Understanding The Benefits Of Vibration Testing

Understanding the Benefits of VibrationTestingNovember 15, 2012

Agenda Introductions / HistoryBenefits of Vibration TestingOverview of Vibration TestingBearing Faults9 Stages of Bearing WearTraditional Bearing AnalysisNew Automated Bearing DiagnosticsComparison of Vibration Testing MethodsAnother type of vibration testing – screening toolsWhen to use – diagnostic tester or screening

Introductions / History

Introductions / History

Introductions / History

Maintenance PracticesReactive maintenance:“run to failure”No actions taken untilmachinery fails.Preventive maintenance:“calendar-based”Actions scheduledregardless of actualcondition of equipment.Predictive maintenance:“condition-based”Actions taken only after faultfound, monitored over time.The Bathtub CurveBreak InNormal OperationWear OutCasualtiesTimeUnplanned downtime, highlabor costs, reducedproduction, highmaintenance costs,machines drive staffFault free machinesrepaired unnecessarily,higher program costsEquipment repaired whenneeded, increasedproduction, reduced failuresand maintenance costs6

CBM TechnologiesVibration AnalysisFor diagnosing mechanicalfaults in rotating machines.Oil AnalysisFor finding problems withlubricant; gearboxes andreciprocating machinesIR ThermographyMotor TestingFor finding electrical hotFor finding a wide variety ofspots in switchgear andmotor faultsmotor controllers. Alsoused to find mechanical andprocess hot spots.Ultra SoundFor locating air leaks7

Benefits of Vibration Testing Predictability: give maintenance staff time to schedulerequired repairs and acquire needed parts. Safety: take faulty equipment offline before a hazardouscondition occurs. Revenue: fewer unexpected and serious failures, helping toprevent production stoppages that cut into the bottom line. Increased maintenance intervals: life of equipment can beextended and maintenance can be scheduled by need. Reliability: fewer unexpected or catastrophic failures - problemareas can be anticipated before failure Peace of mind: builds confidence in maintenance schedules,budgeting, and productivity estimates.8

Early Indicators of Machine Health In the world of mechanical maintenance, vibration remainsone of the earliest indicators of a machine’s health.Point where failurestarts to occurChanges in Vibration P-F Interval 1-9 monthsWear Debris in Oil P-F Interval 1-6 mosPP Potential FailureP1IR Thermography P-F Interval 3-12 wksP2Quantitative PM P-F Interval 5-8 wksP3P4P5Audible Noise P-F Interval 1-4 wksHeat By Touch P-F Interval 1-5 daysP6FThe P-F Curve, Adapted from John Moubray’s book “Reliability Centered Maintenance II”F Failure

Thermography and VibrationThermography is the measurement of temperature remotelyto indicate equipment health and assigning a color basedon the temperature.–––––––Electrical equipmentElectrical circuitsMechanical equipmentHeating/cooling equipmentBuilding envelopeElectronicOther

Thermography and Vibration Use IR Thermography to supplement bearing diagnostics

Overview of Vibration TestingTransducer picks upvibration signals frombearing locations andtransmits them to adata collection device All rotating equipment generate a unique vibration signal or “signature” These unique signals are usually captured in series, with the signal’s amplitude(y-axis) depicted over time (x-axis). This is called a time waveform.

Making Vibration Data Easier to InterpretFFT The wave form contains informationabout the machine where measured But the patterns of different eventsare overlapped and jumbled together Frequency analysis performed in thedata collector simplifies the waveform Spectrum is the plot of the signal’samplitude (y –axis) against frequency(x-axis)

Common Machine Faults & Spectrum Analysis Every machine componentproduces a unique type ofvibration signal. Signals displayed in thevibration spectrum often formcharacteristic patterns. Pattern recognition is a key partof vibration analysis but4 Common Faults are:significant training and Imbalanceexperience are necessary toread the patterns. Misalignment Looseness Bearing Failures

Four common causes of vibration1.Bearing 1215

Bearing Faults Replacing bearings based on calendar or running hours bearings may be replaced too early or too late Scatter of bearing life ranges from hours to years Bearing faults can account for 60% of mechanical problemsSnap ring grooveBearings fail due to: poor installation poor lubrication contamination wear/fatigue other faultsBallSeal/shieldgroove & notchInner ringInner raceOutsidediameterBoreCageInner ringfaceOuter ringfaceOuter ringOuter race

Bearing TypesRoller bearings: A rolling-elementbearing carries a load by placing roundelements between the two piecesJournal bearings: simplest type ofbearing, just a bearing surface and norolling elements. The journal slidesover the bearing surface.

Where to measure on machineMOTOR18COUPLINGCOMPRESSOR

Two Frequency rangesLow Range DataImbalance, Misalignment, Fan blades, PumpImpeller, Looseness, FoundationHigh Range DataFirst bearing fault indication, motorbars, gear mesh, turbine vanes

Overview of Vibration TestingWe can simplify it down to a 3 step process:1. Identify vibration peaks as they relate to a sourcecomponent on the machine.2. Look for patterns in the data based on vibration rules3. Measure the amplitude of the vibration peak to determinethe severity of the fault.Once the fault andseverity are determined,a repair can berecommended and awork order generated.

Roller Bearing Faults Bearing frequencies are non-synchronous The geometry of the balls, cage and races show up atdifferent speeds – not a multiple of shaft speed In most cases, non-synchronous peaks are roller bearings Most vibration programs use bearing frequencies:1. Inner race2. Outer race3. Cage4. Ball Spin

Roller Bearing Faults Here is a vibration peak at 3.56X shaft speed This is probably from a roller bearing

9 Stages of Bearing Wear- Early bearing wear first shows up in the high frequencies- Nothing is seen in the low frequencies- This data looks healthyStage 1

9 Stages of Bearing WearA peak shows up at 3.1XThis can’t be imbalance, misalignment, looseness, or from fan blades or pumpimpeller vanes.Stage 2Verysmall flaw

9 Stages of Bearing Wear- Next, the peak at 3.1X grows in amplitude indicating that the bearing isgetting worse.Stage 3

9 Stages of Bearing Wear- Next, a harmonic of the 3.1 peak appears at 6.2, indicating that the bearing isgetting worse.Stage 4Slight

9 Stages of Bearing Wear- Sometimes, the bearing wear will cause looseness which shows up asincreased harmonic peaks.Stage 5

9 Stages of Bearing Wear- As the bearing defect moves in and out of the load zone, modulation of theshaft is seen as 1X sidebandsStage 6ModerateSmall flaw

9 Stages of Bearing Wear- As bearings wear, they produce larger quantities of random vibration andimpacts. This is first seen as a haystack around the base of the bearing tone.Stage 7SeriousMedium flaw

9 Stages of Bearing Wear- Eventually, the random vibration raises the noise floor of the spectrum.Stage 8ExtremeFriction heatLarge flaw

9 Stages of Bearing Wear- Too late - Game Over!Stage 9

Traditional Bearing Analysis First, look at complex timewaveform to find impacting. Next, look up the bearingfrequencies from a databaseof thousands of bearings. Then, overlay to identifypossible bearing faults on thefrequency spectrum. But, what if you don’t knowor don’t keep track?

New Automated Bearing Diagnostics1.2.3.4.Normalize the DataSynthetic BaselineAutomated Peak ExtractionDiagnostic Report

How does the Diagnostic Engine Work?Good Good GoodThe technology behind the answerStep 1 - Data Normalization: uses shaft speed input from user (nameplate or tachometer) Normalization algorithmsearches for a peak insidenarrow windowSets nominal speedShaft – Pump Vane - Bearing Rescales data from RPM to multiples of shaft rotation or ordersIdentifies vibration sources inside machine

How does the Diagnostic Engine Work?Step 2 - Synthetic Baseline: screens data that has been collectedPeak at 7.29 X is above thebaseline BearingDerived from algorithms defining a healthy machine Machine technical descriptions and data analyzed over40 years Computes baseline noise level from machine typeselected by user Computes other peaks from shaft speed andcomponents Exceedances used for next diagnostic step

How does the Diagnostic Engine Work?Step 3 – Pattern Recognition to determine machine faults Over 4700 rules for machine faults Based on analyzing patterns seen inrotating machinery Most common faults are imbalance,misalignment, looseness, roller bearings Example:9 Stages of roller bearing wear

How does the Diagnostic Engine Work?Step 4 – Diagnosis with fault / severity / location / recommendationWhere is the problem? How bad is theproblem?What is the problem? Motors (AC/DC, ¼ HP )Fans and BlowersBelts and Chain DrivesGearboxes and CouplingsPumps (Centrifugal, Piston, Sliding Vane,Propeller, Screw, Rotary Thread/Gear/Lobe )Compressors (Piston, Centrifugal, Screw)Closed Coupled Machines and SpindlesBearing WearImbalanceMisalignmentLooseness200 DifferentFault Calls

Comparison of vibration testingData collector Data analyzerVibration tester Vibration meter Production Critical – top 10 %Complex system– many variablesReliability Team requiredData Collector / Analysis S/WVital/Important – Costly repairsMiddle 60%No support from Reliability TeamBasic machines – few variablesMaintenance Staff - part time Turbine GeneratorsDiesel GeneratorsPaper MachinesMulti-machines BeltsNon vital – ExpendableBottom 30% - Low priority38

Compare trends and reportsTrendingData collector Data analyzerVibration tester Motor ImbalanceMotor Bearing WearVibration meter Report

Another Type of Vibration TestingSimple vibration testing: Overall vibration/bearing measurements Vibration screening devices provide quick feedback of equipment condition A single number for overall vibration to understand whether there is aproblem, instead of analyzing vibration in-depth with a spectrum. If the machine vibration or noise is higher, this value will increase. Use vibration screening tools to make quick “go” or “no go” decisions bychecking the value against a pre-set alarm level, comparing it to ISOStandards (ISO 10816) and trending the results over time.40

Benefits of Vibration Screening ToolsFront line mechanicalmaintenance teams need: A quick screening tool to fit intoexisting rounds. Reliable and repeatablemeasurements of rotatingequipment to make imperativego/no-go maintenance decisions. Ability to trend readings over timeand notify a consultant orreliability engineer whensomething abnormal arises. Quick understanding of overallmachine and bearing condition, todecide on repairs and repairequipment.41

What does it measure?Vibration Meter is amultifunction vibrationchecker which Provides quantifiableresults of bearingcondition, overallvibration, temperature Assesses the severityon a severity scale Provides ability toupload the data to PCfor later trending42

Types of Vibration Testing0.4 in/sec43

Checks against machine categoriesChiller (refrigeration) Reciprocating CentrifugalPositive Displacement Pumps Piston pumps Gear pumpsFans Belt-driven Direct drive Vacuum blowers Shaft-mounted integral Large forced and induced draft fans Axial flow fans (belt or direct drive)Air compressors Reciprocating Rotary screw CentrifugalCooling tower drives Long, hollow drive shaft Belt drive Direct driveCentrifugal Pumps Vertical pumps Horizontal pumps Boiler feed pumpsBlowers Lobe-type rotary blowers Multi-stage centrifugal blowersGeneric gearboxes Single stage gearboxMachine tools Spindles44