1. After bearing installation, the necessary bearing adjustment cannot be overlooked
After the bearing is installed, add the specified lubricant and then conduct a test run to check for any abnormal noise and the bearing temperature.
The trial operation should be conducted under partial load conditions, and in cases where the speed range is wide, operation at medium to low speeds is recommended.
Under no circumstances should self-aligning roller bearings be started and accelerated to high-speed operation under no-load conditions, as the rolling elements may slide on the bearing raceway, damaging it, and the cage may also experience excessive pressure. Under normal conditions, the bearing will emit a uniform "rumbling" sound.
A whining or sharp, screeching sound from the bearing indicates insufficient lubrication.
A bearing emitting an uneven rumbling or knocking sound is mostly due to the presence of foreign objects in the bearing or damage sustained during the installation process.
The bearing temperature rises immediately after startup, which is a normal phenomenon.
For instance, in the case of grease lubrication, the bearing temperature will not decrease until the grease is evenly distributed inside the bearing, after which it will reach a balanced temperature.
Abnormally high temperatures or significant temperature fluctuations may indicate excessive lubricant inside the bearing, radial or axial deformation of the bearing, or insufficient clearance. Other causes include improper manufacturing or installation of related components, or excessive friction from seals.
During or immediately after the trial operation, the seals should be inspected to ensure they are functioning properly. Additionally, the lubrication equipment and oil levels in the oil reservoir should be checked. It may also be necessary to collect lubricant samples to determine whether the bearings are contaminated or if internal components are worn.
2. Usage factors and inherent factors affecting bearing lifespan
There are many factors that may affect the service life of self-aligning roller bearings, which can be further explained from both usage-related and inherent factors.
The primary factors involve whether installation, adjustment, usage, maintenance, and repairs comply with technical requirements.
According to the technical requirements for the installation, operation, maintenance, and care of self-aligning roller bearings, monitor and inspect the loads, rotational speed, operating temperature, vibration, noise, and lubrication conditions of the bearings in operation. If any abnormalities are detected, promptly identify the cause, make adjustments, and restore them to normal.
Installation conditions are one of the primary factors in usage considerations. Bearings often experience altered stress states among their components due to improper installation, leading to abnormal operation and premature failure of the entire bearing set.
The force applied during bearing installation can affect its performance and lifespan, and may even cause damage. Below are four key techniques to note during the installation process:
The force applied should be smooth and uniform, avoiding any impact. This requires the use of hydraulic tools or equipment capable of delivering steady tension or pressure. If hammering is absolutely necessary, softer metals such as copper sleeves should be used to cushion the impact, and the striking force should be as gentle as possible. It is preferable to use copper bars or hammers for hammering.
2. The force application should continue until the task is completed. For example, when installing a bearing, stop applying force precisely when the bearing reaches its correct position, ensuring that the end face of the ring (washer) rests against the seat hole or the shoulder end face of the shaft. The bearing should neither be pressed too tightly nor improperly installed.
3. The resultant force of the applied force should pass through the axis of the bearing as much as possible, which requires the application point to be uniform, symmetrical, and smooth, and applied through a spherical surface or parallel to the axis.
4. Avoid applying force through rolling elements, which requires applying force through the inner ring when installing and removing the inner ring (shaft ring), and applying force through the outer ring when installing and removing the outer ring.
As long as the force applied during the installation and removal of bearings is stable and uniform, without any impact, and the force should be applied continuously until the work is completed, there will be no damage to the bearings during installation.
The metallurgical quality of self-aligning roller bearing materials used to be the main factor affecting the early failure of self-aligning roller bearings. With the advancement of metallurgical technology, such as vacuum degassing of bearing steel, the quality of raw materials has been improved.
The proportion of raw material quality factors in bearing failure analysis has significantly decreased, but it is still one of the main influencing factors of bearing failure. Whether the material selection is appropriate is still a factor that must be considered in bearing failure analysis.
The manufacturing of self-aligning roller bearings generally involves multiple processing steps such as forging, heat treatment, turning, grinding, and assembly. The rationality, progressiveness and stability of each processing technology will also affect the service life of bearings.
The heat treatment and grinding processes that affect the quality of finished bearings are often more directly related to bearing failure. In recent years, research on the deteriorated layer on the working surface of bearings has shown that the grinding process is closely related to the surface quality of bearings.
The main task of analyzing the service life of self-aligning roller bearings is to identify the main factors causing bearing failure based on a large amount of background materials, analysis data, and failure forms, in order to propose targeted improvement measures, extend the service life of bearings, and avoid sudden early failure of bearings.
The vibration of self-aligning roller bearings can be divided into three types according to the direction of vibration:
1. Radial vibration. Vibration within the radial plane of the bearing ring.
2. Axial vibration. Vibration along the axis of the bearing.
3. Angular vibration. The oscillation of the radial plane of the ring relative to the diameter.
The vibration of self-aligning roller bearings can be divided into the following three types according to their generation mechanism:
1. Natural vibration of bearing structure
(1) Consider the outer ring as an inherent vibration caused by an elastic body.
(2) Consider the outer ring as an inherent vibration caused by the steel body.
(3) Consider steel balls as inherent vibrations of the steel body.
2. Forced vibration
(1) The rolling elements undergo vibration, which is caused by the period of the rolling elements passing through the load line during the operation of the bearing.
(2) Vibration caused by manufacturing errors in bearing components.
3. Impact vibration
When there are defects such as scratches, burrs, rust spots, pitting, peeling pits, and dust on the surface of the ring raceway or rolling element, it will excite the bearing pulse type vibration. The period of the pulse is inversely proportional to the speed, and the amplitude is related to the size of the defect.
The vibration of self-aligning roller bearings is often the result of the combined action of various types of vibrations mentioned above. Numerous experimental studies have shown that under normal bearing operation, the surface waviness of bearing components is the main factor causing bearing vibration.
