1. Axial displacement
The axial displacement of the steam turbine rotor. The axial displacement index is used to monitor the working condition of the thrust bearing. The axial thrust acting on the rotor is borne by the thrust shaft, thus ensuring a reliable axial clearance between the dynamic and static parts of the unit. Excessive axial thrust or abnormal operation of the thrust bearing itself will cause the burning of the thrust pads, causing damage to the equipment caused by dynamic and static parts of the steam turbine.
Turbine steam temperature is low or the cylinder will generate huge axial thrust when it is fed into the water. For the reheat unit with reverse arrangement of high and medium pressure cylinders, due to water impact accidents, the instantaneous increase of axial thrust occurs in the high pressure cylinder Inside, that is, the axial thrust direction is consistent with the steam flow direction in the high-pressure cylinder, so the working surface of the thrust pad will bear huge axial force.
When the temperature of the reheated steam is reduced or the medium pressure cylinder is filled with water, the direction of the thrust force is consistent with the steam flow direction of the medium pressure cylinder. At this time, the non-working surface of the thrust tile will bear a huge axial force. In addition, when the vacuum is low or the flow-through part is fouled, the axial thrust will change greatly.
During the operation of the unit, when the axial displacement is found to be increased, the turbine should be fully inspected, listen to the internal sound, measure the bearing vibration, and pay attention to monitor the change of the thrust pad temperature and the return oil temperature. Generally, the thrust pad urinary temperature is normally not allowed to exceed At 85 ℃, the thrust pad's black metal temperature exceeds 107 ℃, it should be decisively shut down. The oil return temperature is not allowed to exceed 71 ℃. When the temperature exceeds the specified allowable value, even if the string shaft indication is not large, the load should be reduced to restore it to normal. If the tandem shaft indication exceeds the allowable value and the protection action is triggered, the generator should be immediately asked to stop and stop. When the indication value of the string shaft exceeds the allowable value, and the protection refuses to act, it should be carefully checked and judged. When the indication value is confirmed to be correct, emergency stop measures should be taken quickly.
The main reasons for the increase of axial thrust during steam turbine operation are:
(1) Steam temperature and steam pressure drop;
(2) The gap between the diaphragm seal and the seal increases due to wear;
(3) Poor steam quality, causing scaling in the flow section;
(4) A water shock accident occurred;
2. Bearing bush temperature
The turbine shaft rotates at high speed in the bearing bush, which causes the temperature of turbine oil and bearing bush to rise. When the bearing bush temperature is too high, it will threaten the safety of the bearing. The method of monitoring the temperature rise of the lubricating oil is usually used to indirectly monitor the temperature of the bearing bush. Because the temperature of the bearing bush increases, the heat transferred to the lubricating oil also increases, and the temperature rise of the lubricating oil increases. The temperature rise of general lubricating oil should not exceed 10 ～ 15 ℃. However, the temperature rise of the lubricating oil alone is not only slow, but also unreliable. Often the bearing bush has been burned, but the oil return temperature has not changed significantly, especially the thrust bearing bush, which is not significant. Therefore, the best way is to directly monitor the Ujin temperature of the bearing shell. The oil return temperature of each bearing of the steam turbine is normally not more than 77 ℃, and it should be decisively shut down if it exceeds 113 ℃. In order to make the bearing work normally, the oil temperature of the bearing is clearly specified. Generally, the oil temperature of each bearing is 38 ～ 45 ℃.