According to the investigation results, during the appearance inspection of bearings, it was found that 47.3% of the total number of bearings were unloaded due to the extrusion of sealing cover and sealing failure.It indicates that the failure rate of newly built and overhauled bearings is high during the quality guarantee period, and the failure occurs if the quality guarantee period is not reached, resulting in frequent maintenance of bearings.In particular, bearing seal failure to discharge greatly increases the bearing discharge rate.Then what causes the truck bearing seal to come out?According to the understanding of Zhonghua Bearing Network (abbreviation: Zhonghua Bearing Network), we will share the related reasons and control measures for the extrusion of the truck bearing seal cover.
1. Reasons for bearing seal cover coming out
1) due to the outer ring threaded groove depth or width can not meet the standard, even without grooves, cause the seal cover the threaded convex platform could not enter the outer ring threaded groove, not only not prevent seal cover out effect, but also damage the outer ring threaded and sealing cover due to cooperate, make the fit interference quantity was not up to standard or even no surplus quantity, in the vehicle, seal cover gradually emerge due to the vibration of the vehicle.
2) Because there is no guide chamfering on the outside of the outer ring mouth, in the assembly process of the sealing cover, the sealing cover mouth boss can not enter the outer ring mouth smoothly and is cut off, resulting in the sealing cover without boss, and the sealing cover is pulled out in the operation of the vehicle.
3) can be completed on truck not withdrawal bearing appearance inspection, in accordance with the provisions of no specific inspection seal cover out judgment method, only in the withdrawal of bearing, bearing (including outer cover, seal, rubber oil seal, seal seat, front cover, gear, shaft end bolts, etc.) after the appearance of cracks, bruising, loose, deformation and other different shape of withdrawal.To this end, the truck does not unload the bearing when the outside
There is no specific inspection standard for inspecting whether the sealing cover has come out, which makes some sealing cover come out without timely detection and withdrawal.
4) bearing parts, general maintenance carried out in accordance with the provisions of the bearing outer ring threaded groove depth, breadth, and the outer ring chamfer size measurement standards and methods, such as caused due to the outer ring threaded such as groove depth, breadth, and the outer ring chamfer size unqualified bearing cannot be found in general maintenance and control and continue to use, the load to the bearing operation.
2. Control measures to prevent bearing seal cover from coming out
1) Improve the quality of bearing manufacturing and overhaul. In particular, manufacturers should focus on controlling the depth, width, machining roundness and outer ring machining chamfer and other geometric dimensions. If they do not meet the requirements of the drawings, they are prohibited from factory.
2) Establish an information communication system between bearing manufacturers and overhaul manufacturers and users.Organize quality exchange between manufacturers and users every year.The use unit will feedback the bearing manufacturing quality problems to the bearing manufacturers and overhaul manufacturers, so as to cause the manufacturers and overhaul manufacturers to pay attention to the bearing processing quality, so as to avoid the same quality problems in the bearings manufactured in the future.When the bearing overhaul factory overhauls the bearing, it shall process the bearing whose processing quality cannot reach the standard to reach the process standard. The parts that cannot reach the standard shall be scrapped and shall not be assembled into the overhauled bearing.
3) in general manufacturing quality problems found in the process of inspection and is in quality guarantee period of the bearing, manufacturers offer a claim and will return to factory were analyzed, and the bearing manufacturer in view of the problem to develop targeted rectification measures, in order to better improve the quality of bearing source, reduce the use of hot shaft accidents caused by bearing failure.
4) Control measures for sealing cover appearance inspection and parts inspection during section repair shall be strengthened.
A. Set up a special appearance inspection procedure at the bearing collecting place and bearing closing place, and the workers, foremen, quality inspectors and inspectors shall rotate and inspect the non-returning bearings one by one.
B, A visual inspection must be manually turn the bearing's outer ring more than 3 ~ 5 laps, carefully check the state of external and internal vision, bearing on the same sound but also focusing on the bearing outer ring, seal cover (LL type sealing device of oil seal, oil seal, front cover, inside and outside after if there is A crack damage, looseness, both before and after the seal cover whether partial pressure, pressure does not reach the designated position, cover before and after the block is not A problem, and check the sealing device a-side direction shall not be higher than the outer end of the week.
C. The cleaned bearing front cover and back cover shall be tested in accordance with the requirements of the test items. The dimensions qualified by the test shall be marked on the outer diameter of the front cover and back cover.
D. Develop torque detection tools for non-retractable bearings to ensure that the non-retractable bearings do not loosen under the specified torque.
E, bearing parts in addition to strictly in accordance with the railroad truck axle assembly, maintenance and management rules prescribed by the project and standard for inspection, measurement, when making parts appearance inspection, increase the pressure for the bearing outer ring and sealing cover into the chamfer size, the threaded abrasion, groove depth and width of the threaded size inspection measurement.At the same time, the relevant size limits and inspection standards of different types of bearings are included in the "Railway Freight Car Wheel and Axle Assembly, Maintenance and Management Rules".
F. Specification of specific interference standards for sealing cover and outer ring during bearing testing.When the sealing cover is selected, the recommended interference is within the range of 0.18 ~ 0.28.
G. When newly made or overhauled bearings leave the factory, the inner diameter size and clearance size shall be sent to the user together with the bearings. The user shall check before use and control the inner diameter size and unqualified axial clearance bearings of the manufacturers for loading and use.
H. Control the occurrence of loading and use of bearings with faults caused by improper packaging and protection for newly made and overhauled bearings.Using department will seal seat before bearing used are taken from the bearing (except LL type sealing device), check the internal and external oil seal for flanging, tearing, inner seal installation does not reach the designated position, not wait for a phenomenon, one by one check the sealing seat, to see if there are any more CARDS inside and outside the oil seal with state resistance, geometry distortion and not a problem.Seal cover in place to check installation using depth vernier caliper, or sample inspection, must ensure that seal cover surface installation shall not be higher than in the week direction outer end face, no partial pressure, pressure equipment does not reach the designated position, or convex platform is pressed out and being connected in the bad phenomena such as over-voltage found unqualified bearing should stop using the batch bearing and return to factory.
I. After the bearing is pressed, the running-in test should be carried out with the speed not less than 200 r/min and the time not less than 5 minutes.In the running-in process, workers should listen carefully to the running-in sound of both ends of the bearing, and there should be no different sound when the bearing rotates.The temperature gauge should be used to test the temperature rise of the bearing in the running-in process, and the temperature rise of the bearing should not be higher than 40 ℃ after running-in.In the running-in process, there are abnormal conditions, abnormal sound, friction and other sounds or the temperature rise on both sides is large, the running-in time should be extended to 15 minutes.Careful inspection should be carried out on the unqualified bearings in running-in.It is forbidden to load unqualified bearings for use.
J. Inspection and monthly comprehensive performance check of strengthened bearing testing system, bearing single column correction press, sealing cover pressing mould, torsional torque testing equipment and bearing pressing machine before starting every day.If the equipment state cannot meet the working quality requirements, timely repair shall be carried out to ensure the good performance of bearing maintenance equipment.