THE “B” BOOK GUIDE TO VIBRATION …balmacinc.com/downloads/BBookVibration.pdfThe “B” Book Guide To Vibration Measurements Why Use Vibration Measurements? Vibration measurement

THE “B” BOOK GUIDETO VIBRATION MEASUREMENTS

HOW TO MEASURE MACHINE VIBRATIONWITH A VIBRATION METER

Page 2 “B” Book Guide To Vibration Measurement

Fig 1 - Balmac Digital VibrationMeter with 100 mV/g Accelerometer

Fig 2 - Balmac hand-held pocket sizevibration meter

The “B” Book GuideTo Vibration Measurements

Why Use Vibration Measurements?

Vibration measurement is an effective method forlooking at the condition, or “health”, of rotatingmachinery in commercial and industrial applications. Periodically checking machine conditions (known as“trending”) is easy to do with vibration meters.

Vibration meters help operators spot deterioratingmachine conditions before they become critical. Byidentifying and quantifying a vibration problem,corrective action can be taken before the problembecomes significant and expensive.

Trending with vibration meters allows maintenancetechnicians to plan repairs during normal work hoursrather than scheduling costly overtime or even shuttingdown production or an entire HVAC system.

Practical Uses for Vibration Measurements

Pinpoint Vibration ProblemsIdentify Mechanical LoosenessDetect Bearing WearSpot Bent ShaftsCondition MonitoringPredictive and Preventive MaintenanceTroubleshoot MachineryQuality Control

Applications for Vibration Measurements

BearingsBlowersCentrifugesCompressorsConveyorsCooling TowersFansGrindersHVAC SystemsMixersMotorsPumpsSpindles

Page 3 “B” Book Guide To Vibration Measurement

Fig 3 - Attach cable to meter andtransducer then attach magnet or probetip.

Fig 4 - Magnetic Clamp and Probe Tip.

WARNINGExercise extreme caution when performing any taskaround rotating machines. Failure to do so may resultin equipment damage and personal injury. Operatorsare encouraged to become familiar with the equipmentand operating procedures before attempting vibrationanalysis.

How To Use a Vibration Meter

Step 1: Attach the Standard Accessories

Typical Vibration Meters have standard accessoriesthat are included with the Meter. They include: avibration Transducer or Accelerometer (often called theSensor), a connecting cable (Pickup Cable) , aMagnetic Clamp (for securely attaching the transduceror accelerometer to the surface of the application beingmeasured) and a Vibration Probe Tip (sometimescalled a “Stinger.”)

Attach one end of the Pickup Cable to the Meter andthe other end to the transducer (or accelerometer). One connector matches the transducer and onematches the connector on the meter.

Select either the Magnetic Clamp Base or Probe Tip.The advantages of each are discussed below. Bothaccessories have a 1/4- 20 or 1/4-28 studs and attachto the mounting holes in the base of the transducer oraccelerometer.

Magnetic Clamp (Recommended) or Probe Tip

The Magnetic Clamp Base is recommended to providea secure, stable mounting for the transducer. Themagnet has a 12 lb pull, but allows an operator todetach it without difficulty. Vibration readings areaffected by the stability of the transducer mounting.

The 7" Probe Tip is typically used in hard-to-reachareas. It is convenient for operators to use on vibrationpoints on machines because it is not as bulky as amagnet. However, some practice is required toachieve consistent, repeatable readings.

Page 4 “B” Book Guide To Vibration Measurement

Fig 3 - Modes are DISP,VEL and ACC.

Fig 4 - VEL selected.

Fig 5 - DISP selected.

Fig 6 - ACC selected.

Step 2 - Select a Mode

The Mode is a vibrationparameter you want tomeasure. Balmac VibrationMeters have three modes:Displacement = DISP,Velocity = VEL andAcceleration = ACC.

Velocity

Velocity is read in inches persecond (Peak). Velocitymeasures the rate of changeof displacement. Velocity ismore proportional to thedestructive forces generatedin a machine than eitherdisplacement or acceleration. Velocity readings reveal moreabout vibration at allmachinery speeds (RPMs).

Displacement

Displacement measures thedistance the part moves read inMils (one Mil = .001 inch)(Peak to Peak). It is necessaryto know the RPM of theequipment to establish avibration limit in Displacement(Mils).

Acceleration

Acceleration is the rate ofchange of velocity read in g’s(Peak). G’s are useful whenmeasuring very high frequencyvibrations such as signalsgenerated in rolling elementbearings or gear trains.

Step 3 - Select a Range

Ranges on Balmac meters are:

200 20 2 Very Low Range

200 (very rough vibration)

Most applications will neverbe this rough. Used withextremely large primarymovers (Class 4) type ofequipment.

Max Min199.9 19.0

20 (moderate vibration)

Recommended starting rangefor most measurements. Goto 2 for smaller vibrationlevels.

Max Min19.99 1.9

2 (smooth to moderatevibration)

Use for small vibration levelsand for QC levels for motorsand fans.

Max Min1.999 0.01

Very Low Range

Multiply reading on display by number on label thatcorresponds to Mode used.

Example: Mode is Velocity Model = Vel. Displayreading = 197.6. Answer: 197.6 x .001 = .19 in/sec.

Page 5 “B” Book Guide To Vibration Measurement

Fig 12 - Vertical, Axialand Horizontaldirections.

Fig 13 - Typical measurementpoints on a blower.

Fig 14 - Typical Vibration Severity Chart

Step 4 - EXAMPLE: Taking a Measurement inVelocity

1. Complete Step 1. Attach Magnetic Clamp (or ProbeTip) to Transducer. Connect Transducer to propercable end and then connect the other cable end to theMeter.

2. Complete Step 2. Select Velocity Mode.

3. Complete Step 3. Select 20 Range.

4. Secure Magnetic Clamp/Transducer assembly tofirst measurement point. (See Vibration Directions andMeasurement Points later in this brochure)

5. Depress OFF/ON button until it latches. (Power ON -Display comes on)

6. Depress VEL button until it latches. (Mode =Velocity)

7. Depress 20 button until it latches. (Range = 20)

8. Allow readings to stabilize. (Do not be concerned ifthe digits to the far right of the display vary up or down,this is normal operation.)

9. Record reading.

Step 5 - What Direction to Measure?

Vibration is measured inVertical, Horizontal andAxial directions. Test allthree to find the direction ofthe strongest signal. Typically, the Horizontal(Radial) direction providesthe strongest signal.

Machine mountings caninfluence readings. Springisolator mounted machinesmay have strong verticalreadings.

Strong axial readings oftenindicate a bent shaft orloose bearings. Takemeasurements in all threedirections wheneverpossible.

Step 6 - Where To Measure Vibration?

Vibration signals arestrongest at or nearbearings. They tend toweaken as you movefarther away frombearings. Example:the vibration signal isstrongest on a directdrive motor/fanassembly on thebearing closest to thefan.

CAUTION: Extremecare must be taken when working around rotatingmachinery belts, pulleys, sheaves and shafts.

Step 7 - What Does the Reading Mean?

Refer to the Vibration Severity Chart .

Example: an operator has set the Vibration Meter toVelocity (VEL) on the 20 Range and has measured thevibration level on a bearing in the Horizontal direction.

The reading is: 00.15 (Inches Per Second, Peak):

The operator would record the reading and thencompare the recorded reading with the Severity Chart todetermine the vibration severity.

Page 6 “B” Book Guide To Vibration Measurement

Fig 16 - Displacement readings run across the top anddown the right side of the Severity Chart. Accelerationis shown in lines running diagonally left to right.

Fig 18 - Over Range

Looking at the left side of the Severity Chart (see Fig16), the operator would see these numbersrepresenting Velocity in inches per second.

The operator’s reading of 00.15 would fall exactly halfway between .1 and .2 and the operator could concludethe vibration level was in the GOOD zone on the chart.

00.15 ips = GOOD

Measuring vibration in Velocity is the easiest method tolearn machine condition. Velocity readings do notrequire knowing the RPM of the machine. A reading of.1 is SMOOTH whether the machine is running at 100RPMs, or 100,000 RPMs.

Other Examples of readings in Velocity:

0.08 ips = SMOOTH

0.4 ips = ROUGH.

Displacement Measurements (Mils Peak-to-Peak)

Displacement (Mils) readings run across the top anddown the right side of the chart. (See Fig 16) Matchyour reading with the same number at the top or righthand column on the chart.

Next to that number is a diagonal line running right toleft down to the bottom of the chart.

Follow the diagonal line down until it crosses a verticalline coming up from the bottom that corresponds tomachine RPM. (RPM is at the bottom of the chart.)

Determine if this reading falls in the SMOOTH, GOOD,FAIR or ROUGH range.

Example: a reading of .5 mils (top right corner of chart)intersecting at 2000 RPM (middle bottom of chart) is inthe SMOOTH range. A reading of 3 mils (top middle ofchart) at 2000 RPM is ROUGH.

Displacement readings require knowing the machinerunning speed (RPM).

Acceleration Measurements (g’s, Peak):

Acceleration readings are represented by diagonal linesrunning from the top left to the bottom right of the chart. Acceleration numbers are found in the middle of theselines. Like Displacement readings, Accelerationreadings require knowing the machine RPM.

Example: .1 g at 1000 RPM = ROUGH.

0.1 g at 10,000 RPM = SMOOTH.

Over Range

Vibration signal strength to strong for setting. If displayshows a 1. (see photo), select next higher range.

Page 7 “B” Book Guide To Vibration Measurement

Fig 20 - Sample VibrationRecord

Fig 21 - Vice Grips

Fig 22 - Shaft Stick

Vibration Maintenance Records

Recorded vibration levels:

provide machine history

trend machine conditions

help schedule maintenance

Recording intervals vary from machine to machine. Age and machine condition are important factors, but ageneral rule of thumb is readings should be made morefrequently as soon as machinery deterioration isnoticed.

Vibration Maintenance Records Samples may bedownloaded from the Balmac Inc. website.

Directions:

1. Sketch basic machine configuration in upperleft grid.

2. Record operator identification, dates, times,etc.

3. Include critical machine information such astype of equipment, RPM and special notes.

4. Record vibration readings in HORIZONTAL,VERTICAL and AXIAL directions in appropriatecolumns. Record both VELOCITY andDISPLACEMENT readings.

Vice Grip Pliers

The Model 158 Pickups maybe attached to Vice GripPliers for non-magneticsurfaces.

Fish Tail Shaft Sticks

The Fishtail Shaft is used tomeasure vibration onrotating shafts.

Headphones

Headphones are useful for listening top machineryvibrations. With experience, an operator can learn toidentify vibration sources by listening to the pitch andintensity of the vibration noise. This can be useful whenanalyzing defective bearings. Headphones may beused with Model 200, 205 and 211 Vibration Meters.

WARNINGRotating machinery have potentially dangerous movingparts. Potential hazards to the operator or thesurrounding area may exist. Operators should useextreme caution when working around moving parts.

DISCLAIMER

Balmac Inc. assumes no responsibility for errors oromissions nor assumes any liability for any damagesthat may result from use of its products or theinformation provided by Balmac Inc.

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