Accidents, analyze the causes of their occurrence, and propose preventive measures.
The 630 electric dump truck is the main transportation equipment of the Heiyugou open pit mine. Since it was put into operation, there is one 63 each in October and March 2002 respectively. When the truck is under heavy load, the bolt is broken due to the joint. Separate the electric wheel from the carcass. In addition to causing severe deformation of the flange of the electric wheel end and tearing of the cable pipeline, it almost caused a rollover accident, which caused great impact on the inspection and management of the mining and stripping production equipment of mine. Therefore, measures must be taken to prevent the breakage of the electric wheel coupling bolts to ensure the safe operation of the 630 electric wheel dump truck.
1 Analysis of the cause of the breakage of the electric wheel coupling bolt 1.1 The high-strength screw inspection of the connection mode of the electric wheel and the vehicle body, the electric wheel housing and the rear axle housing are fastened and connected, and the standard tightening torque of each bolt is 2 001 For accurate and convenient installation of the electric wheel. The tilting wheel housing method 1 and the rear axle housing of the truck have positioning pin holes, which can be positioned during installation, and the rear axle of the truck is flanged to facilitate the mounting of the electric wheel with the elastic yellow pad to prevent Loose bolts. On the same horizontal line of the lowermost part of the joint, 7 fastening bolts are arranged side by side. The purpose is to add a joint to prevent it from being too concentrated on a certain bolt.
The electric wheel coupling bolt breakage damage occurred. When the electric wheel flash coupling bolt broke and the electric wheel was completely separated from the truck, we immediately observed and evaluated the accident site and found that the two trucks had broken signs. For the electric wheel and the rear axle of the rear axle of the truck, the joint bolt is broken and the fatigue fracture is found in the private section. The fracture source is found. The fracture of the upper bolt shows a slant, close to 45, showing the pull. Broken sign, and the upper part of the electric wheel housing coupling flange has a more serious outward tilt.
In addition, the scene of the accident in October 2000 was a dumping site, and the scene of the accident in March 2002 was a stripping site. The road condition was very bad. The analysis of the fracture of the 1.3 electric wheel bolts was carried on the electric wheel with tires, tires and Ground contact, whether in the case of dynamic load or static load, the force of the electric wheel coupling bolt is different due to the different parts. According to the force of the vehicle and the way of flange connection, the coupling screw of the lower part of the electric wheel. It is pulled by the pull, and the electric wheel. The coupling bolt of the part is in the abnormal case of the joint. In addition to the pull-in effect of the pre-tightening force. + Subject to any force. And as the direction of the bolt mounting position changes. The tension received is gradually reduced. In theory, the position of the high factory axis becomes zero. Of course, the shear stress and the joint surface of the rear axle of the truck are in relative motion during the truck operation, so the effect on the shear stress is almost Not there.
Then, how does the electric wheel coupling bolt break? For the 630 electric dump truck, the self-weight is 108.8, and the total weight at normal load is 281. Based on the design idea, the weight distributed on each rear wheel is 93.7. According to the force analysis, the static load can not break the bolt anyway. However, during the operation of the truck, the impact load is quite large due to road speed and loading. It can be inferred from your = momentum formula that the impact load is several times or even ten times that of the static load, and the coupling is a bolt. Due to the structure of the bolt itself and the viscosity of the manufacture, stress concentration is easily generated at the bottom of the thread. . From the analysis of its damage and force analysis, the 630 truck is vibrating and impacting due to its own movement and the bumps of the road during its operation. Although the buffer of oil and gas shock absorbers. But it can't be eliminated and offset. This impact load causes stress concentration in the coupling bolt. During the fixed operation period, the stress concentration caused by the impact will be repeated, which will cause the bottom joint bolt to produce seven fatigue. When the fatigue crack is generated, the connection between the electric wheel and the vehicle body becomes more. Unreliable; on the other hand, the maximum force position is gradually moved up, which deteriorates the stress of the joint bolt and increases the speed of fatigue cracking. When the fatigue cracking is extended to a certain degree, especially when the 7 bolts of the lowest sound 5 and the 7-foot flat are mostly fatigue cracked and subjected to the impact of strong vibration, the electric wheel bolt can no longer bear. Such a huge impact load, all of which breaks instantaneously, causing the electric wheel to separate from the truck, and exhibits a fatigue fracture of the lower coupling bolt, and the upper coupling screw is a tensile fracture. The upper edge of the electric wheel is tilted outside. 1 According to the above-mentioned clothing, the fatigue strength of the original flashing bolts causing the breakage of the electric wheel coupling bolts is insufficient and the vibration during the operation of the truck.
2 Measures to prevent breakage of joint bolts 2.1 Management and inspection of bolts The joint bolts of important parts are the key components of the equipment. Purchasing and storage should be strictly in accordance with technical requirements to create the necessary conditions for the safe operation of electric wheels. Before the installation of the electric wheel, the repairman should carefully check each connecting bolt. For the bolts with deformation cracks and damaged threads, they must never be used again to ensure the quality of the connecting bolts. When installing, make sure that the pre-tightening force 2.2 determines the life cycle of the coupling bolt. When the splicing screw is used, after the interval or after the cycle, although the surface looks good, it is due to the stress. It may produce a slight fatigue crack or plastic deformation.
The internal organization can make a change. The inspection of the apricot on the naked eye is not able to confirm the state. If it continues to be used, it will bring uneasiness to the truck's hall, and provide conditions for stress concentration. The life cycle is an important means to ensure the safe and reliable operation of trucks. Our mine stipulates that the use of two cycles or the use of more than 60,3 of the swaying wheel bolts is scrapped to ensure the safety and reliability of the electric wheel connection.
Strengthening the 630 trucking, the inspection and management of the fatigue fracture of the connecting bolts never occurred in an instant, and it must have a process of continuation. If in daily operation management, standard operation and maintenance, strengthen inspection and inspection, find the signs of fatigue cracking of bolts in advance, and take corresponding measures, it is to avoid the engagement between the accident wheel and the truck axle shell where the electric wheel and the truck are completely separated. There will be mutual and moving traces, and the coaxiality will change to varying degrees.
Taking measures to reduce the vibration and vibration of the car body is the most direct cause of the impact load, and whether the road is leveled becomes the key to affect the vibration of the truck, especially the roads of the stope and the abandoned site are more important. Therefore, the quality of the truck road is reduced; secondly, it is necessary to adjust the vibration of the vehicle body before and after the truck according to the technical specifications; once again, when loading the vehicle, it should be loaded as balanced as possible, and the load should be over-biased. To avoid the vibration caused by the bias, to reduce the vibration of the truck operation, it is also necessary to improve the quality and responsibility of the truck operator, which is also an important guarantee for the safe operation of the truck.
3 Conclusion In summary, the accident of the separation of the electric wheel and the vehicle body caused by the breakage of the coupling bolt not only affects the mining and stripping production of the open pit mine, but also brings great hidden dangers to the operation safety of the mine equipment.
The root cause of this accident is the vibration of the truck and the fatigue strength of the bolts. Take targeted measures. Preventing the occurrence of similar accidents is of great significance to the production of open pit mines.
In 1992, he graduated from the Inner Mongolia Institute of Technology as the director of the auto repair workshop of the Heilongjiang Open-pit Coal Mine.
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