tailieunhanh - Ebook The vibration analysis handbook: Part 2
(BQ) Part 2 book "The vibration analysis handbook" has contents: Accurate diagnosis of antifriction bearings, accurate evaluation of gears, analyzing and solving press roll and nip problems. | CHAPTER FIVE: INTRODUCTION This chapter describes procedures for identifying defects in antifriction bearings by analyzing frequencies generated by the moving parts. Defects on bearing raceways, rolling elements, and the cage generate different frequencies. The spectrum shape, amplitude, frequency, sum and difference frequencies, and the time domain signal are useful in identifying the nature, location, combination, and size of defects. Methods are presented to calculate the bearing frequencies; identify if the bearing is in a thrust or radial load; calculate the length of inner race defects with the time domain signal; and measure the length of a defect on the outer race in the frequency domain spectra. The nature of the defect, such as shallow flaking, deep fatigue spalls, corrosion, acid etching, fluting, and inadequate lubrication can be determined by analyzing the frequency and time domain data. These techniques can also identify bearings with excessive clearance and bearings that are not properly installed, such as those turning on the shaft or loose in the housing. Techniques used to predict the life span of a defective bearing are discussed. DATA COLLECTION Data collection is the most important step in evaluation of bearing condition. Data should be collected by placing the transducer in the bearing load zone with due respect to flexibility. If this is not done, the best signal definition may not be obtained. For example, with a radial bearing in a radial load, the best signal is obtained in the radial position. For an angular contact bearing or a radial bearing in a thrust load, the best signal definition is obtained in the axial direction. The machine internal geometry, as well as which problems generate radial or thrust loads, must be determined in order to properly place the transducer. Data should be taken where the transfer function is best; for example, put the transducer on a bolt head, not the cover. For pillow-block, tending side dryer, and .
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