Transmission of Vibrations through Vibration Isolators, Theory and Application

Abstract

Vibration isolation of machines, machinery, technological and civil structures has become an inseparable part of their design. Machines can generate energy with very strong low-frequency vibrations which can affect nearby neighbouring machinery, structures and humans. The transmission of vibration energy is highly dependent on isolation of the frame support and/or usage of resilient foundation mountings. On the other hand, improper vibration isolation of a particular system may results in negative dynamic effects occurring in connected/surrounding technological and civil structures, including working spaces of the machine. Well-designed vibration isolation of potential sources can not only effectively reduce vibration energy into supporting and surrounding structures, but also improve sound energy transmission and fatigue characteristics. The presented paper investigates the conditions for reducing transmission of low frequency vibration energy from a recirculation ventilator and air-conditioning unit employing different types of vibration isolators. The solution of this problem is based on theoretical knowledge and existing methodology for transmission of longitudinal and transverse waves including measurement of the structures involved. Theoretical results were compared with vibration measurements for different conditions and configurations of vibro-isolating elements. Application of specific dynamic sources with respect to blocking forces and wave transmission where also performed to determine their effects on the machine foundation and transmission of energy to its surroundings. Finally, the paper suggests some measures that can be taken which will effectively reduce unwanted vibration energy occurring on the foundation of the machine as well as the machine itself and its immediate surroundings.