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For each vibration problem the optimum solution!

Spring devices

Field of application

Different base isolation concepts for a hydraulic press

Spring devices can be used for solving a wide range of vibration isolation problems.A typical industrial application is the base isolation of heavy duty machinery like presses or forge hammers. In power plants spring devices are installed to isolate coal mills, gas- or diesel engines, turbines, pumps or condensers. Compressors or big fans are other examples where the isolation with spring devices avoids that the vibration induced by this equipment – the source of the vibration – is transmitted to the environment (isolation at source).

Spring devices can also be used to isolate a vibratory system against vibrations induced by the environment (isolation of recipient). Examples for this are the base isolation of precision equipment or structures like buildings against vibrations induced e.g. by traffic.

In any case base isolation with spring devices is a state of the art approach to reduce the effects of unwanted vibration thus allowi

  • protection against shocks and continuous excitation for man, machines, structures and building
  • control of operational vibrations within the admissible limits
  • reduction of wear and tear of machines, equipment and structures

As a consequence, with a good base isolation concept for e.g. a big hydraulic press,the foundation of the machine may be designed in a significantly lighter way. This concept allows the installation of vibrating equipment in almost every location and it allows to considerably reduce the cost of the foundation itself.

Viscoelastic dampers

Damping – Dissipation

Viscoelastic dampers reduce vibrations by converting kinetic energy into heat thus damping the motion of the system. Damping, as a method to reduce unwanted vibrations, is most effective in cases where the vibratory system is excited with a frequency close to its natural frequency viscoelastic dampers are designed in a way that they can be used in a wide frequency range.

Isolation

Spring devices are the prototype product to isolate a vibratory system from a source of vibration. They are to be positioned between the system and the source in order to minimize the energy transfer from the source to the system. The natural frequency of the vibratory system f0, defined by the spring devices and the load they carry, has to be designed in a way that it is significantly lower than the main natural frequency fE  of the vibration source.

Field of application

Installed viscoelastic damper in a nuclear plant

Viscoelastic dampers may be used to solve very different vibration problems. A typical example is the damping of operational vibrations in an industrial piping system e.g. in a power plant. Whenever the piping systems cannot be isolated from the source of vibration, damping might be an adequate measure to reduce the motion of the piping to an acceptable level.

Another example is the damping of shocklike forces induced e.g. by a large forge hammer. In this case the damping device needs to absorb a significant amount of energy in a very short time, so that the system comes to rest as quickly as possible allowing the start of the next operation of the hammer with minimum recovery time. Viscoelastic dampers may also be used together with spring devices e.g. for the baseisolation of a smaller diesel engine foundation in a power plant.

During start-up, the engine will continuously increase its speed up to the operational frequency. Spring devices are designed in a way that at operational frequency the surroundings are well isolated from the vibration of the rotating machine. In fact the  natural frequency of the system consisting of engine,foundation and spring devices has to be much lower than the operational frequency. Therefore when starting up the turbine it will increase its frequency from zero to the operational frequency thus passing the resonance range of the system around its natural frequency – that is where it needs a viscoelastic damping element to damp the motion of the system.

Unfortunately sometimes dampers are proposed as an alternative to shock arresters (snubbers). The typical function of shock arresters is to make sure that mechanical connections are protected in case of shock like forces acting on these connections. Therefore these devices have to provide a rigid link parallel to the connection to be protected that can transmit these forces instead of the connection. An example for this is e. g. the connection of a steam generator in a nuclear plant to the piping that must be protected in case of a seismic event. Here viscoelastic dampers are not the right choice to protect the connection as they do not provide the necessary rigidity with the necessary reaction time.

For vibration reduction products please refer to our joint venture partner VICODA.