Title of Invention	A DRILLING FOR CONFIGURATING ROOT HOLES ON ROOT BLADES
Abstract	This invention relates to a drilling device for configurating root holes on rotor blades, in particular pin-type rotor blades of turbines, comprising a drilling fixture (4') having a U-shaped clamp (5) for forming atleast one pin-hole (9) on a disc (4) of the rotor blade, the clamp (5) having atleast two concentric rings (6) disposed at both ends of ithe clamp; a plurality sets of stepped bushes (7) having outer diameters selected in correspondence with an internal diameter of the concentric rings (6), the internal diameters of said plurality set of stepped bushes (7) varying in incremental steps; a pin (3) insertable in the atleast one pin—hole (9). The internal diameter of each of the plurality sets of bushes (7) mounted on the atleast two rings (6) correspondingly matching the diameter of the pin-hole (9) under drilling.

Title of Invention

A DRILLING FOR CONFIGURATING ROOT HOLES ON ROOT BLADES

Abstract

This invention relates to a drilling device for configurating root holes on rotor blades, in particular pin-type rotor blades of turbines, comprising a drilling fixture (4') having a U-shaped clamp (5) for forming atleast one pin-hole (9) on a disc (4) of the rotor blade, the clamp (5) having atleast two concentric rings (6) disposed at both ends of ithe clamp; a plurality sets of stepped bushes (7) having outer diameters selected in correspondence with an internal diameter of the concentric rings (6), the internal diameters of said plurality set of stepped bushes (7) varying in incremental steps; a pin (3) insertable in the atleast one pin—hole (9). The internal diameter of each of the plurality sets of bushes (7) mounted on the atleast two rings (6) correspondingly matching the diameter of the pin-hole (9) under drilling.

Full Text	FIELD OF INVENTION:- This invention relates to manual drilliiig of holes at the roots of pin-type turb'ms hhdds of turho-gdnerator s^ts during replacement of failed blades BACKGROUND OF INVENTIQN:- Turbo-generator (TG) sets generate electricity which is always in great demand. Therefore, failure of TG sets need to be rectified within the shortest period to ensure minimum generator loss. Failure of turbine blades is quite a common phenomena Majority of such failures are repaired at site itself to minimize the down time. The replacement job undertaken at site is predominantly manual. It is always executed under severe space constraints and constant pressure for the fastest complstioa of the job. The first casualty in such severs working conditions is the accuracy of the work, which again determines the frequency of future failures. DESCRIPTION OF PRIOR ARt;- As per existing prior art, pin-tj'pe blade replacement involves following manna! operations: i) Removal of the faulty blades after cutting open the covering ring called shroud and the fixing pins located in the disc; ii) Fitting of new blades in place of the faulty ones; iii) Centering the new blades in the exact location of the faulty blades, marking and removal of the new blades; iv) Drilling undersized holes in the new blades' root manually with drilling machines for fitting pins. This operation is done outside the turbine, on the markings on the roots; v) Reassembling the new blades on the turbine disc; vi) M^uaily drilling the holes on the blades' roots to enlarge the hole dimneter to the desired size in several small incremental steps; vii) Fitting the pins in finished holes to fmally fix the new blades in position and viii) Refixing tlie shroud. In the repair process described above, the major problems that come up are a) The manual drilling described under vi) ^ove often results in ttq)ered drill holes. After several such operttfions, the final dimneter of the drilled holes may turn out to be much beyond the designed and desired tolerance limits. This not only results in ill-fitting pins, at times this renders the whole turbine rotor unfit for repairs at site. In a typical example, a tolerance limit of 0.2mm was specified, but the manual drilling resulted in 1.0mm toler^ce i.e, 5 times the desired tolerance value. b) Secondly, due to the delicate nature of the manual operation, it becomes very slow. In a typical example, only 2 holes can be fmisb drilled in one single day. This has a great bearing on the down-time of the T-G set. OBJECTS OF THE EWENTIQNi- The invention described hereunder addresses both problems listed under a) and b) above. The blade root hole drilling fixture guides the drill accurately during manual drilling at site so that the finish drilled hole remains within the prescribed tolerance by ahnost totally eliminating taper in the drill holes. In typical example, a finished hole drilled with the help of the invented fbcture had a tolerance of 0.2mm i.e, the prescribed tolerance. Secondly, the speed of execution also goes up remarkably when the fixture is used. In an exajnple, the number of finished holes made with the help of this llxture went up from 1 per day to 10 per day. SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a drilling device for configurating root holes on rotor blades* in particular pini-type rotor blades of turbine comprising: - a drilling fixture having a U-shaped clamp for forming at least one pin-hole on a disc of the rotor blade^) the the clamp having atleast two concentric rings disposed at both ends of the; clamp; - a plurality sets of stepped bushes having outer diameters selected in correspondence with an internal diameter of the concentric rings, the internal diameters of said plurality set of stepped bushes vary- ing incremental steps; - a pin insertable in the atleast one pin-hole» characterised in that the internal diameter of each of the plurality sets of bushes mounted on the atleast two rings correspondingly matching the diameter of the pin- hole under drilling. Further, according to a second aspect of the invention there is provided a method of manual drilling of root holes on rotor blades in a fixture as claimed in claim 1» comprising the steps of! - positioning the rotor blade in the disc having pin- holes; - placing the drilling fixture in an inverted u—position on the rotor blade) and snug-fitting atleast one pair of bush on the rings of the drilling fixture such that the bushes are aligned co-axially with the pin-hole; - carrying out atleast one manual drilling operation to configure a root-hole; on the rotor blade in which the atleast one pair of bush guiding the atleast one manual drilling operation to maintain coaxiality of the configurable rotor blade root-hole; repeating the manual drilling operation using additional pair of bushes having a. stepped incremental internal diameter to complete the' configuration of the root-holej and removing the following drilling fixture when the root- hole is configured. DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The invention will be described with the help of the following drawings;- Fig.l-shows the generation of taper drill holes in the blade roots when repaired as per prior art, i.e, without the help of the invented fixture. Fig.2- shows the elevation of the pin-type turbine blade m assembled condition. fixture as per the present invention. Fig.4- shows the method of using the guide fixture as per the present invention while in use for drilling the root holes. Fig.l shows the formation of the error (taper) in the drilling operation, when the fixture as per the invention has not been used (prior art). Blade (1) is fitted in disc (4) and pin-hole (9) is drilled manually. The pin hole (9) has an original and a desired axis (10) which runs parallel to the turbine axis (not shown in drawing). Due to manual drilling, a taper axis (11) is created. The pin-type turbine rotor blades are normally operational in the turbine as depicted in Fig.2. The blade (1) has roots (2) protrudmg downwards which are placed in aileast one hole provided in the disc body (4). The pins (3) are fitted through the holes ninning parallel to the turbine axis to keep the blade in firm hold on the disc. When such a blade develops faults, for example developing cracks due to mechanical or thermal shocks, it fails and leads finally to the stoppage of the turbine and outage of the TG set. In order to bring the TG set back into generation with minimum down-time, replacement of such faulty blades is takeniup immediately at site. Fig.3 shows the invented fixture (4' ) for root hole drilling. The fixture consists of a V type clamp (5) having rings (6) fitted at both ends. The inner surface of both the rings are accui-ately machined and the rings are made perfectly concentric. They also must be coaxial when fixed Ito the U-cIamp. Several sets of stepped bushes (7) are manufactured separately. These bushes have their outer diameter just marginally less than the internal diameter of the rings so that any bush has a snug fit mside a ring. The internal diameter of the bushes vary in small incremental steps. These bushes (7), when fitted inside the rings, act as guides to the manual drill operations in small incremental steps. Fig.4 shows the fixture as per the invention in use. The fixture (4*) is fitted in "inverted u" position on to the disc (4), where the turbine blade (1) is already fitted. The two rings (6) of the fixture contain one bush (7) each, the internal diameter of the bushes being appropriate for the intended driiting operation. Fig.4 shows one pin (3) already fixed; in position after drilling operation carried out with the help of the fixture and the next pin-hole (9) being readied for driiling. WE CLAIMS 1. A drilling device for configurating root holes on rotor bladeS, in particular pin-type rotor blades of turbinees, comprising: a drilling fixture (4') having a U-shaped clamp (5) for forming atleast one pin-hole (9) on a disc (4) of the rotor blade, the clamp (5) having atleast two concentric rings (6) disposed at both ends of the clamp; - a plurality sets of stepped bushes (7) having outer diameters selected in correspondence with an internal diameter of the concentric rings (6), the internal diameters of said plurality set of stepped bushes (7) varying in incremental steps; - a pin (3) insertable in the atleast one pin-hole (9), characterized in that the internal diameter of each of the plurality sets of bushes (7) mounted on the atleast two rings (6) correspondingly matching the diameter of the pin-hole (9) under drilling. 2. A method of manual drilling of root holes on rotor blades in a fixture as claimed in claim 1, comprising the steps of s - positioning the rotor blade (1) in the diac (4) having pin-holes (9); - placing the drilling fixture (4') in an inverted u-position on the rotor blade (1), and snug-fitting atleast one pair of bush (7) on the rings (6) of the drilling fixturel (4') such that the bushes (7) are aligned co—axially with the pin—hole (9); - carrying out atleast-one manual drilling operation to configure a root-hole on the rotor blade (1) in which the atleast one pair of bush (7) guiding the atleast one manual drilling operation to maintain coaxiality of the configurable rotor blade root—hole, - repeating the manual drilling operation using addit- ional pair of bushes (7) having a stepped incremental internal diameter to complete the con- figuration of the root—holes and - removing the fallowing drilling fixture (4') when the root-hole is configured. 3. A drilling device for configurating root holes on turbine root blades as substantially herein described and illustrated with reference to the accompanying drawings. This invention relates to a drilling device for configurating root holes on rotor blades, in particular pin-type rotor blades of turbines, comprising a drilling fixture (4') having a U-shaped clamp (5) for forming atleast one pin-hole (9) on a disc (4) of the rotor blade, the clamp (5) having atleast two concentric rings (6) disposed at both ends of ithe clamp; a plurality sets of stepped bushes (7) having outer diameters selected in correspondence with an internal diameter of the concentric rings (6), the internal diameters of said plurality set of stepped bushes (7) varying in incremental steps; a pin (3) insertable in the atleast one pin—hole (9). The internal diameter of each of the plurality sets of bushes (7) mounted on the atleast two rings (6) correspondingly matching the diameter of the pin-hole (9) under drilling.

Full Text

FIELD OF INVENTION:-
This invention relates to manual drilliiig of holes at the roots of pin-type
turb'ms hhdds of turho-gdnerator s^ts during replacement of failed blades
BACKGROUND OF INVENTIQN:-
Turbo-generator (TG) sets generate electricity which is always in great
demand. Therefore, failure of TG sets need to be rectified within the
shortest period to ensure minimum generator loss.
Failure of turbine blades is quite a common phenomena Majority of such
failures are repaired at site itself to minimize the down time.
The replacement job undertaken at site is predominantly manual. It is
always executed under severe space constraints and constant pressure for the
fastest complstioa of the job. The first casualty in such severs working
conditions is the accuracy of the work, which again determines the
frequency of future failures.
DESCRIPTION OF PRIOR ARt;-
As per existing prior art, pin-tj'pe blade replacement involves following
manna! operations:
i) Removal of the faulty blades after cutting open the covering ring
called shroud and the fixing pins located in the disc;
ii) Fitting of new blades in place of the faulty ones;
iii) Centering the new blades in the exact location of the faulty blades,
marking and removal of the new blades;
iv) Drilling undersized holes in the new blades' root manually with
drilling machines for fitting pins. This operation is done outside
the turbine, on the markings on the roots;
v) Reassembling the new blades on the turbine disc;
vi) M^uaily drilling the holes on the blades' roots to enlarge the hole
dimneter to the desired size in several small incremental steps;
vii) Fitting the pins in finished holes to fmally fix the new blades in
position and
viii) Refixing tlie shroud.
In the repair process described above, the major problems that come up
are
a) The manual drilling described under vi) ^ove often results in
ttq)ered drill holes. After several such operttfions, the final
dimneter of the drilled holes may turn out to be much beyond
the designed and desired tolerance limits. This not only results in
ill-fitting pins, at times this renders the whole turbine rotor unfit
for repairs at site. In a typical example, a tolerance limit of 0.2mm
was specified, but the manual drilling resulted in 1.0mm toler^ce
i.e, 5 times the desired tolerance value.
b) Secondly, due to the delicate nature of the manual operation, it
becomes very slow. In a typical example, only 2 holes can be
fmisb drilled in one single day. This has a great bearing on the
down-time of the T-G set.
OBJECTS OF THE EWENTIQNi-
The invention described hereunder addresses both problems listed under a)
and b) above.
The blade root hole drilling fixture guides the drill accurately during manual
drilling at site so that the finish drilled hole remains within the prescribed
tolerance by ahnost totally eliminating taper in the drill holes. In typical
example, a finished hole drilled with the help of the invented fbcture had a
tolerance of 0.2mm i.e, the prescribed tolerance.
Secondly, the speed of execution also goes up remarkably when the fixture
is used. In an exajnple, the number of finished holes made with the help of
this llxture went up from 1 per day to 10 per day.

SUMMARY OF THE INVENTION
According to a first aspect of the invention there is
provided a drilling device for configurating root holes on rotor
blades* in particular pini-type rotor blades of turbine
comprising:
- a drilling fixture having a U-shaped clamp for forming
at least one pin-hole on a disc of the rotor blade^) the
the clamp having atleast two concentric rings disposed
at both ends of the; clamp;
- a plurality sets of stepped bushes having outer
diameters selected in correspondence with an internal
diameter of the concentric rings, the internal
diameters of said plurality set of stepped bushes vary-
ing incremental steps;
- a pin insertable in the atleast one pin-hole»
characterised in that the internal diameter of each of
the plurality sets of bushes mounted on the atleast two
rings correspondingly matching the diameter of the pin-
hole under drilling.
Further, according to a second aspect of the invention there
is provided a method of manual drilling of root holes on rotor
blades in a fixture as claimed in claim 1» comprising the steps
of!
- positioning the rotor blade in the disc having pin-
holes;
- placing the drilling fixture in an inverted u—position
on the rotor blade) and snug-fitting atleast one pair
of bush on the rings of the drilling fixture such that
the bushes are aligned co-axially with the pin-hole;
- carrying out atleast one manual drilling operation to
configure a root-hole; on the rotor blade in which the
atleast one pair of bush guiding the atleast one manual
drilling operation to maintain coaxiality of the
configurable rotor blade root-hole;
repeating the manual drilling operation using additional
pair of bushes having a. stepped incremental internal
diameter to complete the' configuration of the root-holej
and
removing the following drilling fixture when the root-
hole is configured.
DESCRIPTION OF A PREFERRED EMBODIMENT OF
THE INVENTION
The invention will be described with the help of the following drawings;-
Fig.l-shows the generation of taper drill holes in the blade roots when
repaired as per prior art, i.e, without the help of the invented fixture.
Fig.2- shows the elevation of the pin-type turbine blade m assembled
condition.

fixture as per the present invention.
Fig.4- shows the method of using the guide fixture as per the present
invention while in use for drilling the root holes.
Fig.l shows the formation of the error (taper) in the drilling operation, when
the fixture as per the invention has not been used (prior art). Blade (1) is
fitted in disc (4) and pin-hole (9) is drilled manually. The pin hole (9) has an
original and a desired axis (10) which runs parallel to the turbine axis (not
shown in drawing). Due to manual drilling, a taper axis (11) is created.
The pin-type turbine rotor blades are normally operational in the turbine as
depicted in Fig.2. The blade (1) has roots (2) protrudmg downwards which
are placed in aileast one hole provided in the disc body (4).
The pins (3) are fitted through the holes ninning parallel to the turbine axis
to keep the blade in firm hold on the disc. When such a blade develops
faults, for example developing cracks due to mechanical or thermal shocks,
it fails and leads finally to the stoppage of the turbine and outage of the TG
set.
In order to bring the TG set back into generation with minimum down-time,
replacement of such faulty blades is takeniup immediately at site.
Fig.3 shows the invented fixture (4' ) for root hole drilling. The fixture
consists of a V type clamp (5) having rings (6) fitted at both ends. The
inner surface of both the rings are accui-ately machined and the rings are
made perfectly concentric.
They also must be coaxial when fixed Ito the U-cIamp. Several sets of
stepped bushes (7) are manufactured separately. These bushes have their
outer diameter just marginally less than the internal diameter of the rings so
that any bush has a snug fit mside a ring. The internal diameter of the bushes
vary in small incremental steps. These bushes (7), when fitted inside the
rings, act as guides to the manual drill operations in small incremental steps.
Fig.4 shows the fixture as per the invention in use. The fixture (4*) is fitted
in "inverted u" position on to the disc (4), where the turbine blade (1) is
already fitted. The two rings (6) of the fixture contain one bush (7) each, the
internal diameter of the bushes being appropriate for the intended driiting
operation.
Fig.4 shows one pin (3) already fixed; in position after drilling operation
carried out with the help of the fixture and the next pin-hole (9) being
readied for driiling.
WE CLAIMS
1. A drilling device for configurating root holes on rotor
bladeS, in particular pin-type rotor blades of turbinees,
comprising:
a drilling fixture (4') having a U-shaped clamp
(5) for forming atleast one pin-hole (9) on a
disc (4) of the rotor blade, the clamp (5) having
atleast two concentric rings (6) disposed at both
ends of the clamp;
- a plurality sets of stepped bushes (7) having outer
diameters selected in correspondence with an
internal diameter of the concentric rings (6), the
internal diameters of said plurality set of stepped
bushes (7) varying in incremental steps;
- a pin (3) insertable in the atleast one pin-hole
(9), characterized in that the internal diameter of
each of the plurality sets of bushes (7) mounted
on the atleast two rings (6) correspondingly
matching the diameter of the pin-hole (9) under
drilling.
2. A method of manual drilling of root holes on rotor
blades in a fixture as claimed in claim 1, comprising the steps
of s
- positioning the rotor blade (1) in the diac (4)
having pin-holes (9);
- placing the drilling fixture (4') in an inverted
u-position on the rotor blade (1), and snug-fitting
atleast one pair of bush (7) on the rings (6) of
the drilling fixturel (4') such that the bushes (7)
are aligned co—axially with the pin—hole (9);
- carrying out atleast-one manual drilling operation
to configure a root-hole on the rotor blade (1) in
which the atleast one pair of bush (7) guiding
the atleast one manual drilling operation to
maintain coaxiality of the configurable rotor
blade root—hole,
- repeating the manual drilling operation using addit-
ional pair of bushes (7) having a stepped
incremental internal diameter to complete the con-
figuration of the root—holes and
- removing the fallowing drilling fixture (4') when
the root-hole is configured.
3. A drilling device for configurating root holes on
turbine root blades as substantially herein described and
illustrated with reference to the accompanying drawings.

This invention relates to a drilling device for configurating root holes on rotor blades, in particular pin-type rotor blades of turbines, comprising a drilling fixture (4') having a U-shaped clamp (5) for forming atleast one pin-hole (9) on a disc (4) of the rotor blade, the clamp (5) having atleast two concentric
rings (6) disposed at both ends of ithe clamp; a plurality sets of stepped bushes (7) having outer diameters selected in correspondence with an internal diameter of the concentric rings
(6), the internal diameters of said plurality set of stepped bushes (7) varying in incremental steps; a pin (3) insertable in the atleast one pin—hole (9). The internal diameter of each of
the plurality sets of bushes (7) mounted on the atleast two rings (6) correspondingly matching the diameter of the pin-hole (9) under drilling.

Documents:

00239-kol-2005-abstract.pdf

00239-kol-2005-claims.pdf

00239-kol-2005-correspondence-1.1.pdf

00239-kol-2005-correspondence.pdf

00239-kol-2005-description(complete).pdf

00239-kol-2005-drawings.pdf

00239-kol-2005-form-1.pdf

00239-kol-2005-form-18.pdf

00239-kol-2005-form-2.pdf

00239-kol-2005-form-3.pdf

239-KOL-2005-FORM-27-1.pdf

239-KOL-2005-FORM-27.pdf

239-kol-2005-granted-abstract.pdf

239-kol-2005-granted-claims.pdf

239-kol-2005-granted-correspondence.pdf

239-kol-2005-granted-description (complete).pdf

239-kol-2005-granted-drawings.pdf

239-kol-2005-granted-examination report.pdf

239-kol-2005-granted-form 1.pdf

239-kol-2005-granted-form 18.pdf

239-kol-2005-granted-form 2.pdf

239-kol-2005-granted-form 3.pdf

239-kol-2005-granted-gpa.pdf

239-kol-2005-granted-reply to examination report.pdf

239-kol-2005-granted-specification.pdf

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Patent Number

237906

Indian Patent Application Number

239/KOL/2005

PG Journal Number

03/2010

Publication Date

15-Jan-2010

Grant Date

12-Jan-2010

Date of Filing

29-Mar-2005

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

REGIONAL OPERATIONS DIVISION (ROD), PLOT NO: 9/1, DJBLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI-110049, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	GUPTA GANPATILAL	AGM (STE/PSE/CDE), BHEL, BHOPAL
2	CARPENTAR BRAJ MOHAN	FOREMAN, STM, BHEL, BHOPAL
3	NIMJE ASHOK KASHINATH	SR. DGM, STE, BHEL, BHOPAL

PCT International Classification Number

B27B 41/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA