Brookfield DV3T Rheometer Bedienungsanleitung PDF herunterladen (Seite 113)

Brookeld Engineering Labs., Inc. Page 113 Manual No. M13-2100

Appendix F - The Brookeld Guardleg

Theguardlegwasoriginallydesignedtoprotectthespindleduringuse.Therstapplicationsofthe

BrookeldRheometerincludedhandheldoperationwhilemeasuringuidsina55-gallondrum.Itis

clearthatunderthoseconditionsthepotentialfordamagetothespindlewasgreat.Originalconstruction

includedasleevethatprotectedthespindlefromsideimpact.EarlyRVguardlegsattachedtothedial

housingandLVguardlegsattachedtothebottomofthepivotcupwithatwistandlockmechanism.

ThecurrentguardlegisabandofmetalintheshapeoftheletterUwithabracketatthetopthatattaches

tothepivotcupofaBrookeldViscometer/Rheometer.Becauseitmustattachtothepivotcup,the

guardlegcannotbeusedwithaCone/Plateinstrument.AguardlegissuppliedwithallLVandRVseries

instruments,butnotwiththeHAorHBseries.It’sshape(showninFigureF-1andF-2)isdesignedto

accommodatethespindlesoftheappropriatespindleset;therefore,theRVguardlegiswiderthanthe

LVduetothelargediameteroftheRV#2spindle.Theyarenotinterchangeable.

ThecalibrationoftheBrookeldViscometer/Rheometerisdeterminedusinga600mLLowFormGrifn

Beaker.ThecalibrationofLVandRVseriesinstrumentsincludestheguardleg.Thebeakerwall(for

HA/HBinstruments)ortheguardleg(forLV/RVinstruments)denewhatiscalledthe“outerboundary”

ofthemeasurement.ThespindlefactorsfortheLV,RV,andHA/HBspindlesweredevelopedwiththe

aboveboundaryconditions.Thespindlefactorsareusedtoconverttheinstrumenttorque(expressed

asthedialreadingor%Torquevalue)intocentipoise.Theoretically,ifmeasurementsaremadewith

differentboundaryconditions,e.g.,withouttheguardlegorinacontainerotherthan600mLbeaker,

thenthespindlefactorsfoundontheFactorFindercannotbeusedtoaccuratelycalculateanabsolute

viscosity.Changingtheboundaryconditionsdoesnotchangetheviscosityoftheuid,butitdoes

changehowtheinstrumenttorqueisconvertedtocentipoise.Withoutchangingthespindlefactorto

suitthenewboundaryconditions,thecalculationfrominstrumenttorquetoviscositywillbeincorrect.

Practicallyspeaking,theguardleghasthegreatesteffectwhenusedwiththe#1&#2spindlesofthe

LVandRVspindlesets(Note:RV/HA/HB#1spindleisnotincludedinstandardspindleset).Any

otherLV(#3&#4)orRV(#3-#7)spindlecanbeusedina600mLbeakerwithorwithouttheguard

legtoproducecorrectresults.TheHAandHBseriesViscometers/Rheometersarenotsuppliedwith

guardlegsinordertoreducethepotentialproblemswhenmeasuringhighviscositymaterials.HA/

HBspindles#3through#7areidenticaltothosespindlenumbersintheRVspindleset.TheHA/HB

#1&#2haveslightlydifferentdimensionsthanthecorrespondingRVspindles.Thisdimensional

differenceallowsthefactorsbetweentheRVandHA/HB#1&#2spindlestofollowthesameratios

astheinstrumenttorqueeventhoughtheboundaryconditionsaredifferent.

Therecommendedproceduresofusinga600mLbeakerandtheguardlegaredifcultforsomecustomers

tofollow.Theguardlegisonemoreitemtoclean.Insomeapplicationsthe500mLoftestuid

requiredtoimmersethespindlesina600mLbeakerisnotavailable.Inpractice,asmallervesselmay

beusedandtheguardlegisremoved.TheBrookeldViscometer/Rheometerwillproduceanaccurate

andrepeatabletorquereadingunderanymeasurementcircumstance.However,theconversionofthis

torquereadingtocentipoisewillonlybecorrectifthefactorusedwasdevelopedforthosespecic

conditions.Brookeldhasoutlinedamethodforre-calibratingaBrookeldViscometer/Rheometer

toanymeasurementcircumstanceinMoreSolutionstoStickyProblems.Itisimportanttonotethat

formanyrheometerusers,thetrueviscosityisnotasimportantasarepeatabledaytodayvalue.This

repeatablevaluecanbeobtainedwithoutanyspecialeffortforanymeasurementcircumstance.But,it

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