Because each maintenance personnel has different understanding of excavator maintenance, there are some misunderstandings in the maintenance process. This article will explain the misunderstandings of maintenance personnel on piston and grinding bearing bush in the maintenance process, which is only for reference.
1. Piston open flame heating
Because the piston and piston pin are interference fit, the piston should be heated and expanded before installing the piston pin. Some maintenance personnel will directly heat the piston on an open fire. Such an approach is very wrong. Because the thickness of each part of the piston is uneven, the degree of thermal expansion and cold contraction will be different. Open fire heating will cause uneven heating of the piston, which is easy to cause deformation. Carbon ash will also be attached to the piston surface, reducing the service life of the piston.
If the piston cools naturally after reaching a certain temperature, its metallographic structure will be damaged and its wear resistance will be greatly reduced, and its service life will be significantly shortened.
When installing the piston pin, heat the piston evenly in hot oil to make it expand slowly. Do not heat it directly with open fire.
4. Polish the bearing bush with emery cloth
For some inexperienced repairmen, scraping tiles is a difficult job. As the scraping technology is difficult to master, it is difficult for the bearing bush to meet the technical requirements. Therefore, when replacing the bearing bush, someone polished it with emery cloth instead of scraping the Bush in order to increase the contact area between the bearing bush and the crankshaft. This method is wrong in actual maintenance. Because the abrasive particles on the abrasive cloth are hard, but the bearing bush alloy is soft, so the abrasive particles can easily be embedded into the alloy during grinding. When the diesel engine works, it will accelerate the wear of the journal and shorten the service life of the crankshaft.
