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Causes and types of bearing failures

Release time: 2022/04/29

The fault mechanism of bearings

1. Common faults of bearings.

(1) bearing discoloration. When the bearing runs at a continuous high temperature, it will produce black or blue color. The main reasons for bearing discoloration are: smooth bearing does not fit the technical requirements; Dirt or impurities in the process of bearing installation; Bearing, journal, shaft hole fit more loose, resulting in sliding friction bearing inner and outer ring; The different center between the bearing seat hole and the journal, resulting in abnormal bearing operation; Bearing due to overspeed or overload operation, operation itself designed bearing capacity; The axial clearance of cylindrical roller bearings is smaller, bearing and seal installation, gaskets and bushings produce greater friction.

(2). Cracks appear on the inner and outer rings of the bearing. On the inner and outer rings of bearings, cracks at different levels are mainly caused by: defects in bearing quality or defects in the inner steel used by bearings; The shaft receives a large impact load from the outside; When installing and disassembling the bearing, the shaft receives direct beating from the iron, resulting in cracking of the inner and outer ring of the bearing; The bearing inner ring, outer ring, seat hole and journal are not well matched, resulting in uneven force on the raceway, and cracks on the inner ring and outer ring.

(3). Bearing corrosion. Bearing seal installation failure, resulting in external dirt or water into the bearing, resulting in bearing corrosion.

(4) Ball bearings or rollers are broken. Because the clearance of the bearing ball or roller device is too small, the bearing is subjected to violent impact in the process of use, and the smooth agent is mixed with iron filings and other hard substances, resulting in the crushing of the ball or roller.

(5) The raceway shows pit scars. The shaft receives external impact load or due to poor smoothness, the raceway exceeds the force design specification, resulting in pit scar.

(6) Bearing rotation is laborious. Bearing running speed is slow, hand rotation can not rotate or rotate hard, this is mainly due to the bearing is not cleaned clean, bearing journal, inner ring or outer ring with pore is too small, resulting in bearing deformation or large force, eventually resulting in operation effort.

2. Fault mechanism of bearings.

Bearing is more common in most mechanical equipment, has a high utilization rate, but also has a high damage rate. Bearing has many advantages such as good starting performance, high reliability and easy maintenance, which are widely used in mechanical equipment. Bearing in the equipment is in the same speed state, has a high bearing capacity, long-term force action, resulting in bearing relative to other parts, it is easy to attack faults, in all kinds of mechanical fault types, bearing faults occupy a large proportion.

Rolling bearing, by contrast, is greater than sliding bearing radial size and vibration to match, machinery and equipment under a state of high speed rolling bearing to less than the life of the sliding bearing, noise also compare high, main function is to accept the centripetal bearing radial force, its composition includes four local, namely, inner and outer ring, rolling body and rolling body insist on rack. The inner ring is tightly set on the journal and rotates synchronously with the shaft, while the outer ring is in the bearing seat hole. When the inner and outer rings rotate relatively, the roller will roll on the raceway of the outer and inner rings of the inner ring, and the two will be separated by a stick rack to avoid friction. Bearing is most situations can present problems, is mainly due to the operation in the process of sealing shaft sleeve and a fixed bolt loose parts, forming roller and roller stick to wear, or bearing gland, shaft sleeve, etc have crack, the impurities such as water or dust from these gaps in smooth oil dirty bearing box to form smooth, eventually cause bearing fault.

3. Bearing damage.

Under normal conditions, only normal use, bearings can be used until the fatigue life. Bearing presents early damage of no durability, premature damage and fatigue life, which is called bearing fault. Investigate the reason, bearing faults are generally due to the device or use of not paying attention to the smooth bearing, resulting in foreign body invasion from the outside, or caused by the thermal effect of the bearing shell smooth bad, so as to early damage.

Bearing maintenance in mechanical maintenance

1. Maintenance of bearings.

In mechanical equipment, when the bearing is faulty, the appearance of the bearing should be recorded when the bearing is disassembled and stopped for maintenance, the residual stock of the smoothing agent inside the bearing should be checked, and the smoothing agent should be stopped for sampling storage, and the simple cleaning of the bearing should be stopped by kerosene or gasoline.

Clean the disassembled bearings, stop rough cleaning first, and then stop 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. When stopping rough cleaning, it is necessary to prevent the bearing from rotating together with dirt to prevent damage to the bearing rolling surface. Apply the brush to remove the sticky matter and smooth grease before entering the fine washing step. The bearing is placed in the cleaning oil and cleaned while rotating. When the oil is dirty, it should be changed in time to ensure the fine cleaning effect. In order to determine that the disassembled bearings can continue to be used, the inspection needs to be stopped after the bearing cleaning is completed. The inspection items of bearings include: bearing foreign body, bearing clearance, bearing dimensional accuracy, bearing frame wear, mating surface state, rolling surface state, raceway surface state, ball or roller running state, etc. About non-separation small ball bearings, the inner ring of the bearing should be flat with one hand, and the outer ring should be rotated to confirm whether the bearing can run smoothly. Stop checking the raceway surface and rolling body of the outer ring for circular cone roller bearings.

2. Bearing maintenance and matters needing attention.

(1) Bearing itself defects.

In the process of mechanical maintenance, it is necessary to have a full understanding of the technical index information such as the bearing code and model of the equipment, and try to rotate the original model to prevent the use of alternative models. In practical work, some equipment often change bearings, and the changed bearings are very easy to present the phenomenon of burning out, which is usually caused by the difference in the type of bearings, the use of substitute bearings, and the quality defects of bearings themselves. Due to the uneven quality of bearings sold on the market, there is a phenomenon of shoddy bearing accessories, the long-term use of inferior bearing accessories, the formation of long-term wear of mechanical equipment, reducing the service life of equipment. Mechanical maintenance, rotating bearings to prevent rotation of long-term inventory of accessories, at the same time to stop the bearing appearance inspection, the function of stop testing, in order to ensure the quality of bearings.

Bearing plays a serious role in the normal operation of machinery. After insisting on smooth operation, preventing foreign body immersion and overloading, it can prolong the service life. When maintaining bearings, it is necessary to analyze the cause of damage, take targeted measures to ensure the maintenance quality and improve the operation efficiency of equipment.

(2) Bearing device.

In the process of mechanical maintenance, bearing maintenance has a higher request to the device. Because the bearing does not have obvious external characteristics in appearance, both forward and reverse can be installed, and it is extremely easy to present the phenomenon of reverse installation. In the bearing assembly process, the request maintenance personnel has a full understanding of the bearing structure and device request, familiar with the safety technical points, according to the design request, the correct device. Tapered bearing device includes "back to back" and "face to face" device method, if the device error solution results in axial movement and can not stop adjustment; If there is a lack of understanding of the structure and installation of bearings, it is easy to install reverse when facing the tight ring and loose ring of flat bearings, which leads to the normal operation after assembly, and causes more problems of mechanical equipment.