Today cryogenic circulating systems are used in many branches of technology as cryostats for superconducting devices and in cryogenic vacuum pumps where a high vacuum or a high capacity is required. One of the most important elements in these systems is the flow driver - the device which causes the cryogenic liquid to circulate. Systems which include a mechanical or jet pump are widely used, as are those in which the liquid is circulated by a compressor in a single-loop system. The operational principle of a new device for circulating cryogenic liquid - an expander pump - is as follows. Previously compressed gas, with a temperature somewhat higher than the saturation temperature, expands in a cylinder and does work by pumping the liquid. At the end of the expansion process, part of the working gas condenses and can completely or partially compensate the loss of liquid in the utilization loop. The use of an expander pump has many advantages over other flow drivers. These advantages are discussed.