Stern tube seal system

Abstract

A seal system includes a face seal rotor ring including a wide sealing face preferably made of tungsten carbide. The stator ring includes a narrower sealing face confronting the rotor ring wide sealing face. The stator ring sealing face is preferably made of polyamide-imide and tapers to narrower widths rearwardly.

What is claimed is: 
     
         1 . A shaft seal system comprising:
 a face seal stator ring disposable about a shaft;   a face seal rotor ring disposable about the shaft for rotation therewith;   one of the stator ring and rotor ring including:
 a wide sealing face made of a metal, and 
 the other of the stator ring and rotor ring including a narrower sacrificial plastic sealing face confronting the wider sealing face. 
   
     
     
         2 . The system of  claim 1  in which the stator ring includes the narrower plastic confronting sealing face. 
     
     
         3 . The system of  claim 1  in which the plastic confronting sealing face tapers to narrower widths rearwardly to reduce the confronting area of the plastic sealing face as the sealing face wears. 
     
     
         4 . The system of  claim 1  in which the stator ring further includes a rearward flange for mounting the stator ring to a stator holder. 
     
     
         5 . The system of  claim 1  in which the wider sealing face includes a second material on the metal ring. 
     
     
         6 . The system of  claim 5  in which the wide sealing face includes a tungsten carbide coating on the metal ring. 
     
     
         7 . The system of  claim 1  in which the plastic is polyamide-imide. 
     
     
         8 . The system of  claim 1  further including a clamp ring fixed to the shaft and to the rotor. 
     
     
         9 . The system of  claim 8  further including a back-up seal. 
     
     
         10 . The system of  claim 9  in which the back-up seal is fluid activated. 
     
     
         11 . The system of  claim 10  in which the fluid activated back-up seal includes a lip seal spaced from the rotor and a foam body including a gel material configured to expand in the presence of fluid and disposed to urge the lip seal into engagement with the rotor to seal the rotor in the presence of fluid. 
     
     
         12 . The system of  claim 1  further including a spring assembly about the shaft biasing the confronting faces into engagement with each other. 
     
     
         13 . The system of  claim 12  in which the spring assembly includes a plurality of spaced metal members on a seal member. 
     
     
         14 . The system of  claim 13  in which the seal member conforms to the shape of the spaced metal members. 
     
     
         15 . The system of  claim 14  in which the spaced metal members and the seal member are bent inwardly at each edge and then bent outwardly between the edges. 
     
     
         16 . The system of  claim 15  in which said bends are radiused. 
     
     
         17 . The system of  claim 1  further including at least one inflatable back-up seal about the shaft. 
     
     
         18 . A shaft seal system comprising:
 a face seal stator ring disposable about a shaft;   a face seal rotor ring disposable about the shaft and including a wide scaling face made of tungsten carbide; and   the stator ring including a narrower sacrificial sealing face confronting the rotor ring wider sealing face, the stator ring sealing face made of polyamide-imide and tapering to narrower widths rearwardly.   
     
     
         19 . A method of sealing a shaft, the method comprising:
 configuring one of a face seal stator ring and rotor ring to include a first sealing face made of metal;   configuring the other of the face seal stator ring and rotor ring to include a sacrificial sealing face made of a plastic material confronting the first sealing face;   the sacrificial sealing face narrower than the first sealing face; and   the sacrificial sealing face tapering to narrower widths rearwardly.   
     
     
         20 . The method of  claim 19  in which the first sealing face includes a tungsten carbide coating on a metal ring. 
     
     
         21 . The method of  claim 19  in which the plastic material is polyamide-imide. 
     
     
         22 . The method of  claim 19  further including providing a fluid activated back-up seal. 
     
     
         23 . The method of  claim 19  further including disposing a spring assembly about the shaft biasing the confronting faces into engagement with each other. 
     
     
         24 . The method of  claim 23  in which the spring assembly includes a plurality of spaced metal members on a seal member. 
     
     
         25 . The method of  claim 19  further including disposing at least one inflatable back-up seal about the shaft. 
     
     
         26 . A stem tube seal system comprising:
 a split housing disposable about a propeller shaft;   a split face seal stator ring assembly in the housing disposed about the propeller shaft;   a split face seal rotor ring assembly in the housing coupled and sealed to the propeller shaft;   one of the stator ring assembly and the rotor ring assembly including:
 a wide sealing face made of a metal, and 
 the other of the stator ring assembly and the rotor ring assembly including a narrower sacrificial plastic sealing face confronting the wider sealing face; 
   the sacrificial plastic sealing face tapering to narrower widths readwardly to reduce the confronting area of the plastic sealing face as the sealing on the wider sealing face as the sacrificial plastic sealing face wears; and   a spring assembly in the housing biasing the rotor ring assembly into engagement with the stator ring assembly, the spring assembly including:
 spaced metal members disposed about the shaft extending between the housing and the stator ring assembly, and 
 a rubber seal member about the shaft conforming to the spaced bent metal members sealing the stator ring assembly with respect to the housing. 
   
     
     
         27 . The system of  claim 26  in which the sacrificial plastic sealing face tapers at an angle sufficient to maintain a constant or nearly constant strength force applied by the spring assembly as the sacrificial plastic sealing face wears. 
     
     
         28 . The system of  claim 27  in which said angle is between 60 and 70 degrees. 
     
     
         29 . The system of  claim 26  in which the wide sealing face includes a second material on the metal ring. 
     
     
         30 . The system of  claim 29  in which the wide sealing face includes a tungsten carbide coating on the metal ring. 
     
     
         31 . The system of  claim 26  in which the plastic is polyamide-imide. 
     
     
         32 . The system of  claim 26  in which the rotor assembly include a clamp ring fixed to the shaft and to the rotor ring. 
     
     
         33 . The system of  claim 26  further including a fluid activated back-up seal. 
     
     
         34 . The system of  claim 26  in which the stator ring assembly includes a stator holding ring fixed to the stator ring and the spring assembly.