1, after-the-fact maintenance, also known as fault maintenance and damage maintenance. It does not control the maintenance cycle, but only carries out maintenance when the mechanical equipment fails or is damaged, so as to restore the original function. It applies to:
1) The failure of machine parts does not affect the safety of assembly and system, nor does it affect the overall production of equipment.
2) The fault is accidental and the law is unclear, or it is a wear fault, but it is more economical to maintain it afterwards.
As a maintenance strategy, after-the-fact maintenance can maximize the service life of main parts, which is different from the original and backward after-the-fact maintenance, but it is not suitable for equipment that has a great impact on safety, quality and production.
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2. Preventive maintenance. Preventive maintenance is a mechanical equipment maintenance activity in accordance with the pre-established repair plan and technical requirements, in order to prevent equipment performance from declining and precision from deteriorating or reduce the failure rate. Preventive maintenance can be divided into regular maintenance and condition monitoring maintenance.
1) Regular maintenance, also known as planned maintenance and time preventive maintenance. It takes the service time as the maintenance cycle. As long as the scheduled time is used, no matter what the technical state is, the specified maintenance work should be carried out to prevent unexpected accidents from becoming the purpose of maintenance. This is a compulsory preventive maintenance method. Maintenance is generally carried out in a planned way between production, and maintenance resources can be fully prepared in advance, which can reduce maintenance workload and downtime. It applies to:
① The failure mechanism has obvious time correlation, and the main failure mode is wear, which has certain regularity.
(2) During the service life, the expected wear failure of machine parts occurs, and the time of impending failure can be measured according to the wear law.
③ When it is difficult to check and judge the technical status of some important parts, regular maintenance is an effective method.
The advantage of regular maintenance is that it is easy to master the time, plan, organization and management of maintenance, which plays a good role in preventing faults. Its disadvantage is that it is not easy to consider other failure modes besides wear, such as fatigue and corrosion. When it is implemented, it is often not aimed at the actual situation, but a one-size-fits-all way of large-scale disassembly, which increases the number of disassembly times, is not conducive to giving full play to the inherent reliability of parts, and even leads to an increase in failures.
2) Condition monitoring and maintenance, also known as condition-based maintenance, on-demand preventive maintenance or predictive maintenance. It is based on the actual situation of mechanical equipment condition monitoring and technical diagnosis device prediction to determine the maintenance opportunity and content. Condition monitoring, including condition check, condition check and trend monitoring, is the most effective maintenance method. It is carried out online and implemented regularly as planned, requiring investment and recurrent expenses. It applies to:
(1) is a part with wear fault, which has the same slow development as wear, so the time from quantitative change to qualitative change can be estimated.
(2) It is difficult to find faults by relying on people's senses and experience, and it is not allowed to disassemble and inspect mechanical equipment at will.
(3) In case that the failure of machine parts directly endangers safety and there are limit parameters to be monitored.
In addition to its own detection device, condition monitoring also needs appropriate monitoring or diagnosis means, which can evaluate the technical condition of parts and indicate whether it is normal or not, so as to decide whether to repair it immediately. Its advantage is that it can give full play to the potential of parts, improve the effectiveness of preventive maintenance of parts, and reduce maintenance workload and human error. Mainly suitable for key equipment, high utilization, precision, large and rare key equipment.
Its disadvantage is that there should be enough reliability test data and information as the basis for judging the state of parts, necessary test means and standards, and large investment. Enterprises should decide whether to adopt condition monitoring maintenance according to actual needs and capabilities.
3. Improve maintenance. Improved maintenance is a maintenance method to eliminate equipment congenital defects or frequent failures. It is necessary to improve the local structure, parts and even system design of the equipment, and adopt new technologies, new materials and new processes to improve the performance, reliability and maintainability of the equipment. It is an important development of preventive maintenance, which is different from the usual repair-only repair or replace parts as they are, and modify parts or components that affect the performance of equipment and fail repeatedly, so as to reduce the failure rate of equipment and improve the service performance and life.
4. No maintenance design. Maintenance-free design refers to the ideal design of products (equipment), and its goal is to achieve the purpose of no maintenance in use. In the design of equipment, it is a maintenance strategy, also known as maintenance prevention, in order to eliminate the causes of maintenance, make the equipment run trouble-free or reduce maintenance work. At present, it is mainly used in large quantities of household appliances and equipment with high safety and reliability requirements, such as nuclear energy equipment and spacecraft. —— Henkel Machinery