A seal assembly and cartridge for sealing a space between a rotating member and a stationary member in which a sleeve extends around the rotating member and with the inner surface of the sleeve being spaced from the outer surface of the rotating member to form a gap. Pressurized fluid is introduced to the sleeve to establish and maintain a predetermined gap between the sleeve and the rotating member, so that the pressure of the fluid can be varied to maintain the predetermined gap despite variations of the diameter of the rotating member during its rotation.