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1

Which are the ways to control the vibrations?

In practice, there are a number of situations where it is possible to reduce but not eliminate the forces of dynamic (time varying) that excite our mechanical system resulting in the appearance of a vibration problem. In this sense, there are different methods of raising the vibration control:

  • The knowledge and control of the natural frequencies of the system in order to avoid the presence of resonance under the action of external excitations.
  • The introduction of damping or any type of energy dissipating mechanism in the face to prevent excessive system response (large amplitude vibration), even if there is a resonance.
  • The use of vibration isolating elements that reduce the transmission of excitation forces or vibrations between the different parts that make up our system.

2

How is the performed control of the natural frequencies?

We know that when the excitation frequency coinceide as a natural frequency of the system, take place a phenomenon of resonance. The most important feature of resonance is that it gives rise to large displacemen to significantly amplify the vibration. In most mechanical systems, the presence of large displacements is an undesirable phenomenon because it causes the appearance of stresses and strains that can cause equally large mechanical failure. Consequently,resonance conditions should try to be avoided in the design and construction of mechanical systems. However, in most cases, the excitation frequencies can not be controlled to be imposed by the requirements of a nature functional of the machine (eg, speeds). In this case, the objective is to control the natural frequencies of the system to avoid the presence of resonances.

The natural frequency of a system can be changed by varying both the mass (m) and stiffness (k) thereof. In many situations in practice, the mass is not easy to change, since its value is usually determined by the functional requirements of the machine. Therefore, the stiffness is the parameter that is modified most common way in altering the natural frequencies of a mechanical system. For example, the stiffness of a rotor can be changed by changing the number and placement of the support points (bearings), or by installing a bed of inertia.


3

What precautions should be taken into account in the connection and insulation of pipes and ducts?

Pipes:

Flexible connections pipe used for the following functions:
 

  • Provide flexibility to piping supports so that the vibration of the equipment to work properly.
  • Protect the equipment from the stresses caused by misalignment and / or contraction and expansion of the pipes.
  • Reduce noise and vibration transmission to the pipes and from these to the structure of the building.

The connectors can be flexible rubber hoses or metal braid or rubber expansion joints, and should be chosen depending on the diameter of the pipe, with minimum lengths specified in a new board (to consult in the standard).

In general, the flexible connectors are unable to reduce noise transmission through the fluid. In addition, connectors flexible nonmetallic material becomes rigid when the pressure of the fluid is high and, consequently, reduces its insulating capacity. In these instances, where the machine room is near sensitive areas, it is necessary that the pipes are elastically supported by springs and / or gums, as when the pipes must connect to machines that rely on vibration isolators.The supports of these pipelines must be chosen with a deflection equal to or greater than the vibration isolators of the computer you are connected and at least be installed throughout the engine room.

The pipes should never put a strain on the machinery to which they are connected.
In no case should be allowed direct contact between the metallic material of the pipe and bracket.

Ducts:

The ducts must connect to the fans or air handling units through flexible fabric connections and / or glue.

4

How is the introduction of damping in a mechanical or structural?

Although the damping is often overlooked in order to simplify the analysis of a system, especially in the pursuit of their natural frequencies, all real mechanical damping have a greater or lesser extent (the springs have almost no damping because they work by rigidity, elastomers while providing a higher level of damping). His presence is very helpful. If the system is in a case of forced vibrations, the response (the amplitude of the resulting vibration) tends to be amplified near the resonances, the more the lower the damping.The presence of damping always limits the amplitude of vibration.
If the force or forces excitation frequencies are known, it is possible to avoid changing the natural frequency resonance of the system and away from that or those.

In certain structural applications, damping can also enter through the seams.

TECNOELASTICA installed, when necessary, elastomers brought in the support bases of the system and / or stabilizing internal metal spring isolators).

5

What advantages does the use of inertia benches?

The elastic supports can be installed directly on the supports of the equipment or on a base which directly and rigidly fixing the computer.

The first solution is applicable only for small and compact, equipped with sufficient structure. However the team benches should be used when the computer does not have a home base sufficiently rigid when required natural frequency decrease by increasing the mass of the system or when required by the alignment of their components (eg, motor and fan motor pump).

The use of the benches also presents the following advantages:
 

  • Election of the status of the brackets so as to increase the stability of the machine to lower the center of gravity and widen the base of support.
  • Increased supported mass, which requires the use of stiffer elastic supports, thereby decreasing the amplitude of the oscillation (important for the connections of ducts, pipes and electrical).
  • Improved uniformity of weight distribution on the supports.
  •  Reducing the impact of external forces.



The banks should have sufficient rigidity to withstand the stresses caused by the operation of equipment.

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