The TVS™ and TVS+™ systems accurately measure speed, torque, and torsional vibration.
Torsional Vibration Measurement
Torsional vibration measurements help you avoid downtime and surprises.
Torsional vibration is the angular vibration of a shaft about its axis of rotation. It can be induced by variations in shaft load, unbalance, or bearing degradation, or other undesirable characteristics of the drivetrain.
For example, Variable Frequency Drives (VFD) are notorious for generating torsional vibration in the coupled shaft. More generally, the dynamic behavior of the whole drivetrain consisting of the driving force (turbine, VFD or other motor), the coupling shaft, and the driven load (such as compressor, alternator, or pump) generates torsional vibrations at given speed and acceleration conditions.
Other phenomena such as fluctuations in the available electrical power can also generate swings which induce torsional vibration.
Torsional vibration frequency is assessed by measuring variations in shaft speed at high resolution. This can be performed in a single plane with a single sensor; however, a 2-plane, 2-sensor arrangement will give more accurate data, allowing differentiation between synchronous speed changes and actual torsional vibration.
Torsional vibration amplitude is determined by measuring the twist angle between two locations on the shaft. This requires a dual-plane, dual-probe sensor. Knowledge of amplitude is a critical factor in determining if a torsional vibration poses a high cycle or low cycle fatigue problem or if the vibration is benign for the sizing of the shaft.
Torsional vibration is usually not monitored continuously, resulting in unplanned failure. Common failures happen in the coupling shaft. Both disc couplings and diaphragm couplings have experienced torsional failures. Failures in other components, although not as frequent, also happen.
Torsional vibration measurements help identify issues in rotating equipment in lieu of scheduled maintenance intervals or prior to catastrophic failure. Foreknowledge of a problem before failure and avoiding premature maintenance, results in less down-time and lower maintenance costs.
Torsional vibration on a piece of equipment can occur as a transient phenomenon during ramp up or ramp down while crossing specific speeds and frequencies of rotation. It is essential for the operator to know where the torsional vibration frequencies are, to determine a safe range of operation and to avoid running for prolonged durations at damaging speeds.
Our TVS™ and TVS+™ systems measure torsional vibration of your equipment optically.
Torque measurement helps you plan your machine preventive maintenance intelligently.
Non-Contact Torque Measurement of a Rotating Shaft
Accurate torque measurement is critical to understanding the health of the rotating system. Torque monitoring over time can alert the user to system degradation. For example, wear in pump seals decrease the pump efficiency over time; these show as a variation in torque over time. Monitoring changes in torque through continuous measurement of shaft twist is a reliable way to alert an operator to the need of preventive or corrective maintenance.
Continuous torque monitoring is also a reliable way to detect system aberrations or over-torque conditions that are leading indicators of system failure. Setting alarms based on detection of these anomalous torque events allows operators to perform inspection of the machinery, avoiding further degradation of the equipment.
Additionally, combining the TVS+™ torque and speed measurement results in a high accuracy measurement of shaft power and enables precise calculation of system efficiency.
Absolute vs. Relative Torque Measurement
Do you need to monitor absolute torque or relative torque? The TVS+™ system measures absolute twist, which can be used to measure absolute or relative torque. However, users must understand the difference because absolute torque places a premium on accurate calibration.
For many users, the critical parameter is the change of torque over time. A decrease in torque is an indicator of system degradation. This can be due to leaks, wear in seals or bearings, misalignment, and many other factors. Conversely, users can track improvements they make to rotating machinery by tracking the resulting increase in torque.
The TVS+™ system tracks absolute twist. The measurement of the twist angle between the two probes does not require any calibration.
If absolute torque is required, conversion from twist to torque is necessary. Converting twist to torque requires calibration. It can be performed by calculation, given the geometry and material properties of the shaft; or it can be physically calibrated by submitting the shaft to a known torque and measuring its angular deflection.
For users who are only concerned about changes in torque, the goal is to measure torque differences from a baseline condition. In that case, the measurement of twist – or change in twist over time – is sufficient, and there is no need to perform any calibration.
Accurate shaft speed measurement
Hold your system accountable to the speed limits. Speed measurement helps you ensure that your system is operating as intended. Speed is critical in a variety of applications across industries.
- In power generation speed changes can lead to fluctuations in frequency of the AC power produced.
- In films and paper manufacturing variations in roller speed can lead to inconsistent product dimensions and scrap.
- In automotive and industrial environments variation in speed can be an identifier of unbalance in the system.
Taking accurate real time speed measurements can allow you to automate system shut down before failure, identify out of tolerance product, and account for variation in your manufacturing system. Our TVS™ system accurately measures speed and speed variation of your rotating assembly.
Using TVS™ to Measure Speed, Torque, and Torsional Vibration
These measurements can be achieved several ways, but the greatest advantages of our optical system approach are that:
- Optical systems are intrinsically safe and immune to electromagnetic interference. The optical probes can be located in any ATEX zone. Long optical leads allow the instrumentation to be located remotely, away from the hazardous area. Instrumentation can also be enclosed in an ATEX rated enclosure.
- The sensor does not need to make contact with the shaft in order to give high accuracy measurement. Rotating systems are sensitive to balance and loading conditions, by opting for a non-contact sensor you avoid these potential risks.
- Optical sensors are easy to install, with very little to no modification to the shaft. One version of our product does not require any marking or change to the shaft. Another version only requires a rugged label to be affixed in two places on the shaft.
- Installation of the system can be done both retroactively on existing systems or designed into the system upon conception.
The ease of installation combined with the minimally invasive aspect of the sensor system makes it an ideal measurement tool for a variety of applications and environments.