How to reduce NTN bearing failure rate?
How to reduce NTN bearing failure rate?
2022年5月11日
Select NTN bearing model with high load capacity
Select NTN bearing model with high load capacity
2022年5月11日

How to inspect fag bearings

Mechanical damage fag bearings

  • The friction of Koyo bearing is mainly composed of rolling friction and sliding friction between rolling element and ring raceway; Sliding friction between cage and rolling element and ferrule surface (sliding friction between rolling elements without cage); The sliding friction between the end face of the roller and the retaining surface of the ferrule; Viscous resistance of lubricant; The sealing device is composed of sliding friction and other aspects, and its size depends on Koyo bearing type, size, load, speed, lubrication, sealing and other factors.
  • Deep groove ball bearings, cylindrical roller bearings and self-aligning ball bearings are usually used in instruments and machinery requiring low friction torque to bear radial load; Single row thrust ball bearing is selected to bear the radial load of Koyo bearing. If it bears combined load, angular contact ball bearing can be selected. When the load angle is basically the same as the contact angle, small friction torque can be obtained; If the gap between the two angles is too large, centripetal and thrust bearing assembly can be used to solve it.
  • When Koyo bearing with low friction torque is selected, contact sealing device shall be avoided in structural design. At the same time, for Koyo bearings with low friction torque, oil drop lubrication, oil mist lubrication and oil air lubrication should be adopted.
  • For novices who just use fag bearings, they often have no experience. Do not know how to check the purchased fag bearings. The following is a rough introduction to the method of checking fag bearings.
  • Observation method. Observe the rolling fag bearing with naked eyes. The inner and outer raceways shall be free of peeling marks and serious wear, and shall be in the shape of an arc groove; The surface of all rolling elements shall be free of spots, cracks and peeling; The cage shall not be loose, damaged or worn through, and the gap with the rolling element shall not be large.How to inspect fag bearings
  • Hand feeling method. The clearance between the inner and outer race of normal fag bearing and the rolling element is 0.005 ~ 0.010 mm. For the rolling fag bearing that has been used for one stage, there shall be no obvious vibration sound when holding the inner race with your fingers for axial shaking.How to inspect fag bearings
  • Rotation method. Hold the fag bearing inner race with one hand and rotate the outer race with the other hand. The fag bearing shall be able to rotate flexibly without radial shaking.How to inspect fag bearings
  • During inspection, the above three empirical methods shall be combined to make a correct judgment on the technical state of rolling fag bearing. For tapered roller fag bearings, also observe whether the rolling element is located in the middle of the outer race. If it moves forward, it shall not exceed 1.5mm.How to inspect fag bearings
  • As the world’s NSK bearing, it is widely used. Each industry has different characteristics of damage. Let’s take a look at the damage characteristics of engine sliding NSK bearing.How to inspect fag bearings
  • The mechanical damage of sliding NSK bearing refers to the groove marks in different degrees on the alloy surface of bearing bush. In serious cases, metal peeling and large-area random scratch occur on the contact surface; Generally, contact surface damage and ablation exist at the same time. The main reason for the mechanical damage of NSK bearing is that it is difficult to form oil film on the surface of NSK bearing or the oil film is seriously damaged.How to inspect fag bearings
  • Under the repeated action of cylinder pressure (impact load), the surface layer of sliding NSK bearing has plastic deformation and cold work hardening, locally loses its deformation ability, gradually forms wrinkles and expands continuously, and then forms cavities in the loaded surface layer with the falling off of wear debris. Generally, when the bearing bush is pitted, the pit first appears, and then the pit gradually expands and causes the cracking of the alloy layer interface.How to inspect fag bearings
  •  The crack extends along the parallel direction of the interface until it peels off. The main reason for cavitation of sliding NSK bearing is that the sudden change of the cross section of structural elements such as oil groove and oil hole causes strong disorder of oil flow, forming bubbles in the vacuum area with disordered oil flow, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of NSK bearing, such as the lower bearing bush of crankshaft main NSK bearing.How to inspect fag bearings
  • fatigue pitting
  • Fatigue pitting corrosion of NSK bearing refers to the fatigue damage, fatigue pitting corrosion or fatigue falling off in the middle of NSK bearing caused by overheating of NSK bearing and excessive clearance of NSK bearing due to overload operation of engine. This damage is mostly caused by overload, too large NSK bearing clearance, or unclean lubricating oil and foreign matters mixed in it.How to inspect fag bearings
  •  Therefore, attention should be paid to avoid overload operation of NSK bearing during use, and do not operate at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure the normal NSK bearing clearance and prevent the 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.How to inspect fag bearings
  • NSK bearing alloy corrosion
  • NSK bearing alloy corrosion is generally caused by impure lubricating oil. The chemical impurities (acid oxides, etc.) in the lubricating oil oxidize the NSK bearing alloy to form acidic substances, causing part of the NSK bearing alloy to fall off and form irregular small cracks or pits. The main causes of NSK bearing alloy corrosion are improper selection of lubricating oil, poor corrosion resistance of NSK bearing materials, or rough engine operation and high temperature.How to inspect fag bearings
  • NSK bearing melting
  • There is a small convex metal surface between the journal and the NSK bearing friction pair, which forms a local high temperature. Under the condition of insufficient lubrication and poor cooling, the NSK bearing alloy blackens or burns locally. This fault is often caused by too tight fit between journal and NSK bearing; Insufficient lubricating oil pressure is also easy to burn NSK Bearings.How to inspect fag bearings
  • NSK bearing outer circle
  • The outer circle of NSK bearing means that NSK bearing has relative rotation in the seat hole. After the NSK bearing goes through the outer circle, it will not only affect the heat dissipation of the NSK bearing, which is easy to ablate the alloy on the inner surface of the NSK bearing, but also damage the back of the NSK bearing and burn the NSK bearing in serious cases. The main reason is that NSK bearing is too short, tenon damage, processing or installation does not meet the specifications, etc.How to inspect fag bearings
How to inspect fag bearings

How to inspect fag bearings cavitation

  • When selecting the fit, the type of load borne by the ferrule should be considered first. Generally, there are three types of load borne by the ferrule:How to inspect fag bearings
  • Fixed load
  • The synthetic radial load acting on the ferrule is borne by the local area of the ferrule raceway and transmitted to the relative area of the shaft or SKF bearing seat. This load is called fixed load. The characteristic of fixed load is that the synthetic radial load vector is relatively static with the ferrule. Both the ferrule and the synthetic radial load do not rotate or rotate at the same speed, which are fixed loads. Loose fitting can be selected for ferrule bearing fixed load.How to inspect fag bearings

Rotating load fag bearings

  • The synthetic radial load acting on the ferrule rotates along the circumferential direction of the raceway and is successively borne by each part. This load is called rotational load.How to inspect fag bearings
  • The characteristic of rotating load is that the synthetic radial load vector rotates relative to the ferrule. There are three cases of rotating load:How to inspect fag bearings
  • The load direction is fixed and the ferrule rotates;How to inspect fag bearings
  • The load vector rotates and the ferrule is stationary;How to inspect fag bearings
  • The load vector and ferrule rotate at different speeds.How to inspect fag bearings
  • Swing load and indefinite load
  • In addition to the fixed load caused by the rotation direction of the rotor, sometimes the load caused by the rotation direction is still much larger than the exact load caused by the rotation direction of the rotor, for example; If the rotating load is much smaller than the fixed load, the composite load is the swing load.How to inspect fag bearings
  •  No matter rotating load or swinging load, its size and direction are constantly changing. In the variable working state, the load on some ferrules may be rotating load, fixed load or swinging load. This kind of load is called indeterminate load.How to inspect fag bearings
  • Swing load and indefinite load should be treated equally with rotating load in terms of fit. Too loose fit will cause damage to the mating surface.How to inspect fag bearings
  • Transition fit or interference fit shall be selected for the ferrule rotating relative to the load direction and the shaft or seat hole. The interference size is based on the principle that when the SKF Bearing works under load, the SKF Bearing ring will not produce “creep” on the shaft or the mating surface in the seat hole. When the load is very light or the ferrule rotates occasionally at low speed under the action of heavy load, the transition fit can be selected. At this time, the shaft surface should have high hardness and small surface roughness.fag bearings
  • For heavy load occasions, it is usually tighter than that in light load and normal load occasions. The heavier the load, the greater the fit interference.fag bearings

listen for:How to inspect fag bearings

  • It is more and more important to check the condition of the running machine and prepare a thorough inspection plan, in which the Koyo bearing is the focus of attention, because it is an important rotating part of all machines. Condition monitoring is an important part of preventive maintenance. Early detection of Koyo bearing damage can avoid equipment shutdown during unplanned maintenance caused by Koyo bearing damage. Let me introduce this method of listening to you.How to inspect fag bearings
  • Using hearing to identify irregular operation is a very common method. For example, it is used by experienced operators to detect the abnormal noise of a part with the help of electronic stethoscope. If the Koyo bearing is in good operation condition, it will make low whine sound. If it makes sharp hiss, squeak and other irregular sounds, it usually indicates that the imported Koyo bearing is in bad operation condition.
  • Sharp squeaking noises may be caused by improper lubrication. Improper Koyo bearing clearance can also cause metal sound. The dents on the track of the outer ring of the Koyo bearing will cause vibration and make a smooth and crisp sound. If it is due to the knocking scars caused during installation, it will also produce noise, which will vary with the speed of the Koyo bearing. 
  • If there is intermittent noise, it means that the rolling parts may be damaged. This sound occurs when the damaged surface is rolled out. If there are pollutants in the Koyo bearing, it will often cause hissing sound. Serious damage to the Koyo bearing will produce irregular and huge noise.How to inspect fag bearings
  • The damage of Koyo bearing can be detected by hearing, but usually it has arrived at this time, and the Koyo bearing must be replaced immediately. Therefore, a better method is to use, for example, electronic condition monitoring instrument to check the operation of Koyo bearing in advance.How to inspect fag bearings
  • Compared with the old method (using a wooden stick or screwdriver against the Koyo bearing housing and the other end against the ear), using advanced instruments can more accurately predict the condition of Koyo bearings.How to inspect fag bearings
  • The friction coefficient of rolling bearing is smaller than that of sliding bearing and the transmission efficiency is high. Generally, the friction coefficient of sliding bearing is 0.08-0.12, while that of rolling Koyo bearing is only 0.001-0.005;How to inspect fag bearings
  • The rolling bearing has realized standardization, serialization and generalization, which is suitable for mass production and supply, and the use and maintenance are very convenient;How to inspect fag bearings
  • The rolling bearing is made of Koyo bearing steel and subjected to heat treatment. Therefore, the rolling Koyo bearing not only has high mechanical properties and long service life, but also can save the expensive non-ferrous metals used in the manufacture of sliding Koyo bearing;How to inspect fag bearings
  • The internal clearance of rolling bearing is very small, and the machining accuracy of each part is high. Therefore, the operation accuracy is high. At the same time, the rigidity of Koyo bearing can be increased by preloading. This is very important for precision machinery;How to inspect fag bearings
  • Some rolling bearings can bear radial load and axial load at the same time. Therefore, the structure of Koyo bearing support can be simplified;How to inspect fag bearings
  • Because the rolling bearing has high transmission efficiency and low heating capacity, it can reduce the consumption of lubricating oil and save trouble in lubrication maintenance;How to inspect fag bearings

Rolling bearing can be conveniently applied to any direction of space.How to inspect fag bearings

  • However, everything is divided into two, and the rolling Koyo bearing also has some disadvantages, mainly including:How to inspect fag bearings
  • The load bearing capacity of rolling bearing is much smaller than that of sliding Koyo bearing with the same volume. Therefore, the radial size of rolling Koyo bearing is large. Therefore, sliding Koyo bearings are often used in occasions with large load and occasions requiring small radial size and compact structure (such as Koyo bearings of internal combustion engine crankshaft);How to inspect fag bearings
  • The vibration and noise of rolling bearing are large, especially in the later stage of use. Therefore, it is difficult for rolling bearing to be competent in the occasions with high precision and no vibration. Generally, the effect of selecting sliding Koyo bearing is better.How to inspect fag bearings
  • Rolling bearings are particularly sensitive to foreign matters such as metal chips. Once foreign matters enter into Koyo bearings, intermittent large vibration and noise will be generated, which will also cause early damage. In addition, rolling bearings are also prone to early damage due to metal clip impurities. Even if there is no early damage, the service life of rolling bearings has a certain limit. In short, the service life of rolling Koyo bearing is shorter than that of sliding Koyo bearing.How to inspect fag bearings
  • However, compared with sliding Koyo bearings, rolling Koyo bearings have their own advantages and disadvantages and occupy certain application occasions. Therefore, they can not completely replace each other. However, due to the outstanding advantages of rolling Koyo bearings, at present, rolling Koyo bearings have developed into the main support type of machinery and are more and more widely used.How to inspect fag bearings