Process fluid lubricated pump

A process fluid lubricated pump for conveying a process fluid, comprising:

• a common housing;
• a pump unit arranged in the common housing;
• a balance drum and a drive unit arranged in the common housing, the common housing comprising an inlet and an outlet for the process fluid,
• the pump unit comprising a pump shaft extending from a drive end to a non-drive end of the pump shaft and configured to rotate about an axial direction, at least a first stage impeller fixedly mounted on the pump shaft, and a last stage impeller fixedly mounted on the pump shaft,
• the drive unit configured to exert torque on the drive end of the pump shaft to drive the rotation of the pump shaft,
• the balance drum fixedly connected to the pump shaft between the pump unit and the drive end of the pump shaft, the balance drum defining a drum front side facing the pump unit and a drum back side,
• a relief passage disposed between the balance drum and a first stationary part configured to be stationary with respect to the common housing, the relief passage extending from the drum front side to the drum back side, and the pump shaft radially supported in a non-contacting manner during operation of the pump;
• at most one hydrodynamic radial pump bearing to support the pump shaft, the at most one radial pump bearing being arranged at the non-drive end or at the drive end of the pump shaft;
• and
• at least one hydrostatic support device to radially support the pump shaft, the hydrostatic support device configured to provide the support by the Lomakin effect.