Introduction
Duetotheusecharacteristicsofpressurevesselsandthechemicalprocesscharacteristicsoftheinternalmedium,itisoftennecessarytosetupsomesafetydevicesandmeasuringandcontrolinstrumentsonthevesseltomonitortheparametersoftheworkingmedium.Inordertoensurethesafetyoftheuseofpressurevesselsandthenormalprogressoftheprocess.
Safetyaccessoryisasafetydeviceinstalledonequipmentforthesafeoperationofpressurevessels.Includingsafetyvalves,burstingdiscdevices,emergencyshut-offdevices,pressuregauges,liquidlevelgauges,temperaturemeasuringinstruments,fusibleplugs,etc.
Classification
1.Thesafetyaccessoriesofpressurevesselsareclassifiedaccordingtotheirperformanceorpurpose.Theycanincludethefollowingfourtypes:
1.Pressurereliefdevice:Adevicethatcanautomaticallydischargethepressurewhenthepressurevesselisoverpressure.Suchas:safetyvalves,rupturediscsandfusibleplugs,etc.
2.Meteringdevice:referstoanappliancethatcanautomaticallydisplayprocessparametersrelatedtosafetyduringcontaineroperation.Suchas:pressuregauge,thermometer,liquidlevelgauge,etc.
3.Alarmdevice:Referstotheinstrumentthatcanautomaticallyemitsoundorotherobviousalarmsignalswhenthecontainerisinadangerousstateduetounsafefactorsintheoperation.Suchas:pressurealarm,temperaturedetector.
4.Interlockingdevice:Itisacontrolmechanismsetuptopreventoperationerrors.Suchas:interlockswitch,linkagevalve,etc.
Second,amongthesafetyaccessoriesofpressurevessels,themostcommonlyusedandmostcriticalaresafetyreliefdevices,pressuregauges,etc.
1.Safetyvalve:Itscharacteristicisthatwhenthepressurevesselisundernormalworkingpressure,itiskepttightandleak-proof.Oncethepressureinthevesselexceedstheregulation,itcanautomaticallyandquicklydrainthemediuminthevesseltomakethevesselThepressureisalwayskeptwithinthehighestallowablerange.Safetyvalvescanbedividedintospring-typesafetyvalves,lever-typesafetyvalves,andpulse-typesafetyvalves.Undernormalcircumstances,thesafetyvalveshouldbeinstalledonthecontainerbodyasmuchaspossible,theliquefiedgasshouldbeinstalledinthegasphase,andthesafetyofdischargeshouldbeconsidered.
2.Burstingdisc:alsoknownasexplosion-proofmembrane,itisafracturedsafetydevicewithgoodsealingperformanceandquickresponsetopressurerelief.Generallyusedinhigh-pressure,non-toxicgascylinders,suchasair,nitrogen.Theburstingdiscpressureonthegascylinderisgenerallylargerthanthefillingpressureofthegascylinderandlessthanthedesignmaximumtemperaturerisepressureofthegascylinder.
3.Fusibleplug:itusesthelowmeltingpointalloyinthedevicetomeltatahighertemperatureandopensthechanneltodischargethegasfromtheholeoftheoriginallyfilledfusiblealloytoreleasethepressureItischaracterizedbysimplestructure,easyreplacement,andeasycontroloftheactionpressuredeterminedbythemeltingtemperature.Itisgenerallyusedforcontainerswherethegaspressureisnothighandiscompletelydeterminedbythetemperature.Forexample,themeltingtemperatureofthefusibleplugonthelow-pressureliquefiedgaschlorinecylinderis65°C.
Comparedwiththesethreesafetydevices,thesafetyvalvecanbeclosedafteritisopenedtodischargeexcessivepressure.Thecontaineranddevicecancontinuetobeused,buttherupturediscandfusibleplugcannotbeusedafterthedischargeofexcessivepressure.Andthedevicehastostoprunning.Whenselectingsafetyvalvesandfusibleplugs,thesafetydischargevolumeshouldbeconsidered,andtherupturediscshouldconsiderthecalculationofthedischargeareaandthickness.
4.Pressuregauge:Itisaninstrumentusedtomeasurethepressureofthemediumonapressurevessel.Typescanbedividedinto:
Springpressuregauge,suitableforpressurevesselswithgeneralmedia.
Diaphragmpressuregauge,suitableforpressurevesselswithcorrosivemedia.