US 4,380,172 A · On-line rotor crack detection

Abstract

A method is disclosed by which incipient cracks are detected in the rotor of a fluid powered turbine while the turbine is on-line and running under substantially normal load. In a preferred form of the invention, vibrations are monitored in the rotor and signature analysis of the normal background vibration pattern is obtained to establish the spectral content of the normal vibration signal. The turbine rotor is then transitorily perturbed, preferably by changing the temperature of the motive fluid (steam temperature is changed for example in a steam driven turbine), and the signature analysis is again performed to determine changes in the vibration pattern. An increase in the amplitude of the fundamental frequency and the appearance and increase in amplitude of higher harmonics following rotor perturbation is indicative of the presence and size of a crack in the rotor.

Claims11

Dependent claims

For a motive fluid powered turbine, a method for detecting incipient cracks in the turbine rotor while the turbine is under load at substantially normal operating speed, comprising the steps of:

(a) obtaining from at least one vibration sensor, adapted to sense vibrations in said rotor, a signal representation of such vibrations;
(b) determining the spectral distribution of said vibration signal;
(c) causing a transient perturbation of said rotor to establish a transient vibratory response therein by changing the temperature of the turbine motive fluid;
(d) determining the spectral distribution of said vibration signal resulting during said transient vibratory response, and
(e) comparing the spectral distribution obtained in step (b) with the spectral distribution obtained in step (d), the change in spectral distribution between that of step (b) and that of step (d) being indicative of the presence and size of cracks in said rotor.

2 more elements

Dependencies are inferred from the claim text.

On-line rotor crack detection

Life of this patent

On-line rotor crack detection

Life of this patent

Abstract

Claims11