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The reasons for the early damage of sliding bearings

Update:21-10-2020
Summary:

1. Early damage caused by particulate matter 1) Early b […]

1. Early damage caused by particulate matter

1) Early bearing damage caused by small particles and foreign matter

It is caused by the entry of tiny particles into the moving surface of the bearing alloy layer. Although it did not cause serious damage to the bearing, if this kind of phenomenon continues to develop, it will not only cause early damage to the bearing, but also severe damage to the shaft. Eliminate the cause of the failure in time to avoid damage to the parts.

The reasons for the entry of fine particles include: (1) The air filter has a poor filtering effect or the air intake system is not well sealed; (2) The lubricating oil is contaminated and added to the engine or the oil and the filter element is used for too long. The oil on the lubricating surface enters directly without being filtered; (3) Excessive fuel supply and insufficient combustion, nozzle leakage, causing fuel to seep into the crankcase, and some impurities with the fuel enter the crankcase and mix with the oil to reduce the lubrication effect; ⑷When the engine is assembled, the cleanliness of internal parts is poor.

2) Larger foreign matter and inferior lubricating oil cause early bearing damage

When alloy blocks or flakes with larger particles are found in the oil filter element and the engine oil pan, the machine must be shut down immediately for inspection and repair. If it continues to be used, more parts will be damaged. The main reason for the entry of larger particles is that the parts are not cleaned during installation. For example, the metal chips generated during the processing of the inner hole of the connecting rod bushing are stored in the connecting rod oil passage, and the parts and the oil passage are stuck with chips or silt, etc. Therefore, clean and inspect carefully when repairing and installing.

Poor quality lubricating oil contains many impurities, which can easily block the oil filter element, causing the lubricating oil to directly enter the moving surface without filtering, further accelerating the damage of the shaft and bearing. Therefore, when buying and replacing lubricating oil, the lubricating oil must be strictly controlled according to regulations. The quality of the oil is selected according to the regulations.

3) Do not move foreign objects to cause early damage to shafts and bearings

If there is a large foreign body sandwiched between the bearing and the inner wall of the shoe mounting hole, bumps will be generated on the moving surface of the bearing. When the shaft is running, abnormal wear will start from the convex point and expand to the periphery, causing early damage to the shaft and the bearing; if there is a large foreign body between the moving surface of the bearing and the shaft, the alloy of the bearing will be embedded after installation In the layer, while the shaft is damaged during operation, the bearing is also damaged; if the shaft, bushing and mounting holes and other related parts hit the bumps, the shaft and bushing will be damaged or damaged.

Before installation, check and clean carefully, especially the oil passage and the inner cavity of the tubing; the installation site must be far away from dusty and debris splashing sites; the tools used for installation must be cleaned, and necessary protective measures must be taken to avoid re-contamination. At the same time, the lubricating oil used in the assembly should be clean to prevent dust from entering; the storage and installation of shafts, bearings and bearing holes should ensure that they do not come into contact with any metal objects and do not have any bumping operations.

 

 

2. Early damage caused by the lubrication system

If the lubricating oil fails or the pressure does not meet the requirements, the moving surface will completely lose the protection of the oil film and directly contact for dry friction. As the temperature rises, the alloy layer of the bearing melts, and the timely shutdown will cause the phenomenon of "shingling", and the failure to shutdown in time will cause more serious damage to the parts. The main reasons for this situation are: the oil level is too low or the lubricating oil passage is ruptured; the oil suction filter, oil passage, and oil hole are blocked; the oil pump is worn or the suction pipe is leaking; the pressure regulating valve and the pressure limiting valve are damaged ; The engine idling operation time is too long; after the engine is started, it will directly perform high-speed operation and full-load operation without warming up. After full-load operation, the engine will be stopped without cooling down during low-speed operation under no-load conditions when the temperature is high. The internal heat deposits and the temperature rises; the standard oil is not selected and the oil is changed regularly.

3. Early damage caused by incorrect use

When the engine is idling, the speed is low, and the oil supply of the oil pump is small, causing slight dry friction between the bearing surface of the bearing and the shaft, causing damage to the alloy layer surface of the bearing. At the same time, wear debris is generated to accelerate the wear and damage of the shaft and the bearing. ; Therefore, when the engine is idling for a long time, it runs at a temperature lower than the normal operating temperature, and the fuel injected into the combustion chamber cannot be completely burned. Part of the unburned fuel flows into the crankcase along the cylinder wall, destroying the oil film of the lubricating oil , Reduce the lubrication effect.

In addition, after the engine has been working under heavy load for a long time, the internal parts are at the highest operating temperature, especially the combustion chamber is at high temperature. After the engine stops running, the cooling system and lubrication system stop working, and the heat cannot be dissipated. The temperature of related parts increases, which destroys the oil film on each lubricating surface. When restarting, when the oil film on each lubricating surface has not yet formed, abnormal bearing wear has occurred. In particular, the damage to the sliding bearing of the turbocharger is more serious. At the same time, too high temperature will cause the shaft hole to deform, destroy the operation accuracy and accelerate the engine damage. The occurrence of this phenomenon will cause serious damage to the piston, cylinder liner and cylinder liner sealing ring. Therefore, after the engine has been working with a large load for a long time, the engine should be operated at no-load, medium and low speed for more than 10 minutes, and the internal temperature should be reduced. Downtime.

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