The air spring is an inflatable rubber spring that is filled with compressed air in a flexible airtight container and uses the compressibility of the air to achieve elastic action, so it has high requirements for air tightness. Air springs generally have two sealing methods: screw fastening and pressure self-sealing. The former uses screws to fasten the metal buckle, the capsule sealing part, and the upper cover together to seal; the latter uses the air pressure inside the capsule Press the sealing surface of the capsule tightly with the cover plate to seal. Because the pressure self-sealing structure has the advantages of small size, light weight, and convenient installation, the 25T passenger car bogies widely use this type of air spring.
Air spring leakage. In the process of use, due to climatic conditions, line conditions (especially small radius curves), air spring system components and air spring quality and other comprehensive factors, (hardware spring) air springs may leak air.
Air leaks between the upper cover and the capsule. For the pressure self-sealing air spring, after using about an A3 repair process, the rubber of the upper cover and the sealing part of the capsule has compression permanent deformation and rubber aging. When suddenly subjected to a large lateral impact, the upper cover and the capsule are sealed The part will be misaligned and air leakage will occur. Especially when the temperature drops in winter, the performance of the rubber material deteriorates further, and it is more prone to air leakage failure. In addition to the factors of the air spring itself, complex operating conditions, improper operation during use and maintenance are also the main factors that cause air leakage between the upper cover and the capsule.
The sealing part of the upper cover and lower seat is degummed and leaks air. The sealing part of the upper cover or the lower seat is a layer of vulcanized rubber. In production, when the metal frame of the upper cover is vulcanized with rubber, the vulcanized surface is not clean enough or the adhesive is applied unevenly, which makes the rubber bonding strength poor, and degumming and deformation of the rubber layer occur during a period of use, resulting in air leakage phenomenon.
Man-made or accidental breakage of the capsule in use can also cause air leakage.
Air leakage caused by defects such as lack of glue, inclusions, damages on the upper cover, lower seat, and capsule.
During maintenance, if a slight air leak is found between the upper cover and the capsule of the self-sealing air spring, it is generally not necessary to deal with it, or the air in the air spring is exhausted and then refilled. The air leakage can generally be eliminated. Air springs with repeated slight and severe air leakage should be disassembled and inspected. If necessary, replace faulty parts or replace them as a whole.
Capsule failure The air spring (spring machine) has been used for about a period of time. Due to the long-term exposure of the capsule to the air, it is subject to the effects of ozone, sun, rain, and the corrosion of the capsule by organic solvents such as acid, alkali and paint during maintenance. , So that uniform and fine cracks appear on the rubber surface of the outer layer of the capsule, that is, cracks. Surface cracks are generally limited to the outer rubber, and the inner sealing rubber layer will not be damaged. However, there are also a small number of capsules where the local cord density is uneven during the manufacturing process. The capsules where the cord density is small will produce larger radial cracks after a certain amount of fatigue, and the cracks will extend to the middle cord layer. On-site statistics show that when the length of the crack on the surface of the capsule exceeds 30 mm and the width is greater than 1 mm, or when a dense pinhole-like shedding occurs at the crack, the crack has expanded to the outermost cord of the cord layer.
The test results show that the air spring still maintains air tightness and elasticity when there are serious cracks on the surface of the capsule. The air spring with relatively serious cracks on the surface of the capsule was filled with high-pressure water to slowly increase its internal pressure. After reaching 2.0 MPa, the air spring capsule was not damaged. This shows that the air spring still has sufficient compressive strength.
In use, the contact parts of the capsule and the upper cover and the lower seat will produce relative sliding friction, which will cause the surface of the capsule to wear, and in severe cases, it will wear to the capsule cord layer. Especially for bogies with large lateral swing, the parts where the air spring capsule contacts the upper cover or the edge of the lower seat will be worn, so pay attention to inspection during maintenance. The surface of the capsule is allowed to have local minor scratches and abrasions, but if it is worn to the cord layer, it should be replaced with a new one.
During the manufacturing process of the air spring capsule, the inner and outer rubber layers are not well bonded to the cord layer. During use, air will enter and stagnate between the inner and outer rubber layers and the cord layer, resulting in local bubbling. It should feel soft when pressed. It should be noted that the current SYS series air spring capsules for 25T vehicles have local unevenness on the surface. They are the protrusions formed by the normal overlap of the capsule cord joints on the outside of the capsule during the manufacturing process. It feels dense when pressed by hand. Yes, this phenomenon is easily mixed with the bubbling of the outer rubber of the capsule.
In vehicle operation, if the air spring is in the normal inflated state, if the continuous length of the crack on the surface of the capsule does not exceed 30 mm and the width does not exceed 1 mm, it can continue to be used normally; for surface bubbling, cracks exceeding the limit, and dense pinholes Capsules that fall out of shape can be replaced in the next A2 or A3 repair process; for capsules with damaged or exposed cords, they should be arranged for shunting immediately to replace them.