Vibration Monitoring & Analysis

What is Vibration ? It is motion of mechanical parts back and forth from its position of rest /neutral position. Vibration Monitoring

What causes Vibration ? Induced Force & Freedom for Movement

Vibration Monitoring Harmful Effects of Excess vibration Increased load on BRGs: Reduced BRG Life Higher Forces on Mountings: Foundation Loosening and Damage of Support Structure Increased Stresses of M/c : Risk of fatigue components

Vibration Monitoring Harmful Effects of Excess vibration Decreased Equipment efficiency. Reduced Output Quality. Increased Maintenance Cost due to more Component Failures and Unplanned Operations Unsafe Operating Environment

Vibration Monitoring Vibration Monitoring Problem Identifications Unbalance Misalignment Mechanical Looseness Antifriction / Sleeve Bearing Defects Gear Defects

Vibration Monitoring Vibration Monitoring Problem Identifications Belt Defects Impeller / Blade Defects Bent Shaft Electrical Problems Resonance

Vibration Monitoring Fundamental Realities All Machines vibrate. An increase in vibration level is a sign of trouble & amplitude of Vibration depends on the extent of defect in the machinery components Each trouble will create vibration with different characteristics

VIBRATION FUNDAMENTALS TIME Period(T) (1 complete cycle) Neutral Position Upper Limit Lower Limit

Characteristics of Vibration Characteristics of Vibration Vibration characteristics are Amplitude FrequencyHz or CPM PhaseAngle or clock face Displacement Velocity Acceleration

Parameter Selection Frequency sensitivity Displacement<600CPM Velocity600-60,000CPM Acceleration>60,000CPM Spike Energy/SEE Ultrasonic range

Frequency sensitivity

Vibration Monitoring Displacement Velocity Acceleration

FFT FAST FOURIER TRANSFORM. THE PROCESS OF TRANSFORMING TIME DOMAIN SIGNAL TO FREQUENCY DOMAIN. THE TIME DOMAIN SIGNAL MUST FIRST BE SAMPLED AND DIGITIZED.

Time Domain - overall data is the sum of all exciting and reacting forces Time Resultant Complex Waveform

Spectrum Analysis Enables precise evaluation of machinery condition and prediction

Fmax, LINES, AVERAGES. Fmax REPRESENTS THE MAXIMUM FREQUENCY RANGE IN CPM OR HZ TO BE SCANNED BY THE INSTRUMENT. Fmax SHOULD NOT BE SET TOO HIGH SO THAT THE RESOLUTION AND ACCURACY SUFFERS OR IT SHOULD NOT BE TOO LOW SO THAT WE MISS SOME IMPORTANT HIGH FREQUENCIES.

GUIDELINES FOR SETTING Fmax. FOR MACHINES HAVING ANTI- FRICTION BEARINGS:- Fmax = 60 x RPM FOR MACHINES HAVING SLEEVE BEARINGS:- Fmax = 20 x RPM FOR GEAR BOXES:- Fmax = 3.25 x GMF

LINES OF RESOLUTION THE RESOLUTION IS THE NUMBER OF LINES OR CELLS WHICH ARE USED TO CALCULATE AND DISPLAY THE FREQUENCY SPECTRUM. THE BANDWIDTH CAN BE CALCULATED BY DIVIDING Fmax BY THE LINES OF RESOLUTION. THE GREATER THE NUMBER OF LINES, THE BETTER IS THE ACCURACY.

FREQUENCY RESOLUTION Bandwidth = F max total lines of resolution Amplitude Frequency F max lines or bins or cells of resolution

FFT Calculation Time = Time to calculate FFT from Time Waveform [assuming no overlap processing] Spectrum Data Collection Time FFT Calculation Time = (60) ( #FFT Lines) (#Averages) Frequency Span Where: #FFT = Number of FFT Lines or Bins in Spectrum # Averages = Number of Averages Frequency Span measured in CPM

FFT SPECTRUM

OVERALL VIBRATION Total summation of all the vibration,with no regard to any particular frequency.

OVERALL VIBRATION Overall vibration is the total vibration energy measured within a frequency range. Measuring the “overall” vibration of a machine or component, a rotor in relation to a machine, or the structure of a machine, and comparing the overall measurement to its normal value (norm) indicates the current health of the machine. A higher than normal overall vibration reading indicates that “something” is causing the machine or component to vibrate more.

Overall Vibration Total summation of all the vibration,with no regard to any particular frequency. OA = OA=Overall level of Vibration Spectrum, Ai = Amplitude of each FFT line n = No. of FFT Lines of resolution, N BF= Noise Bandwidth for Window chosen A1 + A2 + ………………………+An 222 N BF N BF

NOTE: Don’t be concerned about the math, the condition monitoring instrument calculates the value. What’s important to remember is when comparing overall vibration signals, it is imperative that both signals be measured on the same frequency range and with the same scale factors.

What is Phase? The position of a vibrating part at a given instant with reference to a fixed point or another vibrating part. The part of a vibration cycle through which one part or object has moved relative to another part. The unit of phase is degree where one complete cycle of vibration is 360 degrees.

Phase Phase is a measurement, not a processing method. Phase measures the angular difference between a known mark on a rotating shaft and the shaft’s vibration signal. This relationship provides valuable information on vibration amplitude levels,shaft orbit, and shaft position and is very useful for balancing and analysis purposes.

Vibration Phase

Additional Illustration on Phase

PHASE AN ILLUSTRATION 30 Micron 10 degrees 32 Micron 10 degrees Shaft centre line moves up and down in a planer fashion

PHASE AN ILLUSTRATION 30 Micron 10 degrees 32 Micron 190 degrees Shaft center line moves up and down in a rocking fashion

MACHINE TRAIN MISALIGNMENT Note: All phase readings corrected for pickup direction TURBINEG/BHP COMPLP COMP AXIAL PHASE (degrees)

Comparing Overall Levels Across Mounting Interfaces

Phase application A B C A5 Microns, 10 degrees B7 Microns, 12 degrees C25 Microns, 175 degrees Bolt at C is loose

Vibration Analysis of Common Problems

Vibration Analysis Unbalance Amplitude proportional to the amount of unbalance Vibration high normally in radial direction (may be also in axial direction incase of overhung and flexible rotors ). 1* RPM vibration is greater than 80% (normally) of the overall reading.

Vibration Analysis Unbalance Horizontal and vertical 1* RPM amplitude should be nearly same, although it also depends on system rigidity on the particular direction. Other frequency peaks may be less than 5% of the 1*RPM amplitude Phase shift of 90 deg. When sensor moves from horizontal to vertical.

UNBALANCE Operating conditions such as load, flow condition and temperature effect unbalance –Balance under normal operating conditions Changes in track and pitch angle of fan blades can result in “Aerodynamic Unbalance”

Typical Spectrum For Unbalance

MISALIGNMENT BIGGEST PROBLEM INITIALLY Operating temperature can affect alignment –Machines aligned cold can go out when warm Bases or foundations can settle Grouting can shrink or deteriorate Increases energy demands

MISALIGNMENT Forces shared by driver and driven (not localized) Level of misalignment severity is determined by the machines ability to withstand the misalignment –If coupling is stronger than bearing the bearing can fail with little damage to the coupling

Three Types of Misalignment Combination (most common) Angular Parallel or Offset

General Characteristics Of Misalignment Radial vibration is highly directional 1X, 2x, and 3x running speed depending on type and extent of misalignment –Angular1x rpmaxial –Parallel 2x rpmradial (H & V) –Combination1,2,3x rpmradial and axial

Typical Spectrum for Misalignment

Vibration Analysis Misalignment Angular Misalignment High axial vibration ( Greater than 50% of the radial vibration) 1*, 2*, 3* RPM normally high. 180 deg. Out of phase across the coupling

Angular Misalignment Produces predominant 1x rpm component Marked by 180 degree phase shift across the coupling in the axial direction

Vibration Analysis Misalignment Off-Set Misalignment High Axial vibration. Also shows high radial vibrations. 1*, 2*, 3* RPM high. 2* often larger than 1* In case of severe misalignment, much high harmonics (4* - 8*) or even a whole series of high frequency harmonics will be generated. 180 deg. Out of phase across coupling

Parallel Or Offset Misalignment Produces a predominant 2x rpm peak in the spectrum Marked by 180 degree phase shift across the coupling in the radial direction.

Typical Spectrum for Misalignment

Axial Phase Showing Misalignment

Other Types Of Misalignment

Vibration Analysis Mechanical Looseness Caused by structured looseness / weakness of machine feet, base plate or foundation; also by deteriorated grouting, loose base bolts and distortion of the frame or base. Radial vibration high 2* RPM & 1* RPM dominant 180 deg. Phase differences between mating surfaces which have looseness between them.

Vibration Analysis Mechanical Looseness Caused by structured looseness / weakness of machine feet, base plate or foundation; also by deteriorated grouting, loose base bolts and distortion of the frame or base. Radial vibration high 2* RPM & 1* RPM dominant 180 deg. Phase differences between mating surfaces which have looseness between them.

Looseness Looseness produces 2X RPM Freq.

Vibration Analysis Mechanical Looseness Caused by looseness in bearing housing bolts and cracks in the frame structure. Radial vibration high 2* RPM normally dominant. 0.5*, 1* and 3* RPM may also be present Substantial Phase difference between mating surfaces which have looseness between them

LOOSENESS Not an exciting force Allows exciting frequencies already present to exhibit much higher amplitudes Loss or reduction in normal stiffness Caused by: –loose mounting bolts –deterioration of grouting –cracked welds

Two Types Of Looseness Looseness of Rotating Components –Loose Rotors –Bearings Loose on the Shaft or in Housing –Excessive Sleeve Bearing Clearances Looseness of Support System –Loose Mounting Bolts –Grouting Deterioration –Cracks –Poor Support –Frame Distortion

Looseness Of Rotating System Rattling condition cause impacts due to excessive clearance in a rolling element or sleeve bearing Impacts cause multiple running speed harmonics to appear in the spectra Identified by: –multiple harmonics –unstable phase –highly directional radial vibration

Typical Spectrum for Looseness of Rotating System

Looseness Of Support System FFT readings show 1x rpm, 2x rpm, and 3x rpm components Structural looseness / weakness will cause high 1xrpm peak in FFT Identified by –Highly directional radial vibration –Bouncing –Taking comparative phase readings across interfaces and look for amplitude variation –Typically loose in vertical direction

Looseness Of Support System

Modern Trend in Vibration Technology

Condition Monitoring System Integration SOFTWARE DCS CMMS NETWORK PdM TECHNOLOGIES ON-LINE ANALYSIS SURVEILLANCE ON - LINE PERIODIC WALKAROUND OFF- LINE CENTRALISED PROTECTION DISTRIBUTED PROTECTION CONTINUOUS PROTECTIO N

Overall Data Acquistion time waveform THE DCS MONITOR DCS OUTPUT 4-20mA

current value Overall Data Trends- this is what the DCS records lo alarm hi alarm The limitation is that it does not adequately reflect changes at higher frequencies which can increase by 100% but only add 1% to the overall energy level

Vibration Analysis time waveform transducer Vibration Spectrum Data Collector Protection Monitor and / or

Band Alarms, associate with each rotating element frequency bands hi alarm lo alarm

Band Trending, the new way forward lo alarm hi alarm Trend and alarm the: Machine unbalance Alignment Gear mesh Bearings etc

Emonitor Odyssey: spectrum band alarming though its diagnostic tools feature for both On & Off line gives advanced machinery analysis and reduces False Alarms

EMONITOR Odyssey: Frequency Band Trends Frequency Trend of Single Measurement

DIAGNOSTICS - the advantage of frequency band trending Root cause analysis is a complex machine specific exercise considering all eventualities Expert systems are a one off diagnosis and do not show a trend Frequency band trending is specific to root cause analysis Band alarming also indicates vibration signals that are outside the established norms Trending alignment, unbalance, gear meshing and bearing condition condition is more specific A complex issue simplified without the need of specialist customisation and regular updates

DCS Limitations - Summary We have shown that putting total belief in the DCS vibration trend is highly risky Machinery failures still happen with on-line vibration monitoring with 4-20mA data to the DCS. Most causes are due to higher frequency signals swamped by the overall levels. Advanced machinery protection through Frequency Band Trending and Alarming - more specific than an Expert system. The latest S/w based Analysers incorporates Narrow Band Alarming. They offer machinery protection and narrow band alarming. A lower cost solution is periodic manual Data Collection.

ESHAPE: Modal analysis using phase for advanced diagnosis and better understanding of system response

On line Vibration and other monitors Innovative, fully-digital design Exceeds API 670 specification Widely-used system Fully field programmable Low installation cost ModBus protocol

TYPICAL APPLICATION

FSHPLPGENEX TURBINE SUPERVISORY STATOR END WINDING CWP BFP ID FD PA AUXILIARIES ENGINEERINGOPERATIONSDCS ODYSSEY SERVER POWER PLANT INTEGRATION GATEWAY TO CMMS VIBRATION ANALYSER DATA LOGGER

ENGINEERING DCS ODYSSEY CLIENT SERVER GATEWAY TO CMMS ANURAKSHAN VIBRATION ANALYSER Plant Integration with LAN or WAN FSHPLPGENEXFSHPLPGENEXFSHPLPGENEX CONTROL ROOM No 1CONTROL ROOM No 2CONTROL ROOM No 3 TG 1TG 2TG 3 ETHERNET

NETWORKING THE INFORATION - LAN / WAN e.g. NOIDA HQ CM CELL VINDHYACHAL RIHAND TALCHER UNCHAHAR KAYAMKULAM PLANT OPERATION S GATEWAY TO CMMS ANURAKSHAN

Using PlantLink Vibration Trend Plot Digital Picture of Plant Hyperlink to equipment Hierarchy Automatic notification on Equipment Alarm Status Click on Measurement Label to link to plots or other views.

Information however you want it !

X-Window Screen Captures

Scenario of Instruments &Sensors & Probes Velocity sensors are made in India Accelerometers range over 150 types –standard –Low frequency –High temperature (Gas Turbines) –Special application Eddy current probes - comprehensive range Others available for process measurement

Vibration Datacollectors Many vendors Select on ‘Fitness for Purpose’ Intrinsic Safety Dust & Moisture proof Diagnostic Capability