U.S. patent number 3,658,438 [Application Number 05/094,847] was granted by the patent office on 1972-04-25 for segmented seating plates and anchoring means for a turbine power plant.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to William H. Coleman, Seward L. Jones, Jack J. Kalbach, Howard L. Novak, Robert C. Quinn.
United States Patent |
3,658,438 |
Coleman , et al. |
April 25, 1972 |
SEGMENTED SEATING PLATES AND ANCHORING MEANS FOR A TURBINE POWER
PLANT
Abstract
The invention relates to a segmented seating plate construction
for providing a positive anchor for tandem-connected low pressure
turbines of a turbine-generator power plant. Rectangularly arranged
seating plate segments, which are not interconnected, are provided
for each low pressure turbine. In both of the opposite central
seating plate segments for the central low pressure turbine,
located in a tandem arrangement between two other low pressure
turbines having segmented seating plates, there is provided a
keyway for restraining axial movements, such as those due to
thermal expansion of the turbines. Each of the central seating
plate segments is securely held in position by a vertically
extending anchor embedded in the concrete foundation and connected
to such segment by an eccentric bushing structure.
Inventors: |
Coleman; William H. (Broomall,
PA), Quinn; Robert C. (Glen Mills, PA), Novak; Howard
L. (Broomall, PA), Kalbach; Jack J. (West Chester,
PA), Jones; Seward L. (Claymont, DE) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
Family
ID: |
22247518 |
Appl.
No.: |
05/094,847 |
Filed: |
December 3, 1970 |
Current U.S.
Class: |
415/213.1;
248/679; 415/215.1; 248/901 |
Current CPC
Class: |
F01D
25/28 (20130101); F16M 5/00 (20130101); Y10S
248/901 (20130101) |
Current International
Class: |
F16M
5/00 (20060101); F01D 25/28 (20060101); F04d
029/00 (); F16f 015/00 (); F01d 025/24 () |
Field of
Search: |
;415/199,219
;248/19,DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Raduazo; Henry F.
Claims
What is claimed is:
1. A large machine subjected to substantial differential thermal
expansions between said machine and its foundation during
operation,
said machine having a longitudinal centerline, a plane transverse
to said longitudinal centerline and containing a transverse
centerline of said machine, and a base portion supported on a
foundation,
seating plates supported by said foundation and frictionally
engaging said base portion of said machine,
said seating plates comprising a plurality of separate unconnected
segments,
said segments including two opposed central segments having their
transverse centerlines extending along said transverse plane of
said machine,
anchoring means for anchoring each of said central segments to said
foundation,
and means for securing said machine to said central segments to
prevent movement of said machine in the longitudinal direction at
said central segments.
2. The structure recited in claim 1 and further providing means for
expansion of the machine in a horizontal plane.
3. The structure recited in claim 2 wherein the means for providing
horizontal expansion and the means for securing the machine
comprise
two keyways equally spaced on opposite sides of the longitudinal
centerline, each keyway cooperatively defined by a central seating
plate segment and the machine base portion,
and a key disposed in each of said keyways.
4. The structure recited in claim 3 wherein the keyways and keys
are disposed in a horizontal plane, and are mutually normal to the
longitudinal centerline of the machine.
5. The structure recited in claim 1 wherein the anchoring means
comprise at least one post embedded in the foundation,
each central segment defining at least one opening therein
corresponding to said post,
said post extending upwardly into said corresponding opening in the
central segment,
said post having a smaller cross-sectional dimension than said
opening and thereby defining a gap,
and means for bridging said gap in said opening between said post
and the central segment to provide a rigid connection between the
post and segment.
6. The structure recited in claim 5 wherein the bridging means
comprises a bushing member which is fitted to the post, bridging
the gap in the opening.
7. The structure recited in claim 1 wherein the anchoring means
comprise at least one post embedded in the foundation,
each central segment defining at least one opening therein
corresponding to said post,
said post extending upwardly into said corresponding opening in the
central segment,
said post having a smaller cross-sectional dimension than said
opening and thereby defining a gap,
a means for bridging said gap in said opening between said post and
the central segment to provide a rigid connection between said post
and segment,
said bridging means comprising a bushing member which is fitted
onto the post bridging the gap in the opening,
said post being eccentrically disposed in said opening and said
bushing member having a corresponding aperture which is eccentric
with respect to its outer dimension.
8. The structure recited in claim 1 wherein the anchoring means
comprise at least one post embedded in the foundation,
each central segment defining at least one opening therein
corresponding to said post,
said post extending upwardly into said corresponding opening in the
central segment,
said post having a smaller cross-sectional dimension than said
opening and jointly defining a gap therewith,
means for bridging said gap in said opening between said post and
said central segment, to provide a rigid connection between said
post and segment,
said bridging means comprising a bushing member which is fitted to
the post, bridging said gap in said opening,
said post being eccentrically disposed in said opening and said
bushing member having a corresponding aperture which is eccentric
with respect to its outer dimension, and
said post, said opening and said bushing member being circular in
cross section.
9. The structure recited in claim 1 wherein the base portion of the
machine is substantially rectangular in cross section and the
seating plate segments are arranged in a substantially rectangular
configuration to support the machine.
10. The structure recited in claim 1 wherein the seating plate
segments are rectangular in cross section.
11. The structure recited in claim 6 wherein the base portion of
the machine has access apertures of greater dimension than the
dimension of the bushing member, one of said apertures
corresponding to each opening in the seating plate.
12. The structure recited in claim 6 wherein each bushing member
and the foundation are in spaced relation, and wherein a retaining
washer is secured to the bottom of each central segment to assist
in supporting the bushing member.
13. The structure recited in claim 1 wherein a layer of grout is
placed between the foundation and the seating plates and wherein
each central segment is provided with anchor discs embedded in said
layer.
14. The structure recited in claim 1 wherein the machine is formed
of a plurality of housing units.
15. The structure recited in claim 14 wherein the units are
turbines heated by hot motive fluid which produces differential
thermal expansion in the units.
Description
BACKGROUND OF THE INVENTION
In a well known and typical tandem compound arrangement of steam
turbine casings, three low pressure turbines are arranged in line
and interconnected by push-pull tie beams. A generator and exciter
are disposed adjacent one of the end low pressure turbines, and an
intermediate pressure turbine and high pressure turbine with
intermediate bearing pedestals are disposed adjacent the other end
low pressure turbine. A steam condenser is disposed below the low
pressure turbines and along the transverse centerline of the
central low pressure turbine, while the axial center lines of the
turbine and condenser are parallel.
In the prior art, an anchored point or point of fixity is
established at the transverse centerline of the condenser and of
the central low pressure turbine. The low pressure turbine casings
respond to the same temperature increase due to changes in the heat
power cycle and generally the casings exhaust into the same
condenser. Therefore the casings and condensers expand uniformly in
all directions. However, each low pressure turbine is positioned on
its seating plate which is, in effect, a one piece unit. It is made
up on interconnected parts which act as a single plate as the
result of welding or doweling joints of adjacent seating plate
segments. Keys are inserted into keyways to fix the seating plate
to the central low pressure turbine and thereby to help prevent
movement in the axial direction (parallel to the turbine rotor
axis). Thus axial expansions of the central low pressure turbine
are directed toward the adjoining low pressure turbine,
intermediate pressure turbine and high pressure turbine in the
direction of the governor, as well as toward the adjoining other
low pressure turbine, generator and exciter in the opposite or
generator direction.
Since low pressure turbines are interconnected by push-pull tie
beams, axial expansion of the central low pressure turbines is
translated thereby to either of the adjoining low pressure
turbines, and from there, and through similar tie beams in bearing
pedestals, they are translated, in the governor direction, through
the intermediate pressure and high pressure turbines. These
push-pull tie beams, therefore, enable a continual axial thrust
between the low pressure turbines so that axial expansions of
either of the end low pressure turbines are additive to motions
imposed on it by expansion of the central low pressure turbine.
Similarly, there are other push-pull thrust members located between
the end low pressure turbine and the intermediate pressure turbine,
the intermediate pressure turbine and inboard pedestal, the
pedestal and the high pressure turbine, and the high pressure
turbine and the governor pedestal. Therefore, axial expansions of
the turbine casings act in a cumulative manner.
Likewise, there is an accumulation of the reaction forces due to
friction sliding forces between the turbines and their seating
plates and between the separate pedestals and their seating
plates.
Because of the cumulative expansion of the casings, there is a
cumulative axial thrust. Therefore the aforementioned keys and
keyways must be capable of absorbing the total net axial thrust
from axial thermal expansions or contractions of all the turbine
components, including the casings and bearing pedestals.
The axial thrust or friction force arises as a result of the local
coefficient of friction between the turbine components and their
seating plates, the axial motions, and the respective normal forces
(total vertical reactions) at each location.
The seating plates resist the above-mentioned axial thrust and
anchor the turbine to the foundation in the following manner. The
seating plates are supported on a layer of grout which, in turn, is
supported on the basic turbine-generator foundation material
(chiefly reinforced concrete).
In order to enable the seating plates to be effective in resisting
movement of the turbine casings, the plates must resist slipping at
the seating plate-to-grout interface. At this interface, there also
acts an effective coefficient of static friction and a normal force
which give rise to a stability force.
The normal force consists of three separate and distinct components
(1) the low pressure turbine machinery weight; (2) the condenser
weight reaction imposed on its supporting low pressure turbines,
or, if an expansion joint is employed between the turbine and the
condenser with the condenser bolted down solidly, an unbalanced
pressure force acts on the seating plate which, in turn, conveys
the force to the foundation; (3) the vertical clamping forces
imposed as a result of prestressing the foundation bolts. One end
of these bolts is embedded in the foundation members, and the other
end protrudes through the seating plate. The exposed ends are screw
threaded to nuts which, when tightened, apply a tensile stress to
the foundation bolts, resulting in establishment of a clamping
force on the seating plate, pressing it to the foundation.
Of the three components of the normal force described above, it
will be seen that the last mentioned, namely, the foundation bolt
clamping, is the only variable element. It can be varied by the
degree of prestress, the diameter of the bolt, and/or the number of
foundation bolts. The degree of prestress has been optimized as the
result of many years of successful service. The diameter of the
bolt has evolved to a single standard size which is related to
commercially available concrete strength. Thus, the only
controllable variable left is the number of foundation bolts. By
varying the number of foundation bolts, the total normal force is
adjusted, acting in conjunction with the static friction
coefficient at the seating plate-to-grout interface, to provide the
desired friction stability force. Occasionally, single foundation
plate cannot be practically loaded with the necessary number of
foundation bolts, in which event it becomes necessary to tie (such
as by dowel pins, tap bolts etc.) adjacent seating plates together
to obtain the combined friction stability effect of the three low
pressure turbine seating plates acting in unison.
It would be desirable to design a seating plate structure which
would reduce the large quantity of foundation structure which would
reduce the large quantity of foundation bolts presently required,
eliminate the necessity of tying the adjacent seating plates
together while giving greater flexibility in aligning the low
pressure turbine casings, and enable the substantial cost
reductions and shortening of manufacturing time.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, segmented
seating plates are provided for each of three adjoining
tandem-connected low pressure turbines, there being no
interconnection between the segments of the seating plates of any
turbine. Keyways are provided in central seating plate segments of
the central low pressure turbine, which segments are each
positively anchored to the foundation by a novel vertical post
embedded in the concrete and which, by an eccentric connection, is
fitted to he segment so as to prevent any possible movement of the
anchored segments. This arrangement eliminates the practice of
tying the adjacent seating plates together and reduces the
installation time and costs of installing a large number of
foundation bolts. Furthermore, there is greater flexibility in
aligning the low pressure turbine casings than is presently
available.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view shown partially in cross section, of
three tandem-connected low pressure turbines forming a portion of a
steam turbine-generator power plant and supported on a segmented
seating plate arrangement in accordance with the principles of the
present invention;
FIG. 2 is a plan view of the novel, segmented seating plate
arrangement for supporting the low pressure turbines shown in FIG.
1.
FIG. 3 is an enlarged plan view of the central seating plate
segment of the middle, low pressure casing shown in FIG. 2;
FIG. 4 is a further enlarged, cross-sectional view taken along
lines IV--IV of FIG. 3;
FIG. 5 is a cross-sectional view taken along lines V--V of FIG. 3
and on the same scale as FIG. 4; and
FIG. 6 is a cross-sectional view taken along lines VI--VI of FIG.
5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to FIG. 1 of the drawing, the letter T
generally denotes a portion of a compound steam turbine-generator
power plant including three low pressure turbine units connected in
tandem with each other and anchored in accordance with the present
invention. On one end of the low pressure turbines connected in
tandem, is a generator and exciter and an intermediate pressure
turbine and high pressure turbine are connected on the other as
well known in the art.
FIG. 1 shows a low pressure turbine unit having an outer casing 1,
a second or central low pressure turbine unit having an outer
casing 2, and a third low pressure turbine unit having an outer
casing 3, with their rotors (not shown) connected in tandem along a
central longitudinal axis of rotation A--A' (See FIGS. 1 and
2).
Low pressure turbine casings 1, 2 and 3 are supported on segment
seating plate groupings 4, 5 and 6, respectively, shown more
clearly in FIG. 2.
Segmented seating plate grouping 5 comprises 12 segments 7 to 18,
inclusive, made of steel in the form of rectangular blocks. An
important distinguishing feature of the present invention, compared
to seating plates of the prior art, is that the seating plate
segments for any of the low pressure turbines are mutually spaced
and not interconnected. The seating plate segments are preferably
mutually spaced on the order of 4 inches apart.
Keyways 19 and 20 are machined in two corresponding portions in
plates 8 and 14, respectively, and the foot portions 2a of the
turbine 2 (FIGS. 2, 5 and 6). The keyways extend in a horizontal
plane which is normal to the longitudinal axis A--A'. The keyways
19 and 20 are defined by the foot portion 2a of the turbine 2 and
the central opposed seating segments 8 and 14. A key 19a is
inserted horizontally into the corresponding keyway 19 and a
corresponding key (not shown) is inserted into keyway 20. Keyways
19 and 20 and their respective keys receive the total net axial
thrust force from axial thermal expansions or contractions of the
turbo-generator unit. Normally the segments 8 and 14 of the
segmented seating plate grouping 5 are too short to securely anchor
the turbine in the manner accomplished by the external keyways in
prior devices.
Assured anchorage of seating plates 8 and 14 is provided by
vertically extending anchors or posts 21 and 22 of steel (see FIG.
3) embedded in the concrete foundation 23 as shown more clearly in
FIG. 4. This assured anchorage is important because the point of
fixity of the turbo-generator unit is at seating plates 8 and 14.
Such posts 21 and 22 positively anchor the low pressure turbine
cylinder 2 against moving in a longitudinal or axial direction
(parallel to its rotor axis A--A'). The posts or anchors 21 and 22
are embedded in the concrete and during erection of the turbine
casings 1, 2 and 3, the protruding ends 21a and 22a of the embedded
posts are machined to a diameter denoted as M in FIG. 4. There is
an opening of diameter N premachined in seating plate 8 (and
14).
Also there is an access hole 0 having a larger diameter than N
which is machined in the foot 2a of the low pressure casing 2
(shown in a dot-and-dash outline). An eccentric anchor bushing 24,
preliminarily formed as a circular plate or disc machined to a
diameter N (less a small clearance for fitting) and of a thickness
approximately equal to the thickness of seating plate 8, is
provided. After final turbine alignment, the eccentricity of the
center of diameter M on the exposed end 21a of the embedded axial
post 21 is measured in relation to the center of the bore or
diameter N in the seating plate. The prefitted disc or eccentric
anchor bushing 24 is then bored to an inner diameter M (plus a
small clearance for fitting) at the required eccentricity.
The eccentric anchor bushings 24 are then installed by introducing
them through the access hole 0 in the low pressure turbine foot 2a.
The plate segment 8 is provided with a welded-on retaining ring or
washer 25 on its bottom surface which acts to maintain the proper
vertical position of the eccentric anchor bushing 24 in relation to
the seating plate thickness.
Finally, to protect the alignment of the various seating plate
segments from motions imposed by friction forces resulting from
differential values of coefficient of friction, a circumferential
series of anchor discs 26 are attached to the underside of the
seating plate segments. Such anchor discs 26 are solidly embedded
in the layer of grout G under the seating plates and on the surface
of concrete foundation 23 so as to interlock the plate segments and
provide the desired resistance to motion in the horizontal
plane.
Two keyways 27 and 28 (FIG. 2) are provided in the oppositely
disposed segments 17 and 11, respectively, which keyways are
located in parallel alignment with the longitudinal axis A--A' of
the turbine-generator. Similarly, keyways 29 and 30 are provided in
the segmented seating plate grouping 4 for casing 1 and keyways 31
and 32 are provided in the segmented seating plate grouping 6 for
cylinder 3, all in parallel alignment with the longitudinal turbine
rotor axis A--A'.
A plane B--A' transverse to the longitudinal axis A--A' of the
central low pressure turbine contains the transverse or vertical
center line 34 of the turbine, while transverse planes C--C' and
D--D' contain vertical joint lines 35 and 36, respectively.
Separately constructed sections 42, 43 and 44 are bolted together,
along the vertical joint lines 35 and 36. Each section has a base
portion and a cover portion. Section 43 is the central casing
portion having a central inlet in the cover portion and sections 42
and 44 are the end casing portions. Through the base portions of
sections 42, 43 and 44, the steam is exhausted downwardly to
condensing equipment (not shown), as well known in the art. The
centers of the gaps between the axially directed seating plate
segments 7, 8, 9, 13, 14 and 15 are located approximately
coincident with the above mentioned vertical planes C--C' and
D--D'. Variations in the elevational setting of the low pressure
turbine foot adjacent casing base sections are readily tolerated.
This allows for much less precision machining of the casing
sections 42, 43 and 44 since each seating plate segment can be
adjusted vertically to support the corresponding casing section. As
an example, up to 0.25 inches of vertical tolerance on turbine
casing sections is allowable as compared to 0.001 inches previously
allowable.
It should be noted that each of the seating plate segments 7 to 18,
inclusive, is independently set to an elevation compatible with the
turbine casing dimensions and the overall bearing alignment scheme.
This allows various adjustable leveling devices, well known in the
art, to position each seating plate segment to support the turbine
casings with an optimum distribution of normal forces on the
seating plates. Previously, with the unitary seating plate,
concentrated forces at the turbine casing foot 2a and at the
vertical joints 35 and 36 would result from any mismatch in
elevation, and required expensive and time consuming hard finishing
operations to preclude gouging of the seating plate and subsequent
misalignment problems.
Foundation anchor bolts, such as 37, are disposed all along the
longitudinal centerlines extending through all the segments of each
of the seating plate groupings 4, 5 and 6.
To ensure cumulative expansion of the low pressure turbine units
about the point of fixity at the center of the low pressure turbine
unit 2, push-pull tie beams 38 and 39 are secured to the foot area
of the adjacent end casing base portions of the units 2 and 3 and
similar beams 40 and 41 are secured to the foot area of the
adjacent end casing bases of units 1 and 2.
Variations may be made in the shape of the ends 21a and 22a of the
anchor post 21 and 22, respectively, that is, they may be made
rectangular or polygonal with corresponding shaped anchor bushings
24, instead of round as described.
Furthermore, the segmented seating plate construction described for
this tandem arrangement of three low pressure turbines may be
applied to any other tandem or cross compound arrangement of low
pressure turbines to realize similar benefits and advantages to
those herein enumerated. An additional advantage of the present
structure is that it considerably reduces the required number of
foundation anchor bolts resulting in savings on associated design
details. Additionally, a major load reduction occurs because,
whereas in the existing or well known design described above under
Background of the Invention, the transverse anchor design load
results as a function of a differential friction force at the
seating plate-to-grout interface in the present invention the
transverse anchor design load results as a function of a
differential friction force at the turbine base-to-seating plate
interface. The latter has an inherently lower coefficient of
friction as well as the complete absence of foundation anchor bolt
clamping forces in the normal or vertical direction. This tends to
reduce transverse anchor loads by about one one-third.
Smaller plate sections will have the same relative movement to the
grout due to differential thermal expansion, but this movement will
no longer be cumulative, therefore, this should add measurably to
stabilizing the turbine alignment throughout the operating life of
the machinery.
Thus it is seen that a segmented seating plate structure with
eccentric anchoring means is provided, which seating plate
structure is unconnected, more reliable, less expensive, and which
structure greatly reduces the number of foundation anchor bolts
because it is no longer necessary to use them to augment the
friction stability forces previously described, and provides more
aligning flexibility than is presently available. Because of the
increase in associated tolerances, the seating plates and turbine
casings do not have to be prefitted before erection at the plant
site and the eccentric anchors permit erection in less time than
heretofore. Furthermore, the following are eliminated: welding and
machining of dowel pinned and bolted lap joints in adjacent
sections of seating plates; heat treating seating plates; machining
the lower surface of the seating plates thereby reducing
fabrication thickness; and finishing operation to custom fit the
turbine keyways; the severe vertical tolerance limitation on
turbine casings; and precise thickness matching at adjacent
sections of seating plates.
Since numerous changes may be made in the above-described
construction and different embodiments of the invention may be made
without departing from the spirit and scope thereof, it is intended
that all subject matter contained in the foregoing description or
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
* * * * *