Rotary machine with adjustable leakage gap

A rotary machine for acting on a process fluid, comprising:

• an impeller configured to act on the process fluid;
• a shaft, on which the impeller is mounted;
• a drive operatively connected to the shaft and configured to rotate the shaft and the impeller about an axial direction;
• a seal having a sealing element sealing the shaft during rotation of the shaft;
• and
• a flush casing configured to receive a flushing fluid for flushing the sealing element, the flush casing delimiting an annular flush chamber extending about the sealing element, and the flush casing comprising a bushing surrounding the sealing element and delimiting a radial leakage gap arranged between the sealing element and the bushing, the bushing arranged and configured to delimit an axial leakage gap between the impeller and the bushing, and the width of the axial leakage gap in the axial direction being adjustable, the flush casing configured to be movable in the axial direction between a first end position and a second end position, and the width of the axial leakage gap is zero when the flush casing is in an operating position located between the first end position and the second end position, so that the bushing abuts against the impeller.