Abstract: Rotating fluid-handling apparatus, e.g., a centrifugal separator has at least first and second elements which rotate relative to the other about a common axis. A seal assembly provides fluid-tight sealing between the elements, which define passages for fluid flow from one element to the other. The seal assembly has at least one annular seat carried by one of the elements coaxially with the axis, and an annular seal, the other of the elements defining a chamber for the seal in proximity to the seat. The chamber carries the seal within it coaxial with the axis, the seal being shiftable axially within the chamber between positions, in and out of sealing contact with the seat. Sealing contact with the seat is provided over an annular sealing surface area.