Brookfield DV2T Viscometer Bedienungsanleitung PDF herunterladen (Seite 80)

Brookeld Engineering Labs., Inc. Page 80 Manual No. M13-167-B0614

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Viscometer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

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