Flexible housing for steam turbine exhaust hood

Abstract

A flexible housing is arranged along an axial centerline of a rotor shaft of a steam turbine. The flexible housing extends between an exhaust hood endcover and a seal end packing housing on a separate supporting standard. The flexible housing includes a top cover portion and a bottom cover portion with a flanged horizontal joint that permits removal and replacement without need to remove the exhaust hood cover and the rotor shaft. The flexible housing encloses the rotor shaft with a first cylindrical element and a second cylindrical element of a different radius joined with an thin member that flexes to absorb expansion and contraction of the turbine exhaust hood.

1 . A flexible housing arranged along an axial centerline of a rotor shaft of a steam turbine, the flexible housing comprising:
 a first cylindrical element with a first radius centered on an axial centerline of a rotor shaft of a steam turbine;   a second cylindrical element with a second radius centered on the axial centerline, the second radius being different from the first radius, wherein the second cylindrical element is arranged adjacent to the first cylindrical element along the axial centerline;   a thin annular member comprising an inner radius corresponding to the first radius and an outer radius corresponding to the second radius, wherein the inner radius is fastened to an end of the first cylindrical element and the outer radius is fastened to an adjacent end of the second cylindrical element;   a first flange fastened to a non-adacent end of the first cylindrical element and adapted to mount to an exhaust hood of the steam turbine; and   a second flange fastened to a non-adjacent end of the second cylindrical element and adapted to mount to a seal end packing box external to the exhaust hood of the steam turbine.   
     
     
         2 . The flexible housing of  claim 1 , wherein the flexible housing is split along a horizontal hemisphere, each hemisphere including opposed flanged joints for assembly around a rotor shaft. 
     
     
         3 . The flexible housing of  claim 2 , each opposed flanged joint including vertical expansion splits on an outer edge. 
     
     
         4 . The flexible housing of  claim 3 , wherein the vertical expansion slits on the opposed flanged joints are disposed proximate the thin annular member. 
     
     
         5 . The flexible housing of  claim 3 , wherein the vertical expansion slits on the opposed flanged joints of the hemispheres flex in response to axial expansion and axial contraction of the exhaust hood when the flexible housing is installed between the exhaust hood and a separately mounted seal end packing box for a steam turbine. 
     
     
         6 . The flexible housing of  claim 2 , wherein the thin annular member, split along the horizontal hemisphere, and flexes in response to the axial expansion and axial contraction of the exhaust hood when the flexible housing is installed between the exhaust hood and a separately mounted seal end packing box for a steam turbine. 
     
     
         7 . A steam turbine comprising:
 an inner casing forming a working steam path through steam turbine stages;   an exhaust hood surrounding the inner casing forming an path for exhaust steam from the inner casing;   a rotor shaft, having an axis driven from the inner casing and extending through at least one axial end of the exhaust hood;   a standard mounting a bearing support and a seal end packing box for the rotor shaft, wherein the standard is mounted separate from the exhaust hood for at least one axial end of the steam turbine;   a flexible housing mounted between an axial end of the exhaust hood and the seal end packing box, wherein the flexible housing encloses the rotor shaft between the axial end of the exhaust hood and the seal end packing box and fluidly connects exhaust steam from at least one axial end of the exhaust hood to the seal end packing box.   
     
     
         8 . The steam turbine of  claim 7 , the flexible housing comprising:
 a first cylindrical element with a first radius centered on the axis;   a second cylindrical element with a second radius centered on the axis, the second radius being different from the first radius, wherein the second cylindrical element is arranged adjacent to the first cylindrical element along the axis;   a thin annular member comprising an inner radius corresponding to the first radius and an outer radius corresponding to the second radius, wherein the inner radius is fastened to an end of the first cylindrical element and the outer radius is fastened to an adjacent end of the second cylindrical element;   a first flange fastened to a non-adacent end of the first cylindrical element and adapted to mount to an exhaust hood of the steam turbine; and   a second flange fastened to a non-adjacent end of the second cylindrical element and adapted to mount to a seal end packing box external to the exhaust hood of the steam turbine.   
     
     
         9 . The steam turbine of  claim 7 , wherein the flexible housing is split along a horizontal hemisphere, each hemisphere including opposed flanged joints. 
     
     
         10 . The steam turbine of  claim 9 , each opposed flanged joints including vertical expansion splits on an outer edge. 
     
     
         11 . The steam turbine of  claim 10 , wherein the vertical expansion slits on the opposed flanged joints are disposed proximate the thin annular member. 
     
     
         12 . The steam turbine of  claim 11 , wherein the vertical expansion slits on the opposed flanged joints of the hemispheres flex in response to axial expansion and axial contraction of the exhaust hood when the flexible housing is installed between the exhaust hood and a separately mounted seal end packing box for a steam turbine. 
     
     
         13 . The steam turbine of  claim 7 , wherein the thin annular member flexes in response to the axial expansion and axial contraction of the exhaust hood when the flexible housing is installed between the exhaust hood and a separately mounted seal end packing box for a steam turbine. 
     
     
         14 . The steam turbine of  claim 13 , wherein a thickness of the thin annular member is selected to provide sufficient deflection to accommodate the expected axial motion of the exhaust endcover under exhaust hood temperature and pressure variations without itself incurring permanent deformation. 
     
     
         15 . A flexible housing arrangement sealing a rotor shaft for a steam turbine between an exhaust hood and a seal end packing box mounted on a separate standard, the flexible housing arrangement comprising:
 an exhaust hood with an endcover for a steam turbine;   a seal end packing box housed on a standard separate from the exhaust hood;   a rotor shaft extending between the endcover of the exhaust hood and the seal end packing box;   opposing cover portions of a flexible housing, each portion including a first semi-cylindrical element with a first radius on the centerline of the flexible housing; a second semi-cylindrical element with a second radius centered on the centerline of flexible housing, the second radius being different from the first radius, wherein the second cylindrical element is arranged adjacent to the first cylindrical element along a centerline;   a thin semi-annular plate including an inner radius corresponding to the first radius and an outer radius corresponding to the second radius, wherein the inner radius is fastened to an end of the first cylindrical element and the outer radius is fastened to an adjacent end of the second cylindrical element;   a horizontal flange attached to each of the opposing cover portions along an equator of the first semi-cylindrical element, the second semi-cylindrical element and the semi-annular element, wherein the horizontal flanges are adapted for bolting the opposing cover portions around the rotor shaft; and   a semi-cylindrical end flange attached at each opposing end for each cover portion, wherein one semi-cylindrical end flange is attached to the first semi-cylindrical element is mounted to the exhaust hood endcover and wherein a second semi-cylindrical end flange that is attached to the second semi-cylindrical element is mounted to the seal end packing box on a standard.   
     
     
         16 . The flexible housing arrangement of  claim 15 , wherein a conical recess of the exhaust hood provides access space for assembly and removal of the flexible housing around the rotor shaft. 
     
     
         17 . The flexible housing arrangement of  claim 15 , wherein the thin semi-annular member of the flexible housing flexes in response to axial expansion and axial contraction of the exhaust hood. 
     
     
         18 . The flexible housing arrangement of  claim 17 , wherein a thickness of the thin annular member is selected to provide sufficient deflection to accommodate expected axial motion of the exhaust endcover under exhaust hood temperature and pressure variations without itself incurring permanent deformation. 
     
     
         19 . The flexible housing arrangement of  claim 15 , wherein the horizontal flanges attached to the opposing cover portions include expansion slits in proximity to an axial location of the semi-annular elements. 
     
     
         20 . The flexible housing arrangement of  claim 15 , wherein the opposing cover portions of the flexible housing are removable by unbolting the horizontal flange between the cover portions and unbolting the end flange for the respective cover portion.