Gas seal for pumps

In a liquid handling device, such as a pump, having a housing structure defining therein a pumping chamber, a rotatable shaft projecting through the housing structure into the pumping chamber and having a liquid handling element such as a pumping impeller positioned within the pumping chamber and connected to the shaft for rotation therewith, and a seal arrangement cooperating between the rotatable shaft and the housing structure for preventing leakage of pumping liquid from the pumping chamber into the surrounding environment, the seal arrangement including an annular face-seal unit interposed between the shaft and the housing structure, the face-seal unit including an annular rotor nonrotatably coupled to the shaft and disposed axially adjacent an annular stator which is nonrotatably coupled relative to the housing structure, the stator and rotor having axially adjacent and axially-opposed seal faces which cooperate to define inner and outer peripheral edge regions, one of said edge regions being in communication with the pumping chamber, and a pressurized barrier gas being supplied to an annular chamber which surrounds the other peripheral edge region so as to create an annular gas seal film between the opposed seal faces, the improvement comprising an annular shroud fixed relative to said housing structure and disposed closely adjacent but spaced from said shaft in surrounding relationship therefrom so as to define an axially elongated annular flow passage therebetween, said annular shroud being positioned relative to the shaft axially between said face-seal unit and said pumping chamber, said shroud defining thereon an inner cylindrical surface which is axially elongated and defines the outer boundary of said annular flow passage, said inner cylindrical surface being of a generally truncated conical configuration so as to be of increasing diameter as it extends from a first end thereof which is disposed most closely adjacent the face-seal unit to a second end thereof which is directed toward the pumping chamber, said annular flow passage at the small diameter end of said shroud being spaced outwardly from the rotatable shaft by a small radial clearance so that rotation of the shaft causes solid particles in the pumping liquid to be centrifugally displaced outwardly adjacent the truncated conical configuration of said inner surface and then flow axially outwardly therealong for return to the pumping chamber to minimize the inflow of solid particles to the face-seal unit.

In a fluid handling device having a housing structure defining a process chamber for handling a process fluid, a rotatable shaft projecting into the process chamber and having a fluid handling element positioned within the process chamber and connected to the shaft for rotation therewith, and a seal arrangement cooperating between the rotatable shaft and the housing structure for preventing leakage of process fluid from the process chamber into the surrounding environment, the seal arrangement including an annular face-seal unit interposed between the shaft and the housing structure, the face-seal unit including an annular rotor nonrotatably coupled to the shaft and disposed axially adjacent an annular stator which is nonrotatable relative to the housing structure, the stator and rotor having opposed and axially adjacent seal faces, the improvement comprising a housing member fixed relative to said housing structure and disposed in surrounding relationship to the shaft at an inboard side of said face-seal unit adjacent said process chamber, said housing member being radially spaced from said shaft so as to define an axially extending and annular flow passage therebetween, said housing member defining an inner surface which is axially elongated and defines an outer boundary of said annular flow passage, said inner surface being of a generally tapered configuration and having a minimum diameter portion defined at one end of said housing member adjacent said face-seal unit to minimize migration of debris in the process fluid located within said annular flow passage toward said seal unit during rotation of said shaft.