Acoustic Emission and Vibration - Essay Example

? Acoustic Emission and Vibration By of Learning: Acoustic Emission and Vibration Introduction Both acoustic emission and vibration sensors have been applied in the development of several monitoring systems that have been conditioned due to their early detection application when it comes to faults arising due to important machinery components. The process of early detection has proved to be a very crucial factor in condition monitoring as well as serving as a basic extended CBM component (Zamada and Masuda, 1999, p. 160). Though the two sensors are effectively applied in this process, there exist several differences in their applications as well as a number of advantages and disadvantages over each other. The acoustic emission normally abbreviated as AE refers to sound waves that are normally produced in the event that a material is subjected to stress due to internal changes and external forces. A good example of this phenomenon is the mechanical loading which generates elastic wave’s sources (Lokajicek and Sikula, 1996, p. 312). Over the years, acoustic emission has steadily replaced the use of vibration techniques that were used traditionally. This transformation is closely associated with the better working conditions witnessed while working with acoustic emission. Vibration sensing has been associated with a number of mechanical conditions such as processes that result in energy loses like friction and impacts, machinery deteriorates, and frequencies that come in a broad range. Acoustic emission on the other hand makes use of much higher frequencies when it comes to vibration movements that are synchronous. By using such frequencies, this technique makes it possible to detect signal parts experiencing high signals and also allows the detections of miniscule activities that come in large amounts like brief impacts, slight rubs or crushing of single lubricant particles. This means that acoustic emission technique is in apposition to detect failures that are impending before they take place and goes further to monitor their progress afterwards (Mori, Saruhashi and Mogi, 1994, p. 375). Though vibration analysis has been in operation for many years, it is associated with a number of disadvantages including its knowledge levels that are unsustainable and its requirements being costly while trying to achieve a good diagnosis. The above setbacks make vibration analysis valuable but overly complicated compared to acoustic emission. Acoustic emission offers detecting warnings early enough on small defects and wear while vibration sensing has to wait until a defect occurs before it detects it. Acoustic emission technique also picks up more information as compared to vibration sensing. Some of the additional information picked up by acoustic emission include; friction, lubrication and cracking. Vibration sensing is in no position to pick up such information. Despite this realization, it is evident that the total information that can be picked by acoustic emission is limited as compared to that obtained by vibration analysis (Mori and Obata, 1998, p. 340). The Differences between Acoustic Emission Sensor and Vibration Sensor The acoustic emission signal processing is complicated in such a way that it cannot be conducted by every individual due to its high frequency signal. It calls for expertise in the interpretation of the oscilloscope’s squiggly lines. This technique allows machines to be run continuously, slowly, for a duration that is short and to be operated intermittently. Acoustic emission also permits for problem diagnosis on machines to be carried out in its early stages, gives room for maintenance procedures and allows for the monitoring of the improvement. By allowing such procedures and process, the technique provides early information that is real time on faults applicability and sensitivity to a broad speed rotational (Simpson, 1991). Contrary to vibration sensing, acoustic emission is designed in such a way that even users with little knowledge on the subject can easily check major conditions concerning slideways and bearings. This is close to impossible when it comes to vibration analysis. Vibration analysis usually takes on ships using third party consultants from outside. Acoustic emission on the other hand makes use of an out of box engineer who by the time the shift is completed, all assessments will be accurately accomplished on room pumps, generator bearings, turbine, and rings on crane slewing. Measurements taken during vibration sensing often require a lot of analysis, sampling, diagnostics contrary to the measurements taken during acoustic emission which is simpler (Brunet, 2000, p. 82). Advantage of Acoustic Emission Analysis over Vibration Analysis Putting into consideration the ISO standards, vibration techniques such as vibration analysis and vibration monitoring are widely used but complicated and need sophisticated understanding and knowledge. This is contrary to acoustic emission technique which has been simplified through having the vibration power technique being placed directly into the engineer’s hands. This allows signals to be easily processed using acoustic emission sensors in a form that is easily understandable (Hill and El-Dardiry, 1998, p. 675). Despite the several advantages of acoustic emission analysis over the vibration analysis, the AE analysis has been associated with a number of disadvantages in comparison to vibration analysis. One of the disadvantages of this type of analysis is its limitations in its approximation, as it can only estimate the qualitative damage levels to the extent of how much and for how long. Therefore, the need arises for other analysis method like the vibration analysis in order to determine the quantitative results (APC, 2004, p. 24). The operation environments for acoustic analysis are often noisy compared to vibration analysis environment, and its signals have been observed as being weak and making signal discrimination to be almost impossible. This process is very crucial for any analysis to be successful. This makes its results less reliable compared to those of vibration analysis (Skylink, 2009, p. 12). In addition to its unsustainable knowledge levels and high cost, vibration sensing frequencies depend critically on the on the geometry, components of the machines, and precise operating speed. Acoustic emission on the other hand has several advantages over vibration sensing. In addition to offering early detection warnings on defects and wear, it picks up some information which vibration analysis cannot like cracking, friction and vibration. This makes acoustic sensing more reliable as compared to vibration analysis. In addition, it requires less expertise thus can be generally used by maintenance staff. Conclusion Acoustic emission should not be viewed as a technique introduced to invalidate vibration technique. All it does is advance on the technique already established by vibration analysis so as to make the assessing process cheaper, simpler and convenient. Vibration and acoustic sensors have been very useful in monitoring systems development because of their ability to detect faults, which is an important process in machinery components. Despite the same applications, the two sensors make use of different technologies depending on where they are applied. While the acoustic sensors applications are more stationery, the vibration sensors are mostly used on moving parts. The acoustic analysis has proved to be more advantageous as compared to the vibration analysis. Acoustic analyses are able to detect faults early enough before they occur, they are cost effective, and their process is simple. However, the same sensors are challenged due to their weak signal discrimination (Gautschi, 2002, p. 45). Despite the fact that acoustic emission has been regarded as being a simpler process, its signal which comes in high frequencies requires special skills thus making the process complicated. This disadvantages the technique as simplicity was one of the factors that gave it an age over vibration analysis. However, recent developments have enabled the introduction of sensor level processing that has made the process simple and convenient to be used by any individual. This makes acoustic emission technique to be deskilled effectively thus allowing broader application use. Reference list APC, 2004. 12FT Netbotz Vibration-Sensor. Springer- Verlag: New York. Brunet et al., 2000. Increase in performances of focused microacoustic sensors by couplant adjustment. Eur. Phys. J. AP, 9, pp 81-85. Gautschi, G., 2002. Piezoelectric Sensorics. Springer Berlin: New York Hill, R. & El-Dardiry, M., 1998. A theory for optimization in the use of acoustic emission transducers. J. Acoust. Soc. Am, 67, pp. 673-682. Lokajicek, T. and Sikula, J., 1996. Acoustic emission and electromagnetic effects in rocks. Progress in Acoustic Emission VIII, pp. 311-314. Mori, Y and Obata, Y., 1998. Acoustic emission and electric potential changes of rock samples under cyclic loading. Progress in Acoustic Emission IX, pp.134-178. Mori, Y., Saruhashi, K. and Mogi, K., 1994. Acoustic emission from rock specimen under cyclic loading. Progress in Acoustic Emission VII, pp.173-178. Simpson, G., 1991. Ultrasonic Methods of Non-Destructive Testing. Springer- Verlag: New York. Skylink, 2009. Skylink VS-433W Vibration Sensor. Springer Berlin: New York Zamada, K. and Masuda, H., 1999. Electromagnetic and acoustic emission associated with rock fracture. Phys. Earth. 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