The invention relates to a multi-stage centrifugal pump assembly having a motor housing and a pump housing connected thereto and having a bearing carrier which receives a bearing of a shaft, which on the motor side carries a rotor and on the pump side carries impellers arranged in pump chambers. 
With regard to the multi-stage centrifugal pump assemblies being discussed here, it is particularly the case of those with a lying shaft, thus with which the motor and the pump are arranged next to one another on operation.  Such assemblies, for some time, have been counted as belonging to the state of the art, and are manufactured and offered for example by the company Grundfos under the model range descriptions CH and CHN.  They consist of an electric drive motor and of a single-stage or multi-stage centrifugal pump which is connected thereto, wherein the motor housing of the motor is connected to the pump housing, and a bearing carrier is provided between the pump housing and the motor housing, said bearing carrier receiving a bearing of a shaft, which on the motor-side carries a rotor and on the pump-side carries impellers, which are arranged in pump chambers.  This bearing carrier either forms a part of the motor housing or a part of the pump housing or both. 
The above mentioned model ranges CH and CHN differ essentially by the fact that with the model range CH, the end-side pump housing parts are manufactured from a cast, whereas with the model range CHN, all fluid leading parts of the pump are lined with stainless steel or consist of stainless steel.  Apart from the drive motors, the two model ranges comprise a multitude of the same parts, thus typically the impellers, as well as the pump chambers, which consist of sheet metal and which encompass the diffuser of the respective stage, but also a multitude of different components.