Vibration Analysis for Rotating Machine

7/26/2019 Vibration Analysis for Rotating Machine

1/46

Vibration monitoring and analysisfor rotating machine

Introduction to mechanical vibration


2/46

Outline

Introduction

Vibration monitoring and analysis

Vibration : Measurement

Data Acquisition

Types of transducer

Mounting method

FFT analysis

Example

Unbalance

Misalignment

Spur gear

Centrifugal pump


3/46

Introduction

Static equipment Ex. Pressure vessel, Tank

Rotating equipment Pump, Compressor, turbine


4/46


Raw Data

Time domain

Analysis data

Frequency domain

FFT analyzer

Sensor


5/46

Vibration : MeasurementAmplitude Units

Displacement, D Micrometer peak to peak

Velocity, V mm/s - peak or rms

Acceleration, A mm/s2- peak or rms


6/46

Types of transducer

Proximity Probe Seismic Velocity

ProbeAcceleration Probe

Relative displacement Velocity Acceleration

01,500 Hz 81,500 Hz 120,000 Hz


7/46

Mounting method

Method Frequency

limit (Hz)

Hand held 500

Magnet 2,000

Adhesive2,500

4,000

Bees wax 5,000

Stud6,000

10,000


8/46

FFT analysis

Fast fourier

transform (FFT)


9/46


Raw Data

Time domain

Analysis data

Frequency domain

FFT analyzer

Sensor


10/46

Example

Unbalance

Misalignment

Spur gear

Centrifugal pump


11/46

Type of unbalance1. Static unbalance2. Couple unbalance3. Dynamic unbalance


12/46

12

Static Unbalances

Corrected

balance weight in one plane at rotor centre of gravity (CG).


13/46

Couple Unbalances

180

Corrected

balancerequires correction in two planes at 180.


14/46

Dynamics Unbalances

static couple Staticunbalance Couple


15/46

Special case of Dynamics Unbalances

Corrected

Overhung rotors often have both static and couple unbalance eachof which may require correction.

Overhung Rotor Unbalance


16/46

Balancing

cooling tower


17/46

Cooling Tower

1. (transducer) (Tachoprobe)

2. 1- (Magnitude :mm/sec)- (phase angle)

3. (trial weight) Rotor

4. 2- (Magnitude :mm/sec)- (phase angle)

5. Polar graph


18/46

(Trail weight) Wt = 30 x Wr/ r

Wr Static weight : gr (radius of trial weight : mm)

(correct weight) Vc= Vox Wt/Vt

Vo Unbalance : mm/secVt : mm/sec

Reference by : Machinery vibration & Balancing /Victor Wowk.


19/46

spectrum cooling #4 1X rpm Amplitude Unbalancing

Frequency : 355.3

Amplitude: 4.379Phase : 84 degree

()


20/46

Vector correct & angle phaseon Polar graph

Data: 1.Rotor & Fan weight : 26 kg ,(4x32 kg)

2. Radius of trial : 220 mm.

Vector unbalance Vo: 4.379 mm/sec

Phase Vo: 84 degree.

Trial weight : 25 g (21 g)

Vector unbalance +weight V1: 7.4 mm/sec

Phase V1: 215 degree.

Vector from trial weight Vt: 10.8 mm/sec

Phase : 329 degree. (Vt-Vc)


21/46

Position of point to correct (Balancing)

Trial weight : 25 g (21 g)

Phase : 84 degree.

Correct weight ,Mc : 10.1 g

Correct phase : 31 degree.

Before..

After..


22/46

Amplitude: 1.684 mm/sec

4.375

()


23/46

Misalignment


24/46

MisalignmentIntroductio

n

What is it? Misalignment is a conditionwhere the centerlines of

coupled shafts do notcoincide.


25/46

EX.

Introductio

nMisalignment


26/46

Introductio

n

Bearing, Coupling, Seal and Shaft failure

Lost time to repair machine

Lost opportunity to run process

Lost Maintenance Cost

Misalignment


27/46

Type of

misalignmen

tMisalignment


28/46

Detection

methodMisalignment


29/46

Introductio

nMisalignment


30/46

MisalignmentDetection

method

Time- Frequency Domain

Fast fourier

transform (FFT)


31/46

Type of

misalignmen

tMisalignment


32/46

Type of

misalignmen

tMisalignment

Shear force

Bending moment

2X component will

be higher than 1X.

Depend on thecoupling type

Axial 1X and 2Xlevels will be low

Symptoms: 2X radial, smaller 1X

radial


33/46

Type of

misalignmen

tMisalignment

Bending moment

Also be fairly

strong radial

1X and 2X levels

Symptoms: High axialvibration: 1X

strong (but 2X and 3X can also be

strong)


34/46

Type of

misalignmen

tMisalignment

Can be 3X, 4X all the

way up to 8X peaks

The noise floor is

not raised(unlike

rotating looseness)

Frequency: 1X and 2X (and 3X and

4X) axial and radial


35/46

Spur Gear

Failure Mode :Backlash, Tooth wear and Broken teeth etc.


36/46

Normal


37/46

Backlash

Normal


38/46

Tooth wear

Normal


39/46

Tooth load

Normal


40/46

Broken Tooth

Normal


41/46

Broken Tooth

Normal


42/46

Vibration in centrifugal pump


43/46

Loosen components


44/46

Gap between blade vanes and case is too small

-the BPF will increase


45/46

Turbulence flow

-random amplitude

at low frequency


46/46

Cavitation

-random amplitude

at high frequency

Documents

Vibration Analysis for Rotating Machine