Common faults and countermeasures of pneumatic ball valve
The railway has adopted a new operation and maintenance mode for the five major speed increases, which can last for up to 20 hours of point-to-point operation between cities. The continuous operation speed reaches 160 kilometers per hour, and a warehouse inspection operation meets 5000 kilometers (one round trip) without maintenance. The adoption of this operation and maintenance mode puts forward higher requirements for the safety, reliability, maintenance free and stability of the self-monitoring system of passenger cars.
Therefore, when the 25T bus with large speed increase generally enters the A2 repair program, the Leap Weekly · Forum does not invite vehicle manufacturers and vehicle maintenance personnel to discuss the maintenance countermeasures of the 25T bus. In order to meet the requirements for the stability and comfort of train operation, the SYS series pneumatic ball valve suspension system has been widely used on the 25T type passenger car bogies for the five times railway speed increase. After more than a year of application tests, the overall application of the pneumatic ball valve is good and can meet the operational requirements of China's railways, but there are also problems in the operation and maintenance.
Pneumatic ball valve is an inflatable ball valve that is filled with pressure air in a flexible closed container and uses the compressibility of air to achieve elastic effect, so it has high requirements for air tightness.
Pneumatic ball valves are generally sealed by screw fastening and pressure self sealing. The former uses screws to fasten the metal retaining ring, capsule sealing part and upper cover plate together for sealing; The latter uses the air pressure inside the capsule to compress the sealing surface of the capsule and the cover plate to seal. Because the pressure self sealing structure has the advantages of small size, light weight, convenient installation, etc., the 25T passenger car bogie widely uses this sealed pneumatic ball valve.
The pneumatic ball valve system of 25T passenger car bogie is mainly composed of pneumatic ball valve, height control valve, differential pressure valve and additional air chamber.
The height control valve is an important part of the pneumatic ball valve system. It mainly adjusts the air pressure in the pneumatic ball valve automatically when the vehicle load changes, so as to maintain the height of the vehicle body unchanged. The differential pressure valve is mainly used to ensure safety. When the pressure difference between the pneumatic ball valves on both sides of a bogie is large or the ball valve on one side is broken, the differential pressure valve automatically communicates with the pneumatic ball valves on the left and right sides to avoid excessive inclination of the car body and prevent derailment, so as to ensure stable and safe operation of the vehicle.
During the operation of pneumatic ball valve, air leakage may occur due to climate conditions, line conditions (especially small radius curve), components of pneumatic ball valve system, quality of pneumatic ball valve itself and other comprehensive factors.
There is air leakage between the upper cover and the capsule. For the pressure self sealing pneumatic ball valve, after about one A3 repair, there is compression permanent deformation and aging phenomenon in the upper cover and capsule sealing part. When suddenly bearing a large transverse impact, the upper cover and capsule sealing part will be mismatched, resulting in air leakage When the temperature drops in winter, the material performance will become worse, and the air leakage fault is more likely to occur. In addition to the factors of the pneumatic ball valve itself, complex operation conditions, improper operation during operation and maintenance are also the main factors causing air leakage between the upper cover and the capsule. The sealing part of the upper cover and lower seat is degummed and air leaks. The sealing part of the upper cover or lower seat is a layer of vulcanization. During production, when the upper cover metal skeleton and vulcanization were carried out, the vulcanization surface was not clean enough or the application of adhesive was uneven, which resulted in poor bonding strength. After a period of use, degumming and rubber layer deformation occurred, resulting in air leakage. Air leakage can also be caused by artificial or accidental damage of capsules in use. The sealing part of the upper cover, lower seat and capsule has air leakage caused by defects such as lack of glue, inclusion and damage.