vibration basic mil

Mechanalysis India Limited

MMECHANALYSISECHANALYSIS INDIA LTD. INDIA LTD.

WELCOMES ALL PARTICIPANTS WELCOMES ALL PARTICIPANTS

TO THE STRUCTUREDTO THE STRUCTURED

TRAINING COURSE ONTRAINING COURSE ON

VIBRATION TECHNOLOGYVIBRATION TECHNOLOGY

@@HOTEL AMBASSADOR - DELHIHOTEL AMBASSADOR - DELHI

WELCOME NOTE


SOLUTION PROVIDERNUCLEARNUCLEAR

AUTOAUTO MARINEMARINEPAPERPAPEROIL & GASOIL & GAS

STEELSTEEL

TURBINETURBINE

POWERPOWER

COOLING TOWERCOOLING TOWER

ALUMINIUMALUMINIUM

MILMIL

POWERPOWER


OUR BELIEF

WE BELIEVE YOU ARE OUR PARTNERS IN THIS BUSINESS. BECAUSE MORE THAN WHAT WE HAVE THOUGHT YOU,

WE HAVE GAINED MUCH MORE FROM YOU.


BRIEF COMPANY HISTORY

• FOUNDERS OF PREDICTIVE MAINTENANCE – 1952 (IRD).FOUNDERS OF PREDICTIVE MAINTENANCE – 1952 (IRD).

• PIONERS IN THE FIELD OF CONDITION BASED MAINTENANCE.PIONERS IN THE FIELD OF CONDITION BASED MAINTENANCE.

• INVENTED VARIOUS INSTRUMENTS AND SOFTWARES.INVENTED VARIOUS INSTRUMENTS AND SOFTWARES.

• GAVE THE INDUSTRY ITS FIRST ANALOGUE AND DIGITAL ANALYZER.GAVE THE INDUSTRY ITS FIRST ANALOGUE AND DIGITAL ANALYZER.

• STRATEGIC TAKEOVER IN 1997 BY ENTEK SCIENTIFIC INC.STRATEGIC TAKEOVER IN 1997 BY ENTEK SCIENTIFIC INC.

• THIS OPENED DOORS FOR FASTER & ACCURATE DATA COLLECTION.THIS OPENED DOORS FOR FASTER & ACCURATE DATA COLLECTION.

• IT ALSO LAUNCHED DIFFERENT USER FRIENDLY SOFTWARES.IT ALSO LAUNCHED DIFFERENT USER FRIENDLY SOFTWARES.

• STRATEGIC TAKEOVER IN 2001 WITH ROCKWELL AUTOMATION INC.STRATEGIC TAKEOVER IN 2001 WITH ROCKWELL AUTOMATION INC.

• THIS HAS INTEGRATED US TO THE WORLD OF PLC AND AUTOMATION.THIS HAS INTEGRATED US TO THE WORLD OF PLC AND AUTOMATION.


MY CREDENTIALS• BORN IN A PLACE 365 DAYS ON HOLIDAY (GOA)BORN IN A PLACE 365 DAYS ON HOLIDAY (GOA)

• PASSED ENGINEERING IN STRUCTURAL FAB & ERECTION ENGG.PASSED ENGINEERING IN STRUCTURAL FAB & ERECTION ENGG.

• TRAINED IN GODREJ & BOYCE FOR THE ISRO PROJECT (INSP)TRAINED IN GODREJ & BOYCE FOR THE ISRO PROJECT (INSP)

• JOINED AS A FULL FLEDGED TRAINEE ENGINEER IN THERMAX LTD.JOINED AS A FULL FLEDGED TRAINEE ENGINEER IN THERMAX LTD.

• WAS AN ERECTION & COMMISSIONING ENGG. WAS AN ERECTION & COMMISSIONING ENGG.

• IN 1996 POSITIONED AS A TROUBLE SHOOTER IN ROTATING EQPTS.IN 1996 POSITIONED AS A TROUBLE SHOOTER IN ROTATING EQPTS.

• IN 1999 JOINED ENTEK IRD IN THE CONSULTANCY DEPARTMENT.IN 1999 JOINED ENTEK IRD IN THE CONSULTANCY DEPARTMENT.

• NAMED MR. NAVY, SINGLE POINT SUPPORT TO ALL NAVAL BASES.NAMED MR. NAVY, SINGLE POINT SUPPORT TO ALL NAVAL BASES.

• IN 2001 PROMOTED AS ASST. MANAGER WEST.IN 2001 PROMOTED AS ASST. MANAGER WEST. • CERTIFIED TRAINER FOR VT-1 COURSE SINCE OCTOBER 2001.CERTIFIED TRAINER FOR VT-1 COURSE SINCE OCTOBER 2001.


EVOLUTIONEVOLUTION

IT IT ALL ALL

STARTEDSTARTED

WITH WITH AA

VISIONVISION

TO KNOW THETO KNOW THE

FUTUREFUTURE


BROAD COURSE OUTLINEBROAD COURSE OUTLINEBROAD COURSE OUTLINEBROAD COURSE OUTLINE

BASIC CONCEPTS OF VIBRATION

INTRODUCTION TO MACHINERY DIAGNOSTIC TECHNIQUES USING VIBRATION.

AN OVERVIEW OF BALANCING


COURSE OUTLINECOURSE OUTLINECOURSE OUTLINECOURSE OUTLINE

A Vibration as an indicator of machinery condition

B What is vibration?

C What causes vibration?

D Vibration and machine life.

E A comparison of maintenance philosophies.

F Vibration as a Predictive Maintenance tool.

G The vibration Predictive Maintenance program.

H Additional applications for vibration detection and analysis.



A Vibration frequency

B Vibration amplitude

C Phase



1. SENSORS

2. INSTRUMENTS

3. Recognising common machinery problems.

Unbalance Defective rolling-element bearings

Bent Shafts Plain bearing problems

Misalignment Aerodynamic / hydraulic problems

Looseness Electric motor problems

Eccentricity Gear problems

Resonance Belt-drive problems


THE RULESTHE RULESTHE RULESTHE RULES

If you have a question



If you have an input



If you have feedback



The only dumb question is the one that is never asked !

I don’t know ….



If we have a discussion


MAINTENANCE STRATEGIESMAINTENANCE STRATEGIES

Affect all three of these principal losses.

– Downtime loss.

– Speed loss.

– Quality loss.


MAINTENANCE STRATERGIESMAINTENANCE STRATERGIES

• RUN TO FAILURE / BREAKDOWN MAINTENANCE.RUN TO FAILURE / BREAKDOWN MAINTENANCE.

• PLANNED / CALLENDER BASED MAINTENANCE.PLANNED / CALLENDER BASED MAINTENANCE.

• PREDICTIVE MAINTENANCE & PREDICTIVE MAINTENANCE &

• PROACTIVE MAINTENANCE.PROACTIVE MAINTENANCE.


RUN TO FAILURERUN TO FAILURE BENEFITS

– No maintenance(Run to failure)

– Some machines are cheaper to replace than repair.

DRAWBACKS– Unplanned shutdown resulting in production

loss.

– High inventory cost.

– Causes untimely failure

– Causes damage to the equipment and the attached equipment as well.

– Sometimes causes catastrophic failure.

COSTCOST


PREVENTIVE PREVENTIVE

Preventive Maintenance

BENEFITS

– Machine inspected at fixed intervals.– Reduces production downtime.– Allows scheduling hence reduces spare

inventory cost.

DRAWBACKS

– Setting of inspection period is critical. – Periodic disassembly of critical / non critical

machines is expensive and time consuming.– Biggest problem is of upsetting a machine

which is running smooth.

COSTCOST

2003


PREDICTIVEPREDICTIVE

COSTCOST

BENEFITS

– Minimizes machine damage and allows scheduling of down time, lab our & material

– Eliminates unnecessary overhauls– Machine inspected non-intrusively.– Allows machines in good operating

condition to continue to run .– Further reduces inventory cost.

DRAWBACKS

– Implementation cost is rather high.– Demands technical competence &

commitment to change.


HOW IT PREDICTSHOW IT PREDICTSHOW IT PREDICTSHOW IT PREDICTS

LEAD TIME

TIME TO PLAN:• SPARES • TOOLS• LABOUR• PRODUCTION

NORMAL OPERATIONS

SHUT DOWN ?

WARNING

FAILURE LIKELY

?

LOW

HIGH


PROACTIVEPROACTIVE

BENEFITS

– Maintains minimal downtime.– Controlling by taking precautions.– Protecting equipment.– Eliminates root cause of failure..

DRAWBACKS

– Requires qualification.– Engineering involvement.– Demands foresight.– Ongoing investment.

COSTCOST


THE PLANT CHALLENGETHE PLANT CHALLENGETHE PLANT CHALLENGETHE PLANT CHALLENGESUBJECTIVE EXPERIENCE


THE PLANT CHALLENGETHE PLANT CHALLENGETHE PLANT CHALLENGETHE PLANT CHALLENGEOBJECTIVE TECHNOLOGY


CASE STUDYCASE STUDYCASE STUDYCASE STUDY

5 identical service pumps

No spare capacity

Stressful service


DETAILSDETAILSDETAILSDETAILS

Equipment : Parallel Centrifugal Pump Sets

Failure Mode : Impellor corrosion / erosion

Detection : Loss of performance of plant - loss of group flow.

Cost: Production loss Rs. 2,45,000 / hour per unit down


METHOD - 1METHOD - 1METHOD - 1METHOD - 1

RUN TO FAILURE

Result : 4 failures per year / 16 hours per change out

Cost : Production loss Rs.1,56,80,000/- per year


METHOD - 2METHOD - 2METHOD - 2METHOD - 2PREVENTIVE (Periodic internal inspection and replacement)

Result: 1 failure per year / 16 hours per changeout

5 inspections per year

3 hours per inspection

Cost: Production loss Rs.75,95,000 / year


METHOD - 3METHOD - 3METHOD - 3METHOD - 3PREDICTIVE (Trend pump parameters and monitor vibration

characteristics).Result: 0 failures per year

1 pump replacement8 hours per change out

Cost: Production loss Rs.19,60,000 / year


METHOD - 4METHOD - 4METHOD - 4METHOD - 4PROACTIVE (Resolve design and installation problem.)

Result: 0 failures per year

1 pump replacement

8 hours per change out

Cost: Production loss Rs.0,00 / year


RELATIVE COSTSRELATIVE COSTS

Breakdown Maintenance

Preventive Maintenance

Predictive Maintenance

Proactive Maintenance

Rs. 1.57 Rs. 1.57 CRORES.CRORES.

Rs.76 Rs.76 LACSLACS

Rs.19,6Rs.19,6LACSLACS Rs.0.00Rs.0.00


STRATEGY REPRESENTATIONSTRATEGY REPRESENTATIONSTRATEGY REPRESENTATIONSTRATEGY REPRESENTATION

• Don’t limit your condition-based maintenance program to the detection Don’t limit your condition-based maintenance program to the detection of sudden-death faults.of sudden-death faults.

Cholesterol and bloodCholesterol and bloodpressure monitoringpressure monitoring

with diet controlwith diet control

Heart attack orHeart attack orstrokestroke

Monitoring and control Monitoring and control failure root causes,failure root causes,e.g., contaminatione.g., contamination

ProactiveProactiveMaintenanceMaintenance

BreakdownBreakdownMaintenanceMaintenance

Large maintenanceLarge maintenancebudgetbudget

Rs. 0.5 L Rs. 0.5 L

Detection of heartDetection of heartdisease using EKG ordisease using EKG or

ultrasonicsultrasonics

PredictivePredictiveMaintenanceMaintenance

Monitoring of vibration,Monitoring of vibration,wear debriswear debris Rs. 2 LRs. 2 L

By-pass or transplantBy-pass or transplantsurgerysurgery

PreventivePreventiveMaintenanceMaintenance

Periodic componentPeriodic componentreplacementreplacement

Rs. 5 LRs. 5 L

Rs. 8 LRs. 8 L

MaintenanceMaintenancestrategystrategy

TechniqueTechniqueneededneeded

Cost per year*Cost per year* Human BodyHuman BodyParallelParallel


DO WE REALLY

USE THESE

STRATERGIES?


APPLICATIONAPPLICATION

Failure Finding

Test

Re-design

On-Condition

Time-Based

Run-to-Failure

Usage-Based PMRun-to-Failure

Spare


RELIABILITY ECONOMICSRELIABILITY ECONOMICSRELIABILITY ECONOMICSRELIABILITY ECONOMICS

Maintenance equates to 15% to 40% of operating cost.

About 30% maintenance spending is found to be unnecessary.

Maintenance costs more than five times new equipment cost.

Maintenance may be the last major controllable cost.


COST OF MAINTENANCECOST OF MAINTENANCECOST OF MAINTENANCECOST OF MAINTENANCE

Direct maintenance cost

– Staff, Overtime, Contractors, Spares, tools etc.

Indirect maintenance costs

– High production costs,lost productionreduced quality, poor customer service

RsRs

RsRs


SEE WITH YOUR EYESSEE WITH YOUR EYESSEE WITH YOUR EYESSEE WITH YOUR EYES


FEEL THE DIFFERENCEFEEL THE DIFFERENCEFEEL THE DIFFERENCEFEEL THE DIFFERENCE


PRACTICING MAINTENANCEPRACTICING MAINTENANCEPRACTICING MAINTENANCEPRACTICING MAINTENANCE

Most facilities practice all four strategies to some degree.

What we wish to do is focus the emphasis on the most suitable strategy for our plant or sub-set of plant.

To do this ….. We need to plan

Maintenance as an integral part of the operation…. Wow

Project implementation is the key to success


THE IMPLEMENTATION LOOPTHE IMPLEMENTATION LOOPTHE IMPLEMENTATION LOOPTHE IMPLEMENTATION LOOP

Benchmarking PlanningSystems

IntegrationImplementation

ProcessImprovement

So what happens if we get it right? ? ….So what happens if we get it right? ? ….


IMPACTIMPACTIMPACTIMPACT

• Increased production capacity.Increased production capacity.

• Lower production costs.Lower production costs.

• Increased quality.Increased quality.

• Improves customer service.Improves customer service.

• AND THIS MAKES YOU COMPETITIVE AND DIRECTLY AND THIS MAKES YOU COMPETITIVE AND DIRECTLY IMPACTS YOUR IMPACTS YOUR PROFITABILITYPROFITABILITY..


MAKING SENSEMAKING SENSEMAKING SENSEMAKING SENSE

19301930 19401940 19501950 19601960 19701970 19801980 19901990 20002000

Repair after failure

Inspect, lubricate

Preventive maintenance

Systematic planning and scheduling

Diagnostics

Reliability engineering

Predictive maintenance

Operator maintenance

Concurrent engineering

Equip

ment

Eff

ect

iveness

and R

elia

bili

tyEquip

ment

Eff

ect

iveness

and R

elia

bili

ty

WHERE ARE YOU ON THE CURVE?


SUMMARYSUMMARYSUMMARYSUMMARY

If you don’t know where

you are, then how can you

get where you are going to.


BREAK - 1BREAK - 1BREAK - 1BREAK - 1

TEA BREAK


SESSION - 2


WHAT IS VIBRATIONWHAT IS VIBRATIONWHAT IS VIBRATIONWHAT IS VIBRATION

Any motion that repeats itself after an interval of time is called vibration or an oscillation.

The cyclic or oscillation motion of a machine or machine component from its position of rest.

Vibration is the response of a system to an internal or external stimulus causing it to oscillate or pulsate.


IT’S ALL ARROUND USIT’S ALL ARROUND US


OTHER MEASUREMENT PARAMETERSOTHER MEASUREMENT PARAMETERS OTHER MEASUREMENT PARAMETERSOTHER MEASUREMENT PARAMETERS

NOISE TEMPERATURE. PRESSURE. FLOW. CURRENT. MOVEMENT:-EXPANSION-VIBRATION. INFRA RED :- THERMOGRAPHY. WEAR ANALYSIS:- FEROGRAPHY SPECTROMETRIC OIL

ANALYSIS. VIBRATION


THEN WHY ONLY VIBRATION?THEN WHY ONLY VIBRATION?THEN WHY ONLY VIBRATION?THEN WHY ONLY VIBRATION?

All machines vibrate.

Every machinery defect generates its own unique vibration frequency.

An increase in vibration indicates of a developing problem.


CAUSES OF VIBRATIONCAUSES OF VIBRATIONCAUSES OF VIBRATIONCAUSES OF VIBRATION

Forces that change in direction with time (Rotating Unbalance).

Forces that change in amplitude or intensity with time (Motor Problems).

Frictional Forces (Rotor Rub).

Forces that cause impacts (Bearing Defects).

Randomly generated forces (Turbulence / Cavitation).


COMMON CAUSES OF VIBRATIONCOMMON CAUSES OF VIBRATIONCOMMON CAUSES OF VIBRATIONCOMMON CAUSES OF VIBRATION

Misalignment Unbalance Looseness Eccentricity Defective Bearings Resonance Electrical Problems Aerodynamic / Hydraulic Forces


BUT WHY STUDY VIBRATION?BUT WHY STUDY VIBRATION?BUT WHY STUDY VIBRATION?BUT WHY STUDY VIBRATION?

Increased machinery life

L10 Life = Estimated bearing life in hours RATINGB = Basic Dynamic Load LOADE = Equivalent applied Radial load (Dead load + live

load)


BUT WHY STUDY VIBRATION?BUT WHY STUDY VIBRATION?BUT WHY STUDY VIBRATION?BUT WHY STUDY VIBRATION?

Increased machinery life

If you RPM is 3000 and you reduce to 1500 then the brg life is doubled.

But if you reduce the load by 50% the the life is extended 8 times


LOAD IS DYNAMICLOAD IS DYNAMICLOAD IS DYNAMICLOAD IS DYNAMIC

Increased dynamic forces reduce life of bearing drastically

Amplitude of machinery vibration is directly proportional to the amount of dynamic forces generated

If generated force is lowered, the vibration is lowered and the machine life is increased


WHY MACHINES DETERIORATE?WHY MACHINES DETERIORATE?WHY MACHINES DETERIORATE?WHY MACHINES DETERIORATE?

Dynamic forces increase, cause increase in vibration– Wear, corrosion, or buildup of deposits

increases unbalance– Settling of foundation may increase

misalignment forces The stiffness of the machine reduces, thus

increasing vibration– Loosening or stretching of mounting bolts– Broken weld– Crack in the foundation– Deterioration of grouting


OTHER REASONSOTHER REASONS

Precision machine tools

–Quality products requireGood dimensional tolerancesGood surface finish quality

Human Annoyance

–Residences / Hospitals Low vibration in heating, ventilation,

air conditioning. machinery, etc...


SYSTEM CHARACTERISTICSSYSTEM CHARACTERISTICSSYSTEM CHARACTERISTICSSYSTEM CHARACTERISTICS

System characteristics which determine how a particular machine reacts to forces.

The Mass of the vibrating system.

The Stiffness of the vibrating system.

The Damping qualities of the system

– Vibration Force = Ma + Cv + Kx

» Vibration force is trying to cause vibration.

» M, K, and C are trying to minimise vibration.


FORCE DUE TO UNBALANCEFORCE DUE TO UNBALANCE

F(lbs) = 1.77 x (RPM/1000)2 x Ounces x Inches

OR

F(lbs) = .0625 x (RPM/1000)2 x Grams x Inches

Force is proportional to the square of the speed


EQUATION 1EQUATION 1EQUATION 1EQUATION 1

VIBRATION AMPLITUDE RESPONSE = DYNAMIC FORCE

DYNAMIC RESISTANCE

ANY VIBRATION CAN BE DEFINED BY THE PARTICULAR COMBINATION OF ANY VIBRATION CAN BE DEFINED BY THE PARTICULAR COMBINATION OF THESE THREE CHARACTERISTICSTHESE THREE CHARACTERISTICS

DYNAMIC RESISTANCE IS PROPORTIONAL TO THE AMOUNT OF DYNAMIC RESISTANCE IS PROPORTIONAL TO THE AMOUNT OF STIFFNESS, DAMPING AND MASS WITHIN THE SYSTEMSTIFFNESS, DAMPING AND MASS WITHIN THE SYSTEM


PREDICTIVE MAINTENANCE.PREDICTIVE MAINTENANCE.PREDICTIVE MAINTENANCE.PREDICTIVE MAINTENANCE.

THE USE OF GRAPHIC TRENDS OF SELECTED MEASUREMENT PARAMETERS AGAINST KNOWN

ENGINEERING LIMITS FOR THE PURPOSE OF:-

DETECTING, ANALYSING, CORRECTING & VERIFYING

MACHINERY DEFECTS,

BEFORE FAILURE OCCURS


PREDICTING PROBLEMS LIKE


UNBALANCEUNBALANCE


MISSALIGNMENTMISSALIGNMENT


BENT SHAFTBENT SHAFT


LOOSENESSLOOSENESS


BAD BEARINGSBAD BEARINGS


HYDRAULICHYDRAULIC FORCESFORCES


CONDITION MONITORINGCONDITION MONITORING

The assessment on a continuous or periodic The assessment on a continuous or periodic basis of the mechanical condition of basis of the mechanical condition of machinery, equipment and systems from machinery, equipment and systems from the observations and/or recordings of the observations and/or recordings of selected measurement parameters.selected measurement parameters.


THE FOUR PILLARSTHE FOUR PILLARSTHE FOUR PILLARSTHE FOUR PILLARSDetection Trending a machines vibration level to detect and quantify

any changes from the norm.Analysis When a significant change is detected the vibration is

analysed to determine the nature of the problemCorrection The advanced warning provided by the detection and

analysis enables corrective action to be prepared and scheduled.

Verification After correction new readings are obtained to ensure that

all defects have been eliminated and to establish new baseline characteristics.


MACHINE OPERATING CONDITIONS MACHINE OPERATING CONDITIONS MACHINE OPERATING CONDITIONS MACHINE OPERATING CONDITIONS

RUNNINGRUNNINGININ

RUNNINGRUNNINGININ NORMAL OPERATIONSNORMAL OPERATIONSNORMAL OPERATIONSNORMAL OPERATIONS

FAILURE

SHUT DOWNSHUT DOWN

WARNINGWARNING

LEADLEADTIMETIMELEADLEADTIMETIME

OIL OIL DEBRISDEBRIS

Bathtub CurveBathtub Curve


Amplitude

Displacement – Units are mils or microns(1 micron =

0.001mm or 0.039 mils.

Velocity – Units are in/sec or mm/sec

Acceleration – Units “g”. Where 1g=32.2ft/sec2 or 9.81 m/sec2.

Spike Energy – gSE, HFD,SEE

Frequency – Hertz(CPS), CPM or Orders Phase

Relative Motion – Degrees or Clock

CHARACTERISTICS OF VIBRATIONCHARACTERISTICS OF VIBRATIONCHARACTERISTICS OF VIBRATIONCHARACTERISTICS OF VIBRATION


WHAT IS A TIME WAVE FORM?WHAT IS A TIME WAVE FORM?WHAT IS A TIME WAVE FORM?WHAT IS A TIME WAVE FORM?

TIMEAM

PL

ITU

DE


TIME WAVEFORM SIMPLIFIEDTIME WAVEFORM SIMPLIFIED

Paper feeds as the block oscillates up and down


TIME WAVEFORMTIME WAVEFORM


WHAT IS VIBRATION AMPLITUDE?WHAT IS VIBRATION AMPLITUDE?WHAT IS VIBRATION AMPLITUDE?WHAT IS VIBRATION AMPLITUDE?

The amount of motion in the system.


VIBRATION AMPLITUDEVIBRATION AMPLITUDE

Magnitude of the vibration signal

– Displacement (Mils OR microns)

– Velocity (in/s OR mm/sec)

– Acceleration (g’s OR mm/sec2)

– Spike Energy (g/SE)

PEAK

VIBRATION SPECIALIST 1 - EXAMPLEVIBRATION SPECIALIST 1 - EXAMPLEVIBRATION SPECIALIST 1 - EXAMPLEVIBRATION SPECIALIST 1 - EXAMPLE

For the time waveform shown in Figure 1, what is the “PEAK AMPLITUDE” for this vibration?

A) 2.0 mm/sB) 0.2 mm/sC) 3.0 mm/s D) 4.0 mm/s

AmplitudeAmplitude(mm/s)(mm/s)

.1

TimeTime(m Secs)(m Secs).2 .3 .4 .5 .6 .7

Figure 1

2

1

0

-1

-2


TIME VARIABLESTIME VARIABLES

X = Displacement at a given time (t)D = Peak Displacement = Angular Displacement = Angular Velocity (Frequency)

= t

X = D sin (t) DISPLACEMENT

V = D cos (t) VELOCITY

A = - 2 D sin (t) ACCELERATION

D


DISPLACEMENT

VELOCITYVELOCITY

ACCELERATIONACCELERATION

TIME

TIME

TIME

EQUATIONS REWRITTENEQUATIONS REWRITTEN

DISPLACEMENT

X = A sin (t)

VELOCITY

V = A sin (t + 90°)

Directly proportional to frequency

ACCELERATION

A = A sin (t + 180°)Proportional to frequency squared


Vibration DisplacementVibration Displacement(mils or microns peak-to-peak)(mils or microns peak-to-peak)

Displacement is most easily understood

The problem with Displacement

– If vibration is not simple, then charts cannot be used for displacement

» 1 mil 1800 CPM - unbalance – FAIR ( ref pg 2.16)

» 0.5 mil 3600 CPM - misalignment - FAIR

» DON’T combine to FAIR

Severity is judged by Displacement and Frequency


Vibration VelocityVibration Velocity(in/s or mm/s rms)(in/s or mm/s rms)

Fatigue = Displacement * Frequency.

Velocity = Displacement * Frequency

– Thus, Velocity and Fatigue are equivalent.

Most machines fail due to Fatigue

– Velocity takes frequency and displacement into account (Severity Charts)

– Valid whether simple or complex vibration.

Overall velocity tells severity of vibration


Vibration VelocityVibration Velocity(in/s or mm/s rms)(in/s or mm/s rms)

Peak value is used in USA

RMS value is used internationally.

90 degrees out of phase with Displacement

Period

-1.5

-1

-0.5

0

0.5

1

1.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time

Dis

plac

emen

t

Period

-1

-0.5

0

0.5

1

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time

Dis

plac

emen

t

Period

TIME

VE

LO

CIT

Y

Maximum Velocity

Minimum Velocity

Minimum Velocity


Overall Alarm ChartOverall Alarm ChartM A C H I N E T Y P E G O O D F A I R A L A R MC o o l i n g T o w e r D r i v e s

L o n g H o l l o w D r i v e S h a f t 0 - . 3 7 5 . 3 7 5 - . 6 0 0 . 6 0 0C l o s e C o u p l e d B e l t D r i v e 0 - . 2 7 5 . 2 7 5 - . 4 2 5 . 4 2 5C l o s e C o u p l e d D i r e c t D r i v e 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0

C o m p r e s s o r sR e c i p r o c a t i n g 0 - . 3 2 5 . 3 2 5 - . 5 0 0 . 5 0 0R o t a r y S c r e w 0 - . 2 7 5 . 2 7 5 - . 4 2 5 . 4 2 5C e n t r i f u g a l w i t h o r w i t h o u t E x t e r n a l G e a r b o x 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0C e n t r i f u g a l - I n t e g r a l G e a r ( A x i a l M e a s . ) 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0C e n t r i f u g a l - I n t e g r a l G e a r ( R a d i a l M e a s . ) 0 - . 1 5 0 . 1 5 0 - . 2 5 0 . 2 5 0

B l o w e r s ( F a n s )L o b e - T y p e R o t a r y 0 - . 3 0 0 . 3 0 0 - . 4 5 0 . 4 5 0B e l t - D r i v e n B l o w e r s 0 - . 2 7 5 . 2 7 5 - . 4 2 5 . 4 2 5G e n e r a l D i r e c t D r i v e F a n s ( w i t h C o u p l i n g ) 0 - . 2 5 0 . 2 5 0 - . 3 7 5 . 3 7 5P r i m a r y A i r F a n s 0 - . 2 5 0 . 2 5 0 - . 3 7 5 . 3 7 5L a r g e F o r c e d D r a f t F a n s 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0L a r g e I n d u c e d D r a f t F a n s 0 - . 1 7 5 . 1 7 5 - . 2 7 5 . 2 7 5S h a f t - M o u n t e d I n t e g r a l F a n ( E x t e n d e d M o t o r S h a f t ) 0 - . 1 7 5 . 1 7 5 - . 2 7 5 . 2 7 5V a n e - A x i a l F a n s 0 - . 1 5 0 . 1 5 0 - . 2 5 0 . 2 5 0

M o t o r / G e n e r a t o r S e t sB e l t - D r i v e n 0 - . 2 7 5 . 2 7 5 - . 4 2 5 . 4 2 5D i r e c t C o u p l e d 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0

C h i l l e r sR e c i p r o c a t i n g 0 - . 2 5 0 . 2 5 0 - . 4 0 0 . 4 0 0C e n t r i f u g a l ( O p e n - A i r ) - M o t o r & C o m p . S e p a r a t e 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0C e n t r i f u g a l ( H e r m e t i c ) - M o t o r & I m p e l l e r s I n s i d e 0 - . 1 5 0 . 1 5 0 - . 2 2 5 . 2 2 5

L a r g e T u r b i n e / G e n e r a t o r3 6 0 0 R P M T u r b i n e / G e n e r a t o r s 0 - . 1 7 5 . 1 7 5 - . 2 7 5 . 2 7 51 8 0 0 R P M T u r b i n e / G e n e r a t o r s 0 - . 1 5 0 . 1 5 0 - . 2 2 5 . 2 2 5

C e n t r i f u g a l P u m p sV e r t i c a l P u m p s ( 1 2 ' - 2 0 ' H e i g h t ) 0 - . 3 7 5 . 3 7 5 - . 6 0 0 . 6 0 0V e r t i c a l P u m p s ( 8 ' - 1 2 ' H e i g h t ) 0 - . 3 2 5 . 3 2 5 - . 5 0 0 . 5 0 0V e r t i c a l P u m p s ( 5 ' - 8 ' H e i g h t ) 0 - . 2 5 0 . 2 5 0 - . 4 0 0 . 4 0 0V e r t i c a l P u m p s ( 0 ' - 5 ' H e i g h t ) 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0G e n e r a l P u r p o s e H o r i z o n t a l P u m p ( D i r e c t C o u p l e d ) 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0B o i l e r F e e d P u m p s 0 - . 2 0 0 . 2 0 0 - . 3 0 0 . 3 0 0H y d r a u l i c P u m p s 0 - . 1 2 5 . 1 2 5 - . 2 0 0 . 2 0 0

M a c h i n e T o o l sM o t o r 0 - . 1 0 0 . 1 0 0 - . 1 7 5 . 1 7 5G e a r b o x I n p u t 0 - . 1 5 0 . 1 5 0 - . 2 2 5 . 2 2 5G e a r b o x O u t p u t 0 - . 1 0 0 . 1 0 0 - . 1 7 5 . 1 7 5S p i n d l e s : a . R o u g h i n g O p e r a t i o n s 0 - . 0 7 5 . 0 7 5 - . 1 2 5 . 1 2 5

b . M a c h i n e F i n i s h i n g 0 - . 0 5 0 . 0 5 0 - . 0 7 5 . 0 7 5c . C r i t i c a l F i n i s h i n g 0 - . 0 3 0 . 0 3 0 - . 0 5 0 . 0 5 0


Interpreting ChartsInterpreting Charts

Good and Below - Satisfactory operation– No significant problems

Fair - Minor problems– Conduct analysis to find problem

– Decrease interval

– Schedule correction, arrange parts and labour

Rough and Above - Analyse immediately– Shutdown as soon as possible


Overall Velocity GuidelinesOverall Velocity Guidelines


Vibration AccelerationVibration Acceleration(g’s peak)(g’s peak)

Peak value is used 90 degrees out of

phase with Velocity, 180 degrees out with Displacement

1g = 9810mm/s/s = 386 in/s/s Preferable for high frequency vibration Chart looks at 18000-600000 CPM range

Period

-1

-0.5

0

0.5

1

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time

Dis

plac

emen

t

Period

-1.5

-1

-0.5

0

0.5

1

1.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time

Dis

plac

emen

t

Period

TIME

Dis

pla

cem

ent

Minimum Acceleration

Maximum Acceleration

Maximum Acceleration


Acceleration Severity ChartAcceleration Severity Chart


WHEN TO USE D / V / A WHEN TO USE D / V / A WHEN TO USE D / V / A WHEN TO USE D / V / A

Amplitude Failure Units Frequency

Displacement Stress mils pk-pk < 600 CPM

Velocity Fatigue in/s pk 600-120K CPM

Acceleration Force g’s pk >120K CPM

Fatigue causes most failures, but stress and force can also cause failures.

Velocity can go as high as 240000 CPM.

F (cpm)60

6006,000

60,000600,000

D (um)100.00

10.001.000.100.01

V (mm/s)0.3140.3140.3140.3140.314

A (g)0.00020.0020.0200.2012.012

CONTOURS OF EQUAL SEVERITYCONTOURS OF EQUAL SEVERITYCONTOURS OF EQUAL SEVERITYCONTOURS OF EQUAL SEVERITY

LOG AMPLITUDE(um, mm/s, g)

LOG FREQUENCY (CPM)

DisplacementDisplacement

VelocityVelocity

AccelerationAcceleration

Force Indicator

Fatigue Indicator

Stress Indicator

60 600 6K 60K 600K

10 um

.314 mm/s

.002 g

.20 g

.314 mm/s

.1 um

FORMULA FOR CONVERSIONFORMULA FOR CONVERSIONFORMULA FOR CONVERSIONFORMULA FOR CONVERSION

WhereWhere : A = Acceleration (g pk), V = Velocity (mm/s pk), D = Displacement (um pk-pk)

D = 2 V x 103 D = 2 g x A x 106

= 19.10 x 103 V / RPM (um pk-pk) = 1.79 x 109 A / (RPM)2 (um pk-pk)

V = 0.5 D x 10-3 V = g x A x 103

= 52.36 x 10-6 D x RPM (mm/s pk) = 93.68 x 103 A / RPM (mm/s pk)

A = 0.5 D x 10-6 A = V x 10-3

= 0.559 x 10-9 D x (RPM)2 (g pk) = 10.67 x 10-6 V x RPM (g pk)

2 RPM

60

602 RPM

602 RPM

2

2 RPM

60

602 RPM

2 RPM

60

2

g g


DISPLACEMENT - How far it moves(Microns or Mils)

VELOCITY - How fast it moves(mm/sec or in/sec)

ACCELERATION - How quickly velocitychanges. (g)

MEASUREMENT PARAMETERS,MEASUREMENT PARAMETERS,MEASUREMENT PARAMETERS,MEASUREMENT PARAMETERS,


DISPLACEMENT

VELOCITYVELOCITY

ACCELERATIONACCELERATION

TIME

TIME

TIME

RELATIONSHIP RELATIONSHIP


WHY IS VELOCITY NORMALLY USED? WHY IS VELOCITY NORMALLY USED? WHY IS VELOCITY NORMALLY USED? WHY IS VELOCITY NORMALLY USED?

IT GIVES EQUAL AMPLITUDE WEIGHTING TO ALL VIBRATION FREQUENCIES.

MOST ROTATING MACHINES PRODUCE FREQUENCIES BETWEEN 6OOCPM TO 120KCPM WHERE VELOCITY IS THE MOST RESPONSIVE

IT IS THE ONLY MEASUREMENT PARAMETER WHERE THE OVERALL VIBRATION LEVEL CAN BE APPLIED DIRECTLY TO A STANDARD OF VIBRATION SEVERITY. IE:-WHEN THE FREQUENCIES OF THE VIBRATION ARE UNKNOWN.


Comparative SpectrumsComparative SpectrumsDISPLACEMENT


Comparative SpectrumsComparative Spectrums

VELOCITY


Comparative SpectrumsComparative SpectrumsACCELERATION


T.C RATHBONE SEVERITY CHARTT.C RATHBONE SEVERITY CHARTT.C RATHBONE SEVERITY CHARTT.C RATHBONE SEVERITY CHART


MIL VIBRATION SEVERITY CHARTMIL VIBRATION SEVERITY CHARTMIL VIBRATION SEVERITY CHARTMIL VIBRATION SEVERITY CHART


IRD VIBRATION SEVERITY CHARTIRD VIBRATION SEVERITY CHARTIRD VIBRATION SEVERITY CHARTIRD VIBRATION SEVERITY CHARTPlotted Point 1800

1.0000

Condition

FAIR

Constant RPM Lines 1200 12000.001 0.21800 18000.001 0.23600 36000.001 0.2

Derived Values 1.0000 0.094210.6111 1.000021.7284 2.1500

0

0.01

0.1

1

10

1 #REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

#REF!

Ext.Smooth

VerySmooth

Smooth

VeryGood

Good

Fair

SlightlyRough

Rough

VeryRough

1200

1800

3600

DISPLACEMENT

0.001

0.010

0.100

1.000

10.000

100 1000 10000 100000

VIBRATION FREQUENCY - CPM

VIB

RA

TIO

N D

ISP

LA

CE

ME

NT

- M

ILS

PE

AK

TO

PE

AK


MACHINE TOOL SEVERITY CHARTMACHINE TOOL SEVERITY CHARTMACHINE TOOL SEVERITY CHARTMACHINE TOOL SEVERITY CHART


INTERPRETING CHARTSINTERPRETING CHARTSINTERPRETING CHARTSINTERPRETING CHARTS

Good and Below - Satisfactory operation

–No significant problems

Fair to Slightly Rough - Minor problems

–Conduct analysis to find problem

–Decrease interval

–Schedule correction, arrange parts and labour

Rough and Above - Analyse immediately

–Shutdown as soon as possible


Factors Affecting AmplitudeFactors Affecting Amplitude

Whether Mounting is rigid or on isolators

What machine does (i.e. Hammer Mills).

Damping factor.

Mass of the machine.

Whether single frequency of multiple frequencies are in action.


Determining Vibration LimitsDetermining Vibration Limits

If unsure what vibration level is normal

– Compare to identical machines

» If higher than average, analyse

– Check for increasing levels of vibration


Determining Vibration LimitsDetermining Vibration Limits

Experience Manufacturers recommendations (Warranty) Published corporate specifications (Committees) Vibration Severity Charts Overall Alarm Charts Comparison of similar equipment If long term trend on a given machine shows a constant

level, this can be considered normal for that machine


BALANCING FORCESBALANCING FORCESBALANCING FORCESBALANCING FORCES

FORCE (ACCELERATION)

DAMPING (VELOCITY)

RIGIDITY(DISPLACEMENT)

MACHINE STARTING FROM REST




DAMPING (VELOCITY)


MACHINE SPEED 10%




DAMPING (VELOCITY)


MACHINE SPEED 30%




DAMPING (VELOCITY)


MACHINE SPEED 50 %




DAMPING (VELOCITY)


MACHINE SPEED 70%




DAMPING (VELOCITY)


MACHINE IN RESONANCE

90 DEG90 DEG


VIBRATIONVIBRATION

How much is too much?


FREQUENCYFREQUENCYFREQUENCYFREQUENCY

DISPLACEMENT AND FREQUENCY FROM THE TIME WAVEFORM

DISPLACEMENT

TIME

Period(T)(1 complete cycle)

Neutral Position

Upper Limit

Lower Limit

Frequency =1

T=

Cycles

Second

1

Period=


VIBRATION FREQUENCY.VIBRATION FREQUENCY.VIBRATION FREQUENCY.VIBRATION FREQUENCY.

THE TIME REQUIRED TO COMPLETE ONE FULL CYCLE OF VIBRATION IS CALLED THE PERIOD. i.e.:-

IF ONE PERIOD IS COMPLETED IN ONE FIFTH OF A SECOND, THE VIBRATION FREQUENCY WOULD BE 5 CYCLES PER SECOND (5 Hz) OR 300 CYCLES PER MINUTE (300 CPM).

FREQUENCY IS THUS

THE RECIPROCAL OF THE PERIOD.


Vibration BasicsVibration BasicsVibration BasicsVibration Basics

Which Frequency Units do we use Hertz or CPM ?

– Dedicated after Heinrich Rudolf Hertz(Discovered electromagnetic radiation)

Why do we need to know the frequency of vibration ?


Significance of FrequencySignificance of Frequency

Essential for pinpointing the cause of a machine problem

Most vibration problems exhibit frequencies related to the rotational speed(s) of the machine

Process of elimination to narrow down the exact machine fault

Problems not always exact multiple of rpm



1 Minute

IF IT TAKES ONE MINUTE TO COMPLETE ONE CYCLE THENIF IT TAKES ONE MINUTE TO COMPLETE ONE CYCLE THEN



1 CYCLE PER MINUTE

1 CPM



1 Minute

IF IT TAKES ONE MINUTE TO COMPLETE THREE CYCLE THENIF IT TAKES ONE MINUTE TO COMPLETE THREE CYCLE THEN



3 CYCLES PER MINUTE

3 CPM



10 seconds

IF IT TAKES TEN SECONDS TO COMPLETE THREE CYCLE THENIF IT TAKES TEN SECONDS TO COMPLETE THREE CYCLE THEN



18 CYCLES PER MINUTE

18 CPM



0.5 Seconds

IF IT TAKES 0.5 SECONDS TO COMPLETE TWO CYCLE THENIF IT TAKES 0.5 SECONDS TO COMPLETE TWO CYCLE THEN



240 CYCLES PER MINUTE

240 CPM



CPM / 60 = CPS

e.g. 240 CPM = 4 CPS

CPS X 60 = CPM

CPS = Hertz (Hz)



1200 CPM = ? Hz



1200 CPM = 20 Hz



1200 CPM = 20 Hz

60,000 CPM = ? Hz



1200 CPM = 20 Hz

60,000 CPM = 1000Hz



1200 CPM = 20 Hz

60,000 CPM = 1000Hz

120,000 CPM = ? Hz



1200 CPM = 20 Hz

60,000 CPM = 1000Hz

120,000 CPM = 2000Hz



1200 CPM = 20 Hz

60,000 CPM = 1000Hz

120,000 CPM = 2000Hz

1500 Hz = ? CPM



1200 CPM = 20 Hz

60,000 CPM = 1000Hz

120,000 CPM = 2000Hz

1500 Hz = 90,000 CPM



1200 CPM = 20 Hz

60,000 CPM = 1000Hz

120,000 CPM = 2000Hz

1500 Hz = 90,000 CPM

500 CPS = ? CPM



1200 CPM = 20 Hz

60,000 CPM = 1000Hz

120,000 CPM = 2000Hz

1500 Hz = 90,000 CPM

500 CPS = 30,000 CPM



From the time waveform calculate the frequency of the vibration in CPM

A) 100B) 333C) 2,000D) 20,000

AmplitudeAmplitude(mm/s)(mm/s)

0 3 6 9 12

TimeTime(m Sec)(m Sec)


Common Machine Defect FrequenciesCommon Machine Defect Frequencies

1xRPM - Unbalance 2xRPM - Misalignment or Looseness Electrical Line Frequency Blade or Vane Pass Frequency BPF = # of vanes or

blades x RPM Gear Mesh Frequency GMF = # of Gear Teeth X gear

RPM Bearing Defect Frequencies


FrequencyIn TermsOf RPM Most Likely Causes Other Possible Causes & Remarks

1 x RPM Unbalance 1) Eccentric journals, gears or pulleys2) Misalignment or bent shaft - If high axial vibration3) Bad Belts - If RPM of belt4) Resonance5) Reciprocating forces6) Electrical problems7) Looseness8) Distortion - soft feet or piping strain

2 x RPM Mechanical 1) Misalignment - if high axial vibrationLooseness 2) Reciprocating forces

3) Resonance4) Bad belts - if 2 x RPM of belt

3 x RPM Misalignment Usually a combination of misalignment and excessive axial clearances (looseness).

Less than Oil Whirl (less 1) Bad drive belts1 x RPM than 1/2 RPM 2) Background vibration

3) Sub-harmonic resonance4) "Beat" Vibration

Synchronous Electrical Common electrical problems include broken rotor bars, eccentric(A.C. Line Problems rotor unbalanced phases in poly-phase systems, unequalFrequency) air gap.2 x Synch. Torque Pulses Rare as a problem unless resonance is excitedFrequencyMany Times RPM Bad Gears Gear teeth times RPM of bad gear(Harmonically Aerodynamic Forces Number of fan blades times RPMRelated Freq.) Hydraulic Forces Number of impeller vanes times RPM

Mechanical Looseness May occur at 2, 3, 4 and sometimes higher harmonics ifsevere looseness

Reciprocating ForcesHigh Frequency Bad Anti-Friction 1) Bearing vibration may be unsteady - amplitude and frequency(Not Harmonically Bearings 2) Cavitation, recirculation and flow turbulence cause random,Related) high frequency vibration

3) Improper lubrication of journal bearings (Friction excited vibration)4) Rubbing

Relationship of various frequenciesRelationship of various frequencies


Real Vibration is ComplexReal Vibration is Complex


ACTUAL VIBRATIONACTUAL VIBRATIONACTUAL VIBRATIONACTUAL VIBRATION

ImbalanceRolling Element Bearing

Coupling chatter

Gearmesh

Time

Resultant Complex Waveform


Real Vibration is ComplexReal Vibration is Complex


Resulting Spectrum (FFT)Resulting Spectrum (FFT)


One More ExampleOne More Example


Resulting Spectrum (FFT)Resulting Spectrum (FFT)


Spectrum TermsSpectrum Terms Predominant Frequency - Highest amplitude.

Subsynchronous Frequency - Below 1xRPM.

Fundamental Frequency - Lowest frequency associated with a particular problem

Harmonic Frequency - Exact multiple of a fundamental frequency

Order Frequency - Same as Harmonic

Subharmonic Frequency - Exact sub-multiple of a fundamental frequency


TIME DOMAINTIME DOMAINTIME DOMAINTIME DOMAIN

TIME DOMAIN

RESULTS IN


TIME DOMAINTIME DOMAINTIME DOMAINTIME DOMAIN

TIME DOMAIN

COMPLEX WAVEFORMCOMPLEX WAVEFORM


FREQUENCY AND TIME DOMAINSFREQUENCY AND TIME DOMAINSFREQUENCY AND TIME DOMAINSFREQUENCY AND TIME DOMAINS

Time Domain(Sec or Min) Frequency Domain

(CPM or Hertz)

Amplitude

Complex Waveform

Simple Wave forms

FrequencySpectrumPlot

TMAX

FMAX

1X1X3X3X

5X5X

9X9X


WHAT IS AN FFTWHAT IS AN FFTWHAT IS AN FFTWHAT IS AN FFT Fast Fourier Transform.

Also known as a Spectrum or as the Frequency domain.

Graph of Vibration Amplitude vs. Frequency.

Also known as Signature

All frequencies in a chosen range are separated and displayed as individual peaks each having its own amplitude.

Most useful tool for analysis.

Named after French mathematician Baron Jean Baptist Joseph Fourier


FFTFFTFFTFFT


For the sine wave shown in Figure 1, calculate and draw a representation of the frequency spectrum on Figure 2 (Amplitude not important).

VelocityVelocity(mm/s)(mm/s)

TimeTime(m Secs)(m Secs)

VelocityVelocity(mm/s)(mm/s)

Figure 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

FrequencyFrequency(CPM)(CPM)

15K 30K 45K 60K 75K 90K

Figure 2


PRACTICALSPRACTICALSPRACTICALSPRACTICALS

TAKING AMPLITUDE READINGS.

CAPTURING TIME WAVEFORM.

LOOKING INTO AN FFT.

HENCE SPLIT INTO MAY BE 3-4 IN EACH GROUP.


The angular reference --at a given instance in time -- of a moving part--to a fixed point.

The angular reference--at a given instance in time--of two moving parts to each other.

WHAT IS PHASE?WHAT IS PHASE?WHAT IS PHASE?WHAT IS PHASE?


PhasePhase

Phase is a means of determining the Relative motion of two or more vibrating machine parts

Phase readings only have meaning when compared to other phase readings with a common reference


Phase (continued)Phase (continued)

Used as an analysis tool to pinpoint between problems that occur at 1xRPM

– Unbalance, Bent Shaft, Misalignment, Looseness, Resonance, Eccentricity

Measured with a strobe light or digitally

Essential for Balancing

Distortion Studies

– Shows the distortion of the machine


Relative PhaseRelative Phase

Comparative phase readings show “how” the machine is vibrating



A=180° B=180°

A

B



A=180° B= ?


A=180° B= 0°


A

B

180°


Relative PhaseRelative PhaseRelative PhaseRelative Phase

Comparative phase readings show “how” the machine is vibrating


Relative PhaseRelative Phase Obtained by moving transducer to different measurement

locations while keeping the same speed reference Amplitude and phase are recorded at points of interest


Phase Obtained with a StrobePhase Obtained with a Strobe

Strobe Light is triggered by the vibration signal similar to the way a timing light is fired by the #1 spark plug

Rotating reference mark appears frozen and its position is compared to the stationary reference

If predominant vibration that pickup “sees” is not at running speed, then multiple reference marks will appear


HOW A STROBE IS CONNECTEDHOW A STROBE IS CONNECTEDHOW A STROBE IS CONNECTEDHOW A STROBE IS CONNECTED


Phase Obtained DigitallyPhase Obtained Digitally

Photocell or Laser Tachometer is pointed at the rotating shaft which must have reflective tape

Tape Interrupts Laser and creates a signal which is sent to the vibration analyser which compares it against an arbitrary time waveform position.


DIGITAL PHASE PHOTOCELL/ LASTACH DIGITAL PHASE PHOTOCELL/ LASTACH


ADVANTAGES OF PHOTOCELL/LASERADVANTAGES OF PHOTOCELL/LASERADVANTAGES OF PHOTOCELL/LASERADVANTAGES OF PHOTOCELL/LASER

Digitally obtained phase readings are generally more accurate than strobe readings.

Orders of running speed can easily be obtained by placing multiple strips of tape uniformly spaced

MACHINE TRAIN MISALIGNMENTMACHINE TRAIN MISALIGNMENTMACHINE TRAIN MISALIGNMENTMACHINE TRAIN MISALIGNMENT

Note: All phase readings corrected for pickup direction

TURBINE G/B HP COMP LP COMP

AXIAL PHASE(degrees)

0 5 15 18 198 21510 12 22 24 210 22012 10 20 22 208 218 8 6 16 20 200 210

AMPLITUDE. HOW MUCH.

FREQUENCY. HOW OFTEN.

PHASE. WHEN.

VIBRATION CHARACTERISTICSVIBRATION CHARACTERISTICSVIBRATION CHARACTERISTICSVIBRATION CHARACTERISTICS


LUNCH


SPIKE ENERGY FOR REBSPIKE ENERGY FOR REBSPIKE ENERGY FOR REBSPIKE ENERGY FOR REB


DETECTION

ANALYSIS

CORRECTION

VERIFICATION

BASIS FOR PMPBASIS FOR PMPBASIS FOR PMPBASIS FOR PMP


Spike EnergyTM Spectrum Analysis. (Demodulation)

Low Frequency Measurement.

RECENT ADVANCESRECENT ADVANCESRECENT ADVANCESRECENT ADVANCES


Product Faults - 30.1%– Faulty workmanship

– Design, Planning etc..

– Wrong Materials

Operational faults- 65.9%– Mishandling, Faulty Maintenance

– Rapid wear due to overloading

External Influences - 4%– False Brinneling Electrical Arcing etc..

WHY DOES A BEARING FAILWHY DOES A BEARING FAILWHY DOES A BEARING FAILWHY DOES A BEARING FAIL


SPIKE ENERGY SPIKE ENERGY TMTM

What is it ? How is it measured ? Why does it work ? Where is it used ? How do we assess levels ? Can it be analysed in the

frequency domain ?


SPIKE ENERGY. WHAT IS IT?SPIKE ENERGY. WHAT IS IT?

A measurement parameter designed to

detect low amplitude transient impacts

generated within the Audiosonic/Ultrasonic

frequency range by microscopic surface

flaws inrolling element bearings and gears.


SPIKE ENERGYSPIKE ENERGYSPIKE ENERGYSPIKE ENERGY

Special amplitude parameter obtained using special filters.

First indication of a problem in the rolling element bearing.

Special circuit detects very high frequency, short duration pulses of energy generated by defects such as nicks on the raceway.


HOW IS IT MEASURED ?HOW IS IT MEASURED ?

The acceleration signal is processed via a high pass filter and a peak detection circuit to produce a numerical value which is the product of :- The Number and amplitude ( Intensity ) of the impacts in a unit of time. The value is expressed in units of gSE

TM


CHARACTERISTICS OF SPIKE ENERGYCHARACTERISTICS OF SPIKE ENERGY

Detects audiosonic/ultrasonic frequencies. It’s a filtered reading which only responds to

frequencies above the range of most machine vibrations. (300kcpm.)

It is localised to the area of source It is defect orientated to impact energy.

FOUR FACTORS MAKE IT EFFECTIVE!FOUR FACTORS MAKE IT EFFECTIVE!


ROOT MEAN SQUARE (RMS)ROOT MEAN SQUARE (RMS)ROOT MEAN SQUARE (RMS)ROOT MEAN SQUARE (RMS)

ISO Standard 2372

– ...vibration velocity has been selected as the significant parameter for characterising the severity of machine vibration

– ...the RMS value of the oscillating velocity is used to measure vibration severity

Instruments measure RMS RMS is a measure of energy and is the average vibration

amplitude Roughly equals to 0.707xpeak reading


VISUAL CONCEPT OF RMS AVERAGINGVISUAL CONCEPT OF RMS AVERAGINGVISUAL CONCEPT OF RMS AVERAGINGVISUAL CONCEPT OF RMS AVERAGING

Because vibration is Complex, two waves that have the same peak value can actually be quite different in RMS because of the Superposition Principle


BEARING DEFECTSBEARING DEFECTSBEARING DEFECTSBEARING DEFECTS

Bearing defects cause high frequencies with comparatively low amplitude

Even advanced stages of failure in bearings may show little increase in displacement, velocity, or acceleration


SPIKES CAN GO UNDETECTEDSPIKES CAN GO UNDETECTEDSPIKES CAN GO UNDETECTEDSPIKES CAN GO UNDETECTED

Short duration spikes or pulses are covered up by

– The RMS technique itself

– Low frequency vibration (such as unbalance or misalignment)


SPIKE ENERGY CIRCUITSPIKE ENERGY CIRCUITSPIKE ENERGY CIRCUITSPIKE ENERGY CIRCUIT

Because vibration is very high, circuit utilises an acceleration signal.

‘Band - Pass’ filters out frequencies

– Below 300K CPM (5 kHz)

– Above 3 Million CPM (50 kHz)

A true Peak-to-Peak value detecting circuit is incorporated because spike pulse signals have such low RMS values


BAND PASS FILTER FOR SPIKE ENERGYBAND PASS FILTER FOR SPIKE ENERGYBAND PASS FILTER FOR SPIKE ENERGYBAND PASS FILTER FOR SPIKE ENERGY


SIGNAL PROCESSINGSIGNAL PROCESSINGSIGNAL PROCESSINGSIGNAL PROCESSING


RELEVENCE OF THE FILTERRELEVENCE OF THE FILTERRELEVENCE OF THE FILTERRELEVENCE OF THE FILTER


INTELLIGENT CIRCUITINTELLIGENT CIRCUITINTELLIGENT CIRCUITINTELLIGENT CIRCUIT


SEVERITY CHART FOR SPIKE ENERGYSEVERITY CHART FOR SPIKE ENERGYSEVERITY CHART FOR SPIKE ENERGYSEVERITY CHART FOR SPIKE ENERGY


SPIKE ENERGY CONSIDERATIONSSPIKE ENERGY CONSIDERATIONSSPIKE ENERGY CONSIDERATIONSSPIKE ENERGY CONSIDERATIONS

Readings need to be directly on bearing.

Minimise interfaces.

Consistency between measurements Always use same accelerometer.

Transducer mounting makes a difference.

Overall levels should be trended.


FACTORS AFFECTING SPIKE ENERGYFACTORS AFFECTING SPIKE ENERGYFACTORS AFFECTING SPIKE ENERGYFACTORS AFFECTING SPIKE ENERGY

Load

Lubrication

Temperature

Type of Defect

Distance to Measurement Point

Transducer Mounting Method


MOUNTING MAKES A BIG DIFFERENCEMOUNTING MAKES A BIG DIFFERENCEMOUNTING MAKES A BIG DIFFERENCEMOUNTING MAKES A BIG DIFFERENCE


MOUNTING MAKES A BIG DIFFERENCEMOUNTING MAKES A BIG DIFFERENCEMOUNTING MAKES A BIG DIFFERENCEMOUNTING MAKES A BIG DIFFERENCE

Sharp pulses and random ultrasonic vibrations excite the accelerometers natural frequency regardless of mounting method, but stud mounting gives the highest amplitude response and is most repeatable.

Energy is reflected (60-80%) at each interface depending on the sharpness of the pulse, material differences, fits/clearances, etc.

Potential hand pressure variation with use of probe.

Heavy magnet is better than light magnet


MOUNTING OF ACCELEROMETERSMOUNTING OF ACCELEROMETERSMOUNTING OF ACCELEROMETERSMOUNTING OF ACCELEROMETERS

When attaching any pickup to a threaded stud or magnet ensure that the surfaces are clean and flat and that a smear of silicon grease is used to ensure good contact. Don’t over tighten.

A probe will miss bearing faults & worse may produce phantom data in the bearing defect range due to natural frequency of the probe being excited


MOUNTING METHODMOUNTING METHODMOUNTING METHODMOUNTING METHOD

MountingMaximum

AcceptableFrequency (cpm)

Rating

Stud 975 000 Best

Adhesive 540 000 Very good

Magnet 450 000 Good

Quick Connect 360 000 Quite good

Hand-held 48 000 Poor


FREQUENCY LIMITATIONS ACCELFREQUENCY LIMITATIONS ACCELFREQUENCY LIMITATIONS ACCELFREQUENCY LIMITATIONS ACCEL

Hand Held 9” Probe 30,000 cpm

Small Magnet 20,000 cpm

Large Magnet 240,000 cpm

Hand Held 300,000 cpm

Threaded Stud >600,000 cpm

Ensure surfaces are clean and use a smear of silicon grease to improve transmission of vibration


FREQUENCY LIMITATION FOR VEL FREQUENCY LIMITATION FOR VEL FREQUENCY LIMITATION FOR VEL FREQUENCY LIMITATION FOR VEL

Vice grip Pliers 7,200 cpm

Hand Held 9” Probe 16,000 cpm

Large Magnet 37,000 cpm

Hand Held 60,000 cpm

Threaded Stud 90,000 cpm

Ensure surfaces are clean and use a smear of silicon grease to improve transmission of vibration


ADDITIONAL SOURCES OF gSEADDITIONAL SOURCES OF gSEADDITIONAL SOURCES OF gSEADDITIONAL SOURCES OF gSE

Gear Tooth Impacts Cavitation and

Recirculation Inadequate Lubrication Rubbing Loose or Rattling Parts

Commutator/Brush Noise V-Belt Seams, Chunks Toothed Belts

Machining, Grinding (Chatter)High Pressure FlowCavitation.High pressure steam and air flow.Turbulence in liquids and air.Rubbing. (Seals, rotors, belts, guards etc.)Impact excitation. (Looseness or inherent in the machines operation.)Electrical arcing.


SPIKE ENERGY DOES NOT RESPOND TOSPIKE ENERGY DOES NOT RESPOND TOSPIKE ENERGY DOES NOT RESPOND TOSPIKE ENERGY DOES NOT RESPOND TO

Unbalance Misalignment Bent shaft Electrical problems Eccentric rotors Resonance Structural looseness/weakness Beat vibration problems


ReviewReview gSE should be used primarily as a trending tool.

Absolute values should be used with caution.

Tables of absolute values developed from empirical data should only be used as guidelines.

gSE detects defects which may, or may not be detected by other measurement parameters.


VELOCITY & gSE RELATIONSHIPVELOCITY & gSE RELATIONSHIP

0

0.2

0.4

0.6

0.8

1

1.2

Jan Feb Mar Apr May Jun Jul Aug Sep

201994

181994

201994

191994

181994

171994

161994

151994

131994

ID FAN No 1. POS 4 H ALARM - 8.00 mm/S - 0 .500 g/SE

Ratio to Alarm

ALARM

Normalised Multiple Trend Graph


BEARING DAMAGE BEARING DAMAGE BEARING DAMAGE BEARING DAMAGE


The gSE Spectrum TechniqueThe gSE Spectrum Technique

Time domain signal is filtered via a band pass filter with a definable low frequency corner.

The signal is then routed through a peak-to-peak detector to extract only those frequencies which are repetitive

The demodulated signal is then enveloped and transformed into the frequency domain to show the frequency and harmonics of the fault causing the high spike energy


DEMODULATIONDEMODULATION

The high pass filtered signal is routed through a Peak to Peak Detector/demodulator to detect repetetive frequencies.

The signal is then enveloped to detect the modulation rate.

An FFT is then performed on the resulting waveform.


Spike Energy Spectrum TMSpike Energy Spectrum TM

The modulation frequencies of the Spike Energy signal can be displayed as a spectrum

This allows the user to pinpoint the underlying cause of the spike energy.

It allows the user to extract the forcing frequencies ie, bearing or gear impact repetition rates, from a complex spectrum which may mask developing problems


gSE SPECTRUMgSE SPECTRUM

BPFI

2 X BPFI

3 BPFI


gSE SPECTRUMgSE SPECTRUM


ACCELERATION SPECTRUMACCELERATION SPECTRUM


gSE SPECTRUM WITH BANDSgSE SPECTRUM WITH BANDS


WATERFALL DISPLAY WATERFALL DISPLAY gSE gSE SPECTRUMSPECTRUM


FFT OF DEFECT FREQUENCIESFFT OF DEFECT FREQUENCIESFFT OF DEFECT FREQUENCIESFFT OF DEFECT FREQUENCIES


VIBRATION TRANSDUCERSVIBRATION TRANSDUCERSVIBRATION TRANSDUCERSVIBRATION TRANSDUCERS

Overview

and

Selection


THE TRANSDUCERTHE TRANSDUCERTHE TRANSDUCERTHE TRANSDUCER

The “Heart” of Every Vibration Instrument Converts the Mechanical Vibration Energy into an

equivalent Electrical Voltage Signal There are transducers to detect

– Displacement (Eddy-Current or proximity probes)

– Velocity (Velocity Pickup)– Acceleration (Accelerometers)

Accelerometers are the most common because all parameters (displacement, velocity, acceleration, and spike energy) can be obtained


Seismic:- Bearing relative to space. Velocity Pickups Accelerometers Piezoelectric velocity pickups

Relative:- Shaft relative to bearing. Non-contact Eddy Current Displacement Probes

Absolute:- Shaft relative to space. Shaft Contact Displacement Probes (including Shaft Sticks

and Shaft Riders)

TRANSDUCER TYPESTRANSDUCER TYPESTRANSDUCER TYPESTRANSDUCER TYPES


VELOCITY PICKUP CONSTRUCTION VELOCITY PICKUP CONSTRUCTION VELOCITY PICKUP CONSTRUCTION VELOCITY PICKUP CONSTRUCTION

Magnet

Pickup Case Damper

Mass

Springs

Wire Coil SENSITIVITY – 1080 mili volt /inch/sec


PRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATION

The magnet provides a strong magnetic field around the coil.

When held against a vibrating surface the magnet moves whereas the coil remains stationery in space due to the springs.

When the coil of wire cuts magnetic lines of force a voltage is generated in that wire.

This voltage is directly proportional to the magnetic field strength, no of turns on the wire & the velocity at which the lines are cut.

Since the magnetic strength and no of turns are fixed the output is directly proportional to the velocity and hence VELOCITY PICKUPS.


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

ADVANTAGES•Rugged design. •Self- Generating. High electrical output levels.• No On-board Electronics.• Strong signal.•Unaffected by cable length. Can wire upto 300 mtrs.•Can withstand 250 deg C.

DISADVANTAGES•Bulky and heavy in construction.•Limitation on the min and max amplitude and frequencies.•Not reliable below 600 cpm.

VELOCITY PICKUPVELOCITY PICKUPVELOCITY PICKUPVELOCITY PICKUP


Vice grip Pliers 7,200 cpm Hand Held 9” Probe 16,000 cpm Large Magnet 37,000 cpm Hand Held 60,000 cpm Threaded Stud 90,000 cpm

Ensure surfaces are clean and use a smear of silicon grease to improve transmission of vibration.

FREQUENCY LIMITATION - 544FREQUENCY LIMITATION - 544FREQUENCY LIMITATION - 544FREQUENCY LIMITATION - 544


CORRECTION CHARTCORRECTION CHARTCORRECTION CHARTCORRECTION CHART

0 100 200 300 400 500 600 7001

10

100

1000

FREQUENCY - cpm

MU

LT

IPL

ICA

TIO

N F

AC

TO

R

THIS APPLIES TO FILTERED READINGS ONLY


OTHER DRAWBACKSOTHER DRAWBACKSOTHER DRAWBACKSOTHER DRAWBACKS

Velocity transducers work on fixed internal magnetic field.

Interference in this can distort the readings.

Machines such as AC motors, generators etc.. Create interference.

The induced electrical signal is proportional to the strength of the signal at that location in terms of,

– The frequency is proportional to the strength of the external magnetic field.

– The amplitude is proportional to the strength of the external magnetic field.


HOW DO WE CHECK THIS?HOW DO WE CHECK THIS?HOW DO WE CHECK THIS?HOW DO WE CHECK THIS?

F2F1 F3 F5F4

SELECTLIGHT

STOREADV DEC SKIP ADV

STORE

dataPACTM 1250

EntekIRD

HELP +/-

Highlight an icon using the arrow keys, and then press

<SELECT> or <STOP>.

PROGRAM MANAGER

Data Collection Setup Utility Review Data

Balancing Help System

Select Stop

12:53 PM 1.10

ONOFF

SHIFT

RETURN

MANAGER

DONE.

•Connect the pickup to the analyzer

•Hold the pickup just above the motor where readings are normally taken.

•Hold steady and capture data at line frequency.

•The reading observed is the AC interference.


HOW DO WE OVERCOMEHOW DO WE OVERCOMEHOW DO WE OVERCOMEHOW DO WE OVERCOME

Keeping the pickup as far as possible from the magnetic field.

– The problem here is that you may not get the correct vibration.

– You may get probe natural frequency.

– You will definitely miss all you high frequencies.

Using a magnetic shield to reduce the interference.

– It is observed that magnetic shield can reduce interference to a ratio of 100:1.


DIRECT PROD VELOCITY PICKUPDIRECT PROD VELOCITY PICKUPDIRECT PROD VELOCITY PICKUPDIRECT PROD VELOCITY PICKUP The construction is same as velocity pickup.

The coil is moved by a small magnetized prod directly connected to the coil.

It measures actual vibration of the part monitored.

Extremely useful for monitoring machine operating at low frequency. As low as 50rpm.

Valuable for balancing machine applications.

Does not dampen the original vibration, since its light weight.

It is subjected to the similar interference problems.


CONSTRUCTIONCONSTRUCTIONCONSTRUCTIONCONSTRUCTION

MOUNTING BRACKET

Prod

Magnetised tip


Seismic Mass

Piezoelectric Material

Acoustic shield

Preload Stud

Base

Electrical connector

Mounting Stud receptacle

ChargeAmp

ACCELEROMETERACCELEROMETERACCELEROMETERACCELEROMETER

OUT PUT = PICO COULOMBS


PRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATION Acceleration is the measure of the rate of change of velocity.

Generally expressed in “g” which is the same as the acceleration produced by the force of gravity at the surface of the earth.

The value may change due to latitude or elevation but as internationally agreed the value is 980.665 cm/sec2, 386.087 in/sec2 & 32.179 ft/sec2.

Basic material is the piezoelectric material.

This is squeezed between the body and the calibrated weight.

This is the basic force needed to get the desired output.


PRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATIONPRINCIPAL OF OPPERATION Generally works on the quartz crystal principal.

When subjected to mechanical forces, a charge proportional to the force is generated.

Works on the principal,– Force = mass x acceleration

Force and mass being constant the vibration is directly proportional to acceleration.

Acceleration is a function of displacement and frequency squared, hence accelerometers are extremely sensitive to high frequencies.

The charge produced is in picocoulombs which is 1 millionth of 1 millionth of a coulomb. Because of this a high gain amplifier is used.


High Impedance Charge Type.

Generally requires separate charge amplifier.

Low impedance, voltage mode, integrated circuit piezoelectric (ICP) type.

Now included with most data collectors/ Analysers.

AFTER CONDITIONING THE OUTPUT THE VOLTAGE IS READ IN MILI VOLT/G

SIGNAL CONDITIONINGSIGNAL CONDITIONINGSIGNAL CONDITIONINGSIGNAL CONDITIONING


ACCELEROMETERACCELEROMETERACCELEROMETERACCELEROMETER


ADVANTAGES

No moving parts, no wear. Hence rugged. Not affected by outside magnetic fields. Very large dynamic range. amplitude Wide frequency range. Compact, often low weight. High stability. Can be mounted in any orientation & areas where space is the constraint.

DISADVANTAGES

Susceptible to ground loops. Affected by radio frequencies. Cable length effects may reduce sensitivity

ACCELEROMETERSACCELEROMETERSACCELEROMETERSACCELEROMETERS


Main characteristics to consider: Sensitivity (mV/g) Linear frequency range (Hz or CPM) Mass (grams) Dynamic range (Amplitude) Noise Floor Temperature range Ambient conditions Hermetically sealed.

ACCELEROMETERSACCELEROMETERSACCELEROMETERSACCELEROMETERS


Three most common:

Compression Type Inverted Compression Type Shear Type

ACCELEROMETER TYPESACCELEROMETER TYPESACCELEROMETER TYPESACCELEROMETER TYPES


Seismic Mass

Piezoelectric

ICP Amplifier

Acoustic shield

Preload Stud

Base

Electrical connector

Mounting Stud receptacle

COMPRESSION ACCELEROMETERCOMPRESSION ACCELEROMETERCOMPRESSION ACCELEROMETERCOMPRESSION ACCELEROMETER


Advantages Relatively low cost

Disadvantages Sensitive to base strain Sensitive to Thermal transients Can cause over-saturation and transducer settling

problems

Widely used

COMPRESSION TYPECOMPRESSION TYPECOMPRESSION TYPECOMPRESSION TYPE


Piezoelectric MaterialICP Circuit

Mounting stud receptacle

Seismic Mass

Preload Sleeve

INVERTED COMPRESSION INVERTED COMPRESSION INVERTED COMPRESSION INVERTED COMPRESSION


Electric connector

Seismic Mass

Post

Acoustic ShieldPiezoelectric Material

ICP CircuitMounting StudReceptacle

Base

SHEAR TYPESHEAR TYPESHEAR TYPESHEAR TYPE


Lower sensitivity to base strain Large dynamic range Much less sensitive to temperature transients Stabilizes quickly when taking measurements at low

frequencies.

Disadvantage: -

Generally higher cost due to added

components

SHEAR TYPESHEAR TYPESHEAR TYPESHEAR TYPE


Mass

Special ceramic Piezoelectric Disks

Base

Connector

INTEGRATOR

PIEZO ELECTRIC VELOCITY OUTPUT ACCELEROMETERPIEZO ELECTRIC VELOCITY OUTPUT ACCELEROMETERPIEZO ELECTRIC VELOCITY OUTPUT ACCELEROMETERPIEZO ELECTRIC VELOCITY OUTPUT ACCELEROMETER


PIEZO ELECTRIC VELOCITY PICKUPPIEZO ELECTRIC VELOCITY PICKUPPIEZO ELECTRIC VELOCITY PICKUPPIEZO ELECTRIC VELOCITY PICKUP

ADVANTAGES– No moving parts.

– Very useful for low frequency applications. As low as 60 CPM.

– It is not susceptible to magnetic interference.

DISAVANTAGES– High cost.

– Temperature limitations.


WHICH ACCELEROMETER TO USE?WHICH ACCELEROMETER TO USE?WHICH ACCELEROMETER TO USE?WHICH ACCELEROMETER TO USE?


Sensitivity range Frequency range Amplitude range Natural frequency Weight range Usable temperature range Cross axis sensitivity

SELECTION CRITERIASELECTION CRITERIASELECTION CRITERIASELECTION CRITERIA


MountingMaximum

AcceptableFrequency (cpm)

Rating

Stud 975 000 Best

Adhesive 540 000 Very good

Magnet 450 000 Good

Quick Connect 360 000 Quite good

Hand-held 48 000 Poor

MOUNTING CRITERIAMOUNTING CRITERIAMOUNTING CRITERIAMOUNTING CRITERIA


MOUNTED RESONANCEMOUNTED RESONANCEMOUNTED RESONANCEMOUNTED RESONANCE


PROBE TIPSPROBE TIPSPROBE TIPSPROBE TIPS


NATURAL FREQUENCY OF 225MM PROBENATURAL FREQUENCY OF 225MM PROBENATURAL FREQUENCY OF 225MM PROBENATURAL FREQUENCY OF 225MM PROBE


ACCELEROMETERSTYPICALSPECS GENERAL

PURPOSE LOW FREQUENCY

HIGH FREQUENCY

PERMANENT MOUNTED

TRIAXIAL

RANGESENSITIVITY MV/G

FREQUENCYRANGE CPMSTUDMOUNTEDNAT FREQ

WEIGHTRANGE GRAMS

USABLE TEMPRANGE OF

VELOCITYPICKUPS

10-100 500-10,000 0.4-20 10-100 10-100

120-160,000 6-60,000 600-3,600,000 180-600,000 120-600,000

960,000-2,700,000

390,000-2,100,000

4,200,000-10,800,000

1,080,000-1,800,000

480,000-3,000,000

17 -110 135 - 1000 1.2 - 1.5 60 - 180 17 - 130

--100 -250 --100 - 250 --40 - 350 --50 - 250 --100 - 250

EXAMPLETRANSDUCERS

B&K 4390 PCB 8318 WILCOXON 732 IRD 942 VIBRAMET 3130 IRD 544

GENERALPURPOSE

10 - 1000MV/IN/SEC

600-60,000

ABOUT200,000

100 -150

--50 - 250

PAGE 4.3 TABLE 1.


RELATIVERELATIVERELATIVERELATIVE


HOW IT WORKSHOW IT WORKSHOW IT WORKSHOW IT WORKS• It requires an external electronic circuitry to generate a high frequency ac signal.

• This signal applied to the coil generates a magnetic field.

• The shaft close to the tip absorbs some of this magnetic energy.

• This absorption places a load on the electrical signal thereby reducing its strength.

• This loading – reduction of strength is inversely proportional to the distance between the shaft and the tip.

• As the shaft moves relative to the tip the strength changes proportionally.

• The signal sensor provides an ac signal proportional to vibration and dc signal proportional to gap.

•Hence the ac signal is proportion to displacement, hence displacement probe.


EDDY CURRENT PROBEEDDY CURRENT PROBEEDDY CURRENT PROBEEDDY CURRENT PROBE

PICKUPCOIL

MAGNETIC FIELD

SHAFT

GAPMETER

DC SIGNAL SENSOR

DISPLACEMENTSIGNAL - TO ANALYSER ORMONITOR

NON-CONTACT PICKUP

DETECTOROSCILLATOR AMPLIFIER


USED 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.

EDDY CURRENT PROBEEDDY CURRENT PROBEEDDY CURRENT PROBEEDDY CURRENT PROBE


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.

In many instances the gap needs to be set while the shaft is rotating, hence needs competence.

CAREFULCAREFULCAREFULCAREFUL


SIGNAL SENSOR OUTPUT - VOLTS

GAP - MILS (1 MIL = 0.001”)

200mV/mil

0 20 40 60 80 100 120

-2

-6

-10

-14

-18

-22

+0.8 MIL

-0.5 MIL

SET POINT

OUTPUT CURVEOUTPUT CURVEOUTPUT CURVEOUTPUT CURVE


EFFECT ON DIFF SHAFT MATERIAL EFFECT ON DIFF SHAFT MATERIAL EFFECT ON DIFF SHAFT MATERIAL EFFECT ON DIFF SHAFT MATERIAL

0 10 20 30 40 50 60 70 80 90 1000

-2

-4

-6

-8

-10

-12

-14

-16

-18

-20

-22

Gap From Probe Tip to Target (Mils)

Output, V (d.c)

4149 Steel


SHAFT CONTACT DISPLACEMENT PROBES

Shaft Sticks Hardwood, fish-tail, fixed to accelerometer or

velocity pickup Measures vibration amplitude & phase Shaft Riders

ABSOLUTEABSOLUTEABSOLUTEABSOLUTE


Shaft Sticks.

Accelerometer or Velocity pickups fixed to Hardwood, fish-tail.

SHAFT CONTACT MEASUREMENTSHAFT CONTACT MEASUREMENTSHAFT CONTACT MEASUREMENTSHAFT CONTACT MEASUREMENT


PROBE HOLDERPROBE HOLDERPROBE HOLDERPROBE HOLDER

80mm

150m

mB

BB

BB

B

NO

MIN

AL

AA

AA

AA

25m

m

Probe Tip


SHAFT RIDERSHAFT RIDERSHAFT RIDERSHAFT RIDER

SHAFT SURFACE

NON-METALLIC TIP

MACHINE HOUSING

SHAFT RIDER ASSEMBLY

PICKUP MOUNTING STUD


MOUNTING FLANGE ACCELEROMETERMOUNTING FLANGE ACCELEROMETERMOUNTING FLANGE ACCELEROMETERMOUNTING FLANGE ACCELEROMETER

3 HOLE

FIXING

DUAL ELEMENT

PIEZO-ELECTRIC DEVICE

HEAVY DUTY BLUE OUTER JACKET

HIGH TEMPERATURE CROSS LINKED POLYMER CABLE

ELECTRONICS IN BASE FOR DRIVING

LONG CABLES

FLEXIBLE STAINLESS STEEL ARMOUR


REAL LIFE PICTURESREAL LIFE PICTURESREAL LIFE PICTURESREAL LIFE PICTURES

Case Absolute - Seismic Velocity or Accelerometer

6622 Dual Channel Case Absolute Vibration

– Two Channel

– Accepts Velocity or Acceleration Input

Application– Measures radial vibration primarily on

Roller Bearing applications

CASE ABSOLUTECASE ABSOLUTECASE ABSOLUTECASE ABSOLUTE

Shaft Relative - dual X-Y non-contact pickups

6652 Dual Channel Relative Shaft Vibration

– Two Channel

– Accepts NCPU Input

Application– Monitors radial vibration primarily on

sleeve bearing application

SHAFT RELATIVESHAFT RELATIVESHAFT RELATIVESHAFT RELATIVE

Shaft Absolute - either Shaft Rider or Accel/NCPU combination

6621 Shaft Absolute Vibration– Accepts either Seismic Velocity or

Acceleration and NCPU transducers

6622 Case Absolute Vibration– Shaft Rider configuration

Application– High shaft/case weight ratio

SHAFT ABSOLUTESHAFT ABSOLUTESHAFT ABSOLUTESHAFT ABSOLUTE

Eccentricity - utilizes a non-contact pickup located in the front standard area

6686 Dual Channel Eccentricity– Accepts two NCPU inputs

Application– measure shaft bow from < 1 RPM to ~ 180

RPM

– monitors shaft bow while turning gear is engaged

– indicates when machine is ready to increase speed

ECCENTRICITYECCENTRICITYECCENTRICITYECCENTRICITY

Machine Speed - utilizes non-contact pickup or magnetic interrupter

6675 Speed/Acceleration– Accepts either NCPU or Magnetic Interrupter

– If primary signal fails, automatically switches to backup

Application– Locked Rotor alarm indicates startup sequence

fault

– Zero Speed detection s need to engage turning gearD

LFOR .300 TIP D=1.0"

L=.3"

SPEED ACCELERATIONSPEED ACCELERATIONSPEED ACCELERATIONSPEED ACCELERATION

Position/Thrust - dual non-contact pickup using AND voting recommended

6682 Dual Channel Position– Accepts two NCPU transducers

Application– Early detection of thrust bearing wear,

balance piston wear, and loose thrust bearing

– Indicator of misalignment and compressor surge

POSITION / THRUSTPOSITION / THRUSTPOSITION / THRUSTPOSITION / THRUST

Shell Expansion - utilizes a Linear Variable Differential Transducer (LVDT) Input

6687 Dual Channel Shell Expansion– Accepts LVDT input

Application– Ensures uniform shell expansion

– Avoids machine damage due to non-uniform thermal and mechanical expansion

SHELL EXPANSIONSHELL EXPANSIONSHELL EXPANSIONSHELL EXPANSION

Differential Expansion - utilizes long range non-contact pickups

6688 Dual Channel Differential Expansion

– Accepts two long range NCPU transducers

Application– Critical to monitor effect of thermal

expansion and avoid turbine rubs

– Monitor supports multiple configurations

DIFFERENTIAL EXPANSIONDIFFERENTIAL EXPANSIONDIFFERENTIAL EXPANSIONDIFFERENTIAL EXPANSION

Valve Position - utilizes a rotary cam potentiometer or LVDT

6689 Dual Channel Valve Position– Accepts Rotary Cam or LVDT input

Application– Monitor inlet valve position on a steam

turbine


SUMMARYSUMMARYSUMMARYSUMMARY

THERE IS NO SUCH THING AS PERFECT TRANSDUCER FOR ALL APPLICATIONS.

YOUR DECISION ON SELECTING A PARTICULAR TRANSDUCER IS CRITICAL IN OBTAINING ACCURATE AND RELIABLE DATA.

WHICH PARAMETERS NEED TO BE MEASURED. OPERATING TEMPERATURES. APPLICATION. SAFETY. WHICH FREQUENCIES ARE TO BE CARTURED.


TEA BREAK


INSTRUMENTS FOR VIBRATION INSTRUMENTS FOR VIBRATION DETECTIONDETECTION

INSTRUMENTS FOR VIBRATION INSTRUMENTS FOR VIBRATION DETECTIONDETECTION


The assessment on a continuous or periodic The assessment on a continuous or periodic basis of the mechanical condition of basis of the mechanical condition of machinery, equipment and systems from the machinery, equipment and systems from the observations and/or recording of observations and/or recording of selected selected measurement parameters.measurement parameters.

CONDITION MONITORINGCONDITION MONITORINGCONDITION MONITORINGCONDITION MONITORING


What 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?

CHOOSING YOUR INSTRUMENTATIONCHOOSING YOUR INSTRUMENTATIONCHOOSING YOUR INSTRUMENTATIONCHOOSING YOUR INSTRUMENTATION


Hand held amplitude meter. (spot checker)

Quick Check Analysers

FFT Data Collector/Analysers

Full Feature Analysers

Real Time Spectrum Analysers

Instrument Quality Tape Recorders

Dedicated Balancing instruments

Continious vibration monitoring systems.

INSTRUMENT TYPESINSTRUMENT TYPESINSTRUMENT TYPESINSTRUMENT TYPES


Measures total vibration only.

Simple easy to you, no storage of data

Lightweight/ portable

No frequency information

Limited capability Main application is on non-critical machinery

OVERALL AMPLITUDE METERSOVERALL AMPLITUDE METERSOVERALL AMPLITUDE METERSOVERALL AMPLITUDE METERS


THE SPOT CHECKERTHE SPOT CHECKERTHE SPOT CHECKERTHE SPOT CHECKER


12

3

4

5

1

2

3

45

DateFrequency

Vibration

Overall Level

Spectrum

FANFAN

INTERPRETATION OF READINGINTERPRETATION OF READINGINTERPRETATION OF READINGINTERPRETATION OF READING


Vibration

DateFrequency

12 3 4 5

Overall Level

12

34

5

GEARBOXGEARBOX

INTERPRETATION OF READINGINTERPRETATION OF READINGINTERPRETATION OF READINGINTERPRETATION OF READING


Will obtain rapid hard copy printouts of the amplitude / time and frequency characteristics of a vibration.

Used for basic trending & analysis purposes.

Low cost.

Easy to operate.

Excellent for quick “on site” assessments of machinery condition.

QUICK CHECK ANALYZERSQUICK CHECK ANALYZERSQUICK CHECK ANALYZERSQUICK CHECK ANALYZERS


SWEPT FILTER ANALYZERSSWEPT FILTER ANALYZERSSWEPT FILTER ANALYZERSSWEPT FILTER ANALYZERS Older technology It is like tuning a radio through the

frequency range. Amplitude at each frequency is

displayed. Not very portable Provides frequency information but

very slow Usually has a strobe light No storage of data Acceptable for analysing one machine

at a time, not suitable for a large predictive maintenance program.


SWEPT FILTER ANALYZER BANDWIDTHSWEPT FILTER ANALYZER BANDWIDTHSWEPT FILTER ANALYZER BANDWIDTHSWEPT FILTER ANALYZER BANDWIDTH

“Bandwidth” rejects all frequencies not within upper and lower “cutoff” frequencies

Bandwidth can be set to 3%, 5%, 10%, etc..

– 10% - Broad - less accurate - less time

– 3% - Sharp - more accurate - more time

Constant Bandwidth: fixed frequency range

Constant Percentage: percentage of tuned centre frequency


TUNING INTO VIBRATION FREQUENCIESTUNING INTO VIBRATION FREQUENCIESTUNING INTO VIBRATION FREQUENCIESTUNING INTO VIBRATION FREQUENCIES


Slow Sweep

Fast Sweep

ERROR DUE TO SWEEPINGERROR DUE TO SWEEPINGERROR DUE TO SWEEPINGERROR DUE TO SWEEPING


WHAT IS FFT?WHAT IS FFT?WHAT IS FFT?WHAT IS FFT?

Also known as a Spectrum or as the Frequency domain

Graph of Vibration Amplitude vs. Frequency

All frequencies in a chosen range are separated and displayed as individual peaks each having its own amplitude

Most useful tool for analysis


WHAT IS A SPECTRUMWHAT IS A SPECTRUMWHAT IS A SPECTRUMWHAT IS A SPECTRUM


Lighweight Current state-of-the-art Portable High accuracy of measurement Very high maximum frequency. Rapid frequency information Data storage capability Often has advanced analysis functions Dynamic Range up to 96 dB Much faster than analog 2 Channels Balancing in 1& 2 planes

Primary function is the rapid acquisition of “route data” for Primary function is the rapid acquisition of “route data” for storage in a computer software system but will usually have a storage in a computer software system but will usually have a secondary “off tour” analysis capability secondary “off tour” analysis capability

FFT DATA COLLECTORSFFT DATA COLLECTORSFFT DATA COLLECTORSFFT DATA COLLECTORS


Primary function is the in depth analysis of complex machinery defects either “on site” or from stored data,

May inteface with PMP software & have secondary function as a Data collector.

Can be Swept filter or FFT, or both.

Advanced data acquisition and display functions.

May have “Real Time” data acquisition rate but not “Real Time” screen update.

FULL FEATURE ANALYZERSFULL FEATURE ANALYZERSFULL FEATURE ANALYZERSFULL FEATURE ANALYZERS


Very expensive

Fairly portable

Multi-channel capability

(STA), Order tracking, Natural frequency tests.

Real-time display.

Requires frequent/ training to maintain proficiency

Powerful for advanced diagnostics

REAL TIME SPECTRUM ANALYZERREAL TIME SPECTRUM ANALYZERREAL TIME SPECTRUM ANALYZERREAL TIME SPECTRUM ANALYZER


The Highest rate at which data can

be captured and displayed without

leaving any gaps in the analysis.

REAL TIME RATEREAL TIME RATEREAL TIME RATEREAL TIME RATE


Time Record 1

Time Record 2

Time Record 3

FFT 1 FFT 2

REAL TIME OPERATIONREAL TIME OPERATIONREAL TIME OPERATIONREAL TIME OPERATION


Time 1 Time 2 Time 3

FFT 1 FFT 2

NON-REAL TIME OPERATION NON-REAL TIME OPERATION NON-REAL TIME OPERATION NON-REAL TIME OPERATION


Multi-Channel simultaneous recording. Captures transient events for replay in dynamic form. Analogue (dynamic range 40 to 48 dB) Digital (dynamic range about 78dB) Expensive. Requires a vibration analyser to process the signal.

Analysis at your leisure

INSTRUMENT QUALITY TAPE RECORDERSINSTRUMENT QUALITY TAPE RECORDERSINSTRUMENT QUALITY TAPE RECORDERSINSTRUMENT QUALITY TAPE RECORDERS


Designed to achieve a rapid and automated balance of rotating bodies in one, two, or three planes from two simultaneous inputs.

DEDICATED BALANCING INSTRUMENTSDEDICATED BALANCING INSTRUMENTSDEDICATED BALANCING INSTRUMENTSDEDICATED BALANCING INSTRUMENTS


Portability Relative cost Ease of use Frequency & Dynamic range Measurement parameters Operation & Display types Transducer types Reference and/or Strobe light Software available

CRITERIA FOR COMPARISONCRITERIA FOR COMPARISONCRITERIA FOR COMPARISONCRITERIA FOR COMPARISON


Spike Energy, HFD, or Shock Pulse . Enveloping. Selectable frequency range? Synchronous Time Averaging. Waterfall, Bode plotting. Display Update rate. Data storage. What method? How much? Of what?, Spectra, Time

Waveform, etc... PM P software available. Multi - channel.

CRITERIA FOR COMPARISONCRITERIA FOR COMPARISONCRITERIA FOR COMPARISONCRITERIA FOR COMPARISON


SCAN RATE V/S TIMESCAN RATE V/S TIMESCAN RATE V/S TIMESCAN RATE V/S TIME

““ Cri

tica

l”C

riti

cal”

““ Ess

enti

al”

Ess

enti

al”

““ BO

PB

OP

””

Co

st

of

Lo

st P

rod

uct

ion

Co

st

of

Lo

st P

rod

uct

ion

Gradual DegradationGradual Degradation Sudden Onset FailureSudden Onset Failure

Time to Failure / Required Scan RateTime to Failure / Required Scan Rate

ContinuousContinuousMonitoring andMonitoring and

ProtectionProtectionSystemsSystems

On-lineOn-lineSurveillanceSurveillance

SystemsSystems

Walk-AroundWalk-AroundData CollectorsData Collectorsand Analyzersand Analyzers

MonthsMonths WeeksWeeks DaysDays HoursHours MinutesMinutes SecondsSecondsYearsYears

$$$$$$

$$$$

$$

Co

st

pe

r P

oin

tC

os

t p

er

Po

int


ONLINE SYSTEMSONLINE SYSTEMSONLINE SYSTEMSONLINE SYSTEMS


DAY 2DAY 2DAY 2DAY 2

UNDERSTANDING FFT


FROM TIME TO FREQUENCYFROM TIME TO FREQUENCYFROM TIME TO FREQUENCYFROM TIME TO FREQUENCY

Time Domain(Sec or Min)

Frequency Domain(CPM or Hertz)

Complex Waveform

FrequencySpectrumPlot

TMAX

FMAX

1X1X3X3X

5X5X

9X9X


PROCESS OF GENERATING AN FFTPROCESS OF GENERATING AN FFTPROCESS OF GENERATING AN FFTPROCESS OF GENERATING AN FFT

Integration and Calibration based on sensitivity take place at input

Anti-Alias Filter removes frequencies above the given maximum frequency for collection


ANTI ALIAS FILTER(NYQUIST THEOROM)ANTI ALIAS FILTER(NYQUIST THEOROM)ANTI ALIAS FILTER(NYQUIST THEOROM)ANTI ALIAS FILTER(NYQUIST THEOROM)

“If we are not to lose any information contained in the sampled signal, we must sample at a frequency rate of at least twice the highest frequency component of interest.”


ANTI ALIAS FILTERANTI ALIAS FILTERANTI ALIAS FILTERANTI ALIAS FILTER


PROCESS OF GENERATING AN FFTPROCESS OF GENERATING AN FFTPROCESS OF GENERATING AN FFTPROCESS OF GENERATING AN FFT

The A/D Converter digitises the data The Windowing process compromises between

frequency and amplitude accuracy The Input Buffer temporarily stores data FFT calculation Averaging removes any “transient” events


SAMPLINGSAMPLINGSAMPLINGSAMPLING


WINDOWING FUNCTIONWINDOWING FUNCTIONWINDOWING FUNCTIONWINDOWING FUNCTION


TYPES OF WINDOWSTYPES OF WINDOWSTYPES OF WINDOWSTYPES OF WINDOWS

HANNING

HAMMING

FLAT TOP

RECTANGULAR

KAISER BESSEL


DIFFERENCE BETWEEN FLAT TOP AND HANNINGDIFFERENCE BETWEEN FLAT TOP AND HANNINGDIFFERENCE BETWEEN FLAT TOP AND HANNINGDIFFERENCE BETWEEN FLAT TOP AND HANNING


LINES OF RESOLUTIONLINES OF RESOLUTIONLINES OF RESOLUTIONLINES OF RESOLUTION


RELATIONSHIP BETWEEN LINES, FMAX & RESOLUTIONRELATIONSHIP BETWEEN LINES, FMAX & RESOLUTIONRELATIONSHIP BETWEEN LINES, FMAX & RESOLUTIONRELATIONSHIP BETWEEN LINES, FMAX & RESOLUTION

Increasing FMax gives worse Resolution Decreasing FMax gives better Resolution Increasing the Lines gives better Resolution Decreasing Lines gives worse Resolution The better the Frequency Resolution, the longer it

takes to obtain the FFT reading and the more memory it requires to store

Increasing FMax gives worse Resolution Decreasing FMax gives better Resolution Increasing the Lines gives better Resolution Decreasing Lines gives worse Resolution The better the Frequency Resolution, the longer it

takes to obtain the FFT reading and the more memory it requires to store


SPECTRA PARAMETERSSPECTRA PARAMETERSSPECTRA PARAMETERSSPECTRA PARAMETERS

Amplitude Units - Displacement, Velocity, Acceleration, and Spike Energy

Frequency Units - CPM or Hz Frequency Max (Fmax) - The range of

frequency Lines of Resolution - The accuracy or

sharpness of the displayed frequencies Number of Spectral Averages - Spectra are

averaged to minimise transient events


SELECTING PROPER FMAXSELECTING PROPER FMAXSELECTING PROPER FMAXSELECTING PROPER FMAX

Most important FFT Decision

Must be high enough to include all significant, problem-related frequencies. We can not afford to miss anything!

The higher we go, the more we decrease our accuracy between frequency peaks


EFFECT OF IMPROPER FMAXEFFECT OF IMPROPER FMAXEFFECT OF IMPROPER FMAXEFFECT OF IMPROPER FMAX


WHERE TO STARTWHERE TO STARTWHERE TO STARTWHERE TO START

Collect data with a fairly high Fmax and if no high frequencies are present, then lower

Use General Machinery Charts

Anticipate the highest problem-related frequency for a given machine



Rolling-element bearings

–About 120,000 CPM (2KHz)

Sleeve bearing machines

–Usually not to exceed 60,000CPM (1KHz)

Gear Drives

–Fundamental gear mesh frequency x 3.25


FMAX EXAMPLEFMAX EXAMPLEFMAX EXAMPLEFMAX EXAMPLE

GMF1 = (50T)(1180 RPM) = (20T)(2950 RPM)

GMF1 = 59,000 CPM

POS 3HI FMAX = GMF1 X 3.25

= 191,750 CPM

USE POS 3HI FMAX = 200,000 CPM

GMF2 = 54T X 2950 RPM = (30T)(5310 RPM)

GMF2 = 159,300 CPM

POS 6HI FMAX = 3.25 X 159,300

= 517,725 CPM

USE POS 6HI FMAX = 540,000 CPM

(Must Measure Acceleration Here)


FFT LINES OF RESOLUTIONFFT LINES OF RESOLUTIONFFT LINES OF RESOLUTIONFFT LINES OF RESOLUTION

Determines Frequency Accuracy by setting the “Sharpness” used in obtaining the FFT

Frequency range (0 to Fmax) is divided equally by the number of these “bins”

Typical FFT Analysers offer choices of

–25, 50, 100, 200, 400, 800,

1600, 3200, 6400, and 12,800 lines


FREQUENCY RESOLUTIONFREQUENCY RESOLUTIONFREQUENCY RESOLUTIONFREQUENCY RESOLUTION

For an Fmax of 120,000 CPM with 400 Lines, the Resolution = 300 CPM / bin

Every vibration frequency present within a given 300 CPM span will be averaged together and shown as one peak

Thus it is possible that more than one peak exists in a 300 CPM span


RELATIONSHIP BETWEEN FMAX,LINES & RELATIONSHIP BETWEEN FMAX,LINES & RELATIONSHIPRELATIONSHIP

RELATIONSHIP BETWEEN FMAX,LINES & RELATIONSHIP BETWEEN FMAX,LINES & RELATIONSHIPRELATIONSHIP

Increasing Fmax gives worse Resolution Decreasing Fmax gives better Resolution Increasing the Lines gives better Resolution Decreasing Lines gives worse Resolution The better the Frequency Resolution, the

longer it takes to obtain the FFT reading and the more memory it requires to store


UNDERSTAND CURSOR FREQUENCYUNDERSTAND CURSOR FREQUENCYUNDERSTAND CURSOR FREQUENCYUNDERSTAND CURSOR FREQUENCY

The lines of resolution determine the speed and accuracy of data collection

The FFT displays the ”Cursor Frequency”

The actual peak lies somewhere within the band defined by the frequency resolution


SPECTRAL AVERAGINGSPECTRAL AVERAGINGSPECTRAL AVERAGINGSPECTRAL AVERAGING

Linear or RMS Exponential Time Synchronous Peak Hold


SPECTRAL AVERAGINGSPECTRAL AVERAGINGSPECTRAL AVERAGINGSPECTRAL AVERAGING

More than one set of data is taken for a given FFT reading

These sets of data are averaged together to help eliminate the influence of transient or random vibrations in the FFT that can confuse the data readings

The number of data sets is usually 2, 4, or 8–Can go much higher as need arises


HOW MANY SPECTRAL AVERAGESHOW MANY SPECTRAL AVERAGESHOW MANY SPECTRAL AVERAGESHOW MANY SPECTRAL AVERAGES

Compromise between accuracy and time For general machines, use 4 averages When collecting data on High Frequency

machines or performing a detailed analysis, use at least 8 averages

Set higher where random vibration occurs If overlapping is option, then use 8 averages

with 50% overlap


INCREASING AVERAGES LIMITS INCREASING AVERAGES LIMITS TRANSIENTSTRANSIENTS

INCREASING AVERAGES LIMITS INCREASING AVERAGES LIMITS TRANSIENTSTRANSIENTS


PM PROGRAMEPM PROGRAMEPM PROGRAMEPM PROGRAME

Implementing an Implementing an effective predictive effective predictive

maintenance programmaintenance program


AIM OF PM PROGRAMAIM OF PM PROGRAMAIM OF PM PROGRAMAIM OF PM PROGRAM

Effectiveness - doing the right things

Efficiency - doing things right

Continuous Improvement - doing the right things better tomorrow


PRE IMPLEMENTATION ISSUESPRE IMPLEMENTATION ISSUESPRE IMPLEMENTATION ISSUESPRE IMPLEMENTATION ISSUES

What are your objectives ? Is the technology applicable to your plant ? What are the organizational implications ? Material requirements ? How much does it cost ? Is it justified ? Do we have management commitment ?


TYPICAL PM OBJECTIVESTYPICAL PM OBJECTIVESTYPICAL PM OBJECTIVESTYPICAL PM OBJECTIVES

PROCESS / UTILITIES INDUSTRY

Extension of Planned Maintenance intervals Reduction of Planned Maintenance content Protection of vital, key equipment Focussing of activity resources Product quality improvement Lower spare parts inventory



BATCH MANUFACTURING INDUSTRY

Protection of vital, key equipment Non interruption of production runs Optimized maintenance effort during shut downs Focussing of activity resources Product quality improvement Lower spare parts inventory



BATCH INDUSTRY

Decrease downtime with no associated cost penalty.

PROCESS / UTILITY

Decrease costs with no associated downtime penalty.


PROGRAM PLANNINGPROGRAM PLANNINGPROGRAM PLANNINGPROGRAM PLANNING

Set objectives Structured criticality assessment Preliminary cost benefit analysis Get management commitment Define budgets Start pilot program Establish schedule


TYPICAL IMPLEMENTATION PLANTYPICAL IMPLEMENTATION PLANTYPICAL IMPLEMENTATION PLANTYPICAL IMPLEMENTATION PLAN

1 - Initial system setup

2 - Learn to swim

3 - Applicable training

4 - Second stage setup

5 - Ongoing support


PHASE 1 – INITIAL SYSTEM SETUPPHASE 1 – INITIAL SYSTEM SETUPPHASE 1 – INITIAL SYSTEM SETUPPHASE 1 – INITIAL SYSTEM SETUP

System installation Database setup Initial training Baseline data collection Route compilation Overall exception level setting


PHASE 2 – LEARN TO SWIMPHASE 2 – LEARN TO SWIMPHASE 2 – LEARN TO SWIMPHASE 2 – LEARN TO SWIM

Routine data collection

System familiarisation

Problem identification


PHASE 3 - TRAININGPHASE 3 - TRAININGPHASE 3 - TRAININGPHASE 3 - TRAINING

On or off site General awareness Basic system operation Vibration analysis - VA1,2,3 Advanced system management Syndicate work Interactive training


PHASE 4 – SECOND STAGE SETUPPHASE 4 – SECOND STAGE SETUPPHASE 4 – SECOND STAGE SETUPPHASE 4 – SECOND STAGE SETUP

Database expansion

Advanced features

Frequency analysis groups

Spectral alarms


PHASE 5 – ONGOING SUPPORTPHASE 5 – ONGOING SUPPORTPHASE 5 – ONGOING SUPPORTPHASE 5 – ONGOING SUPPORT

Partner mind set - Platinum club etc. System upgrades Data analysis assistance System management contracts Hardware calibrations Post implementation reviews



Plant SurveyPlant Survey




Select machines

Select machines




Select machines

Select machines

Select Technique

Select Technique




Select machines

Select machines

Select Technique

Select Technique

Set-up SystemSet-up System


DATABASE

ROUTE

OPTIONS

CHANGE PLANTPLANTTRAINMACHINEPOINTFREQUENCY BANDSROUTE INSTRUCTIONSNOTE CODES

CHANGE PLANTADDEDITRECALLSTOREDELETEPRINTCLEARDATA DIRECTORYSYSTEM DEFAULTSCOLORSHARDWAREDATA COLLECTORHOUSEKEEPERDOS FUNCTION

SETUP



Creating first on paper saves time

Do not create too many measurement points - could be a waste of time, money, and computer storage.

PLANNING DATABASE & ROUTE DATAPLANNING DATABASE & ROUTE DATAPLANNING DATABASE & ROUTE DATAPLANNING DATABASE & ROUTE DATA


Classify equipment into groups and determine which groups to monitor - consider

(a) Equipment Classification

- Critical

- Essential

- General purpose

PLANNING YOUR DATABASE FILESPLANNING YOUR DATABASE FILESPLANNING YOUR DATABASE FILESPLANNING YOUR DATABASE FILES


(b) Failure Rate - Monitor equipment that has a high failure rate

(c) Safety - Regularly monitor any equipment whose failure results in unsafe conditions or threatens personnel safety

(d) Cost of Downtime - Monitor any equipment that results in large monetary losses due to downtime



Determine where to take the measurements for best indicating the condition of the equipment.

Estimate the number of locations - Too many points reduces software performance.

Identify the parameters for determining the condition of the equipment.

Fill in a database configuration worksheet



Plan on paper Review layout of your plant to determine equipment

Select which points to use in the route. Can have as many routes as you like.

Walk through plant following route - decide on most convenient sequence for collecting measurements in the fastest possible time

PLANNING YOUR ROUTESPLANNING YOUR ROUTESPLANNING YOUR ROUTESPLANNING YOUR ROUTES


Make some measurements to estimate time to collect data for all points on the route

Clearly identify the measurement locations to ensure same location and direction

Identify how often to monitor the equipment.

Fill in a route planning worksheet

PLANNING YOUR ROUTESPLANNING YOUR ROUTESPLANNING YOUR ROUTESPLANNING YOUR ROUTES



Set/review Limits

Set/review Limits


Select machines

Select machines

Select Technique

Select Technique

Set-up SystemSet-up SystemMeasureMachine

MeasureMachine



Set/review Limits

Set/review Limits


Select machines

Select machines

Select Technique

Select Technique


MeasureMachine

ConditionAnalysis

ConditionAnalysis

Not OK



Set/review Limits

Set/review Limits


Select machines

Select machines

Select Technique

Select Technique


MeasureMachine

ConditionAnalysis

ConditionAnalysis

Not OK

Fault Correction

Fault Correction

Fault Found



Set/review Limits

Set/review Limits


Select machinesSelect machines

Select Technique

Select Technique


MeasureMachine

ConditionAnalysis

ConditionAnalysis

Not OK

Fault Correction

Fault Correction

Fault Found

No Fault Found


ANALYZE FAILUREANALYZE FAILUREANALYZE FAILUREANALYZE FAILURE

Ask the questions:

–Understand what went wrong physically

–What needed to exist for this to happen

»Conditions

»Events Follow the “fault tree” to a “root cause”


ANALYZE FAILURE TILL THE ROOTANALYZE FAILURE TILL THE ROOTANALYZE FAILURE TILL THE ROOTANALYZE FAILURE TILL THE ROOT

Identify unacceptable performanceBe specific, use measures

Ask both:"why is this happening", and "what conditions must exist for this to happen"

Keep asking until there are no more answersThis is your root cause


ANALYZE YOUR DECISIONSANALYZE YOUR DECISIONSANALYZE YOUR DECISIONSANALYZE YOUR DECISIONS

We tend to stick with what we knowWe jump to solutions that appear obviousWe seldom test those solutions for completeness

We really need to be more innovative and creative in our problem solving

Failure analysis is driven by our knowledge of causes of failure

Events need to be consideredEvents trigger conditions that cause failures



Set/review Limits

Set/review Limits


Select machinesSelect machines

Select Technique

Select Technique


MeasureMachine

ConditionAnalysis

ConditionAnalysis

Not OK

Fault Correction

Fault Correction

Fault Found

No Fault Found

RoutineMonitoring

RoutineMonitoring

DataRecording

DataRecording

TrendAnalysis

TrendAnalysis

OK

OK

Alarm


PHASE ? SYSTEM REVIEWPHASE ? SYSTEM REVIEWPHASE ? SYSTEM REVIEWPHASE ? SYSTEM REVIEW

Communicate success Adapt for failure Adjust alarms Add measurements Extend to new machines Identify problem machines Embrace new technologies


PHASE ? SYSTEM REVIEWPHASE ? SYSTEM REVIEWPHASE ? SYSTEM REVIEWPHASE ? SYSTEM REVIEW

Is your CM programme changing the way you do maintenance ?

Data or information ?

Is your CM programme saving or just costing you money ?

Are you running CM for it’s own sake ?

Is anyone aware of the above ?


Denial

NO!

Anger

Bargaining

Depression

Acceptance!

Do it slowly

Let people understand why

Help them to be involved

Listen to and act on their concerns

Communicate

MANAGING CHANGEMANAGING CHANGEMANAGING CHANGEMANAGING CHANGE


Overall Alarm Reports

Band Alarm Reports

Inspection Code Reports

Spectral Reports

GENERATING MEANINGFUL REPORTSGENERATING MEANINGFUL REPORTSGENERATING MEANINGFUL REPORTSGENERATING MEANINGFUL REPORTS


Reports all machines that have vibration which has exceeded the Overall Alarm for one or more points

OVERALL TRENDOVERALL TRENDOVERALL TRENDOVERALL TREND


WATERFALLWATERFALLWATERFALLWATERFALL


SPECTRUMSPECTRUMSPECTRUMSPECTRUM


POLAR PLOTSPOLAR PLOTSPOLAR PLOTSPOLAR PLOTS


EXCEPTION REPORTEXCEPTION REPORTEXCEPTION REPORTEXCEPTION REPORT


OVERALL REPORTOVERALL REPORTOVERALL REPORTOVERALL REPORTPage No. 19/16/2003 8:42 PMCOLLECTED MEASUREMENT REPORTLocation Pos Direction Data Type Units Filter Value Date/TimeArea 2 Level 3PA FAN #1MTR-OB-HORIZ 1 Horizontal Magnitude ips Overall .43 6/4/1997 11:12 AM MTR-OB-HORIZ 1 Horizontal Spectrum ips None .553 6/4/1997 11:13 AM MTR-OB-HORIZ 1 Horizontal Magnitude g's High Frequency .037 6/4/1997 11:12 AM

MTR-OB-HORIZ 1 Horizontal Spectrum g's Envelope .00858 6/4/1997 11:13 AM MTR-OB-VERT 1 Vertical Magnitude ips None .503 6/4/1997 11:13 AM MTR-OB-VERT 1 Vertical Spectrum ips None .48 6/4/1997 11:14 AM MTR-IB-HORIZ 2 Horizontal Magnitude ips None .481 6/4/1997 11:15 AM MTR-IB-HORIZ 2 Horizontal Spectrum ips None .464 6/4/1997 11:15 AM MTR-IB-HORIZ 2 Horizontal Magnitude g's High Frequency .128 6/4/1997 11:15 AM

MTR-IB-HORIZ 2 Horizontal Spectrum g's Envelope .0335 6/4/1997 11:14 AM MTR-IB-VERT 2 Vertical Magnitude ips None .247 6/4/1997 11:15 AM MTR-IB-VERT 2 Vertical Spectrum ips None .245 6/4/1997 11:15 AM MTR-IB-AXIAL 2 Axial Magnitude ips None .114 6/4/1997 11:16 AM MTR-IB-AXIAL 2 Axial Spectrum ips None .0921 6/4/1997 11:16 AM FAN-IB-HORIZ 3 Horizontal Magnitude ips None .86 6/4/1997 11:17 AM FAN-IB-HORIZ 3 Horizontal Spectrum ips None .851 6/4/1997 11:17 AM FAN-IB-HORIZ 3 Horizontal Magnitude g's High Frequency .065 6/4/1997 11:17 AM

FAN-IB-HORIZ 3 Horizontal Spectrum g's Envelope .0235 6/4/1997 11:16 AM FAN-OB-HORIZ 4 Horizontal Magnitude ips None .87 6/4/1997 11:17 AM FAN-OB-HORIZ 4 Horizontal Spectrum ips None .774 6/4/1997 11:18 AM FAN-OB-HORIZ 4 Horizontal Magnitude g's High Frequency .178 6/4/1997 11:17 AM

FAN-OB-HORIZ 4 Horizontal Spectrum g's Envelope .118 6/4/1997 11:18 AM


General Considerations

and Pitfalls.


Measurement Locations. Machine and Point Identification. Measurement Parameters. Instrument and Transducer Selection. Measurement Techniques. The use of Probes and Transducer Mounting

CONSIDERATIONS IN OBTAINING QUALITY CONSIDERATIONS IN OBTAINING QUALITY DATADATA

CONSIDERATIONS IN OBTAINING QUALITY CONSIDERATIONS IN OBTAINING QUALITY DATADATA


MEASUREMENT LOCATIONSMEASUREMENT LOCATIONSMEASUREMENT LOCATIONSMEASUREMENT LOCATIONS


MEASUREMENT DIRECTIONSMEASUREMENT DIRECTIONSMEASUREMENT DIRECTIONSMEASUREMENT DIRECTIONS


Select optimum locations. For acceleration and ultra-sonic rolling element

bearing detection get as close to the machine bearings as possible (ideally within load zone).

If you have to compromise on safety or frequency response consider installing a permanently mounted transducer

CHOOSE MEASUREMENT LOCATIONSCHOOSE MEASUREMENT LOCATIONSCHOOSE MEASUREMENT LOCATIONSCHOOSE MEASUREMENT LOCATIONS


Never compromise safety. Measure as near as possible to the vertical,

horizontal and axial centrelines Any axial measurement is better than none so long

as the same location is used each time Do not mistake seal locations for bearing locations

e.g. on pumps Avoid measurements on locations with a low

dynamic resistance e.g. protective covers

CHOOSE MEASUREMENT LOCATIONSCHOOSE MEASUREMENT LOCATIONSCHOOSE MEASUREMENT LOCATIONSCHOOSE MEASUREMENT LOCATIONS


Always Use Consistent numbering and naming conventions ie:-

a) Number the measurement points in the line of drive from the outboard end of the prime mover to the outboard bearing of the driven machine.

b) Consistent lettering conventions for the direction of the pickup

e.g. A - Axial H - Horizontal V - Vertical

MACHINE POINT IDENTIFICATIONMACHINE POINT IDENTIFICATIONMACHINE POINT IDENTIFICATIONMACHINE POINT IDENTIFICATION


Motor Inboard Bearing (Drive end) 2 MIV

Option 1Location on the Machinery Option 2

1Motor Outboard Bearing (Non drive end) MOV

3Fan (Driven) Inboard Bearing FIV

4Fan (Driven) Outboard Bearing FOV

Number from the DE of prime mover to the NDE of driven unit.

USE CONSISTENT NAMING CONVENTIONUSE CONSISTENT NAMING CONVENTIONUSE CONSISTENT NAMING CONVENTIONUSE CONSISTENT NAMING CONVENTION


Clearly mark machine with the same name as on computer database and data collector

Produce machine drawings showing measurement locations

Clearly mark and label measurement point locations

- Use Special paint, metal stamps etc.

MACHINE AND POINT IDENTIFICATIONMACHINE AND POINT IDENTIFICATIONMACHINE AND POINT IDENTIFICATIONMACHINE AND POINT IDENTIFICATION


MACHINE DRAWING AND DATAMACHINE DRAWING AND DATAMACHINE DRAWING AND DATAMACHINE DRAWING AND DATA

DRIVER INTERMEDIATE DRIVENRPM min: 3560 RPM in: RPM min.: 3560

max.: out: max.:RATIO:

MODEL: 7209 MODEL: MODEL:SER NO.: SER NO.:RATING: RATING:BELT #: # BLADES:BRG#: (I) BRG#: BALL (I)BRG#: (O) BRG#: BALL (O)GEAR T: CT GEAR T: CT

SER NO.:V 480 P 3 A 109

pulley: ___IDBRG#: BALL 6312 (I)BRG#: BALL 6312 (O)H.P.: 100OTHER: OTHER: OTHER:

MFGR:WESTINGHOUSEMFGR:WESTINGHOUSE

MACHINE IDENT: 3 COND XFER PUMP AREA: NGS-3ROUTE:

3120


Construct a map of machine locations within the plant

This will help you to verify where you are during data collection and to decide on an efficient route - use the same identification number on machine, database and your map

MACHINE AND POINT IDENTIFICATIONSMACHINE AND POINT IDENTIFICATIONSMACHINE AND POINT IDENTIFICATIONSMACHINE AND POINT IDENTIFICATIONS


SAMPLE MACHINE LOCATION MAPSAMPLE MACHINE LOCATION MAPSAMPLE MACHINE LOCATION MAPSAMPLE MACHINE LOCATION MAP

BLDG. 101ADDITION

(ON SECOND FLOOR)

101B 101A

ABS CLEAN ROOM(INTERIOR ROOF)

AH23

AH20

AH19

AH21

AH22

101AAHU

MET-7

AHUSUP-7

101AAHU

MET-7

AHUSUP-7

(ROOF)

HEATTREAT VPUMP(GROUND)

01

02

SLA-1A SLA-1B

COOLING BLOWER

101A


From your knowledge of the machines build, operating characteristics and forcing frequencies set up the measurement details for each point. i.e.:-

–Measurement Parameters

–Alarm Levels (Overall and Bands )

–Optimum frequency span. (Fmax )

–Number of Lines of Information.

–Number of Averages

MEASUREMENT POINT SETUPMEASUREMENT POINT SETUPMEASUREMENT POINT SETUPMEASUREMENT POINT SETUP


Data collector batteries are in good condition and properly charged

Cables are in good operating condition

Check correct date and time in data collector

Ensure correct transducer sensitivity is entered in data collector or software

ENSURE CORRECT INSTRUMENT SETUPENSURE CORRECT INSTRUMENT SETUPENSURE CORRECT INSTRUMENT SETUPENSURE CORRECT INSTRUMENT SETUP


When using additional transducers

e.g.. temperature, current or proximity probes, ensure that :-

Operation is clearly understood

Instrument is correctly configured to accept the information

Proper sensitivity is entered

ENSURE CORRECT INSTRUMENT SETUPENSURE CORRECT INSTRUMENT SETUPENSURE CORRECT INSTRUMENT SETUPENSURE CORRECT INSTRUMENT SETUP


Motor3580 RPM

Gearbox1:1.7 ratio

Bull gear (68 teeth)

Blower6086 RPM

Pinion (40 teeth)

MTR DRIVEN GB AND BLOWER SKETCHMTR DRIVEN GB AND BLOWER SKETCHMTR DRIVEN GB AND BLOWER SKETCHMTR DRIVEN GB AND BLOWER SKETCH


.030

.060

.090

.120

.150

.180

.210

.240

.270

.300Peak Velocity (in/sec)

Frequency (CPM)

2400 4800 7200 9600 12000

1X Motor rpm (Fm) 1X Blower rpm (Fb)

2X Motor rpm (Fm)

3X Motor rpm (Fm)

No particular problem noted from this spectrum

0-12000 CPM SPECTRUM0-12000 CPM SPECTRUM0-12000 CPM SPECTRUM0-12000 CPM SPECTRUM


Peak Velocity (in/sec)

.030

.060

.090

.120

.150

.180

.210

.240

.270

.300

Frequency (CPM)

4800 9600 14400 19600 24000

1X Fm

1X Fb

2X Fm 3X Fm

2X Fb3X Fb

Slight mechanical looseness on the gearbox output shaft is indicated



240,000

.030

.060

.090

.120

.150

.180

.210

.240

.270


Frequency (CPM)

48,000 96,000 144,000 192,000

1XBPFO with cage frequency sidebands

2X BPFO3X BPFO

4X BPFO5X BPFO

SKF 22212 Bearing outer race defect is detected in addition to the mechanical looseness



.030

.060

.090

.120

.150

.180

.210

.240

.270


Frequency (CPM)

72,000 144,000 216,000 288,000 360,000

4X BPFO5X BPFO

3X BPFO2X BPFO

1X BPFO

Fb

2X Fb

1X GMF

1X Gear mesh frequency with bearing defectfrequency harmonics and slight mechanical looseness. Gear mesh looks normal.



1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Peak Acceleration (g’s)

Frequency (CPM)

156,000 312,000 468,000 624,000 780,000

Output gear and bearing problem noted

1X BPFO2X BPFO

3X BPFO

4X BPFO5X BPFO

1X GMF2X GMF

3X GMF

Blower speedsidebands




Rolling-element bearings

–About 120,000 CPM (2KHz)

Sleeve bearing machines

–Usually not to exceed 60,000CPM (1KHz)

Gear Drives

–Fundamental gear mesh frequency x 3.25


VIBRATION ANALYSIS


Every machine fault will generate a unique vibration characteristic.

Analysis involves a logical, systematic approach that can pinpoint the exact machine fault

Analysis is a process of elimination

A step by step procedure can be used to minimise wasted time

VIBRATION ANALYSISVIBRATION ANALYSISVIBRATION ANALYSISVIBRATION ANALYSIS


Establish “Baseline Data” Identify cause of excessive vibration Identify cause of significant vibration increase Identify cause of frequent component failures

– bearings, couplings, seals, gears... Identify cause of structural failures - foundation, piping,

mountings, welds...

DEFINE THE PROBLEM. WHY PERFORM AN DEFINE THE PROBLEM. WHY PERFORM AN ANALYSIS? STEP 1ANALYSIS? STEP 1

DEFINE THE PROBLEM. WHY PERFORM AN DEFINE THE PROBLEM. WHY PERFORM AN ANALYSIS? STEP 1ANALYSIS? STEP 1


Identify the source of a noise problem.

Identify why a machine tool fails to produce a quality part

– Surface finish

– Dimensional tolerances...

Machine does not meet performance standards such as those set by NEMA, ISO, and API

DEFINING THE PROBLEMDEFINING THE PROBLEMDEFINING THE PROBLEMDEFINING THE PROBLEM


When Did the Problem Start?

Where any recent changes made prior to the problem being noticed?

DETERMINE MACHINE HISTORY – STEP 2DETERMINE MACHINE HISTORY – STEP 2DETERMINE MACHINE HISTORY – STEP 2DETERMINE MACHINE HISTORY – STEP 2


Components eventually wear out - bearings, grouting, couplings, etc...

Corrosion or deposit build-up can affect the balance

Settling of bases can affect alignment

Blockage of filters can affect flow

Breakdown of lubrication

VIBRATION INCREASED GRADUALLY VIBRATION INCREASED GRADUALLY OVER TIMEOVER TIME

VIBRATION INCREASED GRADUALLY VIBRATION INCREASED GRADUALLY OVER TIMEOVER TIME


ALWAYS RUN ROUGH EVEN WHEN NEWALWAYS RUN ROUGH EVEN WHEN NEWALWAYS RUN ROUGH EVEN WHEN NEWALWAYS RUN ROUGH EVEN WHEN NEW

Resonance condition may exist

Machine / associated piping may have not been properly aligned

Not designed correctly for application

– i.e. Pump not operating on curve


Changes in machine speed or load.

Modifications to any machine component such as the base, foundation, piping, etc..

Replacement of parts

VIBRATION INCREASED ABRUPTLYVIBRATION INCREASED ABRUPTLYVIBRATION INCREASED ABRUPTLYVIBRATION INCREASED ABRUPTLY


DETERMINE MACHINE DETAILS - STEP 3DETERMINE MACHINE DETAILS - STEP 3DETERMINE MACHINE DETAILS - STEP 3DETERMINE MACHINE DETAILS - STEP 3

All machine speeds (rpm) Types of bearings Number of fan blades / impeller vanes Number of gear teeth Type of coupling Machine critical speeds/natural frequencies Background vibration sources


HAVE A MACHINE DIAGRAM HAVE A MACHINE DIAGRAM HAVE A MACHINE DIAGRAM HAVE A MACHINE DIAGRAM


Loose or Missing Bolts Cracks in the Base, Foundation, Welds Leaking Seals Worn Belts Excessive corrosion or build-up of deposits Perform a Slow Motion Study

VISUAL INSPECTION – STEP 4VISUAL INSPECTION – STEP 4VISUAL INSPECTION – STEP 4VISUAL INSPECTION – STEP 4


Suction and discharge piping on pumps Externally mounted components Background sources Compare overall levels across all mounting

interfaces for looseness Compare overall levels at machine feet for “soft

foot”

PROBING STUDDIES – STEP 5PROBING STUDDIES – STEP 5PROBING STUDDIES – STEP 5PROBING STUDDIES – STEP 5


COMPARING LEVELS ACROSS COMPARING LEVELS ACROSS INTERFACESINTERFACES

COMPARING LEVELS ACROSS COMPARING LEVELS ACROSS INTERFACESINTERFACES


Run machine at normal load, speed, temperature, pressure, etc...

Use the same amplitude scale for all FFT readings (normalisation)

Define spectral parameters that cover important frequencies

OBTAIN TRI-AXIAL SPECTRA – STEP 6OBTAIN TRI-AXIAL SPECTRA – STEP 6OBTAIN TRI-AXIAL SPECTRA – STEP 6OBTAIN TRI-AXIAL SPECTRA – STEP 6


Take readings with:

–Machine shut down to analyse background sources

–Machine idling (no machining) to identify drive related problems

–Machine under normal operating conditions to identify cutting, drilling, or grinding operation problems (chatter)

MACHINE TOOLMACHINE TOOLMACHINE TOOLMACHINE TOOL


USE SAME AMPLITUDE SCALEUSE SAME AMPLITUDE SCALEUSE SAME AMPLITUDE SCALEUSE SAME AMPLITUDE SCALE


Fmax needs to be high enough to catch all defect frequencies in machine.

Resolution needs to be sharp enough to separate closely spaced frequencies.

Some machines may require more than one set of FFT’s.

SET FFT PARAMETERS PROPERLYSET FFT PARAMETERS PROPERLYSET FFT PARAMETERS PROPERLYSET FFT PARAMETERS PROPERLY


Identify the machine component with the vibration problem (motor, pump, gears).

Reduce the number of possible problems from several hundred to only a few

INTERPRETING THE DATAINTERPRETING THE DATAINTERPRETING THE DATAINTERPRETING THE DATA


Most vibration problems generate frequencies related to the rotating speed.

Frequencies at 1x rpm, 2x rpm, 3x rpm, 4x rpm, etc.

IDENTIFICATION BASED ON FREQUENCYIDENTIFICATION BASED ON FREQUENCYIDENTIFICATION BASED ON FREQUENCYIDENTIFICATION BASED ON FREQUENCY


Component with highest amplitude is usually problem component.

Some exceptions such as Misalignment of direct coupled machine

IDENTIFYING PROBLEMS BASED ON IDENTIFYING PROBLEMS BASED ON AMPLITUDEAMPLITUDE

IDENTIFYING PROBLEMS BASED ON IDENTIFYING PROBLEMS BASED ON AMPLITUDEAMPLITUDE


FrequencyIn TermsOf RPM Most Likely Causes Other Possible Causes & Remarks

1 x RPM Unbalance 1) Eccentric journals, gears or pulleys2) Misalignment or bent shaft - If high axial vibration3) Bad Belts - If RPM of belt4) Resonance5) Reciprocating forces6) Electrical problems7) Looseness8) Distortion - soft feet or piping strain

2 x RPM Mechanical 1) Misalignment - if high axial vibrationLooseness 2) Reciprocating forces

3) Resonance4) Bad belts - if 2 x RPM of belt

3 x RPM Misalignment Usually a combination of misalignment and excessive axial clearances (looseness).

Less than Oil Whirl (less 1) Bad drive belts1 x RPM than 1/2 RPM 2) Background vibration

3) Sub-harmonic resonance4) "Beat" Vibration

Synchronous Electrical Common electrical problems include broken rotor bars, eccentric(A.C. Line Problems rotor unbalanced phases in poly-phase systems, unequalFrequency) air gap.2 x Synch. Torque Pulses Rare as a problem unless resonance is excitedFrequencyMany Times RPM Bad Gears Gear teeth times RPM of bad gear(Harmonically Aerodynamic Forces Number of fan blades times RPMRelated Freq.) Hydraulic Forces Number of impeller vanes times RPM

Mechanical Looseness May occur at 2, 3, 4 and sometimes higher harmonics ifsevere looseness

Reciprocating ForcesHigh Frequency Bad Anti-Friction 1) Bearing vibration may be unsteady - amplitude and frequency(Not Harmonically Bearings 2) Cavitation, recirculation and flow turbulence cause random,Related) high frequency vibration

3) Improper lubrication of journal bearings (Friction excited vibration)4) Rubbing

FREQUENCY RELATED PROBLEMSFREQUENCY RELATED PROBLEMSFREQUENCY RELATED PROBLEMSFREQUENCY RELATED PROBLEMS


How do radial (horizontal and vertical) readings compare to each other.

How do radial readings compare with axial measurements

COMPARISON BY DIRECTIONCOMPARISON BY DIRECTIONCOMPARISON BY DIRECTIONCOMPARISON BY DIRECTION


Relative stiffness between the measurement directions needs to be established

Ratios beyond 4:1 are unusual and indicate an abnormal condition such as looseness or resonance

COMPARE HORIZ & VERTICAL READINGSCOMPARE HORIZ & VERTICAL READINGSCOMPARE HORIZ & VERTICAL READINGSCOMPARE HORIZ & VERTICAL READINGS


COMPARING RADIAL AMPLITUDECOMPARING RADIAL AMPLITUDECOMPARING RADIAL AMPLITUDECOMPARING RADIAL AMPLITUDE


Only a few machine defects can cause high axial readings

–These include Misalignment, Bent Shafts, or Unbalance of Overhung Rotors.

General Rule:

–Any time the axial amplitude exceeds 50% of the highest radial, these defects should be strongly considered

COMPARING RADIAL AND AXIALCOMPARING RADIAL AND AXIALCOMPARING RADIAL AND AXIALCOMPARING RADIAL AND AXIAL


SINUSOIDAL WAVEFORMSINUSOIDAL WAVEFORMSINUSOIDAL WAVEFORMSINUSOIDAL WAVEFORM


Sinusoidal WaveformSinusoidal Waveform


Square WaveSquare Wave


Spike - Pulse WaveformSpike - Pulse Waveform


Side-Band FrequenciesSide-Band Frequencies

The resultant of Amplitude Modulation The Carrier Frequency is the centre frequency which

is also the defect frequency The two sidebands are equally spaced from the

Carrier by the modulation frequency


AM & FMAM & FMAM & FMAM & FM


Typical Side-BandsTypical Side-Bands


Step 7 - Is Vibration Directional Step 7 - Is Vibration Directional

Directional is non-uniform vibration.

Non-directional is uniform vibration.

Unbalance and bent shafts are uniform, most other types are directional.

Misalignment, eccentricity, and looseness cause directional vibration


Directional Versus Non-Directional VibrationDirectional Versus Non-Directional Vibration

Comparing horizontal, vertical, and axial FFT’s.

Comparing vertical and horizontal phase.

Multiple radial amplitude measurements


Comparative Horizontal & Vertical Phase Comparative Horizontal & Vertical Phase


Multiple Radial MeasurementsMultiple Radial Measurements


COMMON PROBLEMSCOMMON PROBLEMS

Unbalance Bent Shafts Misalignment Looseness Eccentricity Problems Resonance Belt Drive Problems

Defective Rolling Element Bearings

Sleeve Bearing Problems Electric (Induction) Motor

Problems Gear Problems


UNBALANCEUNBALANCE

ONLY causes vibration at 1x rpm. Amplitude is proportional to the unbalance Amplitudes are higher in the radial direction

unless the rotor is overhung Phase readings will be stable Phase readings will shift 90 degrees when

pickup is shifted 90 degrees (60o to 120o phase difference is allowable)


UNBALANCEUNBALANCE

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 UnbalanceTypical Spectrum For Unbalance


BENT SHAFTSBENT SHAFTS

Caused by:

–Manufacturing errors

–Mishandling during transportation

–“Bow” due to thermal growth

Rotors can be kinked or bowed


BENT SHAFTSBENT SHAFTS

Predominant vibration at 1x rpm which can be accompanied by a 2x rpm peak.

Axial vibration amplitude exceeds 50% of highest radial amplitude.

Radial vibration is uniform

Axial phase analysis needs to be used to verify problem and type of bend


Typical FFT for Bent ShaftTypical FFT for Bent Shaft


Axial Phase ReadingsAxial Phase Readings

Determine axial twisting or planar motion Taken at 4 positions around bearing face Corrections need to be made for transducer orientation


Identifying a Shaft with a KinkIdentifying a Shaft with a Kink


Kink in the ShaftKink in the Shaft

Use axial phase measurements to see twisting motion

– 180o difference between top and bottom

– 180o difference between left and right Shows 1x rpm peak and possible 2x rpm Condition verified with dial indicator Appears the same as a cocked bearing, but

axial readings show similar amplitudes around bearing face for kink


Identifying a Simple BowIdentifying a Simple Bow

Axial amplitude and phase readings around the bearing face will be uniform

Shows 1x rpm peak with possible 2x rpm Axial phase readings across the support bearings show 180 degree

phase difference Correct for orientation of transducer


Axial Phase Indicating Planar Motion Axial Phase Indicating Planar Motion from Shaft Bowfrom Shaft Bow


MISALIGNMENTMISALIGNMENT

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


MISALIGNMENTMISALIGNMENT

Forces shared by driver and driven (not localised)

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 MisalignmentThree Types of Misalignment

Combination (most common) Angular Parallel or Offset


General Characteristics Of MisalignmentGeneral Characteristics Of Misalignment

Radial vibration is highly directional 1X, 2x, and 3x running speed depending on type

and extent of misalignment

–Angular 1x rpm axial

–Parallel 2x rpm radial (H & V)

–Combination 1,2,3x rpm radial and axial


Typical Spectrum for MisalignmentTypical Spectrum for Misalignment


Angular MisalignmentAngular Misalignment

Produces predominant 1x rpm component Marked by 180 degree phase shift across the

coupling in the axial direction


Parallel Or Offset MisalignmentParallel 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 MisalignmentTypical Spectrum for Misalignment


Axial Phase Showing MisalignmentAxial Phase Showing Misalignment


Other Types Of MisalignmentOther Types Of Misalignment


BEARING COCKED ON SHAFTBEARING COCKED ON SHAFT

Rarely causes a problem unless there is some other exciting force to create radial vibration and magnifies the misalignment

COCKED SLEEVE BEARING

Comparative axial phase will show large amplitude discrepancy and same phase as kink in bearing


LOOSENESSLOOSENESSLOOSENESSLOOSENESS

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 LoosenessTwo 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 SystemLooseness 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


Spectrum for Looseness of Rotating SystemSpectrum for Looseness of Rotating System


Spectrum Looseness of Rotating SystemSpectrum Looseness of Rotating System


Looseness Of Support SystemLooseness 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 SystemLooseness Of Support System


ECCENTRICITYECCENTRICITY

Produces vibration at 1xrpm of the eccentric component

Vibration is highly directional Pulleys, gears, and chain sprockets will show

directional vibration acting on a line between the two centres

Slow motion studies and dial indicators can assist confirmation

Balancing will give only limited success


Eccentricity Gears and SheavesEccentricity Gears and Sheaves

Gears have variation in mating force along centreline of gears

Sheaves have vibration along centreline of driver and driven pulley


Eccentric Armatures and BearingsEccentric Armatures and Bearings

Eccentric Motor Armature causes unbalanced magnetic forces

Eccentric bearings rarely cause a problem because of precision manufacture


Typical Spectrum For EccentricityTypical Spectrum For Eccentricity


RESONANCERESONANCE

Every machine element has a natural frequency(s) based on mass and stiffness

Resonance occurs when a forcing frequency coincides with a one of these natural frequencies


VIBRATION DUE TO RESONANCEVIBRATION DUE TO RESONANCE

Every object, including every element or part of a machine, has a “natural frequency” or a frequency at which “it likes to vibrate”

Determined by the machine’s mass and stiffness Does not cause vibration but serves as a “mechanical

amplifier” (10x-100x) Resonance is a very common cause of excessive

vibration because:– Machines consist of many individual elements– Stiffness of each machine component differs in

all directions, causing several natural frequencies


Identifying ResonanceIdentifying Resonance

Vibration will be Highly Directional Changing the Exciting Forcing Frequency Change the mass or stiffness of the suspected

resonant machine component Perform a Bump Test


RESONANCERESONANCE

Occurs when Forcing Frequency is within +/- 20% of Natural Frequency


Bump Test Results to Confirm Resonance Bump Test Results to Confirm Resonance


GEAR VIBRATIONGEAR VIBRATION

DIAGNOSTICS DIAGNOSTICS

GEAR VIBRATIONGEAR VIBRATION

DIAGNOSTICS DIAGNOSTICS


CALCULATION OF GEAR MESH CALCULATION OF GEAR MESH FREQUENCIESFREQUENCIES

CALCULATION OF GEAR MESH CALCULATION OF GEAR MESH FREQUENCIESFREQUENCIES

20 TEETH20 TEETH

51 TEETH51 TEETH

1700 RPM1700 RPM

31 TEETH31 TEETH

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


GEARS NORMAL SPECTRUMGEARS NORMAL SPECTRUM

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

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

frequencies are present

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

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

frequencies are present

14 teeth

8 teeth GMF= 21k CPM

2625 rpm

1500 rpm


GEARS TOOTH WEARGEARS TOOTH WEAR

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

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

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

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

14 teeth1500 rpm

8 teeth2625 rpm

GMF = 21k CPM


GEARS TOOTH LOADGEARS TOOTH LOAD

Gear Mesh Frequencies are often sensitive to load

High GMF amplitudes do not necessarily indicate a problem

Each analysis should be performed with the system at maximum load

Gear Mesh Frequencies are often sensitive to load

High GMF amplitudes do not necessarily indicate a problem

Each analysis should be performed with the system at maximum load


GEARS GEAR ECCENTRICITY AND BACKLASHGEARS GEAR ECCENTRICITY AND BACKLASH

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

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

frequency

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

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

frequency


GEARS GEAR MISALIGNMENTGEARS GEAR MISALIGNMENT

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

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

Important to set Fmax high enough to capture at least2X GMF

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

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

Important to set Fmax high enough to capture at least2X GMF


GEARS CRACKED / BROKEN TOOTHGEARS CRACKED / BROKEN TOOTH

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

It will excite the gear natural frequency which will be sidebanded by the running speed fundamental

Best detected using the time waveform Time interval between impacts will be the reciprocal of

the 1X RPM

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

It will excite the gear natural frequency which will be sidebanded by the running speed fundamental

Best detected using the time waveform Time interval between impacts will be the reciprocal of

the 1X RPM

TIME WAVEFORM


GEARS HUNTING TOOTHGEARS HUNTING TOOTH

Vibration is at low frequency and due to this can often be missed

Synonymous with a growling sound The effect occurs when the faulty pinion and gear teeth

both enter mesh at the same time Faults may be due to faulty manufacture or mishandling

Vibration is at low frequency and due to this can often be missed

Synonymous with a growling sound The effect occurs when the faulty pinion and gear teeth

both enter mesh at the same time Faults may be due to faulty manufacture or mishandling

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


GEAR BOX LIMITATIONSGEAR BOX LIMITATIONSGEAR BOX LIMITATIONSGEAR BOX LIMITATIONS


PUMPS AND BEATSPUMPS AND BEATSPUMPS AND BEATSPUMPS AND BEATS


FLOW INDUCED VIBRATIONFLOW INDUCED VIBRATION

Cavitation, Recirculation, and Flow Turbulence

Inherent in Pumps and Fans

Varies significantly with Load

Blade Pass Frequency = # Blades x RPM


CAVITATIONCAVITATION

Pumps forced to operate will below their designed capacity experience cavitation

Lack of suction pressure creates a vacuum pockets in the fluid that are unstable and can collapse or implode.

Implosions excite natural frequencies.

Show up as “haystack” of frequencies in the 20,000 CPM to 150,000 CPM range


Flow Related ConsiderationsFlow Related Considerations

BPF may excite Resonance

Manufacturing Errors

Piping and Duct Configuration

– API 610 specifies a five x diameter rule for inlet elbows

Design Capacity (Check Pump Curve)


HYDRAULIC AND AERODYNAMIC FORCESHYDRAULIC AND AERODYNAMIC FORCESHYDRAULIC AND AERODYNAMIC FORCESHYDRAULIC AND AERODYNAMIC FORCES

If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitude

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

Eccentric rotor can cause amplitude at BPF to be excessive

If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitude

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

Eccentric rotor can cause amplitude at BPF to be excessive

BPF = BLADE PASS FREQUENCY



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

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

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

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

FLOW TURBULENCEFLOW TURBULENCE


Case Study: Flow ProblemCase Study: Flow Problem


Spectra for Flow ProblemsSpectra for Flow Problems



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

Normally indicates inadequate suction pressure Erosion of impeller vanes and pump casings may occur if

left unchecked Sounds like gravel passing through pump

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

Normally indicates inadequate suction pressure Erosion of impeller vanes and pump casings may occur if

left unchecked Sounds like gravel passing through pump

CAVITATIONCAVITATION


BEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATIONBEAT VIBRATION

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

The wideband spectrum will show one peak pulsating up and down

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

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

The wideband spectrum will show one peak pulsating up and down

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

WIDEBAND SPECTRUM

ZOOMSPECTRUM

F1 F2


BELTBELT VIBRATIONVIBRATIONBELTBELT VIBRATIONVIBRATION


Often 2X RPM is dominant Amplitudes are normally unsteady, sometimes pulsing with

either driver or driven RPM Wear or misalignment in timing belt drives will give high

amplitudes at the timing belt frequency Belt frequencies are below the RPM of either the driver or the

driven

Often 2X RPM is dominant Amplitudes are normally unsteady, sometimes pulsing with

either driver or driven RPM Wear or misalignment in timing belt drives will give high

amplitudes at the timing belt frequency Belt frequencies are below the RPM of either the driver or the

driven

WORN, LOOSE OR MISMATCHED BELTSWORN, LOOSE OR MISMATCHED BELTS

BELT FREQUENCYHARMONICS

BELT PROBLEMSBELT PROBLEMSBELT PROBLEMSBELT PROBLEMS


Pulley misalignment will produce high axial vibration at 1X RPM

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

Pulley misalignment will produce high axial vibration at 1X RPM

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

1X DRIVEROR DRIVEN

BELT / PULLEY MISALIGNMENTBELT / PULLEY MISALIGNMENT



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

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

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

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

RADIAL1X RPM OFECCENTRICPULLEY

ECCENTRIC PULLEYSECCENTRIC PULLEYS



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

Belt natural frequency can be changed by altering the belt tension

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

Belt natural frequency can be changed by altering the belt tension

BELT RESONANCEBELT RESONANCE RADIAL

1X RPM

BELT RESONANCE



Reduce premature bearing failureReduce premature bearing failureReduce premature bearing failureReduce premature bearing failure

Poor installation - 16% of all premature bearing failures are caused by poor installation . Professional installation, using specialized tools and techniques, is a positive step toward achieving maximum machine uptime.

Poor lubrication - 36% of all premature bearing failures are caused by incorrect specification and inadequate application of the lubricant. Because bearings are the least accessible components of machinery, neglected lubrication compounds the problem.

Contamination - 14% of all premature bearing failures are attributed to contamination problems. A bearing will not operate efficiently unless both the bearing and its lubrication are isolated from contamination.

Fatigue - 34% of all premature bearing failures are caused by overloaded, incorrectly serviced or neglected machines. Sudden failures can be avoided since bearings emit “early warning” signals which can be detected using condition monitoring equipment.


Construction of bearingsConstruction of bearingsConstruction of bearingsConstruction of bearings

Outer Ring Raceway

Outer Ring LandInner Ring

Inner Ring Raceway

Rolling Element

Inner Ring Land

Outer Ring

O.D. Surface

Cage

Bore Surface

Side Faces


Bearing loadBearing loadBearing loadBearing load


Bearing typesBearing typesBearing typesBearing types

Double row angular contact ball bearing

Single row deep groove ball bearing

Single row angular contact ball bearing

Self-aligning ball bearing

Cylindrical roller bearing

Spherical roller bearing

Tapered roller bearing

Needle roller bearing


BEARING FAILURESBEARING FAILURESBEARING FAILURESBEARING FAILURES


L10h = 1,000,00060 (n) ( )C

P

p

Where:n = rotational speed (rpm)C = dynamic bearing capacityP = equivalent load appliedp = 3 for ball bearingsp = 10/3 for roller bearingsNote: C/P target = 8 to 12

Basic L10 Fatigue Life


Lubrication conditionsLubrication conditionsLubrication conditionsLubrication conditions

Full lubrication Marginal / inadequate lubrication


ContaminationContaminationContaminationContamination

– When a hard particles > 5 microns is forced through the gap of around 0.5 microns a dent is formed in the raceway

– Even soft particles, if large enough, will produce dents in the very hard raceway


Contamination - Surface Fatigue

1) A dent is formed 2) A crack arises

3) Crack Propagation 4) Flaking

ContaminationContaminationContaminationContamination


Bearing arrangementsBearing arrangementsBearing arrangementsBearing arrangements

Locating Non-Locating


Temperature MountingTemperature MountingTemperature MountingTemperature Mounting

Hot Plate Induction Heater


Bearing TerminologyBearing Terminology


BEARING FAILUREBEARING FAILURE

Four failure stages

–Stage 1: Visible flaw, only seen in Spike Energy

–Stage 2 : Size of flaw increases, natural frequency of bearing appears

–Stage 3 : Bearing defect frequencies appear

–Stage 4 : The last hurrah!, Spike Energy may actually decline


ROLLING ELEMENT BEARINGS STAGE 1 ROLLING ELEMENT BEARINGS STAGE 1

Earliest indications in the ultrasonic range These frequencies evaluated by Spike EnergyTM gSE,

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

first stage

gSE

ZONE BZONE A ZONE C ZONE D



Slight defects begin to ring bearing component natural frequencies

These frequencies occur in the range of 30k-120k CPM At the end of Stage 2, sideband frequencies appear above and

below natural frequency Spike Energy grows e.g. 0.25-0.50gSE

ZONE A ZONE B ZONE C ZONE D

gSE


Stage 2 Of Bearing FailureStage 2 Of Bearing Failure



Bearing defect frequencies and harmonics appear Many defect frequency harmonics appear with wear the

number of sidebands grow Wear is now visible and may extend around the periphery of

the bearing Spike Energy increases to between 0.5 -1.0 gSE

ZONE A ZONE B ZONE C ZONE D

gSE



Discreet bearing defect frequencies disappear and are replaced by random broad band vibration in the form of a noise floor

Towards the end, even the amplitude at 1 X RPM is effected High frequency noise floor amplitudes and Spike Energy may in fact decrease Just prior to failure gSE may rise to high levels

gSE

ZONE A ZONE B ZONE C

High just priorto failure


Bearing Database Bearing Database


Paper Roll Bearing With Multiple Harmonics Paper Roll Bearing With Multiple Harmonics Of BPFOOf BPFO


Case Study: Defective Rolling Element Case Study: Defective Rolling Element BearingBearing


Oil WhirlOil Whirl

Pressure lubricated sleeve-type bearings operating above critical speed

Occurs in range of 0.42-0.48x rpm Oil film pushes shaft around in housing Only causes problems when oil whirl dominates

normal static or dynamic load


Oil WhipOil Whip

Occurs in machines operating above 2x rotor critical speed

Oil film breaks down and shaft whirls at first critical speed


STRATEGIC APPROACH TO MOTOR HEALTH DIAGNOSIS

STRATEGIC APPROACH TO MOTOR HEALTH DIAGNOSIS

ELECTRICAL ELECTRICAL DIAGNOSTICSDIAGNOSTICSELECTRICAL ELECTRICAL

DIAGNOSTICSDIAGNOSTICS


ELECTRICAL PROBLEMELECTRICAL PROBLEMELECTRICAL PROBLEMELECTRICAL PROBLEM

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

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

Soft foot can produce an eccentric stator

STATOR ECCENTRICITYSTATOR ECCENTRICITYSHORTED LAMINATIONSSHORTED LAMINATIONSAND LOOSE IRONAND LOOSE IRON


ELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMSELECTRICAL PROBLEMS

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

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

Common values of FP range from 20 - 120 CPM

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

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



• Electrical line frequency.(Electrical line frequency.(FLFL) = ) = 50Hz = 3000 cpm.50Hz = 3000 cpm. 60HZ = 3600 cpm60HZ = 3600 cpm• No of poles.No of poles. ((PP) )

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

• Synchronous speed (Synchronous speed (NsNs)) = = 2xFL2xFL PP• Slip frequency ( Slip frequency ( FFS S )= )= Synchronous speed - Rotor rpm.Synchronous speed - Rotor rpm.

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

• Electrical line frequency.(Electrical line frequency.(FLFL) = ) = 50Hz = 3000 cpm.50Hz = 3000 cpm. 60HZ = 3600 cpm60HZ = 3600 cpm• No of poles.No of poles. ((PP) )

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

• Synchronous speed (Synchronous speed (NsNs)) = = 2xFL2xFL PP• Slip frequency ( Slip frequency ( FFS S )= )= Synchronous speed - Rotor rpm.Synchronous speed - Rotor rpm.

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

FREQUENCIES GENERATEDFREQUENCIES GENERATEDFREQUENCIES GENERATEDFREQUENCIES GENERATED


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

2X line frequency sidebands on rotor bar pass frequency (RBPF) indicates loose rotor bars.

Often high levels at 2X & 3X rotor bar pass frequency and only low level at 1X rotor bar pass frequency.

ROTOR PROBLEMSROTOR PROBLEMS



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

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

making contact

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



Loose stator coils in synchronous motors generate high amplitude at Coil Pass Frequency

The coil pass frequency will be surrounded by 1X RPM sidebands

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



DC motor problems can be detected by the higher than normal amplitudes at SCR firing rate

These problems include broken field windings Fuse and control card problems can cause high amplitude peaks at

frequencies of 1X to 5X Line Frequency

DC MOTOR PROBLEMSDC MOTOR PROBLEMS



POLEPOLE

MINIMUMMINIMUM

POLEPOLE

MAXIMUMMAXIMUM

MAXMAX

MINMIN

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


MOTOR CURRENT ANALYSISMOTOR CURRENT ANALYSIS

• Diagnoses range of ac motor faults

• Can be integrated with vibration

• Measurement trending


AC MOTOR FAULTSAC MOTOR FAULTSAC MOTOR FAULTSAC MOTOR FAULTS

poor brazingoscillatingload

loss ofphase supply

crackedend rings

bent shaft

brokenrotor bars

air gapeccentricity

winding insulationdegradation


AC MOTOR CURRENT SPECTRUMAC MOTOR CURRENT SPECTRUMAC MOTOR CURRENT SPECTRUMAC MOTOR CURRENT SPECTRUM

currentclamp

datacollector


FAULT DIAGNOSISFAULT DIAGNOSISFAULT DIAGNOSISFAULT DIAGNOSIS

primary rotorfault sidebands

good motor bad motor


HOW DOES IT FIT IN A CMPHOW DOES IT FIT IN A CMPHOW DOES IT FIT IN A CMPHOW DOES IT FIT IN A CMP

Approximately 10% of motor failures are rotor related.

Significant threat of secondary damage.

Most motors are healthy.

On-line non-intrusive test.

Easy to do - data collector.


Solving Those Solving Those

Difficult Vibration Difficult Vibration

Problems Problems


OPERATING SHAPE ANALYSISOPERATING SHAPE ANALYSISOPERATING SHAPE ANALYSISOPERATING SHAPE ANALYSIS

• Foundation problemsFoundation problems

• Static/coupled unbalanceStatic/coupled unbalance

• MisalignmentMisalignment

• ResonanceResonance

• Case distortionCase distortion


ODS MEASUREMENTODS MEASUREMENTODS MEASUREMENTODS MEASUREMENT


SHAPE 1SHAPE 1SHAPE 1SHAPE 1


SOUNDSOUNDSOUNDSOUND

ENTEK IRD


•Sound is a pressure oscillation in a fluid. •Which moves radially away from the source that produces it.

•Sound radiates by, or is “propagated” by, wave motion through the fluid or “medium.”

•The four characteristics of the wave motion are: Amplitude, Frequency, velocity and wavelength.

BASIC CHARACTERISTICS BASIC CHARACTERISTICS BASIC CHARACTERISTICS BASIC CHARACTERISTICS


• The velocity of sound is essentially “fixed”.

•It is constant for the medium in which it travels

•In air it travels at 1120 feet per second and 340 metres per sec in air.

•Changes slightly due to temperature and pressure variations.

VELOCITYVELOCITYVELOCITYVELOCITY


The Wavelength is the distance between similar points on two adjacent “waves” and is determined both by the velocity [c] and the frequency [f] at which the waves are propagated, or:

(feet per cycle) = c (feet/cycle) F (cycles/sec)

WAVELENGTHWAVELENGTHWAVELENGTHWAVELENGTH


•It is determined by the source causing it.

•Common source of sound is a vibrating solid.

•Vibrating or oscillating motion of the solid causes pressure changes.

•The pressure oscillation frequency is the same as the vibration frequency of the solid.

•Number of individual components generate different frequency, hence the “overall” sound will contain an equal number of individual “pressure oscillations” (or sound) frequencies.

FREQUENCYFREQUENCYFREQUENCYFREQUENCY


• Is determined by how much the medium is alternately compressed and rarefied.

• The amplitude is a measure of the energy imparted to the medium by the source.

• The initial energy imparted to the medium dissipates with distance.

• Energy is imparted by the source to a “receiver” (such as a microphone, or the ear).

• Sound amplitude is measured with an instrument in terms of the pressure level changes.

• Sound amplitude” is more commonly called “Sound Pressure Level” SPL.

AMPLITUDEAMPLITUDEAMPLITUDEAMPLITUDE


• In addition to the “sound pressure level, the term “sound level” is also commonly used in place of sound amplitude.

• If sound is measured with an instrument that is fully responsive to all frequencies of sound, then the measured value will be in terms of “sound pressure level”.

• It will measure what is actually “out there” or the true pressure level.

SOUND PRESSURE LEVEL SOUND PRESSURE LEVEL SOUND PRESSURE LEVEL SOUND PRESSURE LEVEL


SOUND LEVELSOUND LEVELSOUND LEVELSOUND LEVEL

• Instruments designed to work the way our ear works.

• Our ear is responsive to some frequencies but less responsive to others.

• Such instruments are called sound level reading; that is, they are not meant to measure in terms of actual sound pressure.


•The generally accepted definition of noise is simply “unwanted sound.”

•This includes everything from the drip of a tap in the middle of the night to the roar of an aircraft engine as it leaves the runway.

•It can even include music if it interferes with the work or concentration of the listener.

•To be considered noise all that is desired is that the sound is undesirable to the listener.

NOISENOISENOISENOISE


Sound or noise can be generated in three ways.

1) Vibrations of solid structures such as machines or walls, which alternately compress and rarefy the air in contact with these structures.

•The rate or frequency at which these structures vibrate determines the frequency of the sound that is radiated.

2) The movement of air over solid structures can also generate sounds. (example is the old type factory whistle or siren.)

•Fast moving air across the structure create sounds. (example of this is the pipe organ.)

•The flow of air over ventilation grills or fan blades.

•3) Turbulent mixing of fast moving air with relation to slow moving air.(noise is generated by a jet engine.)

GENERATION OF NOISEGENERATION OF NOISEGENERATION OF NOISEGENERATION OF NOISE


• Sound, or noise, is measured in units called “decibels.

• It is abbreviated to “dB.”

• Easy to use as compared to microns or millimetres.

• The levels of a number of common place sources of noise are given to provide this feel.

DECIBELDECIBELDECIBELDECIBEL


• Tremendous range of sound levels that the human ear can hear.

• Sound pressure levels of interest for engineering purposes cover a ratio of one billion to one (109 to 1).

• Inconvenient to handle with conventional linear units such as lb/in 2or microbars.

•The decibel provides a logarithmic scale, which compresses that huge linear scale of one billion to one into a decibel (logarithmic) range of only 180 to one.

WHY DECIBELWHY DECIBELWHY DECIBELWHY DECIBEL


Sound pressure level is defined by the following equation:

SPL = Sound Pressure Level

SPL = 20 log 10 Measured Sound Pressure (microbar)

Reference Sound Pressure (microbar)

Where Reference Sound Pressure = 0.0002 microbar or 20 micronewtons per square metre).

100 kpa = 1 bar

WHY DECIBELWHY DECIBELWHY DECIBELWHY DECIBEL


WHICH SCALE IS BETTERWHICH SCALE IS BETTERWHICH SCALE IS BETTERWHICH SCALE IS BETTER


• Where high noise levels occur in areas of work.

• Levels are governed by noise which can cause personnel fatigue and efficiency loss.

• Levels of acceptability for noise in different areas and conditions is different.

TYP. INDUSTRIAL NOISE LEVELTYP. INDUSTRIAL NOISE LEVELTYP. INDUSTRIAL NOISE LEVELTYP. INDUSTRIAL NOISE LEVEL


Noise Level dB(A)

Communication Required Typical activity or working area

110 Communication nearly impossible. Maximum shouting required at a distance of one foot or less

Deafening

100 Shouting required. Communication difficult even at one foot distance. Inside a workshop or machinery area

90 Shouting required at one foot. Maximum level at which a telephone can be used. Very loud

85 Raised voice can be understood at two feet. All working areas; For most tasks, worker efficiency is affected above this level.

70 Telephone use not a problem up to this level. Normal voice can be understood at three feet distance.

Machine shop, restaurants, busy department store

65 Secretarial offices

55 Normal voice can be understood at 12 feet distance Conference room, class room

50 Private office, drafting room, where close exacting work is required

30 Broadcast studio

ACCEPTANCE CHARTACCEPTANCE CHARTACCEPTANCE CHARTACCEPTANCE CHART


• It functions over an extremely wide range of amplitudes and frequencies

• Can detect very small changes or differences in amplitude and frequency.

•With experience can judge the actual frequency (or tone) of a specific sound.

• In judging loudness, the ear tends to respond poorly to frequencies near to low and high ends of a range of 20 Hz to 10 kHz. i.e. from about 200 Hz down to 20 Hz.

• Sounds having frequencies between the range of 200 Hz and 6000 Hz are heard essentially as their actual levels (or even amplified slightly).

• Another factor in this poor response characteristic of the ear is that as sound pressure level increases the response improves.

•For example, at 20 Hz an 80 dB SPL will be heard as a 20 dB sound (response error of 60 dB), whereas a 130 dB SPL will be heard as a 100 dB sound (an error of only 30 dB).

WORKING OF THE EARWORKING OF THE EARWORKING OF THE EARWORKING OF THE EAR


• Sound is often measured in conjunction with a problem related to human hearing.

• It has been found desirable in many cases to use instrumentation which measures sound in a manner similar to the human ear.

•To do this, sound level meters and analysers are electronically tuned to hear poorly at low and high frequencies and hear best at around 4 kHz.

•The electronics which generate this kind of response are called A, B and C weightings.

A, B & C WEIGHTINGA, B & C WEIGHTINGA, B & C WEIGHTINGA, B & C WEIGHTING


• The ear responds differently to sounds to sounds of different levels.

• For low level sounds (below 50 dB), the A weighting best approximates the human ear.

• From 55 to 85 dB the C weighting.

• For data recording it is necessary to specify what weighting is being used. For example, the sound levels are recorded: 50 dB (A) or 75 dB(B) or 92 dB(C) etc.

• Regardless of the level of sound. Most environmental requirements ask for the A weighting to be applied.

WHEN TO USE A, B & C WEIGHTINGWHEN TO USE A, B & C WEIGHTINGWHEN TO USE A, B & C WEIGHTINGWHEN TO USE A, B & C WEIGHTING


• The selection is generally governed by the standard under which the noise measurement is being made.

• Most environmental standards use the A weighting.

• If the requirement is that the degree to which communication is hindered or impaired has to be assessed then the A weighting is used.

• If the requirement is to assess or track down the noise from machinery then the C weighting is used.

• This weighting is also used for measuring the sound outputs of musical instruments or sound systems.

•The B weighting is rarely used and is sometimes not available in sound level meters.

WHEN TO USE A, B & C WEIGHTINGWHEN TO USE A, B & C WEIGHTINGWHEN TO USE A, B & C WEIGHTINGWHEN TO USE A, B & C WEIGHTING


A PAPER

ON

INTRINSIC SAFETY


INTRINSIC SAFETY & IMPORTANCEINTRINSIC SAFETY & IMPORTANCEINTRINSIC SAFETY & IMPORTANCEINTRINSIC SAFETY & IMPORTANCE

Generally referred to as an energy limitation protection technique.

Used in areas where gasses, volatile chemicals and fine dusts are processed and used.

The smallest spark of electrical energy can set off a dangerous explosion.

Instruments used in these environments must be incapable of generating energy sufficient to cause ignition.

In earlier days instruments installed in these hazardous areas were off pneumatic design.

Semiconductor, (Integrated Circuits) have insufficient power to ignite most of the gases.

Intrinsically safe devices help us from segregating the instruments in purged, explosion-proof containers as done in the past and were found to be extremely costly in terms of design, installation, and serviceability.


IGNITION TEMPERATUREIGNITION TEMPERATUREIGNITION TEMPERATUREIGNITION TEMPERATURE

It is the point at which an air/gas mixture will self-ignite.

All operations / instrumentation in this zone must operate without generating temperatures at or near the minimum ignition temperature.

Instruments are typically classified by a T Class rating


FLASH POINTFLASH POINTFLASH POINTFLASH POINT

Is the temperature at which volatile liquids give off ignitable fumes, or gasses.

Instruments operating at temperatures above the flash point of substances present in the process must be intrinsically safe.


EUROPEAN AREA CLASSIFICATIONEUROPEAN AREA CLASSIFICATIONEUROPEAN AREA CLASSIFICATIONEUROPEAN AREA CLASSIFICATION Zones are generally used in Europe:

Zone 0: Flammable gasses are present continuously or for long periods. (Typically more than 1,000 hours per year.)

Zone 1: Gasses are likely to occur in normal operation. (Typically between 10 and 1,000 hours per Year.)

Zone 2: Gasses unlikely to occur and will occur only for short periods. (Typically between 0.1 and 10 hours per year.)


EUROPEAN AREA CLASSIFICATIONEUROPEAN AREA CLASSIFICATIONEUROPEAN AREA CLASSIFICATIONEUROPEAN AREA CLASSIFICATION European standard EN 50.014 requires that all instrumentation be subdivided into two groups:

Group I: To be used in mines; presence of methane and coal dust.

Group II: To be used in surface industries; presence of gasses or vapors

(Class 1). In Group II, a letter designation is appended indicating the level of ignition energy,

A - being the lowest (propane), B - higher (ethylene), and C - the highest (hydrogen, acetylene).


NORTH AMMERICAN AREA NORTH AMMERICAN AREA CLASSIFICATIONCLASSIFICATION


Divisions are generally used in North America

Division 1 : Dangers can be present during normal functioning.(>10 Hrs/day)

Division 2 : Dangers can only be present during abnormal functioning.(between 0.1 to 10 Hrs/day)




Further divisions are subdivided into

Class 1 : Gases and vapours are grouped by the level of ignition energy

D - being the lowest (propane), C - higher (ethylene), and

A&B - the highest (hydrogen, acetylene).

Class II : Dusts are grouped by the level of ignition energy.

G - being the lowest (Grain dust), F - higher (Coal dust), and E - the highest (metal dust).

Class III : Fibres are not sub-grouped


DIFF. BETWEEN NA & ESDIFF. BETWEEN NA & ESDIFF. BETWEEN NA & ESDIFF. BETWEEN NA & ES

Zone 2 and Division 2 are almost equivalent.

While Division 1 includes the corresponding Zones 0 and 1. An instrument designed for Zone 1, however, cannot be directly used in Division 1.

In Europe, instruments are certified on the basis of design and construction.

In North America, they are classified on the basis of the zone of possible installation.


AREA CLASSIFICATIONAREA CLASSIFICATIONAREA CLASSIFICATIONAREA CLASSIFICATION


GAS GROUP CLASSIFICATIONGAS GROUP CLASSIFICATIONGAS GROUP CLASSIFICATIONGAS GROUP CLASSIFICATION


GROUP CLASSIFICATIONGROUP CLASSIFICATIONGROUP CLASSIFICATIONGROUP CLASSIFICATION


TEMPERATURE CLASSIFICATIONTEMPERATURE CLASSIFICATIONTEMPERATURE CLASSIFICATIONTEMPERATURE CLASSIFICATION


TESTING AUTHORITIESTESTING AUTHORITIESTESTING AUTHORITIESTESTING AUTHORITIES


NON-INCENDIVE AND ISNON-INCENDIVE AND ISNON-INCENDIVE AND ISNON-INCENDIVE AND IS Both are constructed to protect during exposure to hazardous gases.

Non-incendive is designed for safe use in areas that may be hazardous under abnormal conditions. (Zone 1 Div 2)

Low incidence of the hazard in this zone makes it unlikely that failure will occur while explosive gases are present.

Intrinsically safety is required where areas have a hazardous atmosphere intermittently or continuously. (Class 1 div1)


METHODS OF PROTECTIONMETHODS OF PROTECTIONMETHODS OF PROTECTIONMETHODS OF PROTECTION Explosion containment (Ex "d") allows the explosion to occur.

but confines it in a well-defined place, avoiding propagation to the surrounding atmosphere.

Explosion-proof enclosures are part of this method.

Segregation attempts to physically separate or isolate electrical parts or hot surfaces from the explosive mixture.

Pressurization (Ex "p") and encapsulation (Ex "m") techniques are used in this method. Other related methods worth noting are oil immersion (Ex "o"), powder filling (Ex "q"), and extra heavy-duty design electrical apparatus (Ex "e").

Prevention limits thermic and electric energy to within safe levels.

Nonincendive approval (Ex ÒnÓ) assures that under normal operating conditions no explosion will occur.

Intrinsic safety approval (Ex ÒiaÓ and ÒibÓ) assures that no explosion will occur even if faults in the electronic circuitry occur.


ELECTRONIC IS CIRCUITRYELECTRONIC IS CIRCUITRYELECTRONIC IS CIRCUITRYELECTRONIC IS CIRCUITRY According to CENELEC EN 50.020 no spark or

thermal effect, generated during normal functioning

and/or

Specific fault condition, is able to ignite a given explosive atmosphere.

All parts of a circuit that are able to store energy (inductance and capacitance to operate switches) must release energy that is only lower than the minimum ignition energy of the explosive mixture present in the hazardous location.


DIFFERENCE IN ia & ibDIFFERENCE IN ia & ibDIFFERENCE IN ia & ibDIFFERENCE IN ia & ib

Under European standards, an instrument of category "ia" should not be able to ignite a dangerous air/gas mixture during normal functioning, in the presence of a single fault, or in the presence of any combination of two faults.

An instrument of category “ib”should not be able to ignite such a mixture during normal functioning, or in presence of a single fault.

Caterory “ia” guarantees the safety with two faults whereas the category “ib”guarantees the safety with only one fault.


THERMOGRAPHY


Infrared ThermographyInfrared Thermography

Non-contact temperature measurement technique

Requires no interruption of production - You don’t have to sacrifice productivity to gain productivity

Safe monitoring distance

Detects potential faults


Where is thermal imaging used?Where is thermal imaging used?

Electrical inspection

Mechanical inspection

Refractory/insulation inspection

Steam related inspection


Some typical faults detectedSome typical faults detected

Overheating component provides an early warning of impending component failure

Excessive heat loss signifies inadequate thermal insulation


Electrical Inspection-Electrical Inspection-phase systemsphase systems

Small change in current flow results in considerable heating difference.

Overheating appears as a constant temperature along the length of the conductor


Electrical Inspection aElectrical Inspection acceptable heating levelscceptable heating levels

Companies specify their own levels

Typically three or four levels

Most critical requires immediate replacement of a faulty component

Least critical requires monitoring and re-inspection at next survey


Inside Electrical Fuse Box


Mechanical InspectionMechanical Inspection

Usually involves rotating equipment

Excessive heat generated from friction caused by faulty bearings, inadequate lubrication, misalignment, misuse and normal wear


Mechanical Inspection-Mechanical Inspection-Typical componentsTypical components

Gears Shafts Couplings V-belts Pulleys Chain Drive Systems Conveyors Air Compressors Vacuum pumps Clutches


IR Application - motor and Jaw CouplingIR Application - motor and Jaw Coupling

0Misalignment

105° F

62° F

1,000/inch outAngular

30,000 out Parallel10,000/inch out angular


Bearings Before Lubrication


Bearings After Lubrication


IR Application – Furnace applicationsIR Application – Furnace applications


Refractory/Insulation InspectionRefractory/Insulation InspectionTypical componentsTypical components

Batch and continuous furnaces

Heat treatment furnaces Ovens Dryers Kilns Boilers Ladles Hot storage tanks Insulated pipes


Steam Related InspectionSteam Related InspectionSteam line leaks and insulation defectsSteam line leaks and insulation defects

Above the ground steam lines scanned as operator walks underneath

Underground inspections more problematic due to the density of the surface material


Roof Inspection Moisture


1840:

William and John Herscheldiscovered Infrared spectrum

Looking BackLooking Back


1960:

1st ‘real time’ imager. 10 minutes per scan! 85 pounds Nitrogen-cooled Limited use



1973:

25 pounds Battery-operated No temperature measurement



1978:

Temperature measurement Recording capability 8 more pounds



1986:

Thermoelectrically-cooled Increased portability



1990:

Self contained unit incorporating recording, temperature calibration, data collection and storage.

Even greater portability



Focal Plane Array Technology

Hand-held Higher resolution Light weight Intuitive features

TodayToday


Third Parties Supply the SystemThird Parties Supply the SystemThird Parties Supply the SystemThird Parties Supply the System

Emonitor Odyssey imports the bit maps Using Active ‘X’ the embedded thermographic software is

accessed through Emonitor Odyssey From Odyssey a double click on the thermographic image and you

are ‘live’ All windows based systems are suitable


EMONITOR Odyssey - Thermo graphic DataEMONITOR Odyssey - Thermo graphic Data


Emonitor odyssey information the way you want Emonitor odyssey information the way you want Emonitor odyssey information the way you want Emonitor odyssey information the way you want


ANY QUESTIONSANY QUESTIONSANY QUESTIONSANY QUESTIONS

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