Vibration Quick Reference

SIGNATURE ANALYSISSIGNATURE ANALYSISSIGNATURE ANALYSISSIGNATURE ANALYSIS

Which frequencies exist and what are the relationships to the fundamental exciting frequencies.

What are the amplitudes of each peakHow do the peaks relate to each other If there are significant peaks, what are their source

COUPLE UNBALANCECOUPLE UNBALANCECOUPLE UNBALANCECOUPLE UNBALANCECOUPLE UNBALANCECOUPLE UNBALANCECOUPLE UNBALANCECOUPLE UNBALANCE

1800 out of phase on the same shaft 1X RPM always present and normally dominatesAmplitude varies with square of increasing speedCan cause high axial as well as radial amplitudesBalancing requires Correction in two planes at 180o g q p

OVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCEOVERHUNG ROTOR UNBALANCE

1X RPM present in radial and axial directions 1X RPM present in radial and axial directionsAxial readings tend to be in-phase but radial readings

might be unsteadyg yOverhung rotors often have both force and couple

unbalance each of which may require correction

Diagnosing UnbalanceDiagnosing UnbalanceDiagnosing UnbalanceDiagnosing UnbalanceDiagnosing UnbalanceDiagnosing UnbalanceDiagnosing UnbalanceDiagnosing Unbalance

Vibration frequency equals rotor speed.Vib ti d i tl

900

Vibration predominantly RADIAL in direction.

Stable vibration phase 0 Stable vibration phase measurement.

Vibration increases as

900

V b o c e ses ssquare of speed.

Vibration phase shifts in direct proportion to measurement direction.

ECCENTRIC ROTORECCENTRIC ROTORECCENTRIC ROTORECCENTRIC ROTORECCENTRIC ROTORECCENTRIC ROTORECCENTRIC ROTORECCENTRIC ROTOR

Largest vibration at 1X RPM in the direction of the t li f th tcenterline of the rotors

Comparative phase readings differ by 00 or 1800

Att t t b l ill d i lit dAttempts to balance will cause a decrease in amplitude in one direction but an increase may occur in the other direction

ANGULAR MISALIGNMENTANGULAR MISALIGNMENTANGULAR MISALIGNMENTANGULAR MISALIGNMENTANGULAR MISALIGNMENTANGULAR MISALIGNMENTANGULAR MISALIGNMENTANGULAR MISALIGNMENT

Characterized by high axial vibration 1800 phase change across the couplingTypically high 1 and 2 times axial vibrationNot unusual for 1, 2 or 3X RPM to dominate Symptoms could indicate coupling problemsy p p g p

PARALLEL MISALIGNMENTPARALLEL MISALIGNMENTPARALLEL MISALIGNMENTPARALLEL MISALIGNMENTPARALLEL MISALIGNMENTPARALLEL MISALIGNMENTPARALLEL MISALIGNMENTPARALLEL MISALIGNMENT

RadialRadial

11xx 22xx44xx

RadialRadial

High radial vibration 1800 out of phase Severe conditions give higher harmonics Severe conditions give higher harmonics 2X RPM often larger than 1X RPM Similar symptoms to angular misalignment Similar symptoms to angular misalignmentCoupling design can influence spectrum shape and

amplitudeamplitude

BENT SHAFTBENT SHAFTBENT SHAFTBENT SHAFTBENT SHAFTBENT SHAFTBENT SHAFTBENT SHAFT

Bent shaft problems cause high axial vibration 1X RPM dominant if bend is near shaft center 2X RPM dominant if bend is near shaft ends Phase difference in the axial direction will tend

towards 1800 difference

MISALIGNED BEARINGMISALIGNED BEARINGMISALIGNED BEARINGMISALIGNED BEARING

Vibration symptoms similar to angular misalignmentAttempts to realign coupling or balance the rotor will not

alleviate the problem.Will cause a twisting motion with approximately 1800

phase shift side to side or top to bottom

OTHER SOURCES OF HIGH AXIALOTHER SOURCES OF HIGH AXIALOTHER SOURCES OF HIGH AXIALOTHER SOURCES OF HIGH AXIALOTHER SOURCES OF HIGH AXIAL OTHER SOURCES OF HIGH AXIAL VIBRATIONVIBRATION

OTHER SOURCES OF HIGH AXIAL OTHER SOURCES OF HIGH AXIAL VIBRATIONVIBRATION

a. Bent Shaftsb. Shafts in Resonant Whirlc. Bearings Cocked on the Shaftd. Resonance of Some Component in the Axial p

Directione. Worn Thrust Bearingsf. Worn Helical or Bevel Gearsg. A Sleeve Bearing Motor Hunting for its Magnetic

CCenterh. Couple Component of a Dynamic Unbalance

MECHANICAL LOOSENESS (A)MECHANICAL LOOSENESS (A)MECHANICAL LOOSENESS (A)MECHANICAL LOOSENESS (A)( )( )( )( )

Caused by structural looseness of machine feetyDistortion of the base will cause “soft foot” problems Phase analysis will reveal aprox 1800 phase shift in the Phase analysis will reveal aprox 180 phase shift in the

vertical direction between the baseplate components of the machine

MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)MECHANICAL LOOSENESS (B)

Caused by loose pillowblock boltsCan cause 0.5, 1, 2 and 3X RPM Sometimes caused by cracked frame structure or

bearing block

SLEEVE BEARINGSLEEVE BEARINGWEAR / CLEARANCE PROBLEMSWEAR / CLEARANCE PROBLEMS

SLEEVE BEARINGSLEEVE BEARINGWEAR / CLEARANCE PROBLEMSWEAR / CLEARANCE PROBLEMSWEAR / CLEARANCE PROBLEMSWEAR / CLEARANCE PROBLEMSWEAR / CLEARANCE PROBLEMSWEAR / CLEARANCE PROBLEMS

Later stages of sleeve bearing wear will give a large family of harmonics of running speed

A minor unbalance or misalignment will cause high amplitudes when excessive bearing clearances are

tpresent

COMPONENT FREQUENCIES OF A SQUARE COMPONENT FREQUENCIES OF A SQUARE WAVE FORMWAVE FORM

COMPONENT FREQUENCIES OF A SQUARE COMPONENT FREQUENCIES OF A SQUARE WAVE FORMWAVE FORMWAVE FORM.WAVE FORM.WAVE FORM.WAVE FORM.

COMPONENT FREQUENCIES OF A SQUARECOMPONENT FREQUENCIES OF A SQUAREWAVE FORMWAVE FORM

COMPONENT FREQUENCIES OF A SQUARECOMPONENT FREQUENCIES OF A SQUAREWAVE FORMWAVE FORMWAVE FORM.WAVE FORM.WAVE FORM.WAVE FORM.

MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)MECHANICAL LOOSENESS (C)

Phase is often unstableWill have many harmonicsCan be caused by a loose bearing liner, excessive

bearing clearance or a loose impeller on a shaft

ROTOR RUBROTOR RUBROTOR RUBROTOR RUBROTOR RUBROTOR RUBROTOR RUBROTOR RUB

Truncated waveformTruncated waveform

Similar spectrum to mechanical looseness Similar spectrum to mechanical loosenessUsually generates a series of frequencies which may

excite natural frequenciesexcite natural frequencies Subharmonic frequencies may be presentRub may be partial or through a complete revolutionRub may be partial or through a complete revolution.

RESONANCERESONANCERESONANCERESONANCE

Resonance occurs when the Forcing Frequency i id ith N t l Fcoincides with a Natural Frequency

1800 phase change occurs when shaft speed passes through resonancethrough resonance

High amplitudes of vibration will be present when a system is in resonancey

BELT PROBLEMS (D)BELT PROBLEMS (D)BELT PROBLEMS (D)BELT PROBLEMS (D)BELT RESONANCEBELT RESONANCE

RADIAL

1X RPM

BELT RESONANCE

High amplitudes can be present if the belt natural frequency coincides with driver or driven RPM

High amplitudes can be present if the belt natural frequency coincides with driver or driven RPM

Belt natural frequency can be changed by altering the belt tension

Belt natural frequency can be changed by altering the belt tension

BELT PROBLEMS (A)BELT PROBLEMS (A)BELT PROBLEMS (A)BELT PROBLEMS (A)WORN LOOSE OR MISMATCHED BELTSWORN LOOSE OR MISMATCHED BELTSWORN, LOOSE OR MISMATCHED BELTSWORN, LOOSE OR MISMATCHED BELTS

BELT FREQUENCYHARMONICSHARMONICS

Often 2X RPM is dominantOften 2X RPM is dominantOften 2X RPM is dominantAmplitudes are normally unsteady, sometimes pulsing

with either driver or driven RPM

Often 2X RPM is dominantAmplitudes are normally unsteady, sometimes pulsing

with either driver or driven RPMWear or misalignment in timing belt drives will give high

amplitudes at the timing belt frequencyWear or misalignment in timing belt drives will give high

amplitudes at the timing belt frequencyBelt frequencies are below the RPM of either the driver

or the drivenBelt frequencies are below the RPM of either the driver

or the driven

BELT PROBLEMS (C)BELT PROBLEMS (C)BELT PROBLEMS (C)BELT PROBLEMS (C)ECCENTRIC PULLEYSECCENTRIC PULLEYS

RADIAL1X RPM OFECCENTRICPULLEYPULLEY

Eccentric or unbalanced pulleys will give a high 1X RPM of the pulley

Eccentric or unbalanced pulleys will give a high 1X RPM of the pulley

The amplitude will be highest in line with the beltsBeware of trying to balance eccentric pulleys The amplitude will be highest in line with the beltsBeware of trying to balance eccentric pulleys

BELT PROBLEMS (B)BELT PROBLEMS (B)BELT PROBLEMS (B)BELT PROBLEMS (B)BELT / PULLEY MISALIGNMENTBELT / PULLEY MISALIGNMENT

1X DRIVEROR DRIVEN

Pulley misalignment will produce high axial vibration Pulley misalignment will produce high axial vibration at 1X RPM

Often the highest amplitude on the motor will be at the fan RPM

at 1X RPMOften the highest amplitude on the motor will be at the

fan RPMfan RPMfan RPM

HYDRAULIC AND HYDRAULIC AND AERODYNAMIC FORCESAERODYNAMIC FORCES

HYDRAULIC AND HYDRAULIC AND AERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCES

BPF = BLADE PASS FREQUENCY

If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitudeHi h BPF b if i ll i i

If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitudeHi h BPF b if i ll i iHigh BPF may be present if impeller wear ring seizes on shaft

Eccentric rotor can cause amplitude at BPF to be

High BPF may be present if impeller wear ring seizes on shaft

Eccentric rotor can cause amplitude at BPF to beEccentric rotor can cause amplitude at BPF to be excessive

Eccentric rotor can cause amplitude at BPF to be excessive

HYDRAULIC AND HYDRAULIC AND AERODYNAMIC FORCESAERODYNAMIC FORCES

HYDRAULIC AND HYDRAULIC AND AERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCESAERODYNAMIC FORCES

FLOW TURBULENCEFLOW TURBULENCE

Flow turbulence often occurs in blowers due to Flow turbulence often occurs in blowers due to Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ducts

Random low frequency vibration will be generated,

Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ducts

Random low frequency vibration will be generated,Random low frequency vibration will be generated, possibly in the 50 - 2000 CPM range

Random low frequency vibration will be generated, possibly in the 50 - 2000 CPM range

HYDRAULIC AND AERODYNAMIC HYDRAULIC AND AERODYNAMIC FORCESFORCES

HYDRAULIC AND AERODYNAMIC HYDRAULIC AND AERODYNAMIC FORCESFORCESFORCESFORCESFORCESFORCES

CAVITATIONCAVITATIONCAVITATIONCAVITATION

Cavitation will generate random, high frequency broadband energy superimposed with BPF harmonics

Cavitation will generate random, high frequency broadband energy superimposed with BPF harmonics

Normally indicates inadequate suction pressureErosion of impeller vanes and pump casings may

if l ft h k d

Normally indicates inadequate suction pressureErosion of impeller vanes and pump casings may

if l ft h k doccur if left unchecked Sounds like gravel passing through pump

occur if left unchecked Sounds like gravel passing through pump

BEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONWIDEBAND SPECTRUM

F1 F2

ZOOMSPECTRUM

A beat is the result of two closely spaced frequencies going into and out of phase

A beat is the result of two closely spaced frequencies going into and out of phase

The wideband spectrum will show one peak pulsating up and downTh diff b t th k i th b t f

The wideband spectrum will show one peak pulsating up and downTh diff b t th k i th b t fThe difference between the peaks is the beat frequency which itself will be present in the wideband spectrum

The difference between the peaks is the beat frequency which itself will be present in the wideband spectrum

ELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMS

STATOR ECCENTRICITYSTATOR ECCENTRICITYSHORTED LAMINATIONSSHORTED LAMINATIONSSHORTED LAMINATIONSSHORTED LAMINATIONSAND LOOSE IRONAND LOOSE IRON

Stator problems generate high amplitudes atStator problems generate high amplitudes at 2FL (2X line frequency )

Stator eccentricity produces uneven stationary airStator eccentricity produces uneven stationary air gap, vibration is very directional

S ft f t d t i t tSoft foot can produce an eccentric stator

FREQUENCIES PRODUCED BY ELECTRICAL FREQUENCIES PRODUCED BY ELECTRICAL FREQUENCIES PRODUCED BY ELECTRICAL FREQUENCIES PRODUCED BY ELECTRICAL MOTORS.MOTORS.MOTORS.MOTORS.

•• Electrical line frequency.(Electrical line frequency.(FLFL) = ) = 5050Hz = Hz = 3000 3000 cpm.cpm.6060HZ = HZ = 3600 3600 cpmcpm

•• Electrical line frequency.(Electrical line frequency.(FLFL) = ) = 5050Hz = Hz = 3000 3000 cpm.cpm.6060HZ = HZ = 3600 3600 cpmcpmpp

•• No of poles.No of poles. ((PP) )

•• Rotor Bar Pass Frequency (Rotor Bar Pass Frequency (FbFb) =) = No of rotor bars xNo of rotor bars x

pp•• No of poles.No of poles. ((PP) )

•• Rotor Bar Pass Frequency (Rotor Bar Pass Frequency (FbFb) =) = No of rotor bars xNo of rotor bars x•• Rotor Bar Pass Frequency (Rotor Bar Pass Frequency (FbFb) = ) = No of rotor bars x No of rotor bars x Rotor rpm. Rotor rpm.

•• Synchronous speed (Synchronous speed (NN )) 22xFLxFL

•• Rotor Bar Pass Frequency (Rotor Bar Pass Frequency (FbFb) = ) = No of rotor bars x No of rotor bars x Rotor rpm. Rotor rpm.

•• Synchronous speed (Synchronous speed (NN )) 22xFLxFL•• Synchronous speed (Synchronous speed (NsNs)) = = 22xFLxFLPP

•• Slip frequency ( Slip frequency ( FFSS )= )= Synchronous speed Synchronous speed -- Rotor rpm.Rotor rpm.

•• Synchronous speed (Synchronous speed (NsNs)) = = 22xFLxFLPP

•• Slip frequency ( Slip frequency ( FFSS )= )= Synchronous speed Synchronous speed -- Rotor rpm.Rotor rpm.y (y ( S S ))•• Pole pass frequency (Pole pass frequency (FFPP )=)= Slip Frequency x No of Poles.Slip Frequency x No of Poles.

y (y ( S S ))•• Pole pass frequency (Pole pass frequency (FFPP )=)= Slip Frequency x No of Poles.Slip Frequency x No of Poles.


SYNCHRONOUS MOTORSYNCHRONOUS MOTORSYNCHRONOUS MOTORSYNCHRONOUS MOTOR(Loose Stator Coils)(Loose Stator Coils)

Loose stator coils in synchronous motors generate high amplitude at Coil Pass FrequencyTh il f ill b d d b 1XThe coil pass frequency will be surrounded by 1X RPM sidebands


POWER SUPPLYPOWER SUPPLYPOWER SUPPLYPOWER SUPPLYPHASE PROBLEMSPHASE PROBLEMS(Loose Connector)(Loose Connector)

Phasing problems can cause excessive vibration at 2FL with 1/3 FL sidebands

Levels at 2FL can exceed 25 mm/sec if left uncorrected Particular problem if the defective connector is only

i ll ki t toccasionally making contact


ECCENTRIC ROTORECCENTRIC ROTOR((Variable Air GapVariable Air Gap))ECCENTRIC ROTORECCENTRIC ROTOR((Variable Air GapVariable Air Gap))((Variable Air GapVariable Air Gap))((Variable Air GapVariable Air Gap))

Eccentric rotors produce a rotating variable air gap, this induces pulsating vibration

Often requires zoom spectrum to separate 2FL and running speed harmonic

Common values of FP range from 20 - 120 CPM


DC MOTOR PROBLEMSDC MOTOR PROBLEMSDC MOTOR PROBLEMSDC MOTOR PROBLEMS

DC motor problems can be detected by the higher than normal amplitudes at SCR firing rateTh bl i l d b k fi ld i diThese problems include broken field windings

Fuse and control card problems can cause high amplitude peaks at frequencies of 1X to 5X Line Frequencypeaks at frequencies of 1X to 5X Line Frequency

ELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSROTOR PROBLEMSROTOR PROBLEMSROTOR PROBLEMSROTOR PROBLEMS

1X, 2X, 3X, RPM with pole pass frequency sidebands indicates rotor bar problems.

2X line frequency sidebands on rotor bar pass frequency (RBPF) indicates loose rotor bars.Oft hi h l l t 2X & 3X t b fOften high levels at 2X & 3X rotor bar pass frequency and only low level at 1X rotor bar pass frequency.

ROTOR BAR FREQUENCIES ROTOR BAR FREQUENCIES ROTOR BAR FREQUENCIES ROTOR BAR FREQUENCIES (SLOT NOISE)(SLOT NOISE)(SLOT NOISE)(SLOT NOISE)

POLEPOLE POLEPOLE

MINIMUMMINIMUM MAXIMUMMAXIMUM

MAXMAX

MINMIN

CALCULATION OF GEAR MESH CALCULATION OF GEAR MESH FREQUENCIESFREQUENCIES

CALCULATION OF GEAR MESH CALCULATION OF GEAR MESH FREQUENCIESFREQUENCIESFREQUENCIESFREQUENCIESFREQUENCIESFREQUENCIES

17001700 RPMRPM

5151 TEETHTEETH

1700 1700 RPMRPM

51 51 TEETHTEETH

3131 TEETHTEETH

20 20 TEETHTEETH

31 31 TEETHTEETH

8959 8959 RPM RPM ---- HOW MANY TEETH ON THIS GEAR?HOW MANY TEETH ON THIS GEAR?

GEARSGEARSNORMAL SPECTRUMNORMAL SPECTRUM

GEARSGEARSNORMAL SPECTRUMNORMAL SPECTRUMNORMAL SPECTRUMNORMAL SPECTRUMNORMAL SPECTRUMNORMAL SPECTRUM

GMF= 21k CPM2625 rpm

8 teeth GMF= 21k CPM

1500 rpm14 teeth

Normal spectrum shows 1X and 2X and gear mesh frequency GMF

GMF commonly will have sidebands of running speedAll peaks are of low amplitude and no natural

f i tfrequencies are present

GEARSGEARSTOOTH LOADTOOTH LOAD

GEARSGEARSTOOTH LOADTOOTH LOADTOOTH LOADTOOTH LOADTOOTH LOADTOOTH LOAD

Gear Mesh Frequencies are often sensitive to loadGear Mesh Frequencies are often sensitive to loadHigh GMF amplitudes do not necessarily indicate a

problemproblemEach analysis should be performed with the system at

maximum load

GEARSGEARSTOOTH WEARTOOTH WEAR

GEARSGEARSTOOTH WEARTOOTH WEARTOOTH WEARTOOTH WEARTOOTH WEARTOOTH WEAR

8 teeth GMF = 21k CPM

14 teeth

8 teeth2625 rpm

GMF = 21k CPM

1500 rpm

Wear is indicated by excitation of natural frequencies along with sidebands of 1X RPM of the bad gearalong with sidebands of 1X RPM of the bad gear

Sidebands are a better wear indicator than the GMFGMF may not change in amplitude when wear occursGMF may not change in amplitude when wear occurs

GEARSGEARSGEAR ECCENTRICITY AND BACKLASHGEAR ECCENTRICITY AND BACKLASH

GEARSGEARSGEAR ECCENTRICITY AND BACKLASHGEAR ECCENTRICITY AND BACKLASHGEAR ECCENTRICITY AND BACKLASHGEAR ECCENTRICITY AND BACKLASHGEAR ECCENTRICITY AND BACKLASHGEAR ECCENTRICITY AND BACKLASH

Fairly high amplitude sidebands around GMF suggest Fairly high amplitude sidebands around GMF suggest eccentricity, backlash or non parallel shafts

The problem gear will modulate the sidebandsThe problem gear will modulate the sidebands Incorrect backlash normally excites gear natural

frequencyq y

GEARSGEARSGEAR MISALIGNMENTGEAR MISALIGNMENT

GEARSGEARSGEAR MISALIGNMENTGEAR MISALIGNMENTGEAR MISALIGNMENTGEAR MISALIGNMENTGEAR MISALIGNMENTGEAR MISALIGNMENT

Gear misalignment almost always excites second order or higher harmonics with sidebands of running speed

Small amplitude at 1X GMF but higher levels at 2Xand 3X GMFand 3X GMF

Important to set Fmax high enough to capture at least2X GMF2X GMF

GEARSGEARSCRACKED / BROKEN TOOTHCRACKED / BROKEN TOOTH

GEARSGEARSCRACKED / BROKEN TOOTHCRACKED / BROKEN TOOTHCRACKED / BROKEN TOOTHCRACKED / BROKEN TOOTHCRACKED / BROKEN TOOTHCRACKED / BROKEN TOOTH

TIME WAVEFORM

A cracked or broken tooth will generate a high amplitude at 1X RPM of the gear

It will excite the gear natural frequency which will be sidebanded b the r nning speed f ndamentalsidebanded by the running speed fundamental

Best detected using the time waveformTi i t l b t i t ill b th i l fTime interval between impacts will be the reciprocal of

the 1X RPM

D0

DD BPFI =Nb

2Bd

PdRPM(

(

1 + COS XD1DB

2 Pd(

(

N ( B (

X RPMBPFO = Nb

2 ( 1 - Bd

PdCOS

(

X RPM

BSF =Pd

2Bd ((

1 - Bd

Pd( COS2 (

XRPM

FTF =12 ( (

COS1-Bd

PdX RPM

Note : shaft turningt fi d

FTF = 2 ( (

Pd

outer race fixedF = frequency in cpmeque cy cpN = number of balls

ROLLING ELEMENT BEARINGSROLLING ELEMENT BEARINGSROLLING ELEMENT BEARINGSROLLING ELEMENT BEARINGSROLLING ELEMENT BEARINGS ROLLING ELEMENT BEARINGS STAGE STAGE 1 1 FAILURE MODEFAILURE MODE

ROLLING ELEMENT BEARINGS ROLLING ELEMENT BEARINGS STAGE STAGE 1 1 FAILURE MODEFAILURE MODE

ZONE BZONE A ZONE C ZONE D

gSE

Earliest indications in the ultrasonic rangeThese frequencies evaluated by Spike EnergyTM gSE, q y p gy g ,

HFD(g) and Shock PulseSpike Energy may first appear at about 0.25 gSE for thisSpike Energy may first appear at about 0.25 gSE for this

first stage

ROLLING ELEMENT BEARINGS ROLLING ELEMENT BEARINGS STAGESTAGE 22 FAILURE MODEFAILURE MODE

ROLLING ELEMENT BEARINGS ROLLING ELEMENT BEARINGS STAGESTAGE 22 FAILURE MODEFAILURE MODESTAGE STAGE 2 2 FAILURE MODEFAILURE MODESTAGE STAGE 2 2 FAILURE MODEFAILURE MODE

ZONE AZONE A ZONE B ZONE C ZONE D

gSE

Slight defects begin to ring bearing component natural frequencies q

These frequencies occur in the range of 30k-120k CPMAt the end of Stage 2 sideband frequencies appear aboveAt the end of Stage 2, sideband frequencies appear above

and below natural frequencySpike Energy grows e g 0 25 0 50gSESpike Energy grows e.g. 0.25-0.50gSE



ZONE A ZONE B ZONE C ZONE D

gSEgSE

Bearing defect frequencies and harmonics appearMany defect frequency harmonics appear with wear the number of

sidebands growW i i ibl d t d d th i h f thWear is now visible and may extend around the periphery of the bearing

Spike Energy increases to between 0 5 1 0 gSE Spike Energy increases to between 0.5 -1.0 gSE



gSE

ZONE A ZONE B ZONE C

High just priorto failure

Discreet bearing defect frequencies disappear and are replaced by g q pp p yrandom broad band vibration in the form of a noise floor

Towards the end, even the amplitude at 1 X RPM is effectedHi h f i fl lit d d S ik E iHigh frequency noise floor amplitudes and Spike Energy may in fact decrease

Just prior to failure gSE may rise to high levels Just prior to failure gSE may rise to high levels

GEARSGEARSHUNTING TOOTHHUNTING TOOTH

GEARSGEARSHUNTING TOOTHHUNTING TOOTHHUNTING TOOTHHUNTING TOOTHHUNTING TOOTHHUNTING TOOTH

fHt = (GMF)Na(TGEAR)(TPINION)

Vibration is at low frequency and due to this can often b i dbe missed

Synonymous with a growling soundTh ff t h th f lt i i dThe effect occurs when the faulty pinion and gear teeth both enter mesh at the same time

Faults may be due to faulty manufacture or Faults may be due to faulty manufacture or mishandling

OIL WHIP INSTABILITYOIL WHIP INSTABILITYOIL WHIP INSTABILITYOIL WHIP INSTABILITYoil whip

oil whirl

Oil whip may occur if a machine is operated at 2X the rotor critical frequency.

When the rotor drives up to 2X critical, whirl is close to critical and excessive vibration will stop the oil film from supporting the shaftthe oil film from supporting the shaft.

Whirl speed will lock onto rotor critical. If the speed is increased the whipfrequency will notspeed is increased the whipfrequency will not increase.

OIL WHIRL INSTABILITYOIL WHIRL INSTABILITYOIL WHIRL INSTABILITYOIL WHIRL INSTABILITY

Usually occurs at 42 - 48 % of running speedVibration amplitudes are sometimes severeVibration amplitudes are sometimes severeWhirl is inherently unstable, since it increases

centrifugal forces therefore increasing whirl forcescentrifugal forces therefore increasing whirl forces

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