Bolt rod stretching device and method for hydraulic disassembling and assembling impeller

The invention discloses a bolt rod stretching device and a bolt rod stretching method for a hydraulic disassembling and assembling impeller as well as a centrifugal compressor, which belong to the technical field of workpiece processing groups. The device comprises a spindle, a fixed ring and a cushion cover, wherein the spindle is a stepped shaft; a second through hole is formed in the center of the fixed ring, and the second through hole is a stepped hole; the spindle is arranged in the fixed ring, and a remaining containing space is left between a first shoulder and a second shoulder; the cushion cover is arranged between the second shoulder and a to-be-stretched impeller; the spindle, the fixed ring and the cushion cover are made of rigid materials; a third through hole is axially formed in the first section of the shaft, one end of the third through hole is used for injecting hydraulic oil, and the other end of the third through hole is communicated with the remaining containing space. The method is impl