Plant Condition Monitoring and Predictive Maintenance

Nowhere are the risks of failures and shutdowns more critical than in the nuclear power generation industry. Therefore, nuclear power plants have come to be the facilities that conduct the most comprehensive predictive maintenance programs using IR thermography. However, the applications within these programs are typical to almost all plants and facilities. 

Condition monitoring problem indications are known as findings because unusual heating conditions can be caused by normal events other than failure mechanisms. Findings must therefore be accompanied by other condition information before they can be validated as incipient problems. Findings fall into three broad categories electrical, mechanical, and miscellaneous. 

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Chapter 7 Plant Condition Monitoring and Predictive Maintenance Chapter 8 Buildings and Infrastructure... 

As an example of the importance of process parameters monitoring, consider a process pump that may be critical to plant operation. Vibration-based predictive maintenance will provide the mechanical condition of the pump and infrared imaging will provide the condition of the electric motor and bearings. Neither provides any indication of the operating efficiency of the pump. Therefore, the pump can be operating at less than 50 per cent efficiency and the predictive maintenance program would not detect the problem. 

Implementation Routes and timing are established, people are trained, and the program is implemented. Readings are taken, analyses are performed, and recommendations for action are provided to maintenance, engineering, and operations. A strict condition-monitoring discipline will lead a plant to a successful predictive maintenance environment where people at all levels of a plant will be able to visualize the resultant equipment saves. ... 

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. 

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. 

Thermography is a predictive maintenance technique that can be used to monitor the condition of plant machinery, structures and systems. It uses instrumentation designed to monitor the emission of infrared energy, i.e. temperature, to determine their operating condition. By detecting thermal anomalies, i.e. areas that are hotter or colder than they should be, an experienced surveyor can locate and define incipient problems within the plant. 

Alert and alarm limits The microprocessor should include the ability to automatically alert the user to changes in machine, equipment or system condition. Most of the predictive maintenance techniques rely on a change in the operating condition of plant equipment to identify an incipient problem. Therefore, the system should be able to analyze data and report any change in the monitoring parameters that were established as part of the database development. 

The purpose of predictive maintenance is to minimize unscheduled equipment failures, maintenance costs and lost production. It is also intended to improve the production efficiency and product quality in the plant. This is accomplished by regular monitoring of the mechanical condition, machine and process efficiencies and other parameters that define the operating condition of the plant. Using the data acquired from critical plant equipment, incipient problems are identified and corrective actions taken to improve the reliability, availability and productivity of the plant. 

The labor-intensive part of predictive maintenance management is complete. A viable program has been established, the database is complete and you have begun to monitor the operating condition of your critical plant equipment. Now what ... 

The second type of prognosis is for situations where a failure is catastrophic (e.g., in nuclear power plants). It is desirable to predict the probability that a machine operates without failure up to some future time (e.g., next inspection interval), given the current machine condition and past operation profile. Actually, in any situation, the probability that a machine operates without failure until next inspection (or condition monitoring) interval is a good reference for maintenance persoimel to decide whether or not the inspection interval is appropriate. 

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