Predictive maintenance analysis techniques

The use of vibration analysis is not restricted to predictive maintenance. This technique is useful for diagnostic applications as well. Vibration monitoring and analysis are the primary diagnostic tools for most mechanical systems that are used to manufacture products. When used properly, vibration data provide the means to maintain optimum operating conditions and efficiency of critical plant systems. Vibration analysis can be used to evaluate fluid flow through pipes or vessels, to detect leaks, and to perform a variety of non-destmctive testing functions that improve the reliability and performance of critical plant systems. 

The fact that vibration profiles can be obtained for all machinery having rotating or moving elements allows vibration-based analysis techniques to be used for predictive maintenance. Vibration analysis is one of several predictive maintenance techniques used to monitor and analyze critical machines, equipment, and systems in a typical plant. However, as indicated before, the use of vibration analysis to monitor rotating machinery to detect budding problems and to head off catastrophic failure is the dominant predictive maintenance technique used with maintenance management programs. 

It is important for predictive maintenance programs using vibration analysis to have accurate, repeatable data. In addition to the type and quality of the transducer, three key parameters affect data quality the point of measurement, orientation, and transducer-mounting techniques. 

Motion of fluids in which local velocities and pressures fluctuate irregularly, in a random manner. Predictive maintenance technique that uses principles similar to those of vibration analysis to monitor the noise generated by plant machinery or systems to determine their actual operating condition. Ultrasonics is used to monitor the higher frequencies (i.e., ultrasound) that range between 20,000 Hertz and 100 kiloHertz. 

Vibration analysis is the dominant technique used for predictive maintenance management. Since the greatest population of typical plant equipment is mechanical, this technique has the widest application and benefits in a total plant program. This technique uses the noise or vibration created by mechanical equipment and in some cases by plant systems to determine their actual condition. 

Most vibration-based predictive maintenance programs use some form of signature analysis in their program. However, the majority of these programs rely on comparative analysis rather than full root-cause techniques. This... 

Spectrographic analysis allows accurate, rapid measurements of many of the elements present in lubricating oil. These elements are generally classified as wear metals, contaminates, or additives. Some elements can be listed in more than one of these classifications. Standard lubricating oil analysis does not attempt to determine the specific failure modes of developing machine-train problems. Therefore, additional techniques must be used as part of a comprehensive predictive maintenance program. 

This predictive maintenance technique uses principles similar to vibration analysis. Both monitor the noise generated by plant machinery or systems to determine their actual operating condition. 

The microprocessor should also be able to support modem communication with remote computers. This feature will enable multiple plant operation and direct access to third party diagnostic and analysis support. Data can be transferred anywhere in the world using this technique. Not all predictive maintenance systems use a true RS 232 communications protocol or support modem communications. These systems can severely limit the capabilities of your program. The various predictive maintenance techniques will add other specifications for an acceptable data acquisition unit. 

The optimum predictive maintenance program developed in earlier chapters is predicated on vibration analysis as the principle technique for the program. It is also the most sensitive to problems created by the use of the wrong transducer or mounting technique. 

Ferrography is a technique that provides microscopic examination and analysis of particles separated from fluids. Developed in the early 1970s as a predictive maintenance technique, it was initially used to precipitate ferrous wear particles from lubricating oils magnetically. This technique was used successfully to monitor the condition of military aircraft engines. That success has led to the development of other applications, including testing of fluids used in vacuum pumps within the semiconductor industry. 

Once identified the basic events analyzed for the occurrence of deviation (as an example no flow), it can observe that the basic events correspond to the failure mode of a component for that reason the FMEA technique is applied in order to identify the causes of failure that lead to the occurrence failure mode and consecutively select maintenance policies. As an example, the failure modes and effects analysis for the Electric Motor A.C. considering the failure Motor A.C. won t start is shown in Table 5. Those systems are submitted, according to manufacturer s recommendation, to a detailed maintenance policy based on predictive or preventive techniques. 

Perhaps the most commonly used spectrometric method for analysis of viscous oils is infrared spectroscopy. General instructions for qualitative hydrocarbon type and functional group analysis are widely available. Papers have also been published for quantitative analysis of hydrocarbon types [/O]. FT-IR techniques have been reported for use in predictive maintenance programs to monitor the concentration of additives and degradation products in used oils [11 ]. 

Predictive maintenance or Condition Monitoring (CM) uses primarily non-intmsive testing techniques, visual inspections and performance data to assess equipment condition. It replaces arbitrarily timed maintenance tasks with maintenance scheduled only when warranted by equipment condition. Continuous analysis of equipment condition monitoring data allows planning and scheduling of maintenance or repairs in advance of catastrophic and functional failure. 

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