Gas seal system for the shaft of an electric compressor motor

Abstract

An electric motor ( 30 ) is accommodated in a first portion ( 42 ) of a housing ( 40 ) and is arranged to drive a compressor ( 32 ) accommodated in a second portion ( 44 ) of the housing separated from the first housing portion ( 42 ) by a wall ( 46 ). An umbilical ( 48 ) introduces dry motor protection gas into the first housing portion ( 42 ) and a passage ( 54 ) between the first and second housing portions ( 42,44 ) allows a leakage of the motor protection gas from the first housing portion ( 42 ) into the second housing portion ( 44 ) at a higher pressure than gas supplied to the compressor ( 32 ) via an inlet pipe ( 58 ) thereby preventing moisture laden gas from the compressor ( 32 ) entering the first housing portion accommodating the electric motor ( 30 ).

1 . A gas seal system assembly, comprising: 
 a housing;    an electric motor accommodated within a first portion of the housing;    rotating machinery accommodated within a second portion of the housing and driven by said electric motor;    separation means in the housing between said first and second portions thereof for separating fluid acted upon by said rotating machinery from said electric motor;    gas introduction means for introducing at least substantially dry motor protection gas into said first housing portion;    wherein said gas introduction means further comprises a restricted gas flow means for permitting a leakage of the motor protection gas from said first housing portion into said second housing portion; and    a circulating apparatus for diverting a portion of the fluid acted upon by said rotating machinery to said first housing portion, said circulating apparatus including drying means for reducing the moisture content of the acted upon gas diverted back to said first housing portion, said drying means having at least one outlet.    
   
   
       2 . The assembly as claimed in  claim 1 , wherein said gas introduction means includes external means for supplying the at least substantially dry gas.  
   
   
       3 . The assembly as claimed in  claim 2 , wherein said means for supplying the at least substantially dry gas comprises a gas drying and supply unit on a remote host facility linked to said first housing portion by an umbilical.  
   
   
       4 . The assembly as claimed in  claim 1 , wherein said drying means separates the diverted portion of the acted upon gas into an at least substantially moisture-free first outlet flow and said circulating apparatus includes first routing means for routing the first outlet flow from a first one of said at least one outlet of said drying means to said first housing portion.  
   
   
       5 . The assembly as claimed in  claim 4 , wherein said drying means incorporates moisture extracted from the acted upon gas into a second outlet flow from said drying means.  
   
   
       6 . The assembly as claimed in  claim 5 , wherein the second outlet flow from said drying means is transported away from the assembly by means of the gas being acted upon by said rotating machinery.  
   
   
       7 . The assembly as claimed in  claim 5 , including second routing means for routing the second outlet flow containing the extracted moisture from a second outlet of said drying means and for incorporating it into the flow of gas acted upon by said rotating machinery.  
   
   
       8 . The assembly as claimed in  claim 7 , wherein said second routing means incorporates the second outlet flow containing the extracted moisture into the acted upon gas at least substantially prior to the gas being acted upon by said rotating machinery.  
   
   
       9 . The assembly as claimed in  claim 7 , wherein said second routing means incorporates the second outlet flow containing the extracted moisture into the acted upon gas at least substantially after the gas has been acted upon by said rotating machinery.  
   
   
       10 . The assembly as claimed in  claim 9 , wherein said second routing means includes a pressure equalizing device for incorporating the second outlet flow containing the extracted moisture into the acted upon gas downstream of said rotating machinery.  
   
   
       11 . The assembly as claimed in  claim 1 , wherein at least one outlet flow passes through at least one non-return valve configured to prevent such flow or flows returning directly to said at least one outlet of said drying means.  
   
   
       12 . The assembly as claimed in  claim 1  wherein said rotating machinery is selected from the group consisting of compressors and centrifugal pumps.  
   
   
       13 . The assembly as claimed in  claim 1 , wherein said second housing portion includes a compressor inlet for receiving gas at a first pressure and a compressor outlet for delivering gas at a second pressure higher than the first pressure and said restricted gas flow means enables leakage of the motor protection gas into said second housing portion.  
   
   
       14 . The assembly as claimed in  claim 13 , wherein said gas flow means is adjacent said compressor inlet.  
   
   
       15 . The assembly as claimed in  claim 1 , including means for automatically maintaining the motor protection gas at a pressure above that of fluid in a part of said second housing portion adjacent said restricted gas flow means.  
   
   
       16 . A gas seal system method, comprising: 
 operating an electric motor accommodated in a first portion of a housing and arranged to drive a rotating machine accommodated in a second portion of the housing in which fluid in the second housing portion which is acted upon by the rotating machine is separated from the first housing portion by separation means, the method including providing gas introduction means for introducing at least substantially dry motor protection gas into the first housing portion, and providing restricted gas flow means between the first and second housing portions, wherein the method further comprises the steps of:    establishing a leakage of the motor protection gas from the first housing portion to the second housing portion via the gas flow means;    providing circulating apparatus and diverting a portion of the acted upon gas to the first housing portion via the circulating apparatus; and    incorporating drying means in the circulating apparatus and reducing the moisture content of the acted upon gas diverted back to the first housing portion by means of the drying means.