1. Power frequency vibration caused by eccentric load of gear. The speed of the turbine is very high, the speed of 1-2 stages is 15200rpm, the speed of 3-4 stages is 19200rpm. It is very important to keep a high gear contact surface. It is impossible to get the dynamic actual contact condition by checking the gear contact surface under static state. Our method is to make the contact surface not less than 85% under static state. During the maintenance of one unit, it was found that the contact surface of the gear was poor, and a new gear had serious pitting corrosion and big tooth surface spalling after only running for more than two months (the current price of a big tooth is about 300000 yuan). The vibration of the unit is very large, and the damage of the gear is in a vicious circle, which is difficult to save.
2. Low frequency vibration caused by oil whirl. The oil film in the bearing plays the role of transportation and lubrication between the shaft and the bearing. If the stability of the bearing is not good, the oil film will whirl at half speed. The speed of the third turbine is 19200, which produces low frequency vibration at about 10000. Low frequency vibration produces the exciting force which is out of step with the working speed of the rotor. Its influence on the life of the rotor and shaft is greater than that of the power frequency vibration. It increases the total vibration of the rotor, which has always been taboo. If the low frequency value is 105 times of the power frequency value, attention should be paid to it. The low frequency value of our original machine is more than 5% of the power frequency value, which has caused serious consequences. The tin base alloy of the bearing bush peeled off many times (actually bumped down) and was forced to shut down. One piece of stage 2 rotor cracked (13442 hours in total), about 1.5mm2, and the shaft head of stage 3-4 rotor cracked (11000 hours in total). It will cost hundreds of thousands to replace two rot
