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FAG Bearing Operation Inspection

Source:  skf bearing  Time:  2023-09-26

FAG bearings (especially rolling bearings) are of two types with cage and without cage. Among them, large-scale FAG bearings are generally required to withstand larger loads, often without a cage, but filled with rolling elements between the inner and outer raceways. And most of the small and medium rolling bearings are with cages.


In the processing process of FAG bearings, how are the outer ring, inner ring, rolling element and cage of the bearing assembled together? Simply put, first put the inner and outer rings of the FAG bearing, put the inner ring aside, then put the rolling elements (put aside), then adjust the position of the rolling elements, and finally, put the cage. Now everyone knows that cages are involved in the processing of FAG bearings. So what is the main role of FAG bearing cages?

The role of the cage is:


1. Guide and drive the rolling elements to roll on the correct raceway;


2. The cage separates the rolling elements at equal distances and is evenly distributed on the circumference of the raceway to prevent collision and friction between the rolling elements during work;


3. In the separable bearing, the rolling element and a ferrule are combined to prevent the rolling element from falling off.

Bearings are called windows, which are used to isolate and guide the rolling elements. The pocket gap allows the cage to have a certain amount of movement in the radial and axial directions. The total amount of movement in the radial direction is called the cage gap. The roller cage has a variety of structural types and complex shapes. There are many equidistant pockets on the cage. The shapes of the pockets are spherical, round, elliptical, rectangular and toothed. The size of the pockets is larger than the size of the rolling elements. The difference between the two is the pocket gap. Sometimes the FAG bearing cage The connecting part between the windows is called the lintel, which plays a role in connecting and increasing the strength of the cage.
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After the FAG bearing is installed, in order to check whether the installation is correct, a running check is required. Small machines can be rotated by hand to confirm whether they rotate smoothly. The inspection items include improper operation due to foreign objects, scars, and indentations, unstable torque due to poor installation and poor processing of the mounting seat, excessive torque due to too small clearance, installation errors, and seal friction, etc. Wait. If there is no abnormality, power operation can be started.


Large-scale machinery cannot be rotated manually, so immediately cut off the power after starting without load, and the machinery is idling. Check for vibration, noise, and contact with rotating parts. After confirming that there is no abnormality, enter the power operation.


The power operation starts at a low speed with no load and slowly increases to the rated operation under the specified conditions. The items to be checked during the test run are whether there is abnormal sound, bearing temperature change, lubricant leakage or discoloration, etc. If an abnormality is found, stop the operation immediately, inspect the machine, and remove the bearing for inspection if necessary.


Bearing temperature can generally be estimated based on the external temperature of the bearing seat. However, it is more accurate to use the oil hole to directly measure the temperature of the bearing outer ring. The temperature of the bearing gradually increases from the start of operation, and usually stabilizes after 1 to 2 hours. If the bearing is installed improperly, the temperature will rise sharply, resulting in abnormally high temperature. The reasons include too much lubricant, too small bearing clearance, poor installation, and too much friction in the sealing device. In the case of high-speed rotation, the wrong choice of bearing structure and lubrication method is also the reason.


The rotating sound of the FAG bearing is checked with a stethoscope, etc., there are strong metal noises, abnormal sounds, irregular sounds, etc., indicating abnormalities. The reasons include poor lubrication, poor shaft or bearing seat accuracy, bearing damage, and foreign matter intrusion.

Common faults of bearings are as follows:


1. Corrosion of tile surface: Spectral analysis found that the concentration of non-ferrous metal elements is abnormal; there are many sub-micron wear particles of non-ferrous metal components in the iron spectrum; the moisture of lubricating oil exceeds the standard, and the acid value exceeds the standard.


2. Strain on the journal surface: there are iron-based cutting abrasive particles or black oxide particles in the iron spectrum, and there is a tempering color on the metal surface.


3. Corrosion of journal surface: Spectral analysis found that the concentration of iron is abnormal, there are many sub-micron particles of iron in the iron spectrum, and the moisture or acid value of the lubricant exceeds the standard.


4. Surface strain: cutting abrasive particles are found in the iron spectrum, and the abrasive particles are non-ferrous metals.


5. Fretting wear of tile back: Spectral analysis found that the iron concentration is abnormal, there are many iron submicron wear particles in the iron spectrum, and the lubricant moisture and acid value are abnormal.


Under liquid lubrication conditions, the sliding surface is separated by lubricating oil without direct contact, and friction loss and surface wear can be greatly reduced. The oil film also has a certain vibration absorption capacity.