On-site repair methods for shaft wear in water ring vacuum pumps

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【Abstract】An analysis was conducted on the common causes of wear in pump shafts； An explanation and comparison of on-site repair techniques were provided ； It introduces the advantages of on-site repair techniques for polymer composite materials ； 【Keywords】Shaft wear, water ring vacuum pump, shaft head wear repair, on-line repair, tool repair 1. Equipment introduction and problem description Vacuum pumps are common devices in industry; in particular, water ring vacuum pumps are favored due to their simple structure, which facilitates manufacturing and maintenance. Since the gas compression process in a water ring vacuum pump is isothermal, it can be used to evacuate flammable and explosive gases as well as gases containing dust or moisture. Therefore, water ring vacuum pumps are widely used in industries such as papermaking, chemicals, and pharmaceuticals. For a long time, the wear issue in the drive components of vacuum pumps has been difficult to resolve quickly. Although vacuum pumps have a simple structure that makes maintenance easy, achieving rapid on-site repairs during continuous industrial production has always been a challenge. The impeller rotor shaft of the water ring vacuum pump is the source of power for the vacuum pump to perform its functions; once wear occurs on this shaft, it will inevitably lead to the shutdown of the vacuum pump. 2. Analysis of wear causes There are many reasons for wear on the shafts of water ring vacuum pumps, but the main cause lies in the properties of the metal used to manufacture these shafts. Although metal is hard, it has poor ductility (it cannot return to its original shape after deformation), weak impact resistance, and poor fatigue resistance. As a result, it is prone to adhesive wear, abrasive wear, fatigue wear, and fretting wear. Most types of shaft wear are not easily detectable; people only become aware of it when the machine experiences high temperatures, excessive vibration, or unusual noises. By the time this is noticed, most of the shafts have already worn out, leading to machine shutdown. 3. Analysis of repair processes: Shaft wear is a common phenomenon in industrial enterprises, severely affecting their normal production. Traditional repair methods such as patch welding, brush plating, and thermal spraying are difficult to meet the requirements for on-site repairs. To avoid the losses associated with disassembly and repair, companies often resort to using custom-made sleeves as a solution; however, the repair results are not satisfactory. This approach is even ineffective for shaft ends that are severely worn. The main reason is that wear of the shaft head results in an irregularly uneven surface at the worn area, which **reduces** the contact area between it and the non-standard sleeve, leading to linear or even point contact. Under the effects of shocks and vibrations from the equipment, stress concentration occurs, causing further wear of the shaft head. The use of polymer composite materials for online repair is a new technique among the implementation methods; it is a cold welding (bonding) technology. No high temperatures are generated during the online repair process, which effectively protects the equipment itself from damage. Moreover, this method is not limited by the degree of unilateral wear on the shaft. This technology enables rapid on-site repair of wear issues based on the wear dimensions of the vacuum pump shaft, thereby resuming production; generally, the repair is completed within 4-6 hours. Among such repair materials, the 2211F metal repair material offers the most reliable performance. The process and device for repairing worn shafts using the \"mold positioning method\" have been granted a **utility model patent**. 4. Description of the repair process for polymer composite materials 1) Mold processing: Fabricate standard split molds (with bilateral positioning). 2) Surface treatment: degreasing, polishing, and cleaning to ensure the surface is clean, dry, and solid. 3) Mixing materials: accurate proportions and even mixing. 4) Coating material: Ensure the adhesion, filling, and thickness of the 2211F metal repair material. 5) Installing the mold: Fix the mold with its inner surface coated in 803 release agent, to ensure that any excess material is extruded. 6) Demolding: After curing, remove the mold to clean up any excess material. The material should not be struck; it can be removed using tools such as grinders or files to meet the installation requirements. Application Cases: