A Microcomputer Based Vibration Diagnostic System for Steam Turbines and Turbo-Generators in Power Plants

A new shaft-vibration diagnostic system for rotating machinery in power plants has been developed. This system, with its microcomputer, can be effectively applied to solve almost all the vibrational problems which occur during load operation or inspection. For frequency spectral analysis, the Walsh to Fourier transform is used with some modifications to reduce the microcomputer load. New firmware is also developed. With these improvements it is possible to diagnose simultaneously shaft vibrations for a five second period at a maximum of twelve points. This system has been successfully used in field tests to diagnose abnormal shaft vibrations caused by machinery unbalance or rubbing of steam turbines and turbo-generators. Large-scaled thermal power plants are in great demand to supply the middle load, i.e., the daily or weekly cyclic load above the base load. This has increased severity of their operating conditions, for example, by increasing the number of start/stop operations in a given period. In order to alleviate these conditions, microcomputer controlled systems have been developed. Extension of their use has led to applications in malfunction diagnosis and scheduled inspection tasks. For effective power plant operation and maintenance, it is important to diagnose properly shaft vibrations in such rotating machinery as steam turbines and turbo-generators. The following method is usually used. During the load operation, overall vibration is measured continuously at all bearings.