Diagnostics of cavitation mode plays an important part in safe unit centrifugal pump operation, as soon as cavitation presupposes massive destruction of rotor wheel surface and pipe-lines, and additional vibration loads on unit construction. Currently, the main method of pump unit cavitation mode monitoring is spectral component analysis of case vibration signal. However, spectrum analysis requires precise data on pump unit construction (number of blades on rotor wheel, bearing types). Lack of such data or its irrelevance to the real one will lead to errors in cavitation mode measurements. Consequently, still, one of the urgent problems is development of new cavitation diagnostics methods using algorithms invariant to construction type of the unit.
The article dwells upon cavitation diagnostics of pump units by means of modern non-linear dynamics trend - fractal theory in which Hearst index related to a vibration signal dimension is used as a diagnostic feature. The main advantage of this feature is its invariance to the signal level and, consequently an independence from power and size characteristics of the unit.
The results of Hearst index usage during processes of pump unit testing and operation are also given in the article. It is shown that sensitivity of the feature equals or, in some cases, exceeded sensitivity of a spectral method.
Consequently, Hearst index allows to increase reliability rates of results issued by expert system of centrifugal pump unit health diagnostic system.
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Kostyukov V.N., Boychenko S.N. Real-time diagnostics and monitoring of pump unit cavitation mode // Condition Monitoring and Machinery Failure Prevention Technologies (СМ/MFPT 2014)
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