After the installation of NTN imported bearings is completed, in order to check whether the installation is correct, a running inspection is required. Small machinery can be rotated by hand to confirm whether it rotates smoothly. The inspection items include poor operation due to foreign objects, scratches, and pressure marks, unstable torque due to poor installation, 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 machinery cannot be rotated manually, so the power is cut off immediately after no-load start, the machine is idling, check whether there is vibration, noise, whether the rotating parts are in contact, etc. After confirming that there is no abnormality, enter the power operation.
The power operation starts from the no-load low speed and gradually increases to the rated operation under the specified conditions. The items to be checked during the trial operation are whether there is abnormal sound, temperature change of NTN imported bearings, leakage or discoloration of lubricant, etc. If an abnormality is found, the operation should be stopped immediately, the machine should be inspected, and the bearing should be removed for inspection if necessary.
NTN imported bearing temperature can generally be estimated based on the external temperature of the bearing housing. However, it is more accurate to use the oil hole to directly measure the temperature of the outer ring of the bearing. The bearing temperature gradually increases from the start of operation, and the temperature is usually stable after 1 to 2 hours.
If the bearings are not properly installed, the temperature will rise sharply and abnormally high temperatures will appear. The reasons are too much lubricant, bearing clearance is too small, poor installation, excessive friction of the sealing device, etc. In the case of high-speed rotation, the choice of NTN imported bearing structure and lubrication method is also the reason.
The rotation of NTN imported bearings is checked with a stethoscope, etc., and there are strong metal noises, abnormal sounds, irregular sounds, etc. that are abnormal. The reasons are poor lubrication, poor precision of the shaft or bearing housing, bearing damage, foreign matter intrusion, etc.
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Common faults of NTN imported bearings are as follows:
1. Corrosion of the tile surface: Spectral analysis found that the concentration of non-ferrous metal elements is abnormal; many sub-micron wear particles of non-ferrous metal components appear in the iron spectrum; the moisture content of the lubricant exceeds the standard and the acid value exceeds the standard.
2. Strain on the surface of the journal: There are iron-based cutting abrasive particles or black oxide particles in the iron spectrum, and the tempered color exists on the metal surface.
3. Corrosion of journal surface: Spectral analysis found that the concentration of iron is abnormal. There are many submicron particles of iron in the iron spectrum. The moisture content of the lubricant exceeds the standard or the acid value exceeds the standard.
4. Surface strain: cutting abrasive particles are found in the iron spectrum, and the abrasive particles are made of non-ferrous metals.
5. Fretting wear on the back of the tile: Spectral analysis found that the iron concentration is abnormal. There are many iron components with submicron wear particles in the iron spectrum, and the moisture and acid value of the lubricating oil are abnormal.
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.