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A Brief Discussion on Proactive Prediction in Equipment Maintenance

2007-12-24View Original

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At present, the equipment maintenance management in most economic entities generally remains at the level of preventive maintenance only. However, in the face of a rapidly changing market, how to produce more varieties of products that meet quality standards within a specified time while keeping costs at their lowest to maximize profits is an issue that management should pay close attention to. To ensure uninterrupted and safe operation, it is necessary to guarantee the normal, safe, and efficient functioning of machinery. This requires proactive real-time monitoring, which enables the prediction of potential failures and their occurrence times based on various operational parameters of the machinery, before any failure actually happens. By anticipating time-dependent failures in equipment, maintenance strategies can be adjusted accordingly. Equipment predictive maintenance technology has evolved from condition monitoring and fault analysis; it is a key technology that enables the refinement and extension of time-based preventive maintenance through advanced predictive methods. Predictive maintenance of equipment focuses on dynamic management and sustainability, and it requires the involvement of all employees; it cannot be achieved solely by the equipment management department. However, the equipment management department must play an organizational role, such as supervising and inspecting the equipment inspection processes, utilizing data from the equipment database along with new technologies and processes to improve the current condition of the equipment, adjusting the methods of equipment maintenance, and organizing and overseeing the implementation of maintenance plans to ensure dynamic management. 1. Through equipment FMEA analysis, it was determined that there are three basic maintenance methods: preventive maintenance (including routine maintenance and condition-based maintenance), corrective maintenance, and reactive maintenance. For each failure mode of the equipment, its occurrence frequency O, severity S, and detectability D are examined; these three factors are then combined to determine the Risk Priority Number (RPN). The maintenance method to be used for the equipment is decided based on the failure frequency, severity, detectability, and RPN. Failure occurrence frequency O: Based on the equipment operation and maintenance records, the frequency of each type of failure is determined, with numbers being used to indicate the level of that frequency. For new equipment, experienced personnel can determine the frequency of failures. Severity S): Severity is used to assess the extent to which each type of fault affects the normal operation of the equipment; it is expressed as a number that indicates the level of impact, with lower scores indicating less impact. Detectability D: refers to the probability that a fault is detected before it occurs. Detectability can apply either to the causes of failures or to the failure modes themselves. If a failure has a long period of early warning before it occurs, its probability of being detected is high; if a failure can be detected using simple methods, its probability of detection is also high. To increase the likelihood of early detection of failures, sensors, alarms, and other devices can be installed on equipment, with numbers again being used to indicate the level of probability of detecting such failures. Risk Priority Number RPN: The risk priority RPN is obtained by multiplying the three scores for failure frequency, severity, and detectability: RPN = O × S × D ; RPN has no meaning on its own; it is simply used to indicate the level of risk associated with a fault. The ideal value for RPN is 1; at this level, the risk of failure is minimal, and no corrective or preventive actions are required ; As RPN increases, the risk of failure also increases, and it becomes more necessary to take corresponding corrective actions at this point. Regarding the method for determining the RPN threshold, it is recommended to use the \"95% confidence\" rule: multiply the maximum possible RPN value by (1–0.95) to obtain the RPN threshold. According to the 1–4 grading scale, the RPN value is: 4×4×4(1—0.95), which is approximately equal to 3. In other words, if the RPN for a particular fault is greater than 3, then corresponding corrective actions need to be taken. Another common method for determining the RPN threshold is to apply Pareto’s 80/20 rule: approximately 80% of the risks are caused by the top 20% of RPN values, so it is necessary to focus on taking corrective actions against the faults that result in the highest 20% of RPN values. Select the maintenance method for the equipment: Determine which maintenance method to use based on the failure frequency, severity, detectability, and risk priority number RPN mentioned earlier. 2. Develop management plans for the corrective actions to be taken for each type of fault, the frequency of implementing these actions, and the main personnel responsible for the repairs. 3. Based on the data in the equipment database, the equipment maintenance methods are adjusted through the analysis of potential failure modes and their consequences for key equipment. Sustainability: 1) Assessing the modified preventive maintenance approach based on target values, including the importance of the equipment, maintenance tasks, causes of failures, degree of impact, failure rate before improvements, the original preventive maintenance plan, current predictive maintenance measures, time required to implement these measures, failure rate after improvements, the modified preventive maintenance approach, as well as evaluating and calculating the lifecycle of critical equipment spare parts and their optimal inventory levels. 2) When the target value cannot be achieved, improvement measures should be proposed, including using the equipment FMEA approach and conducting failure consequence analysis to determine a new equipment FMEA approach. 3) When the target value is achieved, new target values are set based on the review reports, including equipment condition assessment and improvement reports. As preventive maintenance becomes a common method for extending the lifespan of components in routine maintenance, predictive maintenance builds upon this by adding the capability to monitor the condition of key components, thereby enabling the prediction and avoidance of unnecessary downtime. 4. The equipment management department is also responsible for carrying out preventive/condition-based maintenance, as well as accurate data storage and calculation, in order to continuously improve various equipment metrics based on the collected data. It is important to effectively integrate these data with each other from a technical perspective into the equipment maintenance management system. 5. On the basis of establishing a equipment maintenance mechanism, integrate the contents and standards of maintenance into equipment management activities, so that maintenance work is carried out in a quality-driven, quantifiable, tangible, and effective manner, ensuring that equipment maintenance is conducted on a regular basis.

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