Impact of vibration on imported Koyo bearings
Impact of vibration on imported Koyo bearings
2022年5月7日
New technology and process equipment of Timken bearing grinding
New technology and process equipment of Timken bearing grinding
2022年5月9日

Six precautions for selecting NTN imported bearing

  • Whether ina bearing is installed or not will affect the accuracy, service life and performance of the bearing. Therefore, please fully install the INA Bearing, that is, please install the INA Bearing according to the operating standards including the following items.Estimation method of fatigue life of NTN bearing
  • Clean ina bearings and related parts. For bearings that have been greased and with oil seals or dust covers on both sides, the sealing rings need not be cleaned before ina bearings are installed.Estimation method of fatigue life of NTN bearing

Check the size and NTN imported bearing

  • Installation method the installation of bearing shall be determined according to the bearing structure, size and the matching nature of INA Bearing parts. The pressure shall be directly added to the end face of the tightly matched ferrule, and the pressure shall not be transmitted through the rolling element. The bearing installation generally adopts the following methods:Estimation method of fatigue life of NTN bearing
  • Press fit
  • The inner ring of INA Bearing fits tightly with the shaft. When the outer ring fits loosely with the bearing seat hole, press the INA Bearing on the shaft with a press, and then install the shaft together with the bearing into the bearing seat hole. When pressing, pad the end face of ina bearing inner ring with an assembly pipe (copper or mild steel) made of soft metal material. Estimation method of fatigue life of NTN bearing
  • The inner diameter of the assembly sleeve should be slightly larger than the diameter of the journal, and the outer diameter should be slightly smaller than the retaining edge of ina bearing inner ring, Avoid pressing on the holder. Estimation method of fatigue life of NTN bearing
  • The ina bearing outer ring fits tightly with the bearing seat hole. When the inner ring fits loosely with the shaft, the ina bearing can be pressed into the bearing seat hole first. At this time, the outer diameter of the assembly sleeve should be slightly smaller than the diameter of the seat hole.
  •  If the ina bearing ring is tightly matched with the shaft and seat hole, the inner ring and outer ring in the installation chamber shall be pressed into the shaft and seat hole at the same time, and the structure of the assembly sleeve shall be able to press the end faces of the bearing inner ring and outer ring at the same time.Estimation method of fatigue life of NTN bearing
Estimation method of fatigue life of NTN bearing

NTN imported bearing

  • By heating INA Bearing and ina bearing seat, the installation method of changing tight fit into loose fit by thermal expansion. It is a common and labor-saving installation method. This method is suitable for the installation of INA Bearing with large interference. Estimation method of fatigue life of NTN bearing
  • Before hot installation, put the ring of INA Bearing or separable ina bearing into the oil tank and heat it evenly for 80-100 ℃, then take it out of the oil and install it on the shaft as soon as possible. In order to prevent the end face of inner ring and shaft shoulder from not fitting tightly after cooling, ina bearing can be tightened axially after cooling.Estimation method of fatigue life of NTN bearing 
  • When the outer ring of the bearing is tightly matched with the bearing seat made of light metal, the hot installation method of heating ina bearing seat can avoid the scratch of the mating surface. When heating INA Bearing with oil tank, there should be a mesh grid at a certain distance from the bottom of the box, or hang the bearing with hook. Estimation method of fatigue life of NTN bearing
  • The bearing cannot be placed on the bottom of the box to prevent sinking impurities from entering the bearing or uneven heating. There must be a thermometer in the oil tank, and the oil temperature must be strictly controlled not to exceed 100 ℃ to prevent tempering effect and reduce the hardness of the ferrule.Estimation method of fatigue life of NTN bearing
  • Installation of tapered bore bearing
  • The tapered hole bearing can be directly installed on the journal with taper, or on the conical surface loaded with the set sleeve and the release sleeve. The tightness of its fit can be measured by the reduction of the radial clearance of INA Bearing. Therefore, the radial clearance of INA Bearing should be measured before installation, and the clearance should be measured frequently during installation to achieve the required reduction of clearance. Generally, lock nut installation or heating installation can be used during installation.Estimation method of fatigue life of NTN bearing

Installation of NTN bearing

  • The fit between the circumference of the thrust bearing and the shaft is generally a transition fit, and the fit between the race and the ina bearing seat hole is generally a clearance fit. Therefore, this ina bearing is easy to install. The middle shaft spring of the two-way thrust ina bearing should be fixed on the shaft to prevent rotation relative to the shaft. Estimation method of fatigue life of NTN bearing
  • Estimation method of fatigue life of NTN bearingGenerally, the installation method of bearing is mostly shaft rotation, so the fit between inner ring and shaft is win-win fit, and the fit between ina bearing outer ring and bearing chamber is clearance fit. There are two methods to estimate the fatigue life of NTN bearings: calculation method and test method.Estimation method of fatigue life of NTN bearing
  • The fatigue life of NTN bearing calculated according to the specified formula and calculation rules is used as the calculated fatigue life. The calculated total rotation value is specified as the total rotation value when the inner ring or shaft ring rotates (at this time, the outer ring or seat ring is fixed).
  • According to the specified standard test method (rolling NTN bearing fatigue life test specification), a testing machine that can meet the requirements specified in the method in terms of service performance shall conduct sampling fatigue life test on a batch of NTN bearings. The actual test life obtained from the test data processing is the fatigue test life of the batch of NTN bearings represented by the tested NTN bearings.Estimation method of fatigue life of NTN bearing
  • The fatigue life test of rolling bearing is a kind of strengthened fatigue life test method, which can fully lubricate and restrain the wear factors of rolling NTN bearing to a great extent. It adopts strengthened load and speed to highlight the fatigue factors of NTN bearing.Estimation method of fatigue life of NTN bearing
  • The calculation method of NTN bearing fatigue life and fatigue life test complement each other, and the results obtained by them have sufficient correspondence.Estimation method of fatigue life of NTN bearing
  • In fact, for each specific application, a sufficient number of NTN bearings are selected for life test to verify whether the selected NTN bearings are suitable, which is very huge in economy, time and labor. Therefore, the test method of NTN bearing life is only used when it is very necessary or important. In most cases, the standard life calculation method is used to estimate the service life of NTN bearings, There is a sufficient degree of dependability. Estimation method of fatigue life of NTN bearing
  • According to the service time, the motor should be cleaned and refueled after 2000 hours. SKF imported bearings can be cleaned in the following two ways:Estimation method of fatigue life of NTN bearing
  • Hot oil cleaning method because it has been used for a long time, SKF hardened with soft dry oil or antirust paste is only imported bearings. It should be immersed in 100-200 ℃ hot engine oil, clamp SKF bearings with pliers, and clean the oil stain on SKF bearings with a brush. The soft dry oil or antirust paste will melt when heated to 100-200 ℃, which is easy to wash out from the gap of SKF Bearing. Sometimes just shake the bearing in the oil for many times. Oil will also flow away from the gap.Estimation method of fatigue life of NTN bearing
  • When cleaning the centripetal spherical bearing of old motor or imported motor, the ball, bead frame and inner ring should be turned laterally from the outer ring and then immersed in hot oil. When cleaning the short cylindrical roller bearing, the roller, bead frame, inner ring and outer ring should also be separated.Estimation method of fatigue life of NTN bearing

During hot oil cleaning, the oil temperature NTN imported bearing 

  • When heating directly with open fire, attention should be paid to prevent the oil from burning. SKF Bearing should be hung in the oil pan. Sinking the bottom will cause overheating and reduce the hardness.Estimation method of fatigue life of NTN bearing
  • General cleaning method: soak SKF Bearing in kerosene for 5-10 minutes, hold the inner ring with one hand and rotate the outer ring with the other hand, and the dry oil or antirust paste on SKF Bearing will fall off. Then put the SKF Bearing into clean kerosene, brush it with a soft brush, clean the oil stain in the ball and gap, and then put it into gasoline for cleaning once. Take it out and put it on clean paper. When cleaning centripetal spherical ball bearings and short cylindrical roller bearings, the ball, bead holder, inner ring and outer ring shall be separated for cleaning.Estimation method of fatigue life of NTN bearing
  • The SKF Bearing installed on the shaft is cleaned mainly by spraying oil or spraying with an oil gun. The oil stains that are easy to be cleaned are first cleaned with kerosene and then gasoline; For oil stains that are difficult to be cleaned, first wash them with 100-200 ℃ hot engine oil or spray them with an oil gun, and then clean them with gasoline. Estimation method of fatigue life of NTN bearing
  • Be careful not to scrape the SKF imported bearing with sharp tools: hard oil dirt or rust, so as not to damage the smoothness of the SKF Bearing rolling body and groove ring. The cleaned SKF Bearing shall be wiped dry with a clean cloth. Whether the outer packaging is clear: generally, the brands of the main factory have their own special designers to design the outer packaging, and arrange the factories with qualified production conditions for production. Therefore, the packaging is very clear from line to color block ­,Estimation method of fatigue life of NTN bearing
  • Whether the steel seal words are clear: brand words, labels, etc. will be printed on the fag imported bearing body. The font is very small, but most of the products produced by the original factory use steel printing technology, and they are pressed before overheating treatment. Therefore, although the font is small, it is concave ­ Deep, very clear. The font of counterfeit products is not only fuzzy, but also floating on the surface due to the rough printing technology. Some of them can even be easily erased by hand.Estimation method of fatigue life of NTN bearing
  • Whether there is any noise: hold the fag imported bearing body sleeve with your left hand, and turn the sleeve with your right hand to listen for any noise. Due to the backward production conditions of most counterfeit products and complete manual workshop operation, sand will inevitably be mixed in the production process ­ A kind of impurity is hidden in the fag imported bearing body, so it will make a noise when rotating. This is a big difference from the factory brand that strictly implements production standards and operates with machines.Estimation method of fatigue life of NTN bearing
  • Whether there is muddy oil on the surface: this should be paid special attention when purchasing fag imported bearings. As the current domestic antirust technology is not particularly good, it is easy to leave thick oil stains when antirust the imported fag bearing body, and it is sticky when holding it in your hand. However, there is almost no trace of antirust oil on the imported fag bearing, but a particularly careful expert said that the imported fag bearing smells like a smell. It must be antirust oil, but you can’t see it.Estimation method of fatigue life of NTN bearing
  • Whether the chamfering is uniform: the so-called chamfering of fag imported bearings is the junction of horizontal and vertical surfaces. Due to the limitation of production technology, the fake fag imported bearings are not handled satisfactorily in these corners.Estimation method of fatigue life of NTN bearing

The feature of NTN imported bearing

  • Fag bearing shall rotate flexibly without blocking feeling after being pressed into the bearing. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large and the tolerance should be reduced. If the fag bearing is pressed into the shaft and rotates by hand with an obvious “rusty” feeling, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. Therefore, when controlling the tolerance of shaft and bearing chamber, it is also necessary to control the roundness. At present, many domestic manufacturers only control the tolerance, not the roundness.
  • Because fag bearing is a high-precision product, if it is not assembled properly, it is easy to damage the fag bearing channel, resulting in the damage of fag bearing. Fag bearing shall be equipped with a special mold during assembly, which can not be knocked at will. When pressing the shaft, it can only be stressed by a small ring, and when pressing a large ring, it can only be stressed by a large ring. Pneumatic or hydraulic pressure is required during assembly. During press assembly, the upper and lower molds shall be outside the horizontal state. If there is inclination, the fag bearing channel will be damaged due to stress and the fag bearing will make a sound.
  • When fag bearing is installed on the rotor for dynamic balance, it is easy to enter the iron filings generated during dynamic balance into fag bearing. Therefore, dynamic balance is performed before fag bearing is installed. In order to facilitate assembly, some manufacturers apply some oil or grease in the bearing chamber for lubrication effect during assembly, but it is often difficult for operators to control the amount. If there is a large amount of oil or grease in the fag bearing chamber, it is easy to enter the fag bearing along the shaft when the fag bearing rotates. In Japan, FAG bearing chamber should not be coated with oil or grease. If it must be coated, it should be controlled and there should be no accumulation in the bearing chamber.
  • The feature of paint rust is that it often occurs in sealed motors. The sound of the motor is very good during assembly, but after it is put in the warehouse for some time, the abnormal noise of the motor becomes very large, and there is serious rust when removing fag bearings. In the past, many manufacturers thought it was the problem of fag bearing. After our continuous publicity, the motor factory has realized that the main problem is the insulating paint. The main reason for this problem is that the acidic substances volatilized from the insulating paint form corrosive substances at a certain temperature and humidity, which corrodes the fag bearing channel and leads to the damage of fag bearing. At present, the problem can only be to select good insulating paint and assemble after drying and ventilation for a period of time.
  • The service life of fag bearing is closely related to manufacturing.

  • assembly and use. Only by doing well in each link can fag bearing be in the running state, so as to prolong the service life of fag bearing.
  • After moving for a period of time, the vibration and noise maintain a certain level, and the spectrum is very single, with only one or two times the frequency. The frequency spectrum above three times of power frequency rarely appears, and the state of fag bearing is very stable and enters the stable working period.
  • After continued operation and entering the later stage of use, the vibration and noise of fag bearing began to increase, and sometimes abnormal sound appeared, but the change of vibration increase was slow. At this time, the kurtosis value of fag bearing began to suddenly reach a certain value. We believe that fag bearing shows initial failure at this time.
  • At this time, it is required to closely monitor the fag bearing and pay close attention to its changes. Since then, the kurtosis value of fag bearing 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. When the vibration exceeded the vibration standard (such as ISO2372 standard), the kurtosis value of fag bearing also began to increase rapidly. When both the vibration standard and the kurtosis value also exceeded the normal value (the relative kurtosis standard can be used), the fag bearing has entered the late fault production, and the equipment needs to be repaired in time, Replace the rolling fag bearing.
  • Fag bearing shows the characteristics of late failure. The time from the occurrence of serious failure (generally fag bearing damage, such as shaft holding, burn, sand frame crack, raceway, bead wear, etc.) is mostly less than one week. The larger the equipment capacity, the faster the speed, and the shorter the interval. Therefore, in the actual rolling fag bearing fault diagnosis, once the late fault characteristics are found, the fag bearing should be determined to have a fault and the maintenance should be arranged as soon as possible