How to prolong the service time of bearings
Bearings are important parts in mechanical equipment. To ensure the best performance of the bearings, correct installation and operation and reasonable maintenance are very important. To extend the service life of the bearing, three aspects need to be done.
First of all, lubrication is the key
Choose a suitable lubrication system and high-quality lubricants. The lubricating oil film separates the oil film surfaces that are in contact with each other due to the load bearing and provides the necessary protection against corrosion and wear. Therefore, for all rotating or reciprocating parts, especially bearings and gears, if normal operation is required, the lubricating oil film is indispensable lack. If it is splash lubrication or circulating lubrication system, the oil film can also transfer heat.
Factories often experience unnecessary shutdowns and deterioration of equipment due to improper lubrication. Insufficient oil supply will lead to increased wear and temperature rise, resulting in excessive wear and/or early bearing failure and damage. Excessive lubrication, especially high-speed equipment, will generate excessive heat due to oil agitation, chemically degrade the lubricating oil, and cause bearing damage.
Proper lubrication and regular maintenance can avoid bearing damage caused by lubrication problems. To ensure reasonable lubrication:
1. Follow the instructions set by the device manufacturer for each device;
2. When adding grease, it should be filled between the rolling parts of the bearing and the housing (or retainer) to ensure that sufficient grease enters and the surface of the key raceway is fully lubricated;
3. Pay attention to when the bearings should be greased;
4. The indicating instrument of the monitoring equipment, in order to find the signs of the problem as early as possible, such as temperature fluctuation and/or abnormal high temperature;
5. Pay attention to equipment noise or abnormal vibration;
6. Observe the lubricating oil leakage;
7. Regularly sample the lubricating oil and check for contamination.
Secondly, reasonable adjustments are very important
During assembly or installation, if the internal clearance of the bearing is too large or too small, or in some cases, the preload is too high, which may cause early damage and shorten the life of the bearing. In addition to causing downtime and expensive maintenance, improper bearing assembly and installation may also have more negative effects, such as affecting the operation of other parts and shortening their service life.
According to the equipment manufacturer's manual, assembly, installation and regular maintenance are the best way to prevent problems. If the time is tight, the adjustment device can be pushed forward or the gasket can be removed to correct the too loose tapered rolling bearing set.
On the other hand, if the bearing is adjusted too tightly, it may cause overheating and damage, and the bearing has to be replaced. The process of assembling and installing the bearing must be accurate and repeatable, and it can be verified after the installation is completed. In addition, other component parameters must be considered to optimize system performance.
In addition, use the equipment in accordance with the requirements of the OEM, and set appropriate predictive maintenance items such as monitoring of lubricating oil or grease, which should include the root cause analysis of the failure. In this way, even if it is a problematic device, its uptime can be greatly extended.
Correct lubrication and maintenance are very important, and correct installation and use are indispensable, and then make full use of the existing condition monitoring equipment to escort. Failure to follow the installation and maintenance requirements will cause equipment failure and constitute a major safety hazard.
Do the inspection after the bearing is installed
Whether the bearing is installed correctly or not has a direct impact on its life and the accuracy of the main engine. If it is installed improperly, the bearing will not only have vibration, high noise, low accuracy, and large temperature rise, but also the danger of being stuck and burned; on the contrary, if it is installed properly, it will not only ensure accuracy, but also greatly extend its life. Therefore, after the bearing is installed, it must be inspected.
The key inspection items are as follows
1. Check the installation location
After the bearing is installed, first check whether the moving parts and the fixed parts collide, whether the lubricating oil can flow into the bearing smoothly, and whether the sealing device and the axial fastening device are installed correctly.
2. Check the radial clearance
Except for the installation of bearings with pre-interference, the radial clearance should be checked. Deep groove ball bearings can be tested by hand rotation, so that they are stable and flexible, without vibration, and without side-to-side swing. Cylindrical roller and spherical roller bearings can be inspected with a feeler gauge. Insert the feeler gauge between the roller and the bearing ring. The insertion depth of the feeler gauge should be greater than 1/2 of the length of the roller.
When the radial clearance of the bearing cannot be measured with a feeler gauge, the displacement of the bearing in the axial direction can be measured instead of the reduction in the radial clearance. Under normal circumstances, if the inner ring of the bearing is a conical hole, the axial movement on the conical surface is about 15 times the radial clearance reduction.
The radial clearance of the bearings can be adjusted after installation, such as angular contact ball bearings and tapered roller bearings; some have been adjusted in accordance with the standards during manufacturing, and cannot be adjusted after installation. Such as deep groove ball bearings, self-aligning ball bearings, cylindrical roller bearings, spherical roller bearings, etc.
If this type of bearing is unqualified after installation and the radial assembly clearance is too small, it means that the matching selection of the bearing is improper or the assembly part is processed incorrectly. At this time, the bearing must be removed, the cause must be found out, and it must be eliminated and reinstalled. Of course, the bearing clearance is too large.
3. Check the tightness of the bearing and the shaft shoulder
Under normal circumstances, a bearing fitted with a tight fit interference must be close to the shaft shoulder. Testing method:
(1) Lighting method. That is to say, aim the light at the bearing and the shaft shoulder, and judge the light leakage. If there is no light leakage, the installation is correct; if there is even light leakage around the shaft shoulder, it means that the bearing is not close to the shaft shoulder, and pressure should be applied to the bearing to make it close; if there is some light leakage, it means that the bearing is installed tilted. You can use a hammer or copper rod. Or the sleeve knocks on the inner ring of the bearing and slowly settles.
(2) Thickness gauge inspection method. The thickness of the thickness gauge should start from 0.03mm. During the inspection, try to insert several places on the entire circumference of the bearing inner ring end face and the shaft shoulder. If there is a gap and very uniform, it means that the bearing is not installed in place, and the bearing inner ring should be pressurized to make it close to the shaft shoulder;
If the pressure is increased and the tightness is not tight, it means that the rounded corners of the rounded part of the journal are too large, and the bearing is stuck. The rounded corners of the journal should be trimmed to make it smaller; if the end face of the bearing inner ring and the bearing shoulder are found in some parts The thickness gauge can pass, indicating that it must be disassembled, trimmed, and reinstalled at this time.
If the bearing is installed in the bearing housing hole with an interference fit, when the outer ring of the bearing is fixed by the housing hole shoulder, whether the end face of the outer ring is tight with the housing hole shoulder end and whether the installation is correct can also be checked with a thickness gauge.
4. Inspection after installation of thrust bearing
When installing the thrust bearing, check the verticality of the shaft ring and the shaft center line. The method is to fix the dial indicator on the end surface of the case, make the contact of the indicator rest on the raceway of the bearing shaft ring while rotating the bearing, while observing the dial indicator pointer, if the indicator yaws, it means that the shaft ring and the center line of the shaft are not perpendicular. When the box shell hole is deep, it can also be inspected with an extended dial gauge.
When the thrust bearing is installed correctly, its seat ring can automatically adapt to the rolling of the rolling elements to ensure that the rolling elements are located in the upper and lower ring raceways. If it is installed backwards, not only the bearing will not work properly, but also the mating surfaces will be severely worn. Since the difference between the shaft ring and the seat ring is not very obvious, you should be extra careful during the assembly and make no mistake.
In addition, there should be a gap of 0.2-0.5mm between the seat ring of the thrust bearing and the bearing seat hole to compensate for the errors caused by inaccurate parts processing and installation. When the center of the bearing ring shifts during operation, this gap It can be ensured that it is automatically adjusted, avoiding contact and friction, and making it work normally. Otherwise, it will cause severe damage to the bearing.
5. Check whether the bearing noise, temperature rise, and vibration meet the requirements
Generally, the operating temperature of the bearing should be lower than 90°C. When the temperature is too high, it will cause the bearing to heat and anneal or burn out, reducing the service life.
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