Train Balance, Rotordynamic Analysis Case Study

Problem

A high-speed dual impeller fan, used for process, was experiencing high vibrations.

Solution

The original vibration on the fan at running speed was 1.93 inches per second (ips) and the vibration after initial field balancing was 0.41 ips at running speed. KHE attempted further balancing but was unable to decrease vibration amplitude. A resonance test of the rotor indicated the first critical speed was near the running speed which amplified the vibration problem. KHE performed an analysis of the rotor and wheels in order to predict the effect of a heavier wheel on the rotor and its dynamics response. This analysis indicated the critical speed would decrease approximately 11%. Heavier fasteners would be required in construction of the new wheels to maintain an acceptable factor of safety for the vane’s attachment to the front and rear wheels.

Results

The fan was modified according to KHE recommendations, resulting in reliable operation.