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Làm thế nào để cải thiện hiệu suất Feeder

Làm thế nào để cải thiện hiệu suất Feeder


Nó iscrucialtounderstandthedifferenttypesandtheadvantages/disadvantagesofscrewtrough,

khuấy, andthescrewitself. Manyloss trong weightfeedersincorporateascrewasthefeeddevice
duetoitswidefeed-rangecapability.
Eachselectedfeeddevicehasarangeofavailablescrewswithdifferentdiametersandpitches.
Eachfeedersupplierprovidesarangeofmodelscapableofprovidingfeedratesoverthespectrum
ofnormalapplications. Thefeeddeviceiscomprisedofseveralcomponents.
Thescrewtroughisacriticalcomponentofascrewfeeder.Itconvergesdimensionallyfromtheinlet,
attachedtotheextensionhopper, andintothescrew. Ittransitionsthemassofdryingredient
containedinthefeederfromthelarger-dimensionextensionhopperintothesmaller-dimensionscrew.
Mostdryingredients (bột, hạt, bột viên, sợi, andflakes) donotflowreliablythrough
convergingtransitions. Thereisfrictionbetweentheparticlesandaninterlockingtendencythat
restrictsorstopstheflow. Whentheflowstopsitiscalleda "cầu."
Alldryingredientshaveaminimumbridgingdimension.Flowstopsandabridgeformsatthis
Cross-sectiondimension. Thereducingcross-sectiondimensionsinthescrewtrougheventually
reachthebridgingdimension. Anagitationdeviceisincorporatedinthescrewtroughinorderto
preventthebridgefromforming.
Flexiblewalled/externalpaddleandinternalstirringaretwocommontypesofagitationdevices.
Thescrewtroughisconstructedofaflexiblematerial, normallypolyurethane, inawedgeshapeon
twosidesandnearverticalontheothertwosides. Movablemetalpaddlescontactthetwo
wedged shapedsidesand "xoa bóp" họ, pushingthesidesinandoutcontinuously.
Thismovementcausesanunstablesupportforthedryingredientparticles.Arestrictionmovement
followedbyavoidmovementcausesanybridgesthatarestartingtoformtocollapse. Gravityacts
ontheparticlestomovethemdownandeventuallyintothescrew.
Comparisonoffeedercomponentsforexternalpaddleagitationandinternalstirringagitation
Thescrewtroughisconstructedofmetal, normallystainlesssteel, andiscurvedinaconstant
radiustoaccommodatetheclosemovementofrotating, agitatingblades. Theagitatorblades
movethroughthedryparticlesoneachsideofthescrew, whichispositioneddirectlybelowthe
agitatorblades. Movementisdownintothescrewononesideofthescrewtroughanduponthe
Otherside. Thisblademovementpreventsbridginginthescrewtrough.
Theshapeofthescrewtroughiscritical.Aloss trong weightfeeder'smainpurposeistofeedthe
ingredientaccuratelyatthedesiredsetpoint. Theweight-feedbackcontrolrequiresthateachscrew
flightbefilledwiththesameweightofingredient. Lặp lại weightfillingofeachscrewflightis
achievedbyaproperlydesignedagitationdevice (linh hoạt-walledwithexternal-paddlemassage
orwithinternalstirring).
Ngoài ra, theremustbesufficientscrewflightsexposedopenlyinthebottomofthescrewtrough
sothatcompleteandrepeatablefillingoccursbeforetheingredientisenclosedinthescrewtube.
Thebestscrew-troughshapeisawedge, ratherthanasphericalorconicalshapeatthebottom
ofthescrewtrough, inordertoexposetherequiredlengthofscrewtofillproperly.
Theflexible-tường/bên ngoài-chèo thuyền-massagedscrewtrough, availablefromseveralsuppliers,
hasdrawnmoreinterest. Oneimportantreasonforthisisthatthemovementoftheflexing
screwtroughdirectlycontactsandmassagestheingredientinthescrewtroughonboth
sidesofthewedgesurfaces, fromthetopinlettothetopofthescrew.
Sincethestirringagitatorhasacircularmotion, therearetwodeadzones (noagitation) tại
thetopofthescrewtrough. Thescrewtroughissizedtoreducethevolumeofthedeadzone.
Asaresult, theflexible-tường/bên ngoài-chèo thuyền-massagedscrewtroughtypicallyhasalarger
volumeandinletdimensionthantheinternal-stirringscrewtrough. Sincetheextension
hopperismounteddirectlyabovethescrewtrough, thebottomdimensionoftheextension
hopperistypicallythesameastheinlettothescrewtrough.
Giảm cân-trong-weightfeederextensionhoppersarecommonlysized (ruleofthumb) để
contain4minutesofstorageatthemaximumfeedrate/minimumbulkdensityoftheingredient.
Theextensionhopperoftencanbesuppliedwithverticalsides, whichprovidesfloorspace
advantagesoverconicalextensionhoppers. Ngoài ra, thereisnorequirementforadditional
stirringagitationintheextensionhopper,sincethesidesarevertical(noconverging).
Nói chung, ascrewfeeddevicewithflexible-tường/bên ngoài-chèo thuyền-massagedscrewtrough
isafirstchoiceforloss trong weightfeeders. Tuy nhiên, therearesituationswherethestirringagitator là
yêu cầu: cohesiveingredientsandingredienttemperature. Cohesiveingredientsformasolid
masswhenexposedtocompression. Somearesosensitivethattheforceofgravityactingontheir
ownheadmasscancausethemtosolidify. Theseingredientsaredifficult, sometimesimpossible, để
feedreliablywithoutexcessivemaintenance. Testingishighlyrecommendedatfeedermanufacturers,
whoofferseveraltypesoffeeddevices. Stirringagitatorsmayhavethebestchanceofsuccessinsuch
trường hợp. Polyurethanebecomestoosoftatingredienttemperaturesabove50C (122F), yêu cầu
ametalscrewtrough.
Thescrewisthecomponentofthefeederthatprovidesthefeeding.Theagitationonlyensuresthat
thescrewflightsfilluniformly. Screwsareselectedtoachievemaximumandminimumfeedrates.
Thescrewdiameterandpitcharesizedtoachievethefeedrateatanoptimalscrewrotationalspeed.
Attoolowascrewspeedthe "pulsingflow" maycauseanundesiredvariationinthefinalproduct.
Toohighascrewspeedmaycauseincompletefillingofthescrew.
Therearethreecommonscrewtypes:spiralscrew, bladescrewandtwinconcavescrew.
Thesingle-spiralscrewisthemostcommonselection.Itis "mở" fortheingredienttoflow
freelyintotheflightsofthescrew. Ithasasmallersurfaceareathathelpsreduceadhesionof
theingredient, whichchangesthescrewvolumetricgeometry. Ingredientsaretransferredwith
lowshear. Onthenegativeside, aeratedingredientscaneasilyfloodpastthescrewflights.
Thesingle-bladescrewoffersmoreresistancetoaeratedingredients, butbecause
thereismoresurfacearea, stickyingredientscanadhere, reducingthevolumetricgeometry.
Bladescrewsareoftenpreferredforheavypowderswithbulkdensitiesofmorethan80lb/ft3.
Twinconcavescrewscanprovidesuperiorperformanceforpoorlyflowingpowders.Twinconcave
screwsareco-Luân, intermeshing, andself xoá sạch. Thepowderflowsaroundtheflightsof
bothscrews. Lau Thenegativeeffectsofsomeadhesivepowdersarereducedbytheself
ofthetwoscrews. Twinconcavescrewsaresolidandthescrewflightshavealowvolumecompared
withspiralandbladescrews. Theshearonthepowderishigh, particularlyinthescrewtube.
Thescrewtubeistypicallyshorttoreducenegativeeffectsofhighshear.
Twinconcavescrewsareideallysuitedtopowderswithfeedratesbelow5ft³/hr. Thecross-phần
ofthetwoscrewsiswiderthananequivalentsinglescrew, reducingthetendencytobridgeinthe
transitionfromthescrewtroughintothescrew. Ngoài ra, screwspeedsfortwinconcavescrewscanbe
higherthansinglescrewsforthesamefeedratebecauseofthelargerinletandlowvolumeofthe
screwflight. Higherscrewspeedsreducethenegativeeffectsofpulsation.