FIELD OF INVENTION
The present invention relates to a device for accurate drilling of inclined holes in nozzle
segment for hydraulic turning gear of steam turbine. More particularly, the invention
relates to a device for machining inclined holes of nozzle segment accurately so that
required torque is generated to rotate the turbine by hydraulic turning gear.
BACKGROUND OF THE INVENTION
At present machining of inclined holes is done on conventional machine therefore
accuracy of these holes gets disturbed. Since the operation is carried out without any
guidance of the tool, it is always difficult to drill inclined holes and chance of breakage
of drill is also high. As the drilling is done on a conventional machine without proper
guidance inaccurate holes result. Variation in these holes changes the angle at which
fluid should strike hence resulting in insufficient torque to rotate the turbine has been
reported from various power plants.

OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to provide a device for accurate
machining of inclined holes in nozzle segment maintaining all the geometrical
parameters which eliminates the disadvantage of the prior art.
Another object of the present invention is to provide easy and accurate machining of
inclined holes in nozzle segment.
Yet another object of the present invention is to provide required torque for proper
rotation of turbine by hydraulic turning gear.
A further object of the present invention is to reduce the cycle time of machining the
holes.
A still further object of the present invention is to provide a guide to tool while
machining thus providing better machining accuracy.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.l (a) - shows device for accurate drilling of inclined holes in nozzle segment for
hydraulic turning gear of steam turbine according to present invention.
Fig.l (b) - shows Section-AA of fig.l (a) with Guide pate (1), bolt for fixing nozzle
segment (2) with threaded hole HI.
Fig.l (c) - shows View Y of scheme shown in fig.l (a) with End Plate (3), Guide pate
(1) and bolts for clamping (4).
Fig.2 (a) - shows the Guide plate (1) of the device with threaded holes HI, inclined
holes H2 and threaded holes H3 according to an embodiment of the present invention.
Fig.2 (b) - shows End plate (3) with holes H4 for clamping according to present
invention.
Fig.2 (c) - shows Hardened Fixed bush (5) for guiding the drill according to present
invention.
Fig.3 - shows the layout of all items.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Accordingly, there is provided a device for accurate drilling of inclined holes in nozzle
segment for hydraulic turning gear of steam turbine comprising mainly of:
a) Guide plate (1)

b) Bolts (2) for fixing nozzle segment (6)
c) End plate (3)
d) Bolts for clamping (4)
e) Hardened Fixed bushes (5)
Outer diameter of Nozzle segment (6) is rested on Inner diameter of Guide plate (1)
such that the end face of nozzle segment (6) butts with the face of End plate (3) and is
fixed by bolts (2). The end plate (3) is clamped with Guide plate (1) with bolts (4).
Reference of holes is taken by end plate (3) which butts with the end face of nozzle
segment (6) and clamped with guide plate (1) by clamping bolts (4).
Hardened Fixed bushes (5) are inserted to each inclined hole H2 of Guide plate (1) for
guided drilling operation on nozzle segment (6). Hardened Fixed bushes (5) are made
of high carbon high chromium steel and then heat treated and tempered to Rockwell
hardness RC 60 and finally finished by grinding. These bushes are designed suitably to
guide the specified drill in order to maintain the geometrical and dimensional
parameters of inclined holes in nozzle segment.
The guide plate (1) of the device is equipped with threaded holes HI, inclined holes H2
and threaded holes H3.

The end plate is provided with counter bore holes H4 for bolts to clamp the end plate
with guide plates.
Fig.l (a) shows the device which comprises of a Guide plate (1). Firstly device is
assembled by clamping End plate (3) with Guide plate (1) with two bolts (4) for
clamping. Hardened Fixed bushes (5) are inserted in the inclined holes H2 of Guide
plate (1). Outer diameter of Nozzle segment is rested on inner diameter of Guide plate
(1) such that end face of nozzles segment (6) butts with face of end plate (3) so that
reference for position of holes may be taken easily. Then nozzle segment (6) is fixed by
six bolts (2) for fixing nozzle segment (6) through threaded holes HI in Guide plate (1).
WE CLAIM
1. A device for accurate drilling of inclined holes in nozzle segment for hydraulic
turning gear of steam turbine comprising:
a guide plate (1) having inclined hole H2 for guided drilling operation;
a plurality of bolts (2) for fixing nozzle segment (6) in guide plate (1);
an end plate (3) for holding the guide plate (1) and for making reference of
holes to be drilled in nozzle segment (6);
a plurality of bolts (2,4) for clamping guide plate with end plate and for fixing
nozzle segment (6) with guide plate (1);
characterised in that,
a plurality of hardened fixed bushes (5) are inserted to each inclined hole (H2) of
Guide plate (1) for guided drilling operation on nozzle segment (6).
2. A device as claimed in claim 1, wherein the hardened fixed bushes (5) are made
of high carbon high chromium steel.
3. A device as claimed in claim 1, wherein the hardened fixed bushes (5) are heat
treated and tempered to Rockwell RC 60.
4. A device as claimed in claim 1, wherein the said bushes are ground finish.

5. A device as claimed in claim 1, wherein the guide plate (1) is fixed to the nozzle
segment (6) through threaded holes (H1) by six bolts (2).
6. A process for accurate drilling of inclined holes in nozzle segment for hydraulic
turning gear of steam turbine comprising:
clamping the end plate (3) with guide plate (1) with a plurality of bolts;
fixing the nozzle segment with guide plate (1) through threaded holes HI;
resting the outer diameter of nozzle segment (6) on inner diameter of Guide
plate (1) butting its end face with face of end plate (3) to take reference for
position of holes; wherein hardened fixed bushes (5) are inserted to each
inclined holes H2 of guide plate (1) for guided drilling operation.

A device for accurate drilling of inclined holes in nozzle segment for hydraulic turning
gear of steam turbine comprises of a guide plate (1) having inclined hole H2 for guided
drilling operation when nozzle segment (6) is fixed with guide plate (1) by bolts (2). An
end plate (3) holds the guide plate and makes reference of holes on the nozzle segment
(6) for making the drilled holes. A plurality of hardened fixed bushes (5) is inserted to
each inclined holes (H2) of guide plate for guided drilling operation on nozzle segment
(6).