What are the causes of bearing consumption on the engine？

The plain bearings used in the engine are usually divided into two kinds: one is a thin-wall bearing with lining, which is shaped like a tile and is commonly known as a bearing 

shell; The other is the bushing, also known as the copper bushing, the shape of a hollow cylinder. The thin-wall bearing is mainly used to support the crankshaft and connecting 

rod of the engine; Bushing is mainly used to support camshaft journal and piston pin.

Early damage forms and preventive measures of thin wall bearing (bearing bush).

The form of early damage: in the normal use of bearings, due to gradual wear until finally losing the ability to work and ending its service life, this natural damage is difficult to avoid. However, if the bearing is prematurely worn or damaged due to improper engine assembly adjustment, poor lubricating oil quality or poor use conditions, it is an early damage caused by humans. Early damage not only greatly reduces the service life of the bearing, but also affects the normal operation of the engine. According to the 

long-term experience of diesel engine maintenance, the common forms of early damage of plain bearings are mechanical damage, bearing cavitation, fatigue pitting, corrosion and so on.

(1) Mechanical damage: sliding bearing mechanical damage refers to different degrees of grooves on the alloy surface of the bearing, serious metal stripping on the contact 

surface and a large area of messy scratches; In general, contact surface damage and ablative phenomena exist simultaneously. The main cause of bearing mechanical damage is 

that the bearing surface is difficult to form an oil film or the oil film is seriously damaged.

(2) Bearing cavitation: Under the repeated action of the sliding bearing in the cylinder pressure impact load), the surface layer has plastic deformation and cold hardening, the 

local loss of deformation ability, gradually formed a grain and continued to expand, and then with the grinding debris off, the load surface layer formed cavitation. When the bearing bush cavitation occurs, the pits first appear, and then the pits gradually expand and cause the cracking of the alloy layer interface, and the cracks expand along the 

parallel direction of the interface until the spalling. The main reason for the cavitation of plain bearings is that the oil flow is strongly disturbed due to the sudden change of 

the transverse section of the structural elements such as oil groove and oil hole, and bubbles are formed in the vacuum area of the oil flow disturbance, and then cavitation 

occurs due to the rise of pressure and bubble collapse. Cavitation generally occurs in the high-load area of the bearing, such as the lower bearing of the main bearing of the 

crankshaft.

(3) Fatigue pitting: bearing fatigue pitting means that due to the overload of the engine, the bearing is overheated and the bearing clearance is too large, resulting in fatigue 

damage, fatigue pitting or fatigue shedding in the middle of the bearing. Most of this damage is caused by overload, bearing clearance is too large, or the lubricating oil is 

not clean, and there are foreign bodies mixed in. Therefore, when using, attention should be paid to avoid bearing overload work and not to run at too low or too high speed; 

When idling, the engine should be adjusted to a stable state; Ensure normal bearing clearance to prevent engine speed from being too high or too low; Check and adjust the 

working condition of the cooling system to ensure that the working temperature of the engine is appropriate.

(4) Bearing alloy corrosion: bearing alloy corrosion is generally the area of lubricating oil is not pure, the chemical impurities (acid oxides, etc.) in the lubricating oil to oxidize 

the bearing alloy and generate acidic substances, causing the bearing alloy part to fall off, forming irregular small holes or small pits. The main reasons for the corrosion of 

bearing alloys are improper selection of lubricating oil, poor corrosion resistance of bearing materials, or rough engine work and high temperature.

(5) Bearing melting: there is a small raised metal surface direct contact between the journal and the bearing friction pair, forming a local high temperature, in the case of 

insufficient lubrication and poor cooling, making the bearing alloy black or local melting. This fault is often caused by too tight match between the journal and the bearing; 

Insufficient lubricating oil pressure is also easy to burn the bearing.

(6) Bearing outer circle: bearing outer circle is the relative rotation of bearing in the seat hole. After the bearing is rounded, it not only affects the heat dissipation of the 

bearing, which is easy to ablate the alloy on the inner surface of the bearing, but also damages the back of the bearing, and burns the bearing in serious cases. The main 

reasons are that the bearing is too short, the tenon is damaged, and the processing or installation does not meet the specifications.