Installation and maintenance of four-row cylindrical roller bearings for rolling mills

Roller bearings are an important component of rolling mills. The quality of installation and maintenance of roller bearings has an important impact on the service life of bearings. Four-row cylindrical roller bearings can withstand large radial forces, and the axial force is borne by a separate thrust bearing. Compared with general rolling bearings, the working environment of roller bearings is relatively harsh and the working load is relatively large. Most of the roller bearings that were damaged earlier were not all due to certain quality defects. In most cases, they were caused by incorrect installation methods and the lack of necessary maintenance. According to statistics, the causes of bearing failure include poor bearing lubrication accounting for 35%, bearing contamination accounting for 15%, poor installation accounting for 20%, and material fatigue failure accounting for 30%. Therefore, the correct installation and maintenance of roller bearings are important factors related to the life of roller bearings.

1. Installation of four-row cylindrical roller bearings

(I) Preparations before installation

(1) The installation site should be a clean and dry workplace. All tools should be fully prepared and kept clean. The installation should not be close to the welding site to prevent debris or dust from entering the bearing. Before installation, the instructions or drawings should be carefully compared to make the installation sequence and work steps of each bearing component clear, so as to save assembly time and reduce the pollution of the bearing in the air;

(2) Before installation, each accessory, including the roll neck, bearing box, etc., must be inspected on the surface, and the specifications, status, precision and tolerance of the accessories must be inspected to determine whether they meet the design standards. If the precision of the parts combined with the bearing does not meet the design requirements, the original precision of the bearing will be changed;

(3) The area combined with the bearing surface, including the roller neck, various holes, corners and burrs, needs to be properly cleaned, otherwise, it will affect the installation of the bearing and scratch the bearing surface, and then debris will fall into the bearing, directly causing early damage to the bearing;

(4) After the new bearing is unpacked, its assembly dimensions should be checked to see if they meet the installation requirements, and the appearance should be checked for defects such as rust, bumps, burrs, etc., and whether the ring number is correct. If there is any objection, the supplier should be contacted or the product should be returned.

(II) Installing the roller ring and inner ring

The roller ring and inner ring are generally combined and debugged by the roller processing plant. Two inner rings are installed in each four-row cylindrical roller bearing. The inner ring and the roller diameter are combined by interference. Before the combination and debugging, the inner ring needs to be heated up. After expanding to the required size, it can be installed on the roller diameter, and then the outer diameter of the inner ring is ground.

Before installation, first check the actual size of the bearing inner diameter and roller diameter to confirm whether the two sizes meet the interference requirements during design; after heating, quickly check the bearing inner diameter size to see if it can meet the installation requirements. Otherwise, the inner ring may be half-installed and hold the shaft, and the inner ring cannot be pushed to the required position, thus wasting the inner ring resources; in the four-row cylindrical roller bearing, the inner ring is combined with the roller neck by interference fit, and the inner ring must be heated during the specific installation process to about 100°C, but not more than 150°C, and the time is within 2 hours, otherwise the inner ring material structure may change, and the inner ring cannot shrink to its original size after cooling, resulting in the interference fit not meeting the design requirements. Heating can be done by oil tank or induction, and never by open flame.

(III) Installation of outer ring and rolling element

The outer ring and the inner hole of the bearing seat are generally transition fit. First, the roundness of the bearing seat should be checked. The bearing seat should be thoroughly cleaned before measurement. Use an inner diameter micrometer to measure at four positions of the inner hole of the bearing seat. Each position is measured twice at 90° intervals to ensure that the roundness meets the requirements of the drawing. For the same set of four-row cylindrical roller bearings, the outer ring and roller assembly have the same circular size, so try not to mix them to ensure the original processing accuracy of the bearings. Install the skeleton seal, water seal and O-ring on the end cover on the side of the bearing seat close to the roller body, and then install the end cover on the bearing seat. Install the side ring, outer ring and its accessories, retaining ring, etc. in order. The threaded holes on the retainer are used for hoisting. The spare mounting holes on the outer ring can be used to lift the outer ring and its accessories, and put them vertically into the bearing box. For small bearings, the outer ring, roller and retainer can be slowly knocked into the bearing with a copper hammer. In addition, during the installation of the outer ring, it is necessary to always pay attention to whether there are markings on its surface and the surface of the retainer. If there are, it is necessary to keep the same markings during the installation process; for four-row cylindrical roller bearings with movable gears, the various accessories must be installed in the order marked on the end face of the ring, and do not mix them.

2. Lubrication of four-row cylindrical roller bearings

In the actual use of bearings, in order to ensure the normal operation of bearings to the greatest extent, complete lubrication is required;

First, avoid or minimize the contact between bearings and rolling elements, raceways and cages, thereby reducing the loss caused by friction;

Second, the oil film is formed on the friction surface. After the oil film is formed, the contact area of each component can be effectively expanded, thereby reducing the tensile stress of the contact surface to a certain extent, thereby extending the service life of the contact surface;

Third, after using lubricants, it can play a certain role in anti-corrosion;

Fourth, lubricants can dissipate heat and remove particles that appear during the use of bearings;

Fifth, lubricants can improve the sealing performance of equipment, thereby avoiding contamination by external particles;

Sixth, vibration and noise can be reduced to a great extent.

4. Maintenance of four-row cylindrical roller bearings

The service life of bearings depends largely on the maintenance of bearings. The bearing must be removed from the roll for inspection regularly to find the problem load area as early as possible to prevent it from expanding further, thereby ensuring the longest operating time of the bearing to the greatest extent.

Build bearing documents, clean and inspect bearing components on time, observe the damage of the running surface of the raceway and the surface of the roller, and replace them in time if they exceed the specified standards. In the process of using the bearing, the original bearing components must be used first, and other accessories must be measured twice before they can be selected and used.

Change the bearing load area. For example, if the initial load area is 1, the load area 3 in the opposite direction can be used after the next inspection and cleaning, then the load area 2, load area 4, and so on. In this way, the outer ring deformation of the bearing can be automatically corrected during the operation of the bearing, the load area stress angle can be maintained, fatigue damage stress can be reduced, and the use value of each surface can be fully utilized to effectively extend the service life of the bearing.

Regularly check and adjust the side slide of the support roller bearing seat to ensure that the axes of each roller are parallel. In addition, the connecting shaft of the transmission system must be replaced on time, otherwise the gap will be too large, resulting in additional axial force, which will eventually lead to bearing damage.

5. Storage of rolling mill bearings

As a bearing component with high tightness, its storage environment has very high requirements:

First, the temperature and humidity of the warehouse. First of all, it is necessary to maintain the air in the warehouse with high fluidity and maintain the temperature above 25℃; secondly, excessive humidity will cause rust and corrosion of the bearings, so the humidity of the warehouse needs to be maintained below 70%;

Second, the placement of the warehouse. Bearings need to be stored separately. When placed in the same place with other goods, other goods cannot be chemical products;

Third, the placement of bearings. When placing bearings, they must be kept above 3cm from the ground and placed flat, and keep a certain distance from the radiator;

Fourth, regular inspection. According to the anti-rust specifications of bearing goods, inspections are required every once in a while. If rust is detected in the packaging, it is necessary to repackage it in time.

Practice has proved that if the four-row cylindrical roller bearings are properly installed and maintained, the service life of the bearings will be greatly extended!

Qiqiang large cylindrical roller bearings are durable and of guaranteed quality. Whether it is industrial application or mechanical equipment, it can easily handle it. Strong stability and long life make the machine more efficient!

Learn more: http://www.cqqbbearing.com/en/products/Four-Row-Cylindrical-Roller-Bearings/1048