FIELD OF INVENTION
The present invention relates to a device for checking chamfer at exit edge root of
freestanding fir-tree blades of low pressure steam turbine. More particularly, the
present invention relates to a device for checking the chamfer at exit edge root of fir-
tree blades to achieve proper fitting in low pressure steam turbine shaft.
BACKGROUND OF INVENTION
Freestanding low pressure steam turbine blades are mainly made by precision forging
for profile of the blade and the root is manufactured by form milling cutter. Due to
freestanding nature, rigidity and quality of these blades highly depend upon the
manufacturing quality of roots. The root forms, profile forms axial accuracy, blade tips
are checked to ensure quality but there is a necessity to check whether the root
chamfers are dimensionally acceptable during fitting and if not, there should be a
device that can be used to check the same during

root fitting operation. As these chamfers are on the exit edges of bearing flanks of fir-
tree freestanding low pressure blades, these are dimensionally critical and thus care
should be taken to maintain these dimensions during manufacturing to ensure that no
uneven or unwanted concentrated stresses are generated in the bearing flank areas.
After manufacturing of fir-tree blades of different root forms, manual chamfering is
done in the root exit edges at the bearing flanks. This operation is done by engineering
files as per dimension of blade drawings during root fitting operation. Thus, there exists
a need of a device to check the low pressure steam turbine blades.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a device for checking chamfer at
exit edge root of freestanding fir-tree blades of low pressure steam turbine, which is
capable of checking dimensional accuracy of said chamfer.
Another object of the invention is to propose a device for checking chamfer at exit edge
root of freestanding fir-tree blades of low pressure steam turbine, which is able to
improve the quality by maintaining dimensional accuracy of said chamfer at exit edge
root with the help of checking device.

Yet another object of the invention is to propose a method of checking the chamfer at
exit edge root of freestanding fir-tree blades of low pressure steam turbine using the
device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig. 1(a) - Shows device for checking chamfer at exit edge root of freestanding fir-
tree low pressure steam turbine blades according to present invention.
Fig.l(b) - Shows section AA of fig.1a with root Holder (1), Stopper Plate (3) and
Screws (4) for fastening Stopper Plate (3) with Root Holder (1) vide holes
H2 & H3.
Fig.2 - Shows Root Holder (1) with threaded hole H1 and threaded holes H2
according to an embodiment of the present invention.
Fig.3(a) and 3(b) - Shows the tightening screw (2) with threaded size H4 and stopper
plate (3) with holes H3 for champing according to the present invention.
Fig.4 - Shows the fir-tree freestanding blade having chamfer at exit edge of root.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in fig.1a, a device (D) for checking chamfer at exit edge root of freestanding
fir-tree low pressure steam turbine blades comprising;
(a) Root Holder (1)
(b) Tightening Screw (2)
(c) Stopper plate (3)
(d) Screws (4)
The exit edge of the root of fir-tree blade shall be fitted in the Root Holder (1). Stopper
plate (3) shall be fastened according to the hand (left hand or right hand blade
according to steam flow direction on blade profile) with 2 number of fastening Screws
(4) vide holes H2 & H3. The stopper plate (3) will be treated as reference which
restricts the motion of the device along the root of the fir-tree blade. The device shall
be fixed from the bottom by tightening the Screw (2).
Once the setup is ready, fillers will be inserted in the chamfered areas of the root as
there will be gaps between the surfaces of device and blade bearing flanks.

As shows in fig.1a and 1b, the root holder of the device is fitted with a stopper plate,
the said plate being fixed in the holes H2, H3 by the screws (4). The stopper plate is
fixed according to hand of blade related to steam flow direction on blade profile.
After manufacturing, the exit edge of the blade root shall be inserted into the Root
Holder (1) until the blade is stopped by stopper plate (3). Now the Tightening Screw (2)
is inserted into the threaded hole H1 of Root Holder (1) and rotated to lift the blade
from bottom and thus ensuring proper tightening of blade inside Root Holder (1).
Now filler of dimension 'C' as per (chamfer dimension) is inserted in the gaps between
the gauge surfaces and upper bearing flanks at exit edges of the blade. The fillers of
certain dimension shall exactly go into the gaps and until this is achieved, the chamfer
is continued to be rectified.

WE CLAIM
1. A device for checking chamfer at exit edge root of freestanding fir-tree blades of
low pressure steam turbine, the said device comprising:
a root holder (1) having threaded holes H1 and H2;
a stopper plate (3) being fixed to the root holder (1) for stopping the
inserted exit edge of the blade in the root holder;
a plurality of fastening screws (4) for fixing the stopper plate (3) in the
treaded hole H1 and H2 of the root holder (1);
a tightening screw (2);
characterized in that the root holder (1) is disposed for receiving the exit
edge of the blade root until it is stopped by the stopper plate (3) when the
tightening screw (2) is disposed in threaded hole H1 of root holder (1) for
rotating and lifting the blade from bottom for ensuring proper tightening of blade
inside the root holder (1).
2. A method for checking the chamfer by the device claimed in claim 1, comprising;

fixing a support plate (3) with screws (4) on the root holder (1) to stop
exit edge of the root of fir-tree blade inserted in the root holder (1), the said
stopper plate (3) being fastened to root holder according to left or right hand of
blade based on steam flow direction on blade profile;
inserting a tightening screw (2) in threaded hole H1 of root holder and
rotating to lift the blade from bottom to ensure proper tightening of blade inside
root holder (1) wherein filler of kn dimension 'C' as per requirement of
chamfer is inserted into the gaps between the gauge surfaces and upper bearing
flanks at exit edges of blade and the chamfer is continued to be rectified till the
fillers of certain dimension exactly go into the gaps.

ABSTRACT

A device for checking chamfer at exit edge root of freestanding fir-tree blades of low
pressure steam turbine comprising a root holder (1) having threaded holes H1 and H2.
A stopper plate (3) is fixed on this root holder by threaded screws (4) at H1 and H3. A
tightening screw (2) is inserted in the threaded hole H1 of root holder and rotated to lift
the blade from bottom and thus ensuring proper tightening of blade inside not holder.
The support plate (3) is fastened to the root holder (1) according to hand, left or right
based on steam flow direction on blade profile. Filler of known dimension as per
required chamfer is inserted in the gaps between the gauge surfaces and upper bearing
flanks at exit edges of the blade. The filler of certain dimension is inserted into the gaps
between the gauge surfaces and upper bearing flanks at exit edges of the blade to
check if it goes exactly into the gap and until it does, the chamfer is continued to be
rectified.