pull testing vs gauss testing - powder … food processing pull testing vs gauss testing ......

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www.powder‐solutions.com

GUIDEFORMAGNETSELECTION&VALIDATION

inFOODPROCESSING

PULLTESTINGvsGAUSSTESTING

October2016PreparedbyActiveMagneticsResearchPtyLtd.

ConsultingReference‐HACCPInternationalandFoodSafetyStandardMAGSEP1‐2010

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Introduction:Thefollowingreview,writtenbyWilliamJBaker,SeniorConsultantofActiveMagneticsResearch,isprovidedforthebenefitofqualityobjectivesofglobalfoodindustryin2016.Fundamentaltothispaperistheassertionthatneitherhighestpulltestorhighestgausstestmeasurementsaloneprovethesemagnetswillprovidethebestperformanceinreal‐lifemagnetinstallations.

Review:Neodymiummagnetshaveenabledtheredesignofgrateandbarmagnetstosuitmodernsafefoodprocessing,wheretheemphasisformagnetshasshiftedfrompreventionofequipmentdamageanddowntimecausedbytrampiron,tofoodsafetyandproductpurity.In2016foodindustrypractice,wemustefficientlyextract<1/8”fragmentsofweaklymagneticSSchips,scrapingsandmetaldustfrombecomingspecsofunwantedcontaminationinfinaloutgoingproductsorpassedtotheconsumerinfinishedproduct.Obviously,peakperformancemagnetsareessentialfordaytodaycontinuingprotection.Asanaddedbenefit,effectivemagnetswillreduceproductwastageandsavetimesearchingforcausesofmetaldetectorrejections.

Notonlymustwepreventmachinerydamageandproductiondowntime,butpreventbrandnamedamageandcostlyproductrecallsfrommetalcontaminations.Wemustextractwhatmetaldetectorsand/orx‐rayequipmentmaymiss.Peakperformingmagnetswillreducefalserejectsfrommetaldetectorsandx‐rayequipment,andallowthemtoperformattheirbestsensitivity.Youmayask…..1) HowdoIreallyknowifmymagnetsarepeakperformers?2) HowdoIknowthatoriginalpeakperformingmagnetshavenotlosteffectivestrengthsince

beingnew?Itistheobjectiveofthispapertoclarifythesecriticalissues.Thesearethevitalquestionsdemandingaccurateanswerstosatisfythoseresponsibleforriskreduction,maintenanceofcompanyqualityandbrandimage;anddiscriminatingengineersresponsibleforselectionandmaintenanceofeffectiveprocessequipment.

Question1/HowdoIreallyknowifmymagnetsarepeakperformers?Ifthemagnetisthefinalmagnetpriortopackaging,verifyitconformstoHACCPInternationalFoodSafetyStandard0909MAGSEP1‐2010‐atleastintermsofgaussstrengthandpolecentres.

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Whatconstitutes‘MagnetPerformance’infoodmillingandrelatedfoodindustriesoperatingunderaHACCPorsimilarriskandhazardcontrolprocess?

“Itistheabilityofmagnettoextractthehighestpercentageofweaklymagneticandtypicalmagneticcontaminationfoundinfoodstreamspriortooutgoingproduct”.

Additionally;BesidesSTRENGTH(pulltestorgausstest)andPOLECENTRES(distancebetweenhighstrengthpolebands)thereareotherfactorstoconsiderwhichareveryimportantwhenevaluatinglongtermoptimumperformingmagnetinstallations,whenfoodsafetyandproductpurityiscritical.

Whatarethemeasuresofthisperformanceinorderofimportance?1) Most10,000gausscollectionpoles(22mmcentresorless)inagivenbarlength.2) Longestlinearlengthofcollectionpolespergivenbarlength.3) Locationtoavoiddownstreamre‐contamination(nearesttopacking).4) Sizingtomagneticallycovertheproductstreamwithoutblockage.5) Bestmagnetstrengthretentionmeasures,asconfirmedbycertifiedmagnetvalidationsto

detectdeclinefromoriginalstrength.6)Themagnetshapewillefficientlyretainmagneticsextracted.7) Easiestdesigntoregularlycleanoffcollectedfragmentstomaintainseparating efficiencyofacleanmagnet.Furtherrecommendationsforassuringoverallmagneticseparationefficiency:

Considerinstallingadditional10,000gaussmagnetsofattheearliestintakepositionstoconfirmingredientsarefreeofmagnetics

Bestpracticeshouldincludemagnetstoremovebulkofmagneticssuchasstainlesssteel&ferroustramp,rustandmagneticstonetoavoidmachinerydamageandgrindingoflargermagneticstofineweaklymagneticparticles.

Intermediatemagnetshelptoavoidoverloadingoffinalmagnetsparticularlywherethepackingmagnetissmalldimensionally.

ExposingaMAGNETICSEPARATIONMYTH:Reviewingsomerecentmagnetmanufacturerstestsandclaims,itseemsthatpulltestresultsareoftenpresentedinawaytoencouragetheconclusionthatmagnetbarsshowingthehighest“pulltest”averagearethereforethehighestperformers.Thisisdefinitelynotthecaseinsensitivefoodmagnetapplications.

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Whileblindtestingandgoodtestingmethodologymaybeused,the“objective”and“conclusions”ofthesetestsneedtobeclarified.Higherpulltestreadingsareeasilyengineered,butseparationperformancedoesnotnecessarilyequatewithhighestpulltestreadings!Pleasereferdiagram‘A’below.Diagram“A”

Explanation:Bywideningtheinnermildsteelpoleplatebetween2magnetsinrepulsion,wecaneasilyelevatethepullteststrength,butthisreducesthegaussfluxdensity.Thetrickisthatpolecentresarethenwidenedinordertoachievespecifiedgauss.ThisresultsinthehigherpulltesttubebeinglessefficientasdepictedinmoredetailinDiagram‘B’below.TheinnermildsteelpoleplateiswiderinMagnet#1,thereforemorelinesofforcepassthroughthe¼”diametermildsteelballresultinginthehigherpulltestreading.Thismagnetwillholdtightertolargeandmediumtrampiron>than¼”ballsize.ThismagnetcircuitdoesnotconformtotheMAGSEPstandardforfinalmagnets,butcouldbeselectedformachinerydamagepreventionapplications.Inordertomaintainspecifiedfluxdensity(gauss)readings,noticeinMagnet#1thatpolecentresofhighestpulltestmagnetsarewiderapart!Thisistoutilisetheextraenergyofalongerinnermagnet‐verysignificantwhenitcomestoselectingthebestperformerforriskreductionandproductfreeof<1/8”fragmentsandfineweaklymagneticcontamination,whichisourmainobjectiveinsensitivefoodrelatedindustries.PleasereferDiagram‘B’below.

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Diagram“B”

Explanation:Magnet#2hassimilargaussasMagnet#1,however,itisamoreefficientontypicalmagneticcontaminants,astherearemorehighstrengthpolebandsandlessdeadareasaroundthecentrelinebetweenpolebands.Assumingpulltestandgaussstrengthisidenticalamagnetbarwith25mmpolecentreswillbelessefficientonfineweaklymagneticcontaminationsand30mmpolecentresevenlessefficient.TheInternationalStandardforFinalMagnets0909MAGSEP1‐2010recognises10,000gauss@22mmpolespacing’sasmaximumpermittedpolecentresforfinalmagnetsinafoodprocessingoperationoperatingunderaHACCPriskcontrolprogram.Thisisimportantsofineandweaklymagneticparticlescanattractandholdtothehighstrengthpolebandsduringtheirmillisecond

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passagearoundthemagnettubeorbar.Ifpolecentresarewidermanysuchfragmentsaredeflected,butmayescapebeforebeingretained,astheDiagram“B”shows.

Conclusion1:Themagnetwiththehighestpulltestwillhold¼”andlargerferrouspiecestothemagnetbarwithmarginallymoreforceandmaybeselectedwherethemagnetisnota“finalmagnet”orwheretheprimeimportanceistoextractsmalltomediumtrampironforpreventionofequipmentdamage.

Conclusion2:Highestgaussattheshortestdistancebetweenpolecentersshouldbeselectedasthebestperformerwheretheprimarydutyistoextract<1/8”fragments,fineandweaklymagneticcontaminations.TheintendeddutyanddesiredresultsofthemagnetMUSTbeconsideredwhenselectingordesigningthebestperformingmagnetforthejobandnot“pulltest“or“gaussreading”testresultsalone.Theengineerselectingmagneticseparatorsshouldaskthequestion,“Whatarethecentredistancesbetweenthehighstrengthpolebandsalongthebar?”Caution:10%moreinpulltestvaluewithlongerpolecentresmaymean20‐30%lessseparatingefficiency–specifyamaximumof22mmpolecentresforfinalandothercriticalmagnetsmagnets.

Conclusion3:Gausstests,insteadof,orinadditiontopulltestsarerelatedtopotentialperformanceofmagnetinstallations.Thegausstestismorequantitative,gauss/teslabeinganSIderivedunit.Pulltestinouncescanvarytoshowelevatedreadingsifthewidthofpoleplatesisvaried.Acalibratedgaussmeteristhemoreoverallreliableindicatorofpotentialmagneticseparationperformance.

Conclusion4:Sincebotharereliablecomparativeinstruments,digitalcalibratedpulltestersordigitalcalibratedgaussmetersareequallysuitablefordetectingandtrendingmagnetstrengthlossovertimeonmagnetsoriginallydeterminedtohavegaussreadingsandpolespacing’sconformingtotheMAGSEPStandard.

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Question2/HowdoIknowthatoriginalpeakperformingmagnetshavenotlosteffectivestrength?Sinceintroductionofthenewcalibratedinstrumentation,calibrateddigitalpulltestersorgaussmetersarebothanaccuratemeansofmeasuringandtrendingDECLINEinmagneticstrengthfromnewmagnetratingscomparingthesamemagnet/sovertime.Itisrecommendedinthe0909MAGSEP1‐2010Standardthatfinalmagnetsbetestedatleastonceyearlyusingarecentlycalibratedgaussmeter.Theresultsofthesetestscantrendmagnetstrengthdeclineandhelptopinpointearlydemagnetisationduetounforeseenfactorssuchas;

• Temperatureabovethemagnetoperatingtemperaturerating,• Thermalshock,• Corrosion,• Excessivevibration,• PoororcheapRareEarthMagnetsoflowcoercivityrating,• Roughhandlingandimpactbypersonsdoingthemagnetcleaning.

Summary,Specifications&EfficiencyTips;

• Pullstrengthtestsandgaussstrengthtestsshouldnotbeusedasthesolebasistoselectbetweenmagnetsofdifferentmanufacturers.

• Inallcircumstances,itisimportanttoconsider‘whatistheprimeoressentialdutyofthemagnetandtoselectthebestperformingfieldpatternfortrampironprotectionorfinalmagnetsproductpurity.PleaserefertoDiagram“B”onPage6.

• Haveparticularregardforsuitabilityofmagnetdesigntonotlosefragmentsdefinedas<1/8”weaklymagneticandfinecontamination,whicharethebiggestmagneticandmetalcontaminationconcernsinthefoodindustry.

• Calibrateddigitalpulltestersorgaussmetersarenowequallyeffective,reliableandaccurateforcomparingmagnetstrengthlossofanindividualorsetofinstalledmagnetsovertime.

• Whenselectingformagneticseparationefficiency,consider“polecentres”aswellas“strength”.7/8”(22mm)maximumissafefortubesandbarsupto2”diameter.

Highperformingfinalmagnetsandothercriticalmagnetswilluseneodymiumironboronmagnetsofhighcoercivityandresistancetothermalshock,suchasRE80HTorequivalentwithexcessservicetemperatureratingofpreferably302F/150°C.

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• Highperformancefinalmagnetswillalsobesizedforcorrectcoverageofproductstreamandlocatedatorimmediatelyupstreamofpackingorout‐loading.

• Lowergradeorwiderpolecentregratemagnetsoflowercostmaybesuccessfullyusedasmagneticintakescalpingmagnetsoratlargeareabagopeningorblendstationsupstreamoffinalmagnets.Regularmagnetcleaningisessential.

• Ifconsideringself‐cleaninggratetypemagnets,ensurethebarsaresolidandwithoutsleeves,whichareverythintoachievesurfacestrength,butareverysusceptibletoimpactdamageduringcleaningcycles.Also,ensurethereisaneffectivemechanismforequalisingbarabrasionandpreventingbuildupandblockage.MAG‐RAM™separatorsandRotarygratesprovidethesebenefitsinherently.

• DrummagnetsandPlatemagnetshavelongservedwellforremovingheavyanddamagingsizetrampironatintakesandatindividualHammermills,Pinmills,Rollmills,etc.topreventdamageandproliferationofgroundupmagneticmaterial.

• Finally,highperformance,small,lowcost“indicatormagnets”arebecomingpopularforplacingontopofintakeorbagopeninggratesalsointakeblowlines.Theseneedtobesamespecificationasfinalmagnetstoseparateworkhardenedstainlesssteelparticles,etc.

Addendum:THEBELOWTESTRESULTSARETHEBASISSUPPORTINGTHEFACTSANDOPINIONSEXPRESSEDINTHISPAPER.METHOD:

Magnetsinrepulsionwereplacedina1”diametertubeandcompressedwithcircuitvariationscomprising,2mmand4mmwidemildsteelpoleplatesbetweenthem.

Samegrademagnetswereusedtoavoidvariationfromcauseofdifferentgradesusedbydifferentmanufacturersoftubeandbarmagnets.

Samethicknesstubeandstainlesssteelwereusedoneachtesttopreventvariationsfromothercauses.

Calibratedgaussandpulltestmeterswereusedtorecord8readingsontheexternalofthetubeonthecentrelineofeachpoleplatewithmagnetlengthsof20mmand30mm.

Readingsweretherebyrecordedat22mmpolecentres,24mmpolecentres,32mmpolecentresand34mmpolecentres.Thereadingswereaveragedasshownintheresultstable.

8readingsweretakenwitheachinstrumentandaveraged(BrandEandAMRpulltesters,Gaussmeter)

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OBSERVATIONS:

TheBrandEpulltesterreadslightlyhigherthantheAMRinstrument,butwellwithinnormal2%or3%instrumentvariationtolerance.

Gaussmeterreadingswereconsistentwithusualfieldtestreadingsonthesemagnetpolecentrevariations.

RESULTS:

PoleCentrePolePlateWidth

MagnetLength

AverageGaussAverageEriezPullTest

AverageAMRPullTest

0.866”/22mm 0.0787″/2mm 0.787”/20mm 10,694gauss 90.46oz 89.6oz

0.945”/24mm 0.1575”/4mm 0.787”/20mm 9,634gauss 99.18oz 99.0oz

1.26”/32mm 0.0787″/2mm 1.181”/30mm 11,472gauss 93.53oz 92.6oz

1.34”/34mm 0.1575”/4mm 1.181”/30mm 9,987gauss 98.92oz 99.0oz

EXPLANATION: 2mmwidepoleplatesgavethehighestgaussandshortestpolecentres,butlowestpulltest

value. Widerpoleplatesgavehighestpulltestvalue,longerpolecentres,butlowergaussvalue. Longermagnetelementswith2mmwidepoleplates,substantiallyincreasedgauss,slightly

increasedpulltestvalue,butgreatlyincreasedpolecentres. Longermagnetelementswith4mmwidepoleplatesgreatlyreducedthegauss,maintained

thehigherpulltestvaluebutfurtherincreasedthepolecentres.ThefiguresforgaussandpulltestconfirmthatpullinouncesisnotanSIvalue,meaningthereisnotanequivalentratiobetweengaussfluxdensityandouncepulloveravarietyofmagnets.ThisisthereasonpulltestsarenotallowedintheHAACPInternationalStandardasbasisforcertifiedmagnetvalidations.

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WehavealreadydepictedinDiagramBabovethatbecausemorelinesoffluxpassthrougha¼”pulltestballwhenwiderpoleplatesareusedwithinthemagnettube,thismakesthepullvaluehigheralongwithmarginallymoreholdontrampiron3mmandlargerinsize.However,thediagramalsoshowsthathighgaussandshortpolecentresismoreimportantwhenthedutyistoextractandholdweaklymagneticfragmentslessthan3mminsize.Especially,sincethemiddleofeachmagnetinanytubemagnetcircuitis”nilgauss”and“nilpull”.Contaminateparticlesmustmovetothehighgausspolebandsasproductmovespastthemagnetbar.Sincemagneticgaussandpullisalwaysweakatadistancefromthemagnetbar,allmagnetsinsensitivefoodstreamsshouldbedesignedforproductcontact.Theargumentthathigherpullonsurfaceandhigherpullatdistancemeasuredwitha¼’mildsteelballdoesnotproverelevant.Separationoffineandweaklymagneticfragmentsrequiresspecifiedfluxdensityingaussanddistancebetweenpolesastheessentialperformancefactors.Whereproductflowpermits,staggeredmagnetbarsorsplitterbarsorangledeflectorsmaybeusedtofurtherraisemagneticseparationefficiency.

CONCLUSION:

FoodSafetyStandard0909MAGSEP1‐2010forfinalmagnetsinafoodrelatedprocesscorrectlyspecifiesfinalmagnetsshouldbeaminimumof10,000gaussat22mmpolecentres.

Themostefficientmagnetgratetubeorbarforseparatingfineandweaklymagneticcontaminationisnotthemagnetshowinghighestpulltestvalue.Themostefficientmagnetwillhavethehighestgaussatshortestdistancebetweenpolebandscentres.TheMAGSEPStandardcurrentlyexcludespulltestinstruments.However,HACCPInternationalhasconfirmedthatmagnetvalidationsusingcalibratedpulltestinstrumentsmaybeacceptableprovidedthefirstvalidationincludedcalibratedgaussvaluesaspertheStandard.

AMRMagnetValidationReportscanincludebothgaussandpulltestvalues.AMRMagnetValidationReportsarecertifiedbyHACCPInternationalandareavailableglobally.

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ForMagnetvalidationsconformingtoHACCPInternationalFoodSafetyStandard0909MAGSEP1‐2010,lookfortheHACCPCertificationLogoasshownbelow.

CONSULTINGREFERENCE: USAREPRESENTATIVEFORAMR:HACCPInternational D.L.Newslow&AssociatesNorthSydney,Australia Florida,USAwww.haccp‐international.com www.newslow.com

USAREPRESENTATIVEFORMAGNATTACK:

Powder‐Solutions,Inc.Chanhassen,MNwww.powder‐solutions.com

pull testing vs gauss testing - powder … food processing pull testing vs gauss testing ......

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