FIELD OF THE INVENTION
The present invention relates to an improved device for supporting and holding
in a process of TEG-welding of leading and trailing edges of pressure and suction
side surfaces of Banana type hollow guide blades of Steam Turbine LP Modules.
BACKGROUND OF THE INVENTION
Normally the Steam or Gas Turbine Blades are designed with prismatic blade
roots, such as T-root, Fir-Tree root, Fork Root etc, but in case of Banana type
hollow guide blades there is no prismatic root available to hold the blade. Hence
the devices available are not suitable to hold the blades during TIG welding of
the leading and trailing edges of the banana type hollow guide blades.
Banana type hollow guide blade is a stationary blade of Low Pressure (LP)
module of the Steam Turbines of power generating equipment. This guide blade
has typically designed geometrical aerofiles profiles with bent stacking axis.
Moreover these blades do not have any prismatic roots, such as T-Root, Fir Tree,
Fork type etc...., which are normally found in all the other types of ST/GT blades.
During the manufacturing process of Banana type hollow guide blades, bent
sheet metal skins of the pressure and suction side surfaces of the blades are to
be tightly held in position for TiG welding of the leading and trailing edges of the
blade. And also the holding area has to be distributed over the entire blade
aerofoil surface to minimise the distortions formed due to heat generated at the
time of welding. The Holding positions and Fingers should not hinder the TiG
welding process to be carried out at both edges of the blade.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved device for
supporting and holding in a process of TIG-welding of leading and trailing edges
of pressure and suction side surfaces of Banana type hollow guide blades of
Steam Turbine LP Modules.
Another object of the invention is to propose an improved device for supporting
and holding in a process of TIG-welding of leading and trailing edges of pressure
and suction side surfaces of Banana type hollow guide blades of Steam Turbine
LP Modules, which enables maintenance of dimensional deviation of the blades
within permissible limit.
A further object of the invention is to propose an improved device for supporting
and holding in a process of TTG-welding of leading and trailing edges of pressure
and suction side surfaces of Banana type hollow guide blades of Steam Turbine
LP Modules, which allows holding of the sheet metal edges in right position to
eliminate distortion of the blade due to heat generated during welding.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved device for supporting and holding in a
process of TIG-welding of leading and trailing edges of pressure and suction side
surfaces of Banana type hollow guide blades of Steam Turbine LP Modules. The
invention allows carrying-out a stitch welding process without any distortion or
dimensional deviations.
According to the invention, the twisted aerofoil Pressure and Suction Side
surfaces of the Banana type hollow guide Blade is mounted with the help of a
plurality of Finger inserts. The Pressure and Suction side surface sheet metal of
the Banana Hollow Guide Blade are clamped by fastening the top and bottom
aerofoil supports.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a banana type hollow guide blade supported and held on the
device of the invention in an open position for welding of the leading
and trailing edges of the blade.
Figure 2 - shows the inventive device in a closed-state.
DETAIL DESCRIPTION OF THE INVENTION
As shown in Figure 1 and Figure 2, a banana type hollow guide blade (1), which
is to be held in position, comprises suction (2) and pressure (3) aerofoil surfaces
in the form of bent sheet metal parts. These sheet metal parts are to be TiG
weld together at Leading (4) and Trailing (5) edges to form the final blade
shape. The inventive device comprises a Base Plate (6) to accommodate a
support Plate (7), a plurality of leading Edge Stoppers (8), a multiple Suction
Surface Support Fingers (9), a Conical End Stopper (10), a top Plate (11), a
plurality of Pressure Surface Support Fingers (12), a hinge Pin (13) and a
Clamping Screw (14).
The Support Plate (7), which is fastened to the Base Plate (6), holds the Top
Plate (11) with the help of Hinge Pin (13) and allows the Top Plate to be opened
and closed at the time of welding operation. The Leading Edge Stoppers (8),
which are fastened to the Base Plate (6) locate the Pressure and Suction surface
skins of the blade in position by butting at the leading edge. However, after
firmly holding the blade, these Stoppers (8) are removed to allow welding of
leading edge of the blade. The Suction Surface Support Fingers (9), which are
fixed on to the Base Plate (16), support the Suction Side Aerofoil Sheet metal
Surface (2) to be held in position by matching to the part of the Blade aerofoil
surface (3,4), at three places, to cover the entire Blade length. The Conical End
Stopper (10), which is fixed to the Boss Plate, is butted against the Blade Sheet
metal skins, at the inner edges of the Blade, to reference and locate the blade in
axial direction. Pressure Surface Support Fingers (12), which are fixed on to the
Top Plate (11), support the Pressure Side Aerofoil Sheet metal Surface (3) to be
held in position by matching to the part of the Blade aerofoil surfaces, at three
places, to cover the entire Blade length. Finally, the Top Plate (11) along with
the Pressure Surface Support Fingers (12) are screwed to the Conical End
Stopper (10) for holding the Blade from all directions to avoid welding
distortions.
Based on the above functional requirements the Welding device has been
manufactured to TiG weld the bent sheet metal pressure and suction side surface
segments of the blade aerofoil profiles, at two open areas i.e., Leading and
Trailing Edges, formed by inlet and outlet edges of the top and bottom skins, the
device holding in position without any obstructions and distortions. This results in
manufacturing of a single Banana type Hollow Guide Blade of Steam Turbine LP
Module. This device also ensures a final blade within the specified dimensional
tolerance requirements.
WE CLAIM
1. An improved device for supporting and holding in a process of TIG-
welding of leading and trailing edges of pressure and suction side surfaces
of Banana type hollow guide blades of Steam Turbine LP Modules, the
guide blade (1) comprises at least one each suction aerofoil surface (2)
and pressure aerofoil surface (3) to be welded at leading edge (4) and
trailing edge (5) to form the complete blade, the device comprising:-
- a base plate (6);
- a support plate (7) vertically fixed at a first end of the base plate (6) to
hold a top plate (11) via a hinge pin (13), the top plate (11) being
openable-closable during the welding operation;
- a plurality of leading edge stoppers (8) vertically and equidistantly
disposed along the longitudinal surface of the base plate (6) which initially
locate the pressure and suction surfaces (3,4) of the guide blade (1) and
removed during welding;
- a plurality of suction surface support fingers (9) vertically attached to the
base plate (6) and parallely positioned in respect of said stoppers (8) to
matchingly hold the pressure and suction surfaces (4,3) of the guide blade
(6);
- a conical end stopper (10) disposed vertically at a second end of the base
plate (6) supporting the inner edges of the blade surfaces to reference
and locate the blade (6) in axial direction;
- a plurality of pressure surface support fingers (12) disposed on the inner
side of the top plate (11) to support the pressure side aerofoil sheet metal
surface (4) along the axial length of the blade (6); and
- the top plate alongwith the pressure support fingers (11,12) screwably
attached to the conical end stopper (10) for holding the blade (06) such
that welding distortions are eliminated.
2. An improved device for supporting and holding in a process of TIG-
welding of leading and trailing edges of pressure and suction side surfaces
of Banana type hollow guide blades of Steam Turbine LP Modules, as
substantially described and illustrated herein with reference to the
accompanying drawings.

ABSTRACT

The invention relates to an improved device for supporting and holding in a
process of TIG-welding of leading and trailing edges of pressure and suction side
surfaces of Banana type hollow guide blades of Steam Turbine LP Modules, the
guide blade (1) comprises at least one each suction aerofoil surface (2) and
pressure aerofoil surface (3) to be welded at leading edge (4) and trailing edge
(5) to form the complete blade, the device comprising a base plate (6); a
support plate (7) vertically fixed at a first end of the base plate (6) to hold a top
plate (11) via a hinge pin (13), the top plate (11) being openable-closable during
the welding operation; a plurality of leading edge stoppers (8) vertically and
equidistantly disposed along the longitudinal surface of the base plate (6) which
initially locate the pressure and suction surfaces (3,4) of the guide blade (1) and
removed during welding; a plurality of suction surface support fingers (9)
vertically attached to the base plate (6) and parallely positioned in respect of
said stoppers (8) to matchingly hold the pressure and suction surfaces (4,3) of
the guide blade (6); a conical end stopper (10) disposed vertically at a second
end of the base plate (6) supporting the inner edges of the blade surfaces to
reference and locate the blade (6) in axial direction; a plurality of pressure
surface support fingers (12) disposed on the inner side of the top plate (11) to
support the pressure side aerofoil sheet metal surface (4) along the axial length
of the blade (6); and the top plate alongwith the pressure support fingers
(11,12) screwably attached to the conical end stopper (10) for holding the blade
(06) such that welding distortions are eliminated.