisruntoacalibrationadapteronthesensorassembly,sothatroutinecalibrationscanbeperformedfromthetransmitter.Otherconfigurationsincludeductmounting,anddrawingasamplefromaremoteorinaccessiblelocation.Thelatterhasaflowswitchtoindicatesamplesystemintegrity,asrequiredbyCode. Carefulattentiontogassensorplacement,supervisorycontrolfunctionsandemergencyresponseplanningwillproduceafunctional,accountableandlowmaintenanceareamonitoringsystemwhichcomplieswithlocalcodesandlaws.
