Levelmount_Machine_Mounts

4 The following section explains some of the basics of vibration technology. It aims to help understanding the information in this technical brochure, and our solutions to your vibration problems. Problem Vibrations and shocks have a negative impact in many areas. Poor quality when working with measuring and precision equipment, reduced employee efficiency, or structural damage, are just a few examples. To assess the impact on people and structures, DIN standards and VDI guidelines were developed. Procedure Information on the machine and installation site is the basis for an assessment. This information will help to decide on measures for isolating vibration. Standards provide reference values that differ according to building type, excitation condition and exposure period. On page 30 of this brochure, the procedure is demonstrated with the help of a case study. Vibration isolation In principle, there are two different types of vibration isolation:  source isolation (active)  receiver isolation (passive) The isolation can be divided into two types:  isolation of periodic vibrations  shock absorption Periodic vibrations result from imbalances of rotating machinery parts or mass moments of stroke movements. The isolation rate is dependent on the ratio of the excitation frequency (for example, engine speed) to the natural frequency of the vibration isolator (tuning ratio [ η ]). As shown in figure 1 (page 2), an isolating effect takes place only from a tuning ratio of η = 2; below this value an increased distur- bance force must be expected. Damping [D] reduces the increase in disturbance forces. How- ever, below η = 2 damping degrades the isolation effect (see page 31, Dynamic Properties). This means in practical applications that vibration isolating is a compromise between tuning ratio and damping. Shocks are characterised by their strength, duration and behaviour. They result, for example, from releasing work in a press. The characteristic short, high-peak force is spread over a more protracted course with low residual forces. The cushioned system vibrates with the natural frequency of the vibration isolator. The lower the natural frequency of the vibration isolator, the lower the transferred residual force becomes. Passive isolating means to isolate machines (e.g. measuring equip- ment) and machine parts against external disturbance forces. Theoretical analysis does not distinguish between active and pas- sive isolation. Therefore, the degree of isolation can be determined analogous to the active isolation. In practical applications, passive isolation elements with low natural frequency are used. The excitation frequencies are usually natural frequencies of the floor in the case of floormounted installa- tions or low-frequency shock excitations. The best isolation values are achieved with LEVELMOUNT pneumatic spring elements. Structure-borne sound insulation Structure-borne sound insulation represents a special type of vibration isolation. Structure-borne vibrations spread wave-like within a machine or machinery and excite components to vibrate. These vibrations are then audible as sound waves (secondary airborne noise). Structure-borne sound waves are reflected by boundaries between different materials. The degree of reflection, and thus the effectiveness of the structure-borne sound insulation are dependent on the magni- tude of the impedance discontinuity. Impedance discontinuity is the difference between the elasticity and density of the different materials. Please visit us at www.effbe.de General information on vibration technology