With these evaluation criteria, repairing compressors must be an extremely daunting task

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Some factories, seeing that maintenance workers often had nothing to do and spent their time drinking tea, smoking, or resting, felt dissatisfied; as a result, they tried to evaluate these workers based on the amount of work they completed, but this approach had the opposite effect. The equipment repaired by maintenance staff always leaves problems and side effects; new repair tasks keep arising, and the maintenance staff end up as busy as firefighters. As a result, the condition of the equipment worsens, and the production losses caused by downtime increase further. Therefore, how to evaluate maintenance performance becomes a complex and worthy of study issue. The system is like a ball: if one side is flattened, the other side will bulge out. Taylor said over 100 years ago that it is difficult for a system to make progress without metrics; it is very helpful for users to be aware of some key performance indicators, as these aid in evaluating and driving improvements in the management of equipment at compressor stations. 01 Equipment integrity rate: The equipment integrity rate is used most frequently among various indicators, but its role in facilitating management is limited. The so-called integrity rate refers to the ratio of devices in good condition to the total number of devices during inspections (Device integrity rate = Number of devices in good condition/Total number of devices). Many factories manage to achieve an integrity rate of over 95%. The reason is simple: at the time of inspection, if the equipment is running and not malfunctioning, it is considered to be in good condition, so this indicator shows a good value. If it looks good, that means there isn’t much room for improvement; it means nothing can be improved further, and it also means it’s difficult to make progress. To this end, many companies have proposed modifying the definition of this indicator; for example, they suggest conducting checks on the 8th, 18th, and 28th of each month, and using the average of the good rate values obtained from these checks as the good rate indicator for that month. This is of course better than checking once, but it still represents a good rate on a point-by-point basis. Later, it was proposed to use the number of productive hours divided by the total calendar working hours; the productive hours are equal to the total calendar working hours minus the total time spent on failures and their repairs. This indicator is much more realistic. Of course, there are again issues related to the increased workload in statistics and the accuracy of those statistics, as well as debates over whether to deduct costs when it comes to preventive maintenance. Whether the integrity rate is an effective indicator of equipment management depends on how it is applied; different people may have different opinions on this. 02 Failure rate of the equipment: This metric is easy to confuse, as there are two definitions for it. 1. If it refers to the failure frequency, then it is the ratio of the number of failures to the actual number of times the equipment was in operation (Failure frequency = Number of failures due to downtime / Actual number of operating hours of the equipment) ； 2. If it is the failure downtime rate, then it is the ratio of the time the equipment is down due to failures to the total time the equipment is actually in operation, including the time it is down due to failures (Failure Downtime Rate = Time down due to failures / (Total time in operation + Time down due to failures)). Clearly, the failure downtime rate can provide a more accurate reflection of the equipment’s condition. 03 Equipment availability: This is more commonly used in the West, while in China there are two different terms for it – planned time availability (planned time availability = actual working time/planned working time) and calendar time availability (calendar time availability = actual working time/calendar time). By definition, the availability rate as defined in the West is actually the calendar time utilization rate. Calendar time utilization reflects the full utilization level of the equipment; in other words, even for equipment that operates on a single shift basis, we calculate the calendar time based on 24 hours. Because whether the factory uses this equipment or not, it still consumes the company’s assets in the form of depreciation. The planned time utilization rate reflects the planned usage level of the equipment; in the case of single-shift operation, the planned time is 8 hours. 04 Mean Time Between Failures: Another way of referring to this is mean time without failure (Mean Time Between Failures for a device = total time it operated without failures during the statistical period / number of failures). It reflects the frequency of failures, that is, the health status of the equipment, in a complementary manner to the failure downtime rate. It is sufficient to use one of the two indicators; there is no need to measure something using related indicators. Another indicator reflecting maintenance efficiency is the Mean Time To Repair (MTTR) (Mean Time To Repair = total time spent on repairs during a statistical period / number of repairs), which measures the improvement in the efficiency of maintenance work. With the advancement of equipment technology, it is difficult to determine a fixed value for maintenance time due to factors such as the complexity of the equipment, the difficulty of repairs, the location of faults, the average skill level of maintenance technicians, and the age of the equipment. However, we can use these factors to assess its average performance and levels of improvement. 05 Overall Equipment Efficiency: As market competition becomes increasingly fierce, manufacturers need to maximize its utilization and improvement in order to achieve sustained high economic benefits. The production efficiency in the manufacturing workshop is of utmost importance; in some cases, it even becomes the decisive factor in whether a company can be profitable. However, in today’s manufacturing industry, production facilities that appear to be operating well are actually not functioning at their best; there is significant room for improvement in terms of the efficiency of both equipment and operators, which indirectly causes substantial losses for businesses. To address this issue, the international manufacturing industry introduced the concept of Overall Equipment Effectiveness (OEE). Overall Equipment Efficiency is known as OEE for short. Generally, each production equipment has its own theoretical capacity, and to achieve this theoretical capacity it is necessary to ensure that there are no disruptions or quality losses. It is a strict measure of the overall performance of a machine, indicating where time wastage occurs; the purpose of tracking various forms of time wastage is to facilitate improvements. OEE is an indicator that provides a comprehensive reflection of equipment efficiency; it is the product of time availability, performance availability, and quality rate. Just like a person, the time utilization rate represents the attendance rate; the performance utilization rate indicates whether one works hard after starting work and achieves the desired efficiency; the quality rate reflects the effectiveness of the work, showing whether mistakes are made frequently and whether tasks can be completed with both quality and quantity ensured. The simple formula for OEE is: Overall Equipment Effectiveness OEE = Output of qualified products / Theoretical output for the planned working time. 06 Fully Effective Productivity – the formula that reflects equipment efficiency most thoroughly, rather than OEE. True Effective Productivity TEEP = Output of qualified products / Theoretical output over calendar time; this indicator reflects various deficiencies in the systematic management of the equipment, including upstream and downstream impacts, effects related to the market and orders, imbalances in the equipment’s production capacity, and unreasonable scheduling arrangements. This indicator is usually very low, which doesn’t look good, but it is highly accurate. 07 In terms of maintenance and management, there are relevant indicators such as the first-time pass rate for maintenance quality, the rework rate, and the maintenance cost ratio. 1. The one-time pass rate for maintenance quality is measured as the number of times the equipment after maintenance meets the product quality standards during a single trial run, divided by the total number of maintenance sessions. It is worth examining whether the factory uses this indicator as a performance metric for the maintenance team. 2. The repair rate is the total number of repairs performed after equipment maintenance divided by the total number of maintenance sessions. This more accurately reflects the quality of maintenance. 3. There are many definitions and calculation methods for the maintenance cost ratio. One is the ratio of annual maintenance costs to the total annual output value; another is the ratio of annual maintenance costs to the total original value of assets for that year. Yet another is the ratio of annual maintenance costs to the total replacement cost of assets for that year, followed by the ratio of annual maintenance costs to the total net value of assets for that year. Finally, there is the ratio of annual maintenance costs to the total production costs for that year. The author believes that the last algorithm is more reliable. Even so, the magnitude of this repair cost rate figure does not tell us anything. Because equipment maintenance is a form of investment, and investment creates value and output. Insufficient investment and significant production losses affect output ； Of course, excessive investment is also not ideal; it is known as over-maintenance and represents a waste. Appropriate investment is ideal. Therefore, factories should explore and determine the optimal ratio of inputs. High production costs mean more orders and a greater workload, which in turn increases the load on the equipment and raises the need for maintenance. Making investments in the right proportions should be the goal that factories strive to achieve. With this benchmark in place, the further one deviates from this indicator, the less ideal it is. 08 Regarding spare parts management, there are many indicators; the spare parts inventory turnover rate (Spare parts inventory turnover rate = Monthly cost of spare parts used / Average monthly value of spare parts inventory) is a relatively representative indicator. It reflects the liquidity of spare parts. If a large amount of capital is tied up in inventory, it will be reflected in the turnover rate. Another indicator reflecting spare parts management is the spare parts capital ratio, which is the ratio of the total funds allocated to spare parts to the total original value of the company’s equipment. This value varies depending on whether the factory is located in a central city, whether the equipment is imported, and the extent of the losses caused by equipment downtime. If the daily downtime cost of the equipment is high, or if the failure poses serious risks to environmental pollution and human safety, and if the lead time for obtaining spare parts is long, then a higher inventory level of such spare parts is necessary; otherwise, the capital investment associated with these spare parts should be kept as low as possible. There is an indicator that goes unnoticed by many, but is extremely important in modern maintenance management: the intensity of maintenance training (intensity of maintenance training = hours of maintenance training / hours of actual maintenance work). This training covers topics such as specialized knowledge of equipment structure, maintenance techniques, professional ethics, and maintenance management. This indicator reflects the degree of emphasis and investment companies place on improving the skills of their maintenance personnel, and it also indirectly reflects the level of their maintenance technical capabilities. 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