Products : Vibration Monitoring

TTVMS™

Transient Torsional Vibration Monitoring System

The acronym for industry proven technology to monitor torsional vibration is TTVMS™. SI's TTVMS™ uses pulse trains from speed probes installed in the turbine housing around the speed pickup gear as the main input. The incoming signal is demodulated to create a voltage that is proportional to the instantaneous speed, which allows interpretation of dynamic variations in rotor speed as torsional vibration. Auxiliary inputs from various electrical transmitters can also be recorded for correlation with torsional events. The screen capture below shows the Automatic Monitoring Session screen, where four selectable frequency bands can be monitored on each of the five monitoring channels.


George Szasz at SI's TTVMS™
(TTVMS™ is a product of the SI Vibration Group)

Operating Modes

  • Automatic Monitoring
  • Manual Session
  • Data Analysis

Data Analysis Module Features

  • Time History
  • Peak detection
  • Root-mean-square (rms)
  • Digital filtering: low pass, high pass,
    band pass; 2 to 10 poles
  • Frequency spectrum using the FFT with outputs in power, root-mean-square (rms), peak, power density, rms density
  • Orbit plots (two selected channels)
  • Integration, single or double (two selected channels)
  • Differentiation, single or double (two selected channels)

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

Structural Integrity Associates (SI) has developed a real time, high speed, PC based Transient Torsional Vibration Monitoring System (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.

3315 Almaden Expressway, Suite 24, San Jose, CA 95118 :: PH:408-978-8200 FX:408-978-8964 info@structint.com