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Entry type: FAQ Entry ID: 38716895, Entry date: 10/02/2009
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Vibration severities and influenceable variables

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QUESTION:

 

 

 

 

 

How is vibration severity described and what are the influencing variables?


ANSWER / REMEDY / NOTES:

  

 

 

 

 

The vibration severity classifies the measured effective value of the vibration velocity.

Installation and test conditions for rotating machines measured in the manufacturing plant are standardized in DIN EN 60034-14.

This standard only applies to machines which are tested alone (without the driven machine, no-load operation) and in the case of free suspension or rigid clamping.

     
   

The purpose of this standard is to present the vibration response of the machine alone under defined conditions, therefore in a reproducible and comparable manner.

The limit values for vibration severity are also standardized and vibration severity level A (normal) applies with any special agreements.

     
   

Vibration

severity

level

Shaft height

H in mm

56 ≤ H ≤ 132

132 ≤ H ≤ 280

H > 280

Machine

installation

Seff

m

Veff

mm/s

aeff

m/s2

Seff

m

Veff

mm/s

aeff

m/s2

Seff

m

Veff

mm/s

aeff

m/s2

A

Free

suspension

25

1,6

2,5

35

2,2

3,5

45

2,8

4,4

A

Rigid

clamping

21

1,3

2,0

29

1,8

2,8

37

2,3

3,6

B

Free

suspension

11

0,7

1,1

18

1,1

1,7

29

1,8

2,8

B

Rigid

clamping

-

-

-

14

0,9

1,4

24

1,5

2,4

     
   

Limit values (effective values) of the max. vibration severity for vibration
displacement (s), vibration velocity (v) and acceleration (a) for the shaft height H

(Excerpt from DIN EN 60034-14)

     
   

The vibration severity is significantly influenced by the balance quality, however, other influencing variables also affect the vibration severity, such as elastic properties of the bearing and of the machine components it is carrying as well as electromagnetic excitations.

There is no direct connection between vibration severity and balance quality.

The vibration severity of a motor alone does generally not provide any information on the vibration response of the entire drive unit at the installation site (vibration assessment at the installation site in accordance with DIN ISO 10816-3). Please also refer to the subsequent FAQs. If impermissibly high levels of vibrations are detected here, experience has shown that close cooperation between the motor manufacturer, machine manufacturer and operator can pinpoint the cause.

     
    Frequent causes of system vibrations of this kind are:
  • incorrectly balanced transmission elements
  • inaccurate alignment
  • resonances of a torsionally soft base frame
  • Distortion of the motor in the foundation fixing
  • Excitations from the driven machine / gearbox
    Experience has shown that steel building constructions are particularly susceptible to system vibrations, as they only tend to be dimensioned after static loads without dynamic aspects being taken into consideration.

 

 

 

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