Factors affecting the tolerance of NTN combined bearings and their solutions
Factors affecting the tolerance of NTN combined bearings and their solutions
2022年6月4日
Comprehensive calibration method for routine inspection and maintenance of NTN one-way bearing
Comprehensive calibration method for routine inspection and maintenance of NTN one-way bearing
2022年6月6日

Effect of regular maintenance on service life of Timken cross roller bearing

The reasons for the cracks cross roller bearing

  • There are uneven pits on the contact surface between the raceway and the roller of INA Bearing, which indicates that the four row cylindrical roller bearing produces plastic deformation. The reason is that the local stress on the working surface of the bearing exceeds the yield limit of the material under the action of large static load or impact load, which usually occurs on the bearing rotating at low speed.Effect of regular maintenance on service life of Timken cross roller bearing
  • The reasons for the cracks in the bearing race may be that the bearing fits too tightly, the bearing is foreign or the inner ring is loose, the containing parts of INA Bearing are deformed, and the surface processing of the installed bearing is poor.Effect of regular maintenance on service life of Timken cross roller bearing
  • Under the action of instantaneous high temperature, the steel surface reacts with oxygen in the air to form a very thin layer (20 ~ 30nm) of iron oxide. It should be noted that there is a corresponding relationship between the thickness of oxide layer and the total thickness of surface grinding metamorphic layer. This shows that the thickness of oxide layer is directly related to the grinding process and is an important symbol of grinding quality.Effect of regular maintenance on service life of Timken cross roller bearing
  • It is common for ina bearing to break down during operation, so there is no need to make a fuss. When a fault occurs, judgment and handling is the key. The reasons for the high temperature of four row cylindrical roller bearings are: the quality of lubricating oil does not meet the requirements or deteriorates, and the viscosity of lubricating oil is too high; The mechanism assembly is too tight (insufficient clearance); The bearing assembly is too tight;Effect of regular maintenance on service life of Timken cross roller bearing
  • Tile surface corrosion: abnormal concentration of non-ferrous metal elements is found by spectral analysis; There are many sub micron wear particles composed of non-ferrous metals in ferrography; The water content and acid value of lubricating oil exceed the standard.Effect of regular maintenance on service life of Timken cross roller bearing
  • Journal surface strain: there are ferrous cutting abrasive particles or black oxide particles in the Ferrograph, and there is tempering color on the metal surface.Effect of regular maintenance on service life of Timken cross roller bearing
  • Journal surface corrosion: abnormal concentration of iron element is found through spectral analysis. There are many submicron particles of iron composition in the ferrogram, and the water content or acid value of the lubricating oil exceeds the standard.Effect of regular maintenance on service life of Timken cross roller bearing
  • Surface strain: cutting abrasive particles are found in the Ferrograph, and the abrasive particles are composed of non-ferrous metals.Effect of regular maintenance on service life of Timken cross roller bearing
  • Fretting wear on the back of the pad: abnormal iron concentration is found through spectral analysis. There are many iron components, submicron wear particles, and abnormal moisture and acid value of the lubricating oil in the Ferrograph.Effect of regular maintenance on service life of Timken cross roller bearing
  • Under the condition of liquid lubrication, the sliding surface is separated by the lubricating oil without direct contact, which can also greatly reduce the friction loss and surface wear. The oil film also has a certain vibration absorption capacity
  • In the grinding process, the contact area between the grinding wheel and the workpiece consumes a lot of energy and generates a lot of grinding heat, resulting in local instantaneous high temperature in the grinding area. It is found that the instantaneous temperature in the grinding zone can be as high as 1000 ~ 1500 ℃ within 0.1 ~ 0.001ms by deducing and calculating the heat transfer theoretical formula of linear moving heat source or measuring the instantaneous temperature under the experimental conditions by using infrared ray method and thermocouple method. Effect of regular maintenance on service life of Timken cross roller bearing
  • Such an instantaneous high temperature is enough to cause high-temperature oxidation, amorphous structure, high-temperature tempering, secondary quenching, and even burn cracking of the surface layer at a certain depth of the working surface.Effect of regular maintenance on service life of Timken cross roller bearing
  •  Usually, it is supported radially and axially by two double row tapered roller bearings, and one side of the bearing is called the fixed end bearing, which bears the radial and axial load types of the two fixed shafts and the axial displacement relative to the bearing housing. Effect of regular maintenance on service life of Timken cross roller bearing
  • The other side will be known as the free end, which can only bear the radial load and the axial relative motion. The fixed end double row tapered roller bearing must be compared with the fixed shaft and bearing housing. The more suitable bearing can bear, but the installation must maintain a certain radial bearing housing spacing.Effect of regular maintenance on service life of Timken cross roller bearing
  •  Due to the thermal expansion of the axial length change of the free end Koyo bearing, there is no extrusion in the double row tapered roller bearing. Axial displacement occurs in the bearing collar and may also occur with the bearing in the bearing.Effect of regular maintenance on service life of Timken cross roller bearing
  • The basic performance requirements of materials for Koyo bearings depend on the working characteristics of double row tapered roller bearings
Effect of regular maintenance on service life of Timken cross roller bearing

The reason is that the local stress on the working cross roller bearing

  • Effect of regular maintenance on service life of Timken cross roller bearingA
  • When the inspection of Timken cross roller bearing equipment is suspended during regular maintenance, operation and replacement of peripheral parts, it is required to judge whether Timken cross roller bearing parts can be used again and record the good or bad application conditions.cross roller bearing
  • Secondly, check whether the raceway surface, rolling surface and joint surface of the bearing and the wear condition of the standoff frame are damaged or abnormal. In particular, check the running track of the raceway surface. To judge whether Timken cross roller bearing can be used again, we should make a decision after considering the level of bearing damage, mechanical function, priority, operation premise, search and inspection cycle, etc.cross roller bearing
  • Search and inspection results. If Timken cross roller bearing is found damaged or abnormal, please find out the notice according to the phenomenon of bearing damage and formulate countermeasures. In addition, the search and inspection results, if there are several defects below, the bearing can no longer be used, and it needs to be replaced with a new bearing.cross roller bearing
  • If the flow bearing is used in harsh environment, the bearing seal ring and seal cover are essential, because they can prevent dirt from invading and prolong the service life of the bearing. Rolls in rolling mills are usually supported by Timken cross roller sub bearings. It is required to bear strong impact load and invasion of water and debris during use.cross roller bearing
  • The negative pressure generated in the bearing can cause water to invade from the main seal, and the structure of the hole seal has a great impact on the negative pressure. Therefore, reducing the negative pressure in Timken cross roller bearing is the basic requirement to prevent water from entering. cross roller bearing
  • The effective method is to make the hole seal not directly contact with water, while retaining the original function of the hole seal – to prevent water and dirt from invading from the side of the roll neck. The sealing method adopts surface contact instead of line contact.cross roller bearing
  •  The surface contact hole sealing has the characteristics of good sealing performance in both the running process and the static process. Therefore, the new super capacity sealed clean bearing has higher reliability than the traditional sealed bearing.cross roller bearing
  • Under severe lubrication conditions, the load of the bearing is increased by 34%, and the bearing has high reliability, long service life and easy maintenance. This performance improvement is the result of optimizing mechanical design, adopting new materials and patented sealing technology. Compared with the traditional Timken cross roller bearing, this Timken cross roller bearing not only increases the basic rated dynamic load by 34%, but also prolongs the service life by 2.7 times.cross roller bearing

Under severe lubrication conditions cross roller bearing

  • Bearing radial load
  • The ina bearing that mainly receives radial load is the radial bearing. The nominal contact angle of this type of bearing A0 > =450. The radial load of roller bearings with dimensional communication is larger than that of ball bearings.cross roller bearing
  • N-type and nu type cylindrical roller bearings can only accept radial load, and other types of radial bearings can accept both radial load and axial load.cross roller bearing
  • Axial load of bearing
  • INA Bearing, which mainly accepts axial load, is generally called thrust bearing, and its nominal contact angle a0>450. Thrust bearing and thrust angular contact ball bearing can also accept one or two inclined axial forces according to their structural differences.cross roller bearing
  • Under the radial load, the INA Bearing will produce the force acting on the axial direction, which is generally borne by the second bearing.cross roller bearing
  • In a bearing configuration consisting of two single row angular contact ball bearings or two tapered roller bearings back-to-back or face-to-face, each bearing must withstand the axial force from the other bearing. When the two bearings are the same, the radial load acts on the center of the two bearings. If the bearing configuration is adjusted to zero clearance, the load distribution can be achieved automatically when half of the components bear the load.cross roller bearing
  •  It should be remembered that rigidity is affected not only by the elasticity of the bearing, but also by the elasticity of the shaft and bearing pedestal, the installation fit of the ina bearing ring, and the elastic deformation of all other components in the stress field, including the support. These factors have considerable influence on the elasticity of the whole shaft system.cross roller bearing
  •  If it is found that the temperature is very high, stop the equipment immediately, find out the cause, and deal with it according to the solutions provided above. However, the solutions may be different due to the different causes of the heating of the plane thrust ball bearing. Therefore, it is still necessary to deal with the specific situation with the help of technicians.cross roller bearing
  • If you carefully observe the running track, you will know that it only bears radial load, large axial load, moment load, or extreme uneven rigidity on the bearing housing. It can be checked whether the plane thrust ball bearing is loaded with unexpected load and whether the installation error is too large, which becomes a clue to investigate the damage cause of the outer spherical bearing.cross roller bearing
  • When the bearing temperature rises, first judge whether there is misoperation. If it does rise, the following measures shall be taken:
  • Incorrect installation position of the bearing will cause large axial force between the ball end face and the inner race and outer race of the bearing seat, resulting in overheating of the bearing.
  • SKF bearings used shall be of the specified accuracy grade.cross roller bearing
  • The main shaft of the plane thrust ball bearing in use is bent or the box hole is not concentric, resulting in heating. The solution is to repair the main shaft
  • The solution to heating caused by too tight bearing belt is to adjust the belt to ensure proper tightness.
  • The solution to heating caused by poor lubrication is to select the specified brand of lubrication data and properly clean them.
  • The solution of heating caused by low assembly quality is to improve the assembly quality.
  • The solution to the heating caused by the running ring of the inner shell of the plane thrust ball bearing is to replace the bearing and related worn parts, correct the diameter of the impeller balance hole and verify the static balance value
  • The solution to heating caused by too large axial force is to clean and adjust the clearance requirements of sealing ring
  • The solution to the heating caused by the damage of rolling bearing is to replace the plane thrust ball bearing. When we use SKF bearings,cross roller bearing
  • Lubrication is very important, not only for bearings, but also for all bearings. However, please note that the bearing should not be greased too much. Then it is time to change the lubricant of the bearing. After the old engine oil is removed from the plane thrust ball bearing lubricated with engine oil, if possible, it should be refilled with fresh engine oil and the machine should be rotated at low speed for several minutes. Make the oil collect residual pollutants as much as possible, and then drain the oil. cross roller bearing
  • When replacing the grease of the plain thrust ball bearing lubricated with grease, the stripper used shall avoid any part of the outer spherical bearing with cotton. Because these residual fibers may wedge between the rolling parts and cause damage, especially in the application of small bearings.
  • When using SKF Bearing, if it is to be used, it is necessary to check the plane thrust ball bearing to check its vibration amplitude, sound, temperature and lubricant (whether there are changes in color and viscosity, and whether there are foreign matters). 
  • Keep in mind that the amount of lubricant used must be moderate. If there is too much waste, it will not play its due role. In the process of use, do not exceed the limit speed. If the operating temperature exceeds 100 ℃, the oil should be replaced 2-3 times a year.
  • Steps to find out the cause of NTN bearing damage in case of abnormal operation of the bearing, the cause shall be found out in time and the fault shall be eliminated. After a certain period of service, the sliding bearing will always fail or be damaged.
  • If the damage is analyzed and corresponding countermeasures are taken, its service life and working reliability can be improved, the maintenance times and costs of the main engine can be reduced, and the service life of the main engine can be prolonged. The following are the characteristics of common damage forms of bearings, the search and analysis methods of damage causes, and the effective measures to avoid or slow down such damage.
  • The sound comes from the lower part of the cylinder block near the crankcase. The oil pressure drops significantly. The engine vibrates the throttle valve at low and medium speed, giving out obvious and dull continuous knocking sound accompanied by engine vibration.
  • When the engine runs at high speed, the engine body vibrates greatly and the oil pressure drops significantly, it is because the clearance between the sliding bearing and the journal is too large or the bearing alloy is ablated and falls off.
  • The sound of the single cylinder fire break test changes little, but the sound of the adjacent two cylinders decreases or disappears obviously when the fire breaks, which is the sound of the crankshaft NTN bearing between the two cylinders.
  • If the engine body vibrates a lot at low speed, there is a phenomenon of swinging and shaking, and a heavy and large “bang bang” knocking sound is emitted at the same time, it means that the crankshaft is broken.
  • The sound increases with the increase of temperature. At high speed, the sound becomes disordered, which may be due to the bending of the crankshaft.
  • Before disassembling the damaged bearing, review the calculated load, calculated speed and other original data of NTN bearing, and pay attention to whether there are omissions or errors in the original design
  • Check whether the actual load and speed of the bearing are different from the original ones, and whether the sliding bearing is correctly selected;
  • Understand the abnormal phenomena during and near damage, especially the appearance and evolution of noise and heat; Pay attention to check whether the power supply and the adjacent mechanical components of NTN bearing have abnormal phenomena during this period. Analyze the type of noise, the level of tone, and the interference rhythm of frequency: pay attention to when the temperature suddenly increases, and write down the power supply and other parts;
  • Find out the configuration and matching characteristics of the sliding bearing in the main engine, judge whether it is properly configured, and record the position of the ferrule relative to the housing and the load direction;
  • Manually rotate the shaft and the damaged NTN bearing for several turns to experience the heaviness of operation, and then push the shaft back and forth several times along the axial direction to experience the tightness of the shaft along the axial direction. If necessary, measure the deflection of the shaft;
  • Check the position of the bearing and find out the lubrication; Check whether the lubricant brand and sealing method are correct. Pay attention to whether the bearing temperature exceeds the temperature limit of the lubricant used in case of temperature rise. 
  • Focus on checking whether the oil level is high or low, whether the sealing clearance is leaking oil or grease, whether moisture, dust or other foreign matters have invaded the sliding bearing, and whether the grease supply system is faulty
  • Check whether there is any vibration source affecting the NTN bearing. Debris or particle source, water source or fluid pollution source, and current source that can flow through the bearing;
  • According to the inspection, it can be used as a basis to judge whether the damage of NTN bearing is due to fretting corrosion, wear, corrosion or electric corrosion.