1, improper mechanical installation, parts dislocation, preload
2, shaft alignment of bad
3, the machine geometry parameters (such as with the gap, the amount of interference and relative position) improper adjustment
4, the pipeline stress, the machine in the working state changed the dynamic characteristics and installation accuracy
5, the long-term improper placement of the rotor, the change of the dynamic balance accuracy is not in accordance with the rules and regulations, the destruction of the original nature and accuracy of the machine