Fault mechanism of bearing
1. Fault mechanism of bearing.
Bearings are common in most mechanical equipment, with high Bearing Failure utilization rate and high damage rate. Bearing has many advantages such as good starting performance, high reliability and convenient maintenance.
It is widely used in mechanical equipment. When the equipment is in the state of constant speed, the Bearing Failure bearing has high bearing capacity and long-term stress, resulting in the bearing is prone to failure compared with other parts. Among all kinds of mechanical failure types, bearing failure accounts for a large proportion.
In contrast, the radial dimension of the rolling bearing is larger than that of the sliding bearing, and the Bearing Failure damping capacity is relatively poor. When the mechanical equipment is at high speed, the service life of the rolling bearing is lower than that of the sliding bearing, and the noise is also relatively high.
The main function of the radial bearing is to bear the radial force, which consists of four parts, namely, the inner ring, the outer ring, the rolling element and the rolling element cage. The inner ring is tightly sleeved on the journal and rotates Bearing Failure synchronously with the shaft, while the outer ring is in the bearing seat hole.
When the inner and outer rings make relative rotation, the rolling will roll on the raceway of the outer circumference of the inner ring and the inner circumference of the outer ring. In order to prevent friction, the cage separates the two. In most cases, the reason why the bearing has problems is mainly due to the Bearing Failure looseness of sealing shaft sleeve, fixing bolt and other parts during operation,
resulting in the wear of rolling element and rolling element cage, or there are gaps in bearing gland and shaft Bearing Failure sleeve, impurities such as water or dust enter the bearing box from these gaps, and the lubricating oil becomes dirty, resulting in poor lubrication, which eventually leads to bearing failure.
2. Bearing damage.
Under normal circumstances, as long as it is used normally, the bearing can be used until the fatigue life. Bearing failure is called bearing failure when the bearing is not durable, premature damage and relatively early damage of fatigue life.
The reason is that the bearing failure is generally due to the failure to pay attention to the lubrication of the bearing during installation or use, resulting in the intrusion of foreign matters from the outside, or poor lubrication caused by the thermal influence of the bearing shell, resulting in premature damage.
3. Common faults of bearing.
（1）. Bearing discoloration. When the bearing operates under continuous high temperature, it will produce black or blue. The main reasons for bearing discoloration are: the lubrication in the bearing does not meet the technical requirements; Dirt or impurities invaded during bearing installation;
The fit of the bearing with the journal and shaft hole is loose, resulting in sliding friction between the inner and outer rings of the bearing; The non concentricity between the bearing seat hole and the journal leads to abnormal effects on the bearing during operation;
The bearing operates its own designed bearing capacity due to overspeed or overload operation; The axial clearance of the round cone roller bearing is small, and the bearing has large friction with the sealing device, washer and bushing.
（2）. The inner and outer rings of the bearing are cracked. There are different degrees of cracks on the inner ring and outer ring of the bearing, mainly due to: defects in the quality of the bearing or defects in the steel used by the bearing;
The shaft bears large external impact load; When installing and removing the bearing, the bearing bears the direct beating of iron, resulting in cracking of the inner and outer rings of the bearing; The inner ring, outer ring, seat hole and Journal of the bearing are poorly matched, resulting in uneven stress on the raceway and cracks on the inner ring and outer ring.
（3）. The bearing is rusted. The sealing device of the bearing fails, resulting in external dirt or moisture entering the bearing, resulting in corrosion of the bearing.
（4）. Broken balls or rollers. Because the installation clearance of the bearing ball or roller is too small, the bearing is subjected to severe impact during use, and the lubricant is mixed with iron filings and other hard substances, resulting in the breakage of the ball or roller.
（5）. Pit scar on raceway. The bearing bears external strong impact load or the raceway exceeds the stress design standard due to poor lubrication, resulting in pit scars.
(6) The bearing rotates laboriously. The running speed of the bearing is slow, and it cannot rotate or rotates laboriously by hand. This is mainly because the bearing is not cleaned, and the matching pores of the bearing journal, inner ring or outer ring are too small, resulting in bearing deformation or large force, which eventually leads to laborious operation.
1. Bearing maintenance.
In case of bearing failure in mechanical equipment, when disassembling the bearing for maintenance, record the appearance of the bearing, check the residual amount of lubricant in the bearing, sample and save the lubricant, and select kerosene or gasoline to simply clean the bearing.
Clean the disassembled bearing, first conduct rough cleaning, and then conduct fine cleaning. Place the bearing on the container and place the metal mesh as the bottom to prevent the bearing from directly removing the dirt at the bottom of the container. During rough cleaning, the bearing shall not rotate with dirt to avoid damaging the rolling surface of the bearing.
After removing the adhesive and grease with a brush, enter the fine washing step. Place the bearing in the cleaning oil and clean it while rotating. When the cleaning oil is dirty, replace it in time to ensure the fine cleaning effect. In order to judge that the disassembled bearing can continue to be used, it is necessary to check after bearing cleaning.
The inspection items of the bearing include: bearing foreign matters, bearing clearance, bearing dimensional accuracy, bearing frame wear, mating surface status, rolling surface status, raceway surface status, ball or roller operation status, etc.
For non separable small ball bearings, use one hand to level the inner ring of the bearing, and confirm whether the bearing can run smoothly by rotating the outer ring. For round cone roller bearings, the raceway surface and rolling element of the outer ring shall be inspected.
2. Bearing maintenance and precautions.
(1) Bearing installation.
In the process of mechanical maintenance, bearing maintenance has high requirements for installation. Since the bearing does not have obvious external characteristics in appearance, it can be installed in either forward or reverse direction, which is extremely easy to reverse installation.
In the process of bearing assembly, maintenance personnel are required to have a full understanding of the structure and installation requirements of the bearing, be familiar with the technical points, and install correctly according to the design requirements. The installation of tapered bearing includes “back-to-back” and “face-to-face” installation methods.
If the installation error will lead to axial movement and can not be adjusted; If there is a lack of understanding of the structure and installation of the bearing, it is easy to install reversely when facing the tight ring and loose ring of the plane bearing, resulting in the failure of normal operation after assembly and greater failure of mechanical equipment.
(2) Bearing defects.
In the process of mechanical maintenance, fully understand the technical index information such as bearing code and model of the equipment, try to rotate the original model as much as possible, and avoid using alternative models.
In practical work, some equipment often replace bearings, and the replaced bearings are very easy to burn out, which is usually directly caused by the difference of bearing models, the use of substitute bearings and the quality defects of bearings themselves.
Due to the uneven quality of the bearings sold in the market, there is a phenomenon of shoddy bearing parts. The long-term use of low-quality bearing parts causes long-term wear and tear to the mechanical equipment and reduces the service life of the equipment.
During mechanical maintenance, the rotating bearing shall avoid rotating the accessories in long-term inventory. At the same time, the bearing shall be visually inspected and the function shall be tested to ensure the bearing quality.
The bearing plays an important role in the normal operation of the machine. By maintaining lubrication, avoiding the immersion of foreign matters and overload and overspeed operation, the service life can be prolonged. During bearing maintenance, the causes of damage shall be analyzed and targeted measures shall be taken to ensure maintenance quality and improve equipment operation efficiency.