The overhaul limit of railway freight cars refers to the regulations on the degree of damage allowed to the parts and components of freight cars when the freight cars are overhauled. It is an extremely important technical regulation for freight cars. Whether the overhaul limit is set reasonably or not has a direct impact on the quality of the vehicle used and the economic effect of truck overhaul.

Because the factors that affect the damage and service life of truck parts are very complicated, theoretical calculation methods often cannot fully reflect the various effects of actual working conditions. It must be based on theoretical analysis and calculation, combined with a large number of actual investigations and demonstrations. Better work out the overhaul limit standard.

The overhaul limits of all levels of repair programs generally show a gradual decrease. The overhaul limits of high-level repairs are stricter than those of low-level repairs, that is, the overhaul limits of high-level repairs should cover the overhaul limits of low-level repairs. The purpose is to reduce low-level repairs. Increase the safety and reliability of vehicles.

1. Classification of overhaul limits

Compatible with the current truck maintenance system and types of repair procedures, the railway truck inspection and repair limits are divided into four types: service limit, auxiliary repair limit, depot repair limit and factory repair limit. The inspection limit is generally expressed by the size value.

⒈ Application limit

The use limit is the degree of damage allowed for truck parts and is the basis for the continued use of the parts. In the daily operation of the truck, when the damage degree of the parts reaches the limit of use, it means that the damage has reached a certain damage state, and the parts cannot be used continuously and need to be overhauled or replaced to ensure the safe operation of the train.

⒉ Minor limit

The minor repair limit is the limit specified for the parts that directly affect the safe operation of the train, and is the basis for whether to perform inspections during the minor repairs of freight cars. Generally, the parts repaired or replaced according to the minor repair limit should be guaranteed to be used safely until the next repair period.

⒊ Segment repair limit

The segment repair limit is the regulation of the degree of damage allowed on the parts when the truck is undergoing segment repair, and it is also the basis for testing whether the damage is repaired or not.

⒋ Factory repair limit

The factory repair limit is the stipulation of the degree of damage allowed on the parts of the truck when the truck is repaired, and it is also the basis for testing whether the damage is repaired or not.

Although there are the above-mentioned 4 kinds of inspection limits in truck inspection, not all parts have these 4 kinds of inspection limits. Some parts have only factory and depot repair limits. For such parts, they are not included in the train inspection object in the use of freight cars. Therefore, the degree of damage is not specified in the minor training and application limits.

In addition, some parts have a certain degree of damage that only has a limit of application, indicating that such damage of the part is not allowed in other repair procedures, and should be repaired or replaced to restore its prototype size.

2. Determining the limit of overhaul

1. The basic principle of determining the maximum overhaul limit

The maximum overhaul limit refers to the limit limit, but not necessarily the overhaul limit. The overhaul limit leaves a certain safety margin on this basis. When formulating the overhaul limit, first consider the maximum overhaul limit, that is, to determine the maximum overhaul limit from the starting point of measuring the conditions under which the part cannot work normally.

①Working conditions of the part itself

When formulating the maximum overhaul limit, in terms of the working conditions of the part itself, the main consideration is whether the degree of damage destroys the strength condition of the part, and whether the degree of damage can make the existing damage develop rapidly and reach a dangerous degree.

②Working conditions for cooperation between parts

In addition to considering the working conditions of the parts themselves, the maximum damage of many parts should also be considered from the degree of damage to the working conditions of the parts in the parts and other parts. Generally, there are wheelsets and rails, pins and holes. There are several situations such as the fit of the shaft journal and the inner ring of the rolling bearing.

③Impact on the performance of the entire truck

Many overhaul limits are determined not only by considering the parts themselves or working conditions, but also by taking the safety and smoothness of truck operation as well as economic and technical rationality as the starting point to determine, such as safety in operation, train operation Stability, economic and technical rationality, etc.

2. Method of determining the intermediate limit

The intermediate limit refers to the overhaul limit stipulated in the repair procedures such as factory repair, partial repair and minor repair. The intermediate limit is also the basis for distinguishing whether the damage of each part needs to be overhauled in all levels of repair process. It directly affects the technical quality of trucks after inspection and repair, as well as the scope of each repair process, the size of the inspection workload and the cost of the repair. When formulating intermediate limits, the following main issues should be considered.

①Ensure that the parts can be used safely to the next regular maintenance of the same level or advanced level

This is the basic principle for determining the intermediate limit. There is a certain period of use for the part from this regular overhaul to the next regular overhaul. It is necessary to ensure that the part functions well during this period. Therefore, on the basis of the maximum overhaul limit of the part, consider the interval between two regular overhauls. The internal energy can be used safely, that is, to meet the guarantee period of the repair process.

②Mutual cooperation between the various repair programs

The intermediate limit puts forward different quality requirements for different repair procedures, and is also a standard for clearly dividing the scope of repairs at all levels. Therefore, when formulating intermediate limits, consideration should be given to the coordination of the various repair programs. For example: when carrying out higher-level repairs, it is necessary to create convenient conditions for lower-level repairs, that is, the workload of the repairs is large, the repair process is more complicated, and special special equipment and technically demanding repairs are required. To be completed in the higher-level repair process.

③ Carry out the principle of economy on the basis of ensuring the quality of maintenance

The overhaul limit of truck parts is not only the main basis for truck overhaul work, but also directly affects truck overhaul quality and repair cost. Therefore, when formulating various intermediate limits, factors such as saving the consumption of raw materials and new accessories should be considered as much as possible on the basis of ensuring the quality of maintenance and the period of use. For example, as the level of welding and repairing technology improves, the quality of welding and repairing after wear of various parts is also greatly improved, so that the limit requirements can be appropriately relaxed to reduce the number of repaired parts and reduce the cost of repairing vehicles.

In summary, when formulating the overhaul limits for all levels of repair programs, a comprehensive scientific analysis should be carried out, and the overhaul experience in production practice should be fully considered in order to work out a reasonable overhaul limit. At the same time, the principle of formulating overhaul limits will directly affect the size of limit standards and should be considered when formulating limits, as objective conditions change, such as changes in vehicle models and structures, changes in raw materials used for trucks, and changes in truck overhaul techniques. the elements of.