What is a rolling bearing
What is a rolling bearing?
Rolling bearing is a kind of precision mechanical element that changes the sliding friction between the running shaft and the shaft seat into rolling friction, so as to reduce the friction loss. Rolling bearing is generally composed of inner ring, outer ring, rolling element and cage. The function of inner ring is to match with the shaft and rotate with the shaft; The function of the outer ring is to cooperate with the bearing seat and play a supporting role; The rolling element is evenly distributed between the inner ring and the outer ring with the help of the cage. Its shape, size and quantity directly affect the service performance and service life of the rolling bearing; The cage can make the rolling elements evenly distributed, guide the rolling elements to rotate and lubricate.
Function of rolling bearing
Support the rotating shaft and parts on the shaft, and maintain the normal working position and rotation accuracy of the shaft. The rolling bearing has the advantages of convenient use and maintenance, reliable operation, good starting performance and high bearing capacity at medium speed. Compared with sliding bearing, rolling bearing has larger radial size, poor damping capacity, low service life and large sound at high speed.
Structure of rolling bearing
The structure of rolling bearing consists of:
- 1. Outer ring – installed in the bearing seat hole and generally does not rotate;
- 2. Inner ring – installed on the journal and rotates with the shaft;
- 3. Rolling element – the core element of rolling bearing;
- 4. Cage – evenly separate the rolling elements to avoid friction.
Lubricant is also considered to be the fifth largest part of rolling bearing. It mainly plays the role of lubrication, cooling and cleaning.
Characteristics of rolling bearing
In the processing of bearing parts, a large number of special bearing equipment are used. For example, ball grinding machine, grinder and other equipment are used for steel ball processing. The characteristics of specialization are also reflected in the production of bearing parts, such as steel ball companies specializing in the production of steel balls, micro bearing factories specializing in the production of micro bearings, etc.
2. Advanced nature
Due to the large-scale requirements of bearing production, it is possible to use advanced machine tools, tooling and technology. Such as CNC machine tools, three jaw floating chuck and protective atmosphere heat treatment.
The specialization of bearing production provides conditions for its production automation. Full automatic, semi-automatic special and non special machine tools are widely used in production, and automatic production lines are gradually popularized and applied. Such as automatic heat treatment line and automatic assembly line.
Basic characteristics of rolling bearing
Benefits of rolling bearings
- (1) Significant energy saving. Due to the motion characteristics of rolling bearing, its friction is far less than that of sliding bearing, which can reduce the power consumption in friction resistance, so the energy-saving effect is remarkable. From the theoretical analysis and production practice, the general small ball mill with rolling bearing as the main bearing saves electricity by 30% – 35%, the medium ball mill saves electricity by 15% – 20%, and the large ball mill saves electricity by 10% – 20%. As the ball mill itself is a large energy consumer in production, it will mean that a considerable cost can be saved.
- (2) Convenient maintenance and reliable quality. The use of rolling bearings can save a series of complex maintenance processes such as melting, casting and scraping of Babbitt alloy materials, as well as oil supply, water supply and cooling systems with high technical requirements, so the maintenance amount is greatly reduced. Moreover, the quality of rolling bearings is often guaranteed because they are manufactured by professional manufacturers. It also brings convenience to the ball mill manufacturers.
Advantages of rolling bearing
- 1. Low friction resistance, low power consumption, high mechanical efficiency and easy to start;
- 2. Standardized size, interchangeability, easy installation, disassembly and maintenance;
- 3. Compact structure, light weight and smaller axial size;
- 4. High precision, large load, small wear and long service life;
- 5. Some bearings have self-aligning performance;
- 6. Suitable for mass production, stable and reliable quality and high production efficiency;
- 7. The transmission friction torque is much lower than that of hydrodynamic bearing, so the friction temperature rise and power consumption are low;
- 8. The starting friction torque is only slightly higher than the rotating friction torque;
- 9. The sensitivity of bearing deformation to load change is less than that of hydrodynamic bearing;
- 10. Only a small amount of lubricant is required for normal operation, and lubricant can be provided for a long time during operation;
- 11. The axial dimension is smaller than that of traditional hydrodynamic bearing;
- 12. It can bear combined radial and thrust loads at the same time;
- 13. In a large load speed range, the unique design can obtain excellent performance;
- 14. The bearing performance is relatively insensitive to the fluctuation of load, speed and running speed.
Disadvantages of rolling bearing
- 1. Loud noise.
- 2. The structure of bearing pedestal is complex.
- 3. High cost.
- 4. Even if the bearings are well lubricated, installed correctly, dustproof and moisture-proof, and operate normally, they will eventually fail due to the fatigue of the rolling contact surface.
Performance of rolling bearing
When the shaft centerline is inclined relative to the centerline of the bearing seat hole, the bearing can still work normally. Double row centripetal spherical ball bearings and double row centripetal spherical roller bearings have good centering performance. Roller bearing and needle roller bearing shall not have relative inclination of inner and outer ring axes. The allowable inclination angles of various rolling bearings are different, such as 8 ‘- 16’ for single row centripetal ball bearings, 2 ° – 3 ° for double row centripetal spherical ball bearings, and ≤ 2 ‘for tapered roller bearings.
Limit speed is the maximum speed allowed by the bearing under certain load and lubrication conditions. The limit speed is related to bearing type, size, accuracy, clearance, cage, load and cooling conditions. The working speed of the bearing shall be lower than the limit speed. The limit speed can be increased by selecting high-precision bearings, improving cage structure and materials, adopting oil mist lubrication and improving cooling conditions.
Mainly grease lubrication and oil lubrication. Grease lubrication is not easy to leak, easy to seal, long service time, simple maintenance and high oil film strength, but the friction torque is larger than oil lubrication, so it is not suitable for high speed. The filling amount of grease in the bearing shall not exceed 1/2-1/3 of the bearing space, otherwise the bearing will overheat due to excessive mixing lubricant. Oil lubrication has good cooling effect, but the sealing and oil supply devices are complex. The viscosity of oil is generally 0.12-0.2 cm/s. When the load is large and the working temperature is high, the oil with high viscosity should be selected, and when the rotating speed is high, the oil with low viscosity should be selected. Lubrication methods include oil bath lubrication, drip lubrication, oil mist lubrication, oil injection lubrication and pressure oil supply lubrication. During oil bath lubrication, the oil level shall not be higher than the center of the lowest rolling element. If the bearing is designed and the lubricant viscosity is selected according to the hydrodynamic lubrication theory of elastic fluid, the contact surface will be separated by oil film. At this time, under the action of stable load, the service life of bearing can be increased many times.
Modern machines, instruments and other equipment are developing towards high speed, heavy load, precision and lightness, which puts forward many new requirements for rolling bearings. For example, while reducing the size, the bearings are required to maintain or even increase the rated load, and new technologies are adopted to improve the process, improve the manufacturing accuracy and reduce the cost. Universal rolling bearings have been difficult to meet various requirements. Special bearings should be designed and manufactured for machines and equipment with large production capacity. While strengthening standardization, varieties should be increased and the proportion of special bearings should be expanded. The development of modern industry also needs special bearings working under special working conditions, such as bearings working at high speed, high temperature, low temperature, strong magnetic field or in acid, alkali and other media.
Classification of rolling bearings
Classification by structure type
According to the structure of rolling element and ferrule, it can be divided into:
Deep groove ball bearing, needle roller bearing, angular contact bearing, self-aligning ball bearing, self-aligning roller bearing, thrust ball bearing, thrust self-aligning roller bearing, cylindrical roller bearing, tapered roller bearing, outer spherical ball bearing with seat, etc.
Rolling bearings can be divided into:
1. Deep groove ball bearing
Deep groove ball bearing has the advantages of simple structure and convenient use. It is a kind of bearing with the largest production batch and the widest application range. It is mainly used to bear radial load and certain axial load. When the radial clearance of the bearing increases, it has the function of angular contact bearing and can bear large axial load. Used in automobiles, tractors, machine tools, motors, water pumps, agricultural machinery, textile machinery, etc.
2. Needle roller bearing
Needle roller bearings are equipped with thin and long rollers (the roller length is 3 – 10 times the diameter, and the diameter is generally no more than 5mm). Therefore, the radial structure is compact. Its inner diameter size and load capacity are the same as other types of bearings, and its outer diameter is the smallest. It is especially suitable for the supporting structure with limited radial installation size. According to different application occasions, the bearing without inner ring or needle roller and cage assembly can be selected. At this time, the journal surface and shell hole surface matched with the bearing are directly used as the inner and outer rolling surfaces of the bearing. In order to maintain the same load capacity and operation performance as the bearing with ferrule, The hardness, machining accuracy and surface quality of the raceway surface of the shaft or housing hole shall be similar to that of the raceway of the bearing ring. This kind of bearing can only bear radial load. For example: universal joint shaft, hydraulic pump, sheet mill, rock drill, machine tool gearbox, automobile and tractor gearbox, etc.
3. Angular contact bearing
The ultimate speed of angular contact ball bearing is high. It can bear both meridional load and axial load, and can also bear pure axial load. Its axial load capacity is determined by the contact angle and increases with the increase of contact angle. Mainly used for: oil pump, air compressor, various transmissions, fuel injection pump, printing machinery.
4. Self aligning ball bearing
The self-aligning ball bearing has two rows of steel balls, the inner ring has two raceways, and the outer ring raceway is of inner spherical shape, which has the performance of automatic self-aligning. It can automatically compensate the coaxiality error caused by the winding of the shaft and the deformation of the shell, and is suitable for the parts where the strict coaxiality cannot be guaranteed in the support seat hole. This kind of bearing mainly bears radial load. While bearing radial load, it can also bear a small amount of axial load. It is usually not used to bear pure axial load. If it bears pure axial load, only one row of steel balls are stressed. It is mainly used in agricultural machinery such as combine harvester, blower, paper machine, textile machinery, woodworking machinery, traveling wheel and transmission shaft of bridge crane.
5. Self aligning roller bearing
Self aligning roller bearing has two rows of rollers, which are mainly used to bear radial load and axial load in either direction. The bearing has high radial load capacity and is especially suitable for working under heavy load or vibration load, but it can not bear pure axial load; It has good centering performance and can compensate the error of the same bearing. Main uses: paper machinery, reducer, railway vehicle axle, rolling mill gearbox seat, crusher, reducer for various industries, etc.
6. Thrust ball bearing
Thrust ball bearing is a separate bearing. The “seat ring” of the shaft ring can be separated from the components of the “cage” steel ball. The shaft ring is a ferrule matched with the shaft, the sitting ring is a ferrule matched with the bearing seat hole, and there is a gap with the shaft. Thrust ball bearing can only bear axial load, one-way thrust ball bearing can only bear axial load in one direction, and two-way thrust ball bearing can bear axial load in two directions. The thrust ball can not limit the radial displacement of the shaft, and the limit speed is very low. One way thrust ball bearing can limit the axial displacement in one direction of shaft and shell, and two-way bearing can limit the axial displacement in two directions. It is mainly used in automobile steering mechanism and machine tool spindle.
7. Thrust roller bearing
The thrust roller bearing is used for bearing the combined axial and meridional load, but the meridional load shall not exceed 55% of the axial load. Compared with other thrust roller bearings, this kind of bearing has lower friction coefficient, higher speed and self-aligning ability. The roller of 29000 bearing is an asymmetric spherical roller, which can reduce the relative sliding between the rod and the raceway in work, and the roller is long, large in diameter, large in number and large in load capacity. It is usually lubricated with oil, and grease can be used for individual low-speed situations. In the design and selection, it shall be preferred. It is mainly used in hydraulic generators, crane hooks, etc.
8. Cylindrical roller bearing
The roller of cylindrical roller bearing is usually guided by two retaining edges of one bearing ring, cage, roller and guide ring form an assembly, which can be separated from another bearing ring, belonging to separable bearing. This kind of bearing is easy to install and disassemble, especially when it is required that the inner and outer rings are interference fit with the shaft and shell. Such bearings are generally only used to bear radial load, and only single row bearings with retaining edges on the inner and outer rings can bear small steady axial load or large intermittent axial load. It is mainly used for large motors, machine tool spindles, axle boxes, diesel engine crankshafts, as well as variable boxes of automobiles and brackets
9. Tapered roller bearing
Tapered roller bearings are mainly used to bear the combined radial and axial load dominated by radial load, while large cone angle tapered roller bearings can be used to bear the combined radial and axial load dominated by axial load. This kind of bearing is a release bearing, and its inner ring (including tapered roller and cage) and outer ring can be installed respectively. In the process of installation and use, the meridional clearance and axial clearance of the bearing can be adjusted, and the rollers used for automobile rear axle hub, large machine tool spindle, high-power reducer, axle bearing box and conveyor can also be pre interference installed.
10. Outer spherical ball bearing with seat
The outer spherical ball bearing with seat is composed of an outer spherical ball bearing with seals on both sides and a cast (or steel plate stamped) bearing seat. The internal structure of the outer spherical ball bearing is the same as that of the deep groove ball bearing, but the inner ring of the bearing is wider than the outer ring. The outer ring has a truncated spherical outer surface, which can be self-aligning when matched with the concave spherical surface of the bearing seat. Usually, there is a gap between the inner hole of the bearing and the shaft. The inner ring of the bearing is fixed on the shaft with jacking screw, eccentric sleeve or tightening sleeve and rotates with the shaft. The bearing with seat has compact structure, convenient loading and unloading and perfect sealing. It is suitable for simple support. It is commonly used in mining, metallurgy, agriculture, chemical industry, textile, printing and dyeing, transportation machinery, etc.
Classification by size
The bearing is sized according to its outer diameter:
- (1) Miniature bearing — bearing with nominal outer diameter less than 26mm.
- (2) Small bearings – Bearings with nominal outside diameter ranging from 28 to 55 mm.
- (3) Small and medium-sized bearings – Bearings with nominal outer diameter ranging from 60 to 115mm.
- (4) Medium and large bearings – Bearings with nominal outer diameter ranging from 120 to 190mm.
- (5) Large bearing – bearing with nominal outer diameter ranging from 200 to 430mm.
- (6) Extra large bearing – bearing with nominal outer diameter ranging from 440 to 2000mm.
- (7) Major bearing — bearing with nominal outer diameter of more than 2000mm.
How to distinguish the quality of bearings
We usually identify the quality of equipment bearings from the following aspects:
Whether the outer packaging is clear? Generally, the brands produced by regular manufacturers have their own special designers to design the outer packaging, and arrange factories with qualified production conditions for production. Therefore, the product packaging should be very clear and unambiguous from lines to color blocks.
Whether the steel seal is clear
Each bearing product will be printed with its brand words and label on the bearing product body. Although the font is very small, the products produced by regular manufacturers use steel printing technology, and press the font before overheating treatment. Therefore, although the font is small, it is deeply concave and very clear. In general, 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 or the manual marks are serious.
Is there any noise
Hold the inner sleeve of the bearing with the left hand, and move the outer sleeve back and forth with the right hand to make it rotate. Listen to whether there is any noise during the operation of the bearing. Due to the backward production conditions of most counterfeit products and complete manual workshop operation, impurities such as dust and sand will inevitably be mixed in the bearing during the production process, so there will be noise or poor operation when the bearing rotates. This is the key to judge whether the products come from the brand products of regular manufacturers with strict production standards and machine operation.
Is there any muddy oil on the surface
Whether there is muddy oil on the surface requires special attention when purchasing imported bearings. As there is still a certain gap between domestic antirust technology and foreign advanced manufacturing countries, it is easy to leave thick oil traces when antirust the bearing body, which feels sticky when touching with hands, while almost no traces of antirust oil can be seen on the bearings originally imported from abroad. According to industry insiders, a particularly careful person can smell a special smell on imported bearings, which is the smell of antirust oil.
Whether the chamfer is uniform
The so-called bearing chamfer is the junction of horizontal and vertical surfaces. Due to the limitation of production technology, counterfeit bearing products are not handled satisfactorily in these corners, which we can easily distinguish.
The packaging is divided into inner packaging and outer packaging. After the bearing is manufactured and passes the inspection, it shall be cleaned and antirust treated, and then put into the inner packaging, so as to achieve the purpose of waterproof, moisture-proof, dust-proof, impact proof, maintaining the quality and accuracy of the bearing and facilitating use and sales.
The inner packaging of bearing is divided into three categories according to the rust proof period:
- ① Short anti rust period packaging: the anti rust period is 3-6 months. It is suitable for bearings that are delivered in large quantities to the same subscriber and put into use in a short time. By mutual agreement, simple packaging is adopted on the principle of convenience.
- ② General rust proof packaging: the rust proof period is one year, which is suitable for general-purpose bearings.
- ③ Long rust proof packaging: the rust proof period is two years. It is suitable for special and precision bearings.
The packaging materials in the bearing include polyethylene plastic cylinder (box), kraft paper, plain and wrinkled polyethylene composite paper, carton, polyethylene or polyethylene plastic film, nylon fastening belt or plastic woven fastening belt, waterproof high-strength plastic belt, linen bag, etc. The above materials shall be qualified in the corrosion resistance test.
Selection of rolling bearing
There are many types of rolling bearings. The following factors can be considered for selection.
a. Magnitude, direction and nature of load
Ball bearings are suitable for light loads, and roller bearings are suitable for heavy loads and impact loads. When the rolling shaft bears pure axial load, thrust bearing is generally selected; When the rolling shaft bears pure radial load, deep groove ball bearing or short cylindrical roller bearing is generally selected; When the rolling shaft bears pure radial load and small axial load, deep groove ball bearing, angular contact ball bearing, tapered roller bearing, self-aligning ball or self-aligning roller bearing can be selected; When the axial load is large, angular contact ball bearings and tapered roller bearings with large contact angle can be selected, or centripetal bearings and thrust bearings can be combined, which is particularly suitable for extremely high axial load or special requirements for large axial rigidity.
b. Allowable speed
There are great differences due to different types of bearings. In general, bearings with low friction and low heat generation are suitable for high speed. The rolling bearing shall be designed to work under the condition of lower than its limit speed.
When the bearing bears the load, the contact between the bearing ring and the rolling element will produce elastic deformation. The deformation is proportional to the load, and its ratio determines the rigidity of the bearing. Generally, the rigidity of the bearing can be improved through the preloading of the bearing; In addition, in the bearing support design, considering the combination and arrangement of bearings can also improve the support stiffness of bearings.
d. Centering performance and installation error
After the bearing is installed in the working position, it is often poorly installed and positioned due to manufacturing errors. At this time, the bearing often bears excessive load and causes early damage due to shaft bailing and thermal expansion. The self-aligning bearing can overcome the defects caused by installation errors by itself, so it is suitable for this purpose.
e. Installation and removal
Tapered roller bearing, needle roller bearing, etc. belong to the type of bearing with separable inner and outer rings (i.e. the so-called separated bearing), which is convenient for installation and disassembly.
Even the bearings listed in the product catalogue may not be sold on the market; On the contrary, some bearings not listed in the product catalogue are mass-produced. Therefore, it should be clear whether the bearings used are easily available.
Because the thin-walled outer ring may not be round in the processing process, the dimensional accuracy of stamping needle roller bearing cannot be checked before installation. The required geometric accuracy of the bearing can be achieved only when it is pressed into the bearing seat hole with the recommended tolerance limit.
The inspection method for diameter deviation of inscribed circle of needle roller bearing is as follows:
- (1) Press the bearing into the ring gauge (wall thickness ≥ 20mm).
- (2) Check the diameter of the inscribed circle of the bearing with a cylindrical go gauge and a no go gauge.
Load and life
The total number of revolutions before contact fatigue wear of any element in a rolling bearing or the total working hours at a certain speed is called bearing life. The life of rolling bearings varies greatly. The life of bearings produced in the same batch can vary several times or even dozens of times under the same conditions. When 90% of the total revolutions (or working hours) of the same batch of bearings can reach or exceed before fatigue spalling, it is called the rated life L.
The load that can be borne when the rated service life is 1 million revolutions is the rated dynamic load C. When the sum of the plastic deformation at the contact between the rolling element with the largest load and the raceway reaches one ten thousandth of the diameter of the rolling element, the load it can bear is the rated static load C0. The greater the rated load, the stronger the load capacity of the bearing. The rated load of radial bearing is pure radial load, and the rated load of thrust bearing is pure axial load. The actual load of the bearing is often different from the rated load and must be converted into equivalent load.
Under the action of equivalent dynamic load P, the life of bearing is the same as that under actual load. Under the equivalent static load P0, the total plastic deformation at the contact between the rolling element and the raceway with the maximum load is the same as that under the actual load. The relationship between the rated life, rated dynamic load and equivalent dynamic load of the bearing is as follows:
In the formula ε Life index: ball bearing ε=3. Roller bearing ε= 10/3. When selecting bearings, the expected life of bearings is usually taken as the period of medium repair or overhaul of the machine. For example, the infrequently used equipment is 500-2000 hours; Working 8 hours a day, the continuous use of the machine is 20000-30000 hours; Machines that are used continuously for 24 hours a day are 40000-100000 hours. In fact, only a few bearings are damaged when the expected life is reached.
Code of rolling bearing
The code of rolling bearing is a product symbol that uses letters and numbers to represent the characteristics of bearing structure, dimension, tolerance grade, technical performance and so on. The national standard GB/t272-93 stipulates that the code of bearing consists of three parts: front code, basic code and rear code. The basic code is the basis of bearing code. The front code and the rear code are the supplement of the bearing code. They can only be used when there are special requirements for the bearing structure, shape, material, tolerance grade, technical requirements, etc. generally, they can be omitted in part or in whole.
a. Basic code
The basic code indicates the basic type, structure and size of the bearing. It consists of bearing type code, size series code and inner diameter code.
- A1. The bearing type code indicates different types of bearings with numbers or letters. See the database for details.
- A2. The size series code consists of two digits. The first digit represents the width series (radial bearing) or height series (thrust bearing), and the last digit represents the diameter series. The dimension series indicates that bearings with the same inner diameter can have different outer diameters, and the same outer diameter has different widths (or heights), so as to meet the bearing capacity of various requirements.
- A3. The inner diameter code indicates the nominal inner diameter of the bearing, which is represented by numbers.
Example: bearing 2 32 24
2 – type code, self-aligning roller bearing; 32 – size series code; 24 – inner diameter code, d = 120mm;
Example: bearing 6208-2z/P6
6 – type code, deep groove ball bearing; 2 – size series code; 08 – inner diameter code, d = 40mm;
2Z – dust covers are provided at both ends of the bearing; P6 – the tolerance grade shall comply with grade 6 specified in the standard.
50: Separable inner ring or outer ring of separable bearing.
R: Bearings without separable inner or outer rings (needle roller bearings are only applicable to Na type).
K: Roller and cage assembly.
Ws: thrust cylindrical roller bearing shaft ring.
GS: thrust cylindrical roller bearing race.
Daily maintenance of rolling bearing
1. Are there any requirements for the installation surface and installation site?
yes. If there are iron filings, burrs, dust and other foreign matters in the bearing, the bearing will produce noise and vibration during operation, and even damage the raceway and rolling element. Therefore, before installing the bearing, you must ensure that the installation surface and installation environment are clean.
2. Must the bearing be cleaned before installation?
The bearing surface is coated with antirust oil. You must carefully clean it with clean gasoline or kerosene, and then apply clean, high-quality or high-speed and high-temperature lubricating grease before installation and use. Cleanliness has a great impact on bearing life and vibration noise. However, we would like to remind you that the fully enclosed bearing does not need cleaning and refueling.
3. How to select grease?
Lubrication has a very important impact on the operation and service life of bearings. Here we briefly introduce the general principles of selecting lubricating grease. Lubricating grease is made of base oil, thickener and additives. The performance of different types and different brands of lubricating grease of the same type varies greatly, and the allowable rotation limit is different. Pay attention to it when selecting. The performance of grease is mainly determined by the base oil. Generally, the base oil with low viscosity is suitable for low temperature and high speed, and the base oil with high viscosity is suitable for high temperature and high load. The water resistance of thickener determines the water resistance of grease. In principle, greases of different brands cannot be mixed, and even greases with the same thickener will have bad effects on each other due to different additives.
4. When lubricating bearings, the more grease, the better?
When lubricating bearings, the more grease the better, which is a common misconception. Excessive grease in the bearing and bearing chamber will cause excessive mixing of grease, resulting in extremely high temperature. The amount of lubricant filled in the bearing should be 1/2-1/3 of the internal space of the bearing, and should be reduced to 1/3 at high speed.
5. How to install and remove?
During installation, do not directly hammer the bearing end face and non stressed surface. Use pressure block, sleeve or other installation tools (Tooling) to make the bearing bear uniform force. Do not drive the installation through the rolling element. If the mounting surface is coated with lubricating oil, the installation will be smoother. If the fit interference is large, the bearing shall be installed as soon as possible after being heated to 80 – 90 ℃ in mineral oil, and the oil temperature shall be strictly controlled not to exceed 100 ℃ to prevent tempering effect, hardness reduction and size recovery. In case of difficulty in disassembly, it is recommended that you carefully pour hot oil on the inner ring while pulling outward with the disassembly tool. The heat will expand the bearing inner ring and make it easier to fall off.
6. Is the smaller the radial clearance of the bearing, the better?
Not all bearings require minimum working clearance. You must select the appropriate clearance according to the conditions. In national standard 4604-93, the radial clearance of rolling bearing is divided into five groups – group 2, group 0, group 3, group 4 and group 5. The clearance value increases from small to large, of which group 0 is the standard clearance. The basic radial clearance group is suitable for general operating conditions, conventional temperature and common interference fit; Large radial clearance should be selected for bearings working under special conditions such as high temperature, high speed, low noise and low friction; Small radial clearance should be selected for precision spindle and bearing for machine tool spindle; For roller bearings, a small amount of working clearance can be maintained. In addition, there is no clearance for separate bearings; Finally, the working clearance of the bearing after installation is smaller than the original clearance before installation, because the bearing has to bear certain load rotation, as well as the elastic deformation caused by bearing fit and load.
Difference between rolling bearing and sliding bearing
The difference between rolling bearing and sliding bearing lies in the structure. Rolling bearing supports the rotating shaft by the rotation of rolling element, and the contact part is a point. The more rolling elements, the more contact points; The sliding bearing supports the rotating shaft by a smooth surface, so the contact part is a surface. Secondly, the motion mode of rolling bearing is rolling; The motion mode of sliding bearing is sliding, so the friction situation is completely different.
What is a plain bearing
Sliding bearing is a bearing that works under sliding friction. 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. However, the starting friction resistance is large. The part of the shaft supported by the bearing is called the journal, and the parts matching the journal are called the bearing bush.
In order to improve the friction properties of the bearing surface, the antifriction material layer cast on its inner surface is called bearing lining. The materials of bearing bush and bearing liner are collectively referred to as sliding bearing materials. Common sliding bearing materials include bearing alloy (also known as Babbitt alloy or white alloy), wear-resistant cast iron, copper based and aluminum based alloys, powder metallurgy materials, plastics, rubber, hardwood and carbon graphite, polytetrafluoroethylene (PTFE), modified Polyoxymethylene (POM), etc. Sliding bearing applications are generally under low-speed and heavy-duty working conditions, or operating parts where maintenance and lubricating oil filling are difficult.
The radial bearing (mainly bearing radial force) in rolling bearing is usually composed of inner ring, outer ring, rolling element and rolling element cage. The inner ring is tightly sleeved on the journal and rotates with the shaft, and the outer ring is installed in the bearing seat hole. A raceway is arranged on the outer circumference of the inner ring and the inner circumference of the outer ring. When the inner and outer rings rotate relative to each other, the rolling elements roll on the raceway of the inner and outer rings. They are separated by a cage to avoid mutual friction. The thrust bearing is divided into two parts: tight ring and movable ring. The tightening ring is tight with the shaft sleeve, and the movable ring is supported on the bearing seat. The ring and rolling element are usually made of rolling bearing steel with high strength and good wear resistance. The surface hardness after quenching shall reach HRC60 – 65. The cage is mostly made of mild steel, or copper alloy cloth, bakelite or plastic.
Common faults of rolling bearing
There are generally two kinds of fault phenomena of rolling bearing: one is that the temperature of the bearing installation part is too high, and the other is that there is noise during bearing operation.
1. The bearing temperature is too high
During the operation of the mechanism, the part where the bearing is installed is allowed to have a certain temperature. When touching the mechanism shell by hand, it should be normal not to feel hot. Otherwise, it indicates that the bearing temperature is too high.
The reasons for high bearing temperature 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; The bearing race rotates on the shaft or in the shell; Excessive load; Broken bearing cage or rolling element, etc.
2. Bearing noise
The rolling bearing is allowed to make slight running noise during operation. If the noise is too loud or there is abnormal noise or impact sound, it indicates that the bearing is faulty.
The causes of rolling bearing noise are complex. One is the wear of the mating surfaces of the inner and outer rings of the bearing. Due to this wear, the matching relationship between the bearing and the shell, the bearing and the shaft is damaged, resulting in the axis deviation from the correct position and abnormal noise when the shaft moves at high speed. When the bearing is tired, the metal on its surface will peel off, which will also increase the radial clearance of the bearing and produce abnormal noise. In addition, insufficient bearing lubrication, dry friction and bearing breakage will produce abnormal sound. After the bearing is worn and loose, the cage is loose and damaged, which will also produce abnormal noise.
3. Bearing wear
Rolling bearing wear is a common equipment problem during the use of the shaft, which is mainly caused by the metal characteristics of the shaft: Although the metal has high hardness, it has poor concession (unable to recover after deformation), poor impact resistance and fatigue resistance, so it is easy to cause adhesive wear, abrasive wear, fatigue wear, fretting wear, etc. Most of the shaft wear is not easy to detect. It will be noticed only when the machine is at high temperature, large jumping range and abnormal noise. However, when people find out, most of the rolling shafts have been worn, resulting in machine shutdown.
Correct use of rolling bearing
1. Disassembly and assembly of bearing
The bearing shall be cleaned before installation. During installation, the auxiliary bearing shall be pressed straight and evenly with special tools. Do not knock with a hand hammer. In particular, it is forbidden to knock directly on the bearing. When the fit between the bearing race and the seat hole is loose, the seat hole shall be repaired or the bearing shall be replaced. Do not reluctantly use the method of pitting or padding copper skin on the bearing mating surface. When disassembling the bearing, use a suitable puller to pull out the bearing, and do not knock the bearing with a chisel, hammer, etc.
2. Bearing lubrication
There are two kinds of lubricants commonly used in rolling bearings: lubricating oil and grease. When the circumferential speed of the shaft is less than 4-5m/s, or the parts on the vehicle that cannot be lubricated with lubricating oil, grease shall be used for lubrication. The advantage of grease lubrication is that the sealing structure is simple, the grease is not easy to lose, and it is not affected by temperature. Adding grease once can be used for a long time.
Two problems should be paid attention to when using grease. One is to select the appropriate brand of grease according to the requirements of the automobile manual. For example, nano base grease should not be selected for automobile water pump bearing because of its poor water resistance. Second, the amount of lubricating grease added to the bearing should be appropriate. Generally, it is appropriate to fill only 1/2-L/3 of the bearing cavity. Too much is not only useless, but also increases the running resistance of the bearing and heats it up. Special attention should be paid to the automobile hub bearing. It is necessary to advocate “empty hub lubrication”, that is, only apply an appropriate layer of grease on the bearing. Otherwise, it will not only waste and poor heat dissipation, but also cause the grease to overflow due to heating, which may affect the braking performance.
The advantages of lubricating oil lubrication are low friction resistance and heat dissipation. It is mainly used for bearings with high speed and high working environment temperature. The brand of lubricating oil shall be selected according to the requirements of the vehicle manual, and shall be replaced in time after the vehicle maintenance cycle. After discharging the old oil, the mechanism shall be cleaned before adding new oil. The oil shall be added to the specified marking line or flush with the oil filler (depending on the specific structure and requirements of the vehicle), and no more oil shall be added.
Common fault solutions
Traditional maintenance methods
Repair welding, ball replacement, pitting and other methods are generally used for rolling shaft wear in China. However, when the shaft is made of No. 45 steel (quenching and tempering treatment), if only surfacing treatment is adopted, the welding internal stress will be generated. Under heavy load or high-speed operation, cracks and even fractures may appear at the shaft shoulder. If stress relief annealing is adopted, it is difficult to operate, And the processing cycle is long and the maintenance cost is high; When the material of the shaft is HT200, cast iron welding is not ideal. Some enterprises with high maintenance technology will adopt brush plating, laser welding, micro arc welding and even cold welding. These maintenance technologies often require high requirements and high costs.
Calculation method of fault frequency:
- Failure frequency of outer ring of rolling bearing: bpvor ≌ 0.4nn;
- Failure frequency of inner ring of rolling bearing: bpfir ≌ 0.6nn;
- Failure frequency of rolling bearing cage: ftfr ≌ 0.4N;
- Fault frequency of bearing outer ring: bpfoe ≌ n (0.5n-1.2);
- Fault frequency of bearing inner ring: bpfie ≌ n (0.5N + 1.2);
- Fault frequency of bearing rolling element: BSFE ≌ n (0.2n-1.2/N);
- Fault frequency of bearing cage: FTFE ≌ n (0.5-1.2/N).
The above symbols: n = number of scrolls. N = shaft speed.
Note: 1. The rolling bearing does not slide; 2. The geometric dimension of rolling bearing has not changed; 3. The outer ring of the bearing is fixed and does not rotate.
Latest maintenance methods
The above repair technologies are not common in European, American, Japanese and Korean enterprises. Developed countries generally use polymer composite technology and nanotechnology. Polymer technology can be operated on site, effectively improving the maintenance efficiency and reducing the maintenance cost and intensity. Among them, the most widely used is Meijia huafushi blue technology system. Compared with traditional technology, polymer composites not only have the strength and hardness required by metal, but also have the concession (variable relationship) that metal does not have, which can ensure the size matching of repair parts and mating parts to the greatest extent; At the same time, using the comprehensive advantages of compression resistance, bending resistance and ductility of the composite material itself, it can effectively absorb the impact of external forces, greatly resolve and offset the radial impact force of the bearing on the shaft, avoid the possibility of clearance, and avoid the secondary wear of the equipment caused by the increase of clearance.
Position and function of rolling bearing
Rolling bearing is an important mechanical basic component widely used in various fields of national economy and national defense.
The invention of rolling bearing has a long history. According to the discovery of archaeological relics in Yongji County, Shanxi Province, China, bronze rolling bearings have been made as early as 221 – 207 BC (Qin Dynasty); According to the discovery of archaeological relics in Nimi lake, Italy, bronze rolling bearings were also found from 12 to 41 A.D. The birth of modern bearing industry is marked by the invention of the world’s first ball grinding machine in Germany in 1883 and the entry into the era of industrialized production of steel balls. With the vigorous development of bicycle, automobile and other industries during the second industrial revolution, rolling bearing has gradually become a highly professional industrial industry all over the world, and plays a very important role in modern industry.
The importance of rolling bearings is mainly reflected in the following aspects:
(1) In the national economy – rolling bearings are known as “industrial joints”. As the basic and backbone industry of machinery industry, the development level of bearing industry often represents or restricts the development level of machinery industry and other related industries in a country. In Japan, the bearing industry is often referred to as the food of industry. The bearing industry is known as “the core industry of machinery industry” and “the basic industry to improve national life”. It is protected and supported by the revitalization policy of the Japanese government and is one of the 14 “specific machinery industries” “One of the industries. In China, rolling bearing is one of the 11 categories of special revitalization Machinery Products determined by the state, and 33 bearing enterprises are listed as special revitalization industries. Among the 520 key enterprises newly determined by the state, the bearing industry accounts for 6. In the current catalogue of industries, products and technologies encouraged by the state to develop” , the manufacturing of car bearings, railway rolling stock, precision bearings and high-speed bearings are included.
(2) In the cause of national defense – rolling bearings are essential armaments.
Bearings are important or core parts in many military equipment; in war, bearing manufacturers are one of the key targets of hostile countries; during the cold war, special bearing equipment was one of the embargoed materials for western countries to implement economic blockade against socialist countries. So far, many bearing products and technologies are still included in the scope of technical blockade by many military powers .
(3) In terms of technical status – bearing steel is the steel with the most stringent technical indicators among various alloy steels. It is generally recognized that the smelting level of bearing steel is the symbol of a country’s metallurgical technology level. In China, among many special steels such as stainless steel, high-speed steel, gear steel, valve steel and spring steel, bearing steel is one of the few steel types that need to issue production licenses so far Rolling bearing is also an important application field of many new materials, such as engineering ceramics and engineering plastics.
Rolling bearing industry is one of the earliest industrial fields to carry out standardization activities and adopt reliability technology. As early as 1949, the classical theory of rolling bearing fatigue life and reliability has been established, and it was incorporated into the international standard ISO281:1963 in 1963.
The development of the bearing industry in China
With the implementation of China’s reform and opening up policy, a large number of foreign bearing products in advanced technology fields have entered China one after another. Due to the political influence in the early days of the founding of New China, the spread of foreign civilian bearing technology and product sales have also been affected for a time. Blocked, but after all, because of China’s huge consumer market and the rise of national industries, most of the well-known foreign bearing brands have set up subsidiaries and even production plants in China. Although the domestic bearing industry has made significant progress and improvement, there is still a big gap in the promotion of technical quality and product after-sales maintenance concept. Generally speaking, the commercial output value is inherently weak compared to foreign bearings. High-end bearing domestic industry The reputation of the industry needs to be expanded and developed.
Due to the special period of China’s domestic development, the sale and purchase of bearing products under the market economy system is particularly chaotic. There are a large number of large and small distributors engaged in various imported and domestic bearings in China. Due to the large market demand, all walks of life Bearings are inseparable, and it has become China’s unique domestic bearing products “matching seats” phenomenon. According to the needs of different enterprises (except the military), in China, from imported high-quality bearing products to general domestic bearings, the market Prices have extremely large differences and jitter changes.
Related national standards
- GB/T 28268-2012: Technical requirements for stamped cages of rolling bearings
- GB/T 27556-2011: Rolling bearing radial bearing locating groove size and tolerance
- GB/T 273.1-2011: Rolling bearing overall dimension plan Part 1: Tapered roller bearing
- GB/T 20060-2011: Rolling bearing cylindrical roller bearing separable oblique retaining ring outline dimensions
- GB/T 27558-2011: Classification of rolling bearings for linear motion rolling bearings
- GB/T 27557-2011: Rolling bearing code method for rolling bearing linear motion
- GB/T 27560-2011: Technical requirements for casting seat of outer spherical ball bearing for rolling bearing
- GB/T 27554-2011: Code method for rolling bearing outer spherical ball bearing with seat
- GB/T 27555-2011: Technical conditions of rolling bearing with seat outer spherical ball bearing
- GB/T 27559-2011: Cylindrical roller bearings for rolling bearing machine tool spindles
- GB/T 6391-2010: Dynamic load rating and rating life of rolling bearings
- GB/T 25766-2010: Radial clearance of rolling bearing outer spherical ball bearing
- GB/T 25765-2010: Rolling bearing ball bearings for automobile gearboxes
- GB/T 25764-2010: Rolling bearings, roller bearings for automobile gearboxes
- GB/T 25767-2010: Rolling Bearing Tapered Roller
- GB/T 25769-2010: Measuring method of radial clearance of rolling bearing
- GB/T 25760-2010: Overall dimensions of rolling bearing needle roller and thrust ball combined bearings
- GB/T 25768-2010: Rolling bearing needle roller and bidirectional thrust cylindrical roller combined bearing
- GB/T 25761-2010: Overall dimensions of rolling bearing needle roller and angular contact ball combined bearings
- GB/T 25772-2010: Rolling bearing railway passenger car bearings
- GB/T 25771-2010: Rolling bearing railway locomotive bearings
- GB/T 25770-2010: Rolling bearing railway freight car bearings
- GB/T 308.2-2010: Rolling bearing balls Part 2: Ceramic balls
- GB/T 25763-2010: Rolling bearing needle roller bearings for automobile gearboxes
- GB/T 25762-2010: Needle roller and cage assemblies for rolling bearing motorcycle connecting rod support
- GB/T 25510-2010 Mechanical System and General Parts Rolling Bearing Reference Dictionary
- GB/T 7810-1995: Outer dimensions of rolling bearing with seat outer spherical ball bearing
- GB/T 7809-1995: Outer dimensions of rolling bearing outer spherical ball bearing seat
- GB/T 24610.4-2009: Rolling bearing vibration measurement method Part 4: Cylindrical roller bearing with cylindrical bore and cylindrical outer surface
- GB/T 24611-2009: Terms, characteristics and causes of damage and failure of rolling bearings
- GB/T 24610.3-2009: Rolling bearing vibration measurement method Part 3: Spherical roller bearing and tapered roller bearing with cylindrical bore and cylindrical outer surface
- GB/T 24610.2-2009: Rolling bearing vibration measurement method Part 2: Radial ball bearing with cylindrical bore and cylindrical outer surface
- GB/T 24610.1-2009: Rolling Bearing Vibration Measurement Method Part 1: Basics
- GB/T 24609-2009: Calculation method and coefficient of rated thermal speed of rolling bearing
- GB/T 24608-2009: Inspection Rules for Rolling Bearings and Commercial Parts
- GB/T 24607-2009: Rolling bearing life and reliability test and evaluation
- GB/T 24606-2009: Non-destructive testing of rolling bearings, magnetic particle testing
- GB/T 24605-2009: Rolling bearing product mark
- GB/T 24604-2009: Thrust angular contact ball bearings for rolling bearing machine tool screws
- GB/T 12764-2009: Rolling bearings without inner ring, drawn outer ring needle roller bearings, dimensions and tolerances
- GB/T 7218-1995: External dimensions of miniature radial ball bearings with flanged outer ring of rolling bearings
- GB/T 21559.2-2008: Rolling Bearings for Linear Motion Rolling Bearings Part 2: Static Load Rating
- GB/T 271-2008: Classification of rolling bearings
- GB/T 299-2008: External dimensions of rolling bearing double-row tapered roller bearings
- GB/T 21559.1-2008: Rolling Bearing Linear Motion Rolling Bearing Part 1: Rated Dynamic Load and Rated Life
- GB/T 7813-2008: Dimensions of split vertical bearing housings for rolling bearings
- GB/T 300-2008: Outer dimensions of rolling bearing four-row tapered roller bearings
- GB/T 5859-2008: Rolling bearing thrust spherical roller bearing outline dimensions
- GB/T 292-2007: Rolling bearing angular contact ball bearing outline dimensions
- GB/T 283-2007: Rolling bearing cylindrical roller bearing outline dimensions
- GB/T 6445-2007: Dimensions and tolerances of roller needle roller bearings for rolling bearings
- GB/T 7811-2007: Rolling bearing parameter symbol
- GB/T 9160.1-2006: Rolling Bearing Accessories Part 1: Conical Bushing
- GB/T 4663-1994: External dimensions of rolling bearing thrust cylindrical roller bearings
- GB/T 5801-2006: Rolling bearing 48, 49 and 69 size series needle roller bearing outline dimensions and tolerances
- GB/T 20056-2006: Rolling bearing radial needle roller and cage assembly dimensions and tolerances
- GB/T 20058-2006: Rolling bearing single row angular contact ball bearing outer ring non-thrust end chamfer size
- GB/T 273.2-2006: Rolling bearing thrust bearing overall plan
- GB/T 4604-2006: Radial clearance of rolling bearings
- GB/T 9160.2-2006: Rolling Bearing Accessories Part 2: Locking Nuts and Locking Devices
- GB/T 20057-2006: Rolling bearing single row cylindrical roller bearing flat retaining ring and ring without retaining edge chamfer size
- GB/T 3882-1995: Outer dimensions of rolling bearing outer spherical ball bearings and eccentric sleeves
- GB/T 307.3-2005: General technical rules for rolling bearings
- GB/T 307.2-2005: Principles and methods of rolling bearing measurement and inspection
- GB/T 307.1-2005: Rolling bearing radial bearing tolerance
- GB/T 301-1995: External dimensions of rolling bearing thrust ball bearings
- GB/T 297-1994: Rolling bearing tapered roller bearing outline dimensions
- GB/T 296-1994: Overall dimensions of rolling bearing double row angular contact ball bearings
- GB/T 294-1994: Dimensions of rolling bearing three-point and four-point contact ball bearings
- GB/T 288-1994: Rolling bearing spherical roller bearing outline dimensions
- GB/T 285-1994: Rolling bearing double row cylindrical roller bearing outline dimensions
- GB/T 281-1994: Rolling bearing self-aligning ball bearing outline dimensions
- GB/T 276-1994: Overall dimensions of rolling bearing deep groove ball bearings
- GB/T 275-1993: Coordination of rolling bearing with shaft and housing
- GB/T 272-1993: Rolling bearing code method
- GB/T 16643-1996: Overall dimensions of rolling bearing needle roller and thrust cylindrical roller combined bearings
- GB/T 4605-2003: Rolling bearing thrust needle roller and cage assembly and thrust washer
- GB/T 5800-2003: Precision bearings for rolling bearing instruments
- GB/T 4199-2003: Definition of rolling bearing tolerances
- GB/T 4662-2003: Static load rating of rolling bearings
- GB/T 8597-2003: Anti-rust packaging for rolling bearings
- GB/T 5868-2003: Rolling bearing installation dimensions
- GB/T 308-2002: Rolling bearing steel balls
- GB/T 307.4-2002: Rolling bearing thrust bearing tolerance
- GB/T 4661-2002: Rolling Bearing Cylindrical Roller
- GB/T 6930-2002: Rolling Bearing Vocabulary
- GB/T 7217-2002: Rolling bearing flange outer ring radial ball bearing flange size
- GB/T 309-2000: Rolling bearing needle roller
- GB/T 274-2000: Maximum chamfer size of rolling bearing
- GB/T 273.3-1999: Rolling bearing radial bearing overall plan
- GB/T 305-1998: Dimensions and tolerances of stop grooves and stop rings on the outer ring of rolling bearings
- GB/T 290-1998: Outer dimensions of drawn cup needle roller bearings for rolling bearings
- GB/T 4459.7-1998 Mechanical Drawing Rolling Bearing Representation
Assembly method of rolling bearing
Before the assembly of rolling bearing, it is necessary to clean the rolling bearing to keep it clean and tidy; Then check the rolling bearing and assemble it according to its assembly requirements.
- 1. Remove the residual lubricating grease and antirust oil in the rolling bearing.
- 2. Wash the rolling bearing with kerosene, then wash it with gasoline and dry it with a clean cloth.
- 3. It can also be cleaned with other cleaning agents, and the bearing shall be wiped clean with a cloth.
- 4. Remember, do not clean or dry the bearing with dirty oil or dirty cloth or cotton yarn.
Assembly principle of rolling bearing: according to the bearing structure, size, working conditions and the matching nature of bearing components, the pressure during assembly shall be directly added to the end face of the ferrule to be matched, and it is not allowed to transmit pressure through the rolling element. The assembly of rolling bearing generally includes press in assembly method, temperature difference assembly method and power frequency induction heater.
1. The rolling bearing shall not be removed from the machine. If it must be removed, the correct tools and methods shall be selected.
2. Before assembling the rolling bearing, appropriate cleaning agent and method shall be selected for cleaning according to the antirust mode of the rolling bearing.
3. Before assembly, the inner diameter and outer diameter micrometers shall be used to check the inner diameter of the bearing sleeve and the diameter of the journal, and the matching tolerance must meet the requirements of the drawing.
4. The rolling bearing is installed in the split bearing seat, and there shall be no gap between the joint surface of the bearing cover and the bearing seat, but a certain gap shall be reserved between the bearing outer ring and the pad mouth on both sides of the bearing seat. The side clearance of the pad mouth can be measured and checked with a feeler gauge. If the clearance is too small or there is “clamping”, it can be scraped with a scraper to increase the clearance and comply with the table clearance between rolling bearing and split bearing seat.
5. Rolling bearing assembly includes driving method, pressing method and hot assembly method. When hammering by driving method, red copper rod or sleeve shall be used as a tool to transfer force to make the force acting on the bearing symmetrical. In the press in method, a press is used instead of hammering, and the casing is still used to transfer force. During hot charging, direct heating with flame is strictly prohibited. It shall be heated with 80 – 90 ℃ hot oil, and the oil temperature shall not exceed 100 ℃. The bearing shall not contact with the heating oil tank seat during heating, and the bearing shall be hung in the middle of the oil layer to avoid annealing caused by local overheating.
The heating time shall not be less than 15min, and the inner sleeve shall be assembled after expanding to the required value. There shall be no pause during hot assembly, and the bearing shall be installed to the correct position quickly at one time. If the steel ball cage in the bearing is oil resistant plastic, it should be heated with water, but the water should be wiped dry in time after assembly.
6. When assembling rolling bearings, the following requirements shall be met:
- (1) the cleaned bearing shall be inspected, and the bearing shall be free of damage, corrosion, flexible rotation and abnormal noise. The matching category and size of the bearing, journal and bearing seat shall be checked, and assembly can be carried out only after meeting the requirements;
- (2) during assembly, the pressure applied to the bearing shall be evenly distributed and perpendicular to the end face, and the stress on one side is prohibited. Select the stress point according to the assembly relationship. If the bearing is assembled on the journal, the pressure should be added to the inner ring of the bearing;
- (3) during assembly, the bearing and shaft shoulder shall be close. The clearance between tapered roller bearing and radial thrust bearing and shaft shoulder shall not be greater than 0.05mm, and that of other bearings shall not be greater than 0.1mm. The bearing cover and retaining ring must be flat and evenly close to the bearing end face, and the clearance shall be adjusted according to the provisions of the technical documents;
- (4) during assembly, the end marked with specifications on the bearing shall be outward as far as possible to facilitate inspection and replacement. After assembly, rotate by hand to check whether there is jamming, and then add an appropriate amount of grease. The sealing device must be assembled as required, and there shall be no oil leakage after sealing;
- (5) the axial clearance of single row, double row and four row tapered roller bearings and radial thrust bearings shall be checked during assembly and adjusted according to the bearing standards or technical documents;
- (6) various centripetal bearings, needle roller bearings and spiral roller bearings must rotate flexibly after assembly. After the bearing with grease is assembled, clean grease of 65% – 80% of the cavity volume shall be injected into the bearing cavity. For the bearing lubricated with thin oil, it is not allowed to inject grease.
- (7) when assembling the bearing, the axial clearance and axial preload (axial pre interference) to be adjusted shall comply with the provisions of the bearing standard or equipment technical documents.
Source: China Bearing Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
If you want to have more information about the article or you want to share your opinion with us, contact us at email@example.com