At research institutes, liquid helium is supplied in mobile dewars, filled by pressurization of the storage dewar. To reduce the evaporation losses significantly, a pump can be installed. In this article, a prototype of a submersible centrifugal pump is comprehensively investigated by varying process parameters such as shaft speed and sealing gap. The measurements were performed with a single flow transfer line during a standard filling process of dewars, used for the laboratory supply at the TU Dresden. The pump characteristics show wide operating ranges with efficiencies above 50% and peak efficiencies over 80% at high-speed operation. A significant reduction in filling losses and time compared to the traditional process could be demonstrated.