Selection standard of fag imported machine tool spindle bearing
Selection standard of fag imported machine tool spindle bearing
2022-05-15
Selection and use of fag bearings
Selection and use of fag bearings
2022-05-16

Characteristics of engine sliding NSK bearing damage

Mechanical damage NSK bearing damage

  • 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.Characteristics of engine sliding NSK bearing damage
  • 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. Characteristics of engine sliding NSK bearing damage
  • 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.Characteristics of engine sliding NSK bearing damage
  • NSK bearing cavitation NSK bearing damage
  • 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. The crack extends along the parallel direction of the interface until it peels off. Characteristics of engine sliding NSK bearing damage
  • 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.Characteristics of engine sliding NSK bearing damage

 

fatigue pitting NSK bearing damage

  • 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. Characteristics of engine sliding NSK bearing damage
  • 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.Characteristics of engine sliding NSK bearing damage

NSK bearing alloy corrosion NSK bearing damage

  • 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.Characteristics of engine sliding NSK bearing damage
  •  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.Characteristics of engine sliding NSK bearing damage
  • 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.Characteristics of engine sliding NSK bearing damage
  • 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

Fixed load NSK bearing damage

  • 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:Characteristics of engine sliding NSK bearing damage
  • 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.Characteristics of engine sliding NSK bearing damage
  • Rotating load
  • 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.Characteristics of engine sliding NSK bearing damage
  • The characteristic of rotating load is that the synthetic radial load vector rotates relative to the ferrule. There are three rotating loads:Characteristics of engine sliding NSK bearing damage
  • The load direction is fixed and the ferrule rotates;
  • The load vector rotates and the ferrule is stationary;
  • The load vector and ferrule rotate at different speeds.Characteristics of engine sliding NSK bearing damage
  • Swing load and indefinite load
  • Sometimes the direction and size of the load cannot be determined accurately. For example, in high-speed rotating machinery, in addition to the load borne by the rotor weight which is fixed in the direction, there is also the rotating load caused by the unbalanced mass. If this rotating load is much larger than the fixed load, the combined load is still the rotating load; Characteristics of engine sliding NSK bearing damage
  • If the rotating load is much smaller than the fixed load, the composite load is the swing load. 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.Characteristics of engine sliding NSK bearing damage
  • 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.Characteristics of engine sliding NSK bearing damage
  • 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. Characteristics of engine sliding NSK bearing damage
  • 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.
  • 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.Characteristics of engine sliding NSK bearing damage
Characteristics of engine sliding NSK bearing damage
  • Rolling IKO bearing is a mass-produced mechanical part with strict requirements for manufacturing accuracy and high degree of technical specialization. Therefore, for the vast majority of easy to buy IKO bearing varieties, it should be more cost-effective to buy than repair. The repair of IKO bearing can only be considered under the following circumstances, namely:
  • The failure forms of a large number of IKO bearings of the same model used in large factories are mainly the wear, fatigue or fretting abrasion of the rolling surface. In particular, the damaged parts are mostly cages or rolling elements, and the rings or washers still have repair value;
  • Large and extra large IKO bearings are on the verge of failure or have failed without major damage to parts, or valuable IKO bearings must try to prolong their effective service life;
  • Some IKO bearing varieties that are really difficult to buy have to be repaired without spare parts after failure, especially imported IKO bearings;
  • IKO bearing has slight damage, such as slight water rust during storage and slight fretting abrasion during transportation. Such cases are easy to repair and regrettable to discard.
  • In addition to the economy, the repair of IKO bearing also has its technicality, which requires the repairer to fully understand the corresponding technical requirements of IKO bearing and the characteristics of IKO bearing and its parts in structure, technology and materials. Otherwise, it is difficult to ensure that IKO bearing repair has the required effect.

Economic benefits of IKO bearing repair

  • Generally speaking, IKO bearings have few varieties and large quantities. The price of a single IKO bearing is high, or the structure of IKO bearing is simple. If the size is large, the lower the repair cost is, the higher the economic benefit is.
  • In addition, monitoring the operation of IKO bearing and repairing it before IKO bearing failure in a planned way can get twice the result with half the effort. Following reasonable process, using efficient repair equipment and tools and obtaining the help of professional IKO bearing factory will help to improve economic benefits.
  • 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.

listen for:NSK bearing damage

  • 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.NSK bearing damage
  • 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.NSK bearing damage
  •  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.NSK bearing damage
  • 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.NSK bearing damage
  • 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.NSK bearing damage
  • The sliding bearing has low friction ratio and high transmission efficiency. Generally, the friction coefficient of sliding bearing is 0.08-0.12, while that of rolling Koyo bearing is only 0.001-0.005;
  • 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;
  • 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;
  • 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;
  • Some rolling bearings can bear radial load and axial load at the same time. Therefore, the structure of Koyo bearing support can be simplified;
  • 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;
  • Rolling bearing can be conveniently applied to any direction of space.
  • However, everything is divided into two, and the rolling Koyo bearing also has some disadvantages, mainly including:
  • 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);
  • 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
  • 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.
  • 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.
  • Select NTN bearing model with high load capacity
  • When selecting NTN bearings, the price of NTN bearings should be considered, or NTN bearings with higher load capacity but more expensive should be used, or ordinary NTN bearings should be used to prolong their service life. NTN bearings with high load capacity are adopted, such as cylindrical roller bearings with convexity, spherical roller bearings with symmetrical rollers, reinforced tapered roller bearings and ball bearings, ball bearings with corrected ball groove bus, or 70000cd series NTN bearings are used to replace deep groove (single row centripetal) ball NTN bearings. These NTN bearings with high load capacity or due to the improvement of stress distribution, Or it may have higher fatigue life due to the large number of rolling elements.
  • Select the appropriate NTN bearing size
  • In order to select the proper size of NTN bearing, the working load, speed and operating temperature of NTN bearing must be accurately calculated or verified. The load has a great impact on the service life of NTN bearing, so although it is difficult to measure the load, it should be measured as accurately as possible. When the load measurement is difficult, the actual power consumed by the motor can be measured, and the power loss along the way can be calculated according to the transmission route and deducted until the NTN bearing load is closer to the actual one. If the calculated or measured load is too large, the expected fatigue life of NTN bearing must be reduced by a greater margin, which must be remedied. If the installation position allows, NTN bearing with a larger size can be selected; If the radial dimension is limited, the wider NTN bearing should be selected when there is a wider NTN bearing; If wider NTN bearings cannot be used, NTN bearings with higher load carrying capacity can be used instead.
  • Select appropriate NTN bearing material
  • When selecting NTN bearing material, its price should also be taken into account, and when vacuum smelting or electroslag remelting steel has to be used, it should be noted that the lubrication conditions must be improved in order to double the expected fatigue life of NTN bearing. Of course, the cost of selecting NTN bearings made of this kind of high-quality steel is much more expensive than selecting NTN bearings with high load capacity. However, for NTN bearings that are difficult to access in machines and are extremely difficult to assemble and disassemble, or NTN bearings used in mining and tunnel operation machinery, they must be considered sometimes in situations where maintenance is extremely difficult.
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