Equipment inspection and condition-based maintenance

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The main tasks of equipment operation management include equipment inspection, defect management, and equipment maintenance. Improve the rate of defect detection and the accuracy of judgment during equipment inspections, enhance the management of equipment defects, keep track of the operating status of equipment in a timely manner, ensure its safe operation, provide reliable basis for condition-based maintenance, and adhere to the principle of repairing equipment only when necessary and ensuring that repairs are done properly. I. Equipment Inspection
During equipment operation, inspectors are required to conduct inspections in accordance with the prescribed inspection standards, contents, operating parameters, and inspection intervals. Under special circumstances—such as extreme weather conditions (high temperatures, thunderstorms, strong winds, snow and ice), full-load operation, power supply reliability operations, operation of equipment with existing faults, or equipment being put back into service after major repairs—inspections should be intensified as appropriate. Particular attention should be paid to key inspection points. Inspectors must be familiar with the normal operating parameter ranges and technical standards of the equipment, and they are required to keep detailed records of all inspection activities. 　　 These long-term accumulated equipment inspection data serve as the basis for equipment managers to conduct comprehensive analysis, diagnosis, and assessment of the equipment’s health status; they are the prerequisite and foundation for condition-based maintenance of equipment – and this is the true core of equipment inspection. II. Development Process of Equipment Maintenance The development of equipment maintenance has gone through the following three stages: Stage 1: From the Industrial Revolution to before World War II. Due to the large design margins and simple functionality of most devices, they have high reliability and are easy to repair. Therefore, the requirement for maintenance is to repair it only after it breaks down, that is, to carry out post-maintenance, also known as emergency maintenance. 　　 Phase Two: After World War II to the 1970s. Post-maintenance repairs result in excessive downtime, affecting production efficiency; it became apparent that it was necessary to prevent equipment failures, which led to the development of the concept of planned and preventive maintenance centered around regular inspections. This maintenance approach reduces downtime due to failures, eliminates potential problems at an early stage, and decreases the randomness of some maintenance tasks. However, the economic considerations are insufficient, which may still lead to either excessive or inadequate maintenance. 　　 Third phase: 1970s to the present. As equipment becomes more complex, automated, and valuable, maintenance costs rise sharply; as a result, preventive maintenance and maintenance based on equipment reliability are increasingly adopted. Its maintenance characteristic is the implementation of reliability-centered maintenance, supplemented by predictive maintenance or condition-based maintenance. The main strategies employed for equipment maintenance are as follows: fault-based maintenance strategy, scheduled maintenance strategy, and condition-based maintenance strategy. 　　 1. Fault repair 　　 Fault repair is generally carried out after a fault occurs, that is, it is repair done ex post facto. Its greatest advantage is that it makes full use of the lifespan of components or system parts, but routine maintenance is unplanned, resulting in wasted spare repair resources; at the same time, it has certain defects and shortcomings. 　　 2. Regular maintenance 　　 Regular maintenance is a time-based preventive maintenance approach in which the level of maintenance, maintenance intervals, and specific tasks to be carried out are determined in advance, based on the patterns of the equipment’s lifecycle. 　　 3. Condition-based maintenance 　　 Condition-based maintenance is a type of preventive maintenance that relies on the condition of the equipment. It utilizes condition monitoring and diagnostic techniques to obtain information regarding the equipment’s condition, assess its status, and determine in advance the timing of maintenance, the level of maintenance required, as well as the specific tasks to be carried out. III. Technical requirements for condition-based maintenance of equipment 　　 The premise of condition-based maintenance is to conduct a condition analysis and assessment of the equipment, in order to determine what state the equipment is in at present, whether there are any potential faults, what the rate of change of fault-related parameters is, how long the fault development period will last, and how to predict the trend of fault development. The technologies for condition-based maintenance include condition monitoring technology, condition prediction technology, and equipment maintenance decision-making. 　　 1. Equipment condition monitoring: For various failure modes of equipment, appropriate technical methods are employed to monitor its condition information, extract data that reflects the characteristics of its status, identify existing and impending defects, and analyze and predict the timing for maintenance, thereby effectively reducing equipment damage. Equipment condition monitoring can be divided into three basic steps: data acquisition, data analysis and feature extraction, and fault diagnosis and evaluation. 2. Equipment condition prediction 　　 Commonly used methods in prediction include time series analysis, regression analysis, fuzzy prediction, grey prediction, artificial neural network methods, etc. 　　 3. Equipment status assessment: A technical method that employs techniques for predicting the development trends of equipment status, with the aim of improving equipment reliability and availability. The current condition of the equipment is determined after evaluation; therefore, the condition assessment of the equipment serves as the basis for carrying out condition-based maintenance. 　　 Condition-based maintenance encompasses three meanings: equipment condition monitoring, equipment condition prediction, and equipment condition assessment. Equipment condition monitoring is the foundation of condition-based maintenance. Equipment condition prediction relies on this monitoring; by integrating historical equipment data and utilizing technologies such as neural networks and expert systems, it is possible to determine the health status of equipment, make accurate assessments of its condition, and ultimately make maintenance decisions. IV. Solutions for Condition-Based Maintenance of Equipment 1. Equipment Inspection 　　 During the operation of equipment, inspections are carried out in accordance with the specified inspection contents and intervals for different types of equipment. Detailed records of these inspections are kept. Inspections are intensified as appropriate in cases of adverse weather conditions, during full-load operation, or after major repairs when the equipment is put back into service. Special attention is paid to the key aspects of equipment inspection; inspectors are required to be proficient in using the equipment used for inspections and to know the normal operating ranges of the equipment. This provides equipment managers with a basis for comprehensive analysis and diagnosis, as well as for conducting routine or diagnostic tests. 　　 2. Periodic adjustment of equipment status 　　 For the live testing items carried out while the equipment is in operation, if it is confirmed that the accuracy of the displayed values is sufficient to reflect the normal condition of the equipment and that the real-time data indicate good equipment status, then routine tests can be extended or waived, regardless of whether the scheduled inspection time has arrived. If abnormalities are detected during live equipment inspections or routine checks, or if the equipment has been subjected to severe adverse operating conditions that could threaten its safe operation, the equipment manager will decide whether it is necessary to shut down the equipment for diagnostic tests or include such tests in the regular maintenance schedule. In severe cases, the equipment will be overhauled; if overhauling is not feasible, it will be replaced. 　　 3. Evaluation and handling principles for condition parameters
When condition parameters reach the warning values, it indicates that there may be or could develop some defect in the equipment. Devices that are in operation should be monitored continuously, and the device managers should be informed promptly ； For equipment that has been shut down, it is generally not advisable to put it back into operation until it is confirmed that there are no major defects. When the status value exceeds the warning limit, it is necessary to arrange for the equipment to be shut down as soon as possible in order to conduct diagnostic tests or repairs, and the equipment manager should be informed promptly; the equipment should not be put back into operation until the potential hazards have been eliminated. Under similar operating and testing conditions, the same state parameters of identical equipment should not show significant differences; otherwise, it should be taken as a matter of concern. 　　 4. Routine maintenance and testing plans 　　 Routine maintenance and testing plans are formulated based on the principles of equipment inspection and evaluation of operational conditions, rather than being carried out merely on a fixed schedule. Normally, make preparations for maintenance and testing, as well as conduct equipment analysis. Whenever there is a power outage, make full use of that time to carry out equipment maintenance and testing. 　　 5. Statistical analysis of equipment operation status 　　 Conduct statistical analysis on the equipment’s status to accurately understand its condition. Currently, online monitoring technologies are not yet mature enough. It is necessary to make full use of established online and offline monitoring devices and techniques, such as infrared thermal imaging and gas chromatography analysis of transformer oil, to test the equipment in order to analyze its condition. V. Conclusions 　　 1. An objective evaluation of condition-based maintenance 　　 The core of condition-based maintenance management lies in formulating economical and reasonable maintenance and testing plans based on the results of equipment condition assessments. The purpose of equipment maintenance is to eliminate defects in the equipment through maintenance, ensuring its stable and reliable operation throughout the maintenance period. Condition-based maintenance can reduce the randomness of maintenance work, significantly cut down maintenance time, and improve equipment availability. 　　 2. Correct understanding of condition-based maintenance 　　 Condition-based maintenance is a complex, long-term, challenging, and scientific process that requires scientific management to support it, as well as appropriate testing and inspection techniques to ensure its effectiveness. However, there are still many weaknesses in current production technology management; basic management fails to provide complete equipment documentation as well as records of operation, maintenance, and testing. 　　 3. Key issues to be addressed 　　 The application of condition-based maintenance must be based on comprehensive condition monitoring of the equipment. Currently, the online monitoring systems for equipment status still have some issues, such as a limited number of monitoring points, single functions, a lack of systematicness and comprehensiveness, and especially a lack of hierarchical and networked monitoring, which hinders the consolidation and integration of equipment status information. There are still many issues to be resolved regarding how to establish accurate equipment reliability models and develop equipment failure diagnosis expert systems with practical value.