1. Regular inspection
In order to fully utilize the bearing and maintain its performance for a long time, regular maintenance (regular inspection) must be carried out. It is very important to improve productivity and economy by properly discovering faults early and preventing accidents before they happen.
1.1 Cleaning
When removing the bearing for inspection, first use photography and other methods to record the appearance. In addition, confirm the amount of remaining lubricant and sample the lubricant bearing.
a. The cleaning of the bearing is divided into rough cleaning and fine cleaning, and a metal grid can be placed at the bottom of the container used.
b. During rough cleaning, use a brush to remove grease or adhesive in the oil. At this time, if the bearing is rotated in the oil, be careful that the bearing will be damaged by foreign matter.
c. During fine cleaning, slowly rotate the bearing in the oil and it must be done carefully.
The cleaning agent commonly used is neutral water-free diesel or kerosene, and sometimes warm alkali solution is used as needed. No matter which cleaning agent is used, keep it clean. After cleaning, apply anti-rust oil or anti-rust grease to the bearing immediately.
1.2 Inspection and judgment
1.2.1 Bearing fault identification method
Bearing maintenance and care can identify or predict whether the bearing in operation has faults without disassembly inspection, which is very important for improving productivity and economy. The main methods are as follows:
a. Identification by sound
Identification by sound requires rich experience. It must be fully trained to be able to identify bearing sounds and non-bearing sounds. This work is done by a dedicated person. The sound of the bearing can be clearly heard by sticking a listening device or listening stick on the shell.
b. Identification by working temperature
This method is a comparative identification method and is limited to occasions where the operating state does not change much. For this reason, continuous temperature recording must be carried out. Not only does the temperature rise, but irregular changes will also occur.
c. Identification by the state of the lubricant
The lubricant is sampled and analyzed, and the degree of contamination is judged by whether it is mixed with foreign matter or metal powder. This method is particularly effective for bearings that cannot be observed closely.
1.2.2 Bearing Inspection
Inspect the bearings that are disassembled during regular maintenance, operation inspection and replacement of peripheral parts of the equipment to determine whether they can be used again. Carefully investigate and record the disassembled bearings and their appearance. In order to clarify and investigate the remaining amount of lubricant, clean the bearings by sampling.
Secondly, check the conditions of the raceway surface, rolling surface and matching surface, as well as the wear state of the cage for damage and abnormal conditions. To determine whether the bearing can be used again, the inspection results should be considered after considering the degree of bearing damage, machine performance, importance, operating conditions, inspection cycle, etc. If the bearing is found to be damaged and abnormal, the contents of the damage section should be used to find out the cause and formulate countermeasures. In addition, if the inspection results show several defects on the surface, the bearing cannot be used again and needs to be replaced with a new bearing.
a. Any of the inner and outer rings, rolling elements, and cages has cracks and fragments.
b. Any of the inner and outer rings and rolling elements has peeling.
c. The raceway surface, ribs, and rolling elements have significant carding.
d. The cage is severely worn or the rivets are loose.
e. The raceway surface and rolling element are rusted and scratched.
f. There are significant indentations and marks on the rolling surface and rolling element.
g. There is creep on the inner diameter surface of the inner ring or the outer diameter of the outer ring.
h. Severe discoloration due to overheating.
i. The seal ring and dust cover of the grease-sealed bearing are seriously damaged.
2. Shutdown inspection
Regular inspection of the bearing seal is very important to keep the bearing in good condition. The favorable inspection time is arranged in the regular shutdown inspection plan and knowing the bearing model and having bearing spare parts is usually done by inspection.
2.1 It is important to keep the bearing and lubrication clean.
Before inspection, clean the machine surface and then disassemble the parts around the bearing. Oil seals are very fragile parts, so they need to be carefully disassembled, cut, and then carefully inspected. If they show any bad symptoms, they must be replaced. Bad oil seals will damage and seriously shut down the equipment.
2.2 Check lubricant
Apply a little lubricant and rub it between two fingers. If there is contaminant, you can feel it, or apply a thin layer of lubricant on the back of your hand.
2.3 Replace lubricant
After draining the old oil from oil-lubricated bearings, if possible, fill in fresh oil and let the machine rotate at low speed for a few minutes. Collect the remaining contaminants as much as possible, and then drain the oil. The oil should be filtered before use.
When replacing the grease of grease-lubricated bearings, avoid using cotton to contact any part of the bearing with the cleaner, because these residues can wedge between the rolling parts and cause damage, especially for small bearings.
2.4 Cover exposed bearings
When inspecting bearings, never expose the bearings to contaminants or moisture. If work is interrupted, use oil paper, plastic sheet or similar.
If cleaning an uncovered bearing where inspection is possible without disassembly, use a coating brush dipped in petroleum solvent, wipe dry with a lint-free cloth or blow dry with compressed air (be careful not to start the bearing assembly). Use a small mirror and a probe similar to that used by dentists to check the bearing raceway, retainer and beads. If the bearing is not damaged, relubricate as recommended by the lubrication instructions provided by the original manufacturer.
Do not clean bearings with sealing covers or dustproofs; only wipe the outer surface. If the bearing is damaged, it needs to be replaced. Replacing the bearing within the maintenance period is much more economical than the loss of sudden downtime caused by bearing damage.
3. Inspection and troubleshooting during operation
The inspection items during operation include the rolling sound, vibration, temperature, lubrication status of the bearing, etc. Among them, the rolling sound and vibration of the bearing are as mentioned above. Here, lubrication is introduced as follows:
3.1 The role of bearing lubrication
Lubrication has an important impact on the fatigue life, friction, wear, temperature rise, vibration, etc. of rolling bearings. Without normal lubrication, the bearings cannot be damaged. The reasons for bearing damage show that about 40% of bearing damage is related to poor lubrication. Therefore, good lubrication of bearings is an effective measure to reduce bearing damage. In addition, bearing lubrication also has many functions such as heat dissipation, rust prevention, sealing, and impact mitigation. The functions of bearing lubrication are as follows:
a. A layer of oil film is formed between the two rolling surfaces or sliding surfaces in contact with each other to separate the two surfaces, reducing the friction and wear of the contact surfaces
b. When oil lubrication is used, especially when circulating oil lubrication, oil mist lubrication and oil spray lubrication are used, the lubricating oil can take away most of the inside of the bearing to achieve effective heat dissipation.
c. When grease lubrication is used, it can prevent external dust and other foreign matter from entering the bearing and play a sealing role.
d. Lubricants have the function of preventing metal corrosion.
e. Extend the fatigue life of bearings.
