A process fluid lubricated pump includes a pump having a pump shaft extending from a drive end to a non-drive end, first and last stage impellers, a drive unit exerting torque on the drive end to rotate the pump shaft, a balance drum connected to the pump shaft between the pump and the drive end, the balance drum defining a drum front side facing the pump and a drum back side, a relief passage between the balance drum and a first stationary part configured to be stationary with respect to a housing, the relief passage extending from the drum front side to the drum back side, the pump shaft radially supported in a non-contacting manner during operation of the pump, and a hydrodynamic radial pump bearing supporting the pump shaft, the radial pump bearing arranged at the non-drive end or at the drive end of the pump shaft.