Babbitt thrust bearing upper and lower shoe flat arc surface
Materials used for thrust shoes: billet Babbitt (also known as Wujin). Wujin can melt when the shaft temperature reaches around 110 degrees Celsius, increasing the displacement space of the shaft, thereby protecting the shaft and preventing dry friction of the thrust shoes due to large axial displacement. Other materials include tin bronze, billet fluoroplastic (this material has a low friction coefficient, is suitable for higher temperatures, does not require scraping of the shoe, and will not burn the shoe due to oil cutoff), etc. Thrust shoes must operate under oil lubrication conditions, ensuring that the minimum oil film thickness at the oil outlet edge meets the design value (e.g., for large units, the oil film thickness of thrust shoes is generally between 0.03 and 0.07 mm). This requires the mirror plate to have high precision and low roughness. If the mirror plate has high roughness, the bearing friction loss increases. If the mirror surface has defects such as scratches or corrosion, it may damage the oil film and even cause a shoe burning accident. Therefore, mirror plate grinding, thrust shoe scraping, and the maintenance and adjustment of the mirror plate and thrust shoes are very important. Additionally, the mirror plate must ensure its waviness, with parallelism generally around 0.02 mm per meter depending on the unit, and the height difference between thrust shoes is generally controlled within 0.02 mm, meaning the flatness of the thrust shoes must be similar to that of the mirror plate. If the flatness of the mirror plate and thrust shoes is poor, and the deviation exceeds the minimum oil film thickness, it will damage the oil film established between the thrust shoes and the mirror plate. The thrust shoes will then operate under semi-dry or dry friction conditions, leading to shoe burning accidents or shoe surface damage. Furthermore, the force on the thrust shoes is directly related to their parallelism. Only with a large contact area can the thrust shoes withstand greater pressure. If the thrust shoes are uneven with localized high points, force concentration may occur, leading to shoe burning accidents or severe wear of the shoe surface. Only by ensuring that the thrust shoes have good flatness and excellent contact with the mirror plate, and by guaranteeing that an oil film is quickly established between the thrust shoe surface and the mirror plate during unit startup and maintained without destruction during operation, can the thrust bearing's stability and operational safety and reliability be ensured.