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Bearing application of 8 key knowledge points

Time:2019-04-04 17:01:05Hits:1033
1. Bearing installation 2. Bearing material 3. Bearing storage 4. Bearing maintenance 5. Adjustment of bearing axial clearance 6. Bearing damage and countermeasures 7. Bearing form 8. Measure the bearing radial clearance should pay attention to mat

1. Bearing installation

Whether the bearing is installed correctly affects accuracy, life and performance. Therefore, the design and assembly department should fully study the installation of the bearings and install them according to the operating standards. The items of the job standard are usually as follows:

(1) Cleaning bearings and bearing related parts

(2) Check the size and finishing of the connected parts

(3) Installation

(4) Inspection after mounting the bearing

(5) Supply lubricant

 

Open the bearing package before installation. Generally grease is lubricated, not cleaned, and directly filled with grease. Lubricating oil is not necessary for cleaning. However, for instruments or high-speed bearings, it should be cleaned with clean oil to remove the rust inhibitor applied to the bearing. The bearing with the rust preventive removed is easy to rust, so it cannot be placed.

 

Furthermore, bearings that have been sealed with grease are used without cleaning. The mounting method of the bearing varies depending on the bearing structure, fit, and conditions. Generally, since the shaft is mostly rotated, the inner ring needs an interference fit. Cylindrical bore bearings, press with multiple presses, or use hot charging methods. For taper holes, mount directly on the taper shaft or with a sleeve.

 

When installed in the outer casing, the general clearance fits a lot, and the outer ring has an interference amount, which is usually pressed by a press or a cold shrink fit method after cooling. When dry ice is used as the coolant and the shrinkage is installed, the moisture in the air will condense on the surface of the bearing. Therefore, appropriate rust prevention measures are required.

 

2. Bearing material

As the core component of the rotation, the bearing repeatedly withstands high-intensity contact pressure during operation and is accompanied by sliding contact. Therefore, there are strict standards for the bearing ferrule, the rolling element and the steel material of the cage:

 

Ferrules and rolling elements are usually made of high carbon chromium bearing steel. Most of the bearings use SUJ2 in JIS steel grades. Large bearings use SUJ3. The chemical composition of SUJ2 has been standardized as a bearing material in various countries around the world. For example, it is the same kind of steel as AISL52100 (USA) and DIN100Cr6 (West Germany).

 

 Further, when impact resistance is required, chrome steel, chrome molybdenum steel, nickel chrome molybdenum steel, and carburizing quenching are used as bearing materials to provide a hardened layer of steel from the surface to an appropriate depth. A carburized bearing having a suitable hardening depth, a fine structure, a surface having a suitable hardness, and a core hardness has superior impact resistance than a bearing using a bearing steel, and a chemical composition of a general carburized bearing steel. Some imported bearing steels will be vacuum degassed, so the materials used are high in purity, low in oxygen content and good in quality. Further, an appropriate heat treatment is employed to significantly increase the rolling fatigue life of the bearing.

 

In addition to the above-mentioned steel grades, high-speed steel excellent in heat resistance and stainless steel excellent in corrosion resistance are used depending on the specific use. Cage material: The material of the stamping cage, using low carbon steel. Brass plates and stainless steel plates are also used depending on the application. The material of the cage is cut, using high-strength brass, carbon steel, and synthetic resin.

 

3. Bearing storage

The bearing should be fully considered in consideration of the size and weight of the bearings to be stored, and the necessary handling space and equipment should be considered to ensure that the bearings are not collided when stored and taken. Do not place the bearings directly on the ground. Therefore, the appropriate shelf should be configured and the bottom of the shelf should be 30 cm above the ground. In the general packaging state, depending on the storage environment, the rust prevention effect is 13 years. In special cases where it is necessary to store for nearly 10 years, it can be stored in oil such as turbine oil (as a bearing lubricant).

 

4. Bearing maintenance

In order to fully utilize the bearings and maintain their proper performance for a long time, regular maintenance must be carried out. Through proper periodic inspections, early detection of failures and prevention of accidents are important to improve productivity and economy.

 

(1) Cleaning:

 

When the bearing is removed and inspected, the appearance record is first recorded by photography. Also check the amount of lubricant remaining and sample the lubricant before cleaning the bearings.

 

The cleaning of the bearings is carried out by rough washing and fine washing, and a metal mesh frame can be placed on the bottom of the used container. Grease or grease is removed in the oil with a brush or the like during rough washing. At this time, if the bearing is rotated in the oil, be careful that the rolling surface will be damaged by foreign matter or the like. When the wash is fine, slowly rotate the bearing in the oil and proceed carefully. A commonly used cleaning agent is neutral non-aqueous diesel or kerosene, and a warm sputum or the like is sometimes used as needed. However, no matter which kind of cleaning agent is used, it must be filtered and kept clean. Immediately after cleaning, apply anti-rust oil or anti-rust grease to the bearing.

 

(2) Inspection and judgment:

In order to judge whether the removed bearing can be reused, it is important to check its dimensional accuracy, rotation accuracy, internal clearance, mating surface, raceway surface, cage and seal. Regarding the inspection result, it can be judged by a person who is using a conventional bearing or a proficient bearing. The criteria for judgment vary depending on mechanical properties and importance, inspection period, and the like. Bearings must not be reused if they are damaged and must be replaced.

 

5. Adjustment of bearing axial clearance

The axial clearance inside the bearing can be achieved by moving the axial position of the outer ring.

 

1 Adjust the gasket method:

A set of soft material (soft steel sheet or elastic paper) gasket is placed between the bearing end cover and the end surface of the bearing housing; when adjusting, the bearing end cover is not placed on the gasket, and the bearing end cover is evenly tightened on one side. Screw, rotate the shaft by hand until the bearing rolling element is in contact with the outer ring and there is no gap inside the shaft; at this time, the gap between the bearing end cover and the end face of the bearing housing is measured, and the shaft required for the normal operation of the bearing is added. To the gap; this is the total thickness of the required gasket, then fill the prepared gasket between the bearing end cap and the end of the housing, and finally tighten the screw.

 

2 Adjust the bolt method:

Press the pressure ring on the outer ring of the bearing and pressurize it with the adjusting bolt. Before adjusting the pressure, first measure the pitch of the adjusting bolt, then slowly tighten the adjusting bolt until there is no gap inside the bearing, then calculate the adjustment. The corresponding rotation angle of the bolt. For example, if the pitch is 1.5mm and the clearance required for the normal operation of the bearing, then the rotation angle required for adjusting the bolt is 3600×0.15l.5=360; at this time, the adjustment bolt is reversed 360, and the bearing obtains an axial clearance of 0.5 mm. Then fix it with a stop pad.

 

6. Bearing damage and countermeasures

Bearing damage:

Generally, if the bearing is used correctly, it can be used until the fatigue life is reached. However, there will be accidents that are prematurely damaged and cannot be used. This early damage, as opposed to fatigue life, is a quality use limit called a fault or accident. Many of them are caused by inadvertent installation, use, and lubrication, and foreign objects intruding from the outside are insufficiently studied for the thermal effects of the shaft and the outer casing.

 

Regarding the damage state of the bearing, such as:

 

Roller bearing ferrules, rib jams, analysis of the reasons can be considered: insufficient lubricant, unsuitable, for the supply and drainage structure defects, foreign matter intrusion, bearing installation error, shaft deflection too large, will also There are coincidences for these reasons. Therefore, it is difficult to know the true cause of the damage by only investigating the bearing damage. However, if you know the mechanical use of the bearing, the conditions of use, the structure around the bearing, and the situation before and after the accident, combined with the damage state of the bearing and several reasons, it can prevent similar accidents from happening again.

 

7. Bearing form

Inch single row deep groove ball bearings: R

Inch single-row deep groove ball bearings with flange: FR

Metric single row deep groove ball bearings: Marking omitted

Metric flanged single row deep groove ball bearings: F

Specific size metric single row deep groove ball bearings: MR

Special size metric flanged single row deep groove ball bearings: MF

Thrust bearing with channel: FM

Non-channel thrust bearing: F

Sealing ring

Teflon seals with retaining ring on both sides: TT

Steel plate dust cover on both sides: ZZ

Contact rubber seals on both sides: 2RS

 

8. Measure the bearing radial clearance should pay attention to matters

(1) Use special instrument measurement methods whenever possible.

(2) Measurement by hand is required to have higher measurement skills. This method has a large measurement error, especially when the clearance is in the edge state, which is easy to cause an error. In this case, the instrument measurement shall prevail.

(3) When measuring the feeler gauge, it shall be operated according to the standard, and shall not be measured by rolling the roller from the feeler.

(4) During the measurement process, the ball should be guaranteed to fall into the bottom of the ditch, and the closed bearing should be measured before closing. When using a loaded instrument, the measured value should also be reduced by the load increase caused by the load.

(5) For multi-row bearings, it is required that each column of clearance is qualified, and the arithmetic mean of each column of clearance is taken as the radial clearance of the bearing.


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