How to extend bearings service life?
Bearings are important parts in mechanical equipment. To ensure the best performance of the bearings, reliable work, correct installation and operation, reasonable maintenance is very important.
First, lubrication is the key point.
Choose a suitable lubrication system and high-quality lubricants. The lubricant film will separate the surfaces of the oil film that are in contact with each other and provide the necessary protection against corrosion and wear. Therefore, for all rotating or reciprocating parts, especially bearings and gears, for normal operation, the lubricant film must not lack. For splash lubrication or circulating lubrication systems, the oil film can also transfer heat.
Factories often have unnecessary shutdowns and equipment deterioration due to improper lubrication. Insufficient oil supply can cause increased wear and temperature rise, causing excessive wear and / or early bearing failure and damage. Excessive lubrication, especially high-speed operation equipment, will generate too much heat due to oil agitation, which will cause chemical deterioration of the lubricating oil and will also cause bearing damage.
Proper lubrication and regular maintenance can avoid bearing damage caused by lubrication problems.
Secondly, adjustment is very important.
During assembly or installation, if the internal clearance of the bearing is too large or too small, or in some cases, the pre-load is too high, it may cause early damage and shorten the bearing life. In addition to downtime and costly 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 is the best way to prevent problems. If the time is tight, you can push the adjustment device forward or remove the gasket to correct the loose tapered rolling bearing set.
On the other hand, if the bearing is adjusted too tightly, it may cause overheating damage and the bearing has to be replaced. The process of assembling and installing bearings must be accurate and repeatable, and can be verified after installation. In addition, other part parameters must be considered to optimize system performance.
In addition, use the equipment in accordance with OEM requirements and set appropriate predictive maintenance items such as monitoring of lubricating oils or greases, which should include root cause analysis. In this way, even the problematic equipment, its uptime can be greatly extended.
Proper lubrication and maintenance are critical, and correct installation and use are also indispensable, and then make full use of existing condition monitoring equipment to escort. Failure to comply with installation and maintenance requirements will cause equipment failure and constitute a major safety hazard.
Do the inspection after the bearing is installed
The correctness of the bearing installation has a direct impact on its life and the accuracy of the host.
If installed improperly, the bearing will not only have vibration, high noise, low accuracy, increasing temperature rise, but also the risk of being stuck and burned out; otherwise, good installation will not only ensure accuracy, but also greatly extend the 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 running parts and the fixed parts collide, whether the lubricating oil can smoothly flow into the bearing, and whether the sealing device and the axial fastening device are installed correctly.
2. Check the radial clearance
Except for installing bearings with pre-interference, radial clearance should be checked. The deep groove ball bearing can be checked by hand rotation, and it is better to be stable, flexible, no vibration, and no left and right swing. Cylindrical roller and spherical roller bearings can be checked 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 roller length.
When the radial clearance of the bearing cannot be measured with a feeler gauge, the amount of movement of the bearing in the axial direction can be measured instead of the reduction of the radial clearance. Normally, if the bearing inner ring is a tapered hole, the amount of axial movement on the conical surface is about 15 times the amount of radial clearance reduction.
The radial clearance of the bearing can be adjusted after some installations are unqualified, such as angular contact ball bearings and tapered roller bearings; some are adjusted according to the standards during manufacturing, and can not be adjusted after installation. Such as deep groove ball bearings, self-aligning ball bearings, cylindrical roller bearings, self-aligning roller bearings
If this type of bearing fails to pass the inspection after installation, the radial assembly clearance is too small, it means that the bearing is not properly selected for the fit, or the assembly part is not processed correctly. At this time, the bearing must be removed, the cause must be ascertained, and then eliminated after reinstallation. Of course, bearing clearance is too large.
3. Check the tightness of the bearing and shaft shoulder
In general, bearings that fit tightly against interference must bear against the shaft shoulder. Testing method:
(1) Lighting method. That is, the electric lamp is aligned with the bearing and the shoulder, and the light leakage is judged. If there is no light leakage, it means that the installation is correct; if there is even light leakage around the shaft shoulder, it means that the bearing is not tight against the shaft shoulder, and the bearing should be pressed to make it tight; if there is some light leakage, it means that the bearing installation is inclined, you can use a hammer or a copper rod Or the sleeve strikes the inner ring of the bearing, and then slowly settle.
(2) Thick and thin gauge inspection method. The thickness of the thickness gauge should start from 0.03mm. During the inspection, insert a few places on the end surface of the inner ring of the bearing and the entire circumference of the shoulder. If a gap is found and it is very uniform, it means that the bearing is not installed in place. The inner ring of the bearing should be pressurized to close the shoulder; if it is increased The pressure is not too tight, indicating that the fillet of the rounded part of the journal is too large, and the bearing is stuck. The rounded corner of the journal should be trimmed to make it smaller; if it is found that the thickness of the end surface of the bearing inner ring and the bearing shoulder are thin Passed, indicating that it must be disassembled, trimmed and reinstalled.
If the bearing is installed in the bearing housing hole with an interference fit, and the outer ring of the bearing is fixed by the shell hole shoulder, whether the end face of the outer ring is close to the end face of the shell hole shoulder, and whether the installation is correct, can also be tested with a thick gauge.
4. Inspection after thrust bearing installation
When installing thrust bearings, the perpendicularity of the shaft ring and shaft centerline should be checked. The method is to fix the dial indicator on the end surface of the case, so that the contact of the dial is on the bearing ring raceway while rotating the bearing, and observe the pointer of the dial indicator. If the pointer deflects, it means that the shaft ring and the center line of the shaft are not perpendicular. When the case hole is deep, you can also use the extended dial gauge to check.
When the thrust bearing is installed correctly, its seat ring can automatically adapt to the rolling of the rolling body to ensure that the rolling body is located in the upper and lower ring raceways. If the mounting is reversed, not only will the bearings work abnormally, but the mating surfaces will be severely worn. Since the difference between the shaft ring and the seat ring is not obvious, extreme care should be taken during assembly to avoid mistakes.
In addition, there should be a gap of 0.2-0.5mm between the thrust bearing seat ring and the bearing seat hole to compensate for errors caused by inaccurate parts processing and installation. It can ensure its automatic adjustment, avoid contact friction, and make it operate 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 working temperature of the bearing should be lower than 90 ° C. If the temperature is too high, it will cause the bearing to anneal or burn, and reduce the service life.