Common sliding NSK bearing failures

Sliding NSK bearings NSK bearings that work under sliding friction. The sliding NSK bearing works smoothly, reliably and without noise. Under liquid lubrication conditions, the sliding surface is separated by the lubricating oil without direct contact, and the friction loss and surface wear can be greatly reduced, and the oil film also has a certain vibration absorbing capability. The use of sliding NSK bearings is also very versatile. How can we solve the problem of the occurrence of sliding NSK bearings? What better way? Let me explain the relevant knowledge to you, I hope to help you.
Common faults in sliding NSK bearings are as follows:
1, tile surface corrosion: spectral analysis found that the concentration of non-ferrous metal elements is abnormal; there are many sub-micron wear particles of non-ferrous metal components in the iron spectrum; lubricating oil moisture exceeds the standard, acid value exceeds the standard.
2. NSK imported bearing journal surface strain: iron spectrum cutting abrasive grains or black oxide particles in the iron spectrum, tempering color on the metal surface.
3, NSK bearing journal surface corrosion: Spectral analysis found that the concentration of iron is abnormal, there are many sub-micron particles of iron in the iron spectrum, the lubricating oil exceeds the standard or the acid value exceeds the standard.
4, NSK bearing surface strain: found in the iron spectrum cutting abrasive particles, abrasive particles are non-ferrous metals.
5, fretting wear behind the tile: spectral analysis found that the iron concentration is abnormal, there are many iron components in the iron spectrum sub-micron wear particles, lubricating oil moisture and acid value is abnormal.

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Calculation method of rolling bearing fault frequency

Rolling bearing outer ring fault frequency: BPFOr≌0.4Nn
Rolling bearing inner ring fault frequency: BPFIr≌0.6Nn
Rolling bearing cage failure frequency: FTFr≌0.4N

The above symbols:

n = number of rolling elements.
N = speed of the shaft.

Note: 1. The rolling bearing does not slide; 2. The rolling bearing geometry does not change; 3. The bearing outer ring is fixed and does not rotate.

Rolling bearing outer ring fault frequency: BPFOe≌N (0.5n-1.2)
Rolling bearing inner ring fault frequency: BPFIe≌N (0.5n+1.2)
Rolling bearing rolling element failure frequency: BSFe≌N (0.2n-1.2/n)
Rolling bearing cage failure frequency: FTFe≌N (0.5-1.2/n)

The above symbols:

n = number of rolling elements.
N = speed of the shaft.

Note: 1. The rolling bearing does not slide; 2. The rolling bearing geometry does not change; 3. The bearing outer ring is fixed and does not rotate.

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How to choose oil according to the Dn value of the rolling bearing

The recommended oil viscosity according to dn value / temperature is as follows:

Dn value <10000mm.r/min, oil viscosity 60mm2/s for bearing working temperature 0-30°C, suitable oil 37.8°C viscosity 115mm2/s at 30-60°C, suitable viscosity 37.8°C at 60-90°C 360mm2 / s, suitable oil at 90-120 ° C 37.8 ° C viscosity 750mm2 / s;

The dn value is 10000-25000mm.r/min, the oil viscosity is 35mm2/s when the bearing working temperature is 0-30°C, the applicable oil is 37.8°C viscosity 95mm2/s at 30-60°C, and the applicable oil is 37.8°C at 60-90°C. Viscosity 270mm2 / s, suitable oil at 90-120 ° C 37.8 ° C viscosity 550mm2 / s;

The dn value is 25000-60000mm.r/min, the oil viscosity is 35mm2/s when the bearing working temperature is 0-30°C, the applicable oil is 37.8°C viscosity 70mm2/s at 30-60°C, and the applicable oil is 37.8°C at 60-90°C. Viscosity 270mm2 / s, suitable oil at 90-120 ° C 37.8 ° C viscosity 550mm2 / s;

Dn value is 60000-75000mm.r/min, oil viscosity is 20mm2/s when bearing working temperature is 0-30°C, suitable viscosity is 37.8°C 60mm2/s at 30-60°C, and suitable oil is 37.8°C at 60-90°C Viscosity 220mm2 / s, suitable oil at 90-120 ° C 37.8 ° C viscosity 360mm2 / s;

Dn value is 75000-100000mm.r/min, oil viscosity is 20mm2/s when bearing working temperature is 0-30°C, viscosity is 60wt2/s at 30-60°C, viscosity is 60mm2/s at 60-90°C, and suitable oil is 37.8°C at 60-90°C Viscosity 160mm2 / s, suitable oil at 30-120 ° C 37.8 ° C viscosity 3600mm2 / s;

Dn value 100000-250000mm.r/min, oil viscosity 9mm2/s for bearing working temperature 0-30°C, 37.8°C viscosity 35mm2/s for 30-60°C, 37.8°C for oil at 60-90°C Viscosity 115mm2 / s, suitable oil at 90-120 ° C 37.8 ° C viscosity 270mm2 / s;

Dn value is more than 250,000 mm.r/min, oil viscosity is 9mm2/s when the bearing working temperature is 0-30°C, 37.8°C viscosity is 35mm2/s at 30-60°C, and suitable oil is 37.8°C at 60-90°C. The viscosity is 95 mm 2 /s, and the applicable oil at 90-120 ° C is 37.8 ° C viscosity 270 mm 2 / s.

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How to maintain the water pump bearing

(1) The pump that is newly put into use must be replaced with grease (oil) after 100 hours of operation, and then replaced once every 500 hours.

     (2) Lubricating grease-lubricated flow bearings should be replaced after 1500 hours of operation. The amount of oil to be filled should not be too much or too little, because too much or too little grease will cause the bearing to heat up. It is preferably 1/2 to 2/3 of the volume of the bearing chamber.

     (3) For bearings lubricated with lubricating oil, the amount of oil should be added to the specified position.

     (4) The container containing lubricating oil or grease should be clean and should be sealed properly. There should be no dust, iron filings and other debris to avoid damage to the bearing.

     (5) Motor bearings generally use sodium-based grease, which is characterized by high temperature resistance (125 ° C), but is easily soluble in water, so it can not be used for lubrication of water pump bearings.

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Inspection, maintenance and maintenance of wheel bearings

Hub bearings are important moving parts for automobiles. The hub axle bears the burden of reducing the frictional resistance during the operation of the chassis and maintaining the normal driving of the car. If the hub bearing fails, it may cause noise, bearing heat, etc., especially the front wheel is more obvious, which may lead to dangerous phenomena such as out of control. Therefore, the hub bearings must be maintained on schedule.

1. Inspection of the hub bearing

(1) When checking the tightness of the hub bearing, firstly, the axle of the wheel at one end of the wheel of the car to be inspected is erected, and the vehicle is safely framed by means of a vehicle stool, a wooden cover, and the like.

(2) Turn the number of wheels to be inspected by hand to see if the rotation is stable and there is abnormal noise. If the rotation is not smooth and there is friction, the brake part is not normal; if there is no noise, the rotation is not smooth and it is loose when it is tight, indicating that the bearing part is not normal. The hub should be removed when the above abnormality occurs. For small cars, when inspecting the hub bearings, hold the upper and lower sides of the tires with both hands, and pull the tires back and forth with both hands and repeat them many times. If it is normal, there should be no feeling of looseness and blockage; if the swing has a feeling of looseness, the wheel should be removed.

(3) Inspection of the brakes. Usually when inspecting the hub bearing, check the wheel brake device. If there is oil on the inside of the tire, it may be caused by oil leakage from the brake cylinder or brake hose. The cause should be identified and eliminated.

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Surface treatment of bearings with diamond coating reduces loss

Bearings are a universal part, and only a few equipments do not use bearing designs. In most cases, bearings are found in all types of instruments and equipment systems. Surface treatment of ball and plain bearings with a diamond-type coating can greatly reduce the frictional losses of the bearing system. In advance, this diamond-type coating can be applied to plastic bearings through a special coating process to improve the durability of components and extend the life of the equipment.

    Ball bearings are often seen in the transmission section of bicycles, while plain bearings can be found in the shaft of a ship. Bearings play a vital role in many drive and brake designs. They not only work well under high-speed engines and high-heat composite conditions, but also help materials meet the requirements of some extremely demanding working environments. Diamond-type coatings The emergence of the application is very good.

    Scientists from the IWM Materials Performance Research Center in Freiburg, Germany, are actively developing new generations of bearings for the next generation. They have developed a special high-performance chemical coating for the bearings to provide a smooth surface in the bearing. Degree, reduce friction, so as to achieve the design requirements to extend the purpose of bearing use. These innovative coating products, mainly composed of diamond-type carbon (DLC), said Dr. Sven Meier, head of the research center, "The emergence of diamond-based coatings has given us a strong technology for future bearing design. Support. We are fully capable of designing new products that last longer than conventional bearings. The bearing technology and applications for this new coating are still under development, and we envisage that this product can be used without lubricants. The situation can be done well."

    Of course, the surface treatment of diamond coatings on bearings also requires special coating processes, and IWM scientists have also completed the development of this process. Meier went on to say, “Our coating method can be used for surface treatment of complex geometric components such as bearing cages.” Engineers are currently optimizing this technology to achieve low-coat thickness performance. Application requirements, it is reported that IWM plans to control the coating thickness below 20 microns. “Our process ensures the coating service requirements for micron-sized coating structures. At this size, the coating can completely replace traditional lubricants or lubricants to minimize system friction. Special requirements can also create super smooth material surfaces."

    Currently, researchers are further developing coating coating processes to ensure they meet the specific requirements of different sizes and shapes. IWM's goal is to reduce the high cost of existing bearing processing by optimizing the process, thereby reducing the cost of enterprise equipment procurement and equipment maintenance.

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Lubrication of plain bearings

Lubricant

The role of the lubricant is to reduce frictional resistance, reduce wear, cooling and vibration absorption. Lubricants are liquid, solid and gas and semi-solid. Liquid lubricants are called lubricating oils, semi-solid, at room temperature. The grease is grease.

Lubricant

Lubricating oil is the main lubricant. The main physical property index of lubricating oil is viscosity. Viscosity characterizes the internal friction property of liquid flow. The greater the viscosity, the worse the fluidity. Another physical property of the lubricating oil is oiliness, which characterizes the adsorption capacity of the lubricating oil on the metal surface. The greater the oiliness, the stronger the adsorption capacity for the metal, and the easier the oil film is formed. The choice of lubricating oil should take into account factors such as bearing capacity, journal rotation speed, lubrication method, and surface roughness of sliding bearings.
The general principles are as follows:

1. Under high-speed and light-load working conditions, in order to reduce frictional power consumption, a lubricant with a small viscosity can be selected;
2. Under heavy or shock load working conditions, oil with large oiliness and high viscosity should be used to form a stable lubricating film;
3, static pressure or dynamic and static pressure sliding bearings can choose a small viscosity lubricant;
4. Surfaces with rough or unrunned surfaces should be selected with high viscosity lubricants.

The selection of the viscosity of the lubricating oil for hydrodynamically lubricated bearings can be checked by calculation.

Grease

For plain bearings with a journal speed of less than 1 m/s to 2 m/s, grease can be used. The grease is blended with mineral oil, various thickeners (such as calcium, sodium, lithium, aluminum and other metal soaps) and water. The grease has a large consistency (needle penetration) and a large carrying capacity, but its physical and chemical properties are unstable. It should not be used under conditions of large temperature changes, and is often used in low-speed heavy-duty or oscillating bearings.
Solid lubricants and gas lubricants

Solid lubricants include graphite, molybdenum disulfide (MoS2) and polytetrafluoroethylene (PTFE). Generally used under heavy load conditions or under high temperature working conditions. Gas lubricants are commonly used in air, and are used at high speeds and in oils or greases.

Lubrication method

Providing lubricant to the bearing is a necessary condition for forming a lubricating film. The hydrostatic bearing and the hydrostatic bearing continuously supply oil to the bearing bush of the sliding bearing through the oil pump, the throttle and the oil groove, and form an oil film to separate the bearing bush from the journal surface. The oil film of the dynamic pressure sliding bearing is to bring the lubricating oil into the bearing gap by the rotation of the journal, and the oil supply mode includes continuous oil supply and intermittent oil supply.

Intermittent oil supply:

Intermittent oil supply can be oiled by the oil pot and the needle valve can be used to fill the oil through the oil cup. The grease lubrication can only be used intermittently.

Press-fit injection oil cup

Needle valve type oil cup
Continuous oil supply:

Core oil supply oil ring oil supply

Pressure supply
Selection principle:

The lubrication method of the sliding bearing can be determined according to the coefficient k

In the formula:
p=F/(dB)--average pressure (MPa);
V-- journal speed (m/s).
K≤2--lubricated, oil cup lubrication;
k=2—16--needle valve type oil cup lubrication;
k=16-32 oil ring or splash lubrication;
K≥32--pressure cycle lubrication.

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INA rolling bearing installation Common problems

First, how to choose grease?
Lubrication has a very important influence on the operation and life of the INA bearing. Here is a brief overview of the general principles for selecting grease. Grease is made of base oil, thickener and additives. The grease performance of different types and different grades varies greatly. The allowable rotation limit is different. Be careful when selecting. The performance of grease is mainly determined by the base oil. Generally, the low viscosity base oil is suitable for low temperature, high speed and high viscosity for high temperature and high load. The thickener is also related to the lubricating properties, and the water resistance of the thickener determines the water resistance of the grease. In principle, the different greases of the brand cannot be mixed, and even the grease of the same thickener may have a bad influence on each other due to the different additives.
Second, must the bearings be cleaned before installation?
The surface of the bearing is coated with anti-rust oil. You must clean it with clean gasoline or kerosene, and then apply it with clean high-quality or high-speed high-temperature grease. The effect of cleanliness on rolling bearing life and vibration noise is very large. But we must remind you that the fully enclosed bearings do not need to be cleaned and refueled.
Third, how to install and disassemble?
Do not directly hammer the INA bearing end face and the non-stress surface during installation. The bearing should be evenly stressed by the clamp, sleeve or other installation tools (tooling). Do not install by the rolling element transmission force. If the mounting surface is coated with oil, it will make the installation smoother. If the interference is large, the bearing should be placed in mineral oil and heated to 80~90 °C and installed as soon as possible. Strictly control the oil temperature not to exceed 100 °C to prevent the tempering effect from decreasing and affecting dimensional recovery. When disassembling is difficult, it is recommended that you use the disassembly tool to pull outward while carefully pouring hot oil onto the inner ring. The heat will cause the inner ring of the rolling bearing to expand, making it easier to fall off.
4. What are the requirements for the installation surface and installation site?
  Yes. If there are foreign objects such as iron filings, burrs, dust, etc. in the INA bearing, the bearings will generate noise and vibration during operation, and even damage the raceway and rolling elements. Therefore, before installing the bearings, you must ensure that the mounting surface and the installation environment are clean.
5. When lubricating the bearings, the more grease is applied, the better?
When lubricating INA bearings, the more grease is applied, the better. This is a common misconception. Excessive grease in the bearing and bearing chambers will cause excessive agitation of the grease, resulting in extremely high temperatures. The amount of lubricant filled in the rolling bearing is preferably 1/2 to 1/3 of the internal space of the bearing, and should be reduced to 1/3 at high speed.
6. Is the radial clearance of the bearing as small as possible?
Not all INA bearings require a minimum working clearance and you must select the appropriate clearance depending on the conditions. In GB 4604-93, the radial clearance of rolling bearings is divided into five groups - 2 groups, 0 groups, 3 groups, 4 groups, 5 groups. The clearance values ​​are from small to large, and 0 is the standard clearance. The basic radial clearance group is suitable for general operating conditions, conventional temperature and common interference fit; rolling bearings with special conditions such as high temperature, high speed, low noise and low friction should use large radial clearance; Small radial clearance should be used for precision spindles and bearings for machine tool spindles; a small amount of working clearance can be maintained for roller bearings. In addition, there is no so-called clearance for the separate type of bearing; finally, the working clearance after the bearing is installed is smaller than the original clearance before installation, because the bearing is subject to a certain load rotation, and the INA bearing fit and load are generated. The amount of elastic deformation.
After the bearing is installed, check the operation in order to check if the installation is correct. The small machine can be rotated by hand to confirm whether the rotation is smooth. The inspection items have poor operation due to foreign matter, scratches, and indentations. The installation is poor, the torque generated by the mounting is not stable, and the torque is too large due to too small clearance, installation error, and sealing friction. Wait. If there is no abnormality, the power running can be started.
The power running starts from the no-load low speed and slowly increases to the rated operation of the specified conditions. The items to be checked during the test run are whether there is abnormal sound, INA bearing temperature change, lubricant leakage or discoloration, etc. If an abnormality is found, stop the operation immediately, check the machine, and remove the bearing check if necessary.
The bearing temperature can generally be estimated based on the external temperature of the bearing housing. However, it is more accurate to directly measure the temperature of the outer ring of the bearing by using the oil hole. The rolling bearing temperature gradually increases from the start of the operation, and the temperature is usually stable after 1 to 2 hours. If the bearing is poorly installed, the temperature will rise sharply and an abnormally high temperature will occur. The reasons are such as excessive lubricant, too small INA bearing clearance, poor installation, excessive friction of the sealing device, and the like.
The rotation of the INA bearing is checked with a stethoscope, etc., and there are strong metal noise, abnormal sounds, irregular sounds, etc. to explain abnormalities. The reasons are poor lubrication, poor accuracy of the shaft or housing, bearing damage, and foreign matter intrusion.
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Slewing bearing model and features

1. Single row four point contact ball type slewing ring (01 series)

The single-row four-point contact ball slewing ring consists of two races. It is compact and lightweight. The steel ball is in contact with the arc track at four points and can withstand axial force, radial force and tipping moment. Construction machinery such as rotary conveyors, welding operators, small and medium-sized cranes and excavators are available.

2, double row ball slewing ring (02 series)

The double volleyball slewing bearing has three races. The steel ball and the spacer block can be directly discharged into the upper and lower raceways. According to the force condition, two rows of steel balls with different diameters are arranged. This open assembly is very convenient, the upper and lower circular races have a bearing angle of 90° and can withstand large axial forces and tipping moments. The axial and radial dimensions of the bearing are relatively large and the structure is fastened. It is especially suitable for loading and unloading machines such as tower cranes and truck cranes that require medium and large diameters.

3. Single row cross roller type slewing ring (11 series)

Single row cross roller type slewing ring consists of two races. It is compact in structure, light in weight, high in manufacturing precision, small in assembly clearance, high in installation accuracy, and 1:1 cross-arrangement of rollers. Force, tipping moment and large radial force are widely used in hoisting transport, construction machinery and military products.

4, three rows of roller slewing bearings (13 series)

The three-row roller type slewing bearing has three races, and the upper and lower and the radial raceways are separated, so that the load of each row of rollers can be accurately determined. It can withstand various loads at the same time. It is the most load-bearing type among the four products. It has large shaft and radial dimensions and is firm in structure. It is especially suitable for heavy machinery requiring large diameter, such as bucket wheel excavator and wheel. Cranes, marine cranes, port cranes, steel running tables and large tonnage truck cranes.
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Slewing bearing model and features

1, light series slewing ring

The lightweight slewing bearing (including the thin-walled flanged turntable) has the same structure as the ordinary slewing bearing, and is light in weight and flexible in rotation. Widely used in food machinery, filling machinery, trailer trailers, environmental protection machinery and other fields.

2, single row four point contact ball slewing bearing (HS series)

The single-row four-point contact ball slewing ring consists of two races, which is compact and has four points of contact between the steel ball and the circular raceway. It is mainly used in machinery such as truck cranes, tower cranes, excavators, pile drivers, engineering work vehicles, radar scanning equipment, etc., which are subjected to tipping moment, vertical axial force and horizontal tendency force.

3, single row cross roller type slewing ring (HJ series)

Single row cross roller type slewing ring, consisting of two races, compact structure, high manufacturing precision, small assembly clearance, high requirements for installation accuracy, roller 1:1 cross arrangement, can simultaneously withstand axial force, tilt Rolling torque and large radial force are widely used in lifting and transportation, construction machinery and military products.

4, other series of slewing bearings

Single row four point contact ball slewing ring (QU, QW, QN series)

Four-point contact slewing ring (VL series)

Four-point contact slewing ring (VS series)

Four-point contact slewing ring (V series)

Single row cross roller slewing ring (XS series)

Single row cross roller slewing ring (X series)
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Four methods for identifying the quality of stone purchase

Stone engraving machine stone purchase quality good or bad four identification methods

For finished finished stone, the quality can be identified from the following four aspects:

One view, that is, the surface structure of the stone is observed by the naked eye.

In general, the uniform fine material structure of the stone has a delicate texture, which is a good stone; the coarse grain and the unequal grain structure of the stone have a poor appearance. In addition, due to the influence of geological effects, the stone often produces some fine cracks in it, and the stone is most likely to rupture along these parts, and should be removed. As for the lack of edges and corners, it is more important to affect the appearance, especially when choosing.

The second quantity, that is, the size specification of the stone, so as not to affect the splicing, or cause the pattern, pattern and line deformation after splicing, affecting the decorative effect.

Three listening, that is, listening to the sound of the stone

In general, the sound of a good quality stone is crisp and pleasing; on the contrary, if there is a slight crack inside the stone or the contact between the particles becomes loose due to weathering, the knocking sound is rough.

Four tests, that is, using a simple test method to check the quality of the stone