Vibration diagnosing method and apparatus for a rotary machine

A method for diagnosing a vibration in a rotor of a rotary machine comprising the steps of:

• detecting the number of rotations and the vibration in the rotor at a plurality of measuring points disposed at intervals along a direction of the rotor shaft when the rotor is rotating and providing signals representative thereof;
• extracting vibration components synchronized with the number of rotations of the rotor from the signals representative of the detected vibration of the rotor at the plurality of measuring points;
• comparing the extracted vibration components with reference values therefor corresponding to normal vibration in the rotor of the rotary machine for determining that the detected vibration is abnormal when at least one of the extracted vibration components exceeds the corresponding one of the reference values therefor and that the detected vibration is normal when all of the extracted vibration components do not exceed the corresponding reference values therefor;
• calculating abnormal vibration components upon determining that the detected vibration is abnormal by subtracting predetermined values representative of respective rotor vibration components in a normal state of the rotor from the corresponding extracted vibration components so as to obtain abnormal vibration components;
• and
• comparing a pattern of amplitude values of the abnormal vibration components with patterns of previously determined vibration amplitude values at the respective measuring points when an unbalance is provided at different positions of the rotor for determining an unbalance originating position in the rotor according to a selected one of the predetermined unbalanced vibration patterns which is the most similar to the abnormal vibration pattern.

A vibration diagnosing apparatus for rotary machine for diagnosting a vibration in a rotor of the rotary machine by detecting the number of rotations and the vibration in the rotor when the rotor is rotating, comprising:

• a rotation sensor for sensing the number of rotations of the rotor;
• a vibration detector for detecting a vibration generated in the rotor at a proper position of the rotor;
• a vibration analyzer for extracting an unbalance vibration component synchronized with the number of rotations by using a vibration signal from said vibration detector and a phase reference signal obtained from said rotation sensor;
• judging means for judging whether said unbalance vibration component is normal or abnormal by comparing an unbalance vibration component derived from said vibration analyzer with a reference value;
• memory means for previously storing a rotor vibration component in a normal state;
• first arithmetic means for extracting an abnormal vibration component on the basis of an abnormal unbalance vibration component derived from said judging means and a normal vibration component stored in and derived from said memory means;
• second arithmetic means for specifying a maximum amplitude of an abnormal vibration component from said first arithmetic means;
• third arithmetic means for normalizing said abnormal vibration component on the basis of the maximum amplitude of the abnormal vibration component derived from said second arithmetic means;
• pattern memory means for previously storing the normalized pattern of the unbalance vibration;
• unbalance originating position identifying means for identifying a position in the rotor where the unbalanced vibration causing the abnormal vibration is generated on the basis of the comparison of the normalized abnormal vibration pattern from said third arithmetic means with the normalized unbalanced vibration pattern from said pattern memory means.