Detailed Analysis of Common Faults and Repair Methods for Reducers through Multiple Cases

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【Abstract】This paper summarizes several common equipment problems in reducers used in the steel industry, and proposes solutions using polymer composite materials for such issues. Over a decade of continuous practical application has proven that this technology can simply and effectively solve such problems with reducers. The material used in the order is Fushi Blue polymer composite, referred to hereafter as the “material.” Everyone is welcome to share their thoughts and insights! 【Keywords】Steel, reducer, wear, leakage, thread sealing 1. Background of the problem: Reducers are key equipment in the steel industry. It is responsible for transmitting power. Wear and leakage in the bearing housings of reducers, as well as wear and leakage on the input and output shafts, along with leakage at the joint surfaces, are common problems associated with reducers in the steel industry. Such problems usually lead to leakage in the reducer and increased noise, ultimately causing damage to important components such as bearings and gears. This results in equipment shutdown, disrupts normal production activities, and imposes significant economic losses on the company. 2. Common fault causes and analysis: As a key piece of equipment in production, it is very important to ensure the safe operation of the reducer. When abnormalities occur in a reducer, they are generally caused by faults in components such as shafts, bearings, gears, couplings, and the housing. Imbalance is one of the most common faults in reducers. The main causes of rotor imbalance include unreasonable structural design, manufacturing and installation errors, uneven material quality, loosening or detachment of components during operation, etc. Damaged gaskets or O-ring seals at the joint surfaces, loose bolts, as well as excessive impurities and debris in the lubricating oil are also important factors that cause equipment failures. The main manifestations of its faults are as follows: 1) Wear in the bearing chamber of the reducer housing ； 2) Wear of the shaft end of the reducer drive gear shaft ； 3) Wear of the reducer gear shaft journal ； 4) Oil leakage at the coupling surface of the reducer. 3. Comprehensive management of issues related to reducer equipment 3.1 Wear of the reducer’s bearing housing The main reasons for wear of the reducer’s bearing housing (i.e., the outer ring of the bearing coming loose) include: dimensional inaccuracies in the reducer, frequent disassembly and replacement of sealing compounds, etc. These factors cause changes in the fit between the bearing housing and the bearing, which in turn leads to the outer ring of the bearing coming loose and resulting in wear of the bearing housing ； Secondly, inadequate lubrication and cooling of the bearings leads to overheating and seizure of these bearings, causing the outer rings of the bearings to move, which in turn results in increased wear of the bearing housing. On-site repair using polymer composite materials, combined with a positioning repair technique to restore the worn dimensions and appropriate component alignment methods to ensure that the fitted surfaces meet the required standards, enables rapid and effective resolution of issues while satisfying the operational requirements of the equipment. In addition to their excellent physical properties, polymer composite materials possess a \"yielding property\" that metal materials lack, which enables them to effectively address the \"thermal expansion\" issues associated with bearing operation. Application of legend information 3.2 Wear of the shaft ends of the reducer drive gears (keyway damage). The connection between the reducer drive gear shafts and the hydraulic coupler or coupling is usually achieved through keying and an interference fit between the shaft ends. If there is a gap between the key and the keyway, or if there is a gap in the shaft hole, these are all key factors that lead to damage of the keyway as well as wear of the key and the shaft end. At the same time, vibration and impact forces exacerbate the wear problems of keyway rollers and shaft ends. By using this material, minor wear on shaft heads and keyways can be quickly and effectively repaired without the need for disassembly or rewelding. There is no effect from the thermal stress associated with repair welding, and there are no restrictions on the thickness of the repairs. Additionally, the product possesses a ductility that metal materials lack; it can absorb shock and vibrations from equipment, and ensures 100% contact between the mating surfaces, thereby preventing further wear. For cases of severe wear, machining repair techniques can also be employed to achieve optimal fit accuracy. Application of legend information 3.3 Wear of the reducer drive shaft diameter (bearing area). The main factors contributing to wear at the bearing area of the reducer gear shaft (inner ring movement of the bearing) include: the amount of interference between the bearing and the shaft should be appropriate to the load applied; if this interference is insufficient, it will result in inadequate friction between the bearing and the shaft journal, leading to inner ring movement ； Improper axial fixation of the bearing, or issues such as loose fastenings, can cause significant axial movement of the bearing, leading to the inner ring of the bearing shifting ； The quality of the bearing itself and the maintenance during equipment operation are also important factors that cause the inner ring of the bearing to wear out. When the degree of wear is high, applying the polymer composite material 2211F and using machining methods to repair the wear in the bearing area eliminates the effects of thermal stress resulting from welding, and there are no restrictions on the thickness of the repair. When the wear is mild, it is sufficient to create slight dimples; together with the polymer composite material, the component can be assembled directly, which saves time and effort. Moreover, the material’s ability to yield, a property not possessed by metal materials, allows it to absorb shocks and vibrations from the equipment, preventing further wear and the potential failure of the inner ring, thereby **extending the service life of the equipment components, including bearings**. Application of Legend Information 3.4 Leakage at the Joint Surfaces of Reducers: Leakage in the static seals of reducers is a very common phenomenon during equipment operation. The causes of such leakage include a pressure difference between the inside and outside of the reducer, an unreasonable design of the reducer’s structure, excessive oil filling in the reducer, and improper maintenance procedures. The polymer composite material 25551 is used for on-site leakage repair; no disassembly is required – the repair can be carried out directly at the site of the leakage. This approach saves time and effort, and the results are immediate. The material’s excellent adhesion, oil resistance, and good tensile properties enable it to overcome the effects of vibration in reducers, thus solving problems that traditional methods have struggled to address over the years. Application of legend information 4: Improvement measures. If there is slight oil leakage at the dynamic sealing parts during the operation of the reducer, this leakage can be prevented and addressed by adding a super-lubricating sealant. Fushilan Super Lubricating Sealant is a special inert material with multiple uses; as an excellent additive for gearboxes, some of the polytetrafluoroethylene particles in this sealant gather around areas where leaks occur as oil flows, thereby preventing and sealing those leaks. This product can also be used as a threaded sealant; by applying sufficient pressure through pre-tightening, it compresses the surface of the polytetrafluoroethylene particles, causing them to disperse and form a barrier that achieves a sealing effect. For the same reason, the product precipitates on the meshing surfaces of the gears, forming a protective layer with lower friction that shields them from friction and wear, thereby reducing frictional noise. 5. Conclusion: Using polymer composite material technology for on-site repair of the common problems in reducers in the steel industry mentioned above is characterized by simplicity and efficiency. Leveraging the maintenance experience we have accumulated over more than a decade, and addressing these common issues with reducers, we can select appropriate polymer composite materials as well as Fosblue repair solutions based on the equipment parameters and the nature of the damage. Through proper application on-site, these problems can be resolved in a simple and effective manner. It helps enterprises reduce downtime, effectively cut maintenance costs, eliminate potential risks associated with reducers, and ensure the quality of maintenance – thereby securing time and benefits for safe and continuous production.