FIELD OF INVENTION
This invention relates generally to Kaplan and Francis type Hydro turbines. More
particularly, the invention relates to a threaded adapter in the Pivot Ring of
Kaplan and Francis type Hydro Turbines for maintaining a fine working clearance
at the the top and bottom of guide vanes.
BACKGROUND OF THE INVENTION|(
The turbine components generally affecting the guide vane clearances viz. Stay
ring, pivot ring, top cover and the guide vanes are configured to precision
tolerance dimensions. Hydro turbines being large in size, it is difficult to
configure the components to match the level of fine tolerances. Further, the
components like stay ring, which are embedded in concrete, get distorted, As a
result Of these problems/limitations It is normally difficut to achieve a fine
working clearance at the top and the bottom of guide vanes. However the
problem can beobviated by maintai ning larger values of guide vane top and
bottom clearances. Such a solution on the other hand leads to a problem of
excessive water leakage. This excessive leakage leads to further problems of
creeping of the rotating parts of the turbine generator.
According to existing design of the hydro turbines of the type described herein
above, the pivot ring is rigidly fixed to the stay ring and the runner envelope.
Hence raising or lowering the pivot ring to maintain the desired guide vane
clearances is not readily possible.
For large turbines, maintenance of optimum guide vane clearances requires a
huge amount of remedial grinding work of the pivot ring seating area and of the
areas where the top cover rests on the stay ring, to achieve the required guide
vane clearances. Further, a problem arises in respect of the guide vane
clearances when the liner on the pivot ring and the top cover wears out.
Additionally, the larger values of guide vane top and bottom clearances calls for
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a requirement to maintain the thrust bearing of the generator constantly under
forced lubrication thereby increasing the operating cost. In the conventional
practice, grinding of pivot ring seating face to achieve horizontality of the pivot
ring and to achieve guide vane top and bottom clearances is unavoidable which
is very laborious and time consuming.
OBJECTS OF THE INVENTION
It is an object of the invention to propose a Threaded Leveling Adaptor
interposed in the Pivot Ring for achieving and maintaining a required fineworking clearance at the top and the bottom of guide vanes,
Another object of the invention is to propose a Threaded Leveling Adaptor
interposed in the Pivot Ring, which allows an easy raising and lowering of the
Pivot ring.
Yet another object of the invention is to propose a Threaded Leveling Adaptor"
interposed in the Pivot Ring to eliminate the need of a remedial grinding work of
the Pivot ring resting area on stayring thereby reducing the machining, erection,
and commissioning time.
A further object of the invention is to propose a Threaded Leveling Adaptor
interposed in the Pivot Ring, which enables readjustment and redistribution of
the guide vane clearances when the liner plates on the pivot ring and the top
cover wear out,
A still further object of the invention is to propose a Threaded Leveling Adaptor
Interposed in the Pivot Ring that permits a lower top and bottom guide vane
clearances than that can be achieved by prior art, thus eliminating the problems
of creeping of turbine rotating parts and consequent necessity of Keeping the
generator thrust bearing under forced lubrication.
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SUMMARY OF THE INVENTION
Thus, in one aspect of the present invention there is provided a device for
achieving an optimum guide vane clearance in Kaplan and Francis type hydro
turbines, comprising: a pivot ring rigidly fixed on one of a runner envelope, and a
stay ring the pivot ring having female threads internally configured into a bottom
bore; guide vane of the turbine forming a top clearance in respect of a top cover
and a bottom clearance in respect of the pivot ring; characterized in that a
threaded level adaptor comprising a clearance hole, a counter bore for
accommodating holding down bolt is interposed in the pivot ring, and in that the
threaded adaptor being releasably fixed to the pivot ring via a male thread
configured on an outer diameter of the adaptor.
In a second aspect of the invention, there is provided a method to achieve an
optimum guide vane clearance in Kaplan and Francis type hydro turbine in a
device described hereinabove.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - Shows a conventional arrangement of a pivot ring of a Kaplan and
Francis type hydroturbine.
Fig. 2 - Detailed view of the conventional arrangement of the pivot ring
Fig. 3 - Shows a Threaded Leveling adaptor interposed in the Pivot ring of a
Francis type hydroturbine according to one aspect of the invention.
Fig. 4 - Detailed View of a Threaded Leveling adaptor interposed in the Pivot |
ring according to one aspect of the invention.
Fig. 5 - View of the Threaded Leveling adaptor showing the level adjustment of
the Pivot ring according to another aspect of the invention.
Fig. 6 - Exploded view of the Leveling adaptor in Pivot ring detailing the
sequence of operation according to another aspect of the invention
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Fig. 7 - A targetted view of the Threaded Leveling adaptor according to the
present invention
Fig. 8 - Isometric view of the Threaded Leveling adaptor according to the
invention.
Fig. 9 - Isomeric view of a specially designed box spanner for turning the
Threaded level adaptor.
Fig. 10 - Isometric view showing keys of box spanner
engaging with keyways in leveling adaptor.
Fig. 11 - Cut section of the pivot ring showing threads for accommodating the
Threaded leveling adaptor of the invention.
Fig. 12 - Cut section of the pivot ring showing the threaded leveling adaptor of
the present invention positioned above the pivot ring.
Fig. 13 - Cut section of the pivot ring showing assembly of the threaded leveling
adaptor in the pivot ring by the special box spanner according to the invention.
Fig. 14 - Cut section of the pivot ring showing assembly of the threaded leveling
adaptor in the pivot ring using the specially designed box spanner according to
the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Figures 1 and 2 show an arrangement according to the prior art in which the
pivot ring (3) is rigidly fixed on runner envelope (4), or on a stay ring (5) as
shown in fig - 2. Atleast one guide vane (1) of the turbine forms a top clearance
(TC) in respect of a top cover (2), and a bottom clearance (BC) in respect of the
other turbine components for example, the pivot ring (3), the stay ring (5)
and/or the runner envelope (4) which makes it difficult to achieve an optimum
clearance for the guide vane (1). The guide vane height (H) as shown excludes
the guide vane clearances.
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Figure 3 - shows an arrangement in which a threaded leveling adaptor (13) is
interposed in the pivot ring (3) to achieve an optimum guide vane clearance.
Figure 11 - shows that the Pivot ring (3) having female thread (15) on a bottom
bore instead of a simple clearance / cylindrical hole. Within the threaded hole of'
the pivot ring (3) is accommodated an adaptor (13) having male threads (16).
The adaptor (13) has a central hole (12) for accommodating a holding down bolt
(6) and a counter bore (11) For accommodating the bolt head of the holding
down bolt (6).
The adaptor has two diametrically opposite slots milled on the top face. A special
type of box spanner, which has two projecting keys. The keys engage In the,
slots of the adaptor and rotation of the adaptor is effected by turning a handle of
the box spanner.
There is a central hole / bore in the box spanner through which a conventional
hexagonal socket with an extension bar is inserted for tightening the central
holding down bolt. The best mode of carrying out the invention may include:
carrying out a trial assembly of the Top cover and the Pivot ring on the Stay ring.
In the conventional practice grinding of pivot ring seating face to achieve
horizontality of Pivot ring and to achieve guide vane top and bottom clearances
is unavoidable which is very laborious and time consuming. Measuring the
existing guide vane passage height (H) between the pivot ring and the top cover;
determining the required guide vane passage height (H) on the basis of the
measured value of the guide vane height; operating the box spanner to
determine and position the threaded level adaptor within the pivot ring so as to
achieve the required guide vane passage height (H); and locking the adaptor at
the determined position by means of the holding down bolt which additionally
holds the pivot ring and the stray ring at said location.
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WE CLAIM
1. A device for achieving an optimum guide vane clearance in Kaplan and
Francis type hydro turbines, comprising:
- a pivot ring (3) bolted on stay ring (4), the pivot ring (3) having
female threads (15) internally configured into a bottom bore;
- atleast one guide vane (1) of the turbine forming a top clearance
(TC) in respect of a top cover (2) and a bottom clearance (BC) in
respect of the pivot ring (3); characterized in that a threaded
level adaptor (13) comprising a clearance hole (12), a counter
bore (11) for accommodating holding down bolt (6) is interposed
in the pivot ring (13), and in that the threaded adaptor (13) being
reieasably fixed to the pivot ring (3) via a male thread (16)
configured on an outer diameter of the adaptor (13).
2. The device as claimed in claim 1, comprising a box-type spanner (7)
having a handle (7b) and atleast two projecting keys (10).
3. The device as claimed in claim 1, wherein a hexagonal socket (9)
operative by means of an extension bar (7c) is inserted for tightening and
/ or loosering the hoidlng down bolt (6).
4. The device as claimed in claim 1, wherein the threaded level adapter (13) '
having atleast two slots (8) for rotating the adaptor (13) by means of the
handle (7b) of the box spanner (7).
5. A method for achieving an fine working guide vane clearance in Kaplan
and Francis type hydroturbine, comprising the steps of :
- the best mode of carrying out the invention may include:
- carrying out a trial assembly of the Top cover (2) and the Pivot
ring (3) on the Stay ring (5);
- in the conventional practice grinding of pivot ring seating face to
to achieve horizontality of Pivot ring and to achieve guide vane
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