Mechanical Vibration p.1
ANDERSON ANDRADE TRIGO - TEL./FAX: (16)39422003 - CELULAR (16) 97965130 - E-MAIL:[email protected]
Vibrações
Mecânicas
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4-vibração mecanicas, Notas de estudo de Eletromecânica
-vibração mecanicas
Tipologia: Notas de estudo
2011
1 / 11
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Vibrações
Mecânicas
1. Rotational frequency
of the fan
2. Rotational frequency
of the motor
3. Misalignment of the
shaft at the coupling
4. Toothmeshing
frequency
5. A developing fault in
the ball-bearing
Fault Detection and Diagnosis
Types of Vibrations of a Machine
Rotor
Fundation
Bearing Pedestals
Absolute
Bearing Vibrations
Relative
Shaft Vibration
Absolute
Shaft Vibrations
Force Mobility Vibration
RPM
Forces * Mobility = Vibration
Brüel & Kjær
Enter
Prev^ Measure
F1 NextF2^ F3F4F
E^ Check On/Off^ Del
D D
Vibrations may be different from point to point Collector Data Collector Type 2526^ Brüel & Kjær K B 7/6-' Enter Previous Measure F5 (^) F4 F3 (^) NextF2 (^) F 36 9 25847
- (^) E Check. Del 01 On/Off Collector Data Collector Brüel & Kjær Type 2526 K B 7/6-' Enter Previous (^) Measure F5 (^) F4 F3 F2 Next (^) F 36 9 52847
- (^) E Check. 01 On/OffDel
Forces * Mobility = Vibration
RPM
Point 1
Point 2
Measurement time (^) Harmonic signals can be measured in short time (^) Random and Pulsed signals need longer time (^) For FFT spectra C = 1 pr. average. (^) With Digital Filtered CPB Adequate measurement time can be set up. B * T = C
B = Highest resolution of Analysis
T = The Shortest measurement time
C = Constant.
B * T = C
B = Highest resolution of Analysis
T = The Shortest measurement time
C = Constant.
Theoretical
C = 3 for Harmonic Signals
C = 30 For Random Signals
Theoretical
C = 3 for Harmonic Signals
C = 30 For Random Signals
In Practice
C = 5 for Harmonic Signals
C = 100 For Random Signals
In Practice
C = 5 for Harmonic Signals
C = 100 For Random Signals
Typical averaging time:
10 sec for 6%
5 sec for 23 %
20 sec. for slow running machines.
Typical averaging time:
10 sec for 6%
5 sec for 23 %
20 sec. for slow running machines.
Averaging f f f f n B = Bandwidth T = Time B*T > 1 t a BT 1 2
Summary (^) Vibration gives the earliest warning of faults in rotating machinery (^) Since the vibration value varies from point to point, each point should have individual reference. (^) Frequency analysis of vibration gives a good assessment of machinery vibration. (^) Each machinery component has its own Potential Failure Mode which can be detected by vibration. (^) Vibration signals can be a mixture of stationary, harmonic, modulated, random and impulsive signals. (^) Averaging is important for establishing good measurements.