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Siemens AG
Entry type: FAQ Entry ID: 34388051, Entry date: 02/05/2009
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Mechanical distortion after installation - "soft foot"

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QUESTION:

 

 

 

 

 

What is soft foot and how is it possible to find out if it exists?


ANSWER / REMEDY / NOTES:

  

 

 

 

 

If motors are installed in such a way that they are subjected to mechanically distorting forces, increased vibration or noise can be the consequence. The most common cause of distorted motor housings is the so-called "soft foot" problem.

 

 

 
   
     
   

There is an easy way to detect housing distortion due to soft foot:

This is done by loosening the bolted connections of the four motor feet one after the other, one foot at a time. After loosening a foot while leaving the other three feet firmly tightened, the procedure is as follows and must be repeated for each foot:

A dial indicator is attached to the motor foot. If changes in the vertical position of the motor foot are indicated when the bolted connection is loosened, the motor housing is distorted due to soft foot.

If soft foot is detected when the motor is being aligned, it must be corrected by inserting or removing shims under the feet.

In the case of angular soft foot, step shims may be necessary. Unless indicated otherwise by the manufacturer, the amount of soft foot should not be more than 0.05 mm.

     

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