07+2丨丨B丨Article number丨1004*7913(2002)08― The meaning of 2T1Q status maintenance cade*Jo legalElectronicPublish! Reasons and techniques for timely forecasting. ; <1. 1 Problems in the regular overhaul of power main equipment China's power companies have long implemented a unified national regular maintenance system, and its essential characteristics are based solely on the time period. This model clearly has the following problems.

a does not consider the actual condition of the equipment. All pre-specified maintenance cycles are carried out, and over-examination and under-repair are coexisting. The result of the execution is a large amount of inaction and financial loss. Insufficient maintenance is the enemy of equipment safety, and it is the root cause of major malignant accidents such as steam turbine overspeed and boiler explosion.

b. The targetedness during the overhaul process is not strong. Mastering the state of the equipment is not enough, and the key points cannot be highlighted during maintenance.

c The current maintenance cycle does not meet the failure law of the existing equipment life. A large number of equipment statistics at home and abroad show that the failure rate curve of any equipment over its lifetime is a bathtub-like curve. It is unscientific to perform the same periodic overhaul throughout the life of the equipment, which does not meet the objective actual conditions of the equipment.

d often produces a "negative effect." At present, the main overhaul is over-maintenance. Over-maintenance repairs damage some equipment that is good at the end, and also increases the probability of misoperation, accidental touch, and incorrect wiring.

The consistent approach. How to make the prevention work more in line with the objective law, more targeted implementation, through years of practice, the equipment maintenance has been planned to overhaul the "expired compulsory repair, repair must be repaired" understanding, mentioning the establishment and implementation of the state overhaul system Schedule.

2 State maintenance status inspection is based on the equipment status evaluation, according to the equipment status and analysis and diagnosis results, the maintenance time and project are arranged, and the maintenance method is actively implemented.

2.2 The advantages of state maintenance can save costs and extend the service life of equipment. The state maintenance can prevent over-maintenance, that is, over-maintenance and waste when the machine is normal; it will also prevent insufficient maintenance, that is, equipment failure will be caused when the repair is not overhauled, material consumption is reduced, maintenance work is reduced, and human error can be avoided. .

It can provide intelligence to the operating personnel in a timely manner, adjust the operating conditions, and improve the economic operation and safe operation level.

It can improve equipment reliability and availability, increase power generation, and improve economic efficiency.

2.3 Reliability of State Maintenance The establishment and completion of the data foundation must have a complete set of data, including at least frequency data, reliability data, and consequence data. Over the years, reliability management and various supervision and testing have stored a fairly complete set of records like medical records for each device. Such a data base obviously plays a very important role.

The technical support of the state-based maintenance is based on fault diagnosis technology and online monitoring technology.

In recent years, equipment condition monitoring and fault diagnosis technology has achieved unprecedented rapid development at home and abroad. This technology refers to the use of various types of sensors, etc., in the operation of the equipment or without disassembly, to grasp the internal conditions, to determine the location of the fault and to sum up, the technical basis of the state overhaul has been formed and is Consolidated.

3 Reliability Analysis of State Maintenance 3.13 Maintenance Mode Comparison Model Establishment An ideal state is to assume that the system can be restored to the initial state after each inspection, and the reliability is considered as new. The following three indicators are used to compare the three maintenance methods, namely reliability, availability and cost.

Reliability model After-sales maintenance reliability: Foresight inspection is foreseeable to be repaired when a fault occurs, and its occurrence time and probability are basically the same as after-the-fact maintenance.

(ra)-Average working time+Average repair time After-the-fact overhaul: Let Tf be the average after-sales inspection time for after-sales repair after failure, then A1) = Preventive maintenance: The average cost of preventive maintenance unit time is C2, and Cp is average after-sales maintenance For the cost, the average cost of the maintenance unit is expected to be C3, and Ci is the average foreseeable maintenance cost. The comparison of the 3.23 types of maintenance methods first determines the fault probability density function of the equipment. Different distribution functions draw different conclusions, which are common in power equipment. There are two kinds of distribution: exponential distribution and Weibull distribution. Take the exponential distribution as an example: fOe-in (1) = reliability of -3 types of maintenance methods: after-the-fact overhaul: *((()=e preventive maintenance: R2()-dt This indicates that the maintenance work has the same starting point, that is, equipment failure There are defects in the design and manufacturing process, or there are unforeseen abnormal stresses. The maintenance work should be improved on the basis of this understanding.

Availability of 3 types of maintenance methods: After-the-fact overhaul: Foresight overhaul: Let Ti be the average foreseeable inspection time, then preventive maintenance: maintenance costs such as repair, replacement parts, working hours, materials, power loss, state inspection fees, etc. It is advisable to compare the average cost per unit time indicator.

After-sales maintenance unit time average cost C (, let Cf be averaged. After-the-fact maintenance costs, q then a ~ 1999 Tongliao Power Plant 200MW unit 14 times overhaul, the average overhaul interval 2. 85a interval is the longest for the 4th unit ~3 times of overhaul interval is 291a; the interval is the 2nd to 3rd overhaul of Unit 3, the interval is 2.73a. The overhaul interval is 100% close to 3a. The specific overhaul interval is shown in Table 1. Because the state maintenance time Ti is definitely better than afterwards The inspection time is short, that is: - 1999, 200MW coal-fired unit overhaul interval unit statistical station overhaul interval / a average 1-2 times between 2-3 times between 3-4 times between the No. 1 42 state maintenance available The rate is the largest, followed by after-the-fact maintenance, and the planned availability is the smallest.

Comparison of the unit time and cost of the three types of maintenance methods: As shown in Table 1, the overhaul interval of Tongliao Power Plant strictly followed the planned overhaul interval specified in the 1950s, and did not take state maintenance according to the actual conditions of the equipment. For example, in the overhaul of Unit 3 in 1995, at least the overhaul interval can be extended by more than 1a from the perspective of state maintenance.

Because Unit 3 completed 94.80% of the EAF in 1994, the unplanned outage only occurred once. In the 4 months before the overhaul in 1995, the EAF completed 100%, and there was no equipment hazard. It was only after the regular inspection time and the downtime was overhauled. If the overhaul period is extended from 3a to 4a, then each unit of 12a will be reduced by 1 major overhaul. 4 units will be reduced by 4 times for overhaul, and the average overhaul will be reduced by 3 times per 3a, which not only reduces the workload of workers, but also saves overhaul standards every time. The project cost is about 2.5 million yuan. Moreover, the number of operating hours of the unit was increased, and the power generation was 248.28 million kW*h, and the profit was 42.19 million yuan. A total of 2 items can save a total of 44.69 million yuan. If the overhaul period is calculated by 55d, the equivalent availability coefficient can be increased by 1507%, which improves the availability and reliability of the unit.

4.2 Operation reliability before and after overhaul of the unit - Analysis of the 13 overhaul conditions of the 200MW coal-fired unit in 1998, we can see the change of the unit's operational reliability index, see Table 2. After the overhaul of the unit, the reliability of most units is improved, but there are also Some unit reliability has been reduced. a. Reliability improvement of the unit after overhaul In the 13 major overhauls in 1985-1998, the equivalent available coefficient has a certain improvement after 8 major repairs, one year before the overhaul, and the equivalent available coefficient is 88.31%. It rose to an average of 94.08%, an increase of 5.77%; the number of unplanned outages decreased by 8 times, from 6.25 times/year in the year before the repair to 3.5 times/year in the year after the repair; The transportation time has dropped 8 times, from 416.84h/year in the year before the repair, to the general level, the after-sales inspection should be eliminated. It is almost considered that CCCi will not be in the early stage of improving the state inspection level. The general trend is that the state maintenance cost is less than after-the-fact maintenance.

It can be seen that for the case of exponential distribution, it is not necessary to plan maintenance, not only to improve the reliability of equipment, but to reduce the availability of equipment and increase the maintenance cost.

4 Tongliao Power Plant General Factory Overhaul Casebook5 Since the 200 MW units of Tongliao Power Plant have been put into production, the average annual overhaul unit accounts for about 1/3 of the in-service units. The overhaul interval of this type of unit and the reliability of the unit after overhaul are important for power production. Impact. According to the statistical data from 14a, the actual situation of the overhaul interval of this type of unit and the reliability of the unit after overhaul is analyzed, and the scientific condition of the state maintenance is put forward.

1 Overhaul interval table 2 200MW unit before and after overhaul operation reliability index unit equivalent availability coefficient (pre/post) comparison poor unplanned outage times (pre/post) comparison time (pre/post Wh comparison difference equivalent forced outage Rate / No.1, No.2, No.3, No.4, one year after the repair of 118.45h/year, the equivalent forced outage rate decreased in 9 times, from 609% before the repair to 238%. b. After the overhaul The reliability of the unit was reduced. In the 1985-1998 period, there were 5 times in the overhaul, and the equivalent available coefficient was reduced in the year before the major repair. According to statistics, the average available coefficient per unit was 89.78%. , down to 85.56%, down 422%, the number of unplanned outages has risen four times, from 4 75 times/year in the previous year to 700 times/year; unplanned outage has 4 The number of flights has risen from 5, 540 hours/year in the year before the repair to 818.40h/year. The equivalent forced outage rate has risen four times. According to the above data, frequent overhaul does not completely improve the equipment. The level of health may also increase the equipment failure and reduce the reliability of the equipment. The unit is in good operating condition and the equivalent available coefficient in the year before the overhaul.

5 The inevitability of state maintenance The current maintenance system has increasingly deviated from its own purposes and is in urgent need of reform. There is a clear deficiency in the regular maintenance system based on the time period alone.

Some countries and regions have provided useful experience. At present, foreign countries have studied and implemented this work in the state maintenance system and related technologies. 70% of the power plants in the United States and the use of state maintenance technology in different degrees have become an international trend.

In 1987, the State Council repeatedly emphasized that the equipment management of industrial transport enterprises under the ownership of the whole people should actively adopt advanced equipment management methods and maintenance techniques, and adopt equipment maintenance based inspection methods to continuously improve the level of equipment management and maintenance technology modernization; It is necessary to continue to eliminate the time-based equipment maintenance system and establish a equipment system based on condition monitoring. The development of the state maintenance work of the power industry should be said to be at the forefront. The Dalian Electric Power Bureau and Shandong Electric Power Group Co., Ltd. have achieved initial results and accumulated valuable experience.

6 Conclusions Qualitative and quantitative analysis has shown the superiority and scientificity of state overhaul. In the future, a new maintenance system should be established in accordance with the requirements of the state maintenance system to achieve the purpose of increasing efficiency and improving equipment reliability. However, specific equipment analysis, and then appropriate maintenance methods, is also an aspect of state maintenance.

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