During pressure keeping, due to the existence of the piston clearance, the lower side of the pressurized air enters the upper side, so that the pressure difference between the upper and lower sides of the piston cannot be formed, thereby causing the pressure air on both sides to leak with the brake cylinder and losing the automatic air supply, eventually resulting in The brake cylinder is relieved.
For other reasons, this fault was demonstrated during the bicycle test, but the data on the 705 test bench was all qualified. The current pilot project was based on the 1984 Ministry of Railways document. With the increase of the service life of the 104 type distribution valve, each moving part has different degrees of wear, and there are certain differences between the different parts of the manufacturer, such as the poor cooperation between the lower part of the piston cover and the valve body, resulting in assembly. There is a gap between the working piston, so that the pressure air of the brake cylinder passes through the gap → volume chamber → lower side passage of the pressure increasing valve → slip valve relief contact groove → air valve hole of the sliding valve seat → exhaust port of the main control unit → atmosphere.
The normal wear of the type 104 air distribution valve fittings and the differences between the parts manufacturers will cause gaps in the assembly of the 104 valve, which will destroy the automatic air supply of the distribution valve, resulting in the relief of the brake cylinder. To this end, it is recommended to increase the test item of the 705 type test bench, that is, after the original 705 type microcomputer console micro-control test is all qualified, the test stand is set to the manual position, and the handle is placed to the fixed position, and the handle is placed. After the 6-position decompression is 170 kPa, the handle is placed in 3 positions for 3 minutes, and then the exhaust port of the action portion is blocked, and then the handle is placed in one position to observe whether the brake cylinder pressure is lowered. After taking this measure, the Zhengzhou bus section found three faults in the brake pressure of the brake pressure brake cylinder on the 705 test bench within one month. After the decomposition check and replacement of the piston, the fault was eliminated.
The maintenance process requirements for the spring positioning seat structure A4 are not clear. In the "25K type passenger car A4 repair procedures", the maintenance requirements for the CW) 2 series bogie axle box positioning seat are only in the 4.. bogie must be fully decomposed, remove the rust, after the parts are repaired, the rust is applied. Paint (except for special requirements) is covered in Article 0, and there are no other maintenance requirements. There is no clear definition of whether to replace it or the specific maintenance methods and limits.
The process of A3 is not perfect. In the implementation of the A3 process, it can be loaded and used according to the regulations, and there is no specific standard. In the process of repairing, the Qiqihar section only derusted, visually inspected and painted. Under such overhaul technology, a large number of serious crack failures were found. It can be seen that there are a large number of safety hazards in the use of passenger cars.
Improvement measures and suggestions (1) Change the original design structure and increase the wall thickness of the cylinder and the thickness of the bearing part. To increase stiffness and strength. When loading, consider reducing the thickness of the rubber seat of the axle box spring positioning seat to keep the height of the bearing surface of the axle box spring constant; change the connection between the cylindrical structure of the positioning seat and the bearing part of the base to the rounded corner transition. To reduce stress concentration ((b)). (2) All of them are updated during the A4 repair to ensure the quality of the subsequent use. (3) Check the wear level of A3 when repairing, when the bearing part wears more than 1mm, it should be scrapped; increase the flaw detection inspection process, and carry out electromagnetic flaw detection on the parts prone to cracks to ensure the elimination of safety hazards.
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