Barrier sealing system

Abstract

A barrier seal system comprises a rotatable shaft disposed within an outer housing. The rotatable shaft axially extends from a high-pressure region to a low-pressure region within the outer housing. At least a portion of the rotatable shaft, typically the portion disposed adjacent to the low-pressure region, comprises an oleophobic surface. The system further comprises a barrier seal that radially extends from the outer housing to the rotatable shaft and defines a gap between the barrier seal and the rotatable shaft. A barrier gas injector is provided for injecting a barrier gas into the gap to flow from the high-pressure region to the low-pressure region.

1 . A barrier seal system comprising:
 a rotatable shaft disposed within an outer housing and axially extending from a high-pressure region to a low-pressure region, wherein at least a portion of said rotatable shaft disposed adjacent said low-pressure region comprises an oleophobic surface;   a barrier seal that radially extends from said outer housing to said rotatable shaft and defines a gap between the barrier seal and the rotatable shaft;   a barrier gas injector for injecting a barrier gas into said gap to flow from said high-pressure region to said low-pressure region.   
   
   
       2 . A barrier seal system in accordance with  claim 1 , wherein said barrier seal system is used within rotating machinery. 
   
   
       3 . A barrier seal system in accordance with  claim 1 , further comprising a lubricating element within the low-pressure region. 
   
   
       4 . A barrier seal system in accordance with  claim 3 , wherein said barrier gas injector injects a barrier gas through said gap to prevent migration of said lubricating element from said low-pressure region to said high-pressure region. 
   
   
       5 . A barrier seal system in accordance with  claim 4 , wherein said oleophobic surface prevents film formation of said lubricating element adjacent to said gap. 
   
   
       6 . A barrier seal system in accordance with  claim 1 , wherein said oleophobic surface is an oleophobic coating. 
   
   
       7 . A barrier seal system in accordance with  claim 1 , wherein said oleophobic surface is an oleophobic texturing. 
   
   
       8 . A barrier seal system in accordance with  claim 3 , wherein said lubricating element is oil. 
   
   
       9 . A barrier seal system in accordance with  claim 1 , wherein said barrier seal is selected from the group consisting of brush seals, labyrinth seals and carbon face seals. 
   
   
       10 . A barrier seal system in accordance with  claim 1 , wherein said barrier seal is selected from the group consisting of contacting seals and non-contacting seals. 
   
   
       11 . A barrier seal system in accordance with  claim 1 , wherein said barrier gas is injected at a mass flow rate of less than about 16 feet per second. 
   
   
       12 . A barrier seal system in accordance with  claim 3 , wherein said oleophobic surface increases the wetting angle of the lubricating element and correspondingly decreases the required mass flow rate of said injected barrier gas to prevent migration of said lubricating element through said gap. 
   
   
       13 . A barrier seal system in accordance with  claim 1 , wherein said shaft further comprises a shaft sleeve. 
   
   
       14 . A barrier seal system in accordance with  claim 13 , wherein at least a portion of said shaft sleeve disposed within said high-pressure region comprises an oleophobic surface; 
   
   
       15 . A barrier seal system in accordance with  claim 1 , wherein said barrier gas is an inert gas. 
   
   
       16 . A barrier seal system in accordance with  claim 15 , wherein said inert gas is nitrogen. 
   
   
       17 . A barrier seal system in accordance with  claim 3 , wherein the static contact angle of the oleophobic surface is greater than about 30 degrees. 
   
   
       18 . A dry gas seal assembly comprising:
 a dry gas seal; and   a barrier seal assembly spaced apart from said dry gas seal comprising:   a rotatable shaft disposed within an outer housing and axially extending from a high-pressure region to a low-pressure region, wherein at least a portion of said rotatable shaft disposed adjacent said low-pressure region comprises an oleophobic surface;   a barrier seal that radially extends from said outer housing to said rotatable shaft and defines a gap between the barrier seal and the rotatable shaft;   a barrier gas injector for injecting a barrier gas into said gap to flow from said high-pressure region to said low-pressure region.