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How bushing works as a seal and wear protection for mechanical parts

Update:28 Dec 2019
Summary:

Bushing is a matching piece used outside the mechanical […]

Bushing is a matching piece used outside the mechanical parts to achieve sealing, wear protection, etc. It refers to a ring sleeve that acts as a gasket. In the field of valve applications, the bushing is inside the valve cover, and generally anti-corrosive materials such as polytetrafluoroethylene or graphite are used for sealing.
In the moving parts, the parts are worn due to long-term friction. When the clearance between the shaft and the hole wears to a certain extent, the parts must be replaced. Therefore, the designer chooses a lower hardness and better wear resistance when designing. The material is a shaft sleeve or a bushing, which can reduce the wear of the shaft and the seat. When the shaft sleeve or the bushing is worn to a certain extent, it can be replaced, which can save the cost of replacing the shaft or the seat.
Generally speaking, the bushing and the seat adopt an interference fit, and the shaft adopts a clearance fit. Because wear is unavoidable in any case, it can only prolong the life, and shaft parts are relatively easy to process; there are also some new ones. Designers do not like this design. They think that it is an increase in cost during manufacture, but after a period of use, it is still necessary to modify this method during maintenance. However, the modification is likely to cause the accuracy of the equipment to decrease. The reason is simple. Secondary processing It is not possible to supplement the position of the center of the seat hole. The bushing is used in place of rolling bearings (such as camshafts) in places where the rotation speed is low, the radial load is high, and the clearance requirements are high. Bearing), the material requires low hardness and wear resistance. The inner hole of the shaft sleeve is ground and scraped to achieve high matching accuracy. There must be an oil groove on the inner wall. Lubrication of the shaft sleeve is very important. If the shaft is dry ground, the shaft and shaft The sleeve will soon be scrapped. It is recommended to scrape the inner hole wall of the sleeve during installation, so that many small pits can be left, and the enhanced lubrication bush and the sleeve are roots. Different models use different mining conditions. The main conditions are: pressure, speed, pressure-speed product, lubrication state, and load properties. Bushing Kuaiyiyou automatic selection is included.
The valve stem is worn and can be easily replaced. If the bushing is not used, the parts are replaced after wear. Therefore, it is replaced by a replacement bush (during the design, the hardness of the bush is reduced so that it becomes a wear part in the friction pair). Because it is easy to process, the replacement cost is low, and it is easy to replace. Of course, there is guidance, etc., which is secondary.