Peter
Blom
ACAD
International AB
Götlundagatan
34, 12471 Bandhagen, Sverige
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.