Diagnostic system and method, especially for a valve
AssigneeSiemens Aktiengesellschaft
InventorsKlaus-Dieter Fiebelkorn, Gerhard Klebert, Alf Puettmer
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Abstract
The invention relates to a diagnostic system and method, especially for a valve (2) that can be actuated by a positioner (9) via a drive (6). The system utilizes a sensor (12) for recording structure-related sound and has a device (14) for evaluating a recorded measurement signal (13). A spectral region greater than 50 kHz is evaluated for conducting fault recognition. A fault indication signal is generated if the intensity of the measurement signal in this spectral region exceeds a defined threshold value. The sound caused by cavitation is primarily evaluated for conducting fault recognition.
Claims22
A diagnostic system comprising:
- a sensor operable to sense structure-borne noise;
- an evaluation unit operable to evaluate a recorded measurement signal, wherein the measurement signal is representative of at least a portion of the structure-borne noise and said evaluation unit is configured such that a spectral region of the measurement signal above a first limit frequency, where the first limit frequency is greater than 50 kHz, is evaluated for fault detection, and a fault indication signal is generated if an intensity of the measurement signal in the spectral region exceeds a threshold;
- and
- a determining means for determining a strength of background noise in the measurement signal by measuring a signal strength in a spectral region above a third limit frequency, the third limit frequency being greater than a second limit frequency and selected such that influence on the measurement signal by cavitation noise is minimized, determining a strength of the cavitation noise in the measurement signal by measuring the signal strength in a spectral region between the second limit frequency and the third limit frequency, and determining the threshold value based on the strength of the background noise;
- and generating the fault indication signal if the strength of the cavitation noise exceeds the threshold value.
A diagnostic method comprising:
- sensing structure-borne noise;
- evaluating a recorded measurement signal for fault detection, wherein a spectral region of the measurement signal above a first limit frequency greater than 50 kHz is evaluated;
- generating a fault indication signal if the intensity of the measurement signal in the spectral region exceeds a threshold value;
- determining a strength of background noise in the measurement signal by measuring a signal strength in a spectral region above a third limit frequency, the third limit frequency being greater than a second limit frequency and selected such that any influence on the measured signal strength by cavitation noise is minimized;
- determining a strength of the cavitation noise in the measurement signal by measuring the signal strength in a spectral region between the second limit frequency and the third limit frequency;
- determining the threshold value based on the strength of the background noise;
- and
- generating the fault indication signal if the strength of the cavitation noise exceeds the threshold value.
A method for determining a fault in a valve through which a gaseous or a liquid material flows, the method comprising:
- measuring an acoustic signal generated in a vicinity of the valve as the gaseous or liquid material flows through the valve;
- separating the acoustic signal into a low frequency portion and a high frequency portion;
- determining a strength of background noise in the acoustic signal by measuring a signal strength in a first spectral region of the high frequency portion selected such that influence on the measured signal strength by cavitation noise is minimized;
- determining a strength of the cavitation noise in the acoustic signal by measuring the signal strength in a second spectral region of the high frequency portion lower than the first spectral region;
- determining a threshold value based on the strength of the background noise;
- and
- generating a fault indication signal if the strength of the cavitation noise exceeds the threshold value.
Dependencies are inferred from the claim text.