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The scrap crusher is a machine that uses a high-speed rotating hammer installed in the casing to crush materials by impact. The rotor is the primary operating part of the scrap crusher. The main shaft is an important part supporting the rotor. It accepts a large cyclic impact force. Therefore, the material of the main shaft is required to have high strength and resistance, and an option that can accept heavier impact loads is required. Bearing. Generally, single-rotor scrap crushers are equipped with double-row radial spherical roller bearings that can operate normally at high speeds and have small conflict forces. The balance (static balance and dynamic balance) of the scrap crusher rotor equipment is relatively high. When the rotor has a small offset, the large periodic inertia force generated by it acts on the bearing, which can cause The machine oscillates violently, which accelerates bearing wear. In practice, after investigation and analysis of the reasons for the early failure of the bearing, the experience is summarized as follows.
1. The original situation takes the metal crusher manufactured by our factory as an example. The main shaft of the machine is 45# steel after quenching and tempering heat treatment, and 3628 double row radial spherical roller bearing support is optional. When the equipment is in normal production, the bearing temperature often rises sharply (the temperature exceeds 80 degrees). When it is severe, it is accompanied by mechanical noise, which affects the normal production. Started to adopt shutdown cooling and intermittent operations to maintain the condition that the equipment was unable to operate normally after more than a month of production. I had to shut down and check. During maintenance, it was found that the inner ring of the bearing and the shaft journal of the main shaft were cohesive (adhesive) wear, which was severe The journal of the adhesive part was torn and peeled. Two sets of rotor assemblies supplied by the original manufacturer were replaced one after another, but after the replacement of new bearings, the above phenomenon was similar to each other.
2. Possibility of investigation Firstly, it is suspected that the above-mentioned problems are caused by the imbalance of the rotor and the inertial force, but the wear of the rotor key head is small and uniform, the static balance is good, and there is no large oscillation during operation. During the inspection, it was found that the smooth grease in the bearing seat was dry and failed. It is suspected that the failure of the smooth grease may be caused by overheating of the bearing and burned. Therefore, in the future, the focus will be on strengthening the smooth handling of the bearing, fixed grease timing and quantitative refueling, and the service cycle has been slightly improved, but it has not effectively avoided the repeated occurrence of journal adhesion surface damage. After all, the analysis may be due to the improper structure of the bearing equipment.
3. Analysis conclusions Because the crusher rotor receives a heavier impact load, the bearing will generate heat due to conflict during bearing operation, which makes the temperature of the bearing inner ring higher than the temperature of the shaft journal that it cooperates with, and the cooperation between the bearing inner ring and the journal is loosened due to thermal expansion. In practice, due to the different changes in the temperature rise of the inner ring of the bearing and the journal, the nature of the cooperation has also been continuously changed in each period. The cooperation between the bearing inner ring and the journal is interference cooperation in the initial state (within about 1 hour), gap cooperation in the initial stage of operation (within about 2 hours), and transitional cooperation in the later stage of operation (about 2 hours later). Therefore, the public service cooperation selected in the original plan is likely to cause the bearing to expand due to conflict and heat. In the first 1 to 2 hours of the operation, the inner ring and the journal relatively slide, and the inner ring "creeps" on the oil neck cooperation surface. Due to the high variable load stress of the cooperative journal, peeling occurs on the metal surface due to fatigue, which eventually leads to the early failure of the bearing and the adhesive wear of the journal.