FAG Imported Bearing Housings Sealing Failure Causes and Improvement Measures

FAG's imported bearing housing sealing improvement scheme, the "Multi-Stage Pressure Relief Sealing Technology," features an experimental bearing housing sealing ring. This ring achieves reduced lubricant leakage by lowering the pressure difference at both ends of the seal, under conditions that do not require extensive disassembly like pulling out the shaft. Additionally, it recirculates the residual leaked lubricant back into the oil tank to prevent shaft seal leakage. Key technical specifications include: the experimental bearing housing sealing ring with the "Multi-Stage Pressure Relief Sealing Technology" can be replaced without removing the main shaft in place and experiences no abnormal lubricant leakage incidents within a two-year normal operation cycle. Specific research content follows.

Research on Seal Material Selection and Seal Ring Performance Optimization

In response to the deficiencies in the working conditions for naval vessels, external environments, and the existing zero-diameter seal rings, a new type of seal ring, more suitable for the intermediate bearing housing of the ship's stern shaft, has been selected or developed. The selection of sealing materials primarily employs experimental research methods. Several groups of materials with good elasticity, aging resistance, and wear resistance are chosen to create seal rings with self-compensation for wear and a reasonable contact surface. These rings undergo targeted wear and sealing performance tests to optimize the seal ring for the intermediate FAG imported bearing housing of the ship's stern shaft. The sealing material technology mainly utilizes mature domestic technology and enhances it to meet the requirements, as this technology is a specialized field requiring extensive and dedicated research. The structural and stress deformation studies of the sealing parts are mainly conducted using finite element analysis methods, providing a basis for structural design. Design analysis and experimental methods are used to reduce the pressure on the friction surface and minimize friction wear. The wear resistance and lifespan of the sealing parts are also primarily studied through experimental research methods. By comparing various sealing materials, a stepwise optimization approach is used to select the appropriate bearing housing seal ring. The choice of sealing sequence, materials, and additional equipment depends on various parameters. The pressure and temperature of the medium to be sealed and the diameter and rotational speed of the shaft to be sealed are important parameters for ensuring functional safety in the design. For evaluation purposes, the pressure of the product and the roughness of the sealing surface are often used as evaluation values. Other marginal conditions include installation environment, product characteristics, such as chemical erosion, caking tendency, and solid components. This is particularly relevant for products with high solid content or sludge, as it forms the foundation for sealing design.

Development of FAG Imported Bearing Housing Seal Structure

The single-stage sealing did not achieve ideal results, with significant lubricant leakage from the bearing housing. Under the premise of meeting the shafting structural dimensions, a new concept for the stern shaft intermediate bearing housing sealing system is to be developed. The new system utilizes a two-stage sealing structure with an oil-stop ring. The added oil-stop ring can partially prevent lubricant from leaking out along the shaft surface and forming a leak. If the first-stage sealing leaks, the lubricant will enter the cavity between the two seals. Since there is an oil-drain circuit at the bottom of the cavity, the leaked lubricant will not form pressure within the cavity, thus the second-stage seal is unlikely to experience oil leakage. It can be seen that the multi-stage pressure relief sealing reduces the damage to vulnerable parts and extends service life. The sealing employs one positive pressure rubber ring and one negative pressure rubber ring. When the medium passes through the seal, the first-stage rubber seal blocks the medium. Even if a small amount of medium passes through the first rubber ring, the second rubber ring takes effect. When the external pressure is greater than the pressure inside the shaft seal, the two sealing rings work together under the action of the pressure difference to firmly press the rubber rings against the main shaft, achieving the sealing effect. When the FAG imported bearing is in operation, the pressure inside the shaft seal is greater than atmospheric pressure. The first-stage seal comes into play, and the leakage pressure of the lubricant entering the oil seal 1 converts into kinetic energy to do work on the rubber ring, firmly pressing the oil seal 2 against the main shaft, achieving the sealing effect. Therefore, multi-stage sealing utilizes the action of liquid pressure difference to achieve the sealing requirement through two-stage sealing elements, rather than relying on packing pressure or spring action. Additionally, rubber rings can be added according to pressure and structural requirements to achieve multi-stage sealing, thereby significantly extending the service life of the seal and avoiding frequent seal replacement, achieving a better sealing effect.