Pump assembly

A pump assembly having

• a barrel casing;
• and
• a plug-in unit arranged at least in part in the barrel casing, the plug-in unit including a shaft rotatable about an axis of rotation and at least two pressure stages,
• wherein
• each of the at least two pressure stages includes a pressure stage casing, an impeller arranged on the shaft and enclosed by the pressure stage casing, and a seal that separates a first pressure chamber of a first one of the at least two pressure chambers from a second pressure chamber of a second one of the at least two pressure chambers,
• the pressure stage casing of at least one of the at least two pressure stages includes a first casing part and a second casing part,
• the first casing part has a first region having an enlarged inner diameter and a second region, downstream of the first region along an axis of rotation, having a reduced inner diameter,
• the second casing part has at least one first portion having a reduced outer diameter and a second portion having an enlarged outer diameter,
• the first region of the first casing part encloses the first portion of the second casing part and at least in part encloses the second portion of the second casing part such that an annular chamber is formed between the first casing part and the second casing part and the annular chamber is connected to the second pressure chamber,
• the first region of the first casing part has a sleeve shape,
• the second casing part has an annular disc shape, and
• the outer diameter of the second portion of the annular disc-shaped second casing part and the inner diameter of the first region of the sleeve shaped first casing part are formed at their overlapping regions such that the first region of the first casing part bears against or is spaced apart from the second portion of the second casing part.