Vibration Audit - Paper Machine Speed Increase

Paper mills depend upon well running, low maintenance paper machines for best product quality, high efficiency, and low cost operation. When a paper machine’s speed is increased the efficiency must not drop. The new speed must not excite a resonance resulting in high vibration levels with increased sheet breaks and poor bearing life.

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 is 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 are excited when the speed is increased. This will ensure that there will not be vibration problems when the machine speed is increased.