Encapsulated stator assembly and process for making

Abstract

Rotor and stator assemblies that utilize magnetic bearings for supporting the rotor shaft during operation can be suitably used in corrosive environments, such as sour gas. The rotor and stator assemblies include NACE compliant magnetic bearing arrangements for sour gas applications. One embodiment includes a stator assembly that comprises a stator sleeve formed of a magnetic material, a sleeve extender coaxial to the stator sleeve formed of a non-magnetic material fixedly attached to each end of the stator sleeve, wherein a point of attachment is heat treated, and a wall formed of the non-magnetic material fixedly attached to the sleeve extender configured to hermetically house a stator and form the encapsulated stator assembly.

1 . A process of forming an encapsulated stator assembly, the process comprising:
 welding a stator sleeve extender formed of a non-magnetic material to a stator sleeve formed of a magnetic material and subsequently heat-treating the welded stator sleeve extender and the stator sleeve at a temperature effective to relieve weld stress;   attaching stator electromagnetic components to the stator sleeve; and   welding a housing formed of the non-magnetic material to the stator sleeve extender, wherein the housing is configured to encapsulate and hermetically seal the stator electromagnetic components.   
     
     
         2 . The process of  claim 1 , wherein the magnetic material comprises a precipitation hardened martensitic stainless steel comprising 10 to 20 wt % chromium based on a total weight of the precipitation hardened martensitic stainless steel. 
     
     
         3 . The process of  claim 1 , wherein the non-magnetic material comprises a nickel based alloy comprising 40 to 70 wt % nickel based on a total weight of the nickel based alloy. 
     
     
         4 . The process of  claim 1 , wherein heat-treating the welded stator sleeve extender and the stator sleeve comprises exposing the stator sleeve extender and the stator sleeve to a double age hardening process. 
     
     
         5 . The process of  claim 1 , further comprising attaching power and instrumentation wires to the stator electromagnetic components, wherein the wires comprise a wire sleeve comprising a non-magnetic corrosion-resistant alloy surrounding an electrically conductive material. 
     
     
         6 . The process of  claim 1 , wherein welding the stator sleeve extender to the stator sleeve comprises an autogenous electron beam process, a laser weld process, a TIG weld process, a MIG weld process, an arc weld process, a torch weld process or combinations comprising at least one of the foregoing processes. 
     
     
         7 . The process of  claim 1 , wherein heat-treating the welded stator sleeve extender and the stator sleeve comprises solution annealing at an elevated temperature and subsequently cooling to below 32° C.; followed by at least one precipitation-hardening cycle.