KOHTECT BT-77 Instruction Manual

BT-77 Bearing Tester
with Non-Contact Tacho
Operating Instruction Manual

KOHTECT BT-77
CONTENT
Page
INTRODUCTION................................................................................1
1.0 BT-77 INSTRUMENT DISCRIPTION AND FUNCTION............1
1.1Specication
1.1.1StandardConditionforOperation
1.1.2SystemSpecication
1.2OverviewonRollingBearingConditionMonitoring
1.3UnderstandingShockInduced“Carpetvalue”and“Maximumvalue”
1.4Tachometer
1.5DesignofBT-77
1.5.1OperationKeys
2.0 TAKING MEASUREMENT WITH THE INSTRUMENT..............7
2.1.Instrumentdisplayandmeasuringmodes
2.1.1Settingthesystemrealtimeanddate
2.2TakingBearingDiagnosisMeasurements
2.2.1Selectionandsettingupthemeasuringpoints
2.2.2Setupinitialparameter&takingbearingmeasurements
2.2.3Takingbearingdiagnosismeasurementandsave
2.2.4Fileformatandopenmeasuredle
2.3EvaluationoftheMeasuringResults
2.4MeasuringRPMbyTachometer
2.4.1SetupinstrumentandmeasuringRPM
2.4.2MeasuringRPMbytheTachometer
3.0 ROLLER BEARING CONDITION MONITORING BY THE
SHOCK PULSE METHOD (MEASUREMENT METHOD)......14
3.1WhatisShockPulseMethod(SPM)anditbasis
3.2HowShockPulseMeasuredandEvaluatedforRollingBearing
3.3EvaluationofBearingConditionwithBT77
3.4Methodandmeasurementlocationofthebearing
4.0 DELIVERY.................................................................................19

KOHTECT BT-77

KOHTECT BT-77
INTRODUCTION
ThismanualisintendedforthestudyoftheBT-77bearingconditiontester.Themanual
containsdescriptionoftheBT-77 bearing checker operating principle, operating
proceduresoftheintendeduseandbearingshockpulseevaluationconcept.
1.0 BT-77 INSTRUMENT DISCRIPTION AND FUNCTION
1.1 Specication
1.1.1StandardConditionsforOperation:
Operatingtemperature(device&sensor),-10to55°С,(±5)°С;
Relativehumidity80%attemperature30°С;
Atmosphericpressure,84to106.7KPa(630-800mmHg);
Resonancefrequency,32kHz;
Measurementunit,dBi,dBc,dBm;
Range,max.99dB;
Resolution,1dB;
Accuracy,±5%;
Operatingtemperature(tacho),10to55°С,(±5)°С;
Tachometerrange,50-30,000rpm;
Tachometerresolution,1rpm;
Tachometersensingdistance,upto1m;
Memorycapacity,2MB;
PCcommunicationport,USB;
1.1.2SystemSpecication
Power supply, 3.6 �iMH rechargeable battery.Powersupply,3.6�iMHrechargeablebattery.
Continuous operation on batteries, not less than 10 hours.Continuousoperationonbatteries,notlessthan10hours.
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KOHTECT BT-77
Current consumption 220, 50 Hz AC, not more than 5A.Currentconsumption220,50HzAC,notmorethan5A.
The limits of complementary error of the instrument at voltage changing fromThelimitsofcomplementaryerroroftheinstrumentatvoltagechangingfrom
3.6oltsto2.8olts.
Probabilityofno-failureoperation,notlessthan0.92per2000hrs.
Theaverageinstrumentlife,notlessthan10years.
Failuretime,1000hours.Theaveragefailuretimeissetforstan-dardconditions
foroperation.
Dimensions,notmorethan60х110х30(mm).
Weight,notmorethan210gram.
1.2 OverviewonRollingBearingConditionMonitoring
Ideally,rollingbearingelementsareseparatedbyaprotectivelubricantlm,which
impedes their collision.  However, manufacturing defects, damages, which appear
duringoperation,dirtinthebearing,insufficientorincorrectlubrication–allthese
factorscausethecollisionofthebearingelementsand,asaresult,acoustic
oscillationsofawidespectrumaregeneratedinthebearingbody.
Aspeciallydesignedtransducer(patent№18652)isusedtolteroutthepartofthis
spectrumthatcarriesinformationonthebearingfaultsdetection.Thetransducerlters
thoseacousticoscillationswhicharegeneratedbythebearingdefects,andconverts
themintoelectronicsignalproportionaltothemagnitudeofshockpulsesignal,thatis
ampliedand measured bytheBT-77electronic unitintherelative units ofdecibels
(dB).
Arealnewbearingisjustfromthebeginningofitsuse,asourceofinducedvibration,
theamplitudeoftheshockpulseofwhichisdBi.
ThedBi,initialvaluedependsonthelargenumberoffactors;however,inpracticeitis
possibletolimitthemtodiameterD(mm)oftheneckanditsrotatingspeed�(rpm).The
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KOHTECT BT-77
valueofdBifeaturestheconditionofanewcorrectlyinstalledandlubricatedbearing.
The shock pulse amplitude increases as a result of wear and improper use. Shock
accelerationamplitudeoverrunningthevalueofdBi -dBsvfeaturesadamage,andis
usedfortheevaluationofbearingcondition.
ThisenableBT-77totellthedifferenceofshockpulsevaluesinduceislowshockand
highshock,anormalizedmeasurementscalecalldBnisuses,seebeneathTable-1.0.
  dBn = 0-25 Goodcondition
  dBn = 25-40 Satisfactorycondition
  dBn > 40 Poorcondition,breakdownrisk
Table-1.0
Fig-1.0
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KOHTECT BT-77
50 -
-dBa-absolutevalueatmeasuringpoint
40 -
-dBsv -valuefeaturesbearingfailure(dBa-dBi)
30 -
20 -
 -dBi-originalvalueoftheshockaccelerationamplitude
10 -
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0 - responsethresholdofthebearingchecker
-5 -
-10 -
Figure-1.1-Anexampleofthesevaluesratio.
Patternoftheinducedoscillations,whichareregisteredbyBT-77,changesaccording
tothebearingfaults.
1.3 UnderstandingShockInduced“Carpetvalue”and“Maximumvalue”
Atthemeasurements,thebearingcheckerallowstolteroutandmeasuretwospecied
valuesoftheshockaccelerationamplitude:theCarpetvalue(dBc)andtheMax.value
(dBm).
ThedBcbackgroundvalue(theCarpet value) refers to the frequent collisions of the
bearingsurfaceroughness,dBcitgivesimportantinformationregardtothelubrication
ofthebearings,howwellthebearinghavebeenmountedandthewayinwhichthey
arebeenloaded,andisindicatedbythecontinuouslightofLED.ThedBmMaxalue
referstotheseparateshocks,characterizingthefaultslevel,andisindicatedbyseparate
LEDashes.
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KOHTECT BT-77
Forinstance,attheshockaccelerationamplitudemeasuringofawelllubricatedand
correctly installed bearing, the dBm is only slightly higher than dBc. But when one
measures shock acceleration amplitude of a bearing having faults, these faults are
detectedbydBmmaximumvalues,atthat,thebackgrounddBcvaluedependsonthe
lubrication condition, and can grow increase substantially when there is insufcient
lubricationfollowedbyfrequentmetal-to-metalcontacts.
IncreaseofdBcbackgroundvaluemaybecausedbyotherreasonsaswell,e.g.atthe
drivecouplingmisalignment.Itiseasytodistinguishbetweenthesecases–withthe
couplingmisalignmenttherewillbethesamepictureforthebearingsonthebothsides
ofthecoupling.
Resultsoftheshockaccelerationamplitudemeasurementfordrivesbearingscanbe
inuencedby shocks produced duringthe running in ofa gear mesh, whichcan be
transferredontothebearings.However,mostlythegearteethhumissolowthatdoes
notimpedethemeasurement.
Withtheshocks,originatedbythegearwheelsdefects,thedBmMaxalueincreases
sharplyforthetwobearingssimultaneously(onbothsidesofgear).
The greatest effect from the technical state monitoring of bearings is reached when
measuringresultsarebeingputongraphagainstthetimefactor.Atthis,aforecastof
thetechnicalstatebecomespossible.Exampleofthemeasurementsresultsprocessing
isgiveninTable-1.0.
1.4 Tachometer
TheTI-7tachometeroperationisbasedonthemeasurementoffrequencyofinfrared
rayreturnfromthereectivetape(oranothermarker)xedontheturningshaft.Awhite
markerpenisprovidesinthepackagesothatusercanmarktherotortogetgood
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KOHTECT BT-77
contrastwhentakingRPMmeasurement.
ThemeasuredRPMreadingcanalsobesavedwithinthedevicewithlenameendby
“tac”extension.
1.5 DesignofBT77
Constructively BT-77 Bearing Tester is designed in a light and strong alloy casing
protectedbysiliconsleevewiththerechargeableinternalbatterypowersupply,socket
forthemeasuringprobeandUSBportfortachometersensorsorleuploadtoPCfor
datamanagement.ThecontrolsandconnectorslocationisshownontheFig.1.2a&
Fig.1.2b.
Fig.1.2a Fig-1.2bTopviewofBT-77
1.BT-77device
2.Bearingshockpulsemeasuringprobe
3.Tachometersensorandmagneticstand
4.Socketformeasuringprobe
5.USBportforTachometersensor/PCcom
6.SocketforACcharger  
7.Softmembranepushpadforoperation
8.Back-litemonochromeLCDdisplay
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