Bearing life cycle
Investigating the effective factors in bearing life and the life cycle of all types of bearings from the stage of purchase to mounting and dismounting from the device:
All industries, whether small or large, use rolling bearings in their common and widely used types, such as bearings, needle roller bearings, cylindrical roller bearings, and conical roller bearings. Bearings have very high sensitivity and delicacy both in construction and in use, and in this sense, they are very vulnerable. The art of reputable machine designers and manufacturers is to use bearings that have high reliability in the conditions of speed, load and working temperature of the machine. In other words, the life of the bearing reaches its maximum length in the working conditions of the machine.
Although the lifespan of the bearing can be assumed to be unlimited theoretically and in ideal conditions, it is limited in real conditions and needs to be replaced. The art and duty of machine owners and people responsible for the maintenance and repairs of industrial units should be to take proper care of the bearings in order to use their maximum life in the working conditions of the machine and machine.
In the bearing life cycle, important steps can be identified, each of which has a significant impact on its life. These steps include: installation (mounting and initial lubrication), alignment, re-lubrication, condition maintenance and removal (replacement).
In order to prolong the life cycle of the bearing, or in other words, to use the maximum life of the bearing, it is necessary to use the appropriate equipment along with upgrading the technical level of the people involved with it along with training. Extending the life cycle of bearings reduces downtime, reduces repairs, reduces costs, increases production, and increases revenue and profit. In the following, we will briefly explain each of the stages in the bearing life cycle:
Bearings should be selected from reputable manufacturers and purchased from qualified suppliers or dealers. The buyer of bearings should keep these things in mind:
1. The quality and lifespan of bearings is the main reason for the price difference in bearings of the same type and different brands. By buying a cheap bearing, you should not expect a long life from it. Hamed Bearing Trading Company is one of the suppliers of all kinds of bearings in the country’s industry, which by prioritizing quality has been able to market its products at a reasonable price.
2. Bearings made by reputable manufacturers have a manufacturing date, and it should be ensured that new bearings are purchased. The older the bearing is, the more likely it is to rust and damage its components during storage and frequent movements, so its lifespan will be very short. Hamed Bearing Trading Company has started to insert the production date on its products. You can read here how to read the date of its bearings.
3. Unfortunately, the market of non-genuine and fake bearings is very hot in the country, and the purchase of such bearings from non-reputable sellers has also increased every day; The best way to buy bearings is to prepare an annual shopping list and sign a contract with a reliable supplier.
4. The bearing should be purchased and delivered in a safe wrapper with a protective material and safe packaging and the correct technical number, and should be carefully transported and stored until the time of use, and the warehouse officials or others should not be allowed to open the packaging and the bearing wrapper. Have.
Mounting (installation) and initial lubrication
It is a stage that is the only existing, interesting and important stage for most of the technical officials of the industries. But from a fundamental point of view, it is only one of the main and effective steps in the life of the bearing. The important points at this stage are:
1. The seat of the bearing on the shaft and inside the housing should be carefully inspected before starting the installation operation. Common inspections include: checking the tolerance of shaft and housing diameter compatibility with the inner and outer diameter of the bearing, the flatness of the shaft, the roundness of the shaft and housing. The installation operation should be started after ensuring the proper condition of the axle and housing.
2. The environment of the workshop or the room where the bearing is installed must be very clean. Any kind of pollution such as air dust, presence of pleats and shavings caused by grinding and welding operations, contaminated work table and tools, contaminated grease, as well as contaminated hands will all cause contamination to enter the bearing and reduce the life of the bearing.
3. The bearing should be removed from its packaging and wrapper only when starting the installation.
4. Depending on the type and size of the bearing, one should choose one of three methods: cold (mechanical), hot, and hydraulic, and use the basic tools of each method. The mechanical method is recommended for bearings with a maximum outer diameter of 100 mm. Hitting the bearing incorrectly in order to install it and heating it more than 120 degrees Celsius in contaminated oil is one of the common methods in the country’s industry that causes the most damage to bearings and machines.
5. It is very important to maintain the proper clearance after installing the bearing components in the way the bearing works and its lifespan. The amount of slack should be taken from the manufacturers’ technical tables according to the type and specifications of the bearing. In general, the residual slack after installation for all types of bearings (other than the self-adjusting type) as well as conical roller bearings is zero and for cylindrical and spherical roller bearings, taking into account the operating temperature, it is within hundredths of a millimeter and should be Choose the correct one according to the manufacturer’s guide tables and observe it in the bearings (by measuring).
6. It is necessary to completely fill the bearing with suitable and clean grease immediately after it is installed and placed in its place on the shaft and housing.
Bearing alignment with the device
After installing the bearing and before starting the device or machine, the axis of the moving machine must be aligned with the axis of the device or driving machine that are coupled to each other within the permissible limit. Three common methods of alignment are:
1. an eye
2. Measuring hours
3. Laser alignment
Because in most of the country’s industries, due to the lack of specialized people and suitable equipment, eye alignment is used, which is associated with a lot of error, we always see the following major disadvantages and problems:
1. Uneven and excessive load application to the bearings on both sides of the coupling and their very fast erosion
2. increase in friction and, as a result, the operating temperature of devices and energy loss (excessive consumption of electricity up to 15%)
3. Creating or increasing the vibration of devices and accelerating failures to other machine components
The best alignment method, which achieves the highest speed and accuracy and helps greatly in increasing the life of the bearing, is the laser alignment method. After ensuring that the axis of the driving device is aligned with the moving device within the permissible limit, the devices can be safely inserted into the circuit. The manufacturer of each device is obliged to determine the permissible limit of misalignment of his device.
Working and staying healthy of the bearing depends on the presence of lubricant at all times and the creation of an oil film between its contacting surfaces. The thickness of the oil film in the bearings is between 0.1 and 1 micron, which can be created with an oil viscosity between 100 and 400 stock cents at a temperature of 40 degrees Celsius. The loss of the oil film for any reason and for a fraction of a second leads to serious damage and a sharp reduction in the life of the bearing. Grease, which makes up 90% of its volume is oil, is one of the lubricants produced in different types and is used in 95% of the machines in the industry to lubricate the bearings.
Correct lubrication of bearings is determined by three factors:
1. Apply proper and clean grease
2. Proper time interval between two greases
3. Exact amount of grease to be applied at each re-greasing time
In the absence of the device manufacturer’s recommendation on the amount of grease for each re-greasing, the following relationships can be used:
(Gp is in grams, D is the outer diameter of the bearing in millimeters and B is the width of the bearing in millimeters)
Gp=0,005DB if the grease enters from one side of the bearing
Gp=0,002DB if the grease enters from the middle of the outer ring of the bearing
Filling (saturating) the place of the bearing in machines is a misconception that always governs lubrication in the country’s industry. The increase in friction due to excess grease causes an increase in the temperature of the grease and bearing, and as a result, the viscosity and thickness of the oil film at the contact points. The working bearing is reduced, which causes wear and tear and a reduction in the life of the bearing.
Bearing condition care
Regular inspection and awareness of the condition of working bearings, which is done by using basic condition monitoring and measuring temperature, noise and vibration, is of particular importance. These regular measurements and checks on it help to detect the breakdown process and prevent the continuation of breakdowns and unwanted stops of machines with timely measures. In addition, it provides the possibility to plan the stopping of the machine at the right time, which will result in an increase in the efficiency and production of the factory.
Removing the bearing from the device
In any case, the life of the bearing will end and must be replaced. Although the defective bearing cannot be reused, its correct removal is very important at least for the safety of people. In addition, the use of appropriate removal tools and equipment prevents damage to other machine components such as axles and housings. Sometimes it is necessary to temporarily remove the healthy bearing in front of it to replace the gear or other components. In this case, the bearing must be removed with great care and using the correct methods and tools to prevent it from being damaged for reuse. It is recommended to inspect the bearing after removing the bearing if its failure was premature, so that corrective and preventive measures can be taken to avoid future failures after determining the causes of the failure.
These important stages in the life cycle of the bearing should be taken into consideration because each of them has an important and significant role in reaching the maximum lifespan of the bearing. Definitely, this cannot be achieved without training and using correct maintenance methods and appropriate tools.
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