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Entry type: FAQ Entry ID: 33389128, Entry date: 12/15/2008
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Setting up motors; mounting methods;vibration dampers

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QUESTION:

 

 

 

 

 

What do I need to take into account when setting up motors on the concrete foundation? What mounting methods can I use? What are vibration dampers?


ANSWER / REMEDY / NOTES:

  

 

 

 

 

As well as the weight forces, the foundation has to bear all the forces and torques generated when energy is transferred from the motor to the driven machine and pass these onto the subsurface. This also applies to any additional factors which may arise, such as axial thrust and vibrations. In view of this, the foundation must be appropriately designed and adequately dimensioned. The calculations for the foundation must be performed by a construction company, who shall also be responsible for actually realizing it. The type of subsurface chosen (e.g. rock, gravel, sand, marsh, or permafrost) can have a significant influence on the nature of the foundation.

Special care is required when planning steel-framed foundations which are capable of vibration. These are often used in the raw materials or chemicals industries or for harbor cranes.

DIN 4024 must be taken into account when designing the machine foundation as regards the natural frequencies of the foundation (natural frequencies of the foundation after installation of the machine set).

The foundation must be designed in such a way that vibrations cannot be transferred from adjacent units.

 

 

 
   

Notice!

  • Do not allow forces to "wander". Ensure they are channeled in a straight line to the foundation via the shortest route.

  • Watch out for vibrations generated by rotational frequency (where there is a lack of balance, for example), particularly where fast-running drive systems are involved.

  • The machines must be erected in such a way that cooling air can flow unimpeded to and from the motors

    A motor's torque and weight are supported by the foundation via the motor's housing and feet or flange. In view of this, the foundation's dimensions must be based on the maximum possible levels of torque. These are generally the transient torques generated when the machine is switched on. As these occur in the form of oscillating torques, both compression and tensile forces are generated at the mounting points. All mounting elements and the equipment used to anchor them to the foundation must be dimensioned for these forces, and for any additional forces created by the belt drive or other elements capable of transferring force. Steel base frames should be designed in such a way that these loads are unable to generate impermissible levels of deformation or resonance.
     
   

 

 

 

 

 

 

 

Tensile forces

 

 

Compression

    Foundation forces
     

 

Mounting element

Figure

Explanation

 

Concrete foundation

 

With rag bolts

1 Motor foot

2 Alignment plates

3 Concrete foundation

4 Concrete casting

5 Casting channel

6 Rag bolt DIN 529

7 Washer

8 Hexagon nut DIN 934

Insert the rag bolts in the foot holes with the auxiliary pro-tective cover centered in the foot hole. Place the motor on wedges (quite low, to allow shims to be slid underneath at a later time). Only finalize alignment after the concrete casting has set completely.

 

With foundation block

1 Motor foot

2 Alignment plates

3 Concrete foundation

4 Concrete casting

5 Casting channel

6 Foundation block

   DIN 799

7 Washer

8 Hexagon bolt DIN 943

Screw the foundation blocks to the motor feet, place the mo-tor on wedges (quite low, to allow shims to be slid under-neath at a later time). Only finalize alignment after the concrete casting has set completely.

 

On soleplates

1 Hexagon nut

2 Machine foot

3 Alignment plates

   (adjustment plates)

4 Soleplate

5 Alignment irons and

   plates

6 Concrete casting

7 Concrete

8 Armature plate

9 Hammer disk

10 Armature plate

11 Armature bushing

Supporting surface faced for motor feet! Use alignment plates for alignment. Secure larger motors with tapered pins!

 

Steel foundation

 

1 Motor foot

2 Alignment plates

3 Steel foundation

4 Washer

5 Hexagon bolt DIN 933

Supporting surface faced for motor feet! Use alignment plates for alignment. Secure larger motors with tapered pins!

 

Secure with

tapered pins

1 Tapered pins DIN 258

2 Hexagon nut DIN 934

   with washer

3 Motor foot

4 Alignment plates

5 Soleplate or steel

   foundation

Secure the motor feet on the fixed supports with two dia-gonally opposite tapered pins. Only drill and ream out the holes after the final alignment process is complete!

 

 

    Vibration dampers are flexible rubber components used for the purpose of absorbing vibrations when setting up machine sets with shared base frames. If machine sets are to be set up to ensure isolation from vibration, reinforced base frames with high levels of torsional rigidity must be used. Casting is not appropriate in such cases! For the most part, acoustic emissions generated by the machine set and vibrations (as a result of residual imbalance, for example) are converted to heat in the sound absorbers rather than being transferred to the substratum or the bearing structure. If distortion can occur within the underlying structure bearing the load (on ships, for example), the base frame is only set down at three points.
     
   
 
     

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