Intermediate Vibration AnalysisIMRAN AHMADDirector TechnicalSUMICO Technologies (Pvt) Ltd+92 321 427 6092imran.ahmad@sumico.com.pkwww.sumico.com.pk

Timings1st Session 9000-1030Tea Break 1030-10452nd Session 1045-1300Lunch Break(Prayer)1300-14003rd Session1400-1530Tea Break1545-16004th Session 1600-1700

Basics of VibrationIntroduction:What is Vibration?

Principle of Vibration AnalysisMechanical faults generate unique vibration Geometry of the machinediameter of the shaft, number of bearing elements, etc.Turning speed (e.g. RPM)

Mechanical Defects detected with vibration analysis

Belt drive faultsImbalanceMisalignmentBent shaftLoosenessMachine resonanceCavitationShaft RubBearing Defects including:cage defectouter race defectinner race defectrolling element defectGear defectsElectrical faults

What is Vibration?In simple terms vibration is :- A response to some form of excitationThe free movement of the shaft in a journal bearing will cause it to vibrate when a forcing function is appliedWhat is Vibration ?Vibration is the motion of a body about a reference position caused by a force

What is Vibration?Vibration is a pulsating motion of a machine or a machine part from its original position of rest and can be represented by the formula: Vibration Amplitude Response = Dynamic Force __________________

Dynamic Resistance

Vibration from Mechanical Faults

Vibration from Mechanical Faults

Vibration from Mechanical Faults

Vibration from Mechanical Faults

Vibration from Mechanical Faults

Vibration from Mechanical Faults

How Much Vibration is Too Much ?1. Use Absolute Vibration Levels - Given by machine makers - Published Vibration Severity Standards eg. ISO 2372, VDI 2056, BS 4675 2. Use Relative Vibration Levels Vibration Fundamentals

ISO 10816-3

ISO 10816-3

Vibration standards are guidelinesISO2372 ( BS 4675 , VDI 2056 )

Vibration CharacteristicsAmplitude How Much

Frequency How Often

Phase When

Vibration CharacteristicsAmplitude

Amplitude is the magnitude of vibration expressed in terms of signal level (millivolts or milliamps) or in engineering units ( Micron, mils, milli meter per second or inch per second)There are many ways of measuring vibration amplitude levels, the most common are: peak to peak, zero to peak, root mean square (RMS), average and crest factor. Zero to peak or peak is the measurement from the zero line to the top of the positive peak or the bottom of the negative peak. Peak=1.414 x RMS RMS=0.707 x PEAK VALUEPeak to peak is the distance from the top of the positive peak to the bottom of the negative peak. This measurement is used most often when referring to displacement amplitude Pk-Pk=2 x PEAK VALUE

Vibration CharacteristicsThe average value is 0,637 times the peak of a sin wave; average values are measured by most analog meters. Avg=0.637 x PEAK VALUEThe crest factor is determined by dividing the peak value by the RMS value. For a true sine wave Crest Factor = 1/.707 = 1.414

Vibration Characteristics

There are three types of measurements used to display amplitude. These are

DisplacementVelocity Acceleration

Vibration CharacteristicsDisplacementis the distance that shaft moves in relation to reference point. The total movement of the shaft is measured in Peak to Peak.Velocityis the displacement of the shaft in relation to time? It is measured in RMS (Root Mean Square) or Peak.Accelerationis defined as the change in velocity over time. With this value we want the maximum impact (Force) generated, so we use the Peak or RMS measurement.

Vibration CharacteristicsAmplitude Units Metric

DisplacementmPk-PkVelocitymm/secRMSAccelerationgsPk

Vibration CharacteristicsAmplitude Units English

DisplacementmilsPk-PkVelocityinch/secPkAccelerationgsRMS

Vibration Characteristics - Amplitude RelationshipsThe three types of amplitude measurements used to display data are directly related to each otherChanging from one amplitude unit to the next alters the way in which the data is displayedVelocity is the default unit for standard data collection techniquesHigh and low frequency events can be seenDisplacement measures low frequency events ignoring high frequenciesRelative shaft motion Acceleration accentuates the high frequencies ignoring the low frequenciesGood for early bearing detection (Whenever there is Metal to Metal Impacting involve)

Vibration Amplitude Measuring UnitsAccelerationGs or in/s2(180 deg phase lead) VelocityMm/ses or inches/sec(90 deg phase lead )DisplacementAcceleration, a

Velocity, v = a / 2 f

Displacement = a/4 2 f 2 VelocityAcceleration90 oTime90 oDisplacementm 0r .000inch or MilsVibration Characteristics

Vibration CharacteristicsFrequency

Measure of the number of cycles of vibration that occur in a specific period of time Tells us at what rate the vibration is occurringReciprocal of the Period (T)Measured in Hz /CPMConverted by a factor of 60CPM relates directly to machine RPMThe time required to complete one full cycle of vibration

Frequency refers to how often something occurs:How often a shaft rotates?How often a rolling element hits a defected race?There are three ways to express frequency:CPM Cycles Per Minute1CPM = 1RPMHz Cycles Per SecondCPM / 60Orders Multiples of Turning SpeedFrequency/Turning Speed Consider a motor has a rotational speed of 1485RPM, in terms of frequency this equates to:1485 CPM (1rpm = 1cpm)24.75 Hz (1485/60) (minutes to seconds)1 Orders(1 x revolution of the shaft)Vibration Characteristics

Vibration CharacteristicsFrequency

The table below demonstrates the relationship between the different frequency units over a range of frequencies.

Motor Turning Speed = 1500 RPMCPM150022503000600012000Hz2537.550100200Orders11.5248

Stress = Displacement

0-600 CPM

Fatigue = Velocity

600-120,000 CPM

Force = Acceleration

Above 120,000 CPMVibration InstituterecommendationVibration Characteristics what to use ?

Vibration CharacteristicsSignificance of Frequency

Essential to pinpoint the cause of a machine problem

The forces that causes vibration are usually generated through the rotating motion of the machine parts. These changes in direction and amplitude according to rotational speed of the machine components, most vibration problem will have frequencies that directly related to the rotational speed.

Vibration frequency is an analysis or diagnostics tool

Vibration Characteristics - What is Phase?Phase is the measure of time difference expressed in degrees between two events occurring at the same frequencyPhase is the relationship of vibration motion with respect to an other vibration part or fixed reference point

1 Cycle = 360180AB90ABA & B are180 degreesout of phaseABABA & B are90 degreesout of phaseVibration Characteristics - What is Phase?

Two Types of PhaseAbsolute phaseAbsolute phase is the relationship of the Peak of vibration and a fixed reference Signal (once per revolution)

Relative PhaseRelative phase is the relationship between two Peaks of vibration signals

Absolute PhasePhase lag angle between once per turn marker andfirst positive peak in a vibration waveformExpress in degrees phase lagMust be filtered to multiple of turning speedabAbsolute Phase = a/b X 360o

Relative PhasePhase lag angle between positive peaks of twoseparate vibration signals (equivalent events)The two signal must be same vibration unit (eg. vel & vel or displ & displ)Signal B lags signal A by 110oVelocity signal AVelocity signal B110o

-Phase measurements are not taken during routine data collection of predictive maintenance-However, when developing problems are found comparative phase readings can provide valuable information pinpointing the specific problem

Significance of Phase

Conversion of UnitsMetric Units

where:D=Peak-Peak Displacement (m Pk-Pk)V= Peak Velocity (mm/sec Pk)A= Peak Acceleration (gs Pk)F= Frequency (CPM)

V = DF / 19,100V = 3690A / FA = DF2 / 70,470,910D = 19,100V / FA = VF / 3690D = 70,470,910 / F2

Conversion of UnitsEnglish Units

where:D=Peak-Peak Displacement (mils Pk-Pk)V= Peak Velocity (inch/sec Pk)A= Peak Acceleration (gs Pk)F= Frequency (CPM)

V = DF / 19,100V = 93,640A / FA = DF2 / 1,790,000,000D = 19,100V / FA = VF / 93,640D = 1,790,000,000 / F2

Time WaveformsYou can also look at vibration as the amount of Time it takes to complete a particular cycleIf we examine the motion of a forcing function on a fan blade Heavy Spot over a period of time a distinct signature will occur.This motion is called a sine wave. The horizontal axis is measuring TimeThe vertical axis is measuring AmplitudeThis is known as a Time WaveformAmplitude versus Time

Time WaveformsUnfortunately there are multiple sources of forcing functions that can emit from a machine or component. Thus resulting in the time waveform becoming complex in natureThe plot shown on the right is a complex time waveform.Amplitude versus TimeThis is just one format (domain) for analysing vibration data. Data can also be analysed in a Spectrum (Amplitude Vs Frequency) through a process known as the FFT

Fast Fourier Transform FFT ProcessWhen a problem starts to develop within a rotating component it will generate a vibration signature. This signature should be captured in the time waveformDistinguishing that signature can be very difficult when looking at a time plotTo understand the problem we need to understand the frequencyHow often is it occurring? The FFT is a process that determines the frequency of a signal from a time waveform.The FFT is named after an 18th century mathematician named Jean Baptise Joseph Fourier. He established:Any periodic signal can be represented as a series of sine's and cosines. Meaning if you take a time waveform and mathematically calculate the vibration frequency, it can be converted to a more familiar format

How the Vibration Spectrum is Created

Frequency DomainThe frequency domain (Spectrum) plots the data as Amplitude in the (Y) axis and Frequency in the (X) axis. This data is derived from the time domain mathematical manipulation of the time waveform. Recall the waveform and spectrum from the previous slide. If you tried to determine all the frequencies from the waveform plot, you would need all day just to analyse one point of data. As the FFT plots the frequencies from the waveform for you the analysis of this data becomes easier and reduces the amount of time needed for analysis of each point.

Harmonic - OrdersHarmonics are cursors that are exact multiples of the primary frequencyThey are used to locate other frequencies related to the primary cursorTherefore:When the primary cursors is located on 1Order all the harmonics will be synchronousHarmonic cursors can be used to show non-synchronous and sub-synchronous harmonics depending upon the energy of the primary frequency

Energy in the Spectrum

Synchronous EnergySynchronous energy - related to turning speed.All the other peaks are harmonics off, which means they are related to the first peakWe can see from the spectrum that the first peak is at 1 Orders (which means it is 1 x turning speed)

Examples of synchronous energy:1) Imbalance2) Misalignment3) Gearmesh

Non-Synchronous EnergyNon-synchronous energy - not related to turning speedWe can see from the spectrum that the first peak is at 10.24 Orders. This is not related to turning speed. Examples of non-synchronous energy: BearingsMultiples of belt frequencyOther Machine Speeds

Sub-Synchronous EnergySub-synchronous energy - Less than turning speedThe spectrum shows the first impacting peak below 1 Order. This is sub-synchronous energyExamples of sub-synchronous energy are:Belt FrequenciesOther Machine SpeedsCage Frequencies

SynchronousN x RPM where N is an integer Sub-synchronous1x RPM but not integerEnergy in a Spectrum

Causes of Sub Synchronous EnergyFrequencies that show below the rotational frequency (Less than 1 Order) are sub synchronous.Another componentCage frequenciesPrimary belt frequencyOil whirl (plain bearings)

Causes of Synchronous EnergyFrequencies that are equal too or a direct multiple of running speed are SynchronousPossible causes of Synchronous energy are:ImbalanceMisalignmentLoosenessVane pass frequencyGears etc

Causes of Non Synchronous EnergyFrequencies above (but not integer multiples of) turning speed are non synchronous.Possible causes of non synchronous energy are:Another component Antifriction bearingsElectricalSystem resonancesMultiples of belt frequency

Lines of ResolutionLines of resolution determine the clarity of the spectral data The better the resolution the more accurate the frequency displayedThe number of lines of resolution selected are divided into the maximum frequency scale (Fmax) to arrive at the bin width (BW). BW = Fmax/LOR

The lines are actually centre frequencies of bins of energyAll the energy within the bin is summed up to give a single amplitude frequency

ResolutionBW = Fmax / LOREnergy is summed up within a Bin and plotted at the centre frequencyCentre FrequencyBandwidth

Lines of ResolutionThe spectrum shown displays data at 800 L.O.R with an Fmax of 1600 HzThe second spectrum displays the same data but with 3200 L.O.R over the same Fmax

VIBRATION MEASURING INSTRUMENTS

Choosing Your InstrumentationWhat do you want to achieve?What is your present and future budget for equipment & training?Person power? Knowledge level?Number of machines to be monitored?Type of machines to be monitored?Environment?

INSTRUMENT TYPESOverall Level MetersQuick Check AnalyzersFFT Data Collector/ AnalysersFull Feature Analyzers Real Time Spectrum AnalyzersInstrument Quality Tape Recorders Dedicated Balancing instruments

Real Time RateThe Highest rate at which data can be captured and displayed without leaving any gaps in the analysis.

Vibration Transducers OverviewandSelection

Transducer TypesSeismic:- Bearing relative to space.Velocity Pickups AccelerometersPiezoelectric velocity pickupsRelative:- Shaft relative to bearing.Non-contact Eddy Current Displacement ProbesAbsolute:- Shaft relative to space.Shaft Contact Displacement Probes (including Shaft Sticks and Shaft Riders)

Seismic TransducerVELOCITY PICKUP

Velocity PickupsNote :- There are two types of velocity pickups the above advantages do not apply to piezoelectric velocity transducers. ADVANTAGES

Self- Generating No On-board Electronics Strong signal

SESMIC TRANSDUCERSACCELEROMETERS

Accelerometers - advantagesNo moving parts, no wear.Rugged.Very large dynamic range.Wide frequency range.Compact, often low weight.High stability.Can be mounted in any orientation.

Accelerometer TypesThe three most common are :-Compression Type Inverted Compression TypeShear Type

Compression type accelerometerElectric connectorSeismic MassPreload StudAcoustic ShieldPiezoelectric MaterialICP AmplifierMounting StudReceptacleBase

Compression Type AccelerometersAdvantagesRelatively low costDisadvantagesSensitive to base strainSensitive to Thermal transientsCan cause over-saturation and transducer settling problems Widely used

Inverted compression typePiezoelectric MaterialICP CircuitMounting stud receptacleSeismic MassPreload Sleeve

Shear Type Accelerometer

Advantages - Shear TypeLower sensitivity to base strainLarge dynamic range Much less sensitive to temperature transientsStabilizes quickly when taking measurements at low frequencies.Disadvantage: -Generally higher cost due to added components

Piezoelectric Velocity PickupMassPiezoelectric DisksBaseConnectorINTEGRATOR

Non-contact Eddy Current Probe (Relative)

Non-contact Pickups

Non-contact Eddy Current Displacement ProbesUSED FOR:-Relative Shaft Vibration.Radial & axial shaft position.Differential expansion between case and rotor. Especially effective on machinery with high mass rigid casings and relatively low mass rotors supported in journal type bearings.

N.C.P Problems & precautions Only Measures Displacement - Sensitive Only to low frequency defects.

Subject to Mechanical and Electrical Run-out .

Units must be pre calibrated for specific shaft materials.

Shaft Contact Displacement Probes (Absolute)Shaft SticksHardwood, fish-tail, fixed to accelerometer or velocity pickupMeasures vibration amplitude & phaseShaft Riders

SHAFT SURFACENON-METALLIC TIPMACHINE HOUSINGSHAFT RIDER ASSEMBLYPICKUP MOUNTING STUDShaft Rider

Direct Contact : Absolute MeasurementsShaft Riders (permanently installed)Shaft Sticks or Fishtailssafety issuevery useful below coupling of vertical pumps

Vibration TransducersSensorsTransducersProbesWhat is it?.It basically converts mechanical vibration to an electrical signalAccelerometerCharge Type &Line DriveConstant Voltage &Constant CurrentVelocity ProbeDisplacementShaft Riders

Proximity Probes(Eddy Current Probes)

Accelerometers

Velocity Sensors

Displacement Probes (non-contact, eddy current probes)

Radial CasingVibrationRadial ShaftVibration & PositionAxial ShaftVibration & PositionTypical Uses of Vibration Transducers

Monitoring Techniques

Measurement ParameterFind the flattest spectrumNormally velocity is usedFor very slow running machine (< 600 RPM) displacement is preferred.For High frequency diagnostics use accelerationAlways use acceleration for Envelope analysis. AccelerationVelocityDisplacement

Monitoring TechniquesFreqVib

Easy to installGood for detecting high frequency faultsNo moving partsGood dynamic/frequency rangeSmall/light weightWithstands high temperaturesNeeds double integration to displacementNeeds external power sourceProvides limited information on shaft dynamic motionNot good for slow speed machinesMeasures directly shaft motionSame transducers for axial thrust, speed and radial vibrationMeasures directly in displacements unitsMeasures DC (shaft position)No moving partsProximity ProbesAccelerometersAdvantagesDisadvantagesRunout problemsSensitive to shaft materialsInstallationLimited freq. range. No detection of rolling element bearing faultsTemperature restrictionsExternal proximitor needed Comparison of Transducers

Frequency Range

Sensitivity vs Frequency Range

Vibration Pickups

Sensor Mounting - Frequency Range

What is the frequency range of yourInstrumentCables Sensor Sensor CouplingWhat is the fault frequency you are looking for ?Sensor freq = 12 KHzInstrument freq= 80 KHzCable length ?Sensor coupling ?Frequency Range

Types of BearingsJournal Bearings Stationary Signals Relative Low FrequencyMonitoring Techniques

Transducers and Mounting TechniquesAlthough there are many different types of transducers available, the most common type used for day to day data collection are Accelerometers.These transducers provide an electrical charge proportional to acceleration by stressing piezoelectric crystals typically 100mV/g sensors are used.

Data QualityWhether it is your job to collect the data and/or analyse the data it is important to understand that the technologies will not give you the answer to a machines problem unless you have collected meaningful, quality dataThere are certain considerations that must be taken prior to any data being collected, these are:A good understanding of the internal make up of the machine, in order to understand the best transmission path for data collection - bearing locations, load zones etc.Ensure data is collected in a repeatable manner so we can compare two or more readings to each other - trending purposesVariable speed machines - it is very important to collect data with the correct running speed enter into the analyser

Transmission PathDamaged caused to a machine component will cause a certain amount of vibration/sound or heat to propagate away from the initial impact.It is the effect of the impact/force that we are trying to detectIn many cases the further you are away from the initial event the weaker the signal will become, resulting in the data appearing to be lower in value. In more extreme cases the impact can be lost amongst other machine noise by the time it has reached your transducer, resulting in no detection of a machine problem.Usually the best place to acquire data from a machine, is at the bearings. This is because the bearings are the only part of the machine that connect the internal rotating components to the stationary components (Casing)

Repeatable DataCollect data in the same manner each time. This consistency will allow you to trend the machinery condition and properly judge the progression of faultsIn order to aid with repeatable data the analyser requests for data to be collected in certain locations on the machine. These are called Measurement PointsA measurement point is determined by three characters and a description.Each character refers to a particular place on the machine being monitoredE.g. M1H is a typical measurement point

Measurement PointsA measurement point is defined as three alpha numeric digits along with their respective definitionOrientation and location on each componentThe image on the right is taken from the screen of the 2130 analyser during a collection routeThe measurement point identifier can be seen in the top right while the point description is shown just below

Measurement PointsThe first letter of the Point Identifier refers to the type of machine being monitoredM = MotorP = PumpF = FanThe second character represented by a number indicates the location on the machineInboard (Drive End) or Outboard (Non Drive End)The third letter refers to the orientation of the sensor or the type of processing being done by the analyserH = HorizontalV = VerticalP = Peakvue Change in DSP of Analyser

Measurement PointsThe following example shows how the numbering system changes as you cross from one component to the nextNotice how the 1 is not always the Outboard This changes when the next component is required for data collection The numbering system starts from 1 againM1H Motor Outboard HorizontalM1P Motor Outboard Horizontal Peakvue

P1H Pump Inboard HorizontalP1P Pump Inboard Horizontal Peakvue

Locating Turning Speed

Turning SpeedWhen performing analysis on spectrums and waveforms, it is of utmost importance to set the turning speed (running speed) correctlyOnce the turning speed has been set, it is now possible to determine what is Synchronous/Non-synchronous and Sub-synchronous energy.When the turning speed has been located, the software will re-calculate all the frequencies to this exact speed.

Turning SpeedThe spectrum is showing numerous impacts appearing at different frequencies.By locating the turning speed, it is very clear that the impacts are Non-synchronous

Analysis Techniques TestHave a look at the spectrum below.- Where was the data taken?When the turning speed has been located - What type of energy is present?Synchronous Energy

Things to Remember about a RouteA route includes information from one area onlyA route does not have to include all the equipment defined in that areaThe order of the equipment in the route can differ from that of the databaseEquipment can appear in more than one route BUT can not appear in the same route twiceRoute measurement points may not include all the points configured on the equipmentRoute measurement points do not have to be in the same order as they appear in the databaseData is not stored at the route level but in the database with the measurement points, there for routes can be deleted but will not loose data from the databaseA maximum of 50 routes can be stored to each areaEach equipment has a maximum of 144 pointsAnd one route can only contain 1044 measurement pointsImportant: A route file contains the equipment and measurement point IDs and definitions / speeds. For this reason the route does not recognise points if their IDs are altered in the database

Frequency BandsDivide spectrum in frequency bands based on the types of mechanical faults that might appear on the machine

Frequency BandsDivide spectrum in frequency bands based on the types of mechanical faults that might appear on the machineImbalance

Frequency BandsDivide spectrum in frequency bands based on the types of mechanical faults that might appear on the machineImbalanceMisalignment

Frequency BandsDivide spectrum in frequency bands based on the types of mechanical faults that might appear on the machine

Frequency BandsDivide spectrum in frequency bands based on the types of mechanical faults that might appear on the machineImbalanceMisalignmentLoosenessBearing Band 1

Frequency BandsDivide spectrum in frequency bands based on the types of mechanical faults that might appear on the machine

Fault DiagnosticsEach type of machine fault or defect reveals a specific vibration characteristic in the spectrum and time waveform domain that distinguish that fault from another.Simply by gaining a basic knowledge of these patterns and applying a few rules of thumb we can start to analyse machine vibration and prevent machine failure.This section concentrates the characteristics / patterns and rules that apply to diagnose machine faults such as:ImbalanceMisalignmentLoosenessGearsAnti-Friction Bearings (Peakvue) Sleeve BearingsBeltsElectricalResonance

Unbalance

ImbalanceImbalance (Unbalance) occurs when the centre of mass differs from the centre of rotation.If the centre of mass changes on the rotor due to a heavy spot or some other influence then a centrifugal force is produced. This results in the centre of rotation being offset from the centre of mass causing the vibration to increase at the rotational frequency.

UnbalancePrimary TypesStatic or ForcedDynamicCoupled

Imbalance (Types)Static ImbalanceDynamic ImbalanceCouple Imbalance

Static ImbalanceThe radial vibration readings are the highest amplitudes with the axial vibration generally much lower in amplitudesStatic Imbalance will show a 0 phase shift across the rotor (vertical to vertical or horizontal to horizontal) and 90 phase shift from vertical to horizontal at the same bearing locationThe phase angle will change the same amount the heavy spot changes if the system is linear

Dynamic ImbalanceAny thing other than staticRequires more than one correction planesRule of thumbIf D/W < 4 two plan is required D = Diameter of rotor, w = width of rotorTwo unequal/equal heavy spots 180 apart in separate planes on the same rotor or located at some spacing other than 180.Amplitudes will differ or will be related to the location and amount of heavy spot

UnbalanceCauses of ImbalanceImproper AssemblyMaterial build up / dirtWear to componentsBroken or missing partsAll of the above conditions will result in an unbalanced stateDiagnostic Rules for unbalancePeriodic non-impacting sinusoidal waveformSpectral peak at 1xTs (1 Order)Very little axial vibration in case of static imbalance but high in case of overhung rotorSimilar amplitudes between horizontal and vertical plains for static imbalance and differ in case of dynamic imbalance90 phase shift from vertical to horizontalSynchronous fault typeAmplitudes will increase with speedVery low harmonics of 1xTs

Force unbalance will be in-phase and steadyAmplitude will increase with the square of speed1X RPM always present and normally dominatesCan be corrected by the placement of one weight in one planeStatic unbalance

0-180 out of phase on the same shaft for dynamic & 180 out for coupled1X RPM always present and normally dominatesAmplitude varies with square of increasing speedCan cause high axial as well as radial amplitudesBalancing requires Correction in two planesDynamic/coupled unbalance

1X RPM present in radial and axial directionsAxial readings tend to be in-phase but radial readings might be unsteadyOverhung rotors often have both force and couple unbalance each of which may require correctionOverhung Rotor unbalance

Largest vibration at 1X RPM of eccentric rotor Horizontal and vertical phase readings differ by 0 or 180Attempts to balance will cause a decrease in amplitude in one direction but an increase may occur in the other directionEccentric Rotor

Unbalance Spectral DataThe spectrum shown represents a simple unbalance state Single peak at 1xTs (1 Order)Little indication of harmonicsWhat should the waveform show?

Imbalance Waveform DataDespite the waveform being displayed in AccelerationDefault unit for route based waveform dataThere is still a predominant sinusoidal waveform pattern1 x Revolution sine waveChanging the units to velocity would reduce the amount of high frequency noise residing on the waveform

Imbalance Trend DataThe trend data is a good way of determining if there has been a change in condition, as this plots amplitude against time (where time is in days)Here the 1xTs parameter is being trendedVibration has been steady at 3mm/sec for a period of timeA sudden change instate should alert the analyst to a fault developing

Imbalance Problem - PracticalThe following fan unit has an imbalance present on the rotor.1xTs Peak in the Spectrum1xTs Peak in the WaveformWhat would happen to the data if the following occurred to the fan?

Misalignment

MisalignmentWhen two mating shafts do not share the same collinear axis then misalignment is induced.

Misalignment is one of the primary reasons for premature machine failure. The forces that are exerted on the machine and its components when in a misaligned state are greatly increased from normal operating conditions

MisalignmentOperational Deflection Shape (ODS) is a technique that machine movement based upon the phase and magnitude of data collected from the analyser. Shown below is an image from the ODS illustrating the forces that are exerted onto the machine and components when running in a misaligned condition

MisalignmentMisalignment can be broken into three basic categories, these are:Angular Where the shaft centrelines cross producing a 1xTs peak axially Offset Where the shaft centrelines are parallel but they do not meet producing a radial 2xTs peakMore commonly seen A combination of the above

Misalignment

MisalignmentAnother common problem associated with alignment is bearing misalignment.Bearing misalignment occurs when the bearings are not mounted in the same plain possibly due to: one or more of the bearings being cocked in the housingThe machine itself distorts due to thermal growth or soft foot conditions Misalignment at the drive causes shaft bending.

MisalignmentDiagnostic Rules for MisalignmentHigh axial levels of vibration at 1xTs(often .5-2 times the radial readings)High radial levels of vibration at1xTs and/or 2xTs, 3x & 4x may also be presentRepeatable period sine waveform showing 1, 2,3,4 clear peaks per revolution (Most likely M or W shape)Data can usually be seen across the couplingPhase reading will differ by 180 in axial or radial directionsOther visual observations may also be present like:Excessive bearing temperatureOil Leakage around the sealsCoupling worn /wear

Diagnostic Rules for Bearing MisalignmentHigh levels of vibration at 1xTs and 2xTsRepeatable periodic sine waveform showing 1 or 2 clear peaks per revolutionData usually shown either the driver or driven component

Offset Misalignment Spectral DataThe spectral data shown represents a simple misalignment plot. The primary cursor denotes the 1xTs peak while the harmonic cursors indicate a larger 2xTs peak. This type of data is common to that of Offset Misalignment

Angular Misalignment Spectral DataThe spectral data below represents a simple misalignment plot. The primary cursor denotes the 1xTs peak while the data was taken in the axial direction. This type of data is common to that of Angular Misalignment

Offset Misalignment Waveform DataThe waveform above is showing two clear peaks per revolution of the shaft. This type of waveform resembling an M or W shape is common to offset misalignment. Data shown in velocity

MisalignmentThe waveform data shown above is predominantly showing one sinusoidal waveform per revolution of the shaft. Here the data is shown Acceleration

Characterized by high axial vibration180 phase change across the couplingTypically high 1 and 2 times axial vibrationNot unusual for 1, 2 or 3X RPM to dominateSymptoms could indicate coupling problems Angular Misalignment

High radial vibration 1800 out of phaseSevere conditions give higher harmonics2X RPM often larger than 1X RPMSimilar symptoms to angular misalignmentCoupling design can influence spectrum shape and amplitudeRadial1x2x4xParallel Misalignment

Bent shaft problems cause high axial vibration1X RPM dominant if bend is near shaft center2X RPM dominant if bend is near shaft endsPhase difference in the axial direction will tend towards 180 differenceBent Shaft

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 180 phase shift side to side or top to bottom Bearing Misalignment

Looseness

How would looseness ?

LoosenessLooseness can be broken down into two main categories, Structural and ComponentStructural looseness occurs when there is free movement within the machines support structure causing excessive vibration. This can be a result of:Loose support bolts to the components feet and supportsCracked weldsDeterioration of the base itself.Component looseness generally occurs when there is excessive clearance to the components within the machine, such as:Excessive clearance between the shaft and bearingsExcessive clearance between the shaft and an impeller etc.

LoosenessDiagnostic Rules for LoosenessMultiple harmonics of the 0.5xTs and/or 1xTs peak - StructuralMultiple Harmonics of the component that is loose - ComponentNumber of harmonics will increase as the looseness progressesRandom, non-periodic waveform - StructuralWaveform shows predominant impacts ComponentMay also truncation in the waveformPhase varies and unsteadyRaised noise level around the 1xTs + harmonicsHalf harmonics may also be presentCan be present in all Directions but often high in vertical direction

Looseness Spectral Data (Structural)The spectral plot shown is demonstrating Looseness. The 1xTs peak has been highlighted by the primary cursor and the relevant harmonics have been displayed.Multiple harmonics of 1xTs are shown up to around 10 orders of 1xTs.

Looseness Spectral Data (Component)The spectral plot shown is demonstrating rotational Looseness. The primary cursor is on 5xTs peakThe 5 Order peak is vane pass frequency (5 vanes on the impeller)Multiple harmonics of 5xTs are shown indicating the impeller has come loose. The raised noise level around the vane pass frequency is common to a pumping problem known as CavitationThis would be the likely cause of the impeller problem

Looseness Waveform DataHere the waveform is demonstrating a lot of energy and appears to be more random and non-periodic.Displaying the waveform in velocity may help to show the random non-periodic pattern.

Looseness Trend DataHere the trend plot is showing the parameter labelled as the 3-15xTs. This is measuring the amount of energy from 3 orders to 15 orders, which is where the harmonics of looseness will appear.

Caused by structural looseness of machine feetDistortion of the base will cause soft foot problemsPhase analysis will reveal aprox 180 phase shift in the vertical direction between the base plate components of the machineMechanical Looseness

Caused by loose pillow block boltsCan cause 0.5, 1, 2 and 3X RPMSometimes caused by cracked frame structure or bearing blockMechanical Looseness

Phase is often unstableWill have many harmonicsCan be caused by a loose bearing liner, excessive bearing clearance or a loose impeller on a shaftMechanical Looseness

Similar spectrum to mechanical loosenessUsually generates a series of frequencies which may excite natural frequenciesSub harmonic frequencies may be presentRub may be partial or through a complete revolution.Rotor Rub

Gear Boxes

Gear DefectsThere are many different types of gears and gear combinations available for various speed and power requirements.Regardless of gear type they all produce the same basic vibration patterns and characteristics when a defect is presentThe following topic will discuss the basic characteristics for the following types of gears:Spur GearsHelical GearsBevel Gears

Spur GearsSpur Gears are most commonly thought of when diagnosing gears. The teeth are cut parallel to the shaft. These gears are good at power transmission and speed changes but are noisier than other gear types. Spur Gear AdvantagesHigh efficiencyLow heat generationSpur Gear DisadvantagesCan be very noisy

Helical GearsHelical Gears have teeth cut at an angle to the shaft. These gears are much quieter than spur gears but due to the angular nature of the gear meshing, axial thrust and therefore axial vibration is higher than those of spur gearsSometimes to counter act the axial thrust these gears can be double up and are known as Double Helical or Wishbone GearsHelical Gear AdvantagesQuiet OperationHelical Gear DisadvantagesLess power transmission efficiency and greater heat generation than spur gearsAxial loading on bearings

Bevel GearsBevel Gears are used to transmit power and speed to an output shaft perpendicular to the drive shaft. These gears use a bevel design to transmit the power better.These gears are most commonly seen on right angle gearboxes (where the input shaft is at 90 degrees to the output shaft)Bevel Gear AdvantagesConverts the direction of power transmissionBevel Gear DisadvantagesLess efficientHigher heat generation

Gear AnalysisVibration analysis of gears can provide a wealth of information about the mechanical health of the gears. This section discusses the basic frequencies that may be present within a gearbox. Gear Mesh Frequency Spectral DataThe gear mesh frequency (GMF) refers to the frequency at which to mating gears interact with each other and is the most commonly discussed gear frequency.However, GMF by itself is not a defect frequency. The GMF should always be present in the spectral data regardless of gear condition. What is important is the amplitude as this may vary depending upon gear condition or loading of the gear.

GearsTwo mating gears will generate a frequency known as the GMF and will show in the spectral data regardless of gear condition.

Calculating GMF Single ReductionSingle Reduction Gear TrainThe GMF is simply defined as the number of teeth on a gear multiplied by its turning speedGMF = (#teeth) x (Turning speed)Example:Consider the following gear train,GMF = #teeth x turning speed

GMF = 44teeth x 1490 RPM

GMF = 65560 CPMor 65560/60 = 1092.6 Hz

Calculating GMF Multi ReductionCalculating the GMF for gearboxes that have multiple trains use the following. GMF = (#teeth) x (Turning speed)Gear Ratio = (#teeth in) / (#teeth out)Speed out = (Speed in) x (Gear Ratio)Example:Consider the following gear train:

Calculating GMF Multi Reduction

GMF Calculation ExerciseCalculate Speeds of all shaftsAll GMF from the following gearbox arrangementGear Ratio 1 = 10/40= 0.25Shaft 2 speed = 1000 x 0.25= 250 RPMGear Ratio 2= 10/20= 0.5Shaft 3 Speed= 250 x 0.5= 125 RPMGMF 1 = 1000 x 10= 10000 CPMGMF 2= 250 x 10= 2500 CPM

Gears Sideband FrequenciesSidebands are the most common indication that a gear is defected.Sidebands are equally spaced frequencies in the spectral data that materialise either side of the main GMF peak.The sideband frequency spacing is equal to either the turning speed of the input gear or the turning speed of the output gear.Sidebands show in the data when either the gear is worn, loose or eccentric. The speed of the shaft with the bad gear on it will produce the most dominant sidebands in the spectral data.

GearsThe spectral data shows GMF with sideband data. The sidebands are equally spaced at intervals of 310 CPM. This is indicating the gear that rotates at 310 RPM is the one that is worn or damaged. GMFSidebands

Gears Waveform DataGears can produce different types of waveforms, the one shown below is indicating gear wear.As the defective teeth come into mesh the noise generated increases showing an increase in amplitude in the vibration data

Bearing DefectsRolling ElementPlain BearingsPeakvue

Rolling Element BearingsRolling element bearings have specific bearing failure modes that can be observed in the spectral and waveform data.Bearing frequencies differ from most other frequencies present within the spectral data because unless the bearing has a defect there will be no frequency peaks in the data relating to the bearing. Only if the bearing has a defect will frequencies show in the spectral data.There are four main fundamental bearing defect frequencies these are:

Rolling Element BearingsInner RaceOuter Race

How Bearing Faults Generate VibrationBALL SPIN (BSF)CAGE (FTF)INNER RACE (BPFI)OUTER RACE (BPFO)

FTF & BSF

BPFI & BPFO

How Bearing Faults Generate Vibration

How Bearing Faults Generate Vibration

Rolling Element BearingsBearing defect frequencies are calculated based upon the geometry of the bearing these calculations may include:Number of rolling elementsPitch Circle DiameterRolling element diameterContact angleDefined within Machinery Health Manager there are over 100000 predefined bearing stored in the CSI bearing warehouse BEARINGS in CSI Warehouse: c:\RBMsuite\SysData\CSI_CMP.WH **************************************************** BRG ID Bearing Type #B/R FTF BSF BPFO BPFI 12143 RHP 6218 11 0.418 2.967 4.598 6.402 24421 SKF 6313E 8 0.376 1.894 3.009 4.991 25372 SKF I-26313 19 0.433 3.568 8.219 10.781

Rolling Element BearingsCharacteristics of Bearing DefectsHigh frequency raised noise level (Hump of energy)Non-Synchronous harmonic peaks (Both low and high frequency)Time waveform will show a lot of noise/impacting Early stages of bearing wear may show better if viewed in acceleration in the frequency domainFundamental bearing defect frequency (First calculable frequency) may not be present in the spectral dataSidebands surrounding BPFO are much more serious than sidebands surrounding BPFI (for fixed outer race)

The appearance of defect frequencies USUALLY starts with BPFO & BPFI Followed by BSF Followed by FTFThese scenarios presume the absence of manufacturing errors on rolling element bearing components When a roller or ball defect is present from the start, BSF may well appear in the spectrum WITHOUT any progression similar to these scenarios

Frequencies Generated By REBsRandom HF to ultrasonic5KHz to 60 KHz Component Fn30KCPM to 120KCPM54K to 96K for most Defect Frequencies Sum & Difference / Sidebands

Failure Mode 1The early stages of bearing defects produce low amplitudes of vibration at higher frequencies (Appears on the right hand side of the spectrum). These are normally humps of energy or peaks that are harmonics to the fundamental frequency. (The fundamental frequency should not be visible at this stage).

Stage 1: Fault OnsetVibration Analysis (typical):Standard FFT: no visible indication in spectrumSpike Energy: slight increase in value (e.g. 0.25 gSE)PeakVue: bearing frequency peak(s) corresponding to fault type amplitude at 2-7 gs depending on type and location

Oil Analysis (typical):Readings: Slight increase in elemental Fe, particle count, and WPCVisual Ferrography: Small platelet shaped particles (

Failure Mode 2Distinct harmonics of Non-Synchronous peaks appear. (These should appear lower down the scale of the spectrum towards the left / middle of the plot)Sidebands may appear around these frequencies usually equating to turning speed. (The fault frequencies may not match exactly with the peaks in the spectrum due to the fact that the bearing geometry will have changed).

Stage 2: Intermediate WearVibration Analysis (typical):Standard FFT: bearing defect rings in Zone C (natural freq.)Spike Energy: increase in value (e.g. 0.50 gSE)PeakVue: bearing frequency peak(s) with increasing harmonics amplitude at 3-10 gs depending on type and location

Oil Analysis (typical):Readings: elemental Fe stable but increase in particle count, WPC, and PLPVisual Ferrography: Platelet shaped particles (30-50 ) from contact fatiguePossible spherical shaped particles (

Failure Mode 3The fundamental frequency normally appears at this stage (First calculable frequency of the bearing towards the left-hand side of the spectral plot). This is classed as advanced stages of bearing wear.Sidebands may be visible that equate to other bearing frequencies BSF, FTF etc).

Stage 3: Severe WearVibration Analysis (typical):Standard FFT: bearing frequencies with harmonics and sidebands in Zone BSpike Energy: increase in value (e.g. 1.0 gSE)PeakVue: bearing frequency peak(s) with increasing harmonics and sidebands amplitude climbs to 5-10 gs or higher (depending on type and location)

Oil Analysis (typical):Readings: small change in elemental Fe, substantial increase in WPC and PLP Visual Ferrography: Sharp increase in large particles (>30), both platelets and cutting wearIncreased three-dimensional appearance to wear particles

Failure Mode 4The bearing degrades so much that the spectrum becomes a mass of noise. At this point the bearing will fail at any point (If it last this long most fail around Mode 3).

Stage 4: Imminent FailureVibration Analysis (typical):Standard FFT: discrete bearing frequencies replaced by broadband noiseSpike Energy: falling levels until just before failure, then levels rise sharplyPeakVue: bearing frequency peak(s) with increasing harmonics and sidebands amplitude climbs to 10 gs or higher (depending on type and location)

Oil Analysis (typical):Readings: small change in elemental Fe, substantial increase in WPC and PLP Visual Ferrography: Broad range of huge particles (75+) from fatigue and adhesionParticle counts/ferrous density are excessive

Rolling Element Bearings - BPFITypical data showing a defected inner raceFundamental frequency showingHarmonics low and high frequency + sidebands

Rolling Element Bearings - BPFOData showing a defect related to the BPFOThe fundamental frequency is showingHarmonics from low to high frequency

Rolling Element Bearings - BSFBearing defect showing the BSF Rolling elementsSidebands around the BSF = FTF

Rolling Element Bearings - FTFThe FTF is the only bearing frequency that is sub-synchronous May not detect then with conventional vibration dataFTF defect at 0.4 orders shown in PeakvueBearing

Rolling Element Bearings - WaveformAs a bearing becomes defected then the amount of noise/force generated as the rolling elements impact the defective area increases. This can show significant G-levels in the time waveform. This value is trended in the software as the Peak-Peak value This data is taken from a pump with a damaged bearingThe force levels are reaching 40G-s

Bearing DefectsRolling ElementPlain BearingsPeakvue

Plain BearingsRotating elements are not used in sleeve (plain) bearings; rather the shaft rides on a layer of lubricating oil inside the bearing journal. Therefore the fundamental frequencies seen from antifriction bearings do not apply to sleeve bearings. Since there is no contact between the bearing and the shaft monitoring of sleeve bearings for vibration analysis usually requires the use of displacement probes mounted 45 degrees either side of top dead centre.

Plain BearingsAs there are no rotating components in the bearing that produce high frequency noise (force) there is no need to monitor a high frequency range. Usually 10 to 15 orders of turning speed will be sufficient.Sleeve bearings have specific defects that contribute towards bearing failure, these are:Excessive clearanceHydraulic instability (oil whirl)

Plain Bearings Spectral DiagnosticsExcessive ClearanceWhen there is excessive clearance between the rotor and the bearing then this will have an effect on the system vibration. When the bearings have excessive clearance then a looseness occurs.The spectral data shown below is indicating a sleeve bearing with excessive clearance.As the clearance increases then the harmonics of 1xTs will increase and can go up to 1015xTs. Like looseness the more harmonics there are the more severe the problem will be. A good sleeve bearing will still show a few harmonics as there is a small clearance between the shaft and bearing

Plain Bearings Spectral DiagnosticsOil WhirlOne of the major problems encountered with these types of bearings is the possibility of hydraulic instability of the shaft within the bearing; known as oil whirl or oil whip.Oil Whirl is a result of turbulent flow within the oil resulting in the oil pushing the shaft around of centre.The dominant peak within the spectral data will be typically at 0.4 orders. (.40-.48)This defect is sub-synchronous data. When the amplitude of the oil whirl is equal to or greater than the 1xTs peak a problem existsIn this instance oil whirl can be corrected by:Properly loading the bearingChange the oil viscosityChange the oil pressure

Plain Bearings Spectral Diagnostics

Usually occurs at 42 - 48 % of running speedVibration amplitudes are sometimes severeWhirl is inherently unstable, since it increases centrifugal forces therefore increasing whirl forcesOil 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 shaft.Whirl speed will lock onto rotor critical. If the speed is increased the whip frequency will not increase. Oil Whip Instability

Bearing DefectsRolling ElementPlain BearingsPeakvue

Peakvue

What is PeakvueWhat is Peakvue?Peakvue is a technology unique to CSI and means Peak ValueSuch as the Peak Value of an impact generated by a bearing defect in a time waveform - (True Peak Value)If you have a 21XX analyzer you have the capability to acquire Peakvue Data

These stress waves travel further than conventional vibration signals so a truer indication of fault severity is obtained.The True Peak Value is obtained by concentrating on Stress Wave Analysis rather than conventional vibration data.

What is PeakvueWhat is a Stress Wave?

Stress waves accompany metal-metal impacting. These stress waves are short-term (fractional to a few milliseconds) transient events, which introduce a ripple effect on the surface machinery as they propagate away from the initial event. If you think of a stone being dropped into a pool of water. The stone is the initial impact generated by the fault. The effect of the stone being dropped into the water cause a ripple on the surface of the water which, spreads over a wide area.

What is PeakvueIf a bearing has a sub-surface defect (early bearing wear), when a rolling element passes over the defect it bends the race slightly and then as the rolling element passes it restores back to its natural state.This event causes a high frequency (1-50KHz) short duration stress wave.

Peakvue ProcessingThe detection of bearing and gear defects is one of the primary expectations of a predictive maintenance program. As analysts we can spend a lot of time tying to determine these faults. Peakvue is a process that concentrates on these defects to help the analysts determine potential faults developing Peakvue stands for the Peak Value and is a technique that detects high frequency stress waves generated from metal to metal contact, such as:Bearing defects Rotating elements striking a defect on the raceGear defects Damaged teeth in meshIt is the detection of these high frequency stress waves that will aid with analysis

Peakvue Processing - FiltersIn order to capture the stress wave signal the process requires the use of a filter to remove all unwanted noise that can dominate the data

Peakvue Processing - FiltersThere are two types of filters availableBand Pass FiltersThe band pass filter removes all the data above and below the filter corner valuesHigh Pass FilterThe high pass filter removes all data lower in frequency to that of the filter selection allowing only the high frequency stress waves to pass throughAfter the filtering process what should remain is the high frequency stress wave activity that is occurring at the rate of the excitation such as from a bearing.

How Does It Work? A comparison can be made of the sampling to show how data is collected through both methods of data acquisition, normal and Peakvue.

FFT

HighPassFilterFull Wave RectifyDigitalPeakImpactDetectionVibration Signal

How Does It Work?The diagram below shows sampling of data using normal data collection.Stress wave- this is missed under normal conditionsInstantaneous Samples

How Does It Work?The diagram below shows sampling of data using Peakvue data collection.Stress wave- this is missed under normal conditions

How Does It Work?Peakvue measures the highest amplitude found in a stress waves (Pk Value) and holds that dataThe waveform data is then passed through a high pass filter to remove the unwanted, low frequenciesImbalance, Misalignment, Looseness, resonance etc.This just leaves us with the high frequency impacting data (Peak) above the machine noise levelThe data is then brought back to fundamental frequency. (this allows analysis of the data to be done quicker and easier)

PeakVue How does it work?The waveform should contain enough time to include at least 15 shaft revolutions to resolve cage frequency in the spectrum for rolling element bearings.

(The waveform time length is determined by the lines of resolution divided by the f-max)

PeakVue How does it work?The f-max should be set at least 3 or 4 times the highest expected defect frequency (usually inner race defect for rolling element bearings)

One average should be used when taking PeakVue data

PeakVue How does it work?Transducer mounting should be consistent for trend able data.

At minimum the surface should be clean (free of paint, dirt, etc.), stress waves are easily attenuated.

FiltersTypes of filter availableFilter CalculationsFilter Guidelines

Selecting the wrong type of filter will result in poor quality dataTo much noise filtered through (the spectrum becomes very noisy)To much is filtered out (The stress wave is not allowed to pass through)Filters OptionsThere are two types of filter options in Peakvue, these are:1. Band Pass Filter2. High Pass FilterEach of the filters are designed to remove unwanted data out of the signal at the appropriate levelsOne of the key elements in acquiring meaningful peakvue data is the selection of filters

Filter Options - High Pass FilterHigh Pass Filters remove all frequencies from the data below the filter setting but allow the high frequency stress wave to pass through.

Filter Options - Band Pass FiltersLooks for stress waves within a parameter defined by the filter setting. Frequencies above and below this setting are removed from the data

Filter SelectionTo select the correct filter we need to consider the highest operational defect frequency that we want to measure/detect. Then select the next available filter above that frequency

E.g. Consider a typical motor / pump arrangement. We have:1 - 4 Pole A.C. Induction Motor2 - 3 Jaw Coupling3 - Centrifugal PumpTypically the highest defect frequency to emit from this machine would be?1 - BPFI - Bearing Defect

Filter Selection4 Pole Motor A.C Induction fitted with bearings SKF 6313Defect Frequencies (Orders)FTF - 0.384BSF - 2.037BPFO - 3.071BPFI - 4.929Typically we would want to see the 10th Harmonic of the BPFIHighest defect frequency:(BPFI x 10) x Turning Speed (Hz)(4.929 x 10) x 251232.3 HzWe would then select the next available filter setting above the frequency

Available filtersHigh Pass Filters500hz1000hz2000hz5000hz10000hz20000hzBand Pass Filters20hz 150hz50hz 300hz100hz 600hz500hz 1khzNote: the meter will only allow you to select the next filter above the specified Fmax.From our previous calculation of 1232Hz, What filter setting would we select?

Filter uses (Band Pass) - Guidelines Band Pass Filters20hz 150hz Felt problems on paper machines50hz 300hz Certain structural resonance excitation, modulation of gearmesh in low speed machinery100hz 600hz Gearmesh modulation in intermediate speed machinery.500hz 1khz Gearmesh modulationTip: use bandpass filters when the event of interest is the excitation of a structural resonance, or the modulation of known frequencies such as gearmesh.

Filter uses (Highpass) - guidelinesHigh Pass filters500hz Low speed machinery having

Filter Selection - QuestionConsider:Motor running at a speed of 1000RPMDriving a fan unit via pulley beltsFan Speed is 1350RPMMotor Bearings = SKF 3095 - BPFI 4.855Fan Bearings = SKF 6210 - BPFI 5.907Calculate what Filter setting would be required for both the motor and the fan bearings? Filters Available:500 Hz, 1000Hz, 2000Hz, 5000Hz, 10000Hz, 20000Hz. (High Pass)20-150Hz, 50-300Hz, 100-600Hz, 500-1KHz. (Band Pass)

Filter Selection - AnswersMotor Speed = 1000CPM / 60 = 16.667HzFan Speed = 1350CPM / 60 = 22.5HzMotor.BPFI = 4.855Defect Frequency = (BPFI x 10) x Turning Speed (Hz)Defect Frequency = (4.855 x 10) x 16.667Defect Frequency = 809.18 HzFilters Available:500 Hz, 1000Hz, 2000Hz, 5000Hz, 10000Hz, 20000Hz. (High Pass)20-150Hz, 50-300Hz, 100-600Hz, 500-1KHz. (Band Pass)1000Hz

Filter Selection - AnswersMotor Speed = 1000CPM / 60 = 16.667HzFan Speed = 1350CPM / 60 = 22.5HzFanBPFI = 5.907Defect Frequency = (BPFI x 10) x Turning Speed (Hz)Defect Frequency = (5.907 x 10) x 22.5Defect Frequency = 1329.07HzFilters Available:500 Hz, 1000Hz, 2000Hz, 5000Hz, 10000Hz, 20000Hz. (High Pass)20-150Hz, 50-300Hz, 100-600Hz, 500-1KHz. (Band Pass)2000Hz

Peakvue DataSpectrums and WaveformsDiagnostics Techniques

Peakvue - SpectrumHere is a typical Peakvue spectra plot. This is typically a GOOD spectrum

Peakvue - SpectrumThis is a Peakvue spectrum where high frequency stress waves are being detectedThis is indication of a fault developing

Peakvue Processing Spectral DataShown below is a typical Peakvue spectrum with a defect presentThe filter used is shown in the top right hand cornerStress waves are showing clearly in the data at 4.6 OrdersNoise removed by filterGood Spectrum will show only a noise level

Peakvue Processing Waveform DataAs stress waves are small in amplitude severity of the problem can be judged using the time waveformPeak Value of force from the impactThe waveform can resemble a spectrum as there is no negative half to the dataFor Peakvue analysisUse the SpectrumDiagnose the defectUse the Waveform Determine the severity

Peakvue - WaveformsWaveforms can be confused with spectrums, as the waveform is only plotting the peak value and does not show a full wave.

Peakvue - DiagnosticsDiagnosing a Peakvue spectrum and waveform is not to dissimilar to that of conventional data. However there are a few differences which can be a bit confusing at first, these are:1. Do not try to locate 1xTurning Speed, as this is low frequency data and will be filtered out.Turning speed should be entered using the conventional spectral data. 2. Multiple harmonics are often present within a spectrum due to the way peakvue samples the data.These do not indicate Looseness 3. Spectral amplitudes are always low in amplitude but should not be used to judge severity. Use the spectrum to diagnose the fault.4. Waveforms indicate the severity of the problem.

Peakvue - DiagnosticsContinued..5. Ensure the same filter setting is used in both the spectrum and waveform.Potential faults can be missed or overlooked if different filters are used.6. Cage Defects show up well in peakvue data and is normally an indication the bearing is under stress.7. All low frequency faults are removed from the data and will not be seen in a Peakvue spectrum and waveformImbalance, Misalignment, Looseness, Resonance - All Gone.

Peakvue - Diagnostics

Peakvue - Diagnostics

Peakvue Amplitudes - Rolling Element BearingsFor machines running between speeds of 900 - 3600RPM recommended guidelines for setting initial warning levels in the Peakvue time - waveform are as follows:

Chart1

3.57

2.6255.25

1.968753.9375

1.47656252.953125

1.1074218752.21484375

0.83056640621.6611328125

0.62292480471.2458496094

0.46719360350.934387207

0.35039520260.7007904053

0.2627964020.525592804

0.19709730150.394194603

0.14782297610.2956459522

&A

Page &P

Inner race - Amplitude (g's)

Outer race - Amplitude (g's)

Sheet1

Inner race - Amplitude (g's)Outer race - Amplitude (g's)RPM

3.57.0900

2.65.3800

2.03.9700

1.53.0600

1.12.2500

0.81.7400

0.61.2300

0.50.9200

0.40.7100

0.30.575

0.20.435

0.10.310

Sheet2

Alert ValueFault Value

Inner Race3.0g's6.0g's

Outer Race6.0g's12.0g's

Rolling elements fault4.5g's9.0g's

Cage frequenciesIf evident then the bearing is usually under stress.

Sheet3

Peakvue Amplitudes - Rolling Element BearingsFor machines running at speeds

Peakvue Vs Demodulation

Peakvue Vs DemodulationWhat is Demodulation?This is a technique which concentrates on stress wave analysis, but is not as effective. How Does it Work?Demodulation looks for the ringdown that follows an impact, and tries to measure how quickly it fades. In order to do this the Time Waveform has to be manipulated in such away that the waveform data becomes useless

Peakvue Vs DemodulationWhat are the Differences?Peakvue samples the data much quicker enabling it to catch the very short duration high frequency stress wave. It then holds that Peak Value throughout its parameter.Due to the Analogue filtering system used by Demodulation, results in a delay in response and the stress wave impact is missed

Peakvue Vs DemodulationThe Process!

Peakvue Vs DemodulationEquipmentA conveyor system consisting of six rolls is driven by a motor/gearbox unit .The motor speed is 1500RPM reduced through the gearbox giving the roller speed to be 98.5RPM

Peakvue Vs DemodulationData was collected on each bearing of the conveyor systemDue to the slow speeds Peakvue and Demodulation Filters were both set to 500Hz High Pass using 1600 Lines of Resolution

Peakvue Vs Demodulation

Electrical Defects

Electrical DefectsA motor can be simply broken down into two key componentsRotor StatorThe stator is stationaryConsists of wire wound in coils and placed in slots of an iron core. The stator produces a rotating magnetic field.The rotor is not stationaryConsists laminations with solid conductors called rotor barsA circular flow of current through these rotor bars causes the rotor to become an electromagnet which will rotate in a magnetic filed.

Electrical Defects Spectral DataThe most common electrical frequency that materialises in the spectral data is the 2 x Line Frequency.For most industrial applications the line frequency used to supply motors is 50Hz (Europe). Therefore the frequency of concern for most electrical faults would be 100Hz (2xLf [Lf=line frequency]) The spectral plot is showing a peak at 100Hz (6000cpm)2xLfThis can be mistaken for misalignment

Electrical Defects Waveform DataThe waveform data from a 100Hz peak will show a sinusoidal pattern like the waveform shown below Again this type of pattern can be associated with misalignment. Usually misalignment would produce higher force (Higher waveform levels) than those from electrical defects due to the stress being applied to the machine

Electrical Defects - CausesCommon fault types that can produce the 2xLf peak are as follows:Dynamic Eccentricity Usually Rotor RelatedStatic Eccentricity Usually Stator RelatedLoose Iron or Slot Defect Rotor or StatorOpen or Shorted Windings Insulation Breakdown or Imbalanced PhaseLoose Connectors

Electrical Defects - PeakvuePeakvue data also shows electrical defects at the 2xLf peak. This may be due to the rotor or stator bowing; due to heat build up.The spectral plot below is indicating a 100Hz peak using Peakvue with a 1000Hz filter.

Belt DefectsV-BeltsTiming Belts

Belt DefectsBelts are the most common low cost way to transmit power from one shaft to another. Belt drives rely on friction between the belt and pulley to transmit power between drive and driven shaftsThe ability of belt to transmit power depends uponBelt Tension (tension on the belt holds it tightly against the sheave)Friction between the belt and sheaveThe arc of contact between the belt and sheave (Wrap)The speed of the beltHowever, belts can be easily damaged by heat, oil and grease and since belts slip with in the sheaves they can not be used where exact speed changes are required (except for timing belts)

Belt DefectsBelt defects can be considered non-critical faults by many maintenance groups due to the relative ease of replacement requiring minimum downtime. But belt defects are a major contributor to the overall vibration of the machine resulting in premature failure of other machine components.Sources of belt drive defects

Belt Defects Belt TypesThere are many different types of belt drive systems. This section covers the most commonly used types of belt in industry today.V-BeltsV-belts are the most common type of belts used. They are V shaped in cross-section, this allowing the belt to wedge against the side of the sheave. This design allows the belt to be run faster than most other type of belt applications with power transmission efficiencies as high as 95%

Belt DefectsTiming BeltsThese are flat belts with equally spaced teeth that mesh with notches on the pulley. Timing belts are different from other belt drives as they do not induce any slip. Most commonly used where constant velocity and strict timing application is required.

Belt Defects Fault CharacteristicsBelt defects, such as cracks, broken or missing pieces, hard and soft spots can generate vibration at the turning speed of the belt (1xbelt) and harmonics Due to the length of the belt in relation to the pulleys (sheaves) the 1xbelt frequency is sub-synchronous and very often the 2xbelt frequency may be sub-synchronous as wellThe predominant harmonic is typically the 2xBelt frequency and can be seen in the radial plain in-line with the belts.Severity is judged by the number and amplitude of the harmonics seen in the spectral data

Belt Defects Fault CharacteristicsJust like two mating shafts, belt drive systems can also be misaligned in both angular and offset directions. When misalignment is induced into a belt drive system then the life of the belt is significantly reduced as well as the overall vibration of the system increases.Pulley misalignment results in high axial vibration at the shaft turning speed. If the belt is also defected then 1xbelt frequency and harmonics may also show in the axial direction

Belt Defects Calculations The fundamental belt frequency can be calculated using the following equation:Belt Freq. = (3.142 * Pulley Ts * Pulley PCD) Belt (Length)Where:Ts = Turning SpeedPCD = Pitch Circle DiameterNote: The PCD and belt length must be in the same unitsA timing will belt will also have a specific frequency related to the number of teeth on the pulleyTiming Belt Freq. = (Pulley Ts) * (# Pulley Teeth)

Belt Defects Calculation ExampleBelt Frequency CalculationBelt Frequency = (3.142 * 1480 * 300) / (2000)Belt Frequency = (1395048) / (2000)Belt Frequency = 697.524 CPM This is sub-synchronous to the 1xTs of the pulleyMotor RPM = 1480 RPMPulley Diameter = 300 mmBelt Length = 2000mm

Belt Defects Spectral DataThe spectral data above is data taken of a motor from an Air Handling Unit. The frequency highlighted by the primary cursor is showing the 1xTs of the motor (1 Order) There are a lot of sub-synchronous peaks showing in this data. The first peak is the fundamental frequency of the belt rotation. The second peak is the 2xbelt frequency suggesting there is damage to the beltAs the harmonics of the belt increase in number they surpass the 1xTs of the motor and in this case the third harmonic becomes non-synchronous data. 1 x Belt Frequency showing with harmonics

Dominant 2 x Belt Frequency

Resonance

ResonanceResonance is defined as:An excitation of a natural frequency by a periodic forcing function.

All assets contain natural frequencies that vary depending upon the stiffness and mass. Resonance can be considered to be a vibration amplifier, that takes the force level of the periodic forcing function and amplifies it; which significantly increases the movement of the asset.

If Vibration is a Fire, The Resonance is a Fuel

Example of ResonanceThe example shown represents the effect on amplitude of the forcing function when in resonance.In plot 1 the 1xts is running below the natural frequency (Fn). Fn can be seen in plot 2. Plot 3 shows the increase in amplitude of the forcing function when run at the natural frequency this is resonance

ResonanceThere are two factors that determine the natural frequency of an asset these are;Mass The heavier an object the lower the natural frequencyStiffness The more rigid a structure the higher the natural frequency

Resonance is becoming more of a problem in industry in recent years due to:Older equipment having to run faster to meet current production demands (often above what it was designed for)Equipment is being built cheaper and lighterThis is resulting in amplification of the forcing function creating excessive machine movement resulting premature machine failure.

Effects of ResonanceThe ODS data is showing a steel frame structure deflecting at one corner in the vertical direction due to a resonant condition.

Characteristics of ResonanceCharacteristics of ResonanceResonance is very directional in nature (Movement may be greater in one plain than the other)Vastly different amplitudes of the forcing function from one direction to the other (between Horizontal and Vertical Rule of thumb ratio is 3:1 difference)Resonance is very speed sensitive (small changes in speed can show large differences in amplitude of the forcing function)Resonance can occur at any frequency but most commonly associated with the 1xTs180 phase change occurs when shaft speed passes through resonance

Resolving a ResonanceThere are a number of alterations to the system that can be made to resolve a resonance condition. However if structural changes are to be made you need to be careful you dont excite another natural frequency once the change has been made?Once you are sure you have a resonant condition it can be corrected by one of the following methods:Change the MassChange the StiffnessRemove the forcing functionDampen the structureDampening is a method used to convert mechanical energy into thermal energy. It does not remove the resonant condition only controls the amount of movement.

Resonance Spectral DataThe spectrum is showing the 1xTs peak of the motor with amplitudes reaching 19mm/sec. This is high for the 1xTs.Very often this type of data can be mistaken for Imbalance as this defect can also produce a high 1xTs peak. However Imbalance is a centrifugal force and should show similar amplitudes in both radial plains where as resonance is very directional.

In order to help resolve this issue we need to check the amplitude of the 1xTs 90 degrees to this point (horizontal to vertical) This can easily be done by using the multi point plot in the software

Resonance Multi PlotThe multi point plot allows the analyst to display several measurement points on the same plot. Here we are showing all the radial points from the motor.It is very clear that the amplitudes of the 1xTs peak are excessive in the horizontal direction when compared to the vertical. This is a characteristic of a resonant condition.

Rotary Pumps , Fans & Compressors Analysis

Cavitation will generate random, high frequency broadband energy superimposed with VPF harmonicsNormally indicates inadequate suction pressureErosion of impeller vanes and pump casings may occur if left uncheckedSounds like gravel passing through pumpCAVITATIONHydraulic and Aerodynamic Forces

If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitudeHigh VPF may be present if impeller wear ring seizes on shaftEccentric rotor can cause amplitude at VPF to be excessiveHydraulic and Aerodynamic Forces

Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ductsRandom low frequency vibration will be generated, possibly in the 50 - 2000 CPM rangeFLOW TURBULENCEHydraulic and Aerodynamic Forces

Surge can occur if the pressure developed by the compressor is not equal to or greater than the downstream pressure Random low frequency vibration will be generated, possibly at 30-45 % of compressor of compressor speedSURGEHydraulic and Aerodynamic Forces

Digital Signal Processing

Digital Signal ProcessingSignal Integration ModeAnalogAnalog integration integrates data in the time domain as collected , then performs FFT.DigitalPerforms the FFT first then integrates in the frequency domain

Raw SignalAmp

ACOutputIntegrator1x, 2xHigh PassFilterLow PassFilterDCOutputAmp

DetectorP-P or RMSDisplayReadingAccelerometerThe Vibration Meter

Machine Vibration SignalDigital Signal Processing

Time SignalAbsolute Vibration with Free-SpaceMachine Vibration Signal

AC SignalDC SignalRelative Vibration with mounting position of Prox. ProbeMachine Vibration Signal

PeakPeaktoPeakRMSAvgAlways ask.... Are you measuring RMS or Peak , etc ?? What is the frequency range ?? How much averaging?Freq. = 1/TimeFreq. = Hz= rev. per second

Machine Freq are function of RPMie. rev. per minuteBandpass Measurement

RMSTrue peak - peakFor Sine waves only:aT = averaging periodRMSDetector

Stationary Signals- Vibration from rotating machines- Vibration from reciprocating machines (short term)

- Vibration from run-ups and coast-downMachine Signal Types

How to make a frequency analysis?Frequency analysis can be made using frequency selective devices called filtersAn ideal filter will only signals to pass within its bandwidthfdBf2f1fcBB = BandwidthIn FFT analysis, the bandwidth = Frequency span / no. linesFrequency Analysis

High-Pass filters - As the name imply, a high pass filter allows high frequencies to pass. (lower frequency limit)

Low-Pass filters - Allow low frequencies to pass through (upper limit)

Bandpass filters - Allows only frequencies within the band

Anti-aliasing filters - Low pass filter at half the sampling frequenciesTypes of filters:Frequency Analysis

Frequency Range Selection?

BW = Fmax /LOR*BW, bandwidth ,the spacing between each lineThe bandwidth shoul not be no greater than 5Hz or 300CPM Time to Collect one average (sample time) = 1/BW Tmax (Time waveform length) = Sample size / Sample rate Where sample size = 2.56*LOR & sample rate = 2.56*Fmax

Discrete Fourier TransformThe signal that comes to the analyzer is analog signal. It must be digitally sampled by the analyzer. This process is a variation of FFT and is known as DFT.For DFT the waveform is re-created in the analyzer by digitally sampling and then transformed into the frequency domain.To under stand the FFT digital sampling process ,we must have the under standing of:L.O.RFmaxLength of WaveformDigital Sample Size

Discrete Fourier Transform (DFT) - PitfallsFFT - Fast Fourier Transform is an efficient means of calculating a DFT (Discrete Fourier Transform). Basically, it transform a time signal into a frequency spectrum.Aliasing - high frequencies appearing as low frequencies

Leakage - Memory contents forced to be periodic. Can give discontinuities when ends joined

Picket fence effect Actual spectrum sampled at discrete frequencies. Peaks may be missingFFT (DFT) - Pitfalls

Sampling rate too slow

High frequency analysis results in false low frequency signalSolution: Use Anti-aliasing filterTypically a 1K (1024 point) transform, 512 frequency components are calculatedand 400 lines displayed. Similarly a 2K transform 800 lines are displayed.FFT pitfalls - Aliasing Effect

1st Sample2nd Sample-ve-ve+ve+ve..give discontinuities when ends joinedFFT pitfalls - Leakage

ActualSpectrumMeasuredSpectrumFFT - Picket Fence Effect

min. analysis time must allowthe measured freq. to complete its cycle / periodTFreq. = 1/TimeBT > 1Bandwidth Measurement TimeFFT Analysis Time

Harmonic signals can be measured in short timeRandom and Pulsed signals need longer timeFor FFT spectra C = 1 pr. average. B * T = CB = Highest resolution of AnalysisT = The Shortest measurement timeC = Constant.TheoreticalC = 3 for Harmonic SignalsC = 30 For Random SignalsIn PracticeC = 5 for Harmonic SignalsC = 100 For Random SignalsMeasurement Time

T1T2T3T1 > T2 > T3 therefore low freq. analysis always take a longer time than high freq analysislow freq.mid. freq.high freq.FFT Analysis Time

Example: 1 KHz Freq. Span AnalysisMore FFT Lines gives Higher ResolutionBUTAlso takes more time & memory spaceDO WE NEED SUCH A HIGH RESOUTION?CAN OUR HUMAN MIND HANDLE SUCH HIGH RESOLUTION?FFT Analysis Time

Waveforms

WaveformsJust like the spectral there are certain patterns and characteristics to look for when conducting waveform analysis.Once the characteristics have been identified, the analyst can rule out certain faults e.g: if the waveform is periodic faults like Looseness, Bearing defects, Cracks could be ruled out. Some Characteristics are: 1.Amplitude 2.Periodic 3.Impacts 4.Discontinuities 5.Asymmetry 6.Modulation 7.Restrictions

Waveform AnalysisTime - seconds

Waveform AnalysisPeriodicity

Waveform AnalysisPeriodicity

Waveform AnalysisAsymmetry

Waveform AnalysisImpacting

Waveform AnalysisDistortion

Vibration AnalysisComplex

Waveform AnalysisElectrical vs Mechanical

Waveform AnalysisNoise

Waveform AnalysisExtended time

Waveform AnalysisExtended time

Waveform AnalysisLow frequency

A beat is the result of two closely spaced frequencies going into and out of phaseThe wideband spectrum will show one peak pulsating up and downThe difference between the peaks is the beat frequency which itself will be present in the wideband spectrumWaveform - Beats

Crest FactorIntroduction The Crest Factor is equal to the peak amplitude of a waveform divided by the RMS value. The purpose of the crest factor calculation is to give an analyst a quick idea of how much impacting is occurring in a waveform. Impacting is often associated with roller bearing wear, Cavitation and gear tooth wear.

In a perfect sine wave, with an amplitude of 1, the RMS value is equal to .707, and the crest factor is then equal to 1.41. A perfect sine wave contains no impacting and therefore crest factors with a value higher than 1.41 imply that there is some degree of impacting

Crest FactorThe Problem with the Fast Fourier Transform (FFT) The definition of the Fast Fourier Transform implies that any signal can be approximated by the sum of a set of sine waves. Unfortunately, this doesnt work so well when one has a signal that consists of non-periodic events, impacts or random noise . Both impacts and random noise appear the same in the spectrum although they mean different things in the context of machinery vibration analysis. The crest factor is therefore useful in giving the analyst a quick idea of what is occurring in the time waveform.

Crest FactorComparison of 2 Waveforms In below figures we can see an example of the use of the Crest Factor. The waveform in figure on left has a crest factor of 3.01. The waveform in figure on right has a crest factor of 1.61. The data in figure on left represents a machine with serious rolling element bearing wear, and the crest factor is relatively high due to the amount of impacting occurring within the bearing. The data in figure on right represents a machine with an unbalance, but no impacting related to bearing wear.

Crest FactorConclusion The Crest Factor is a quick and useful calculation that gives the analyst an idea of how much impacting is occurring in a time waveform. This is useful information that is lost if one is only viewing a spectrum as the FFT cannot differentiate between impacting and random noise. Impacting in a time waveform may indicate rolling element bearing wear, gear tooth wear or Cavitation. Quite often, the Crest Factor is trended over time in order to see if the amount of impacting is increasing or not.

Advance Analysis

Rotor Dynamics Terminology & Introduction

Types of bearingsStandard Tilting Pad Bearing groovedellipticalTilting Pad

Turbine Supervisory InstrumentationHP TurbineLP TurbineGeneratorExciterA typical 250MW Steam Turbine

Turbine Supervisory InstrumentationTypical TSI Configuration for a Large Steam TurbineProx. Probe

Instrumentation, Measurement TypesThrustEccentricityCase expansionDifferential expansionRadial vibrationSpeedPhaseTemperatureValve position

ThrustThrust is a position measurement, and is one of the most critical measurements on a high speed steam turbineAt least two thrust sensors, for redundancy, and for voting logic, are installed to measure axial rotor positionThrust bearing deterioration, failure, or sudden changes in steam pressure could quickly move the rotor axially and could cause collisions with rotor and stator

Thrust bearing failures can result in extremely costly repairs or even machine replacementThrust or Rotor PositionLPGENEXCIPHPTachIPHPThrust bearing failures are one of the most catastrophic failures

EccentricityEccentricity is a measure of rotor bow during start-upEccentricity is measured with at least one displacement sensor in the HP section with an eccentricity collar as the targetThis parameter is typically monitored from 0 to 600 rpmWhen a turbine is stopped during an outage, uneven heating at the top of the case and the weight of the rotor will introduce bow in the rotorDuring start-up, this bow is worked out before the turbine is brought online

EccentricityLPGENEXCIPHPTach`Over 600 RPM, Eccentricity can be set to zero by the monitorOr, over 600 rpm, vibration measurements are monitored

Case ExpansionCase expansion is a position measurement of the external case of the turbine as it expands during start-upLVDTs (Linear Variable Differential Transformers), the position sensors, are mounted on both sides of the foundation with sensor tips connected to the case. The LVDTs measure case expansion relative to the foundation.Large steam turbines, greater than 250MW, are not fixed at the HP section. The turbine pedestal is allowed to slide on the sole plate as the case expands when heated during start-up. While the case expands, if one side of the turbine binds, the case may bend, which could cause the rotor to contact the stator.

Differential ExpansionUpon start-up, due to mass differences, the rotor expands at a different rate than the caseDifferential expansion (D.E.) is a position measurement to insure that the rotor does not collide with the caseBy mounting the D.E. sensors on the case, and then measuring the position of the rotor, the result is the difference in position of the rotor relative to the caseD.E. is recommended for turbines 250MW and greater

Case ExpansionDifferential Expansion (difference between case and rotor expansion)LPGENEXCIPHPTachDifferential Expansion

Shaft VibrationShaft vibration is monitored for rotor position, rotor motion and bearing housing motionFor turbines up to 250MW, where case is massive as compared to rotor, relative vibration measurements are recommendedFor turbines 250MW to 650MW or greater, absolute vibration measurements are recommendedFor aeroderivative turbines where rolling element bearings are used, accelerometers with RMS processor and PeakVue processors are recommended

Turbo Machines Malfunction DetectionRubBowImbalanceLoosenessMisalignmentCouplingsRunoutFluid instabilitiesShaft cracks

Turbo Machinery Instrumentation12213434XYYX1234Machine CaseEmerson TIE Seminar May 2007

Proximity Probe Systems Pitfalls and HintsProx. Probe Systems

-24VComSignalOscillator/DemodulatorProbeConnectorIntegral CableExtensionCableDisplacement ProbesAlso known as non-contact, eddy current probes, proximity probes

API 670 gives examples of probe mounting blocks which employ a split clamp housin