Case study: Detailed explanation of repair solutions for bearing seat wear (inner ring movement of the bearing)

Thread Content

【Abstract】 A new type of polymer composite material was used for emergency repairs of wear in the bearing areas of drying cylinder bearings and the bearing areas of idler shafts in cement kilns. The sources of wear and the advantages of on-site repairs were analyzed, and improvement measures to prevent equipment failures were proposed. 【Keywords】Bearing seat wear, journal wear, inner ring displacement of bearings, bearing seat repair. I. Repair of dryer cylinder bearing seat wear 1. Parameters and damage conditions of the dryer cylinder equipment: Model: 1760mm 8-cylinder paper machine; Speed: 200 meters per minute; Diameter of the bearing seat: φ328.8 (measured value); Width of the bearing seat: 165mm (measured value); Bearing model: 23068; Wear amount: 1.8mm. 2. Analysis of the advantages and disadvantages of traditional repair methods (1) Traditional repair approaches: a. Brush plating. It can handle minor wear on shaft components, but its capabilities are limited; the thicker the brush-plated layer, the more likely it is to peel off. b. Cladding. The most traditional method for addressing wear in shaft components is patch welding. However, due to the properties of the drum material, white cast iron cracks often appear at the weld joints during this process. Moreover, patch welding large areas of the shaft can cause thermal stress deformation, leading to bending or warping of the shaft, or even fracture at the shoulder area, resulting in the entire shaft becoming unusable. c. Spraying. The adhesion between the thermal spray coating and the substrate relies mainly on mechanical interlocking; as a result, the coating has poor impact resistance and is unable to effectively withstand the impacts exerted on the drying cylinder during operation. Moreover, the coating has a certain porosity; in addition, pollution such as dust, toxic metal vapors, heat radiation, and noise is generated during the spraying process ； It interferes with construction workers and the construction environment. Problems with traditional repair equipment cannot be resolved quickly and effectively on-site, resulting in significant time loss during disassembly and installation. The overall costs associated with traditional maintenance, such as labor expenses, equipment transportation, and machining costs, are higher than those of on-site repairs. Moreover, on-site repairs are greatly limited by space constraints, but they offer relatively higher precision. 3. On-site repair of polymer composite materials: (1) Determine the machining standards for the split molds based on the shaft diameter dimensions of the unworn sections at the beginning and end of the worn area (refer to Figure 3). The molds should be made of thick-walled steel pipes, and they should have connection screw holes, positioning pin holes, and discharge grooves on both sides. (2) Run a dry test with the mold to check the fit. (3) Clean the inner surface of the mold with anhydrous ethanol, then apply a release agent in 2 coats, let it dry, and set it aside for use. (4) Bake the worn section with an oxy-acetylene flame to remove the grease that has penetrated the metal surface. Use a angle grinder to grind the repaired area until it shows its original metal color, then clean it thoroughly with anhydrous ethanol. Ensure the surface is clean, dry, and solid. (5) Mix the Fushi Blue 2211F material strictly in proportion, stirring repeatedly until the color is uniform with no color differences. (6) First, apply a thin layer of material on the surface of the worn area, and scrape and press it repeatedly to ensure adhesion. Then, fill the material evenly into the worn section to be repaired. When applying, it should be done evenly and densely, without any pores visible to the eye. (7) Before installing the mold, apply the newly prepared material to the inner wall of the corresponding part of the shaft mold for installation and tightening, in order to achieve the best filling effect and ensure that excess material is extruded from the discharge groove. (8) The material is allowed to cure naturally for 12 hours at 24°C. The curing time can be reduced by heating the mold with an iodine-tungsten lamp or an oxygen-acetylene flame. Be careful not to let an open flame come into direct contact with the material, and the heating temperature must not exceed the material’s maximum tolerance temperature to avoid sudden changes in temperature. (9) After curing, remove the mold. Tools such as saw blades, grinders, files, and sandpaper can be used to remove the excess material extruded from the discharge channel; it is absolutely not allowed to strike the material. (10) Carry out the final assembly strictly in accordance with the assembly requirements. Images of repair cases II. Repair of wear at the bearing seats of the cement rotary kiln idler shafts 1. Brief introduction to the equipment issue Equipment model: φ3.8*48m Equipment problem: Wear at the bearing seats (excessive interference fit with the bearings) Degree of wear: Wear at the bearing seats of the idler shafts; there are 4 such seats, with a wear amount of around 1 mm each ； There are 3 cases of wear and damage to the thrust bearing seats, with a wear amount of 0.2 mm each. Material of components: Carbon steel. Shaft dimensions: The bearing seat for the idler shaft is 380*310 mm, while that for the thrust bearing is 300*130 mm. Rotational speed: 25 revolutions per minute. 2. Analysis of repair processes: Most of the components in production equipment are made of metal. Due to their high strength and hardness, they are subject to vibration, impacts, and other combined forces during operation, which often results in a \"hard-on-hard\" contact between these metal components. Over time, some of these impact-induced deformations become permanent, leading to a decrease in stress recovery capacity and thus wear of the components with relatively lower hardness. However, metals have poor ductility; if this issue is not detected and addressed in time, wear will continue to increase. Traditional repair methods all have certain drawbacks, such as the welding process which causes significant wear; its disadvantage is that it is highly affected by thermal stress, leading to easy deformation of the equipment. For those with uniform wear and low wear amounts, copper gaskets are used for repair, but the degree of fit cannot be guaranteed. After comprehensive evaluation, it was decided to use Fosilan polymer materials (2211F and 803 release agent) as a scale, along with the four-point positioning method, for the repair. 3. Steps for online repair of Fushilan polymer materials: (1) Remove the bearings and clean the worn bearing areas ； (2) Carefully measure the wear condition of the bearing positions, and carefully check the dimensions of the front and rear shaft shoulders against the drawings; use the design repair scales for the front and rear shaft shoulders based on the actual wear conditions on site ； (3) Thoroughly heat the gas cutting torch with oil until no sparks are produced, then clean its surface with anhydrous ethanol ； (4) Determine the positioning support points, and use a calibration ruler to determine the height of these points ； (5) Apply the polymer composite filler to the designated area to repair a positioning strip of sufficient width ； (6) After the positioning strip has cured, it is carefully polished, and measured using an outer diameter micrometer to achieve the required fit dimensions ； (7) Adjust the polymer composite once more, apply it thoroughly and compactly to the worn bearing area to ensure complete coverage ； (8) The bearings are installed using a hot-insertion method, with direct assembly. It can be put into operation once the curing requirements are met. Case Studies of Repairs: III. Conclusion On-site repair is a maintenance approach that has emerged in recent years; its principle involves using polymer composite repair techniques to carry out repairs on-site, without having to remove the damaged equipment or components. The intermolecular forces resulting from the penetration of polymer materials in the repair composite ensure excellent adhesion to the repaired components, satisfying the requirements for the equipment to withstand various combined forces during operation. This method enables emergency repairs and on-the-spot fixes, with repair times that are extremely short. It saves time and effort compared to traditional disassembly and assembly processing methods, and is very suitable for ensuring the continuous operation of industrial production.