Specified conditions for regular inspection of SKF imported bearings
Regular maintenance of mechanical equipment is very important for production. As a precision accessory of mechanical equipment, the regular inspection of SKF imported bearings is particularly critical. Here is the necessity and key steps of bearing regular inspection.Specified conditions for regular inspection of SKF imported bearings
Specified conditions for regular inspection of SKF imported bearings
It is important to keep the bearings and lubrication clean
Before inspection, clean the surface of the machine, and then remove the parts around the SKF inlet bearing. The oil seal is a very fragile part, so it needs to be disassembled carefully. Do not apply excessive force, and then carefully check the oil seal and its surrounding parts. If there are bad symptoms, be sure to replace it. The bad oil seal will lead to bearing damage and strict equipment shutdown.Specified conditions for regular inspection of SKF imported bearings
Check the lubricant of the bearing
Rub a little lubricant between your fingers. If there are pollutants, you can feel it, or apply a layer of lubricant on the back of your hand, and then seal it for light inspection.Specified conditions for regular inspection of SKF imported bearings
Replace the lubricant of the bearing
After draining out the old oil, if possible, refill fresh oil into the oil lubricated bearing and let the machine rotate at low speed for a few minutes. Make the engine oil collect residual pollutants as much as possible, and then drain the engine oil. The engine oil is filtered before use.Specified conditions for regular inspection of SKF imported bearings
For grease lubricated bearings, the arbor used when replacing grease should avoid connecting the angle of cotton to any part of the bearing, because these residual fibers may wedge between the rolling parts and cause damage, especially for the application of small bearings.Specified conditions for regular inspection of SKF imported bearings
Cover exposed bearings
When inspecting bearings, never expose SKF imported bearings to pollutants or moisture. If the work is interrupted, the machine shall be covered with oil paper, plastic sheet or similar materials.Specified conditions for regular inspection of SKF imported bearings
If it is possible to clean the naked bearing without disassembly, clean it with a brush coated with white spirit, and then dry it with a piece of lint free cloth or blow dry with compressed air (be careful not to start the rotation of the bearing assembly).
Raceway sound of imported bearings and its control method raceway sound is a smooth and continuous sound made by the rolling body rolling on the raceway surface when the shaft is running. It is a unique basic sound that will occur in all rolling bearings. The general bearing sound is the sound of raceway plus other sounds. The raceway sound of ball bearing is irregular, and its frequency is above 1000Hz. Its main frequency does not change with the speed, but its total sound pressure level increases with the speed. Specified conditions for regular inspection of SKF imported bearings
For the bearing with loud raceway sound, the sound pressure level of raceway sound decreases with the increase of viscosity; The sound pressure level of SKF Bearing with low raceway noise changes from decrease to increase when the viscosity increases to more than 20mm2 / s. The greater the rigidity of the bearing pedestal, the lower the total sound pressure level of the raceway sound. If the radial clearance is too small, the total sound pressure level and dominant frequency of raceway sound will increase sharply with the decrease of radial clearance. Specified conditions for regular inspection of SKF imported bearings
The methods to control the sound of raceway are: select low-noise bearings, that is, bearings with small waviness, and carefully select the service conditions. Raceway noise often affects the noise of the whole machinery. Reducing raceway noise can reduce the noise of the whole machinery.Specified conditions for regular inspection of SKF imported bearings
Impact sound of rolling element and its control method when the ball bearing or cylindrical roller bearing of larger model runs at low speed under pure radial load, due to the small centrifugal force of the rolling element, the rolling element in the non load area will impact the cage or raceway and make noise. But as the speed increases, the sound will disappear. The control methods of impact sound of rolling elements are: appropriately reduce the radial clearance, and use the bearing of cage with reasonable structure and flexible material.Specified conditions for regular inspection of SKF imported bearings
Rolling sound of bearing and its control method rolling sound is the harsh metal friction sound that can occur in cylindrical roller bearings on all occasions. It mostly occurs in grease lubricated larger SKF bearings, but it is more likely to occur in greases with degraded base oil performance, which hardly occurs in oil lubrication. In addition, it is easy to occur in winter.Specified conditions for regular inspection of SKF imported bearings
When bearing pure radial load, it is easy to occur in the case of large radial clearance, and it is easy to occur in a specific speed range with different models and sizes, both continuously and intermittently. Special processing methods for the outer ring raceway can prevent the occurrence of rolling sound. If necessary, this kind of bearing can be selected, or the radial clearance of the bearing can be appropriately reduced, the lubricating grease with excellent performance can be used and the rigidity of the parts matched with the bearing can be improved.Specified conditions for regular inspection of SKF imported bearings
Bearing lubrication methods can be roughly divided into grease lubrication and oil lubrication. To give full play to the function of bearing, it is important to use reduction and use purpose, and adopt lubrication method. Table 4-2 shows the advantages and disadvantages of grease lubrication and oil lubrication.
Grease is a lubricant composed of base oil, thickener and additives. When selecting, the lubricating oil that is very suitable for the service conditions of the bearing should be selected. Different trademarks will have great differences in performance. When selecting, attention must be paid to.Specified conditions for regular inspection of SKF imported bearings
Common lubricating greases for bearings include calcium base grease, sodium base grease, calcium sodium base grease, lithium base grease, aluminum base grease and molybdenum disulfide grease.Specified conditions for regular inspection of SKF imported bearings
The amount of grease filled in SKF Bearing is suitable to fill 1 / 2-1 / 3 of the internal space of the bearing. It should be reduced to 1 / 3 at high speed. Too much grease will increase the temperature rise.Specified conditions for regular inspection of SKF imported bearings
When selecting the working temperature of the lubricating grease, the main indicators should be the drop point, oxidation stability and low-temperature performance. The drop point can generally be used to evaluate the high-temperature performance, and the actual working temperature of the bearing should be 10-20 ℃ lower than the drop point. The service temperature of synthetic grease shall be 20-30 ℃ lower than the dropping point.Specified conditions for regular inspection of SKF imported bearings
When selecting grease for bearing load, select grease with small penetration for heavy load. When working under high pressure, in addition to small penetration, it also has high oil film strength and extreme pressure performance.Specified conditions for regular inspection of SKF imported bearings
When choosing grease for environmental conditions, calcium based grease is not easy to dissolve in water and is suitable for dry and less moisture environment. Oil lubrication
Under high-speed and high-temperature conditions, oil lubrication can be used when grease lubrication is no longer suitable. Lubricating oil circulation can take away a lot of heat. The viscosity of lubricating oil between cst-12 and cst-12 directly affects the viscosity of lubricating oil under normal working conditions. The higher the rotating speed, the lower the viscosity should be selected, and the heavier the load, the higher the viscosity should be selected. Specified conditions for regular inspection of SKF imported bearings
Common lubricating oils include machine oil, high-speed machine oil, turbine oil, compressor oil, transformer oil, cylinder oil, etc. In general, Koyo bearing, as a world bearing, will not be excited, but if it is excited, you must check the situation well. Let’s explain the truth of the excitation. Vibration excitation may occur when the bearing is partially damaged. Specified conditions for regular inspection of SKF imported bearings
A small number of bearing raceways and rolling elements may be damaged due to incorrect operation or installation. During operation, rolling over damaged bearing parts will produce specific vibration frequency. Vibration frequency analysis can identify damaged bearing components.
Vibration excitation may occur when the waviness of Koyo bearing is not necessarily deformed. In the case of close fit between the bearing ring and the bearing seat or transmission shaft, the 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 bearing pedestal and drive shaft to the required tolerances.Specified conditions for regular inspection of SKF imported bearings
In addition, the excitation behavior will also occur in applications. In many applications, the stiffness of the bearing is the same as that of the surrounding structure. Because of this feature, as long as the bearing (including preload and clearance) and its configuration in the application are correctly selected, it is possible to reduce the vibration in the application.Specified conditions for regular inspection of SKF imported bearings
There is also the excitation generated when the number of loaded rolls changes. When a radial load is loaded on a 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). Let’s introduce three small methods that can reduce the vibration of Koyo bearing. Change the stiffness of the structure, so as to change the critical frequency. Critical excitation vibration is removed from the application. Suppress the critical excitation vibration between the excitation part and the resonance part.Specified conditions for regular inspection of SKF imported bearings
The selection of specifications, dimensions and accuracy according to the service parts, service conditions and environmental conditions, and matching with appropriate Koyo bearings are the premise to ensure the service life and feasibility of bearings.Specified conditions for regular inspection of SKF imported bearings
Application position: tapered roller bearing is suitable for bearing the combined radial and axial load dominated by radial load. It is usually used in pairs with two sets of bearings. It is mainly used in the transmission parts of automobile, such as front and rear hubs, driving bevel gears, differential, reducer and so on.Specified conditions for regular inspection of SKF imported bearings
Allowable speed: under the condition of correct installation and good lubrication, the allowable speed is 0.3-0.5 times of the limit speed of Koyo bearing. Under normal conditions, it is appropriate to use 0.2 times of the limit speed.Specified conditions for regular inspection of SKF imported bearings
Allowable inclination angle: tapered roller bearings generally do not allow the shaft to be inclined relative to the shell hole. If there is an inclination, the inclination shall not exceed 2 ‘.Specified conditions for regular inspection of SKF imported bearings
Allowable temperature: under the condition of bearing normal load, high temperature resistance of lubricant and sufficient lubrication, general Koyo bearing is allowed to work at the ambient temperature of – 30 ℃ – 150 ℃.
The running state of the machine that needs to be checked is the focus of attention in the bearing, and it is becoming more and more important to prepare a thorough inspection scheme. Because it is an important condition monitoring of all rotating machinery components to prevent Koyo bearing damage and to prevent early detection of bearing damage during unplanned maintenance equipment shutdown, it is an important part at home.Specified conditions for regular inspection of SKF imported bearings
But not all machines are equipped with this advanced equipment. In this case, the machine operator or maintenance engineer must adhere to the Koyo bearing fault signal alarm.
The sharp squeaking noise may be caused by the improper clearance of Koyo bearing. Insufficient lubrication can also cause metal sound. Dents in the bearing cup track can cause vibration. As for the noise generated by the equipment caused by knocking scars, this noise has different speed levels of Koyo bearings. Specified conditions for regular inspection of SKF imported bearings
If there is intermittent noise, then the rolling part may be damaged. This sound appears. When the surface is damaged, if the bearing hiss “sound pollution often causes serious damage to the bearing and causes irregular and huge noise.Specified conditions for regular inspection of SKF imported bearings
However, it is usually unnecessary to replace the Koyo bearing at this time. Therefore, bearing damage, of course, can also be perceived by listening. If better methods are used, such as electronic health monitoring equipment, the operation of bearings before eruption.Specified conditions for regular inspection of SKF imported bearings
In practice, attention should be paid to the selection of the location of measuring points and acquisition methods. To truly and accurately reflect the bearing vibration state. Therefore, it is necessary to arrange measuring points near the bearing. The free end of the motor is generally provided with a rear fan cover, and the measuring points are selected in the fixing screws of the fan cover, which has a good monitoring effect. In addition, it is necessary to collect and analyze the vibration signals for many times and compare them comprehensively. Ability to draw accurate conclusions.Specified conditions for regular inspection of SKF imported bearings
Ina imported bearing shows a strong regularity in its use, which is found in the temporary production condition monitoring. And the repeatability is very good. When the normal high-quality bearing is put into use, the vibration and noise are relatively small, but the spectrum is somewhat scattered and the amplitude is small, which may be caused by some defects in the manufacturing process, such as surface burrs.Specified conditions for regular inspection of SKF imported bearings
The vibration and noise shall be maintained at a certain level after a period of exercise. The spectrum is very single, with only one or two frequency doubling. The frequency spectrum above three times of power frequency rarely appears, and the bearing state is very stable and enters the stable working period.Specified conditions for regular inspection of SKF imported bearings
The vibration and noise of the bearing began to increase and entered the later stage of use after continued operation. Sometimes there is abnormal sound, but the vibration increases slowly. At this time, the kurtosis value of the bearing suddenly reaches a certain value. It is considered that the bearing at this time is an initial fault.Specified conditions for regular inspection of SKF imported bearings
It is required to closely monitor the bearing. Pay close attention to its changes. Then, the bearing kurtosis value began to decline rapidly and close to the normal value, while the vibration and noise began to increase significantly, and the increase amplitude began to accelerate.Specified conditions for regular inspection of SKF imported bearings
When the vibration exceeded the vibration specification (such as ISO2372 specification), the bearing kurtosis value also began to increase rapidly. When the vibration specification was exceeded and the kurtosis value also exceeded the normal value (kurtosis relative standard available), it was considered that the imported bearing of ina had entered the late fault production, and the equipment needed to be repaired in time, Replace the bearing.Specified conditions for regular inspection of SKF imported bearings
The larger the equipment capacity, the bearing shows the characteristics of late failure, and the time from the occurrence of serious failure (generally bearing damage, such as shaft holding, burn, sand frame crack, raceway, bead wear, etc.) is usually less than one week.
The faster the speed, the shorter the interval. Therefore, in the actual bearing fault diagnosis, once the late fault characteristics are found, the bearing fault should be determined and the maintenance should be arranged as soon as possible.Specified conditions for regular inspection of SKF imported bearings
The assembly quality index of ina imported bearings, that is, the assembly accuracy requirements are mainly radial clearance and width. There is a certain functional relationship between axial clearance and radial clearance. Therefore, the axial clearance can be indirectly controlled by controlling the radial clearance.
For deep groove ball bearings, cylindrical roller bearings, self-aligning ball bearings and self-aligning roller bearings, the radial clearance is mainly controlled.Specified conditions for regular inspection of SKF imported bearings
For thrust ball bearing, thrust roller bearing and tapered roller bearing, the height and width are mainly controlled.
For angular contact ball bearings, the contact angle is mainly controlled.Specified conditions for regular inspection of SKF imported bearings
The basic requirements of rolling bearing assembly are: on the premise of ensuring the assembly quality index, the sleeve rate should be high, which should generally be more than 95%.
Obvious loose defects are not allowed on the finished ina bearing ring. It will reduce the density of ferrule and enrich more micropores, low melting point impurities, gases and non-metallic inclusions Like the ribbon carbide, it plays the role of dividing the continuity of the matrix, causing component segregation and matrix embrittlement, which greatly reduces the comprehensive mechanical properties of the ferrule.Specified conditions for regular inspection of SKF imported bearings
The black-and-white concentration difference of martensite matrix in quenching and tempering state, high macro hardness value and loose defects are also potential factors that can not be ignored to induce grinding cracks. The appearance of black-and-white concentration difference indicates that there are serious banded carbides in the original structure, resulting in the segregation of carbon lattice concentration on and between bands. Therefore, after quenching, the overheating tendency between bands and the difference of MS point are increased.Specified conditions for regular inspection of SKF imported bearings
The influence of grinding quality on the premature failure of ina bearing can be judged from the above test results. The grinding crack and grinding burn on one side of the raceway are a direct cause of the collapse of the ferrule and the premature failure of the bearing. Specified conditions for regular inspection of SKF imported bearings
The macro morphology of the crack and the distribution characteristics of grinding burn revealed in this example show that the original position of the raceway is too deviated or the R of the raceway is not round, which increases the grinding allowance on one side of the raceway. Specified conditions for regular inspection of SKF imported bearings
When the feed rate is large in the coarse grinding stage When the grinding speed is fast, the whole raceway produces uneven grinding. If the grinding wheel is not trimmed in time, it will promote the embedding or adhesion of grinding debris, resulting in the blockage and passivation of the grinding wheel pores, which will increase the imbalance of the grinding wheel, aggravate the spindle vibration, and even the grinding chatter caused by the vibration of the machine tool. Obviously, the grinding force changes periodically, forming intermittent burn strips.