Machinery Lubrication

Machinery Lubrication March April 2019

Machinery Lubrication magazine published by Noria Corporation

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Page 18 of 85

Vibration analysis is often used by reliability special- ists to monitor the dynamic mot ion s of m ac h i ne components. Likewise, oil analysis is performed to examine the composi- tion of fluid constituents. However, neither technique checks the actual lubrication of tribological systems in operation. is article will explain how sonic and ultrasonic stress wave analysis can extend vibration from mechanical to tribo-mechanical condition monitoring, thereby covering important gaps between vibration and oil analyses. Intelligent Decimation Modern vibration ana ly zers convert analog vibration signals into an oversampled digital data stream. Digital data is normally sampled at high ultrasonic rates. is high- frequency digital data is decimated to a much lower maximum frequency based on the running speed of a mechanical component. Traditional decimation is effective for extracting sinusoidal motion, rotation, displacement and resonance of machine components. Intelligent decimation operates on the original high sampling rate data before arbitrary decimation processes destroy the high-fre- quency content. is stress wave a na ly sis tech n ique qu a nt i f ie s time-domain events such as impact, bearing and gear defects, slipping, rubbing, severe sliding, mechanical friction, and electrical arcing. It can supplement traditional vibration analysis for rotating machinery and be a primary technique for other equipment types, such as slow- moving, reciprocating, articulating and high-voltage equipment. The intelligent decimation numerical algorithm (I-DNA) creates sonic and ultrasonic maximum peak detection stress waveforms for anal- ysis. Event stress waves originate from a point of contact or compres- sion and propagate through metals or fluids at the relative speed of sound, carrying information about the events that created the stress waves. e sonic range waveform (DNA500) exposes forceful acceleration events including rolling, compression and severe sliding, while the ultrasonic range waveform (DNA12) reveals friction-related events such as slipping, polishing and rubbing. The maximum DNA500 and DNA12 values, along with the ratios of DNA12 and DNA500, can reveal tribological characteristics from mechanical systems in relative motion. Lubrication Regimes e life of machine components is largely dependent on effective lubrication. Besides dry contact between components, there are four different lubrication regimes: boundary, mixed mode, elasto- hydrodynamic and hydrostatic hydrodynamic. Based on the load, speed, lubricant and other factors, equipment designers may select 100-micron-thick, fluid-film hydro- static and hydrodynamic planar bearings or 1-micron-thick, fluid- f ilm elastohydrodynamic roller bearings. e duty cycle for machine operation may occasionally fall into a mixed mode or boundary lubrica- tion regime, such as when the speed Intelligent Decimation: Closing the Gaps Between Vibration and Oil Analyses OIL ANALYSIS Ray Garvey | I-care "Intelligent decimation can extend the range of faults detected and expand the types of machines monitored." 14 | March - April 2019 | www . I-DNA installations are easy to set up, configure and use.

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