1) Problems in the selection of lubricating oil: The rotor bearing is lubricated with grease, and the indicators of the grease can meet the stable operation of the bearing. There is no problem with the selection of grease, and it can be excluded.
(2) The problem of lubricating oil pollution: open the bearing end cover to check, the grease is clean, and there is no impurities such as ash entering, so as to eliminate this problem and cause the bearing to heat up.
(3) Excessive addition of grease in the bearing: Under normal circumstances, excessive grease will cause poor heat dissipation of the bearing and cause the bearing to heat up. There is an oil drain hole at the lower end of each bearing seat end cover of the crusher rotor. Excessive addition of grease will cause the temperature to rise in a short time. After running for a period of time, the old grease is discharged, and the bearing temperature will return to normal. The bearing of the crusher runs at a high temperature of around 85 ℃ all the year round, which should not be caused by this reason.
(4) Bearing assembly: Open the outer end cover of the free end bearing for inspection, measure the distance from the outer ring of the bearing to the side of the bearing seat to be 26.3mm, and measure the length of the end cover of the bearing to be 30mm.
Comparing the two data, the problem of bearing heating was confirmed. It was because the outer end cover of the free end bearing was pressed too tightly, the end cover lip was tightly pressed on the outer ring of the bearing, and the rotor shaft had no thermal expansion, which caused the bearing to heat up.
(5) Calculation of thermal expansion of rotor shaft: the center distance of the bearings at both ends is 3400mm, the working temperature difference is 100℃, the expansion coefficient of ordinary carbon steel is 1.2×10-5/℃; the expansion amount is 4.08mm (3400mm×100℃×1.2 ×10-5/°C).
When the limestone crusher is working normally, the thermal expansion of the rotor shaft is 4.08mm. When the rotor is running, the bearing temperature will gradually rise, the rotor shaft will also be elongated, and the free end bearing will produce axial displacement with the temperature change.
Taking into account the error of assembly size and other errors, during the installation process of the rotor, a distance of more than 10mm should be reserved between the outer end cover of the free end bearing and the outer ring of the bearing to ensure the thermal expansion of the rotor shaft during the normal production process. High temperature caused by axial force, long-term operation, the bearing will be damaged.
Therefore, the problem of floating clearance is the root cause of the long-term high temperature operation of the bearing.
Solutions
Through the above analysis, the main reason for the heating of the bearing is the absence of axial thermal expansion of the free end bearing, which can be solved by adjusting the gap between the bearing outer ring and the stop of the bearing end cover.
There are two solutions, one is to remove the bearing end cover by 10mm; the other is to add a gasket to move the bearing end cover outward. According to the situation on site, the second method is adopted, which is to obtain materials on the spot, make a washer with 10mm old rubber tape on site, and install it between the outer end cover of the free end bearing and the bearing seat to ensure that the rotor has sufficient expansion during operation.
