 There are also machines that exhibit a combination of both properties and are specifically referred to as "mixed-flow" machines.Centrifugal pump impellers have specific speed values ranging from 500 to 10,000 (English units), with radial flow pumps at 500-4000, mixed flow at 2000-8000 and axial flow pumps at 7000-20,000.Values of specific speed less than 500 are associated with positive displacement pumps.