Causes And Prevention And Control Measures Of Freight Car Bearing Seal Cover Falling Off

1. The reason why the truck bearing seal cover comes out during operation

In most cases, the sealing cover is not caused by one reason, but by the coupling of multiple factors, some of which pop up instantly, and some of which move out little by little. Let’s analyze the main reasons that cause the sealing cover to come out:

1) The groove and chamfering of the outer ring of the bearing are not standard

According to the analysis of the reasons for the prolapse of the seal cover in recent years, the main reason for the prolapse of the bearing seal cover is that the groove of the outer ring of the bearing and the chamfering processing are not standard. After the bearing seal cover and the outer ring are assembled, they form an integrated structure without mutual movement. The circumferential non-movement between the seal cover and the outer ring is due to the interference fit between the seal cover and the outer ring teeth, and the axial non-movement is an interference fit. The boss of the sealing cover enters the groove of the outer ring of the bearing to prevent the outer movement of the sealing cover. Whether the groove of the outer ring of the bearing is standard plays a decisive role in preventing the sealing cover from coming out. If the depth and width of the groove are not standard or there are ribs in the groove, it will not only fail to prevent the sealing cover from moving outward, but also destroy the interference fit between the teeth of the outer ring and the sealing cover, thus causing the sealing cover to come out.

2) The thickness of the sealing cover is insufficient, the strength is small, or the processing of the mouth and the boss is not standard

According to the requirements of the drawing, the sealing cover is stamped and formed with a 2.5mm thick steel plate, and the mouth and the boss are machined to ensure that the size of the mating surface of the mouth and the boss meet the standard. In order to process the height of the boss 0.26±0.06mm, the thickness of the mating surface of the mouth of the sealing cover is generally between 2.1 and 2.2mm, and the thinnest is only about 2.0mm. During the assembly of the sealing cover or the operation of the vehicle, deformation due to insufficient strength or deformation of the sealing cover due to clamping and unreasonable processing volume during the processing process will make the roundness or boss size non-standard, resulting in the sealing cover falling out during operation.

3) The interference between the sealing cover and the teeth of the outer ring of the bearing does not meet the standard

Reasonable selection of the fit interference between the seal cover and the outer ring of the bearing can not only prevent the mutual circumferential rotation, but also play an important role in preventing the seal cover from escaping in the axial direction. Insufficient interference, the sealing cover is easily loosened or disengaged due to centrifugal force and rotational torque during vehicle operation. If the interference is too large, it is easy to damage or even cut off the boss during the assembly process of the sealing cover, and it will cause a large elastic deformation and stress on the sealing cover, and it is easy to fall out instantly when it is subjected to vibration or impact.

4) During the assembly process of the sealing cover, the mold and the bearing are not concentric, and the boss of the sealing cover is damaged and cut off

The mold installation position of the seal cover assembly machine is inaccurate or the wear of the mold is not concentric with the bearing. When the seal cover is assembled, the seal cover is forced into the outer ring of the bearing by pressing force, which will damage the boss of the seal cover or even cut off part of it. During the operation of the vehicle, the sealing cover first comes out from the damaged part of the boss.

5) Internal failure of the bearing or poor fit between the raceways, large temperature difference between the inside and outside of the bearing

Bearing internal faults such as raceway surface peeling, skin rolling, poor fit between inner and outer ring raceways and rollers, impurities in grease, grease injection volume does not meet the standard, bearing clearance is too large or too small, etc. Heat is generated during operation, the internal temperature rises, and the pressure increases. Especially in winter, the temperature difference between the inside and outside of the bearing is large, which increases the force of the seal cover to come out. and
And the internal heat of the bearing is first generated or transmitted to the outer ring, and then transferred to the sealing cover through the outer ring. The thermal expansion of the outer ring reduces the interference with the sealing cover and increases the possibility of the sealing cover coming out.

6) Improper selection of the interference between the bearing and the journal during press-fitting

When the interference between the bearing and the journal is too large, the bearing clearance will be reduced, the rotation resistance will increase when the vehicle passes through the curve, and the bearing temperature will rise. The interference between the bearing and the journal is too small, especially if the journal has an inverted cone, the interference between the inner inner ring of the bearing and the journal is too small, which will cause fretting abrasion between the journal and the inner inner ring of the bearing, and also cause the bearing The temperature rises. If the fretting wear is gradually aggravated, it may cause the bearing to rotate, and if it is not found in time, there is a danger of cutting the shaft.

7) The wheel tread is scratched, and the running quality of the vehicle is poor

Faults such as scratches and peeling of the wheel tread will cause the vehicle to vibrate during operation, impact the bearing, deform the teeth of the outer ring of the bearing and the sealing cover, and cause the sealing cover to fall out in severe cases. Since the outer side of the bearing has the largest amount of deformation when it vibrates and is impacted, most of the sealing cover comes out of the sealing cover on the outer side of the bearing.

In addition, the partial load of the vehicle, the centrifugal force when passing the curve, the impact on the bearing when the bogie is completed, and the bumping of the bearing during transportation may all cause the sealing cover to come out.

2. Prevention and control measures for truck bearing seal cover falling off

1) Improve the quality of workers

Key positions must choose personnel with high education level, serious work and strong sense of responsibility, who can explore and sum up experience in work, and continuously improve their job skills. For personnel with high technical quality and strong ability, it is necessary to maintain relative stability.

2) Strengthen equipment guarantee

There are a lot of high-precision testing equipment, instruments and measuring tools for the general maintenance of bearings. If the precision is not enough, or the debugging does not meet the requirements, it will affect the quality of all bearings. Therefore, the instruments and measuring tools must not only be calibrated on time, but also observed and adjusted at any time during normal work to ensure that the testing equipment and instruments are in good condition and achieve the accuracy and accuracy of the test.

3) Ensure the accuracy, perfection and practicability of process standards

Write a detailed “job operation instruction book” and revise and improve it in time. For the process documents, telegrams and control measures issued by the superior, the requirements in the process documents, telegrams and control measures must be refined according to the workshop’s process flow, process equipment and other specific conditions. work instruction book.

4) Strengthen operation process control

The first is to strengthen the mutual control between posts. If the bearings that are not withdrawn must be inspected comprehensively at the posts of bearing press-fitting and cover closing; Check the appearance of the boss of the mouth of the sealing cover, etc. The second is to strengthen the inspection and control of the management personnel on the operation process. Once the quality of some operations leaves the station, the quality cannot be checked, such as whether the inspection of each part is carried out in a week, whether the inspection size is accurate, and whether the outer ring and seal of the sealing cover are assembled. Whether there is grease on the teeth of the cover, etc., so it is necessary to strengthen the inspection of the operation process, and the operation enables the operators to develop good working habits, so as to ensure the quality of bearing maintenance.

5) Strengthen the inspection and control of the quality of key parts

For non-removable bearings, focus on checking whether the sealing cover is loose, falling out, oil leakage, oil throwing and other sealing failures. The sealing cover should not be higher than the end face of the outer ring in the direction of one week; carefully check the rotation of the bearing on the runner , Accurately determine whether there is a fault inside the bearing. For general maintenance of bearings, focus on checking the geometric dimensions of the groove and chamfer of the outer ring of the bearing and the shape and size of the boss of the new sealing cover; strictly select the sealing cover and the outer ring of the bearing, and control the interference at 0.20 Between ～0.25mm; before the bearing assembly starts and after press-fitting, check the state of the sealing cover assembly press to ensure that the equipment is in good condition, check that the press-fitting mold is free from wear, deformation, flashing, etc., and that the mold and the bearing are concentric; Before assembling the device, ensure that the mating surface of the sealing cover teeth, the outer ring teeth and the groove are dry, clean and free of oil; when pressing the cover, stop using the equipment with noise, carefully observe and listen to the sound of the sealing cover entering during the pressing process, and judge Whether the press fit is in place and whether the boss of the seal cover is damaged; after the seal cover is pressed, the quality of the seal cover must be checked with an inspection sample and a depth vernier caliper; the torque of the 26 series bearing sealing device is tested one by one after assembly, and the torque must not be 122.5N·m Loosening; the bearings should be handled with care during transportation, and throwing and bumping are prohibited; when the bearing is pressed, the interference between the bearing and the journal should be strictly selected to ensure that the inner diameter of the inner ring of the two circles and the interference of the journal are consistent Standard and balanced; strictly check the appearance quality of the bearing saddle, the grooves on both sides of the saddle surface, and no raised points higher than the inner saddle surface; when the bogie is completed, prevent the bogie from falling heavily or use a crowbar to pry the load at the end of the bearing The saddle causes the vibration of the bearing sealing device to cause the occurrence of the problem of escape of the seal cover.