The Problem: Torsional Vibration Induced Failure of Rotor Components

Turbine/generator rotors have experienced wear and fatigue damage as a result of torsional shaft vibrations. One source of torsional vibration excitation is generator power perturbations resulting from rapid load changes (e.g. steel mill arc furnaces). The transient excitation may excite torsional resonances in the 1 to 200 Hz range. High amplitude torsional vibration can cause relative motion of the rotor components inducing slippage of shrink fits (couplings, retaining rings, disk bores) that can lead to fretting wear and fatigue. Torsional vibration has also contributed to keyway cracking and coupled blade-disk vibration, resulting in fatigue of last stage blading.

The Solution: Transient Torsional Vibration Monitoring

SI has developed a real time, high speed, PC based TTVMS™. The TTVMS™ provides up to 32 channels of continuous monitoring and acquisition of rotor torsional vibration sensors, generator power, current, and voltage. The system provides individual sensor warning and alarm indication and automatically records all channels of data upon alarm excursion. In addition, the system provides automatic trending, periodic data capture, and manual test capabilities.

Data analysis includes time history, two-channel FFT analysis, orbit, and waterfall. A unique aspect of this system is that it is dedicated to the detection of vibration amplitudes and power directly related to the individual rotor resonance. Each channel may have up to four separate frequency bandwidths with separate warning and alarm levels. Special alarm algorithms provide elimination of false alarms from non-related, electrical noise spiking.

The TTVMS™ is part of SI’s unusual combination of root cause expertise, which includes vibration, fatigue and material testing and analysis.

If you would like more information regarding this product, please contact SI, or click here to read the system specification.