METHOD OF RE-BUILDING FRANCIS TURBINE RUNNERS

METHODE DE RECONSTRUCTION DES ROUES MOBILES DES TURBINES FRANCIS

English Abstract

A hydraulic turbine power house or installation has a rotatably mounted
runner having a crown, a band and a plurality of original runner blades
extending between the crown and the band. A method of retrofitting the
runner with improved performance comprises the steps of removing the
runner from the turbine power house or installation, removing the original
runner blades from the crown, machining the surface of the crown to smooth
the surface adjacent the removed original runner blades, affixing new runner
blades with improved characteristics to the crown, securing the band to the
runner blades to complete the assembly of the retrofitted runner, and re-
installing the retrofitted runner in the turbine power house or installation.

French Abstract

Une centrale ou installation à turbine hydraulique dispose d'une roue mobile montée en rotation avec une couronne, une bande et une pluralité d'aubes de roue mobile d'origine, s'étendant entre la couronne et la bande. Un procédé de rénovation de la roue mobile pour améliorer ses performances comprend les étapes de dépose de la roue mobile de la centrale ou installation à turbine hydraulique, dépose des aubes de roue mobile d'origine de la couronne, usinage de la surface de la couronne pour lisser la surface adjacente aux aubes de roue mobile d'origine déposées, fixation sur la couronne de nouvelles aubes de roue mobile présentant des caractéristiques améliorées, fixation solide de la bande sur les aubes de roue mobile afin de terminer l'assemblage de la roue mobile rénovée, et réinstallation de la roue mobile rénovée dans la centrale ou installation à turbine hydraulique.

Claims

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WHAT IS CLAIMED IS:
1. A method of retrofitting a hydraulic turbine runner for improved
performance, the turbine runner having a crown and a plurality of original
runner blades extending between the crown and an original band, the method
comprising the steps of:
removing the original runner blades from the crown adjacent a surface
of the crown;
affixing new runner blades with improved characteristics to the crown;
and,
securing one of the original band and a new band to the new runner
blades to complete assembly of a retrofitted runner.
2. The method of claim 1 further including the step of:
machining the surface of the crown to smooth the surface adjacent
where the original runner blades have been removed.
3. The method of claim 1 wherein the step of securing the band to
the new runner blades comprises securing the original band to the new
runner blades.
4. The method of claim 1 wherein the step of affixing the new
runner blades to the crown comprises welding the new blades to the surface
of the crown.
5. The method of claim 1 wherein the method further includes the
step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
6. The method of claim 2 wherein the method further includes the
step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
7. The method of claim 3 wherein the method further includes the
step of adding material to the crown to modify the crown to lay over and
support the new runner blades.

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8. The method of claim 4 wherein the method further includes the
step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
9. The method of claim 3 further including the step of adding
material to the original band to modify the original band to lay over and
support the new runner blades.
10. In a hydraulic turbine power house having a rotatably mounted
runner having a crown, an original band and a plurality of original runner
blades extending between the crown and the original band, a method of
retrofitting the runner for improved performance comprising the steps of:
removing the runner from the turbine power house;
removing the original runner blades from the crown adjacent a surface
of the crown;
machining the surface of the crown to smooth the surface adjacent
where the original runner blades have been removed;
affixing new runner blades with improved characteristics to the crown;
securing one of the original band and a new band to the new runner
blades to complete assembly of a retrofitted runner; and,
re-installing the retrofitted runner in the turbine power house.
11. The method of claim 10 wherein the step of securing the band
to the new runner blades comprises securing the original band to the new
runner blades.
12. The method of claim 10 wherein the step of securing the band
to the new runner blades comprises securing a new band to the new runner
blades.
13. The method of claim 10 wherein the step of affixing the new
runner blades to the crown comprises welding the new blades to the surface
of the crown.

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14. The method of claims 10 wherein the method further includes
the step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
15. The method of claims 11 wherein the method further includes
the step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
16. The method of claims 12 wherein the method further includes
the step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
17. The method of claim 11 further including the step of adding
material to the original band to modify the original band to lay over and
support the new runner blades.
18. The method of claims 17 wherein the method further includes
the step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
19. In a hydraulic turbine installation having a rotatably mounted
runner having a crown, an original band and a plurality of original runner
blades extending between the crown and the original band, a method of
retrofitting the runner for improved performance comprising the steps of:
removing the runner from the turbine installation;
removing the original runner blades from the crown adjacent a surface
of the crown;
machining the surface of the crown to smooth the surface adjacent
where the original runner blades have been removed;
affixing new runner blades with improved characteristics to the crown;
securing one of the original band and a new band to the new runner
blades to complete assembly of a retrofitted runner; and,
re-installing the retrofitted runner in the turbine installation.

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20. The method of claim 19 wherein the step of securing the band
to the new runner blades comprises securing a new band to the new runner
blades.
21. The method of claim 19 wherein the step of affixing the new
runner blades to the crown comprises welding the new blades to the surface
of the crown.
22. The method of claims 19 wherein the method further includes
the step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
23. The method of claim 20 wherein the method further includes the
step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
24. The method of claims 21 wherein the method further includes
the step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
25. The method of claim 20 further including the step of adding
material to the original band to modify the original band to lay over and
support the new runner blades.
26. The method of claim 25 wherein the method further includes the
step of adding material to the crown to modify the crown to lay over and
support the new runner blades.
27. The method of any one of claims 1 to 26 wherein the hydraulic
turbine runner is one of a Francis hydraulic turbine runner and a pump turbine
runner.

Description

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METHOD OF RE-BUILDING FRANCIS TURBINE RUNNERS
Field of the Invention
The present invention relates to a hydraulic turbine runner and, in
particular, to a method of re-building a Francis turbine or pump turbine
runner
utilizing the existing crown of the runner.
Background Of The Invention
The output performance of hydro-electric power houses or installations
that are twenty or more years old in operation may be improved by replacing
the existing runner with a new runner whose blade design improves the
efficiency of operation of the turbine and/or the power output of the turbine.
Typically, after twenty or more years of operation, the turbine runner blades
operate with less efficiency and power output due to wearing of the runner
blades. Further, substantial improvements in blade configuration have been
made in the last twenty years.
Replacement of the turbine runner at a hydro-electric installation
typically involves removing the turbine runner from the power house and
replacing the old turbine runner with a new runner. The new turbine runner
comprises a crown, a series of blades attached to the crown and a band
surrounding the blades. The construction and assembly of each one of these
replacement runners is time consuming and costly. Further, the turbine
power house typically has anywhere from two to six or more turbines
operating within the power house. These turbines are replaced one at a time

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since it is necessary for the power house to continue to generate hydro-
electric power for the electrical power grid.
Accordingly, there is a need to provide these power houses with
turbine runners of improved output performance which are less costly to
manufacture than complete newly assembled turbine runners and are more
quickly manufactured to reduce the time required to replace all turbine
runners in the power house.
Summary of The Invention
The present invention relates to a method of retrofitting a hydraulic
turbine runner for improved performance whose blade design has improved
characteristics that improve the efficiency of operation of the turbine and/or
power output of the turbine runner. The method involves retrofitting a
hydraulic turbine runner for improved performance by removing the original
runner blades from the crown of the turbine runner. The method
subsequently affixes new runner blades with improved characteristics to the
crown and secures a band to the new runner blades to complete assembly of
a retrofitted runner. The band may comprise either a new band or the original
band reworked and affixed to the runner blades. Accordingly, the method of
the present invention provides retrofitting the runner with new runner blades
while reusing the crown and optionally permitting reuse of the band.
In one application of the invention, when replacing the turbine runners
in a power house, a first turbine runner may be replaced with a complete
newly assembled turbine runner. This allows for the power station to continue
to operate with all turbine generators operating and permits for the removed
runner to be retrofitted with new runner blades. By re-using the crown,
significant cost savings in the manufacture of the retrofitted runner is
recognized and the assembly of the retrofitted runner is typically quicker
than
assembling a complete runner including a new crown. This permits the next
runner to be replaced in the hydro-electric power house to be removed and
replaced with the retrofitted runner. As can be appreciated, in a power house
having four hydro-electric installations with four turbine runners, it may
only be

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necessary to replace one of the installations with a new runner and the other
three installations may be replaced with retrofitted runners thereby providing
a
substantial replacement cost benefit to the hydro-electric power plant.
The method may further comprise machining the surface of the crown
adjacent the original runner blades to smooth this surface prior to the step
of
affixing the new runner blades with the improved characteristics.
In an embodiment where the runner blades have lengths that are
larger then the original runner blades, additional material is added to the
surfaces of the crown so that the crown continues to lay over and support the
runner blades.
In one embodiment a new band is utilized and in another embodiment,
the original band is utilized and additional material may be added so that the
original band lays over and supports any changes in the size of the
replacement runner blades relative to the original runner blades.
In another embodiment a hydraulic turbine power house has a
rotatably mounted runner having a crown, an original band and a plurality of
original runner blades extending between the crown and the original band.
The method of retrofitting the runner for improved performance comprises of
the steps of:
removing the runner from the turbine power house;
removing the original runner blades from the crown adjacent a surface
of the crown;
machining the surface of the crown to smooth the surface adjacent
where the original blades have been removed;
affixing new runner blades with improved characteristics to the crown;
securing one of the original band and a new band to the new runner
blades to complete assembly of a retrofitted runner; and,
re-installing the retrofitted runner in a turbine power house.

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It should be understood that retrofitting may include re-building which
may include repair and/or dismantling and reassembly with improved parts for
a single turbine runner.
Brief Description of The Drawings
For a better understanding of the nature of the present invention
reference may be had to the accompanying diagrammatic drawings in which:
FIG. 1 is an elevational view, partially in cross-section, of a Francis
turbine installed in a turbine installation of a power house;
FIG. 2 is an illustration of a Francis-type turbine shown removed from
the power house; and,
FIG. 3 is a partial sectional view showing the re-built runner.
Detailed Description Of The Invention
The present invention relates to a hydraulic turbine runner and, in
particular, to a method of re-building a Francis turbine or pump turbine
runner
utilizing the existing crown of the runner. It should be understood that any
reference to turbine throughout the specification and claims may also equally
refer to a pump-turbine.
Referring to FIG. 1 a portion of a turbine installation 10 of a power
house is illustrated for use in the generation of hydroelectricity. It should
be
understood that in a power house, several turbine installations are typically
located beside each other. This could range from two to six and more turbine
installations 10 in the same power house or adjoining power houses at one
hydro-electric power site.
Each turbine installation 10 has a water passageway 12. Water flows
from an inlet 14 of passageway 12 to an outlet 16 located at a lower
elevation. The water passageway 12 passes through a Francis turbine 18
having a turbine runner 20 and a draft tube 22. The runner 20 is secured by
bolts 24 to a shaft 26 transmitting energy to a generator (not shown). The
turbine 18 is mounted in a stationary casing 28 having a head cover 30 and a
bottom discharge ring 32. The head cover 30, discharge ring 32 and draft

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tube 22 are embedded in concrete foundation 34. The draft tube 22 is also
shown to diverge outwardly as the draft tube 22 extends in the downstream
direction.
It should be understood that installation 10 includes other components
such as, for example, stay vanes and wicket gates which are not shown.
Runner 20 is rotabily mounted in casing 28. The runner 20 has a
crown 36 and a plurality of circumferentially spaced original runner blades 38
extending therefrom to an enclosing band 40. The runner 20 is better shown
in FIG. 2 as a one piece assembly of the crown 36, runner blades 38 and the
band 40. The original runner 20 may be assembled by welding or may have
been formed as a one-piece casting.
In accordance with a preferred aspect of the method of the present
invention, the runner 20 is removed from the installation 10 and shipped back
to a turbine manufacturer for retrofitting. The retrofitting is accomplished
by
removing the runner blades 38 by cutting these blades from or adjacent the
surface 60 of the crown 36.
The crown 36 is then machined so that its surface 60 is smoothed
adjacent to where the runner blades 38 were previously affixed; thereby
removing any excess blade material not removed from the crown 36 when the
blades 38 are removed from the crown 36.
Next, new runner blades 80 as shown in FIG. 3, are attached to the
surface 60 of the crown 36 by means of welding. As shown in FIG. 3, each
new runner blade 80 has trailing and leading edges 50, 52 which are
displaced downstream and upstream of corresponding trailing and leading
surfaces 46 and 48 of the removed runner blade 38 as represented by broken
lines in FIG. 3. As a consequence, the crown 36 has material added to its
outer periphery 41. This material may be added by welding and is shown at
42. The material 42 is provided so that the refurbished crown 36 lays over
and supports the new blade 80.
In FIG. 3, the original band 40 is also utilized and affixed to the new
blade 80 by means of welding. The original band 40 also has additional

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material 44 added to one end of the band 40. It should be understood that in
an alternative method, a new band of material may be affixed, by welding, to
the blade 80 to complete the assembly of the new or retrofitted runner 82.
Further, it should be understood that the shape of the new blades 80 may
differ from the shape of the original blades 38 whereby the new blades have
improved characteristics.
The retrofitted runner 82 is then shipped back to the power house
where it is re-installed.
While the invention has been described in connection with the above
detailed description, it is to be understood to those skilled in the art that
various modifications and arrangements may be made without departing from
the scope of the invention described and claimed.

Representative Drawing