US2777665A

US2777665A - Turbine shell support structure

Info

Publication number: US2777665A
Application number: US449056A
Authority: US
Inventors: Martinson Arthur
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1954-08-11
Filing date: 1954-08-11
Publication date: 1957-01-15
Anticipated expiration: 1974-01-15

Description

Jan. 15, 1957 MARTINSON 2,777,665

TURBINE SHELL SUPPORT STRUCTURE Filed Aug. 11, 1954 i q R .9? *1 -J Inventor: 6 'AFthLn Martinsofi L b5 I His Attofineg United States Patent Tunisian SHELL sUrroRr STRUCTURE Arthur Martinson, cotia, N. Y., assigncr to General Eiectric Company, a corporation of New York Application August 11, 1954, Serial No. 449,056

7 Claims. (Cl. 25339) This invention relates to elastic fluid turbines of the type in which the pedestals carrying the shaft bearings and partially supporting the turbine casing are separate from the turbine casing. The novelty resides particularly in an improved method of supporting'theturbine casing on the pedestal which will allow the turbine casing to expand and contract relative to the pedestal without changing the relative position between the casing and the shaft extending therethrough and into the bearing support mounted in the pedestal.

It is theoretically desirable to support the arms of the turbine casing on the turbine pedestals exactly on the centerline of the turbine shaft. This type of construction would make immaterial the relative expansion and contractions of the turbine casing with respect to the turbine pedestal. However, practical limitations require that the shell arms be supported a substantial distance below the centerline of the turbine.

in turbines of this type the turbine casing is subjected to the heat of the; power fluid, and therefore expands relative to the pedestal. This differential expansion between the casing and pedestal directly affects the-relative position of the turbine shaft with respect to the pedestal. For example, the turbine casing when subjected to the heat of the motive fluid will expand upwardly carrying the .packings surrounding the shaftup into the shaft, resulting in a general tendency of the packings to wear on the bottom of the rings and increase the clearance for leakage.

The high speed of rotation of turbine shafts and bucket wheels and the close clearances between moving and stationary parts of this type of prime mover make it necessary that accurate concentric adjustment of such parts should be maintained at all times when the turbine is operating. 1

Accordingly, it isan object of thepresent invention to provide an improved supporting means for the turbine casing so disposed that when the turbine casing changes its dimensions due to thermal expansion or contraction the effect of this change of dimension is utilized to maintain the relative adjustment of the stationary and rotating parts, so that theseparts at all times maintain their relative positions at different temperatures.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a sideelevation partially cut away illustrating a turbine casing'supported at its ends on separate pedestals, Fig. 2 is a partial end View broken away to show the support means for the turbine casing n the pedestal, Fig. 3 is an enlarged picture of one end of the turbine casing and pedestal support means with the pedestal and support partially cut away to illustrate the side view of the casing supported on the pedestal, Fig. 4 is a perspective view of the novelsupport means for the turbine casing-on the pedestal, Fig. 5 is -a plan viewof the upper transverse guide for centering the casing in the pedestal, 'and Figy6 is'a Patented "Jan; 1'5, 1 957 sectional side View of the transverse guide taken at 6--6 in Fig. l.

Generally stated, this invention 'is practiced by providing a support assembly between a turbine casing and pedestal which will allow the turbine to expand and contract relative to the pedestal while maintaining the casing and pedestal concentric with respect to the turbine shaft extending through the casing and the pedestal. This novel support assembly permits manufacturing inaccuracies of the casing arms to be compensated for by simple modifications of the assembly members.

Referring first to Fig. 1, there is illustrated a turbine casing A which contains a turbine'rotor having a shaft 1. The turbine casing is supported at its ends on the pedestals 2, 2a. Shaft 1 extends through the ends of the turbine casing A and is supported in bearings 3 (Fig. 2) disposed in the pedestals 2. The casing A contains conventional packing means 40 surrounding the turbine shaft 1 to prevent the leakage of steam. The lefthand pedestal 2 is fixed to the foundation 4, while the righthand pedestal 2a is free to slide axially on the sole plate 4:: which is in turn secured to the foundation 4.

The turbine casing is made in two halves 5, 6. These halves each have a pair of arms 7, 8, located on opposite sides of the vertical centerline of the turbine shaft 1, which arms extend out from each end of the casing and through which the casing A is supported on the pedestal. The corresponding arms 7, 8 of the respective halves of the casing 5,6 are vertically disposedadjacent one another when the casing is bolted together along its sides by bolts 12.

The arms 7, 8 are supported on thepedestal through the novel support means B which embodies my'invention.

Experience shows that-casing lugs S of a 6 /2" thickness will, when heated upto 1000 E, cause the shell to rise upward about 30 to 40 mils, carrying all the pack ings up into the shaft and resulting in a general tendency of packings to wearonthe bottom of the rings and thereby increase' the clearance for leakage. As turbine shells increase in weight withlarger capacity units, ithis neces-' sary to either;increase the thickness of shell arm to prevent excessive statie deflection, and accept the greater packing wear due to the rise in the shell'packing-bores or there is the alternative of some kind of improve design of support.

To compensate for the uneven expansion and contraction of the turbine casing, relative to the pedestal, the applicantsnovel support means for the casing on the pedestal was designed.

sets of arms 7, gextending outwardlyfrom the ends of the turbine casing are alike, only one of them will be described here. i

Referring now to Figs. 2 and 3 there is illustrated the side and end'views of the novel support means .Bfor the turbine casing on the turbine pedestal. The arms 7, 8 extending from the upper and lowerhalves respectively of the. turbine casing are supported on the pedestal throughrthe support assembly B. The arms 7, 8 are held together by the casing flange bolts 12. The bolt 9 holds the arm 8 down on pedestal 2. The bolt 9 extends freely through holes 10, '11, in the upper arm 7, andlower arm 8 respectively and is threaded into recess i3 in, the, pedestal 2. The holes 19, 11 are substantially larger than bolt 9 to allow for relative movement between the surrounding arms 7 8 and pedestal 2.

The horizontal plane Ixx between the arms, 7, 8 extends through the centerline of the shaft.

The arm 7 extending from the upper half of the cas; ing rests freely on the. arm 8 extendingfrom the lower half of'the casing. This arrangement permits 'th'eupvj Since the support means for each of the four identical per half of the casing and its-corresponding arm to expand freelywith respect to the lower arm. This .is

' permissible since any expansion that takes place in the pedestal and is therefore free to expand vertically without stretching the bolt 9.

On the other hand, expansion of the lower part of the casing relative to the pedestal must be taken up without allowing the casing to expand upwardly at which time it would carry the packings surrounding the shaft up into the shaft, resulting in a general tendency of the packages to wear on the bottom of the rings and increase the clearance for leakage.

.This tendency for the lower half of the casing to expand upwardly is taken up by allowing the casing to expand in a radial direction. This radial movement is accomplished by inserting the support assembly B between the lower arm 8 and the pedestal 2.

'The support assembly B (see Fig. 4) is comprised of the two angle plates 16, 17 and the key plate 18. The angle plate 16 defines a circular boss 19 which fits into a circular recess 20 (Fig. 2) in the bottom surface of the arm 8. After locating the angle plate 16 in the recess, the angle plate 16 is fastened to the arm 8 by cap screws 21 (Fig. 3). The lower angle plate 17 contains a circular boss 22 which is received in a circular recess 23 located in the pedestal'2 (Fig. 2). Angle plate 17 is secured to the pedestal 2 by cap screws 24. The oppositely disposed sloped surfaces 25, 26 of the angle plates 16, 17 are at the same angle to the centerline of the bolt 9 so as to be parallel to each other when they are bolted in place in the arm 8 and pedestal 2 respectively. Located between the angle plates is the key plate 18. The key plate 18 is a fiat plate having upper and

lower boss portions

27, 28. When the key plate 18 is inserted between the angle plates 16, 17 the surfaces 29, 30 of the key plate are parallel to the surfaces 25, 26 of the angle plates. It is to be noted that key plate 18 is disposed in a plane which extends through the center of the shaft 1, as will be seen from Fig. 2. This insures that the casing may expand in an exactly radial direction relative to pedestal 2. The

boss portions

27, 28 are substantially centrally located with respect to the key plate and extend entirely across the key plate. The bosses are adapted to be located in the recesses 31, 32 formed in the center of angle plates 16, 17. It will be noted from Figs. 3 and 4 that the

boss portions

27, 28 comprise a key member extending in a plane perpendicular to the axis of the turbine, so that the keying effect of the plate member 18 cooperating with the upper and lower members 16, 17 prevents relative axial motion between the casing and pedestal. Thus any axial thrust, due for instance to longitudinal expansion of the casing halves 5, 6 is transmitted from the lower arm 8 to the pedestal 2 through the key plate 18 without imposing any shear forces on the bolt 9. In this connection it is to be noted that the lefthand end of the casing 6 is fixed to the foundation (not shown), while the righthand end pedestal 2 is free to slide axially on the sole plate 4a, the sole plate 4a being in turn secured to the foundation (not'shown). Thus axial expansion of the turbine casing imposes a thrust, transmitted through the key plate 13 as described above, which causes the righthand pedestal 2 to slide axially on the sole plate 4a. However, this arrangement permits the inclined surfaces 25, 26 of the angle plates 16, 17 to abut and slide on the upper and lower surfaces 29, 30 of the key plate 18 to allowthe arm 8 to move in a radial direction relative to the center of the shaft 1.

The angle plates 16, 17 and the key plate 18 have 4 holes 33, 34, 35 formed therethrough respectively to allow bolt 9 to be inserted therethrough.

Referring now to Figs. 5 and 6, there is illustrated a plan and sectional view of the transverse guide for centering the turbine casing in the pedestal. The upper half 6 of the turbine casing A is provided with a lug 36 which fits into a recess 39 formed in the pedestal'Z. The lug 36 is narrower than the width of recess 3? and is aligned relative to the pedestal by angle guides 38' The guides 38 are secured in place by bolts 37. Thus any error in dimension of the lug 36 can be compensated for by changing the dimensions of the guides 38 which are readily removable and easily machined.

With the novel support assembly for the casing arms, any error in dimensions of the arm 8 or in the thickness of the blocks 16, 17 can be compensated for by varying the thickness of the plate 18. Plate 18 thus serves as a shim which can be cut to whatever size desired so that the shaft is centered inthe turbine casing. However, if desired, a process of selective assembly can be used to get a plate 18 of the right thickness to cooperate properly with a given arm 8 and pedestal 2. Because of the enormous size of the arm 8 and the pedestal 2 it is difficult to machine them to extremely exact tolerances. However, with the use of the intermediate key plate 18 it is not necessary that the surfaces of the arm 8 and pedestal 2 be machined so precisely since any local inaccuracies can be taken up by selective fitting of the shim 18.

The key plate 18 can be taken out and placed in a surface grinder to vary its thickness. Due to its small size the key plate can be cut and finished very accurately and handled very easily instead of having to swing the enormous casing half 6 back on amachine to machine offthearmS.

The support assembly B may be made of other and more expensive materials than the casing or pedestal to prevent galling and provide for free sliding. The angle plates 16, 17 are separateand therefore can be made of material most suitable for the purpose. The angle plates can be hardened while keeping the keey in a soft condition for easy machining or if desired the key may be hardened and the angle plates kept soft. Thus'it can be seen that the support assembly due to its ease of handling and compactness can be easily machined to exact tolerances and can be made of various materials as desired to prevent galling and provide for free sliding between the casing arm and pedestal. 7

Since the center plane through key plate 18 passes through the axis of shaft 1, any distortion caused by the application of heat to the turbine casing A will take place in a direction radial to the center of the turbine shaft thereby maintaining the shaft in substantially the exact center of the bearing mounted in pedestal 2. With such supports for the casing A the centerline for the casing will remain coincident with that of the shaft under all conditions of temperature changes. This can best be seen by referring to Fig.2. As the casing temperature increases, the casing metal represented by distance R expands, but the metal thickness of the. shell arm also increases proportionately with the result that tapered block 16 slides along key plate 18, maintaining the x-x surface of the casing shell arm at constant elevation.

. Thus it will be seen that the support assembly disposed between the casing and pedestal for supporting the casing on the pedestal, maintains the shaft packing and bearing ported by the arms 8. In addition, the precise geometric shape of the members 16, 17, and 18 could be modified. For instance, the key means 27 could be on the block 16 and the groove 31 in the plate 18. It is, of course, desired to cover by the appended claims all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

' l. in an elastic fluid turbine, the combination of a casing having a shaft extending therethrough, at least one bearing pedestal formed separately from the casing and having bearing means supporting said shaft, the casing having arms extending axially from the end thereof adjacent said pedestal, means supporting each casing arm on the pedestal and comprising a pair of angle plate memers having opposed substantially parallel inclined surfaces secured to the casing arm and pedestal respectively, a key plate member interposed between the angle plates and having a first outer surface abutting and adapted to slide on an inclined surface of an adjacent angle plate, said key plate member being so oriented relative to the casing that the plane containing said first surface pass-es substantially through the centerline of the shaft, whereby the desired location of the casing arm relative to the pedestal may readily be effected during assembly by removing and machining the key plate member without substantially disturbing the pedestal or removing the casing.

2. In an elastic fluid turbine, the combination of a casing having a shaft extending therethrough, shaft packing means preventing leakage between the casing and shaft, a bearing pedestal formed separately from the casing with bearing means supporting said shaft, at least one end of the casing having two arms diametrically spaced on either side of the shaft, and means supporting the casing arms on the pedestal, each of said support means comprising a pair of opposed angle plates defining inclined surfaces secured to the casing arm and pedestal respectively, the opposed inclined surfaces of the angle plates being substantially parallel, a key plate member disposed between the angle plates and defining parallel bearing surfaces abutting and adapted to slide on at least one of the inclined surfaces of the angle plates, the key plate member being oriented so that a longitudinal plane through the middle of the key plate passes substantially through the centerline of the shaft, whereby the thermal expansion of the casing effects relative sliding movement between the angle plates and key plate to maintain the shaft packing substantially in desired coaxial relation to the shaft.

3. An elastic fluid turbine in accordance with claim 2 in which the angle plates and key plate member disposed therebetween have interengaging key means disposed in a plane transverse to the axis of the turbine and permitting relative sliding movement between arm and pedestal along the plane through the axis of the shaft but preventing axial displacement of the casing arm relative to the pedestal.

47 An elastic fiuid turbine in accordance with claim 3 in which the key means includes key members on the opposite sides of the key plate member and keyways defined by the angle plates.

5. In an elastic fluid turbine, the combination of a casing having a shaft extending therethrough, shaft packing preventing eakage between the casing and shaft, a bearing pedestal formed separately from the casing and having bearing means supporting said shaft, at least one end of the casing having two arms diametrically spaced on either side of the shaft, means supporting each casing arm on the pedestal, said means comprising a pair of opposed angle plates defining inclined surfaces secured to the casing arm and pedestal respectively, the opposed inclined surfaces being substantially parallel, a key plate member disposed between the angle plates and defining parallel bearing surfaces abutting and adapted to slide on at least one of the inclined surfaces of the angle plates, the longitudinal plane through the middle of the key plate passes substantially through the centerline of the shaft whereby the thermal expansion of the casing effects sliding movement of at least one of the angle plates on said key plate to maintain the shaft packing in desired coaxial relation to the shaft, the casing arm and support means defining aligned holes therethrough, and a bolt extending through said holes into a' threaded recess defined by said pedestal to secure the casing arm and support means to the pedestal, the bolt being smaller in diameter than said holes to allow for limited relative sliding movement between the arm, support means, and pedestal.

6. In an elastic fluid turbine, the combination of a casing having a shaft extending through shaft packing means,'a bearing pedestal formed separately from the casing and having bearing means supporting said shaft, the casing being divided into upper and lower halves with each of said halves having arms extending from its ends, said arms on the respective halves of the casing being disposed vertically adjacent each other when the casing is bolted together, means for supporting each of the pair of casing arms on the pedestal, said means comprising angle plates having opposed inclined surfaces and which are secured to the casing arm and pedestal respectively, the opposed inclined surfaces of the angle plates being parallel and defining radially disposed keyways therein, a key plate disposed between the angle plates and defining outer surfaces which are parallel to the adjacent inclined surfaces of the angle plates, the key plate having radially disposed keys on its opposite sides and adapted to fit into the keyways in the angle plates to prevent axial displacement of the casing arm relative to the pedestal, the longitudinal plane through the middle of the key plate passing substantially through the centerline of the shaft thereby allowing the casing arm to slide in a radial direction relative to the centerline of the shaft to maintain the shaft packing coaxial with the shaft irrespective of thermal expansion of the casing, the casing arms and support means defining aligned holes therethrough, bolt means extending through said holes and into a threaded recess defined in said pedestal to secure the arm extending out from the lower half of the casing and support means to the pedestal, the bolt being smaller in diameter than said holes to effect limited relative sliding movement between the casing arms, support means, and pedestal.

7. In an elastic fluid turbine, the combination of a casing having a shaft extending therethrough, shaft packing for preventing leakage between the casing and shaft, a bearing pedestal formed separately from the casing and having bearing means supporting the shaft, the casing being divided into upper and lower halves with each of said halves having extended from at least one end thereof two arms having adjacent horizontal surfaces diametrically spaced on either of the shaft, said arms on the same side of the shaft being disposed vertically adjacent each other when the casing is fastened together, means supporting each pair of casing arms on the pedestal, said means comprising a pair of opposed angle plates secured to the lower casing arm and pedestal respectively, each angle plate having a flat bearing surface disposed at an acute angle to the horizontal surface of the lower casing arm, the opposed inclined surfaces of the angle plates being parallel, a key plate member disposed between the angle plates and defining parallel bearing surfaces in engagement with the inclined surfaces of the angle plates, a longitudinal plane through the middle of the key plate passing substantially through the centerline of the shaft whereby the thermal expansion of the casing effects sliding movement of the angle plates on said key plate to maintain the shaft packing in a desired fixed orientation relative to the shaft, the casing arms and support means defining aligned holes therethrough, the diameter of the hole in' the arm extending from the upper half of the casing beinglarger than the hole in the lower arm, a bolt extending through said holes into a threaded recess defined by said pedestal, a sleeve disposed in the hole in the upper arm and located between the under side of the bolt head and the upper surface of the lower arm whereby the lower casing arm and support means are secured to the pedestal by the bolt and the upper casing arm is free to expand thermally relative to said sleeve without further stretching the bolt, the bolt being smaller in diameter than said holes to eflfect limited transverse relative sliding movement between the casing arms, support means, and pedestal.

References Cited in the file of this patent UNITED STATES PATENTS