VISTA Technology knowledge: Installation and Maintenance of Four Row Tapered Roller Bearings

Hot tags: work roll(1), intermediate roll(1), four row tapered roller bearing(1)

Problems of four row tapered roller bearings installed on work roll and intermediate roll

Abstract: problems existing in the use of four row tapered roller bearings installed on work roll and intermediate roll, cause analysis and effect after installation and adjustment.

Key words: work roll, intermediate roll, four row tapered roller bearing

 

1. Introduction

FAG four row tapered roller bearings 802045-H122AA and 802137-H122AA  are installed as radial bearings for the work roll and intermediate roll of the six high cold rolling mill in AnGang Cold Rolling Plant, and four row cylindrical roller bearings are used as radial bearings for the support roll. The radial bearings of the work roll and intermediate roll are lubricated by oil and air, and the radial bearings of the support roll are lubricated by circulating oil. During the use of the cold rolling mill from November 2007 to June 2008, it was found that there were dents on the raceway of four row tapered roller bearings and serious spalling on the inner race of four row cylindrical roller bearings. The outer ring raceway of  bearing 802137-H122AA has dents, and the outer ring raceway of bearing 802045-H122AA has dents in areas III to IV, some of which are deep. The inner race of the four row cylindrical roller bearing is peeling off, the bearing rolling body is rusted, there are axial indentation on the rolling surface, and the roll neck surface matched with the four row tapered roller bearing is worn.


four row tapered roller bearing 


2. Failure Cause Analysis

According to the field observation and analysis of FAG four row tapered roller bearing, the dent on the raceway is caused by foreign impurities. A large number of metal particles with hard texture and large size are found in the bearing seat. Impurities should be left inside the bearing seat during processing. These hard particles will cause deep dents on the raceway during bearing operation. Many fine particles are found in the filter nozzle of oil-gas lubrication, which may be brought by lubricating equipment pipeline or lubricating oil. These particles leave shallow fine indentation on the raceway.

 

3. Improvement Measures

Before the bearing is reinstalled, it is recommended to thoroughly clean the bearing, bearing seat and lubrication system to remove impurities. According to the number and depth of dents, the four row tapered roller bearing can continue to be used, and its performance is basically not affected. It should be noted that the outer ring of FAG four row tapered roller bearing is marked with four bearing areas. It is recommended to take area I as the bearing area and adjust the bearing area after running for 1000 ~ 1200h. Judging from the dents in areas III to IV of bearing 802045-H122AA outer race raceway, areas III to IV shall be placed in the bearing area during initial installation. In view of the deep dent in the existing part of this area, it is recommended to adjust this area relatively during re installation, that is, areas I and II are placed in the bearing area.

 

In addition, the four row tapered roller bearing mating surface of the roll neck is worn. Due to the limitation of the structural characteristics of the four row tapered roller bearing itself and the clearance fit between the bearing and the roll neck for the convenience of roll replacement, there is relative rotation between the bearing inner ring and the roll neck. In order to reduce the wear of roll neck, it is necessary to ensure the proper fit and good lubrication between inner ring and roll neck. According to the wear of the roll neck, it is recommended to check the size of the roll neck to verify whether it is within the recommended dimensional tolerance. At the same time, it is necessary to ensure that the oil supply of oil-gas lubrication and the oil level in the bearing seat are at the position of flooding half of the roller at the bottom of the bearing. For four row cylindrical roller bearings, the serious peeling of the inner race material may be caused by pre-damage. Judging from the serious spalling of the raceway at the distance between the rolling elements and the axial indentation on the rolling elements, there may be scratches between the rolling elements and the raceway of the inner ring during the installation of the bearing. The pre-damage may also be caused by local burns caused by grinding the inner race raceway or defects in bearing materials and heat treatment. If you want to obtain the exact cause of early damage, analyze the metal materials of the damaged raceway and roller, including the depth of carburized layer of inner race raceway, grinding burn, indentation stress distribution of damaged roller, etc.

 

In addition, in case of large-area corrosion on the bearing roller, the moisture content in the lubricating oil should be controlled, which significantly affects the service life of the bearing.

 

4. Installation of Four Row Tapered Roller Bearings

The basic requirements for installation are: specially trained installation personnel shall check the geometric tolerance of the bearing mating surface, keep the installation site clean, open the bearing package after installation preparation, and do not clean the antirust oil of the bearing.

 

(1) Configuration of bearing assembly. Open the bearing package, do not wash off the anti rust oil, and check the bearing components to ensure that the bearing components are complete, the production year is the same, and the production serial number and installation sequence are indicated by letters. Four bearing areas are marked on the bearing mating surface with I to IV separated by 90 °, and the bearing area is marked on the outer diameter of the outer ring of the axial etching line.

 

(2) Fit surface of bearing. In order to prevent the friction corrosion of the mating surface of the roll neck and the bearing seat, it must be coated with a thin layer of installation paste (such as FAG Arca. Mounting paste), fix the end cover of the roll body end on the bearing seat with bolts, and place the opening of the bearing seat upward on the plane support.

 

(3) Open bearing. First, lift the outer ring D-E and the outer spacer d with the e-end down and put them into the bearing seat, and then lift the components in the given order and put them into the bearing seat. Pay attention to the alignment of the bearing area. The rear mounted parts must be in full contact with the front parts without inclination or skew.

 

(4) Installation of open bearing with pressed cage. For the bearing with stamped cage, place the inner ring E-Ce flat on the support (E-end faces down), then place each component one by one in the correct order, and use the lifting device to install the complete bearing component into the bearing seat to ensure the correct alignment of the bearing area I. For the pin type cage bearing, install the inner ring E-Ce (E-end downward), the inner spacer C (locating edge downward), the double row outer ring B-D and the outer spacer B into the bearing seat, install the pin type cage bearing, and install the inner ring A-Ca and the single row outer ring A-B into the bearing seat to ensure the correct alignment of the bearing area I. the pin type cage bearing can be installed by using the lifting device like the bearing with stamping cage.

 

(5) Installation of seal bearing. A special lifting device is used to install the sealed tapered roller bearing. Completely assemble the bearing assembly on the lifting device according to the given sequence. First install the sealing ring E. when installing the grease lubricated bearing, manually lubricate the roller and cage assembly. Ensure that the bearing area I is correctly aligned and install the assembled complete bearing into the bearing seat.

 

(6) Rotating bearing. Install the second end cover gently (do not lock the bolts) on the bearing seat with 4 bolts at the symmetrical position on the circumference, rotate the bearing seat to the horizontal position, and fix the clamp on the end face of the inner ring with a pull rod. At the beginning, it should be lighter, and the clamp can only contact the end face of the inner ring. For sealed bearings, the lifting device is also used as a fixture. Gradually tighten the pull rod and end cover bolts, and slowly and evenly rotate the inner ring until the inner ring completely fits with the inner spacer C without separation. Use a feeler gauge to measure the clearance s between the end cap and the bearing seat and determine the sealing thickness B. Rigid seal B = S - (0.05 ~ 0.1) mm; Elastic seal B = 1.2Smm.

 

(7) Install the seal. Unscrew the end cap bolts and remove the end cap, insert the seal with the required thickness into the end cap, and apply grease to the inner ring hole to complete the installation.

(8) Heat the labyrinth seal ring in the oil bath and push the labyrinth seal ring together with the O-ring onto the roll neck. During the cooling process of the labyrinth seal ring, it must be tightly pressed on the end face of the roll.

 

(9) Push the assembled bearing seat onto the roll neck, regularly check the effectiveness of the bearing seat seal and the bearing temperature, and change the bearing area after the bearing works for 1000 ~ 1200h. Record all maintenance and inspection work of the bearing on the rolling bearing inspection card. Change the bearing area of the bearing, disassemble the bearing in the reverse order of installation, carefully clean the bearing parts, then apply oil immediately, visually check whether the raceway and roller are damaged, check the axial clearance, pack the bearing with new grease, install the bearing according to the installation instructions, and move to the next bearing area.

 

When changing the bearing area for the first time, rotate the outer ring 180 ° to bearing area III; The second rotation is 90 ° to bearing area IV; Rotate 180 ° to II for the third time. For the tapered roller bearing with seal, after the bearing works for 300h, 600h and 900h respectively, conduct supplementary inspection according to the following steps: remove the bearing seat and remove the end cover, and check the amount and state of grease in the bearing and labyrinth seal. If the grease is discolored or contaminated, fill the bearing and labyrinth seal with new grease. Carefully check the bearing seal, replace the seal even if there is slight damage, and record all maintenance and inspection work of the bearing on the rolling bearing inspection card.

 

5. Effect

The four row tapered roller bearings 802045-H122AA and 802137-H122AA of work roll and intermediate roll of six high cold rolling mill were reinstalled and adjusted. No abnormality was found after operation, the axial and radial runout did not exceed the tolerance, and the bearing temperature was normal. One year later, the four row tapered roller bearings were disassembled and inspected again, and the wear of raceway and roller were within the normal range.

 

Through the re-cleaning of equipment and the adjustment of bearings, the average service life of bearings is extended from 8,000h to more than 12,000h, and the annual production cost is saved (3 ~ 5) million yuan.

 

More about VISTA High-quality Four-row Tapered roller bearings:

Four-row tapered roller bearings can accommodate combined (radial and axial) loads at low to moderate speeds. They are used almost exclusively in work roll applications such as rolling mills.


Four-row tapered roller bearings 


Depending on their design, four-row tapered roller bearings provide the following main features and benefits:

·Long service life
The four-cup design (four separate outer rings) provides optimal load distribution over all four rows of rollers.

·Enhanced operational reliability
Optimized surface finish on the contact surfaces of the rollers and raceways supports the formation of a hydrodynamic lubricant film.

·Improved sealing performance with less leakage and less frictional heat
The optimized seal design ensures high protection against external contamination but keeps friction and frictional heat low. This seal design also provides a better retention of lubricant, minimizes environmental impact and reduces maintenance costs.

·Equal load carrying capacity for sealed and open bearings
The optimized and compact seal design enables identical internal design.

·Total bearing interchangeability
Bearings with and without intermediate rings as well as open and sealed bearings are available with identical external dimensions. This allows total bearing interchangeability of current standard design bearings with those without intermediate rings and/or with optimized seal design.

·Separable mounting and simpler inspection
Optimized designs without intermediate rings enable to dismount and separate the cage and roller assemblies and seals. This facilitates mounting, dismounting and also maintenance inspection routines.

·Axial space-saving and cost-effective solution for roll necks
The roll necks can be relatively short, no separate axial bearings are required and identically designed chocks (fig. 1) can be used on both sides of the roll.

·Simple axial location on roll necks
Tighter inner ring width tolerances facilitate the tolerancing and dimensioning of surrounding components.

 

Vista tapered roller bearings are particularly designed to carry combined (radial and axial) loads. They have single,double and four-row tapered roller designs. The single row tapered roller bearings are able to accommodate radial loads and axial loads in one direction only. Under radial loads, axial component force is affected in the bearing which must be counteracted, so the bearings are normally adjusted against a second bearing. Vista tapered roller bearings include metric and inch series single row tapered roller bearing, metric and inch series double row tapered roller bearing, four row tapered roller bearing.


tapered roller bearings 


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2022-04-19

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