Self-aligning ball bearing failure cause and operation check work points and daily maintenance skills

After the TIMKEN bearing is installed, check the operation in order to check if the installation is correct. The small machine can be rotated by hand to confirm whether the rotation is smooth. The inspection items have poor operation due to foreign matter, scratches, and indentations. The installation is poor, the torque generated by the mounting is not stable, and the torque is too large due to too small clearance, installation error, and sealing friction. Wait. If there is no abnormality, the power running can be started.
Large machinery cannot be rotated manually, so the power is cut off immediately after the start of the no-load, the machine is idling, and the presence or absence of vibration, noise, and contact of the rotating parts is checked. After confirming that there is no abnormality, the power is turned on.
The power running starts from the no-load low speed and slowly increases to the rated operation of the specified conditions. The items to be checked during the test run are whether there is abnormal sound, change in the temperature of the self-aligning ball bearing, leakage or discoloration of the lubricant, and the like. If an abnormality is found, stop the operation immediately, check the machine, and remove the bearing check if necessary.
TIMKEN bearing temperature can generally be estimated based on the external temperature of the bearing housing. However, it is more accurate to directly measure the temperature of the outer ring of the bearing by using the oil hole. The bearing temperature gradually rises from the start of the operation, and the temperature is usually stable after 1 to 2 hours. If the bearing is poorly installed, the temperature will rise sharply and an abnormally high temperature will occur. The reasons are such as excessive lubricant, too small bearing clearance, poor installation, excessive friction of the sealing device, and the like. In the case of high-speed rotation, the selection of TIMKEN bearing structure and lubrication method is also the cause.
The rotation sound of TIMKEN bearings is checked with a stethoscope, etc., and there are strong metal noise, abnormal sounds, irregular sounds, etc. to explain abnormalities. The reasons are poor lubrication, poor accuracy of the shaft or housing, bearing damage, and foreign matter intrusion.
The surface of the steel under transient high temperature acts on the oxygen in the air and rises into a very thin (20-30 nm) thin layer of iron oxide. It is worth noting that the thickness of the oxide layer is corresponding to the test results of the total thickness of the surface-grinding metamorphic layer. This shows that the thickness of the oxide layer is directly related to the grinding process and is an important indicator of the quality of the grinding.

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The importance of proper use of lubricants for the operation of SKF bearings

Of course, if the operating speed of the imported bearings is very low and it is necessary to work in a polluted and humid environment, it is best to fill the SKF housing with grease.
The standard products offered are more than 20,000 types of bearings. In addition to rolling bearings, the Group also manufactures linear bearings, plain bearings, bearing housings, ball and roller screws, textile machinery components, retaining rings, machine tools and various precision mechanical components. With extensive experience in these areas, he has the knowledge and expertise to develop, manufacture and apply a wide range of advanced engineering products. Smaller such as micro-bearings weighing only 0.003 grams, up to each of the thirty-four tons of giant bearings. In addition, a series of bearing repair tools, grease and bearing monitoring instruments (bearing heaters, pullers, etc.) are also available, in order to achieve higher efficiency for bearing users and achieve worry-free operation.
Bearings are precision components, SKF bearings and grease contaminated, will not operate. Bearings In addition, at least 14% of all contaminations that have been sealed with grease are maintenance-free. Only a small portion of all bearings failing early is significantly affected by the use of bearings. Bearings have excellent manufacturing and design capabilities to provide a wide range of harsh working condition sealing solutions.
The grease chemically reacts with the oxygen in the air to produce an acidic substance. It first consumes the antioxidant additive in the fat, but to a certain extent, the organic acid formed will corrode the metal component and destroy the structure of the fat to make it drop. Decrease, increase in viscosity of base oil, and deterioration of fluidity. A large number of tests have shown that the higher the temperature, the more pronounced the decline in grease life. For example, when the temperature is between 90 and 100 degrees, the life of the grease is reduced by about half for every 19 degrees of temperature increase. At 10 to 150 degrees, the fat life will be reduced by half for every 15 degrees of temperature increase.
In addition, moisture, dust, and harmful gases in the environment in which the grease is used are also important factors for deterioration. For example, the wear of particles such as copper, iron, lead and bronze in the grease will catalyze the oxidation of the fat. In short, there are many reasons for the failure of grease, sometimes it may be caused by a certain cause, but more is the result of multiple factors acting together, or a breakthrough for one reason, and then other reasons work together.

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Principles and functions of grease in NTN bearings

Our customers always have some improper use methods when using all kinds of NTN bearing grease. Today we will explain the principle and function of the grease in the bearing.
  1. Principle of use of grease
Everyone is a liquid solution that is a very thick solution. This grease is composed of a reticulated soap fiber whose structure determines that it can adsorb a large amount of lubricating oil and make it work properly. But as you can imagine, if a sponge is squeezed, the water will flow out. Grease is also squeezed out of the lubricating oil, but the grease in the NTN bearing is rarely directly squeezed and drained, because a freshly lubricated imported bearing is moving in the inner space of the bearing during running. Its main working principle is "temperature".
  2. Practical function of grease
The main reason for draining grease to the sliding surface is the increase in temperature of the grease around the NTN bearing. When the bearing starts to run normally, the grease will reach the sliding friction surface. Lubrication begins to work as the temperature increases.
Advantages of NTN imported bearings with grease lubrication:
    1) Individual bearing points must be refueled by hand. If the grease is used, it will save trouble and avoid accidents caused by lack of oil.
    2) The grease itself has a sealing effect, which allows the use of a mechanism with a low degree of sealing to achieve a simplified design.
    3) Experience has shown that lithium grease lubrication has a lower temperature rise and longer bearing life than a drop method in a certain speed range (n<20000r/min or dn<20000mm.r/min).
    2, NTN imported bearing lubrication theory basis: the lubrication mechanism of the bearing is the theory of elastic fluid dynamic pressure lubrication.
    3. NTN bearing failure type and lubrication relationship: Most of the failure causes are caused by faults in the assembly and poor sealing. A small number of failures are caused by wear, gluing, corrosion and overheating due to lack or excess of lubricant or quality failure.
    4. Basic characteristics of grease and general criteria for selecting grease:
    When selecting grease, it is necessary to select the grease that is compatible with the conditions of use (temperature, speed, load, environment, etc.), which are related to the basic characteristics of the grease, and the basic characteristics of the grease depend on the thickener and base oil. kind of.

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Reasons affecting the service life of INA bearings

There may be many factors that affect the service life of the bearing, which can be further clarified from the application factors and meanings.
If the first element is used, it means whether the device adjustment, application maintenance, maintenance and repair, etc. can meet the technical request. According to the technical requirements of INA bearing device, operation, maintenance and maintenance, the monitoring and inspection of the load, speed, working temperature, vibration, noise and lubrication accepted by the bearing in operation are suspended, and the abnormality is immediately found and the adjustment is suspended. Make it back to normal. The premise of the device is one of the primary factors in the application of the element. The bearing often causes the force condition between the parts of the whole bearing to change due to the unsuitable device. The bearing runs under abnormal conditions and the service life is early.
The first element of the connotation refers to the three sketches of the quality of the bearing, such as structural design, manufacturing process and data quality.
The metallurgical quality of imported bearing data was once the primary factor affecting the early failure of rolling bearings. With the improvement of metallurgical technology (such as vacuum degassing of bearing steel), the quality of the original data has been improved. The proportion of the original data quality factor in the bearing failure analysis has been significantly reduced, but it is still one of the primary factors affecting bearing failure. The suitability of the material selection is still an essential element for the analysis of bearing failure.
Rolling bearings exhibit late failure characteristics
Rolling bearings show late fault characteristics to serious faults (generally INA bearing damage such as axles, burns, sand cracks, raceways, bead wear, etc.) are not more than one week. The larger the equipment capacity, the faster the speed. The shorter the interval. Therefore, in the actual rolling bearing fault diagnosis, once the late fault characteristics are found, the bearing should be judged decisively and the maintenance should be arranged as soon as possible.
Rolling bearing vibration and noise begin to increase
After a period of motion, the vibration and noise are maintained at a certain level, and the spectrum is very single, only one or two times the frequency. There are very few spectrums above the power frequency, and the INA bearing state is very stable and enters a stable working period. After continuing to run, the vibration and noise of the rolling bearing begin to increase, sometimes abnormal sounds appear, but the change of vibration increases slowly. At this time, the kurtosis value of the imported bearing suddenly reaches a certain value. We believe that the rolling bearing is an initial failure at this time.
Bearing manufacturing is customary through multiple processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the bearing. Thermal processing and grinding processes that affect the quality of scrap bearings are often more directly related to bearing failure. In recent years, the research on the turbulent layer of the bearing working surface indicates that the grinding process is closely related to the bearing surface quality.
The primary obligation of INA bearing life analysis is to find out the primary factors that constitute bearing failure based on a large number of landscape data, profiling data and failure mode, so as to propose improvement measures in a targeted manner, delay bearing decommissioning period and avoid bearing An early failure of a sudden fire.

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Two precautions for oil mist lubrication of imported bearings

Another lubrication method for imported bearings - oil mist lubrication, which is a kind of micro-lubrication, simply means that a small amount of lubricating oil is used to meet the lubrication requirements of imported bearings. Oil mist lubrication is to turn the lubricating oil into an oil mist in the oil mist generator, and lubricate the bearing through the oil mist. Since the oil mist condenses into oil droplets on the working surface of the rolling bearing, the rolling bearing actually maintains a thin oil lubrication state. The following two points should be noted when using this lubrication method:

1. The viscosity of the oil should generally not be higher than 340mm / s (40 degrees) because too high viscosity will not achieve the atomization effect.

2. Lubricated oil mist may partially dissipate with the air and pollute the environment. If necessary, use an oil and gas separator to collect the oil mist, or use a ventilation device to remove the exhaust gas.

When the linear speed of the rolling element of the bearing is high, oil mist lubrication is often used to avoid other lubricating methods from increasing the internal friction of the oil and increasing the working temperature of the rolling bearing due to excessive oil supply. Typical oil mist pressures are about 0.05-0.1 mbar.

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Correct use of TIMKEN cylindrical roller bearing grease

Proper use of grease must be aware of the movement of grease in TIMKEN cylindrical roller bearings. Guarantee the stability of the grease. The movement of the grease filled in the rolling bearing can be roughly divided into two stages with the rotation of the TIMKEN cylindrical roller bearing.
    In general, the amount of grease in the TIMKEN cylindrical roller bearing always exceeds the actual amount of lubrication directly involved in the lubrication, on the frame and in the cavity of the bearing cover, and forms a contour on the periphery of the rolling element. . During this process, the bearing temperature rises rapidly due to the resistance of the excess grease. Although most of the excess grease is squeezed out at the beginning of the run, the grease that is squeezed into the raceway attachment may still be carried by the rolling element into the raceway. In the initial stage of bearing operation, most of the grease is squeezed out of the raceway very quickly (less than one minute), and the grease is accumulated in a small amount while being circulated with the TIMKEN cylindrical roller bearing rotating body. discharge. At this time, the bearing temperature will continue to rise until the excess grease is completely discharged, which can be called the grease's walking phase. According to the grease quality and filling amount in the bearing structure, this time may last for ten minutes. Even a few hours.
    After the remaining grease is completely discharged, the remaining small amount of grease forms a thin layer of grease film on the mutual contact surface of the rolling element, the raceway and the cage, thereby entering the normal operation stage of the bearing. . At this time, the temperature gradually drops and reaches equilibrium. In other words, long-term lubrication is mainly borne by this layer of grease film. In addition, during the long-term operation of the bearing, the contour of the rolling element and the raceway and the grease on the cage are shrunk to separate a part of the base oil, and after flowing into the raceway, the lubrication is also supplemented. .
    Different greases are different in the contours of TIMKEN cylindrical roller bearings. It is necessary to form a contour that is relatively straightforward. The running time is short. In the long-term operation, the bearing temperature is low and stable. This is a kind of It is an ideal grease, so it is especially important for the grease.
    Some so-called eddy-flow greases are not easy to form contours, and even if they are contoured, they are easy to collapse. At this time, the excess grease repeatedly returned to the raceway is in a state of being strongly stirred for a long time, and the torque of the TIMKEN cylindrical roller bearing is large. The temperature is high and unbalanced, and noise may also be generated, and the grease is also prone to deterioration and loss.

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Engine sliding SKF bearing damage features

Core Tip: As the world's top bearing SKF bearings, the application is very extensive. In every industry, the characteristics of its damage are also different. Today we look at the damage characteristics of the engine sliding bearing. (1
As the world's top bearing SKF bearings, the application is very extensive. In every industry, the characteristics of its damage are also different. Today we look at the damage characteristics of the engine sliding bearing.

(1) Mechanical damage

The mechanical damage of the sliding bearing means that the alloy surface of the bearing bush has different degrees of groove marks. In severe cases, metal peeling occurs on the contact surface and a large area of ​​random scratches occurs; in general, the contact surface damage and ablation phenomenon exist simultaneously. The main cause of mechanical damage to the bearing is that it is difficult to form an oil film on the bearing surface or the oil film is seriously damaged.

(2), bearing cave erosion

Under the repeated action of the sliding bearing in the cylinder pressure impact load, the surface layer is plastically deformed and hardened by hardening, and the local deformation loss ability is gradually formed, and the grain is gradually formed and expanded continuously. Then, as the wear debris falls off, a hole is formed in the loaded surface layer. . Generally, when cavitation occurs in the bearing bush, the pit first appears, and then the pit gradually expands and causes cracking at the interface of the alloy layer, and the crack spreads in the parallel direction of the interface until peeling off. The main reason for the cavitation of the sliding bearing is that the oil flow is strongly disturbed due to the sudden change of the cross section of the structural elements such as the oil groove and the oil hole, and bubbles are formed in the vacuum region where the oil flow is disordered, and then the bubble collapses due to the pressure rise. eclipse. Cavitation is generally found 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 refers to the overheating of the bearing and the excessive bearing clearance due to over-loading of the engine, resulting in fatigue damage, fatigue pitting or fatigue shedding in the middle of the bearing. Most of this damage is caused by overload, excessive bearing clearance, or unclean lubricating oil and foreign matter mixed in the interior. Therefore, when using, care should be taken to avoid overloading the bearing. Do not operate at too low or too high speed; adjust the engine to a steady state when idling; ensure normal bearing clearance and prevent engine speed from being too high or too low; check and adjust cooling The working condition of the system ensures that the working temperature of the engine is suitable.

(4), bearing alloy corrosion

The bearing alloy corrosion is generally the area where the lubricating oil is not pure. The chemical impurities (acid oxides, etc.) in the lubricating oil cause the bearing alloy to oxidize to form an acidic substance, causing the bearing alloy to partially fall off and form irregular micro holes or small concaves. pit. The main reason for the corrosion of the bearing alloy is improper selection of lubricating oil, poor corrosion resistance of the bearing material, or rough engine operation and high temperature.

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