## Vibration isolation on weak and finite support - a model and parameter study

Peter Blom

ACAD International AB

Götlundagatan 34, 12471 Bandhagen, Sverige

peter.blom@acad.se

1. Abstract

A model of the vibration isolation for machines on weak and finite supports is discussed. Data from measurements on fans and supports are presented. The data are introduced into the model. Finally an example is given to illustrate the use of the model through the use of real input data.

2. Introduction

Practically all machines with moving parts will give rise to disturbances that can cause noise and vibrations. The vibration isolation is dependent on the support and in order to accurately predict its efficiency, a good understanding of the whole system is nececcary. An analytical model allows for handling of the whole system. However, correct knowledge of its parameters is essential as well as reliable input data – normally the requirement is set as a“highest” noise or vibration level. Therefore various mobility tests on floors have been performed, along with thorough measurements on medium sized fans.

3. Model

The model is based on the different mobilities inherent to the system. In its most simple form this involves, respectively, the mobility of the source, the isolator and the support.

4. Floor Measurements

Existing floors have been tested through impact excitation and the point mobilities have been inserted into the model. The model then yields the vibration isolation.

5. Fan Measurements

Knowledge of the disturbances of radial fans is obtained through measurements. The forces were measured with force transducers as a function of revolution speed, force and flow.

6. Conclusions

An analytical model that predicts the vibration isolation on finite and weak supports is complemented with data from floor measurements and measurements on fans. This has proved a valuable tool in assessing potential disturbances from machines.