Glossary

Vibration audit

survey of current vibration to determine if a problem exists now or at potential future operating conditions

A vibration audit can help ensure smooth and low-maintenance operation by minimizing vibration.

Excessive vibration is always the interaction of dynamic forces, with the dynamic machine stiffness and mass. The dynamic stiffness varies with frequency, resulting in resonance at some frequencies.

 

Excessive vibration at current operating speeds may be analyzed using an Operating Deflection Shape (ODS) analysis. During operation, the amplitude ratios and phase difference are measured and then animated on a stick figure of the structure. This information is then used to determine possible solutions to the problem.

Resonance problems are assessed using two main procedures, a speed sweep and modal testing. The speed sweep shows the vibration amplitude at the speed range of interest. Modal testing determines the vibrational response due to a measured input force.

When the vibration characteristics are known, plans can be made to modify the structure such that no resonances shall be excited when the speed is increased. Thus, productivity may be improved, and vibration problems avoided.

 

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