Brookfield DV3T User Manual

Brookeld Engineering Labs., Inc. Page 112 Manual No. M13-167-A0415
Appendix G - 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G-1andG-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

Brookfield DV3T Specifications

General

Brand	Brookfield
Model	DV3T
Category	Measuring Instruments
Language	English