When starting a large unit, vibration occurs mostly in the medium-speed warm-up and its front and rear speed-up phases, especially during the critical speed, the unit vibration will increase significantly. At this stage, if the vibration is large, it is most likely to cause friction between dynamic and static parts, wear of the seal, and bending of the rotor. Once the rotor is bent, the vibration becomes larger and larger, the greater the vibration, the more severe the friction. Such a vicious cycle can easily cause permanent deformation and bending of the rotor, causing serious damage to the equipment. Therefore, during the warm-up or speed-up process, if there is a large vibration, it should be immediately braked and stopped, and the straight shaft of the car should be cranked to eliminate the cause of the vibration, and then restart the unit.
After the unit is connected to the grid at full speed, every 10,000 loads increase, the steam flow changes greatly, the internal temperature of the metal rises quickly, and the main steam temperature is not well matched. The metal inner and outer walls are most likely to cause a large temperature difference, causing the unit to vibrate. Therefore, each time a certain load is added, the machine needs to be warmed up for a period of time to gradually and uniformly heat the unit.
In summary, during the unit's speed increase and load process, the vibration of the turbine must be monitored frequently.