UNIDAD II

ANALISIS VIBRACIONAL

APLICACIONES EN MÁQUINAS

Espectro de Máquina

v [mm/s]

fn f

(Hz)

1. DESBALANCE

Fundamental Frecuency fn =Evaluation criteria:ISO 10816-3 ISO 1940

n (rev/min) 60

n

2. DESALINEAMIENTO

Machine spectrum:

v [mm/s]

Fn 2xFn f (Hz)

Axial :mainly Angular

Misalignment

radial :Mainly Offset

fz 2xfz 3xfz 4xfz f en Hz

Espectroa enmm/s²

fn2

z1

z2

fn1

Harmonics of fz visibleSide bands with fn

Frecuencia en Mecanismos de Engrane fz =fn1*z1

fz =fn2*z2

z1, z2: número de dientesfn1: Frecuencia Rotacional de la Rueda Conductora

3.Fallas de Frecuencia de Engrane

Side bands with fn

Side band distance fn is the

fundamental frequency of the defective gear (broken tooth)

Many side bands around fz,

gear mesh with slowly decreased amplitudes

z2

fn1

fn2

z1

Fz 2xfz 3xfz f en Hz

Espectro:a enmm/s²

4. Fisura/Rotura de Engranaje

5.Cimentación Mala

fn

fn 2xfn 3xfn 4xfn usw. f en Hz

Espectro de Maquina:v enmm/s

Harmonics of fn are visible

- fundamental freq. fn =

-Root Cause: Resonance or Instability

RPM[Rev/min] 60

s = 9

Espectro de Máquina

x=3(eg. fixture for bearing)

fn

Fn fBPF x fBPF f en Hz

v enmm/s

6.Turbulencia

Blade pass frequency fBPF high

amplitude

- blade pass frequency: fBPXF = fn s

- higher orders xfBPF = fn s x

- s:number of blades

- x:number of disturbance locations

fn

v enmm/s

a) Espectro de Máquina

fn 2xfn 3xfn 4xfn 5xfn f en Hz

7. Resonancia

Resonance step-up

Phase shift of 180°

b) Bode diagram

v enmm/s

nRes n

en °

nRes n

c) Diagrama de Cascada para diferentes RPM

Resonance step-up

v en mm/s

n en Rev/min

Frecuencia Natural f en Hz

fn 2xfn 3xfn

fn

8. Rotor en Rozamiento

v enmm/s

fn 2xfn 3xfn etc. f en Hz

Espectro de Máquina

many Harmonics of fn up to high orders

(10 times ... 20 times)

a enm/s²

t en ms

T

1 Revolución

Acceleration Time Signal

1 shock pulse per Revolution in the time domain of the acceleration signal

Period length T =

1 fn

Campo Magnético Asimétrico en el Estator (Motor Eléctrico)

fn

fNetz

fn 2xfL f en Hz (49,85 Hz) (100 Hz)

v enmm/s

Espectro de Máquina

2-times fL visible

-Line frequency fL = 50,0 Hz

- Exception: Frequency converter Drives

Shorted LaminationsRotor eccentricityasymmetric power feedasymmetric winding

v enmm/s

99,0 2xfn 2xfL 101,0 f en Hz (100 Hz)

Zoom Espectro de Máquina:

No side bands around 2xfL

2-pole machines:

2-times fundamental freq. fn

slightly below 2 fL !

fn 2xfL f en Hz (49,85 Hz) (100 Hz)

v enmm/s

Espectro de Máquina

2-times fL visible

-Line frequency fL = 50,0 Hz

- Exception: Frequency converter Drives

fline

nbar

fn

Armature field fault (Rotor Electric machines):

Bar breakage Bar fracture Bar looseness

Bar passing frequencies fBar with side

bands visible at 2 fL intervals

Bar passing frequency fBar = fn nBar

With: nBar = number of armature bars

fL = 50,0 Hz - Line frequency

fn = fundamental frequency

fn 2xfLfBar f en Hz

v enmm/s Espectro de Máquina

99,0 2xfL 101,0 f en Hz (100 Hz)

v enmm/s

Espectro de Máquina

Armature field fault (Rotor Electric machines):

Sidebands visible around 2 fL at

fslip intervals

with slip frequency fslip = - fn

with p = number of stator poles

2 fL

p

Machine vibrationdisplacementvelocity

R.bearing condition:Shock pulse valuedBm-value,dBc-valueacceleration

Cavitation:Shock pulse value dBcav-valueacceleration

Measurement locations - vibration measurement