Industry News

How to install and inspect to improve bearing life

2019-4-20

Bearings are important parts in mechanical equipment. It is very important to ensure the best performance, reliable work, correct installation and operation of the bearings. What are the methods to extend bearing life?

  First, improve bearing life through lubrication

  Choose the right lubrication system and high quality lubricant. Lubricating oil membranes 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, if normal operation is required, the lubricating oil film is not available. lack. In the case of splash lubrication or a recirculating lubrication system, the oil film also transfers heat.

  Factories often experience unnecessary downtime and deterioration of equipment conditions due to improper lubrication. Insufficient oil supply can result in increased wear and temperature rise, resulting in excessive wear and/or early bearing failure and damage. Excessive lubrication, especially in high-speed operation, will cause excessive heat due to oil agitation, causing chemical degradation of the lubricant and damage to the bearing. Proper lubrication and regular maintenance can avoid bearing damage caused by lubrication problems. Proper lubrication should be achieved by: 1) following the instructions for use by the equipment manufacturer for each unit; 2) when adding grease, it should be filled between the bearing rolling parts and the housing (or retainer) to Ensure that a sufficient amount of grease enters, the critical raceway surface is fully lubricated; 3) should pay attention to when the bearing should be fatliquored; 4) monitor the indicating instrument of the equipment to detect signs of problems such as temperature fluctuations and/or abnormal high temperature as early as possible; 5) Pay attention to equipment noise or abnormal vibration; 6) Observe lube oil leakage; 7) Sampling lubricant regularly and check for contamination.
  Second, the bearing installation and adjustment

  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, it may lead to early damage and shortened bearing life. In addition to causing downtime and costly repairs, improper assembly and installation of the bearings may have more negative effects, such as affecting the operation of other parts and shortening their service life. Assembly, installation and scheduled maintenance are the best way to prevent problems from occurring according to the equipment manufacturer's manual. If the time is tight, push the adjustment device or remove the spacer to correct the loose tapered roller bearing set. On the other hand, the bearing is too tightly adjusted, which may cause overheating damage and the bearing has to be replaced. The process of assembling and mounting the bearings must be accurate, repeatable, and verifiable 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 lubricants or greases, including fault root cause analysis. In this way, even the problematic equipment can greatly extend its uptime. Proper lubrication and maintenance are critical, and proper installation and use are also indispensable, taking advantage of existing condition monitoring equipment to escort. Failure to comply with installation and maintenance requirements will result in equipment failure and constitute a major safety hazard. After the bearing is installed, it is necessary to verify the correctness of the bearing installation, which has a direct impact on the life and the accuracy of the main engine. If improperly installed, the bearing not only has vibration, high noise, low precision, large temperature rise, but also the danger of being stuck and burned. Conversely, if it is installed well, it can not only ensure accuracy, but also prolong its life.

  Third, the bearing after the installation inspection

  After the bearing is installed, it must be inspected.

  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 flow smoothly into the bearing, and whether the sealing device and the axial fastening device are installed correctly.

  2, check the radial clearance

  Radial clearance should be checked except for the installation of bearings with pre-interference. Deep groove ball bearings can be tested by hand rotation, which is smooth and flexible, vibration-free, and no right and left swing. Cylindrical roller and spherical roller bearings can be tested with a feeler gauge. Insert the feeler gauge between the roller and the bearing ring. The 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 amount of axial movement of the bearing can be measured instead of the reduction of the radial clearance. Normally, if the inner ring of the bearing is a tapered hole, the amount of axial movement on the conical surface is approximately 15 times the amount of radial clearance reduction. The radial clearance of the bearing can be adjusted after some installation failures, such as angular contact ball bearings and tapered roller bearings; some are adjusted according to the standard at the time of manufacture, and can not be adjusted after failing after installation. Such as deep groove ball bearings, self-aligning ball bearings, cylindrical roller bearings, spherical roller bearings and so on. If the bearing is unqualified after installation, the radial assembly clearance is too small, indicating that the bearing is not properly selected, or the assembly part is not processed correctly. At this point, the bearing must be removed, the cause identified, eliminated, and reinstalled. Of course, the bearing clearance is too large.

  3. Check the tightness of the bearing and the shoulder

  In general, bearings that are tightly fitted with an interference fit must be placed against the shoulder. Inspection method: (1) lighting method. Just align the lamp with the bearing and the shoulder to see the light leakage. If there is no light leakage, the installation is correct; if the light is uniformly leaked around the shoulder, the bearing is not close to the shoulder, and the bearing should be pressed against the bearing; if there is part of the light leakage, the bearing is tilted, and the hammer and copper rod can be used. Or the sleeve hits the inner ring of the bearing and slowly settles. (2) Thickness gauge test method. The thickness of the gauge should start from 0.03mm. During the test, try to insert several places on the inner circumference of the bearing inner ring end and the shoulder. If there is a gap and it is even, it means that the bearing is not in place, and the inner ring of the bearing should be pressed to close the shoulder; if it is enlarged The pressure is also not tight, indicating that the rounded corners of the journal are too large, and the bearing is stuck. The journal fillet should be trimmed to make it smaller; if the bearing inner ring end face and the bearing shoulder are thick and thin, Pass, indicating that it must be disassembled, trimmed, and reinstalled. If the bearing is installed in the bearing housing hole with an interference fit, when the bearing outer ring is fixed by the housing hole retaining shoulder, whether the outer ring end surface and the housing hole retaining shoulder end face are tight, the installation is correct, and the thickness gauge can also be used for inspection.

  4. Inspection of thrust bearing after installation

  When installing a thrust bearing, check the verticality of the shaft ring and the centerline of the shaft. The method is to fix the dial gauge to the end surface of the casing, so that the contact of the watch top rotates the bearing on the bearing shaft raceway, and observes the dial gauge pointer. If the pointer is yawed, the shaft ring and the shaft center line are not perpendicular. When the case hole is deep, it can also be tested with an extended dial gauge. When the thrust bearing is installed correctly, the seat ring can automatically adapt to the rolling of the rolling elements, ensuring that the rolling elements are located in the upper and lower ring raceways. If it 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, the assembly should be extra careful, and do not make mistakes. In addition, there should be a gap of 0.2-0.5mm between the seat ring of the thrust bearing and the bearing housing hole to compensate for the error caused by inaccurate machining and installation. When the center of the bearing ring is offset during operation, this gap It ensures that it automatically adjusts to avoid friction and make it work properly. Otherwise, it will cause severe damage to the bearing.

  5. Check whether bearing noise, temperature rise and vibration meet the requirements.  

Generally, the working temperature of the bearing should be lower than 90 °C. When the temperature is too high, the bearing will be annealed or burnt, which will reduce the service life.