In order to ensure the PTA device safety、stable and long running, it realize the long period of the equipment running data by implementing on-line monitoring for PTA device, and it provides convenience for capture vibration information. In this paper, it dissected the vibration mechanism of dynamic imbalance fault, and summarized the signal characteristics to some extent, based on that, it identifies the sudden imbalance fault (broken blade) twice of the steam turbine, then, it puts forward the valuable guidance to the enterprise production in time. Results indicate that: (1) this provides the basic knowledge for fault diagnosis by researching the vibration mechanism and fault characteristics; (2) this narrows the harm and economic loss of the big unit accident by detecting and solving fault early; (3) this provides effective protection for predicting maintenance management by on-line monitoring. This paper reflected many advantages of the online monitoring and fault diagnosis, such as timeliness, full cyclical, and convenient, etc., so it should be widely available to engineering practice.
