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How Wear Problems Reveal Themselves
Published in J. Blau Peter, Tribosystem Analysis: A Practical Approach to the Diagnosis of Wear Problems, 2017
Ferrography is an established method for wear debris separation and analysis in which a small sample of oil is allowed to drain down a ramp formed by a glass slide that is placed directly above a magnetic field (see Figure 2.3). Development of the method is credited to Bowen and Wescott in the 1970s (e.g., Ref. [27]). The magnetic field is designed to be stronger at one end of the slide than the other so that drifting particles are separated based on their relative magnetic response to the field strength. When the oil is so treated to form chains of particles along the length of the slide, the resulting arrangement is termed a ferrogram and is inspected under a microscope. Some ferrographs are called “direct reading” because the fer-rograms can be illuminated by a light source above and the signal can be detected by photodiodes beneath it. By using more than one photodiode, a range of particle sizes as large as 0.1 to 300 |im or greater can be sorted. Magnetic particles tend to group and separate along the field lines, but nonmagnetic particles are also detectable since they tend to stand out from the orderly magnetic particles. Like other forms of microscopy, ferrograms can also provide clues to the type of wear being produced and its likely location. They can be illuminated by reflected light, transmitted light, or polarized transmitted light to help sort out the kinds of particles and their sources. In addition, the slides can be heat treated (e.g., a few minutes at 315°C) or tempered to aid in compositional analysis [28]. Larger particles are associated with more severe wear. Some users target a particle size of over 30 | m as equating to “severe” or “abnormal wear.”
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Published in Heinz P. Bloch, Kenneth E. Bannister, Practical Lubrication for Industrial Facilities, 2020
Heinz P. Bloch, Kenneth E. Bannister
Successful analysis of a current wear-related problem requires many pieces of information and a skilled diagnostician. To this end, the practice of analytical ferrography has received recently prominence. Unlike other common instrumentation technologies, analytical ferrography is qualitative and requires visual examination and identification of wear particles. Numerous properties and features of the wear debris are inventoried and categorized. These include size, shape, texture, edge detail, color, light effects, heat treatment effects, apparent density, magnetism, concentration, and surface oxides.
Condition Monitoring
Published in Edgar Bradley, Reliability Engineering, 2016
Ferrography is the microscopic evaluation of a used oil sample, examining particle sizes from 10 μm to more than 1000 μm. This test should only be conducted by well-trained, experienced personnel. Ferrography yields two results:
Wer Debris Recognition and Quantification in Ferrography Images by Instance Segmentation
Published in Tribology Transactions, 2022
Kang Sun, Xinliang Liu, Guoning Chen, Jingqiu Wang
In the working process of mechanical equipment, friction and wear are unavoidable and may cause serious consequences and large economic loss (1). Ferrography is an effective method for wear condition monitoring and fault diagnosis of machines such as aero-engines and mining equipment (2). The wear conditions of the equipment can be determined by analyzing the wear debris in ferrography images. Hence, automatic identification of wear debris has become an important research direction of ferrography because it avoids subjective judgment, particularly by unexperienced analysts.