Vibration Monitoring

Basic Vibration Analysis – Indonesia

SKF Reliability Systems – IndonesiaJaka Rusdianto

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Vibration Analysis

Conducted by:

Anis LutfiCondition Monitoring, SKF Reliability Systems

PT. Skefindo Primatama - INDONESIA

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SKF Reliability Systems – Asia PacificCondition Monitoring Products

1SKF PLATFORM





SKF GROUP

FACTORY UNIT

• 80 Factories

• 1 in Indonesia

• 45,000 employees

• ISO 14001

SALES UNIT

SKF SALES ASIA PACIFIC

SKF VIETNAM

SKF THAILAND

SKF TAIWAN

SKF KOREA

SKF PHILIPINA

SKF MALAYSIA

SKF SINGAPORE

SKF INDONESIA (PT.SKEFINDO) etc.

• 130 COUNTRY• 7,000 DISTRIBUTOR




SKF Network

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2MAINTENANCE PILOSOPHY





The evolution continues…

Not to fix failed machinery, but to prevent machinery failing.

• To maximize productivity.

• To ensure machinery operates satisfactorily and continuously for its rated life - or longer.

• To provide the highest machine availability, with minimum downtime due to maintenance and service.

• To continuously improve the production process.

• To optimize machine performance.

• Smoother, efficient running machinery costs less to operate, and produces a higher quality product.

• To provide a safe environment.

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Cost of Maintenance

$17–18 US

$11–13 US

$7–9 US

Type of Maintenance Program

Run to Failure

Maintenance

Predictive Maintenance

PreventiveMaintenance

Cost of MaintenanceUS $/HP/Year

Customer : Cevron Oil USA




How Do Predictive Maintenance Programs

Work?



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The Predictive Maintenance Cycle

Measurement exceeds

alarm limit

Measurement exceeds

alarm limit

Periodic MonitoringPeriodic

MonitoringAnalyze problem

Repair Equipment

Schedule repair(s)

No

Yes

Increase meas. intervals



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Work FlowWork Flow

PRISM4MICROLOG

ROUTE

SCHEDULE(CMMS)

WORK REQUEST(CMMS)

C.MONITORINGPLAN

DAILY REPORT

MONTHLY REPORT

DATA ANALYSIS

RELIABILITY(Keandalan)

MAINTENANCE(Perawatan)

PRODUCTION(Produksi)

Management



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How are Measurements Performed?

Sensors ... Sense and Convert Mechanical Energy Into

An Electrical Signal



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BufferedOutputs

Internet / Modem

SKF LANEnhanced

RS485

Ethernet

DCS / PAS / PLC or other Relay Outputs

4-20ma / 0-10VRS485

RS232 / TCP/IP

VM600

MCT

CMU

Microlog

Pens

MARLIN

RS485 / TCP/IP - OPC

RS232

RS232

P4 Only

CMMSInterface

/ RemoteView/ TrendOil

/HMI

Our Integrated Platform for Condition Monitoring



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Predictive Maintenance Measurements

Vibration

Temperature

Lube Oil

Process

–Pressure

–Flow

–Speed

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3Basic Vibration Philosophy




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Measuring Vibration

Vibration is considered one of the most effective measurements for monitoring thecondition ofrotating machinery



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Measurable Vibration Characteristics

Frequency - What is vibrating?

Amplitude - How much is it vibrating?

Phase Angle - How is it vibrating?



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Vibration FrequencyMeasurements & Units

• RPM (Revolutions Per Minute)• CPM (Cycles Per Minute)• CPS/Hz (Cycles Per Second/Hertz)• Orders of Running Speed (how

many times event occurs per shaft revolution)



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Vibration AmplitudeMeasurements & Units

Displacement (Distance)

Mils or Microns

Velocity (Speed - Rate of change of displcmt)

In./Sec. or mm/Sec.

Acceleration (Rate of change of velocity)

G’s - In./Sec.2 or Meter/Sec.2



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Amplitude vs. Frequency

When analyzing vibration we look at two components of the vibration signal, its amplitude and its frequency.

Vibration amplitude indicates the severity of the problem.

Vibration frequency indicates the source of the problem.



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Displacement Probe/Eddy Probe

• Measure Relative Distance Between Two (2) Surfaces

• Accurate Low Frequency Response• Limited High Frequency Sensitivity

• Require External Power Source



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Velocity Sensors

• Often Measure Bearing Housings or Machinery Casing Vibration

• Effective in Low to Mid Frequency Range (10 Hz to around 1,500 Hz)

• Self Generating Devices

• Are Electro-Mechanical Devices With Moving Parts That Can Stick or Fail



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Accelerometers

• Rugged Devices

• Operate in Wide Frequency Range (Near 0 to above 400 kHz)

• Good High Frequency Response

• Some Models Suitable For High Temperature

• Require Additional Electronics



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Sensor Relationships

10 100 1,000 10,000

Frequency (Hz)

10

1.0

0.1

1

0.01

100

Displacement (mils)Acceleration(g's)

Velocity (in/sec)

Common Machinery Operating Range

Amplitude(mils, in/sec, g’s)



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Same Data in Velocity and Acceleration

VelocitySpectru

m

Acceleration

Spectrum

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4Vibration Analysis




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Detection vs. Analysis

Detection

Alarm limits are established for each measurement. When the measurement’s value exceeds its programmed alarm limits, the predictive maintenance software or data collector notifies the analyst of a problem.

Analysis

Once detected, analyzing exceptional measurements provides insight to the problem itself, and to its root cause.



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Types of Alarms

Overall Vibration Limits

Spectral Enveloping

Spectral Bands

Phase Alarms



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ISO Standard

Vibration StandardISO 2372-1974



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ISO Vibration Severity Chart



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Overall Vib. Alarm

Assessing OverallVibration Severity

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5Vibration Spectrum




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What is Vibration Analysis ?

Vibration Analysis is a measure of the energy being emitted from a surface due to forced and natural oscillatory movement. The energy is captured as vibrations and displayed in two common form:

1. Time vs Magnitude - known as time wafe form2. Magnitude vs frequency - known as FFT



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Typical Vibration Analysis Display Formats

Overall Vibration (Trending)FFT Spectrum (Trending/Analysis)Time Waveform (Trending/Analysis)Other Processing Methods

– Acceleration Enveloping– SEE



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FFT Spectrum Analysis

FFT Spectrumshows component vibrationsignals at their respectivefrequencies

low freq.

high fre

q.

frequency

amplitude

frequency



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Spectral Pattern Recognition(velocity spectrum)

1X

2X 3X

4X

frequency

amp

litu

de

< 1X

low frequency rotational events and harmonics(i.e. imbalance, misalignment, looseness, etc.)

high frequency events(i.e. bearing or gear-mesh)

10X



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Spectral Example

1

2

3

baseline spectrum (norm)

higher than normal1X vibration signal

1X

2X

3X

bearingfreq..

gearmeshfreq.

higher than normal1X and bearingvibration signals

Known good measurement collected whenmachine was known to be in good runningorder.

1X running speed peak is significantly higher than normal. Indicates a vibration signal occurring once per shaft revolution. Typically caused by misalignment or imbalance.

Higher than normal 1X running speed peak and bearing fault frequency peaks indicate that 1X rotational problem has caused bearing damage.



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Sources of Vibration

Specific patterns in the spectral signatures are recognized as being related to specific machine problems.• Misalignment 1x or 2x shaft speed

• Imbalance 1x

• Bent shaft 1x or 2x Axial

• Looseness 2x to 10x

• Gearmesh # of teeth x RPM

• Bearing Defects bearing defect frequencies



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Misalignment

AngularMisalignment

ParallelMisalignment



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Velocity Measurement Showing Misalignment



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Imbalance - Diagnosis

static imbalance - vibration across machine“in phase”

couple imbalance - vibration across machine“180 degrees out ofphase”



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Velocity measurement Showing Imbalance



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Bent Shaft



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Bent Shaft - Diagnosis

1 - axial measurements across machinetypically 180 degrees out of phase, and ...2 - radial measurements across machineare typically in phase



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Velocity measurement Showing Bent Shaft Problem



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Mechanical Looseness



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Enveloping measurement showing Mechanical Looseness

Problem

Journal bearing on 600 MW Steam Turbine



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Gear-mesh Frequencies

GMF = # of teeth x RPM



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Gear Defects

• The gear mesh frequency is equal to the gear shaft rotating speed times the number of teeth on that gear.

• The amplitude will vary with the load.

• Two equal gearboxes can have very different amplitudes under the same loads.

• ALWAYS collect a time domain spectrum on each gear shaft bearing.



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Acceleration Measurement Showing Gear-mesh Frequencies



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Mining Gearbox Time Domain 208 RPM



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Why Do Bearings Fail?

inadequate lubrication- too much- too little- contaminated

excessive load caused by:- misalignment- imbalance- bent shaft- etc.....

improper handling or installation

ageflaw on outer race



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Enveloping

Band Pass Filter is specifiedaccording to defect harmonicfrequencies of interest

low frequency events filtered out, high frequency defect harmonics emphasizeddue to low signal to noise ratio, these highfrequency harmonics are then summed andfolded back to the defect’s fundamental frequency

resulting enveloped signal,measured in gE

defect fundamentalfrequency

fundamentalfrequencyharmonics



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Bearing Defect Frequencies

BPFOBall Pass Frequency Outer Race

BPFIBall Pass Frequency Inner Race

BSFBall Spin Frequency

FTFCage Frequency orFundamental Train Frequency



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Acceleration Enveloping on bearing with Outer race defect



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Acceleration Enveloping on bearing with Inner race defect



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Acceleration Enveloping on bearing with Cage defect



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Enveloping Severity ChartISO 10816

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Engineering

Vibration Monitoring