Primary shaft seal combined with secondary seal - uses piston controlled by seepage pressure from primary seal to apply secondary seal

摘要

The shaft seal assembly comprises primary and secondary face seals. The space between the seals is connected by a duct to the one end of a hydraulic piston coaxial with the shaft. The other end of the piston confronts a collar mounted on the shaft. If the pressure of seepage from the primary seal rises the piston is moved into engagement with the collar to establish the secondary seal. The collar may be axially slidable on the shaft, and when the piston acts on the collar the latter is pushed back against the pressure of a spring which then determines the pressure of the seal.