Analysis of wear failure of support shaft bearing position of tube bundle dryer and on-site repair case

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The rotary tube bundle dryer is an indirect heating contact dryer that works on the counter-current principle. It can be widely used in chemical industry, light industry, food, grain, feed and other industries for loose materials such as powdery, granular and flaky materials without much viscosity. Tube bundle dryers are currently most advanced * * One of the most widely used and advanced dryers. The main reasons are that the heat consumption is very low, the drying material range is wide, the output is large, the water evaporation is large, and high-moisture materials can be dried (the drying time can be adjusted according to different material properties and moisture requirements), the degree of continuous production is high, and it can also be applied to special production processes. Another point is that the machine has very few wear parts and is easy to install, so the maintenance cost is very low. The rotor of the rotary tube dryer is composed of hollow shafts at both ends, a head and a tube bundle formed by hundreds of tubes. Its general internal structure is shown in the figure below ； During operation, the rotor is supported by bearings at both ends: One end is a fixed bearing, and the other end is free to swim and consume thermal expansion. There are copy plates fixed on the frame around the rotor. 1. Analysis of wear failure of the main support bearing of the dryer a. The dryer must bear a large gravity when fully loaded. ； Support bearings must carry a lot of pressure ； When the equipment is running, due to the rotation of the tube bundle and the unevenness of the material, the transmission shaft will vibrate to varying degrees. ； These vibrations will affect the stability of the transmission mechanism ； b. Since high-temperature steam is introduced into the tube bundle, the temperature is generally around 120-170 degrees Celsius. ； When operating in a high-temperature environment for a long time, high-temperature lubrication and cooling of the bearings are also very important. ； Once the maintenance is not in place or the operation is overloaded, the support bearings are easily affected by high temperatures and cause failure, which directly leads to severe wear of the bearing positions. ； In serious cases, the equipment will cause unpredictable losses ； This will cause great harm to production and personnel safety ； c. Under normal circumstances, the support bearing position is prone to wear, and the cause is mostly due to bearing failure and wear. ； When the bearing rotates under load, the raceway surface or rolling surface of the inner ring and outer ring will peel off like fish scales due to rolling fatigue. The raceway wheels or rolling elements are prone to crack damage. The wear caused by repeated micro-sliding between the two contact surfaces will cause wear damage to the contact parts of the raceway surface and the rolling elements. Due to reasons such as the rise in high-temperature steam temperature and the reduction in lubricant performance, the bearings will discolor and fail, and the raceways, rolling elements and cages will also discolor and fail. To sum up, improper bearing lubricant, excessive load, excessive preload, excessive interference, biting of foreign matter such as metal powder, etc. will all cause damage to the bearing position. 2. Comparative advantages of polymer repair technology and traditional repair technology a: Traditional repair technology In China, repair welding, bushing and other processes are generally used for on-site repair of worn support bearings of such large equipment. The main problem with the repair process of the Xiang bushing is that it is difficult to ensure the large-area fit between the shaft diameter and the bushing. It is a multi-point contact. Due to the large gravity and overload pressure, once fatigue deformation occurs at the support point, it will also cause secondary wear of the shaft diameter. The repair welding process itself can easily cause local thermal stress on the shaft surface, causing the hidden danger of shaft breakage. On-site repair welding to repair the mating surfaces requires a lot of manpower and time, making it difficult to ensure mating accuracy and easily causing damage to the bearings. If it is repaired by machining after welding, the comprehensive cost of maintenance labor, equipment transportation and machining will be higher and the cycle will be longer than on-site repair. b: The polymer repair material process adopts different repair plans according to different wear conditions. Taking 2211F metal repair material as an example, polymer composite materials are used to repair worn parts on site. On the basis of ensuring repair accuracy and meeting installation requirements, there is no need to disassemble a large amount of equipment, and the repair cycle is short. Repair and installation work is generally completed within 8-12 hours. The repair cost of this repair process is lower than that of the traditional repair process. Generally, the amount of polymer composite material is calculated based on the wear amount of the bearing position, and then the repair cost is calculated. The main advantage is that the fit between the polymer repair surface and the inner ring of the bearing is very close, almost 100%, thus avoiding the problem of stress damage to the bearing caused by local point contact. 3. Dryer bearing repair application cases