Rotating blades monitoring using standard turbine instrumentation

Abstract

Ensuring the reliability of the steam turbine is fundamental task for its proper operation. Early detection of any failure avoids material and financial losses. A very important task in turbomachinery diagnostics is monitoring of rotating blades vibration, especially in terms of the last stages of low-pressure turbine parts, where, in general, the vibration can reach the important level due the blades length. The commonly used methods are based on stress evaluation using strain gauges or on the non-contact measurement of blade tips – blade tip-timing (BTT) method. Rising demand for low-cost monitoring systems suitable for blade monitoring has led to development of a new approach based on signal processing of standard turbine instrumentation. The symptoms of blade vibration could be also visible in signals from relative shaft vibration (SV) sensors, which are standardly installed in turbine journal bearings. This paper illustrates the principles and possibilities of the approach based on processing of SV signals for monitoring of actual state of rotating blades. Finally, the comparison of parallel measurements using SV and BTT in operation of steam turbine reveals the properties and advantages of both methods.

A Novel Method of Impeller Blade Monitoring Using Shaft Vibration Signal Processing

“…From this Figure, the presence of blade vibration components is clear. The detailed description of this principle was published in the literature recently [7][8][9][10]. For proper impeller blade state diagnostics, the exact parameters of the blade components from the shaft vibration signal need to be obtained.…”

Natural Frequency Evaluation of Low-Pressure Stage Blade of a 210 MW Steam Turbine

“…It is required to do a vibration study of the rotor blades to assure high reliability. Vibration can reach unsafe levels in rotating blades, particularly in the last stages of low-pressure turbine sections, due to blade length [1][2] [3]. The blades of the last stage are much longer than those of the preceding stages upstream.…”

“…Rotor vibration can be used to describe the LP blade vibrations qualitatively. When describing the data quantitatively, it is necessary to make a comparison with the actual blade vibration levels [1]. While operating at low frequencies, ANSYS 2019 R2 was used to calculate the natural frequency of the last stage LP (low pressure) Steam Turbine power plant's blades [5].…”