How to Install and Inspect to Improve The Service Life of Bearings

Bearing is an important part of mechanical equipment, in order to ensure the best performance of bearing, reliable work, correct installation and operation, reasonable maintenance is very important. Which methods of prolonging bearing life?

1. Enhancing the Service Life of Bearings by Lubrication

Choose suitable lubrication system and high quality lubricant. Lubricating oil film will separate the surface of oil film which bears contact with each other and provide necessary protection against corrosion and wear. Therefore, lubricating oil film is indispensable for all rotating or reciprocating moving parts, especially bearings and gears, to operate normally. For splash lubrication or cyclic lubrication systems, the oil film can also transfer heat.

Unnecessary shutdown and deterioration of equipment condition often occur in factories due to improper lubrication. Insufficient oil supply will lead to increased wear and temperature, resulting in excessive wear and/or early failure and damage of bearings. Excessive lubrication, especially for high-speed equipment, will cause excessive heat due to oil agitation, chemical deterioration of lubricating oil and bearing damage. Correct lubrication and regular maintenance can avoid bearing damage caused by lubrication problems. To ensure reasonable lubrication, the following should be done: 1) follow the instructions set by the equipment manufacturer for each equipment; 2) when adding lubricating grease, it should be filled between the rolling parts of the bearing and the housing (or guard ring) to ensure sufficient lubricating grease to enter and the surface of the key raceway to be fully lubricated; 3) pay attention to when the bearing should be greased; 4) monitor and control; Instrumentation of equipment to detect the signs of problems as soon as possible, such as temperature fluctuation and/or abnormal high temperature; 5) pay attention to equipment noise or abnormal vibration; 6) observe lubricant leakage; 7) regularly sample lubricant and check whether it is contaminated.

II. Installation and Adjustment of Bearings

When assembling or installing, if the internal clearance of the bearing is too large or too small, or in some cases, the preloading load is too high, which may lead to early damage and shorten the life of the bearing. In addition to causing downtime and expensive maintenance, improper assembly and installation of bearings may have more negative effects, such as affecting the operation of other parts and shortening their service life. According to the manufacturer's manual, assembly, installation and regular maintenance are the best ways to prevent problems. If the time is very tight, the adjusting device can be pushed forward or the gasket can be removed to correct the loose conical rolling bearing group. On the other hand, too tight adjustment of bearings may lead to overheating damage and have to replace bearings. 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 the system performance. In addition, according to OEM requirements to use equipment, set appropriate predictive maintenance items such as the monitoring of lubricants or greases, which should include root cause analysis. In this way, even if there is a problem with the equipment, its normal operation time can be greatly extended. Correct lubrication and maintenance are very important, correct installation and use are also indispensable, and then make full use of existing status monitoring equipment escort. Failure to comply with installation and maintenance requirements will result in equipment failure and constitute a major safety hazard. Whether the bearing is installed correctly or not after installation has a direct impact on its life and the accuracy of the main engine. If installed improperly, bearings not only have vibration, noise, low accuracy, temperature rise increases, but also have the risk of being stuck and burnt out; conversely, good installation can not only ensure accuracy, but also greatly prolong life.

III. Inspection after Bearing Installation

After the bearing is installed, it must be inspected.

1. Inspection of Installation Location

After the bearing is installed, first check whether the running part and the fixed part collide, whether the lubricant can flow into the bearing smoothly, and whether the sealing device and the axial fastening device are installed correctly.

2. Inspection of radial clearance

Radial clearance shall be inspected except for bearings with pre-interference. Deep groove ball bearings can be inspected by hand rotation, so as to be smooth, flexible, no vibration, no left and right swing. Cylindrical roller and self-aligning roller bearing can be inspected by plug ruler. The plug ruler should be inserted between the roller and bearing ring. The insertion depth of the plug ruler should be greater than 1/2 of the length of the roller. When the radial clearance of the bearing can not be measured with a plug ruler, the axial displacement of the bearing can be measured to replace the reduction of the radial clearance. Usually, if the inner ring of the bearing is conical hole, the axial displacement on the conical surface is about 15 times that of the radial clearance reduction. The radial clearance of bearings, some of which are not qualified after installation, can be adjusted, such as angular contact ball bearings, tapered roller bearings; some of which have been adjusted in accordance with the standards during manufacture, and can not be adjusted after installation, such as deep groove ball bearings, self-aligning ball bearings, cylindrical roller bearings, self-aligning roller bearings, etc. If the radial assembly clearance of this kind of bearing is too small after installation, it indicates that the matching selection of the bearing is inappropriate or the assembly parts are not processed correctly. At this time, the bearings must be removed, the causes identified, and removed before reinstallation. Of course, too large bearing clearance can not be.

3. Inspection of bearing and shoulder tightness

Usually, the bearing that fits closely with interference installation must be close to the shoulder of the shaft. Inspection methods: (1) Lighting method. The lamp will be aligned with the bearing and shoulder, to see the light leakage judgment. If there is no light leakage, the installation is correct; if the light leakage is uniform around the shoulder, it means that the bearing is not close to the shoulder, the pressure should be applied to the bearing to make it close; if there is part of the light leakage, it means that the bearing installation is inclined, you can use the hammer, copper rod or sleeve to tap the inner ring of the bearing, and slowly correct. (2) Thickness gauge test. Thickness of gauge should start from 0.03mm. When inspecting, try inserting several places on the end face of bearing inner ring and the whole circumference of bearing shoulder, if there is a gap and it is very uniform, indicating that the bearing is not installed in place, the bearing inner ring should be pressurized to make it close to the shoulder; if the increase of pressure is not tight, it means that the fillet of the journal fillet is too big and the bearing is stuck, the journal fillet should be repaired. If it is found that the thickness gauge of the end face of the inner ring of the bearing and the individual parts of the bearing shoulder can pass, it means that the gauge must be disassembled, repaired and reinstalled at this time. If the bearing is installed in the bearing seat hole with 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 checked by thickness gauge.

4. Inspection of Thrust Bearing after Installation

When installing thrust bearings, the verticality of the shaft ring and the axis center line should be checked. The method is to fix the dial gauge on the end of the case, so that the contacts of the dial top the raceway of the bearing ring to rotate the bearing, while observing the dial pointer of the dial gauge, if the pointer is biased, the axis and the axis center line are not vertical. When the hole in the case is deep, it can also be inspected by a lengthened micrometer head. When the thrust bearing is installed correctly, its seat ring can automatically adapt to the rolling of the rolling element to ensure that the rolling body is in the upper and lower raceway. If the assembly is reversed, not only does the bearing work abnormally, but also the mating surfaces will suffer serious wear and tear. Since the difference between axle rings and seat rings is not obvious, special care should be taken in assembling so as not to make mistakes. In addition, there should be a gap of 0.2-0.5mm between the seat ring and the bearing seat hole of thrust bearing to compensate for the errors caused by inaccurate processing and installation of parts. When the center of the bearing ring is offset during operation, the gap can ensure its automatic adjustment, avoid contact friction and make it work normally. Otherwise, the bearing will be severely damaged.

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

Generally, the working temperature of bearings should be lower than 90 C. When the temperature is too high, it will lead to heating annealing or burning loss of bearings and reduce the service life.