Adjustable axial positioning device

Abstract

A positioning device for positioning mating members of a turbine apparatus casing. Two threaded pins are retracted within one of the mating members before the members are placed in their assembled mated relationship. The pins are advanced after assembly to within a predetermined operating clearance of the other member to maintain the members a predetermined distance from each other.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to turbine apparatus, and in particular, to an adjustable positioning device for maintaining predetermined axial position between mated cylinders of a turbine apparatus.

2. Description of the Prior Art:

A casing for an axial flow steam turbine apparatus is usually comprised of one or more inner cylinder members nested within and disposed concentric to an outer cylinder. Since the inner cylinder directly conducts the high temperature motive steam along a flow path within the turbine, it is the inner cylinder which becomes heated to the higher temperature. The higher temperature of the inner cylinder causes an increased rate of thermal expansion for this cylinder, as compared to the concentrically disposed outer cylinders. The differing expansion rates and magnitudes generate the problem of maintaining the axial alignments between the nested cylinders at their predetermined clearances. This is especially important, because misalignment of the cylinders axially could possibly lead to abrasion between the rotating and stationary elements within the turbine, the axial clearances of which depending upon the axial relationships between the cylinders.

In order to make the cylinders act as a single unit and maintain their axial positioning throughout all conditions of operation, prior art has keyed the cylinders together along their horizontal centerlines. Presently, two methods for maintaining axial alignment between mated cylinders disposed radially adjacent each other are used.

Present construction of turbine casings uses, on the inner cylinder, a radially-outwardly-extending horizontal joint flanged protrusion which mates with a corresponding slot disposed on the horizontal joint flange of the next radially adjacent cylinder. One method of maintaining axial position between the inner and the next radially adjacent outer cylinders is to dispose on each axial side of the flanged protrusion an L-shaped member. The short leg of each L-shaped member overlaps and is rigidly secured to the ledge on the outer cylinder which defines the slot therein. The elongated leg of the L-shaped member extends between the axial faces of the flanged protrusion and the side walls of the slot. In this way axial displacement of the inner cylinder relative to the radially adjacent outer cylinder due to a higher rate and magnitude of thermal expansion in the inner cylinder is restrained while freely allowing the corresponding differential expansion of these cylinders in the direction transverse to the rotor axis. However, each L-shaped member must be machined to accurately fit, at initial erection, between the flanged protrusion and the side walls of the slot. Often, however, these members must be re-machined at assembly, when the actual dimensions of the available space between the flange and the slot becomes more precisely known. This added complexity and re-machined, of course, increases the cost of assembly of a turbine using L-shaped axial aligning members.

A more recent innovation for axially positioning the inner and radially adjacent outer cylinders is through the use of a vertical dowel pin fastened on one inner cylinder base and fitted into a slot on the mating cylinder base. Thus, alignment is established with cylinder bases only, which provides a considerable advantage. The cover portions are dowel bolted to their respective bases to complete the assembled clearance and functional relationship. This method, however, requires utilization of custom-machined dowel pins to securely and snugly engage the slot. Custom fitting of any part obviously adds to the cost of fabrication and assembly, and, for this reason, is disadvantageous.

SUMMARY OF THE INVENTION

This invention discloses an adjustable axial positioning device for maintaining a predetermined axial clearance between mated inner and outer cylinders for an axial flow turbine apparatus. The invention retractably disposes threaded pins in an axial bore extending through a flange protrusion mounted on the inner cylinder of the turbine apparatus. The pins are threaded into the axial bore from each axial direction before the flange is inserted into a corresponding slot opening disposed in the outer cylinder. After the flange is inserted to provide a mating relationship between the inner and outer cylinders, each pin is adjusted axially until a predetermined clearance between each pin and the outer cylinder is obtained. Advancing the pins to within the predetermined clearance of the outer cylinder locates the flange, and therefore the inner cylinder, a predetermined axial distance away from the outer cylinder. The pins are then secured within the axial bore extending through the flange by suitable locking means.

It is an object of this invention to provide an adjustable axial positioning device on adjacent cylinder bases so as to maintain axial position of an inner cylinder of a turbine apparatus with respect to a radially adjacent outer cylinder thereof. It is a further object of this invention to provide an axial positioning device that is not custom machined to correspond to clearances which vary from assembly to assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an isometric view of an axial flow turbine apparatus, having portions removed for clarity, and showing the location of a device for positioning concentric turbine cylinder members embodying the teachings of this invention;

FIG. 2 is a plan view of an axial positioning device taught by this invention in a retracted position within the inner cylinder member; and,

FIG. 3 is a plan view, similar to FIG. 2, showing the axial positioning device embodying the teachings of this invention in an extended configuration between the concentric cylinder members of the turbine.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the following description, similar reference characters refer to similar elements in all figures of the drawings.

Referring first to FIG. 1, an isometric view of the base half of an axial flow turbine apparatus 10, having two concentrically disposed inner cylinders 12 and 14 and a concentric outer cylinder 16 is shown. In FIG. 1, there is shown a lower half, or base, portion 18 of the outer cylinder 16 having connected axially thereto the lower halves, or bases, of end members 20 and 22. Disposed radially-inwardly from the outer cylinder base 18 is the lower half, or base 24 of the inner cylinder 14. This outermost-inner cylinder is known in the art as the inner cylinder No. 2. Disposed radially inwardly from the inner cylinder No. 2 base 24 is the lower half, or base, portion 26 of the innermost inner cylinder 12, known in the art as inner cylinder No. 1. Inner cylinder No. 1 confines and guides a high temperature motive fluid, such as steam, through alternating arrays to produce rotational mechanical energy therefrom. The entire turbine arrangement 10 is mounted and supported by a foundation 28.

In FIG. 1, the horizontal joint surfaces of the base 26 of inner cylinder No. 1 and the base 24 of the inner cylinder No. 2 are cross-hatched to provide a clearer understanding of the nested relationship between the cylinders. Omitted from FIG. 1, for clarity, are the cover portions which correspond to each of the base portions shown in FIG. 1. Of course, when the base and cover portions are joined along the horizontal centerlines thereof, a completely integrated casing arrangement for the turbine 10 is provided. It is to be understood that any number of corresponding base and cover portions may be joined together to provide any predetermined number of concentric cylindrical arrangements to satisfy the pressure containment and guidance requirements for a particularized turbine apparatus. In general, the positioning device taught by this invention is applicable to position an inner cylinder with respect to a radially adjacent outer cylinder, even if that outer cylinder is itself concentric to and disposed within yet another outer cylinder member.

Referring to FIGS. 1 and 2, the base 26 of the inner cylinder No. 1 has disposed at a predetermined axial location 32 thereon a radially outwardly extending flange portion 34, which, when inserted into a slot 36 disposed on the interior surface of the base 24 of the inner cylinder No. 2 at a corresponding axial position thereon, provides a mated relationship between the base 26 of the inner cylinder No. 1 and the base 24 of the inner cylinder No. 2. Since the inner cylinder No. 1 is most directly exposed to the high pressure and high temperature motive fluid, it is the inner cylinder No. 1 which undergoes a higher rate and magnitude of differential thermal expansion than does the other concentric cylinder members.

It is especially important that the nested arrangement of the inner cylinders be maintained in axial alignment relative to each other throughout all temperatures within the operating range of the turbine 10. For this purpose, there is provided a positioning device 38 for maintaining the cylinders in their locations relative to each other. With the inner cylinder No. 1 expanding at a greater rate than the inner cylinder No. 2, if the relative axial positions of the cylinders were not maintained, possible abrasion between the rotating members and stationary members of the turbine could occur. The rotating blade members of the turbine are disposed on a shaft member (not shown) while the stationary blading (not shown) is disposed in annular arrays in planes perpendicular to the rotor axis and affixed to slots 40 which are disposed circumferentially about the interior of both the base portion 26 and the cover portion (not shown) of the inner cylinder No. 1.

In the prior art, various methods of maintaining axial position between the mated inner and outer cylinders are utilized. However, the two most widely used methods of providing and maintaining axial displacement and alignment both require the use of custom-fitted spacer members. In one configuration, a pair of custom-machined L-shaped support braces is disposed between the flanged projection mounted on the inner cylinder and the corresponding surfaces of the slot disposed in the outer cylinder. In another configuration, the inner and outer cylinders are maintained axially aligned by the use of a custom machined dowel pin fastened on one cylinder and fitted into a slot on the mating cylinder. However, since custom-machining is required for both configurations, increased cost of assembly and fabrication are a natural concomitant to the use of such aligning arrangements.

Referring to FIGS. 2 and 3, it is to be noted at the outset that the positioning device taught by this invention requires no custom-machining. It is to be understood that although the Figures shows the positioning device 38 utilized to maintain axial positioning between concentric inner cylinder members 12 and 14 of a turbine casing, the device taught by this invention can be utilized in any portion of the turbine where predetermined clearances are required to be maintained. For example, the device taught by this invention can be utilized to maintain alignment between the anchor and aligning features for the turbine.

In FIGS. 2, and 3, the flange 34, which is disposed within the slot 36, has a first and a second axial surface 42 and 44, respectively, thereon. The surfaces 42 and 44 are substantially parallel to each other and parallel to corresponding first and second axial surfaces 46 and 48 which define the slot 36. The axial breadth 52 of the flange 34 is less than the axial breadth 54 of the slot 36. Extending axially through the flange 34 is a threaded bore 56.

In order to assure the axial positioning of the flange 34 relative to the slot 36, and thereby assure the axial positioning of the inner cylinders 12 and 14 relative to each other, a first and a second threaded pin, 58 and 60 respectively, is inserted axially into the threaded bore 56 extending through the flange 34 before the flange 34 is inserted into the slot 36 to provide the mated relationship between the adjacent inner cylinders. Since the axial clearances between the flange 34 and the slot 36 are quite small, being on the order of 1 inch axially from corresponding faces 42 and 46, and 44 and 48, on the flange 34 and slot 36 respectively, both pins 58 and 60 are rotated by the use of suitable means so that the substantially entire axial length of each threaded pin is completely inserted within the bore 56 extending through the flange 34. When inserted, the entire axial length measured from axial edge of protruding pin 58 to the opposite axial edge of protruding pin 60 is less than the axial breadth 54 of the slot 36.

To facilitate insertion of the threaded pins 58 and 60, a plurality of radially bored openings 62 are distributed circumferentially about one end of each pin 58 and 60. Thus, any suitable means which engages the openings 62 may be utilized to threadedly insert the pins 58 and 60 into the axial bore 56 disposed through the flange 34.

Once the pins 58 and 60 are threadedly inserted a sufficient distance into the bore 56, within the flange 34 to permit the flange 34 to be inserted into the corresponding slot 36 (FIG. 2), the base portion 26 of the inner cylinder No. 1 is then inserted into the base portion 24 of the inner cylinder No. 2 so that the flange 34 having the threaded bolts 58 and 60 engaged therein is disposed completely within the slot 36 (FIG. 3). It is to be noted, however, that the plurality of radial openings 62 in each pin 58 and 60 are at all times available for engagement by the rotating means. It is also to be noted that any number of corresponding flange and slot arrangements may be utilized and that only one threaded pin member may be disposed within the bore extending through the flange. It is to be understood however, that any device which utilizes threaded pins to axially position concentrically disposed cylinder member for a turbine apparatus is within the contemplation of this invention.

After the concentric inner cylinders have been nested by the insertion of the flange 34 into the corresponding slot 36, axial alignment between the nested cylinders is assured by adjusting pins 58 and 60 axially outward in the bore 52 until a predetermined clearance 64 between the ends of each pin 58 and 60 and the side surface 46 and 48 of the slot 36 is established (FIG. 3). By providing the small predetermined clearance 64 between the axial ends of the pins 58 and 60 and the side walls 46 and 48 of the slot 36, the surfaces 42 and 44 of the flange 34 are maintained a predetermined axial distance from the corresponding surfaces 46 and 48 of the slot 36. As the cylinders expand and contact laterally with respect to each other, there may be occasional contact between one or the other of these members. To avoid solid binding interferences, the nested cylinders are provided with a small "cold" clearance 64. However, it is to be recognized that since the inner cylinder No. 1 is subjected to greater temperatures than inner cylinder No. 2, therefore, the "hot" clearance between the nested cylinders is even smaller than the initial cold clearance. The pins 58 and 60 are advanced by the insertion of the appropriate rotation tool into the radial openings 62 and the rotation of each pin 58 and 60 in a direction so as to advance the threaded pins 58 and 60 axially out of the slot 56. In addition to maintaining axial positioning between the nested cylinders, the device 38 described by this invention can be used to correctly align the innermost cylinders No. 1 with respect to the concentrically disposed inner cylinder No. 2. This eliminates the need for temporary devices now utilized to position the inner cylinder No. 1 with respect to the axis of the rotor (not shown). Thus, in addition to using the threaded pins 58 and 60 to maintain the correct clearances 64 (FIG. 3), the pins 58 and 60 may be utilized to push the inner cylinder No. 1 into its correct alignment relative to the rotor axis.

Once the axial positioning between the base portions of the inner cylinders has been provided, by extending the pins 58 and 60 to obtain the clearance 64, the positioning alignment of the completed fabricated cylinder, comprising both the covers and the bases, can be maintained. It is worthy of note however, that adjustments to the axial position of the inner cylinder relative to outer cylinder can be made after the insertion of the flange 34 into the slot 36. Since, the openings 62 are always accessible, adjustments through the use of the adjusting means can be made. In addition, it is seen that once the axial location of the base portion 26 of the inner cylinder No. 1 has been maintained relative to the base 24 of the inner cylinder No. 2, the alignment of the completely fabricated cylinders, comprising both cover and base, is guaranteed.

Since the positioning device described by this invention is always accessible, even after assembly, it is seen that prior art devices, such as those described in U.S. Pat. Nos. 2,247,387 and 2,247,423, differ from the positioning device taught by this invention. Of course, both devices in the aforementioned patents relate to vertical positioning of diaphragm members within the casing and thus are structurally different and utilized for different functions, it is also to be noted that the only access to the positioning screws utilized in the aforementioned patents can only be had before the corresponding halves of the diaphragm are connected. Once the lower and upper diaphragm halves are joined, access to the positioning means described in these U.S. patents is precluded.

However, since the circular array of radial bore openings 62 disposed on the threaded pins 58 and 60 is at all times accessible for engagement by the suitable displacement means, axial positioning of the inner cylinder No. 1 relative to the inner cylinder No. 2 can be adjusted to conform to the predetermined optimum displacement even after the inner cylinder No. 1 has been completely fabricated. The positioning device taught by this invention can be periodically adjusted through the simple expedient of advancing the pins 58 and 60 axially into or axially out of the bore 56. It is also to be noted that the axial positioning device taught by this invention requires the use of no custom-machined elements, thus providing an increased cost savings over the devices utilized in the prior art.

Once the precise positioning between the inner cyliners has been provided, and the pins 58 and 60 have been threaded axially outwardly in the bore 56 so that the predetermined small clearance 64 between the edge of the pins and the side surfaces 46 and 48 of the slot 36 is provided, the pins are secured in their axial positions. For this purpose, radial bores 66 and 68, the number of radial bores, of course, depending upon the number of threaded pins utilized in the particular embodiment of the invention, are disposed in the flange 34. Once the pins have been advanced to their optimum axial locations, in order to maintain the optimum axial spacing between the nested cylinders suitable locking means, such as set screws or drive pins 70 and 72 are radially inserted into the bores 66 and 68 until the locking screws 70 and 72 engage and secure the threaded pins 58 and 60 within the bore 56. Thus, any axial displacement of the pins relative to the bore 56 of the flange 34 is prevented through utilization of the locking features 70 and 72.

In summmary, it can be seen that the disposition of an axially extending threaded bore within a mounting flange on the inner cylinder of a turbine apparatus and the provision of at least one, and preferably a pair, axially advanceable threaded pins thereinto provides a novel and unobvious device for maintaining axial positioning of an inner cylinder of an axial flow turbine apparatus relative to a radially adjacent outer cylinder. It can also be seen that the device taught by this invention permits achievement of initial (and subsequent) optimal alignment between inner cyliner No. 1 and inner cylinder No. 2 of an axial flow steam turbine apparatus.

Claims

What we claim is:

1. A casing for an axial flow turbine apparatus comprising:

an inner cylinder,

an outer cylinder surrounding and mating with said inner cylinder, and,

means for positioning said inner cylinder with respect to said outer cylinder, said positioning means being disposed within said inner cylinder, said positioning means being adjustable after said inner cylinder is mated with said outer cylinder.

2. The casing of claim 1 wherein:

said outer cylinder has a slot therein,

said inner cylinder has a mating flange thereon, said flange being disposed within said slot to provide mating relationship between said inner and said outer cylinders, said flange having a threaded bore extending therethrough,

said positioning means comprising a threaded pin, said pin being threaded into said bore in said flange before said flange is disposed within said slot,

said pin being displaceable within said bore after said flange is disposed within said slot until a predetermined clearance between said pin and said outer cylinder disposes said flange a predetermined distance away from said outer cylinder.

3. The casing of claim 2 wherein:

said bore extends axially through said flange, and,

wherein abutting contact between said pin and said flange disposes said flange axially away from said outer cylinder said predetermined distance.

4. The casing of claim 3 further comprising:

means for securing said pin within said bore.

5. The casing of claim 1 wherein:

said outer cylinder has a slot therein,

said inner cylinder has a mating flange thereon, said flange being disposed within said slot to provide mating relationship between said inner and said outer cylinders, said flange having a threaded bore extending axially therethrough,

said positioning means comprising a first and a second threaded pin, said first and said second pins being threaded axially into said bore in said flange before said flange is disposed within said slot,

said first and second pins being advanceable within said bore after said flange is disposed within said slot until a predetermined clearance between said first pin and said outer cylinder and between said second pin and said outer cylinder disposes said flange in a predetermined axial position relative to said outer cylinder.

6. The casing of claim 5 further comprising:

means for securing said first pin and said second pin within said bore.

7. A device for positioning a first member relative to a second member, said first and said second members being in a mated relationship, said first member having a threaded opening therein, said device comprising:

a threaded pin extending into said bore, said pin being disposed within said bore before said first and said second members occupy said mated relationship, said pins being advanceable within said bore after said first and said second members occupy said mated relationship until a predetermined clearance between said pin and said second member disposes said first member a predetermined distance away from said second member.

8. The device of claim 7 wherein said bore extends axially through said first member and,

said abutting contact between said pin and said second member disposes said first member axially away from said second member for said predetermined distance.