Abstract: A multiple stage mechanical end face seal assembly which has been developed to improve seal reliability and performance during both steady-state and transient operation. The seal assembly features a rotating seal ring mounting system which utilizes a rigid support ring loaded thru narrow annular projections in combination with centering non-sealing O-rings which effectively isolate the rotating seal ring from temperature and pressure transients while securely positioning the ring to adjacent parts, and a stationary seal ring mounting configuration which allows the stationary seal ring freedom of motion to follow shaft axial movement up to 3/4 of an inch and shaft tilt about the pump axis without any change in the hydraulic or pressure loading on the stationary seal ring or its carrier. An internal filter arrangement prevents plugging of the pressure staging coils in a multi-stage seal assembly.