As an important component of industrial machinery equipment, the installation quality of bearings plays a crucial role in their use. Therefore, we need to make some preparations before bearing installation. According to data statistics, it is known that 14% of bearing pollution is caused by inadequate preparation before installation, such as environmental issues.

The installation environment of bearings is very important. They must be installed in a dry and clean environment in order to operate better.

In order to give everyone a better understanding of the preparation work for bearing installation, Zhonghua Bearing Network will share some relevant matters before bearing installation based on its understanding of bearing knowledge:

1. Adopting different installation methods based on different bearing sizes and application environments;

2. Prepare the necessary components, tools, and equipment for installation;

3. Prepare all parts that need to be installed and thoroughly clean them before installation;

4. Check the size and shape accuracy of all parts that need to be installed according to the drawings.

Attention: When installing bearings, do not open the packaging of the bearings until the preparation work is completed to prevent contamination of the shaft.

Example of standard installation and common problems of gearbox bearings

1、 Standard installation of gearbox bearings (new bearing installation standard):

1. The new bearing should be calibrated for its model, surface inspection, and radial clearance measurement should meet the requirements. After cleaning with kerosene, it should be heated to 80-100 ℃ with mechanical oil and maintained at this temperature for 30 minutes.

2. Install the bearing (model should face outward) by tapping the inner ring with a copper rod, tightly against the shaft shoulder, without clearance, and without looseness. After the bearing cools down, rotate the bearing by hand and it should rotate flexibly. The cage should work normally and rotate smoothly without any impact sound. Pay close attention to the assembly sequence of each component during assembly to avoid errors or forgetting.

3. The limit value for the temperature of the rotating bearing: 80 ℃ for the rotating rolling bearing and 65 ℃ for the sliding bearing. The rolling bearing temperature of the motor is 100 ℃. The sliding bearing temperature is 80 ℃.

2、 Maintenance steps for gearbox and bearings:

(1) Prepare the necessary lifting tools, dismantle the relevant oil and water pipelines, and seal them in a timely manner.

(2) Remove the screws on the joint surface and end cover of the gearbox, take out the stable pin, clean it, and place it properly.

(3) Measure and record the pre repair clearance of each component.

(4) Lift off the upper cover, lift out the gear, and place it at the designated location.

(5) Clean and inspect bearings and gears with kerosene, measure bearing clearance, and check the wear of gears and bearing cages.

(6) Drain the oil in the box and clean it.

(7) When replacing bearings, use a dedicated scraper. When it is difficult to remove, the inner ring of the bearing can be heated by pouring 120 ℃ hot engine oil, and acetylene flames are strictly prohibited for heating.

(8) Measure the dimensions of the journal and new bearing inner race, measure the clearance, and record it.

(9) Heat the bearing with engine oil and install it on the journal, while also installing the circlip.

(10) Retest the bearing clearance and record it.

(11) Conduct a hydraulic test on the internal cooling water discharge of the gearbox and check for wear.

(12) Lift the gear in place and rotate the large gear to ensure normal meshing and center alignment.

(13) Lift the upper cover of the gearbox, measure the top clearance of the bearing, measure the axial clearance of each part, and adjust it appropriately.

(14) Apply sealant to the joint surface, insert the positioning pin, and tighten the flange screws on the joint surface.

(15) Assemble the end cover and adjust the cushion.

(16) Connect oil and water pipelines and valves properly.

(17) Align the transmission.  

3、 Common problems and malfunctions of gearbox bearings

1. Why do bearings have thrust clearance and expansion clearance?

Metal materials have the properties of thermal expansion and contraction. When the shaft operates under different temperature conditions, the length and diameter of the shaft will also change. Therefore, in order to ensure the formation of pressure oil film in the thrust bearing, it is necessary to leave thrust clearance.

In order to ensure that the shaft is not obstructed or restricted during expansion, resulting in significant stress and damage to the bearing, an expansion gap must be left.

2. How to use the lead wire pressing method to measure the top clearance between the split bearing cover and the bearing?

Place lead wire near the bolt hole and along the arc length direction of the top of the bearing on the joint surface between the bearing seat and the bearing cover.

Install the upper cover and tighten the bolts evenly diagonally. Remove the bearing cover and measure the thickness of each lead wire using an external micrometer.

Subtract the average thickness of the lead wire at the outer ring of the bearing from the average thickness of the joint plane of the bearing seat, and the difference is a positive value for the clearance, and a negative value for the tightening force.

3. What are the hazards of bearing oil level being too low or too high?

If the oil level is too high, it will increase the resistance of the oil ring movement and cause it to slip or stop. The mutual friction of oil molecules will increase the bearing temperature, increase the oil leakage at the gap, and cause the friction power loss of the oil.

If the oil level is too low, it will make the bearing balls or oil rings unable to pick up oil, causing the bearing to not receive lubrication and causing the temperature to rise, resulting in bearing burnout.

4. What is the reason for the high temperature of rotating machinery bearings?

The oil level is low, lacking or without oil.

The oil level is too high and there is too much oil.

Unqualified or deteriorated oil quality (impurities in the oil).

Insufficient or interrupted cooling water.

The oil ring does not contain oil or does not rotate.

F The bearing is defective or damaged.

Equipment vibration.         

5. Looking at the picture to analyze the fault factors of the gearbox bearing?

Matching between bearings and bearing chambers. There is a clearance fit between the outer ring of the bearing and the bearing cover. If it is too tight, the radial clearance of the bearing will be too small due to thermal expansion during bearing rotation. If it is too loose, it will reduce the accuracy of rotation and make it easy to jump during rotation. Therefore, there is usually a distance of 0.05-0 between the outer ring of the bearing and the bearing cover A radial clearance of 10mm, and to ensure the free expansion and elongation of the shaft after being heated, sufficient expansion clearance should be left between the thrust and bearing sides of the bearing and the end cover of the bearing chamber. The clearance and value are related to the shaft length.

The inner ring of the bearing fits tightly with the tail of the shaft. If the interference value is too small, it will cause the inner ring to rotate, causing vibration and temperature rise due to friction with the shaft, causing bearing damage, and bearing wear and tear, resulting in the shaft being scrapped. If the interference value is too large, it will cause the radial clearance of the bearing to be too small, causing the bearing to get stuck or damaged. Therefore, the size of the interference value should be based on the drawing requirements or inspection regulations. In general, the fit force between the bearing and the shaft is 0.02-0.05mm.

6. Common faults and troubleshooting methods of reducers and bearings

1) New wheel box heating

A shaft or journal is bent or deformed. Solution: Replace.

The installation of bearings is incorrect or the clearance is not appropriate. Solution: Reinstall or adjust.

The bearing is worn and loose. Solution: Replace.

The gear meshing clearance is too small. Solution: Adjust.

2) High gearbox noise

A-axis bending deformation. Solution: Replace.

The gear B is severely worn. Solution: Replace.

The gear engagement is incorrect. Solution: Adjust.

Damaged bearings. Solution: Replace.

Improper bearing clearance. Solution: Adjust.

Insufficient lubricating oil in bearing f. Solution: Add lubricating oil to an appropriate amount.

Loose connections. Solution: Tighten.

3) Gearbox oil leakage

The cushion between the split surfaces of the box is damaged. Solution: Replace the cushion.

B Sealing ring aging, deformation, and wear. Solution: Replace.

The surface of the C-axis is worn or deformed at the sealing ring. Solution: Repair or replace.

The oil seal is damaged due to the high temperature of the lubricating oil. Solution: Check the cause of the heating and replace the oil seal.