Bladder device and method for displacing air in a bottle bore shaft

A trapped air displacement device includes a flexible gas fillable bladder 30 and a device 34 for inserting the blader 30 into a bottle bore 8 of a turbine or generator shaft 14. The flexible bladder 30 displaces the air trapped in the bottle bore region 8, so that it will escape along the slightly tilted surface of the shaft 14. A protective tube 34 is provided for the fragile bladder 30 during positioning. The bladder 30 can be inflated through an inner tube 32. The bladder 30 can also be inflated by sealing a small amount of gas in the bladder 30 and tube 30 and applying a vacuum to the shaft 14.