China piping solution supplier: www.epowermetals.com | Email: sales@epowermetals.comTel: +8618267732328

Bearing types: guidelines for selecting the correct bearing

What is a bearing?

20230211085848 50227 - Bearing types: guidelines for selecting the correct bearing

Bearing is an important part of modern mechanical equipmentIts main function is to support the mechanical rotating body, reduce the friction coefficient during its movement, and ensure its rotation accuracy.

According to the different friction properties of moving elements, bearings can be divided into rolling bearings and sliding bearings. Rolling bearings have been standardized and serialized, but compared with sliding bearings, their radial dimensions, vibration and noise are larger and their prices are higher.
Rolling bearings are generally composed of four parts: outer ring, inner ring, rolling element and cage. Strictly speaking, they are composed of six parts: outer ring, inner ring, rolling element, cage, seal and lubricating oil. In brief, as long as they have outer ring, inner ring and rolling element, they can be defined as rolling bearings. According to the shape of rolling element, rolling bearings are divided into ball bearings and roller bearings.

Application of bearings

In terms of its function, it should be a support, that is, it is literally used to support the shaft, but it is only a part of its function. The essence of support is to be able to bear the radial load. It can also be understood that it is used to fix the shaft. The quick, easy and automatic selection of bearings has been included. It is to fix the shaft so that it can only realize rotation, while controlling its axial and radial movement. There is no bearing for the motorIt can’t work because the shaft may move in any direction, and the motor requires the shaft to rotate only when it works. Theoretically, it is impossible to realize the role of transmission. Not only that, the bearing will also affect transmission. In order to reduce this effect, good lubrication must be achieved on the bearing of high-speed shaft. Some bearings have lubrication themselves, which is called pre lubrication bearingThe bearing must have lubricating oil, which is responsible for high speed operation. Friction will not only increase energy consumption, but also easily damage the bearing. It is one-sided to say that sliding friction is converted into rolling friction, because there is something called sliding bearing.
At present, the bearing industry in China mainly faces three prominent problems: low concentration of production, low R&D and innovation ability, and low level of manufacturing technology.

  • First, the industry’s production concentration is low. Of the world’s bearing sales of about 30 billion dollars, the world’s eight largest multinational companies account for 75% – 80%. Germany’s two largest companies account for 90% of the country’s total, Japan’s five companies account for 90% of the country’s total, and the United States one accounts for 56% of the country’s total. While China’s ten largest bearing enterprises, such as bearings, account for only 24.7% of the sales of the industry, and the production concentration of the top 30It is only 37.4%.
  • Second, low R&D and innovation capabilities. Weak basic theoretical research across the industry, weak participation in international standard formulation, less original technology, less patented products. At present, our design and manufacturing technology is basically imitation, and our product development ability is low, which is reflected in: although the matching rate of domestic main engines has reached 80%, the matching and maintenance bearings of important main engines, such as high-speed railway passenger cars, medium and high-end cars, computers, air conditioners, high level rolling mills, are basically imported.
  • Third, the level of manufacturing technology is low. China’s bearing industry has a slow development of manufacturing technology and technological equipment, low CNC lathing rate, and low level of grinding automation. There are only more than 200 automatic production lines in the country. Advanced heat treatment processes and equipment that are critical to bearing life and reliability, such as controlled atmosphere protection heating, double refining, bainite quenching and other low coverage, manyNo breakthrough has been made in tackling technical problems. The research and development of new bearing steel grades, the improvement of steel quality, and the research and development of lubrication, cooling, cleaning, abrasives and other related technologies cannot adjust the requirements of bearing product level and quality improvement. As a result, the process capability index is low, the consistency is poor, the product processing size is discrete, and the internal quality of the product is unstable, which affects the bearingAccuracy, performance, life and reliability.

Classification of bearings

1. Sliding bearing

20230211090820 79102 - Bearing types: guidelines for selecting the correct bearing

What is sliding bearing?
Sliding bearingUnder 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, and the oil film also has certain vibration absorption energy. However, the starting friction resistance is large. The part of the shaft supported by the bearing is called the journal, which matches the journalThe parts of bearing bush are called bearing bush. The antifriction data layer cast on the inner surface of bearing bush in order to improve the friction property of bearing bush surface is called bearing bush. The data of bearing bush and bearing bush are collectively called sliding bearing data. The application of sliding bearing is generally under the condition of high speed and light load.
Operating principle of sliding bearing
The bearing is a part supporting the shaft, which is used to guide the rotation of the shaft or bear the rotating parts of the shaft.
Application of sliding bearing
A sliding bearing is a bearing that works under sliding friction. The sliding bearing works stably, reliably and noiselessly. 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,The parts matching the journal are called bearing shells. The antifriction data layer cast on the inner surface of the bearing shell to improve the friction property of the bearing shell surface is called bearing liners. The data of bearing shells and bearing liners are collectively called sliding bearing data. Sliding bearings are generally used in low-speed and heavy load working conditions, or in operating parts where maintenance and lubrication are difficult.
Classification of plain bearings
There are many kinds of sliding bearings:

  • ① According to the direction of bearing load, it can be divided into radial (centripetal) sliding bearing and thrust (axial) sliding bearing.
  • ② According to the type of lubricant, it can be divided into seven categories: oil lubrication bearing, grease lubrication bearing, water lubrication bearing, gas bearing, solid lubrication bearing, magnetic fluid bearing and electromagnetic bearing.
  • ③ According to the thickness of lubricating film, it can be divided into thin film lubrication bearing and thick film lubrication bearing.
  • ④ According to the bearing bush data, it can be divided into bronze bearing, cast iron bearing, plastic bearing, gem bearing, powder metallurgy bearing, self-lubricating bearing and oil bearing.
  • ⑤ According to the structure of bearing bush, it can be divided into round bearing, elliptical bearing, three oil leaf bearing, stepped surface bearing, tilting pad bearing and foil bearing.

Maintenance of sliding bearing
1. The sliding bearing can also be lubricated with grease. The following points should be considered when selecting grease:

  • (1) When the bearing load is large and the speed is low, the grease with small cone penetration should be selected, otherwise, the grease with large cone penetration should be selected. For high-speed bearings, the grease with small cone penetration and good mechanical stability should be selected. Special attention should be paid to the lower viscosity of the base oil of the grease.
  • (2) The drop point of the selected grease is generally 20-30 ℃ higher than the operating temperature. In the case of continuous operation at high temperature, be careful not to exceed the allowable temperature range of the grease.
  • (3) When the sliding bearing works in a water drenched or humid environment, calcium base, aluminum base or lithium base grease with good water resistance shall be selected.
  • (4) Select lubricating grease with good adhesion.

2. Selection of lubricating grease for sliding bearing:

  • Load<1MPa, journal circumferential speed below 1m/s, maximum working temperature 75 ℃, 3 # calcium base grease;
  • Load 1-6.5MPa, journal circumferential speed 0.5-5m/s, maximum working temperature 55 ℃, 2 # calcium base grease;
  • Load>6.5MPa, journal circumferential speed below 0.5m/s, maximum working temperature 75 ℃, select No. 3 calcium base grease;
  • Load<6.5MPa, journal circumferential speed 0.5-5m/s, maximum working temperature 120 ℃, select No. 2 lithium grease;
  • Load>6.5MPa, journal circumferential speed below 0.5m/s, maximum working temperature 110 ℃, select No. 2 calcium sodium base grease;
  • The load is 1-6.5MPa, the journal circumferential speed is below 1m/s, the maximum working temperature is 50-100 ℃, and No. 2 lithium grease is selected;
  • Load>5MPa, journal circumferential speed 0.5m/s, maximum working temperature 60 ℃, 2 # calender grease;
  • In a humid environment, when the temperature is 75-120 ℃, calcium sodium grease grease should be considered. In a humid environment, when the operating temperature is below 75 ℃, aluminum grease can also be used without No. 3 calcium grease. When the operating temperature is 110-120 ℃, lithium grease or barium grease can be used. When centralized lubrication, the consistency should be smaller.

3. Lubrication cycle of grease for sliding bearing:

  • Occasionally working, unimportant parts: shaft speed<200r/min, lubrication cycle once every 5 days; shaft speed>200r/min, lubrication cycle once every 3 days.
  • Intermittent operation: shaft speed<200r/min, lubrication cycle once every 2 days; shaft speed>200r/min, lubrication cycle once every 1 day.
  • Continuous operation, operating temperature less than 40 ℃: shaft speed<200r/min, lubrication cycle once a day; shaft speed>200r/min, lubrication cycle once a shift.
  • Continuous operation, operating temperature 40-100 ℃: shaft speed<200r/min, lubrication cycle once per shift; shaft speed>200r/min, lubrication cycle twice per shift.

Matters needing attention
The sliding bearing is in surface contact, so a certain oil film should be kept between the contact surfaces, so the following issues should be paid attention to during design:

  • 1. The oil film shall enter the friction surface smoothly.
  • 2. Oil shall enter the bearing from the non load bearing surface area.
  • 3. Do not leave the full ring oil groove in the middle of the bearing.
  • 4. For example, oil grooves shall be opened at joints.
  • 5. The oil ring shall be fully and reliably fed.
  • 6. Do not block the filler hole.
  • 7. Do not form an oil stop zone.
  • 8. Avoid sharp edges and corners that cut off the oil film.

Troubleshooting of sliding bearing
1、 The glued bearing is overheated, overloaded, improperly operated or the temperature control system fails

  • 1. If the bearing is found to be overheated during movement, it should be stopped immediately for inspection. It is better to keep the rotor running at a low speed, or continue to supply oil for a period of time until the bearing bush cools down. Otherwise, babbitt on the bearing bush will stick to the journal due to bonding, which will be troublesome to repair.
  • 2. Prevent insufficient lubricating oil or impurities in the oil, as well as misalignment of rotor installation.
  • 3. The bearing bush with slight scuffing damage can be eliminated by scraping and grinding repair method and continue to be used.

2、 Fatigue fracture Babbitt alloy fatigue fracture of bearing is caused by vibration caused by imbalance, shaft deflection and edge load, overload, etc. The quality of bearing maintenance and installation is not high.

  • 1. Improve installation quality and reduce bearing vibration.
  • 2. Avoid eccentric load and overload.
  • 3. Suitable babbitt alloy and new bearing structure shall be adopted.
  • 4. Strictly control the bearing temperature rise.

3、 Because the lubricating oil brings large particles of dirt into the bearing clearance and embeds them on the bearing bushing, so that when the bearing contacts with the journal (or thrust plate), hard scabs will form, which will seriously scratch the surface of the shaft during operation. The roughened bearing should pay attention to the cleanness of the oil circuit, especially in the maintenance, the metal chips or dirt should be cleaned.
4、 The wear and scratch are caused by impurities, foreign matters and dirt mixed in the lubricating oil, improper maintenance methods, incorrect installation, improper use and maintenance, and poor quality control.

  • 1. Clean the journal, oil circuit and oil screening procedure, and replace the clean lubricating oil that meets the quality requirements.
  • 2. Equipped with repaired or new bearing shells.
  • 3. If the installation is found to be misaligned, it shall be aligned in time.
  • 4. Pay attention to the maintenance quality.

5、 Cavitation corrosion Due to the unreasonable structure of the bearing (the oil stain on the bearing is unreasonable), the vibration of the shaft, the formation of steam bubbles in the oil film, the steam bubbles break, and the local surface of the bearing bush generates vacuum, causing small pieces to peel off and cause cavitation damage.

  • 1. Increase the supply pressure.
  • 2. Improve the shape of bearing bush oil groove and oil groove, and modify the edge or shape of groove to improve the shape of oil film streamline.
  • 3. Reduce the bearing clearance and reduce the shaking of the shaft center.
  • 4. Replace with suitable bearing bush data.

6、 Due to poor insulation or grounding, or static electricity, electric erosion will form a certain voltage between the journal and the bearing pad, penetrate the oil film between the journal and the bearing pad, and generate electric sparks, which will make the bearing pad into pits.

  • 1. Check the insulation of the machine, especially pay attention to whether the wires of some protective devices (such as thermal resistance, thermocouple, etc.) are well insulated.
  • 2. Check the grounding of the machine.
  • 3. If the damage is not serious after electric erosion, the bearing bush can be scraped.
  • 4. Check the journal. If there is pitting on the journal, polish the journal to remove the pitting.

2. Rolling bearing

20230211091902 41699 - Bearing types: guidelines for selecting the correct bearing

What is rolling bearing?
Rolling bearingIt is a precise mechanical element that changes the sliding friction between the running shaft and the shaft seat into rolling friction to reduce friction loss. Rolling bearing is generally composed of four parts: inner ring, outer ring, rolling element and cage. The role of the inner ring is to match with the shaft and rotate with the shaft; the role of the outer ring is to match with the bearing seat and play a supporting role; the role of the rolling element is to use the cageThe rolling element is evenly distributed between the inner ring and the outer ring, and its shape, size and quantity directly affect the service performance and life of the rolling bearing; the cage can make the rolling element evenly distributed and guide the rolling element to rotate for lubrication.
Working principle of rolling bearing
The rolling bearing is composed of an outer ring, an inner ring, a rolling element and a cage. The inner ring is matched with the shaft, the outer ring is matched with the housing hole, and the inner and outer rings form rolling friction rotation through the rolling element. The cage is designed to keep the rolling element evenly distributed in the circumference.
Application of Rolling Bearings
The most representative rolling bearing is widely used and can withstand radial load and bidirectional axial load.
It is suitable for high speed rotation and occasions requiring low noise and low vibration. The sealed bearing with steel dust cover or rubber seal ring is pre filled with proper amount of grease. The bearing with stop ring or flange on the outer ring is easy for axial positioning and installation in the housing.
The size of the maximum load type bearing is the same as that of the standard bearing, but there is a filling groove on the inner and outer rings, which increases the number of balls to increase the rated load.
Classification of rolling bearings
According to the structure of rolling element and ring, 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, spherical ball bearing with seat, etc.
Bearing according to its outer diameter:

  • (1) Miniature bearings – bearings with nominal outside 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 a nominal outside diameter of 60-115mm.
  • (4) Medium and large bearings – bearings with a nominal outside diameter of 120-190mm.
  • (5) Large bearings – bearings with a nominal outside diameter of 200-430mm.
  • (6) Oversize bearings – bearings with nominal outside diameter ranging from 440-2000mm.
  • (7) Heavy bearings – bearings with a nominal outside diameter of more than 2000mm.

Selection Guide for Rolling Bearings
There are many types of rolling bearings, and the following factors can be considered for selection.
a. Size, direction and nature of load
Ball bearings are suitable for bearing light loads, while roller bearings are suitable for bearing heavy loads and impact loads. When the rolling bearing bears pure axial loads, thrust bearings are generally selected; when the rolling bearing bears pure radial loads, deep groove ball bearings or short cylindrical roller bearings are generally selected; when the rolling bearing bears pure radial loads and there is not much axial load, deep groove ball bearingsAngular contact ball bearing, tapered roller bearing and self-aligning ball or self-aligning roller bearing; when the axial load is large, the angular contact ball bearing and tapered roller bearing with larger contact angle can be selected, or the combination of radial bearing and thrust bearing can be selected, which is particularly suitable when extremely high axial load or large axial rigidity is specially required.
b. Allowable speed
There are great differences due to different types of bearings. Generally, bearings with small friction and heat generation are suitable for high speed. Rolling bearings shall be designed to work below their limit speed.
c. Rigid
When bearing bears load, elastic deformation will occur at the contact between bearing ring and rolling element. The amount of deformation is proportional to the load, and its ratio determines the size of bearing rigidity. Generally, the rigidity of bearing can be improved by bearing preloading; in addition, in bearing support design, the bearing support rigidity can also be improved by considering the combination and arrangement of bearing.
d. Centering performance and installation error
After the bearing is installed in the working position, it is often poor in installation and positioning due to manufacturing errors. At this time, the bearing is often subjected to excessive load due to reasons such as the degree of bailing and thermal expansion of the shaft, resulting in early damage. Automatic self-aligning bearings can overcome the defects caused by installation errors, so they are suitable for such purposes.
e. Installation and removal
Tapered roller bearings, needle roller bearings, etc. belong to the bearing type with separable inner and outer rings (the so-called separable bearing), which is easy to install and disassemble.
f. Marketability
Even bearings listed in the product catalog may not be sold in the market; on the contrary, some bearings not listed in the product catalog are produced in large quantities. Therefore, it should be clear whether the bearings used are easy to purchase.
Maintenance of rolling bearing
Storage and rust prevention maintenance of rolling bearings:
1. Storage room requirements
The warehouse shall not allow direct sunlight or rain, snow, dust, etc. to blow into the room; the warehouse shall be kept dry, and the relative humidity shall not exceed 60%; the temperature difference shall not change significantly, and the temperature shall be 10-20 ° C, the maximum shall not exceed 30 ° C, and the minimum shall not be less than 5 ° C. The optimal temperature shall be 18-20 ° C;The warehouse shall be equipped with ventilation, dust prevention and heating facilities; bearings shall not be stored in the same warehouse with acids, alkalis, chemicals, chemical raw materials, harmful gases or substances containing water
2. Storage and maintenance
The bearing shall be stored every 3 months (in humid and hot areas) Or conduct regular inspection once every six months, and set a maintenance date according to the surface condition and rust resistance of the oil seal. Generally, the planned maintenance period is not more than one year. For bearings that have reached the maintenance period, the bearing warehouse and the user organization must carry out rust prevention treatment again to keep them rust free, and allow them to continue to be stored. For bearings that have been delivered for more than one year but have good oil seal packaging, it can be based on the specific situation, and then reseal the package for maintenance after 3-6 months of extension.
Matters needing attention
Precautions during bearing installation:

  • 1. The thickness of the inner and outer spacer ring shall be well matched, and the parallelism of the two end faces of the spacer ring shall not exceed 0.002mm.
  • 2. The bearing must be selected
  • 3. The roundness of bearing seat hole and journal, the coaxiality of both ends of shell hole, and the radial runout of journal shall not exceed 0.003mm.
  • 4. The end face of the part in contact with the end face of the bearing ring shall be colored for inspection, and the contact area shall not be less than 80%
  • 5. It must be installed directionally
  • 6. It is not allowed to directly hit the ferrule with a hammer
  • 7. The datum plane (non typing surface) leans against the shaft shoulder, which is convenient for viewing the bearing code
  • 8. Do not drop dirt into the bearing ring
  • 9. Special tools, copper bars or manual hammering (small bearings) shall be used; sleeve shall be used for installation; press shall be used for installation.

Troubleshooting of rolling bearing
There are two kinds of fault phenomena of rolling bearings. One is that the temperature of the bearing installation part is too high, and the other is that there is noise in the bearing operation.
1. The bearing temperature is too high
When the mechanism is running, a certain temperature is allowed at the position where the bearing is installed. When touching the mechanism shell with hands, 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, 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; the load is too large; the bearing cage or rolling body is broken, 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, it indicates that the bearing is faulty.
The reasons for the noise of rolling bearings are complex. One of them is the wear of the mating surfaces of the inner and outer rings of the bearing. Because of this wear, the matching relationship between the bearing and the housing, and between the bearing and the shaft is damaged, which causes the axis to deviate from the correct position and produces 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 noiseIn addition, abnormal sound will be generated due to insufficient lubrication of the bearing, dry friction, and bearing breakage. After the bearing is worn and loose, the cage will become loose and damaged, which will also generate abnormal sound.
3. Bearing wear
The wear of rolling bearings 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 yielding ability (it cannot be recovered after deformation). The impact resistance and fatigue resistance are poor, 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, only when the machine is high temperature, large jumping range, abnormal noise, etc., will cause detection, but when people find out, most of the rolling shafts have been worn, resulting in machine shutdown.

3. Roller bearing

20230211094201 32410 - Bearing types: guidelines for selecting the correct bearing

What is roller bearing?
Roller bearings are rolling bearings that use short cylindrical, tapered or waist drum shaped rollers as the rolling body. They mainly have the structure types of centripetal short cylindrical rollers, double row centripetal spherical rollers, tapered rollers and thrust rollers.
Working principle of roller bearing
Tapered roller bearings mainly bear radial and axial combined loads. The bearing bearing capacity depends on the raceway angle of the outer ring. The larger the angle, the greater the bearing capacity. Tapered roller bearings have conical inner ring and outer ring raceways, and the tapered rollers are arranged between them. The projection lines of all conical surfaces meet at the same point of the bearing axis.
This design makes the tapered roller bearing particularly suitable for bearing compound (radial and axial) loads. The axial load capacity of the bearing is mostly determined by the contact angle α; the larger the angle α is, the higher the axial load capacity is. The angle size is expressed by the calculation coefficient e; the larger the e value is, the larger the contact angle is, the greater the applicability of the bearing to bear axial loads is.
Application of roller bearing
Tapered roller bearings are mainly used in elevator traction machines, engineering machinery, metal rolling equipment, paper making machinery, construction aggregate industry, industrial washing equipment, wind power spindles, coal mine scraper machines, textile machinery, cement elevators, industrial pumps, machine tools, cement mixers, band saws, motors, etc.
Classification of roller bearings
Classification of roller bearings: cylindrical roller bearings, long cylindrical roller bearings, needle roller bearings, tapered roller bearings, spherical roller bearings, spiral roller bearings, pillar hole roller bearings.
Selection Guide for Roller Bearings
In general, the steps for selecting bearings may be summarized as follows:

  • 1. Select the basic type, tolerance grade and clearance of bearings according to the working conditions of bearings (including load direction and load type, speed, lubrication pipeline, coaxiality requirements, positioning or non positioning, installation and maintenance environment, ambient temperature, etc.);
  • 2. Determine the bearing model by calculation according to the working conditions, stress conditions and life requirements of the bearing, or indicate the bearing model according to the use requirements, and then check the life;
  • 3. Check the rated load and limiting speed of the selected bearing.

The main considerations for selecting bearings are the limiting speed, required life and load capacity. Other factors are helpful to determine the final scheme of bearing type, structure, size, tolerance class and clearance requirements.
Maintenance of roller bearing
Maintenance of tapered roller bearing
1. Cleaning When the tapered roller bearing is disassembled for inspection, the appearance record shall be made by photography. In addition, the amount of residual lubricant shall be confirmed and the lubricant shall be sampled before cleaning the tapered roller bearing.

  • a. The cleaning of tapered roller bearings is divided into rough cleaning and fine cleaning, and a metal mesh frame can be placed at the bottom of the container used.
  • b. During rough cleaning, use a brush to remove the grease or adhesive in the oil. If you rotate the tapered roller bearing in the oil at this time, be careful that the rolling surface will be damaged due to foreign matters.
  • c. During fine cleaning, slowly rotate the tapered roller bearing in oil and carefully.

2. Inspection and judgment
In order to judge whether the removed tapered roller bearing can be reused, its dimensional accuracy, rotation accuracy, internal clearance, mating surface, raceway surface, cage and seal ring should be emphatically checked.
The judgment standard varies according to the mechanical performance, importance and inspection cycle. In case of the following damages, the tapered roller bearing cannot be reused and must be replaced.

  • 1) Fracture and defect of tapered roller bearing parts.
  • 2) Stripping of rolling surface of raceway surface.

Matters needing attention
Precautions for the use of bearings are as follows:
(1) Keep the tapered roller bearing and its surroundings clean.
Even small dust that cannot be seen by the eyes will have a bad effect on the bearing. Therefore, keep the surroundings clean to prevent dust from invading the bearing.
(2) Use carefully.
When the tapered roller bearing is strongly impacted in use, it will produce scars and indentations, which will become the cause of accidents. In serious cases, it will crack and fracture, so attention must be paid.
(3) Use appropriate operating tools.
Avoid replacing existing tools and use appropriate tools.
(4) Pay attention to the corrosion of tapered roller bearings.
When operating the bearing, the sweat on the hands will become the cause of rust. Pay attention to the operation with clean hands, and try to wear gloves.
Troubleshooting of roller bearing
Common faults and causes of rolling bearings:
1. Fault form:

  • (1) The bearing rotates difficultly and heats up;
  • (2) Abnormal sound occurs during bearing operation;
  • (3) The bearing produces vibration;
  • (4) The inner seat ring is peeled and cracked;
  • (5) Outer seat ring peeling and cracking;
  • (6) The bearing raceway and rolling element produce indentation.

2. Fault cause analysis
(1)Before assembly, the inspection was not careful. Before assembly, the bearing should be cleaned and carefully checked for rust, burrs, bruises and cracks on the inner and outer races, rolling elements and cages of the bearing; check whether the bearing clearance is appropriate, whether the bearing rotates freely, and whether there is sudden jamming; and check the size, roundness and cylindricity of the shaft diameter and bearing seat hole, and whether there are burrs or cracks on their surfacesUnequal concave convex. For single cantilever bearing pedestal, 0.1mm-0.25mm clearance shall be reserved between the joint surface of bearing cover and bearing pedestal and the outer circular surface of outer race to prevent the clearance from reducing and the wear from accelerating due to the “collar clamping” phenomenon at the “tile mouth” on both sides of outer pedestal, causing premature damage to the bearing.
(2) Improper assembly. Improper assembly will lead to the above various fault forms of the bearing, as well as the following situations:
A. Improper cooperation
The matching between the bearing inner hole and the shaft adopts the basic hole system, and the matching between the bearing outer circle and the bearing seat hole adopts the basic shaft system. Generally, the shaft and the bearing inner race of centrifugal pumps, centrifuges, reducers, motors and centrifugal compressors operating under normal load use j5, js5, js6, k5, k6, m6 for matching, and the bearing seat hole and the bearing outer race use j6, j7 for matching. The rotating race(The inner race of most bearings is a rotating race, the outer race is not a rotating race, and the opposite is true for a few bearings). Interference fit is usually used to prevent the race from rolling and sliding on the mating surface of the shaft diameter and bearing seat hole under load.
However, sometimes due to the inaccurate measurement of the shaft diameter and bearing seat hole size or the roughness of the mating surface does not meet the standard requirements, excessive interference fit is caused, which causes the bearing race to be greatly squeezed, resulting in the reduction of the radial clearance of the bearing itself, making the bearing difficult to rotate, heat, wear aggravation or seizure, and in serious cases, it will cause the inner and outer races of the bearing to crack during assembly. Do not rotate the raceThe fit with small clearance or interference is often used. If the seat ring is not rotated, slight creep may occur, so that the contact surface between the seat ring and the rolling element is constantly replaced, and the raceway of the seat ring is evenly worn. At the same time, the axial seizure of the rolling element in the bearing caused by the thermal elongation of the shaft can be eliminated. However, if the clearance is too large, the non rotating seat ring will rotate with the rolling element, resulting inThe shaft (or bearing seat hole) and inner race (or outer race) are severely worn, and friction causes bearing heating and vibration
Methods of Eliminating Faults of Roller Bearings

  • (1) When replacing the bearing, carefully check the new bearing, and carefully check the shaft diameter, bearing seat hole and rotor;
  • (2) When assembling and disassembling bearings, strictly implement the maintenance process and operate carefully to avoid bearing damage caused by improper assembly and disassembly;
  • (3) Fill and change oil on time to ensure that the bearing is always in good condition;
  • (4) Carefully check during operation, and timely eliminate the hidden trouble found.

4. Ball bearing

20230211120756 50167 - Bearing types: guidelines for selecting the correct bearing

What is a ball bearing?

Ball bearing is a kind of rolling bearing. The ball bearing is installed between the inner steel ring and the outer steel ring, and can bear a large load. It is also called ball bearing. Ball bearing is better than journal bearingThe rotating friction resistance of the ball bearing is small, so the temperature generated by friction will be relatively low at the same speed. The ball bearing has single row centripetal, double row centripetal spherical, centripetal thrust, thrust and thrust centripetal structures (see figure)This kind of bearing is mainly used to bear radial load, but also can bear small axial load. It is suitable for transmission shafts with multiple supports and large deflection deformation. The two-way thrust ball bearing has two live rings, one tight ring, two rows of rollers and two cages.
Working principle of ball bearing
Working principle of deep groove ball bearing: when working, half of the inner ring rotates while the outer ring does not move, the rolling element rolls between the inner and outer rings. At this time, the cage evenly separates the rolling elements to reduce friction and wear between the rolling elements. The cage also plays the role of rolling equidistantly, so as to reduce friction and wear between the rolling elements. The rolling element not only revolves around itselfThe axis rotates along the raceway of the ring and around the axis of the bearing, with a certain amount of sliding while rolling. The rolling body changes the friction between relative moving surfaces into rolling friction.
Application of ball bearing
Deep groove ball bearings can be used in gearboxes, instruments, motors, household appliances, internal combustion engines, transportation vehicles, agricultural machinery, construction machinery, engineering machinery, roller skates, yo yos, etc.
Classification of ball bearings
Rolling bearing with steel ball as rolling element. The ball bearing has single row centripetal, double row centripetal spherical, centripetal thrust, thrust and thrust centripetal structures
Ball bearingSelection Guide
In general, the steps for selecting bearings may be summarized as follows:

  • 1. Select the basic type, tolerance grade and clearance of bearings according to the working conditions of bearings (including load direction and load type, speed, lubrication pipeline, coaxiality requirements, positioning or non positioning, installation and maintenance environment, ambient temperature, etc.);
  • 2. Determine the bearing model by calculation according to the working conditions, stress conditions and life requirements of the bearing, or indicate the bearing model according to the use requirements, and then check the life;
  • 3. Check the rated load and limiting speed of the selected bearing.

The main considerations for selecting bearings are the limiting speed, required life and load capacity. Other factors are helpful to determine the final scheme of bearing type, structure, size, tolerance class and clearance requirements.
Maintenance of ball bearing
Maintenance problems: the water circulation should not be short of water. Always pay attention to the oil level, replenish the oil in time, and do not be short of oil. According to the quality of the oil, change the oil in time. When a new bearing starts to use, change the oil twice; when the machine stops, wash the bearing with gasoline or diesel oil, and then change the oil. The damage to the bearing caused by lack of oil or full oil is the same. When the oil level is high, it cannot guarantee enough oil dispersionThermal space. When the oil level is low, enough lubrication and heat dissipation cannot be guaranteed.
Regular lubrication and maintenance of bearings during operation
1. Grease lubrication
The relubrication of bearings should preferably be carried out during the planned equipment shutdown period and supplemented regularly. At the same time, the old grease should be removed or the old grease should be squeezed out through the oil drain. Before adding fresh grease, the grease nozzle should be wiped clean. If there is no grease nozzle in the bearing box, the bearing box cover or end cover should be opened to remove the old grease. After cleaning, new grease of the same model should be addedFresh oil.
2. Lube oil lubrication
Regularly check the oil level and quality of the lubricating oil. Generally, the normal oil level should be within the equipment oil level window or the marked range of 1/2-2/3. If the oil replenishing pipe is an oil cup, the oil level displayed only represents the oil replenishing capacity, while the oil level of the bearing box meets the operating requirements. If the oil level in the oil cup is less than 1/4 of its total volume, oil replenishing can be considered.
Inspection and oil replenishing methods: take a small amount of lubricating oil as a sample and compare it with fresh lubricating oil. Competent organizations can consider conducting oil quality tests to ensure that the oil quality is qualified. If the sample looks like a cloud, it may be the result of mixing with water, which is commonly known as oil emulsification. At this time, the lubricating oil should be replaced. If the sample process becomes dark or thick,Then it may indicate that the lubricating oil has started to carbonize, and the old lubricating oil should be completely replaced. If possible, use fresh lubricating oil to flush the oil circuit. When replacing the lubricating oil, ensure that the new and old lubricating oil models are the same, and supplement the oil level that meets the requirements.
With an oil bath lubrication system, if the oil temperature is below 60 ℃ (140 ° F) and the lubricating oil is not contaminated, the lubricating oil can be replaced once a year. If the oil temperature is 60-100 ℃ (140-210 ° F), the lubricating oil needs to be replaced four times a year. If the oil temperature is 100-120 ℃ (210-250 ° F), the lubricating oil needs to be replaced once a month. If the oil temperature is 120 ℃ (250 ° F)The lubricating oil shall be replaced once a week.
Correct installation and maintenance is an important factor for the normal operation of the bearing. At the same time, attention must be paid to keeping the cleanliness of the bearing. The bearing must be protected from pollutants and moisture, and must be installed and lubricated correctly. In addition, the design of the bearing arrangement, the condition of the oil seal, the form and replacement cycle of the lubricant, and special maintenance also play an important role, and must be addedTo focus on.
matters needing attention
Precautions after hot installation of bearings: after installation, pull the outer ring, rotate it to the maximum included angle, and then close and align it. If there are impurities in the bearing, it is difficult to align it. When moving towards the bearing seat, use a feeler gauge to plug the gap between the bearing and the bearing seat. Find the concentricity and perpendicularity of the shaft. When there is no problem, close the box.(The experience method of gland: after the box is closed and tightened, the screw shall be rotated for another 1/4 or 1/2 turn, with a maximum of 3/4 turn)After the box is closed, several people rotate the shaft by hand, and the rotation is the best. Then refuel and fill it up at one time, so that the oil line can not be seen in the oil mirror. Release the oil drain hole, and drain the oil, so that the oil line is between 1/2 and 2/3 oil levels, and once again ensure that the oil tank is clean. Start the machine if there is no error after inspection. Turn it for more than ten minutes, stop the machine for inspection, and then start the machine if there is no error.
Troubleshooting of ball bearing
Simple diagnosis of rolling bearing:
1. Monitoring Rolling Bearings by Auscultation
The common tool for monitoring the working state of rolling bearings by auscultation is a long screw screwdriver with wooden handle, or a hard plastic hose with an outer diameter of about φ 20mm can be used. In contrast, the use of electronic stethoscope for monitoring is more conducive to improving the reliability of monitoring.
1) Sound characteristics of rolling bearings under normal working conditions
When the rolling bearing is in normal working condition, it operates smoothly and briskly without stagnation. The sound generated is harmonious without noise. Even and continuous “gurgling” sound or low “booming” sound can be heard. The noise intensity is not large.
2) Bearing fault reflected by abnormal sound

  • (1) The bearing emits a uniform and continuous “sibilant” sound, which is generated by the rotation of the rolling element in the inner and outer rings, and contains irregular metal vibration sound unrelated to the speed. It is generally manifested by insufficient grease filling in the bearing, which should be supplemented. If the equipment is shut down for a long time, especially under the low temperature in winter, the bearing sometimes emits “sibilant” sound during operationThis is related to the smaller radial clearance of the bearing and the smaller working penetration of the grease. The bearing clearance should be properly adjusted and the new grease with a higher penetration should be replaced.
  • (2) The bearing emits a uniform periodic “rolling” sound in the continuous “gurgling” sound, which is caused by scars, grooves and rust spots on the rolling element and inner and outer race raceways. The sound period is proportional to the bearing speed. The bearing should be replaced.
  • (3) The bearing emits discontinuous “stem” sound, which is caused by the fracture of cage or inner and outer rings. The machine must be stopped immediately to replace the bearing.
  • (4) The bearing emits irregular and uneven “chug” sound, which is caused by impurities such as iron chips and sand particles falling into the bearing. The sound intensity is small and has no relationship with the number of revolutions. The bearing should be cleaned, re greased or replaced with oil.
  • (5) The bearing emits a continuous and irregular “rustling” sound, which is generally related to the loose fit between the inner ring and the shaft of the bearing or the loose fit between the outer ring and the bearing hole. When the sound intensity is high, the matching relationship of the bearing should be checked, and the problems found should be repaired in a timely manner.
  • (6) The bearing emits a continuous screeching sound, which is caused by dry friction caused by poor lubrication or oil shortage of the bearing, or the local contact of the rolling element is too tight, such as the deflection of the inner and outer ring raceways, the tight fit of the inner and outer rings of the bearing, etc. The bearing should be checked in time to find out the problem and deal with it.

3) Requirements for monitoring with electronic stethoscope

  • (1) In the process of monitoring, similar monitoring points or monitoring points with close working conditions shall be selected as far as possible for sound comparison. Any abnormality found shall be regarded as a defect and must be thoroughly checked. For a single equipment, in order to overcome the disadvantage of incompatibility, the sound recording of the monitoring point in the normal state can be used as the basis for comparison in future monitoring.
  • (2) To correctly select the position of the monitoring point, the vibration direction to be measured should be consistent with the sensitive direction of the sensor, so that the measurement direction is the direction with the maximum vibration intensity. The sensor and the measured surface should be at right angles, and the error should be controlled within 10 °.
  • (3) The measuring surface shall be clean and flat without rust and paint, and the concave part shall be polished to make it smooth and flat.
  • (4) The measuring force of the pressure probe should be 10-20N.

2. Monitoring Rolling Bearings by Measurement
By measuring the temperature rise of the bearing during operation, it is generally difficult to monitor the fatigue peeling, cracks or indentation and other local damages of the bearing, especially in the initial stage of the damage, it is almost impossible to find any problems. When the temperature rise of the bearing occurs after long-term normal operation, the problems generally reflected are not only quite serious, but also will develop rapidly, resulting inThe bearing is damaged. At this time, intermittent monitoring often leads to missing monitoring. If the temperature of the bearing is found to exceed 70-80 ℃ during monitoring, it should be stopped immediately for inspection.
For newly installed or readjusted rolling bearings, the quality of bearing installation and adjustment can be judged by monitoring the temperature rise within the specified time through temperature measurement, especially when the clearance is too tight, the temperature rise will be too high. If problems are found, timely adjustment is beneficial to extending the service life of rolling bearings.

5. Rotary table bearing

20230211121005 29168 - Bearing types: guidelines for selecting the correct bearing

What is a turntable bearing?

Turntable bearing is a large bearing with special structure, which can simultaneously bear large axial load, radial load, overturning torque and other comprehensive loads, and integrates support, rotation, transmission, fixation and other functions. Generally, the turntable bearing itself is equipped with mounting holes, lubricating oil and sealing devices, which can meet the requirements of various types of main engines operating under various working conditionsDifferent requirements; on the other hand, the turntable bearing itself has the characteristics of compact structure, convenient guide rotation, simple installation and easy maintenance, and is widely used in large rotary devices such as lifting and transportation machinery, mining machines, construction machinery, port machinery, wind power generation, medical equipment, radar, etc.
Application of rotary table bearing
Turntable bearings are widely used. Construction machinery is the first and most widely used place for turntable bearings, such as earth moving machinery, eccentric hand, disintegrator, stacker reclaimer, grader, roller, dynamic compactor, rock drilling machinery, tunneling machine, etc.
In addition to all kinds of engineering machinery, the application scope of rotary table bearings has gradually expanded. Similar equipment platforms such as port equipment, metallurgical equipment, drilling platforms, etc. have begun to use rotary table bearings in a large range to replace the original bearings.
Classification of rotary table bearings
There are four categories of turntable bearings: three row combined roller turntable bearings, double row angular contact ball turntable bearings, single row cross roller turntable bearings, and single row four point contact ball turntable bearings.
Maintenance of rotary table bearing
Maintenance of rotary table bearing:
After the large rotary table bearing installed and put into operation for 100 consecutive hours, it is necessary to comprehensively check whether the pre tightening torque of the mounting bolts meets the requirements, and then repeat the above inspection every 500 cumulative hours of operation. Problems should be found and solved in a timely manner.
After the rotary table is installed in place, proper amount of grease should be added. When adding grease, the bearing should be rotated while adding grease to make the grease evenly distributed. After the rotary table bearing works for a period of time, it will inevitably lose some grease. Therefore, for the rotary table bearing in normal operation, grease should be added every 50-100 hours of cumulative operationThe rotary table bearing working under working conditions should be filled with grease once after 30-40 hours of operation.
When the rotary table bearing runs continuously for 1000 hours, a comprehensive maintenance should be carried out for the bearing. The bearing needs to be thoroughly cleaned. Professionals should be asked to remove the bearing seal ring and clean the internal grease and dirt. Kerosene or gasoline should be used for cleaning, and diesel can also be used instead. After cleaning, restore the installation, and then add an appropriate amount of new grease.
When the machine using the rotary table bearing needs to be stopped for a long time for storage, enough grease must be added to prevent the internal corrosion and damage of the rotary table bearing.
matters needing attention
Precautions for use of rotary table bearing:

  • 1. When the rotary table bearing leaves the factory, the raceway is coated with a small amount of No. 2 or No. 3 lithium based grease. When it is started, the user should refill it with new grease according to different working conditions.
  • 2. During the use of rotary table bearings, lubricating grease should be added regularly. Generally, ball rotary table bearings should be oiled every 100 hours of operation, and roller rotary table bearings should be oiled every 50 hours. In special working environments, such as high temperature, high humidity, much dust, large temperature changes, and continuous work, the lubrication cycle should be shortened. When lubricating grease, the rotary table bearings should be slowly rotated to make the lubricating greaseFill evenly.
  • 3. For the rotary table bearing with internal or external teeth, the sundries shall be removed frequently and the corresponding grease shall be applied.
  • 4. According to different working conditions, customers can choose different grease according to specific requirements, so as to meet the work needs with the best performance.
  • 5. After the turntable bearing runs for 100 hours for the first time, the bolt pre tightening force shall be checked. After that, the bolt pre tightening force shall be checked every 500 hours of operation, and sufficient pre tightening force must be maintained.
  • 6. Pay attention to the operation of the rotary table bearing during use. In case of abnormal conditions such as noise, impact and sudden increase of power, stop the machine immediately for inspection, eliminate the fault, and disassemble and inspect if necessary.
  • 7. It is forbidden to directly flush the rotary table bearing with water during use to prevent water from entering the raceway, and strictly prevent hard foreign matters from approaching or entering the tooth engagement area.
  • 8. Regularly check the integrity of the seal. If the seal ring is damaged, it should be replaced in time. If it falls off, it should be reset in time.

Troubleshooting of rotary table bearing
Causes of common faults of rotary table bearing.
1、 The temperature of the rotary table bearing is too high: during the operation of the mechanism, a certain temperature is allowed at the position where the rotary table bearing is installed. When touching the mechanism housing with hands, it should be normal not to feel hot, otherwise it indicates that the temperature of the rotary table bearing is too high.
The reasons for the high temperature of the rotary table bearing are: the quality of the lubricating oil does not meet the requirements or deteriorates, the viscosity of the lubricating oil is too high; the mechanism assembly is too tight (insufficient clearance); the rotary table bearing assembly is too tight; the rotary table bearing race rotates on the shaft or in the shell; the load is too large; the rotary table bearing cage or rolling body is broken, etc.
2、 Rotary table bearing noise: a slight running noise is allowed during the operation of the rotary table bearing. If the noise is too loud or there is abnormal noise or impact, it indicates that the rotary table bearing is faulty.
The reasons for the noise of the rotary table bearing are complex:

  • 1. The mating surfaces of the inner and outer rings of the rotary table bearing are worn. Because of this kind of wear, the matching relationship between the rotary table bearing and the housing, and between the rotary table bearing and the shaft is damaged, which causes the axis to deviate from the correct position and produces abnormal sound when the shaft moves at high speed. When the rotary table bearing is fatigue, its surface metal will peel off, which will also cause the radial clearance of the rotary table bearing to increase and produce abnormal sound.
  • 2. Inadequate lubrication of rotary table bearings, dry friction, and broken rotary table bearings will produce abnormal sound.
  • 3. When the rotary table bearing is worn and loose, the cage will become loose and damaged, which will also cause damage to the rotary table bearing with abnormal noise. When the rolling rotary table bearing is disassembled for inspection, the fault and damage reason of the rotary table bearing can be judged according to the damage condition of the rotary table bearing.

3、 Metal peeling off on the raceway surface: the rolling body of the rotary table bearing and the raceway surfaces of the inner and outer rings are subject to periodic pulsating loads, resulting in periodic contact stress. When the number of stress cycles reaches a certain value, fatigue peeling will occur on the working surface of the rolling body or the raceway surfaces of the inner and outer rings. If the load of the rotary table bearing is too large, this fatigue will be aggravated. In additionIf the rotary table bearing is installed incorrectly and the shaft is bent, the raceway will also peel off. The fatigue peeling of the raceway of the rotary table bearing will reduce the operating accuracy of the shaft, causing vibration and noise in the mechanism.
4、 Plastic deformation: uneven pits appear on the contact surface between the raceway and the roller of the rotary table bearing, indicating that the rotary table bearing has plastic deformation. The reason is that the local stress on the working surface of the rotary table bearing exceeds the yield limit of the data under the action of a large static load or impact load, which generally occurs on the rotary table bearing rotating at a low speed.
5、 Burn of rotary table bearing: the raceway and rolling body of the burnt rotary table bearing have a backfire color. The causes of the burn are generally insufficient lubrication, unqualified or deteriorated lubricating oil, and too tight assembly of the rotary table bearing.
6、 Cracks on the bearing race of the rotary table: the cracks on the bearing race of the rotary table may be caused by the tight fitting of the rotary table bearings, the looseness of the foreign or inner rings of the rotary table bearings, the deformation of the containing parts of the rotary table bearings, and the poor surface processing for installing the rotary table bearings.
7、 Broken cage: the reason is insufficient lubrication, broken rolling element, and skewed seat ring.
8、 The metal of the cage adheres to the rolling element: the possible reason is that the rolling element is stuck in the cage or the lubrication is insufficient.
9、 The raceway of the seat ring is severely worn: foreign matters may fall into the seat ring, the lubricating oil is insufficient or the lubricating oil brand is inappropriate.

6. Joint bearing

20230211121339 46143 - Bearing types: guidelines for selecting the correct bearing

What is spherical plain bearing?

Spherical plain bearing is a kind of spherical plain bearing. Its sliding contact surface is an inner spherical surface and an outer spherical surface. When moving, it can rotate and swing at any angle. It is made by a variety of special processing methods, such as surface phosphating, mouth blasting, pad inlaying, spraying, etc. Spherical plain bearing has the characteristics of large load capacity, impact resistance, corrosion resistance, wear resistance, self-aligning, good lubrication, etc.
Operating principle of rotary table bearing
Spherical plain bearing is a kind of sliding bearing with special structure. Its structure is simpler than that of rolling bearing. It is mainly composed of an inner ring with an outer spherical surface and an outer ring with an inner spherical surface. It can withstand large loads. According to its different types and structures, it can withstand radial loads, axial loads or combined loads of radial and axial loads. Spherical plain bearing is generally used for speedThe lower swing motion (i.e. angular motion), because the sliding surface is spherical, can also make inclined motion (i.e. centering motion) within a certain angle range, and can still work normally when the supporting shaft and the axle housing hole are not concentric.
Application of rotary table bearing
Spherical bearings are widely used in engineering hydraulic cylinders, forging machine tools, engineering machinery, automation equipment, automobile shock absorbers, hydraulic machinery and other industries. Spherical bearings are spherical sliding bearings. The basic type is composed of inner and outer rings with spherical sliding spherical contact surfaces. According to their different structures and types, they can withstand radial load, axial load, or radial and axial loadCombined loads acting simultaneously.
Because the spherical sliding contact area of spherical plain bearings is large and the inclination angle is large, and because most spherical plain bearings adopt special processing methods, such as surface phosphating, zinc plating, chromium plating or outer sliding surface lining, padding, spraying, etc., they have greater load capacity and impact resistance, and have corrosion resistance, wear resistance, self-aligning, good lubrication or self-lubricating without lubricating dirtDue to the characteristics of material pollution, it can work normally even if it is installed incorrectly. Therefore, spherical plain bearings are widely used for low speed oscillating, tilting and rotating movements.
Classification of rotary table bearings
Classification of spherical plain bearings: radial spherical plain bearings, angular contact spherical plain bearings, thrust spherical plain bearings, rod end spherical plain bearings, self-lubricating radial spherical plain bearings, self-lubricating angular contact spherical plain bearings, self-lubricating thrust spherical plain bearings, self-lubricating rod end spherical plain bearings.
Rotary table bearingSelection Guide
In any case, the selected fit of the spherical plain bearing shall not cause uneven deformation of the ring, and the selection of its fit property and grade must be determined according to the bearing type, support form, load size and other working conditions.
Maintenance of rotary table bearing
Lubrication: When the speed generated by the applied load and swing movement is very small, the oil fed spherical plain bearing can be operated without lubrication. However, in general, the grease must be supplemented regularly. During the initial installation and operation, it is recommended that the lubrication cycle should be shortened appropriately.
Non oil feeding spherical plain bearing can be used without lubrication. However, if lithium soap base grease is added before operation, the service life of spherical plain bearing will be extended. If grease is injected into the space around the bearing, the spherical plain bearing will be more effective in preventing the invasion of dust and foreign matters.
Matters needing attention
When assembling the spherical plain bearing series, it is necessary to pay special attention to the position of the split surface of the outer ring. In order to avoid the load directly acting on the split surface, it is necessary to maintain the split surface at a right angle to the corresponding direction.
The loading and unloading of spherical bearings shall follow the following principle, that is, the force exerted by assembly and disassembly cannot be transmitted directly through the spherical sliding surface. In addition, auxiliary loading and unloading tools, such as sleeves, disassemblers, etc., shall be used to apply the loading and unloading force exerted by the outside directly and evenly to the matched rings, or use auxiliary methods such as heating for no-load loading and unloading.
Troubleshooting of rotary table bearing
There are many causes of bearing damage, such as improper installation, dirt invasion or moisture invasion, which are common causes of early damage of many bearings. Analysis of common causes of bearing damage and corresponding preventive measures that can extend the life of spherical plain bearings.
A. Improper operation:
Improper installation, operation or removal may cause cage deformation or defect Preventive measures: use proper operation, installation and removal tools
B. Insufficient lubrication:
Inadequate or improper lubrication may lead to element scratches or serious bearing deformation Preventive measures: improve the lubrication system, supplement or replace the lubricant regularly and properly
C. Rust and corrosion:
Contact with water may cause corrosion and rusting of bearing elements. Rusted bearings may cause peeling during operation Preventive measures: check the sealing regularly to ensure good sealing effect, and store spherical plain bearings correctly
D. Current:
When the spherical plain bearing is powered on while it is rotating, it may cause grooves or nicks. When the bearing is stationary, improper grounding of power operation may cause slight burns Preventive measures: reduce or avoid current flowing through the bearing through proper grounding connection before welding components other than the bearing
E. External data:
Abrasive particle pollution and debris intrusion may lead to wear, scratch and depression of bearing working surface Preventive measures: remove the invasive particles and debris, replace the lubricant, and check the sealing system
F. Eccentricity:
Eccentricity, inclination or excessive load may cause geometric stress concentration or surface peeling.

7. Linear bearing

20230211121616 38461 - Bearing types: guidelines for selecting the correct bearing

What is linear bearing?

Linear bearing is a kind of linear motion system, which is used in combination with the cylindrical shaft for linear travel. Because the bearing ball contacts the bearing outer sleeve point, the steel ball rolls with the minimum friction resistance, so the linear bearing has small friction, is relatively stable, does not change with the bearing speed, and can obtain a stable linear motion with high sensitivity and precision. Linear bearing consumption also has its limitations,The most important thing is that the bearing has poor impact load capacity and bearing capacity. Secondly, the linear bearing has large vibration and noise when moving at high speed. The quick, easy and optimal automatic selection of linear bearings is included. Linear bearings are widely used in the sliding parts of precision machine tools, textile machinery, food packaging machinery, printing machinery and other industrial machinery.
Because the bearing ball contacts with the bearing point, the use load is small. The steel ball rotates with minimal friction resistance, thus obtaining high-precision and stable movement.
The plastic linear bearing is a linear motion system with self-lubricating characteristics. The biggest difference between the metal linear bearing and the metal linear bearing is that the metal linear bearing is a rolling friction, and the point contact between the bearing and the cylindrical shaft, so this kind of bearing is suitable for low load high-speed movement; while the plastic linear bearing is a sliding friction, and the surface contact between the bearing and the cylindrical shaft, so this kind of bearing is suitable for high load medium low speed movement。
Working principle of linear bearing
Linear bearing is a kind of linear motion system, which is used in combination with the cylindrical shaft for linear travel. Since the bearing ball contacts the bearing outer sleeve point, the steel ball rolls with the minimum friction resistance, so the linear bearing has small friction, is relatively stable, does not change with the bearing speed, and can obtain a stable linear motion with high sensitivity and precision.
Application of linear bearing
Linear bearings are more and more widely used in precision equipment or special machinery industries such as electronic equipment, food machinery, packaging machinery, medical machinery, printing machinery, textile machinery, machinery, instruments, robots, tool machinery, CNC machine tools, automobiles, and digital three-dimensional benchmark measuring equipment.
Classification of linear bearings

  • 1) Standard type, clearance adjusted linear bearing, open type linear bearing, extended linear bearing, universal linear bearing
  • (2) Flange type linear bearings can be divided into: circular flange type, flange type, elliptical flange type, circular flange type, flange type, elliptical flange type and extended circular flange type.

According to the specification system:
It is divided into two series, namely LM and LME series. The code LM series is used in Asia, Southeast Asia, Japan, South Korea, China, etc. Based on metric dimensions, the outer diameter tolerance of the straight shaft is generally h7. LME series is mostly used in Europe, the United States, Germany, Italy, etc. Based on English dimensions, there are also metric dimensions, and the outer diameter tolerance of the straight shaft is generally g6Large series of structural features, except for different sizes and hole tolerances, their structures are roughly the same.
By shape:

  • 1: Straight cylinder type (the shape is like a cylinder, which is usually installed with a snap ring, and is used in the case of small installation size)
  • 2: Flange type (there is a mounting flange at the end or in the middle, which can be installed with screws. The flange is generally divided into three types: circular, square and trimming)
  • 3: Open type (in the shape of a straight cylinder, with axial slits on the surface, used for occasions requiring clearance adjustment, divided into large opening and small opening)

By performance:

  • 1: Ordinary type (use for general performance requirements)
  • 2: Super (for occasions requiring long service life and heavy load performance)

Selection Guide

  • 1. Straight cylinder type: It is generally installed with a snap ring, and is used for installation of small size occasions.
  • 2. Flange type: there is a mounting flange at the end or in the middle, which can be installed with screws. The flange is generally divided into three types: circular, square and trimming.
  • 3. Open type: the shape is like a straight cylinder, with axial slits on the surface. It is used for occasions requiring clearance adjustment. It can be divided into two types: large opening and small opening.

Maintenance of linear bearing
Maintenance of metal linear bearing: lubrication and friction: inject anti-corrosion oil into the linear bearing. If grease lubrication is used, remove the anti-corrosion oil with kerosene or organic solvent first, and then add lubricating grease after air drying. (It is recommended to use lithium soap grease with viscosity mark of N0.2.)If oil lubrication is used, it is not necessary to remove the anti-corrosion oil. According to the temperature change, the ISO viscosity grade VG15-100 lubricating oil can be selected. Shaft lubrication can be supplied from the oil supply pipe, or from the oil hole on the outer bearing seat. Since the sealing ring will scrape off the lubricating oil, oil lubrication is not applicable to bearings with sealing rings without holes.
Maintenance of plastic linear bearing: since the sliding film in the plastic linear bearing is made of self-lubricating plastic, it does not need additional oil supply and maintenance during use; moreover, because the plastic linear bearing has a chip removal groove, it does not need maintenance even if the bearing or shaft is full of dust, and the dust will automatically be brought out of the chip removal groove during movement; only when the sliding filmAfter wear failure, replace the internal sliding film directly; maintenance is very convenient.
Matters needing attention
Installation precautions:

  • 1. When assembling the linear bearing in the bearing seat, do not directly collide with the side end of the bearing housing, snap ring and seal ring. Use special tools to press in evenly and slowly.
  • 2. When assembling a linear bearing and a special shaft, it should be noted that the axis of the shaft and the axis of the bearing should be kept parallel, and excessive angle should not be used for installation. Excessive angle may easily affect the accuracy and service life of the bearing, or even directly cause the steel ball to fall off.

Precautions:
Linear bearings are designed to be used in linear repeated motion, not suitable for rotary motion, which will affect the life of linear bearings.
Troubleshooting of linear bearing
The fault phenomenon of linear bearing is generally shown in two ways: one is that the temperature of bearing installation part is too high, and the other is that there is noise in bearing operation.
1. Bearing temperature is too high
When the mechanism is running, a certain temperature is allowed at the position where the bearing is installed. When touching the mechanism shell with hands, it should be normal not to feel hot, otherwise it indicates that the bearing temperature is too high. The reasons for the high bearing temperature are: the quality of the lubricating oil does not meet the requirements or deteriorates, the viscosity of the lubricating oil is too high; the mechanism is too tight (insufficient clearance); The bearing assembly is too tight; the bearing race rotates on the shaft or in the housing; the load is too large; the bearing cage or linear body is broken, etc.
2. Bearing noise

The linear bearing is allowed to make a slight running noise during operation. If the noise is too loud or there is abnormal noise or impact, it indicates that the bearing is faulty. The reason for the noise of the linear bearing is relatively complex. One of the reasons is the wear of the matching surfaces of the inner and outer rings of the bearing. Because of this wear, the matching relationship between the bearing and the housing, and between the bearing and the shaft is damaged, causing the axis to deviate from the correct positionWhen the shaft is moving at a high speed, abnormal sound will be generated. When the bearing is tired, the metal on its surface will peel off, which will also increase the radial clearance of the bearing and generate abnormal sound. In addition, abnormal sound will be generated due to insufficient lubrication of the bearing, dry friction, and bearing breakage. When the bearing is worn and loose, the cage will become loose and damaged, which will also generate abnormal sound.

How to select the correct bearing?

The following aspects are usually considered when selecting the correct bearing:

  • Bearing type: according to the load type, speed, application environment and other factors, select the appropriate bearing type, such as ball bearing, roller bearing, thrust bearing, etc.
  • Size and load capacity: select bearings with appropriate size and load capacity according to the use environment and required load capacity.
  • Data and lubricationThe Conduit: Select appropriate bearing data according to the application environment, such as steel, ceramics or plastics, and select appropriate lubrication pipes, such as oil lubrication or grease lubrication.
  • Bearing accuracy and noise level: Select bearings with appropriate accuracy and noise level according to application requirements.
  • Bearing life and reliability: considering the life and reliability requirements of bearings, select the appropriate brand and quality level of bearings.

Finally, selecting the correct bearing requires comprehensive consideration of the above factors and comprehensive evaluation according to the specific application needs.

Selection Guide for Bearings

1. Whether the outer package is clear
Generally, brands produced by regular manufacturers have their own special designers to design the external packaging, and arrange factories with qualified production conditions to produce. Therefore, the product packaging should be very clear and unambiguous from lines to color blocks.
2. Whether the steel seal is clear
Each bearing product will be printed with its brand name, label, etc. Although the font is very small, the products produced by formal manufacturers use steel stamp technology to print and emboss before overheating treatment, so the font is small, but it is deeply concave and very clear. Generally, the font of counterfeit products is not only vague, but also becauseThe printing technology is rough, the font is floating on the surface, and some can even be easily erased by hand or the manual marks are serious.
3. Is there any noise
Hold the inner sleeve of the bearing with the left hand, and rotate the outer sleeve with the right hand in small amplitude to hear whether there is noise during the operation of the bearing. Because most of the counterfeit products are produced under backward conditions and are operated by hand workshops, it is inevitable that impurities such as dust and sand will be mixed into the bearing body during the production process, so there will be noise or unsmooth operation when the bearing rotatesThis is the key to judge whether the products come from the brand products of regular manufacturers with strict production standards and machine operation.
4. Surface
Whether there are muddy oil stains on the surface requires us to pay special attention when purchasing imported bearings. Since there is still a certain gap between domestic anti rust technology and foreign advanced manufacturing countries, it is easy to leave thick oil stains when carrying out anti rust treatment on the bearing body, which is sticky and thick when touching by hand, and there is almost no trace of anti rust oil on the imported bearingsAccording to the insiders, a special smell can be smelled on the imported bearings by a particularly careful person, which is the smell of rust preventive oil.
5. Whether the chamfer is even
The so-called bearing chamfer is the junction between the horizontal and vertical surfaces. Due to the limitation of production technology, the fake bearing products are not satisfactorily processed at these corners, which can be easily identified.
6. Packaging
Bearing packaging includes inner packaging and outer packaging:
After the bearing is manufactured and inspected as qualified, it shall be cleaned and rust proof, and then put into the inner package to achieve the purpose of waterproof, moisture-proof, dust-proof, impact proof, maintaining the quality and accuracy of the bearing, and facilitating the use and sales.
The inner packaging of bearings is divided into three categories according to the rust prevention period:

  • ① Short anti rust period packaging: the anti rust period is 3-6 months. It is applicable to bearings that are shipped in large quantities to the same subscriber and put into use in a short period of time. Simple packaging is adopted based on the principle of convenient use as agreed by both parties.
  • ② General rust proof packaging: the rust proof period is one year, suitable for general purpose bearings.
  • ③ Long rust proof packaging: the rust proof period is two years, suitable for special and precision bearings.

The bearing inner packaging materials include polyethylene plastic cylinder (box), kraft paper, plain and corrugated polyethylene composite paper, paper box, polyethylene or polyethylene plastic film, nylon fastening belt or plastic braided fastening belt, waterproof high-strength plastic belt, linen bag, etc. The above data shall ensure that the corrosion resistance test of the materials is qualified.

Maintenance of bearings

Disassembly of bearing
The bearing is disassembled for regular maintenance and replacement. After disassembly, if the bearing continues to be used or needs to be checked, its disassembly should also be carried out with the same care as the installation. Pay attention not to damage the bearing parts, especially the disassembly of interference fit bearings, which is difficult to operate.
It is also very important to design and make disassembly tools according to the needs. During disassembly, study the disassembly method, sequence, and investigate the matching conditions of bearings according to the drawings, so as to ensure the safety of disassembly.
Disassembly of the outer ring For the outer ring with interference fit, set several screws for extruding the screw rod of the outer ring on the circumference of the shell in advance, tighten the screw rod evenly at the same time, and disassemble at the same time. These screw holes are usually covered with blind plugs, tapered roller bearings, and other separate bearings. Set several notches on the housing retaining shoulder, use cushion blocks, use a press to disassemble, or gently knock to disassemble.
The disassembly of the inner ring can be easiest to pull out with a press. At this time, pay attention to making the inner ring bear its pulling force. Moreover, the pulling fixture shown is also mostly used, no matter what kind of fixture, it must be firmly clamped on the side of the inner ring. For this reason, it is necessary to consider the size of the shaft shoulder, or study the groove processing at the shoulder to use the drawing fixture.
The oil pressure method is used to disassemble the inner ring of large bearings. The oil pressure is set at the oil hole of the bearing to make it easy to draw. For bearings with large width, the oil pressure method is used together with the drawing fixture to disassemble.
The inner ring of cylindrical roller bearing can be disassembled by induction heating method. The method of drawing after local heating in a short time to expand the inner ring. The induction heating method is also used when a large number of such bearing inner rings need to be installed.
Bearing cleaning
When disassembling the bearing for inspection, first make appearance records by photography and other methods. In addition, confirm the amount of residual lubricant and sample the lubricant before cleaning the bearing.

  • a. The cleaning of bearings is divided into rough cleaning and fine cleaning, and a metal grid can be placed at the bottom of the used container.
  • b. During rough cleaning, use a brush in the oil to remove grease or adhesive. If the bearing is rotated in the oil at this time, be careful that the rolling surface will be damaged due to foreign matters.
  • c. During fine cleaning, rotate the bearing slowly in oil and carefully.

The commonly used cleaning agent is neutral diesel oil or kerosene without water, and sometimes warm lye is also used as required. No matter what kind of cleaning agent is used, it should be filtered frequently to keep it clean.
After cleaning, immediately coat the bearing with antirust oil or grease.
matters needing attention
From the perspective of use, the following points should be paid attention to to ensure that the bearing can work reliably:

  • 1. Improve lubrication quality, control oil pressure, temperature and flow, and strengthen oil filtration.
  • 2. Use fuel and lubricating oil that meet the requirements.
  • 3. It is unfavorable to control the temperature of diesel generator set and work under the condition of supercooling and overheating. In cold days, the diesel engine should be preheated before starting, and the crankshaft should be turned manually to make the oil enter the friction surface.
  • 4. The surface quality and geometric shape of bearing and journal shall be strictly guaranteed.
  • 5. The bearing clearance should be appropriate. If the generator set is too large, it will produce impact. If the generator set is too small, it will cause poor lubrication and may burn the pads.

How to ensure the reliable operation of bearings

In general, the following points should be noted from the perspective of use:

  • 1. The bearing clearance should be appropriate. If it is too large, the impact will occur. If it is too small, the lubrication will be poor and the bearing pad may burn;
  • 2. The surface quality and geometric shape of bearing and journal shall be strictly guaranteed;
  • 3. Improve the lubrication quality, control the pressure, temperature and flow of oil, and strengthen the oil filtration;
  • 4. Use fuel oil and lubricating oil that meet the requirements.

In order to give full play to the bearing and maintain its due performance for a long time, it is necessary to do a good job of regular maintenance (regular inspection). Through proper regular inspection, it is very important to find faults early and prevent accidents before they happen, which is very important to improve productivity and economy.

Troubleshooting of bearings

Causes of rolling bearing heating and its troubleshooting:

  • Low bearing accuracy: select bearings with specified accuracy level.
  • The main shaft is bent or the box hole is not concentric: repair the main shaft or box.
  • Poor lubrication: select the lubrication data of the specified brand and clean it properly.
  • Low assembly quality: improve assembly quality.
  • Running ring of bearing inner shell: replace the bearing and relevant wearing parts.
  • The axial force is too large: clean and adjust the seal ring clearance between 0.2-0.3mm, correct the impeller balance hole diameter and verify the static balance value.
  • Bearing damage: replace the bearing.

How to select the correct bearing manufacturer?

Selecting the correct bearing manufacturer usually requires consideration of the following factors:

  • Quality: Select a manufacturer with a good quality record, which will ensure that you get reliable bearings, thus extending their service life and reducing maintenance costs.
  • Reliability: select manufacturers with stable production and supply capacity to ensure that you can obtain the required bearings in time.
  • Technical support: Select a manufacturer that can provide technical support and solve problems to ensure that you get the best bearing performance.
  • Cost: select manufacturers with reasonable prices to ensure that your costs are within the budget.
  • Reputation: Select a reliable and well evaluated manufacturer, which will ensure that you get the best purchase experience.

Taking these factors into consideration, choose one that is consistent with your business needs and values bearing manufacturerIs critical.

PREV
NEXT

RELATED POSTS

Leave a Reply

*

*

Inquery now

SUBSCRIBE TO OUR NEWSLETTER

FOLLOW US

YouTube WhatsApp Skype

Telephone:
8618267732328
Wechat: 8618267732328
Wechat
Whatsapp

Email me
Mail to us
Skype