Precautions for appearance inspection of Timken bearing
Precautions for appearance inspection of Timken bearing
2022年5月11日
How to inspect fag bearings
How to inspect fag bearings
2022年5月11日

How to reduce NTN bearing failure rate?

Knowledge of NTN bearing accessories

 

  • Inclined retaining ring (separable): a separable ring with “L” shaped section, and its outer part is used as a retaining edge of the inner ring of centripetal cylindrical roller SKF Bearing.How to reduce NTN bearing failure rate?
  • Flat retaining ring: a separable basically flat washer with its inner or outer part as a retaining edge of the outer ring or inner ring of centripetal cylindrical roller SKF Bearing.How to reduce NTN bearing failure rate?
  • Stop ring: a single ring with constant cross-section, installed in an annular groove, to axially position the rolling SKF Bearing in the housing or on the shaft.How to reduce NTN bearing failure rate?
  • Middle retaining ring: a separable ring in a roller SKF Bearing with two or more rows of rollers, which is used to isolate the two rows of rollers and merge the rollers.How to reduce NTN bearing failure rate?
  • Spacer: it is an annular part used between two SKF Bearing Rings or SKF Bearing washers, or between two half SKF Bearing Rings or between two half SKF Bearing washers, so as to maintain the specified axial distance between them. NTN bearing
  • Seal ring: an annular cover composed of one or several parts, which is fixed on one ring or washer of SKF Bearing and contacts with another ring or washer or forms a narrow labyrinth gap to prevent leakage of lubricating oil and invasion of foreign objects.
  • Dust cover: it is an annular cover, usually stamped from thin metal plate, fixed on one ring or washer of SKF Bearing and extending towards another ring or washer to cover the internal space of SKF Bearing, but not in contact with another ring or washer.
  • Lock ring: a single ring with constant section, which is installed in the annular groove as a retaining ring to keep the roller or cage in the SKF Bearing.How to reduce NTN bearing failure rate?
  • Rolling element: a ball or roller that rolls between raceways.How to reduce NTN bearing failure rate?
  • Cage: SKF Bearing parts that partially wrap all or some rolling elements and move with them to isolate the rolling elements, and usually return the rolling elements and keep them in the SKF Bearing.How to reduce NTN bearing failure rate?
  • Retainer: a part attached to the inner ring or shaft ring. It uses centrifugal force to enhance the ability of rolling SKF Bearing to prevent foreign objects from invading.How to reduce NTN bearing failure rate?
  • During the disassembly of the coupling, the difficult work is to remove the hub from the shaft. For the hub connected by key, it is generally disassembled with three foot puller or four foot puller. The selected puller should match the overall dimension of the wheel hub, and the right angle hook of each foot of the puller should be properly combined with the rear side of the wheel hub, so as not to slip when applying force. 
  • This method is only used for the disassembly of the wheel hub with small interference ratio. For the wheel hub with large interference ratio, the heating method is often used or combined with the hydraulic jack
  • Cleaning, cleaning and quality evaluation of all parts of the coupling is a very important work after the disassembly of the coupling. The evaluation of parts and components refers to the comparison between the existing conditions of the size, shape and material properties of each part and the quality standards determined by the design of parts and components after operation, so as to determine which parts and components can continue to be used, which parts and components should be repaired and used, and which parts and components should be scrapped and updated.
  • Generally, the coupling bolts shall be removed first. As a layer of oil dirt, corrosion products and other deposits are deposited on the thread surface, it is difficult to disassemble the bolts, especially for the bolts with serious corrosion. Proper tools must be selected for the disassembly of the connecting bolt, because the bearing surface of the outer hexagon or inner hexagon of the bolt has been skidded and damaged, and the disassembly will be more difficult. It is easy for the solvent to penetrate into the loose part of the bolt (such as the loose part of the bolt) so that the rust can be removed easily

Assembly of coupling NTN bearing

  • Generally speaking, the world’s imported bearings such as imported bearings will not be excited. Once that happens. Then we should check it carefully.
  • Excitation caused by the change of the number of loaded rolling elements
  • When a radial load is loaded on an inlet bearing, the number of rolling elements bearing the load will change slightly during operation, that is, this causes the deviation of the load direction. The resulting vibration is inevitable, but can be reduced by axial preloading, which is applied to all rolling elements (not applicable to cylindrical roller bearings).
  • Waviness of components
  • When the imported bearing ring is closely matched with the imported bearing seat or transmission shaft, the imported bearing ring may be deformed by matching with the shape of adjacent components. If deformation occurs, vibration may occur during operation. Therefore, it is important to machine the imported bearing pedestal and transmission shaft to the required tolerance.
  • Local damage
  • Due to incorrect operation or installation, a small number of inlet bearing raceways and rolling elements may be damaged. During operation, rolling over the damaged inlet bearing components will produce a specific vibration frequency. Vibration frequency analysis can identify damaged imported bearing components.
  • Vibration behavior in applications
  • In many applications, the stiffness of imported bearings is the same as that of surrounding structures. Due to this feature, as long as the imported bearing (including preload and clearance) and its configuration in application are correctly selected, it is possible to reduce the vibration in application.
  • There are three ways to reduce the vibration of imported bearings
  • Remove critical excitation vibration from application; Restraining the critical excitation vibration between the excitation part and the resonance part; Change the stiffness of the structure, so as to change the critical frequency.
How to reduce NTN bearing failure rate?

Vibration behavior NTN bearing failure rate

  • The configuration of NSK bearing also has a great impact on the bearing rigidity. Generally speaking, for centripetal thrust ball NSK bearing and roller bearing, when used in pairs, it is appropriate to adopt the configuration with the large end face of the outer ring opposite (i.e. the pressure cone formed by its pressure line is outward). In this way, the ability of anti overturning torque of the bearing is large, and the adjusted preload changes less when the temperature changes.
  • For needle roller NSK Bearings with only stamped outer rings, because the outer ring wall is very thin, it is not necessary to knock and install with a hammer, and it should be pressed in with a press. Because the pressure is uneven when the hammer is knocked, it is easy to cause local deformation of the outer ring of the needle roller bearing.
  • “Cross fixing” refers to an NSK bearing configuration in which each NSK bearing positions the shaft in one direction and in the opposite direction. This combination is mainly used for short shafts. All radial NSK Bearings that can bear axial load in at least one direction are applicable, including deep groove and angular contact ball bearings, tapered roller bearings and NJ cylindrical roller bearings. When using angular contact ball bearings or tapered roller bearings, preload must be applied on some occasions.
  • The shaft is supported radially and axially by two NSK Bearings. The NSK bearing on one side is called the fixed end NSK bearing. It bears both radial and axial loads and plays the role of relative axial displacement between the fixed shaft and the NSK bearing housing. The other side is called the free end, which only bears the radial load and can move relatively in the axial direction.
  • NSK Bearings at the fixed end must be fixed with the shaft and NSK bearing housing at the same time. The more suitable NSK Bearings are radial NSK Bearings that can bear composite loads, such as deep groove ball bearings, self-aligning roller bearings, double row or paired angular contact ball bearings or tapered roller bearings. 
  • Radial NSK bearing combinations bearing simple radial load, such as cylindrical roller bearings with inner and outer rings without retaining edges, can also be used as fixed end NSK Bearings through combination with deep groove ball bearings, four point contact ball bearings or two-way thrust bearings. 
  • At this time, the second NSK bearing provides two-way axial positioning, but it must be installed with a certain radial spacing from the NSK bearing housing. When the length of NSK bearing at the free end changes due to thermal expansion, there will be no extrusion in NSK bearing. Axial displacement can occur inside NSK bearing, NSK bearing ring and NSK bearing seat.

How to reduce NTN bearing failure rate?

  • There are four main methods for injecting lubricating grease into Koyo bearings, which are grease cup method, coating method, grease gun method and centralized grease feeding method.How to reduce NTN bearing failure rate?
  • Open a small hole next to the Koyo bearing to the grease cup, and the grease in the cup will continuously supplement the bearing. The grease overflow valve shall be set for the high-speed bearing to throw out the excessive grease in the bearing through the centrifugal force during bearing rotation, so as to reduce the friction of the bearing and the temperature rise caused by high-speed rotation.How to reduce NTN bearing failure rate?
  • Second: smear method
  • Special tools shall be used when applying, and bare hands are not allowed. The grease amount shall meet the above requirements, and the lubricating grease shall cover all bearing surfaces that need to be lubricated. After the grease has been used for a certain period of time, it needs to be changed or supplemented.How to reduce NTN bearing failure rate?
  • Third: grease gun method
  • The grease gun is used to drive the grease into the bearing through the greasing hole through pressure. This method is mostly used to supplement the grease.How to reduce NTN bearing failure rate?
  • Fourth: concentrated fat feeding method
  • The grease is uniformly transported to the parts of each Koyo bearing by the pump through the pipeline. The flow route of the newly added grease shall be able to squeeze out the old grease, so as to supplement the new grease into each lubrication point. The quality of heat treatment and quenching of IKO bearing parts mainly depends on the quenching heating conditions and cooling conditions, and the cooling conditions mainly depend on the selection of corresponding quenching oil and cooling technology.How to reduce NTN bearing failure rate?
  • IKO bearing parts are mainly quenched and cooled with mineral oil. Mineral oil is composed of paraffin, bad alkane, aromatic hydrocarbon, paraffin aromatic series hydrogen talking compounds and their derivatives. Due to different composition and refining methods, special quenching oils with different characteristics and different uses are formed. How to reduce NTN bearing failure rate?
  • According to the use requirements (including cooling speed, service temperature, brightness, etc.), it can be divided into ordinary quenching oil, fast quenching oil, overspeed quenching oil, graded quenching oil, vacuum quenching oil, fast bright quenching oil and mechanical oil.How to reduce NTN bearing failure rate?
  • When selecting quenching oil, factors such as material, shape, size, deformation, hardening layer depth, process, brightness and heat treatment equipment of parts to be treated must be fully considered. Excellent quenching oil is made of refined base oil with high thermal stability (generally paraffin base) and various additives that can improve service performance and service life. How to reduce NTN bearing failure rate?
  • For rolling IKO bearing parts, during quenching and cooling, the transformation of pearlite type shall be prevented to avoid opaque quenching or local defects such as troostite and soft spots. Therefore, the cooling rate of quenching oil should be greater than the critical cooling rate of IKO bearing steel. How to reduce NTN bearing failure rate?
  • However, the cooling speed should not be too large, so as not to cause large internal stress, resulting in cracking and excessive quenching deformation. According to the C curve, the austenite transformation temperature of gcr15iko bearing steel is about 650 ℃ and 450 ℃. How to reduce NTN bearing failure rate?How to reduce NTN bearing failure rate?
  • Before this temperature, it must be cooled quickly, but at the later temperature, it can be cooled slowly, especially between the starting point of martensite transformation MS and MF. Slow cooling can reduce deformation and cracks, but it can not be too slow. Otherwise, the stable aging of austenite is easy to cause the increase of residual austenite. How to reduce NTN bearing failure rate?
  • Therefore, the cooling rate can be higher than the critical cooling rate at 650 ℃ and 450 ℃, and the oil with slow cooling rate after this temperature is quenching oil Under normal conditions, it is difficult to determine the critical cooling rate of steel under various conditions due to different field conditions However, in the field, the change trend of critical cooling rate can be judged according to the factors affecting the critical cooling rate, and the quenching oil can be selected accordingly If the quenching temperature is high, the holding time is long, and the original structure is fine, the critical cooling speed will be smaller, which is the quenching oil with small cooling capacity.How to reduce NTN bearing failure rate?
  • For IKO bearing rings with large wall thickness, if sufficient hardening layer is obtained, the quenching oil should have a faster cooling rate. For thin-walled IKO bearing rings, the quenching oil should have a slower cooling rate. For parts with complex shapes, quenching oil with short steam film stage and fast cooling speed should be selected.How to reduce NTN bearing failure rate?
  • For IKO bearing rings requiring small deformation, graded quenching oil shall be selected. If the grading temperature of IKO bearing steel ring is above MS point, the cooling speed reaches the critical cooling speed. Generally speaking, the world’s imported bearings such as imported bearings will not be excited. Once that happens. Then we should check it carefully.How to reduce NTN bearing failure rate?
  • Excitation caused by the change of the number of loaded rolling elements
  • When a radial load is loaded on an inlet bearing, the number of rolling elements bearing the load will change slightly during operation, that is, this causes the deviation of the load direction. The resulting vibration is inevitable, but can be reduced by axial preloading, which is applied to all rolling elements (not applicable to cylindrical roller bearings).How to reduce NTN bearing failure rate?
  • Waviness of components
  • When the imported bearing ring is closely matched with the imported bearing seat or transmission shaft, the imported bearing ring may be deformed by matching with the shape of adjacent components. If deformation occurs, vibration may occur during operation. Therefore, it is important to machine the imported bearing pedestal and transmission shaft to the required tolerance.How to reduce NTN bearing failure rate?
  • Local damage
  • Due to incorrect operation or installation, a small number of inlet bearing raceways and rolling elements may be damaged. During operation, rolling over the damaged inlet bearing components will produce a specific vibration frequency. Vibration frequency analysis can identify damaged imported bearing components.How to reduce NTN bearing failure rate?
  • In many applications, the stiffness of imported bearings is the same as that of surrounding structures. Due to this feature, as long as the imported bearing (including preload and clearance) and its configuration in application are correctly selected, it is possible to reduce the vibration in application.How to reduce NTN bearing failure rate?
  • There are three ways to reduce the vibration of imported bearings
  • Remove critical excitation vibration from application; Restraining the critical excitation vibration between the excitation part and the resonance part; Change the stiffness of the structure, so as to change the critical frequency.How to reduce NTN bearing failure rate?