The present invention relates to rigid clamping of LP Rotor (LP 2L/R) Z-
shroud blades having fins on outside periphery. The fixture is used for
holding blades during Magnetic Particle Inspection (MPI) of these blades.
More particularly the present invention relates to fixture for clamping of
LP Rotor Blades of steam turbine and a method for clamping for MPI
purpose.
Background of the invention:-
Steam turbine is a heat engine that converts thermal energy from
pressurized steam and uses it to do mechanical work on a rotating
output shaft to drive an electrical generator and hence to generate
electricity.
A supercritical steam turbine is the steam turbine designed to operate
above the critical pressure of water (i.e. above 221.5 bar). Typically
existing supercritical units operate at around 242 bar main steam
pressure and around 565°C main steam temperature and approximately
593°C reheat steam temperature. This results in fuel savings to the
extent of 5% and hence reduction in CO2 emission.
A turbine blade is an important component of steam turbine. A number
of blades like vanes are assembled around the periphery of the turbine
rotor to guide the steam flow. The energy of steam is converted to
mechanical energy through the impact (impulse) or reaction of steam
against the blades ultimately rotating the turbine shaft.

The main feature in a turbine are -
LP Rotor Blades: It is Low Pressure Turbine Rotor Blade
LP (2L/2R): LP Rotor second stage of module stage Left handed and Right
handed blades
Fins (Refer fig. 2, item 7) are important as it prevent the leakage of the
steam. Amount of steam which passes through other than designed
steam path is called leakage steam. To minimize the leakage resistance
in forms of labyrinth path is made with the help of fins. If fins get
damaged, then the leakage steam will increase and efficiency of turbine
will be reduced and hence coal consumption will increase. Previously
there were blades without integrated fins on the shroud. So, there was no
requirement of special fixture at machine to hold the blade in order to
protect the fins. The blades are fixed in the horizontal position between
root and shroud tip for Magnetic Particle Inspection purpose. MPI is a
non-destructive testing process for detecting surface and subsurface
discontinuities in ferromagnetic materials such as iron, nickel, cobalt
and some of their alloys.
Steam turbine blade and fins are a very precise and critical components.
There are integrated fins (item 7) at the shroud (item 8) of blade (Refer
fig. 2). During fixing of blade at MPI machine, the fins may get damaged.
To protect the integrated fins, a fixture for clamping is required.
Fins are working as sealing strips, which prevents the leakage of steam.
If fins will be damaged then steam leakage will increase and hence the
efficiency of steam turbine as well as of the power plant will be reduced.
If fins get damaged beyond limits, then blades will be rejected. It will
increase the cost of manufacturing of the turbine as well as the
production time of Steam Turbine will increase. Delay in manufacturing
will delay the erection and commissioning of power plant which will
further affect adversely the availability of electricity.

Object of the invention:-
The object of the present invention is to provide a clamping fixture for
Magnetic Particle Inspection of LP rotor blades of Steam Turbine which
prevents the damages of shroud fins.
Another object of the invention is to provide a clamping fixture for
Magnetic Particle Inspection of LP rotor blades of Steam Turbine which
reduces the rework time of blades, caused due to integrated fin damages
during Magnetic Particle inspection.
A further object of the invention is to provide a clamping fixture for
Magnetic Particle Inspection of LP rotor blades of Steam Turbine that
ensures the manufacture of the blade without any rework on shroud
area to maintain the quality of blade.
Brief description of drawing:-
Fig. 1 shows the exploded view of the fixture clamping unit
Fig. 2 shows steam turbine blade (LP 2L/R) with integrated fins.
Fig. 3 shows the assembly of blade with fixture on MPI machine.
Detailed description of a preferred embodiment of the invention:-
In the present invention, the LP2L/R blades (B, Refer fig. 2) with
integrated fin (7) at shroud (8). Hence, in order to protect the integrated
shroud fins (7) during MPI process or any other process in which there

are chances that the fins may collide/butt with other parts and may get
damaged, a clamping fixture (A) is developed. The fixture is tightened on
tail machine plate (5) by four alien bolts (4). The integrated fins (7) fall
into the slotted groove of U- shape frame (10) of fixture (A) and thus
avoiding direct contact with any machine parts.
Accordingly, this provides a single setting clamping fixture (A) for MPI of
blades:-
Reference Part description
01 ---- Inclined Surface of U shaped frame (10) in one limb
02 ---- Plurality of threaded holes on the U-frame
03 ---- Plurality of hole in machine plate (5)
4 ---- Allen Bolt
5 ---- Machine Plate
06 ---- Vertical inner surface of U-frame (10) in the other
limb
07 ---- Fins of a Steam Turbine Blade
03 ---- Shroud part of a Steam Turbine Blade
09 ---- Root part of Steam Turbine Blade
10 ---- U-shaped frame .
11 ---- bottom surface of U frame

Fig. 3 shows the blade (B) which rest on the fixture (A). The fixture (A) is
tightened on tail machine plate using connection between threaded holes
(2) of the device and holes (3) in machine plate (5) and alien Bolt (4).
Machine plate (5) works as washer for the connection between threaded
holes (2) of device and alien Bolt (4)
During MPI process, the blade (B) will butt with the surfaces of U-frame
(10) in such a way that surface (1) and surface (6) have same angles as
that of the corresponding surfaces of the shroud (8) of the blade (B).
Since the surface (1) and surface (6) have same angles as that of the
corresponding surfaces of the shroud (8), the fins (7) will be within the
slot and thereby protected.
The blade (B) is clamped on the machine in horizontal position with the
help of fixture (A) and MPI is done without damaging integrated fins at
shroud.
In this type of clamping if the device will not be used during Magnetic
Particle Testing of Blades with integrated fins at shroud, then there are
chances that fins may get damaged. Fins are working as sealing strips,
which prevents the leakage of steam. If fins will be damaged then steam
leakage will be increased and hence the efficiency of steam turbine will
be reduced. OR If fins get damaged much then Blade will be rejected.
Because, the fins are integrated to shroud and cant be reworked.

We claim:-
1. A fixture (A) for clamping of LP Rotor blades of steam turbine
comprising:
a U-shaped frame (10) having plurality of limbs with an inclined top
surface (1) in one of its limb and a surface (6) vertical to the base of U-
frame (10),
the U frame (10) being shaped in a manner that the inner space
accommodate the fins,
the U-frame (10) having four holes (02) on the surface (11) for fixing the
frame (10) with the machine plate (5) through the corresponding
matching holes (3) with alien bolts characterized in that when the blade
(5) is loaded on the machine with the fixture, the surfaces (1, 6) of the U-
frame (10) butt with the respective matching surfaces of the blade ( B) at
the shroud end (8) such that the fins (7) fit into the vacant space of U-
frame (10) without getting damaged .
2. The fixture as claimed in claim 1 where all the parts are made of
copper material.
3. A method of clamping the steam turbine blade (B) in a fixture (A)
during magnetic particle inspection comprising:
applying the switch/lever to release the pneumatic pressure from the
head of the MPI machine;
holding the turbine blade (B) with hand in between MPI machine head
and tail with fixture (A);
aligning the MPI machine tail plate with fixture (A), so that the blade
integrated fins (7) fall into the slotted groove of U-frame (10) of fixture (A);
releasing the switch/lever to apply the pneumatic pressure on the

turbine blade (B) to hold the turbine blade between MPI m/c head and
tail without damaging the fins;
performing the magnetic particle inspection on the machine.