Vibration diagnoses in fossil fuel power plants

Abstract

Vibration problems in fossil fuel electric generating plants rated from 12.5 to 850 MW were diagnosed by existing methodologies involving state‐of‐the‐art techniques over the past five years. The vibration diagnoses covered the areas of excessive vibration of rotating machinery, dynamic response of machine foundation, shaft misalignment vibration resulting from foundation differential settlement, and vibration of piping systems. The fast Fourier transform (FFT) technique analyzed the causes of rotating machinery vibration. The severities of the vibrations were assessed using international standards. The machine vibration magnitudes attributed to dynamic responses of their foundations were analyzed by using the FFT transfer function technique. The foundation differential settlement was investigated from the measured results of the foundation stiffness. The time histories of both water hammer and steam hammer were studied theoretically and experimentally for the development of prediction methods and for the elimination of transients. Steady‐state piping vibration was correlated with the measured pressure waves in the pipes to analyze the pipe stress waves. Installation of rigid restraints and an increase of pipe wall thickness overcame the problem of fatigue cracking.