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Analysis of engine sliding (lubricated) bearings

Analysis of engine sliding (lubricated) bearings

2020-05-20

Analysis of engine sliding (lubricated) bearingsEngine bearing a lot of both bushing bearing shell belongs to the sliding bearing to ensure accuracy of engine operation sliding bearing running clearance requirement is also the reason of engine bearing fault can be caused in the lubrication critical state running clearance to disrupt oil membrane material accurate parts knock against damage to install clean usage can lead to incorrect harmful chemical reactionLiquid static pressure bearing shaft bearing shell with bearing seal types commonly used new technology of precision bearing process between rust bearing life improved test a kind of eccentric shaft processing, a parallel machine tool design theory and key technology of oil-free bearings lead mold industry revolution in bearing life is intensifying test (a) the bearing life is intensifying test (2)

There are many types of plain bearings on an engine, whether bushing or bearing bush.In order to ensure the running accuracy of the engine, the running clearance of these sliding bearings is also very high.The reasons for the failure of engine sliding bearings can be attributed to: lubrication critical state and any interference caused by damage to the running clearance and any material that damages the oil film.For example, improper installation and adjustment, parts with knock against the damage and poor cleanliness, incorrect use methods, harmful chemical reactions, will lead to the damage of sliding bearings.According to the statistics of cummins engine failure analysis, there are four main reasons for the damage of sliding bearings.The percentages of these four aspects in failure are as follows:

1. Damage caused by cleaning is 45%;

2. Damage caused by lubrication is 25%;

3. 15% damage due to use and installation;

4. Damage caused by surface reactions and other factors is 15%.

From this statistical proportion, we can see that the damage caused by cleanliness to the bearings is the main reason.The job of preventing damage due to poor cleanliness is multifaceted: ensuring the cleanliness of the parts when the engine is assembled is only one aspect, and the other is that the engine is in use.Operators and maintenance personnel must be in accordance with the provisions of the correct use of timely maintenance inspection, especially in the long run in the dust and chemical raw materials working environment of the engine, must take measures to prevent the erosion of dust and chemical gas, to ensure the service life of the engine.The alloy layer on the surface of spindle tile and connecting rod tile in the engine is the softest, which can bear the largest load and is also the most vulnerable to damage. Therefore, the surface damage phenomenon of spindle tile and connecting rod tile is analyzed below to avoid repeated failure after repair.

1. Faults caused by cleanliness:

1. Grinding injury caused by small foreign body on bearing bush:

When the oil filter and the engine oil sump oil plug, the first several dozen milliliters of oil out of the oil, the naked eye can see directly and more alloy powder, bearing bush has been worn.This is due to the small particles of impurities into the bearing alloy layer caused by the movement of the surface, while the bearing bush did not cause serious damage, but if this kind of phenomenon continues, not only bearing early damage, shaft can also severely damage, so must be based on the cause of failure in a timely manner to eliminate, avoid to cause the damage of the parts.After troubleshooting, the service life of the engine bearing bush cannot be calculated according to the service time of normal wear, because the abnormal wear amount of a small particle is equivalent to the wear amount of the engine in normal use for 2500 hours.

The reasons for the entry of tiny particles: first, the filtering effect of the air filter is poor or the air intake system is not sealed well. It is necessary to check the pipelines and joints of the air intake system to see if there is any breakage or looseness. At the same time, check whether the filter element is loose or the paper core is broken.It is important to check whether the entire intake system is being repaired or maintained to ensure reliability.Second, after the lubricating oil is polluted, the engine or the oil and the filter element are used for too long, and all the filter elements are blocked, so that the oil on each lubrication surface will enter directly without filtering.Therefore, when filling lubricating oil, it is necessary to pay attention to the cleaning of oil, equip with necessary filtration machines, and replace the lubricating oil and filter element in time according to the usage regulations.Third, the fuel oil supply is too large combustion, nozzle leakage, resulting in fuel oil infiltration into the crankcase, and some impurities with the fuel oil into the crankcase and oil mixed together to reduce the lubrication effect.Therefore, in the use of the engine should pay attention to observe the engine exhaust and operation, if there is an abnormal to find out the reason for repair or replacement in time.Fourth, when the engine is assembled, the cleanliness of the internal parts is poor.In the repair and maintenance of the engine, must pay attention to the cleaning of parts, installation should pay attention to prevent re-pollution, to ensure the internal cleanliness after installation.

Either way, the engine oil and filter must be changed after troubleshooting.After repair of engine starting idle running two hours stop for inspection, there are no alloy powder in the oil, may use in half load, but in the first few days of use must be observed, after 60 ~ 120 hours operation decision after confirm the abnormal wear and tear is completely ruled out, oil change again, the engine can be put into normal use.If abnormal wear continues to develop, use must be discontinued for disintegration inspection and repair.

2. Damage to bearing bush caused by large particle foreign body and poor quality lubricating oil:

The shaft and bearing bush have been seriously damaged when larger alloy blocks or flakes are found in the oil filter element and the engine oil sump. It must be stopped immediately for disassembly and repair. If continued use, more parts will be damaged.

Larger particles into the reason: when installation parts not clean, such as, the connecting rod bushing hole processing scrap metal remaining in the connecting rod oil passage, parts and oil passage with cutting or silt, not completely clean before installation, or related to sports surface machined part machining burrs flanging is not clear, installing a bearing with large particles of foreign matter or shaft surface is damaged.These phenomena are very serious damage to the bearing bush.So in the maintenance of the installation to carefully clean up and check.

Inferior oil lubrication effect and thermal effect can not meet the requirements, make the bearing and shaft wear, sports surface damaged bearing alloy melting and high temperature, at the same time, inferior oil impurities more oil filter was quickly blocked, lubricating oil containing impurities without direct filtration, the surface of the movement to further accelerate the damage of the shaft and bush.So when buying and changing lubricating oil must strictly control the quality of lubricating oil according to the regulations, according to the regulations to choose lubricating oil.

3. Damage to the shaft and bearing bush caused by non-moving foreign bodies:

If there is a large foreign body sandwiched between the bearing bush and the inner wall of the mounting hole of the bearing bush, the moving surface of the bearing bush will produce convex points. When the shaft is running, abnormal wear will start from the convex points and extend to the periphery, causing early damage to the shaft and bearing bush.If there is a large foreign body between the moving surface of the bearing bush and the shaft, it will be embedded in the alloy layer of the bearing bush after installation. During operation, the shaft will be damaged and the bearing bush will be damaged at the same time.Shaft and tile and installation hole and other relevant parts such as bump bump will cause damage or damage to the shaft and tile.

Causes and prevention: the shaft, bearing bush, bearing bush hole (body, connecting rod) corroded to produce oxide or sediment, check and clean carefully before installation, especially the oil channel and tubing cavity;The installation site must be away from the site with dust and debris splashing;Clean the tools used for installation and take necessary protective measures to avoid re-contamination. At the same time, clean the lubricating oil used in assembly to prevent dust from mixing.The storage and installation of shaft and bearing bush as well as bearing bush hole shall not be in contact with any metal object and shall not have any bumping operation.


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