After the bearing is installed in the main engine, if the radial runout of the spindle is measured, it can be found that there is a certain change in the measured value of each rotation; when continuous measurement is carried out, it can be found that after a certain rotation, the change will approximately repeat. The index to measure the degree of change is the accuracy of cyclic rotation. The rotation needed to repeat approximately represents the "quasi-period" of the accuracy of cyclic rotation. The magnitude of change in the quasi-period is large, that is, the accuracy of cyclic rotation is poor.
If proper preload is applied to the spindle, the rotational speed will be gradually reduced to close to the compulsory rotational speed, so as to implement the "running-in" function of the bearing, the rotational accuracy of the spindle can be improved.
The main factors used for adjustment are installation, use and maintenance, maintenance, etc. which meet the technical requirements. According to SKF bearing installation, use, maintenance and technical requirements of operation of bearing contact load, speed, temperature, vibration, noise and lubrication status monitoring and inspection, find abnormal causes immediately, adjust, make it back to normal. Installation condition is one of the main factors for using bearings. It is the primary factor that often causes the state change between the parts of the incorrect installation package. It terminates in abnormal operation condition and life ahead of schedule.
Internal factors mainly refer to structural design, quality of manufacturing technology and materials, three factors determine the quality of bearings.
The metallurgical quality of bearing materials is the main factor affecting the early failure of rolling bearings. With the progress of metallurgical technology (such as bearing steel, vacuum degassing, etc.), the quality of raw materials has been improved. The proportion of raw material quality factor in bearing failure analysis has been significantly reduced, but it is still one of the main factors of bearing failure. Whether the selection is appropriate or not is still a bearing fault analysis that must be considered.
Bearing manufacturing will undergo multi-process operation of forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of the treatment will also affect the service life of the bearing. Influencing the heat treatment and grinding process of bearings is often more directly related to the failure of bearings related to product quality. In recent years, the research on the deterioration of bearing surface layer shows that the grinding process is closely related to the bearing surface quality.
The main task of SKF bearing service life analysis is to find out the main factors causing bearing failure based on a large number of background materials, data and failure mode analysis. Therefore, improvement measures are proposed to extend the service life of bearings in order to avoid sudden bearing failure in the early stage.
Power operation, starting from no-load low-speed, slowly increased to the rated operation of the specified conditions. The inspection items during commissioning are whether there is abnormal sound, bearing temperature change, lubricant leakage or discoloration, etc. If any abnormality is found, the operation shall be stopped immediately, the machinery shall be inspected, and the bearings shall be removed if necessary for inspection.
Bearing temperature can generally be inferred from the external temperature of the bearing seat. But it is more accurate to measure the temperature of bearing outer ring directly by using oil hole. Bearing temperature, from the start of operation gradually increased, usually 1 to 2 hours after the temperature is stable. If the bearing is not installed properly, the temperature will rise sharply and abnormal high temperature will occur. The reasons include too much lubricant, too small bearing clearance, poor installation, too much friction of sealing device and so on. In the case of high-speed rotation, the wrong choice of bearing structure and lubrication mode is also the reason.
SKF bearings rotate sound with stethoscope and other examinations, there are strong metal noise, abnormal sound, irregular sound and so on to explain the abnormality. The causes include poor lubrication, poor precision of shaft or bearing seat, bearing damage, foreign body intrusion, etc.
The common faults of bearings are as follows:
1. Tile surface corrosion: Spectral analysis found that the concentration of non-ferrous metal elements was abnormal; many sub-micron wear particles of non-ferrous metal components appeared in ferrography; lubricating oil moisture exceeded the standard, acid value exceeded the standard.
2. Surface pull of journal: There are iron series cutting abrasive particles or black oxide particles in Ferrography and tempering color on metal surface.
3. Surface corrosion of axle neck: Spectral analysis found that the concentration of iron was abnormal. There were many sub-micron particles of iron in ferrography, and the water content of lubricating oil exceeded or the acid value exceeded the standard.
Under the condition of liquid lubrication, the sliding surface is separated by lubricating oil without direct contact, and the friction loss and surface wear can be greatly reduced. The oil film also has a certain vibration absorption capacity.
