Technical repair method for NTN bearing

NTN bearings are mass-produced mechanical parts, and the manufacturing precision is very strict, and the degree of technical specialization is very high. Therefore, for most of the easy-to-buy bearing types, it should be more cost-effective to buy than in the following cases. Next, consider the bearing repair problem, namely:

(1) A large number of bearings of the same type used in large factories are mainly in the form of wear on the rolling surface, fatigue or fretting abrasion, especially the damaged parts are mostly cages or rolling elements, and the ferrules or gaskets are still repaired. value;

(2) Large and extra large bearings, which have no major damage to the parts due to failure or failure, or expensive NTN bearings must seek to extend their useful life;

(3) Some types of bearings that are really difficult to purchase, have no spare parts after failure and have to be repaired, especially imported bearings;

(4) The bearing has slight damage, such as slight rust generated during the inventory period, and slight fretting abrasion caused by transportation. It is a pity that such repair is easy and abandon.

In addition to economics, the repair of NTN bearings is technical, which requires the repairer to fully understand the corresponding technical requirements of the bearing, and the structural, technical and material characteristics of the bearing and its parts, otherwise it is difficult to guarantee the repair of the bearing. Have the desired effect.

In the business of repairing bearings, if the cooperation of professional bearing companies can be obtained, the following benefits may be obtained:

(1) The technical requirements of each process of repair can be clarified, and how to ensure the overall quality of the repaired bearings,

(2) It is possible to utilize many of the specialized experience of specialized bearing plants, which can reliably, efficiently and economically meet process requirements;

(3) It is possible to order a tool for a professional bearing company, which can be economical and saves a lot of trouble;

(4) Orders such as cages, rolling elements, rivets, etc. can be ordered from professional bearing companies, which may make the repair work simple, convenient and economical.

If the NTN bearing is mounted on the adapter sleeve, determine the direction of the housing. The nozzle tip of the housing cap should always be on the other side of the adapter nut. Care must be taken in the direction of the entire housing as the top cover and base must be installed in the original orientation.

1. Bearing installation and disassembly are sometimes involved; the movement of heavy objects, the use of tools and other equipment, or the use of high pressure oil.

2. Make sure the environment is clean.

3. Check the size and shape tolerances of the journal.

4. Check that the surface roughness Ra of the support surface is not more than 12.5 μm. The flatness tolerance should be IT7. For applications with lower requirements, IT8 is available.

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Detecting the quality of INA bearing lubricants from the noise used in lubrication

The three simplest detection methods for lubricating oil are: oil spot method, color discrimination method and honing method.

Oil spot method:

The oil to be inspected is evenly mixed and dropped on a white paper (preferably a filter paper) to form oil spots, and the oil spots gradually diffuse from the center outward for about 2 to 3 hours to form three concentric rings. The state of the oil can be discerned based on the color, width and shape of the three areas.

Color discrimination method:

Normal is brown and blue black. If it is milky yellow, it indicates that diesel oil or water is added to the oil and should be replaced in time. If it is dark black, it indicates that the oil has deteriorated and must be replaced in time.

Honing method:

Remove a little oil from the low shell of the oil, apply it on your fingers, and rub it with your fingers and thumb. If you feel that there is impurities in the oil or that it is not sticky like water, or even hairy or sour, the oil has deteriorated. If you can see a small shiny metal grinding on your finger after honing, it means that the engine has a serious wear part, and it also means that the oil must be replaced immediately.

1. Low temperature high speed bearing grease

At present, the equipment using INA bearings is becoming more and more refined, and the grease used for bearings must have the following properties:

(1) It has the same operating life as the bearing, prolongs the maintenance cycle, shortens downtime and improves labor productivity.

(2) Under the high speed of dn>5×105, it is necessary to ensure that the motor temperature rises low and does not lick oil, thus reducing power consumption and protecting the motor.

(3) The impurity content is controlled under certain standards to minimize the pollution of equipment noise to the environment.

(4) Guarantee the flexibility of starting and running the bearing under ultra-low temperature working conditions to ensure the minimum output power.

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FAG thrust ball bearing fault maintenance precautions

Thrust ball bearing fault characteristics show severe faults (usually, such as bearing damage, burns, sand cracking, raceways, beading, etc.) no more than a week old, equipment, capacity is larger, faster, and more Short time interval. Therefore, the actual FAG bearing fault diagnosis, once the fault is discovered, its advanced function, should determine the bearing fault decisively and repair as soon as possible.

1. Selection and control of shaft and bearing chamber tolerance: After the bearing is pressed into the thrust ball bearing, it should be flexible and unobstructed. If the obvious rotation is not flexible, it means that the size of the shaft is too large and the tolerance is lowered. If the bearing is pressed into the shaft and turned by hand, there is a clear "sand" feeling, which may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. Therefore, it is necessary to control the roundness when controlling the tolerance of the shaft and the bearing chamber. At present, many domestic manufacturers only control the tolerance and do not control the roundness.

2, the assembly of the bearing: Because the bearing is a high-precision product, such as improper assembly can easily damage the bearing channel, resulting in bearing damage. The FAG bearing should have a special mold during assembly. It can't be beaten at will. When pressing the shaft, it can only be pressed in a small circle. When pressing a large circle, it can only be subjected to a large circle. Air pressure or hydraulic pressure is required for assembly. The upper and lower molds should be outside the horizontal state during press-fit. If tilted, the thrust ball bearing channel will be damaged due to the force, which will cause the bearing to produce a sound.

3. Prevention of assembly of foreign objects: When the bearing is mounted on the rotor to make dynamic balance, it is easy to enter the iron filings generated during dynamic balancing into the bearing. Therefore, it is better to balance the load before loading the bearing. Some manufacturers have some oil or grease to lubricate the bearing chamber during assembly. However, it is often difficult for the operator to control the amount. If the oil or grease accumulates in the bearing chamber, the FAG bearing rotates. It is easy to enter the inside of the thrust ball bearing along the shaft. It is best not to apply oil or grease to the bearing chamber. If it is not painted, it must be controlled not to accumulate in the bearing chamber.

4, the prevention of paint rust: paint rust is characterized by multiple seals in the motor, the motor sounds very good when assembled, but after putting some time in the warehouse, the motor noise is very large, the bearing is removed Severe rust. In the past, many manufacturers thought that it was a bearing problem. After our constant publicity, the motor factory has now realized that it is mainly a problem of insulating varnish. This problem is mainly caused by the fact that the acidic substance volatilized by the insulating paint forms a corrosive substance under a certain temperature and humidity, and the bearing of the thrust ball bearing is corroded and causes the bearing to be damaged. The problem can only be achieved by selecting a good insulating varnish and venting it after drying for a while.

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Precautions for using grease in FAG cylindrical roller bearings

Lubricating this process is indispensable during the use of FAG bearings. However, there are many ways to lubricate. Various lubrication methods should pay attention to different problems during the lubrication process, which leads to the user's Confused, here I will introduce you to the precautions for cylindrical roller bearing oil lubrication and grease.

1, grease lubrication

Relubrication of cylindrical roller bearings is best carried out during planned equipment downtime and is periodically replenished, while removing old grease or extruding old grease through the drain. Wipe the grease fittings clean before adding fresh grease. If the FAG bearing housing does not have a grease fitting, the bearing housing cover or end cap should be opened to remove the old grease and, after cleaning, replenish the same type of fresh grease.

2, lubricating oil lubrication

Regularly check the oil level and oil quality of the lubricating oil. Under normal circumstances, the normal oil level should be within the range of 1/3-2/3 of the equipment oil level window or mark. The oil filling method is oil cup, the oil level shown only represents the oil replenishing capacity, and the oil level of the cylindrical roller bearing housing is to meet the operation requirements. The oil level in the oil cup is less than 1/4 of its total volume. .

Check and replenish the oil method, take a small amount of lubricating oil as a sample and compare it with fresh oil. The competent unit can consider the oil quality test to ensure the oil quality is qualified. If the sample looks cloudy, it may be the result of mixing with water, which is commonly referred to as oil emulsification. At this point, the lubricant should be replaced.

If the sample is darkened or thickened, it may indicate that the lubricant has begun to carbonize and the old lubricant should be completely replaced. If possible, flush the oil line with fresh oil. When changing the lubricating oil, make sure that the new and old models of the replaced oil are the same and supplement the required oil level.

The grease used in the FAG bearing must have an anti-rust effect, and the anti-rust agent is preferably insoluble in water. Grease should have good adhesion to form an oil film on the surface of the steel, even if the grease is filled with water. Grease becomes soft during machining and causes leakage. When there is a vibration application example, the grease will be smashed into the bearing by the cylindrical roller bearing housing. If the mechanical stability of the grease is insufficient, the grease will be continuously thrown out of the bearing, which will cause mechanical collapse of the soap structure and destruction of the grease.

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Nine common causes of bearing failure

It is not uncommon for the bearing to malfunction during operation, so there is no need to make a fuss. A failure has occurred and it is critical to judge and deal with it. Today we will explain the reasons for the common failure of FAG bearings.

The reasons for the bearing temperature being too high are: the quality of the lubricating oil does not meet the requirements or deteriorates, the viscosity of the lubricating oil is too high; the assembly of the mechanism is too tight (the gap is insufficient); the bearing assembly is too tight; the bearing race rotates on the shaft or inside the casing; Large; bearing cage or rolling body fragmentation.

1. The raceway of the raceway is seriously worn: it may be that foreign objects fall into the raceway, the lubricant is insufficient or the lubricant grade is not suitable.

2. The bearing temperature is too high: When the mechanism is running, the part where the bearing is installed is allowed to have a certain temperature. When the structure of the mechanism is touched by hand, it should be normal to not feel hot, otherwise the bearing temperature is too high.

3. The cage is broken: the reason is insufficient lubrication, broken rolling elements, and skewed seat.

4. Bearing noise: The rolling bearing is allowed to have a slight running noise during operation. If the sound is too loud or there is abnormal noise or impact sound, it indicates that the bearing is faulty.

5. Plastic deformation: uneven pits appear on the contact surface between the raceway and the roller of the bearing, indicating that the bearing is plastically deformed. The reason for this is that under a large static load or impact load, the local stress of the working surface exceeds the yield limit of the material, which generally occurs on bearings rotating at low speed.

6, bearing burns: burned bearings have tempering color on the raceway and rolling elements. The causes of burns are generally insufficient lubrication, the quality of the lubricant does not meet the requirements or deterioration, and the bearing assembly is too tight.

7. Metal surface spalling on the raceway surface: The bearing rolling elements and the inner and outer ring raceways are subjected to periodic pulsating loads, thereby generating cyclically varying contact stresses. When the number of stress cycles reaches a certain value, fatigue peeling occurs on the rolling element or the inner and outer ring raceways. If the bearing load is too large, this fatigue will be exacerbated. In addition, the bearing is not installed correctly, the shaft is bent, and the raceway is peeled off. Fatigue spalling of the bearing races reduces the accuracy of the shaft and causes vibration and noise in the mechanism.

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Analysis: NSK bearing cleaning installation precautions

(1) When cleaning a large number of NSK bearings, first use hot oil with a temperature of 90-100 °C to melt the encapsulating oil. At the same time, use a seamless and non-dusting tool to dig all the old oil and then boil for a few minutes. Then rinse the oil with kerosene and finally wash it with gasoline. After cleaning and cleaning, the NSK bearing should be put on a clean cloth on the workbench or on the paper to dry.

(2) Before the installation of the NSK bearing, the machining quality of the shaft and the seat hole and related parts (such as dimensional accuracy, shape accuracy and surface roughness) should be checked with appropriate measuring tools according to the technical requirements on the design drawings.

(3) Open the NSK bearing package at the time of installation, immerse it in the above-mentioned gasoline and other liquids to gently rotate the hand, and ensure that the cage, the rolling element and the surface of the raceway are thoroughly cleaned.

(4) The surface of the assembly should be cleaned with a clean solution of gasoline, kerosene, toluene or xylene, and dried with a clean rag, and then coated with a thin layer of lubricant, which makes the installation operation more convenient.

(5) Note that the sealed NSK bearing can not be cleaned by this method, and the inside of the seal should be kept as it is.

(6) If there are bumps, burrs, rust spots or solid particles (such as wear debris, sand, dirt) on the assembly surface of the shaft and the bearing housing hole, it will not only make the NSK bearing difficult to install and the installation position is incorrect, but also If the solid particles fall into the NSK bearing, it will act as a grinding. When the NSK bearing rotates, it will wear or scratch the working surface of the NSK bearing. Therefore, it must be carefully inspected before installation. If any defects are found, they should be corrected. . For example, oil mites are used to remove burrs, bumps, rust spots, and light sanding, such as cleaning solid particles, dirt, and the like.

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Anti-friction SKF bearing type and lubrication function

Anti-friction SKF bearings are divided into two main types. They are ball SKF bearings and roller SKF bearings. At the same time, we also know that due to the different uses of the manufacturer and SKF bearings, many different types have evolved according to these basic structures.

Lubrication function, anti-friction lubricant has the following main functions

1. Lubricate the sliding contact between the retainer and the rest of the SKF bearing.

2. Lubricate any contacts between the race and the roller that is not actually rolling.

3. Lubricate the sliding contact between the roller and the guide in the roller type SKF bearing.

4. Lubricate all true rolling contacts in SKF bearings.

The secondary features are:

5. Protect the highly delicate surface from corrosion.

6. Assist the sealing cover to protect against foreign substances. Grease has this function.

7. Provide a means of conducting heat (cold).

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Rolling mill NSK bearing lubrication method

First, the lubrication method

The lubrication of the roller NSK bearing is basically the same as that of other rolling NSK bearings. However, the working condition of the roller NSK bearing is relatively bad, and whether the working performance can be effectively exerted depends largely on the lubrication condition of the NSK bearing.

The lubrication methods used for roll NSK bearings are mainly grease lubrication and oil lubrication.

The grease-lubricated grease has a sealing function, the sealing structure and the lubrication facility are simple, and the grease is convenient to be replenished. Therefore, as long as the working conditions permit, the roller NSK bearing is generally grease-lubricated.

The oil lubrication has a strong cooling effect and can remove dirt and moisture from the NSK bearing. Roll NSK bearings use oil-lubricated lubrication methods such as pressure oil lubrication, fuel injection lubrication, oil mist lubrication and oil and gas lubrication.

Pressure oil lubrication is the most effective lubrication method for roll NSK bearings at normal speed.

Injection lubrication is to lubricate the lubricant to the inside of the NSK bearing through a nozzle mounted on the NSK bearing side at a certain pressure. It is generally used in high-speed roll NSK bearings, or where the pressure supply lubrication cannot meet the cooling requirements.

Spray lubrication is to spray the dry compressed air containing oil mist into the NSK bearing for lubrication. The use of less oil, due to the action of air, the cooling effect is very strong, mainly used for large rolls NSK with high rolling speed and high rolling precision. Bearings, or NSK bearings for rolls that are not frequently removed in NSK bearing housings.

Pressure oil lubrication and fuel injection lubrication require the installation of inlet and outlet pipes, lubrication pumps, oil reservoirs, and sometimes oil coolers. Therefore, the cost is high, and NSK bearings are generally used less.

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