Pump with integral caisson discharge

Abstract

A caisson for submersible pumps and method of operating a pump that is fluidly cooperative with the caisson. The pump discharge and the caisson are fluidly coupled to one another such that upon discharge of a fluid being pumped, the caisson acts as the fluid conduit, thereby removing the need for redundant riser pipes. In one form, the pump is a seawater lift pump for use with floating production storage and offloading (FPSO), offshore platforms or related structures.

What is claimed is: 
     
         1 . A seawater pumping assembly comprising:
 an offshore platform; and   a lift pump assembly cooperative with said offshore platform such that placement of said offshore platform within an ambient body of seawater results in said lift pump assembly being exposed directly thereto, said lift pump assembly comprising:
 a pump comprising a motor section and an impeller section; 
 a caisson coupled to said pump and comprising an interior portion and an exterior portion such that when said caisson is disposed within said ambient body of seawater that is in contact with said exterior portion, said caisson acts as a non-redundant fluid barrier between said ambient body of seawater and a pressurized seawater flowpath that is both (a) formed downstream of said impeller section during operation of said pump and (b) defined by said interior portion; 
 a plurality of flanges formed on said caisson, said plurality of flanges comprising:
 a first flange disposed within said interior portion to provide at least one of radial support and vertical support to said pump; and 
 a second flange situated at the top of said caisson to define both (a) a fixed vertical support of said pump and (b) sealed isolation of said pressurized seawater from said ambient seawater along said seawater flowpath; and 
 
 a gasket disposed within at least one of said ambient seawater and said pressurized seawater and placed between (a) said pump and (b) at least one of said first and second flanges to define a galvanic decoupling structure therebetween. 
   
     
     
         2 . The seawater pumping assembly of  claim 1 , wherein said lift pump assembly comprises a middle-intake design where said motor section is disposed axially below said impeller section. 
     
     
         3 . The seawater pumping assembly of  claim 1 , wherein said lift pump assembly comprises a bottom-intake design where said motor section is disposed axially above said impeller section. 
     
     
         4 . The seawater pumping assembly of  claim 1 , further comprising a cover situated at the top of said caisson such that said sealed isolation of said pressurized seawater from said ambient seawater along said seawater flowpath is formed by a pressure-tight connection in a region of said interior portion that is adjacent at said second flange. 
     
     
         5 . The seawater pumping assembly of  claim 1 , wherein said offshore platform is selected from the group consisting of a fixed offshore platform and a floating production storage and offloading facility. 
     
     
         6 . The seawater pumping assembly of  claim 5 , wherein said at least one of said pump and said caisson is situated outside a hull of said floating production and storage offloading facility. 
     
     
         7 . The seawater pumping assembly of  claim 5 , wherein said at least one of said pump and said caisson is situated outside a leg support structure on said fixed offshore platform. 
     
     
         8 . The seawater pumping assembly of  claim 1 , wherein at least said first flange comprises a metal that is dissimilar to that of the portion of said pump. 
     
     
         9 . The seawater pumping assembly of  claim 1 , wherein said first flange provides both said radial support and said vertical support to said pump that is coupled to said gasket. 
     
     
         10 . The seawater pumping assembly of  claim 1 , wherein said gasket comprises a plurality of gaskets such that each is placed between (a) said pump and (b) a respective one of said first and second flanges to define a galvanic decoupling structure therebetween. 
     
     
         11 . An oil and gas extraction device comprising:
 an offshore platform selected from the group consisting of (a) a floating production storage and offloading facility and (b) an offshore rig; and   a lift pump assembly cooperative with said offshore platform such that placement of said offshore platform within an ambient body of seawater results in said lift pump assembly being exposed directly thereto, said lift pump assembly comprising:
 a pump comprising a motor section and an impeller section; 
 a caisson coupled to said pump, said caisson comprising an interior portion and an exterior portion such that when said caisson is disposed within an ambient body of seawater that is in contact with said exterior portion, said caisson acts as a non-redundant fluid barrier between said ambient body of seawater and a seawater flowpath that is both (a) formed downstream of said impeller section and (b) defined by said interior portion; 
 a plurality of flanges formed on said caisson, said plurality of flanges comprising:
 a first flange disposed within said interior portion to provide at least one of radial support and vertical support to said pump; and 
 a second flange situated at the top of said caisson to define both (a) a fixed vertical support of said pump and (b) sealed isolation of said pressurized seawater from said ambient seawater along said seawater flowpath; and 
 
   a gasket disposed within at least one of said ambient seawater and said pressurized seawater and placed between (a) said pump and (b) at least one of said first and second flanges to define a galvanic decoupling structure therebetween.   
     
     
         12 . The assembly of  claim 11 , wherein said motor section is disposed axially below said impeller section. 
     
     
         13 . The assembly of  claim 11 , wherein said lift pump assembly comprises a bottom-intake design where said motor section is disposed axially above said impeller section. 
     
     
         14 . The assembly of  claim 11 , further comprising a cover situated at the top of said caisson such that said sealed isolation of said pressurized seawater from said ambient seawater along said seawater flowpath is formed by a pressure-tight connection in a region of said interior portion that is adjacent at said second flange. 
     
     
         15 . The assembly of  claim 11 , wherein said first flange comprises a metal that is dissimilar to that of the portion of said pump that is coupled to said gasket. 
     
     
         16 . The assembly of  claim 11 , wherein said first flange provides both said radial support and said vertical support to said pump. 
     
     
         17 . The assembly of  claim 11 , wherein said gasket comprises a plurality of gaskets such that each is placed between (a) said pump and (b) a respective one of said first and second flanges to define a galvanic decoupling structure therebetween.