ROTATING MACHINERY HAVING RIGID ROTORS

 

 

Table 1-Vibration Severity Criteria  

Recommended for General Machinery Turning from 600 to 12000 RPM

(Based on ISO IS 2372)

 

 RMS Overall  velocity Level Measured

in 1000 Hz Bandwidth

                      Vibration Severity Criteria

 

Mm/s

In/s

Class I

Class II

Class III

Class IV

0.28

0.01

Good

 

Good

 

Good

 

Good

0.45

0.02

0.71

0.03

1.12

0.04

Satisfactory

1.8

0.07

Satisfactory

2.8

0.11

Unsatisfactory

Satisfactory

4.5

0.18

Unsatisfactory

Satisfactory

7.1

0.28

Unacceptable

 Unsatisfactory

11.2

0.44

 

Unacceptable

 Unsatisfactory

18

0.71

 

 Unacceptable

28

1.10

 Unacceptable

45

1.77

 

Class I.   Small-sized machines (powered from 0 to 15 KW)

Class II.  Medium-sized machines (powered from 15 to 75 KW)

Class III. Large-sized machines (powered > 75 KW) mounted on "Rigid Support" structures and foundations

Class IV. Large-sized machines (powered >75 KW) mounted on "Flexible Support" structures

 

Note:

Support is determined as  rigid support  if the fundamental frequency of the machine installed on the support is higher than the machine  main excitation frequency

Support is determined as flexible support  if the fundamental frequency of the machine installed on the support is lower than the machine  main excitation frequency

 

 

 

Table 2-Vibration Severity Criteria

Recommended for Slow Speed Large Machinery Turning from 600 to 1200 RPM

(Based on ISO IS 3945)

 

RMS Overall  Velocity Level Measured

in 1000 Hz Bandwidth

Support Classification

Mm/s

In/sec

Rigid Supports

Flexible Supports

0.46

0.018

Good

 

 

Good

0.71

0.028

1.12

0.044

1.80

0.071

2.80

0.110

Satisfactory

4.60

0.180

 Satisfactory

7.10

0.280

Unsatisfactory

11.2

0.440

 Unsatisfactory

18.0

0.710

Unacceptable

28.0

1.100

 

Unacceptable

46.0

1.800

71.0

2.800

 

 

 

 

ELECTRIC MOTOR

 

 

Table 3-Recommended Vibration Limits for Electric Motors

(Based on ISO IS 2373)

 

Motor Grade RPM RMS Velocity amplitude for the following shaft heights, in mm
80 < h < 132 132 < h < 225 225 < h < 400
mm/s in/s mm/s in/s mm/s in/s
Normal 600 - 3600 1.80 0.071 2.8 0.110 4.5 0.177
Reduced 600 - 1800 0.71 0.028 1.12 0.044 1.8 0.071
1801 - 3600 1.12 0.044 1.80 0.071 2.8 0.110
Special 600 - 1800 0.45 0.018 0.71 0.028 1.12 0.044
1801 - 3600 0.71 0.028 1.12 0.044 1.8 0.071

 

Note:

- RMS velocity amplitude is measured in the frequency range from 10 to 1000 Hz.

- The shaft height is the vertical distance from the base of the motor to the centerline of the shaft

 

 

 

                                         Table 4-Permissible Vibration for Large Induction Motors

                                                         (Based on NEMA MG 1-20.52)

 

RPM Displacement amplitude (peak to peak), in inch
3000 - 4000 0.001
1500 - 2999 0.0015
1000 - 1499 0.002
999 and below 0.0025

Motor vibration measurements should be carried out in the condition of motor no-load operation, at rated voltage and nominal frequency (AC motor), nominal speed(s), and motor operational temperature.

To determine vibration severity criteria for specific machineries or motor applications, please contact Vibratechnica at support@vibratechnica.com for support