With the running time of air compressor host goes on, each bearing will wear, thus causing the screw axial movement and radial displacement of initiation increased, the changes will make the void between the screw and screw, screw and the host shell and the front end and the back end of the change. These gaps changes is normal, permitted in bearing life in the time line, and thus the initiation of the air compressor production mind decay load and main motor increase permit is normal, the. With the unit running time close to the overhaul period, the host of the bearing life gradually hasten to the maximum allowed the deadline. This screw axial and radial runout gradually hasten to the maximum allowed value of presupposition, this change will make the gap between the screw and the screw rod screw, and the casing of the host computer and the front end and the back end of the changed greatly. At this point the host running is decided to be safe, but has reached must consider planning for the implementation of resettlement host overhaul time. Since the running time is a unit through the overhaul period, bearing wear and host the appropriate gap to the limit allowed to host the technical conditions of the value, at this time of the host in the operational status of unsafe, any time may occur following the serious consequences: the host running load increases, cause harm to the main motor and electrical system