FIELD OF INVENTION
The present invention relates to an improved method of rotor insertion and
withdrawal from generators with tapered skid plate and skid shoe made of high
strength composite materials.
BACKGROUND OF THE INVENTION
In general practice, steel slide plate, sliding shoes, slide pedestal and slide
grease are used to perform rotor insertion/withdrawal procedure. The present invention
intends to improvise the efficiency and easy handling method compared to the
conventional rotor insertion/withdrawal method by using high strength composite
materials. So far rotor insertion and withdrawal was being carried out with heavy steel
equipment. But availability of heavy steel equipment is limited in India. Hence there is a
lot of dependency on overseas suppliers. The entire process of rotor
insertion/withdrawal is cumbersome due to the heavy equipment involved.
The present invention relates to an improved method of rotor insertion and
withdrawal by replacing the steel equipment with equipment made of composite
material.
Increasing use of composite materials in many fields of engineering has been
observed in the past few decades. The properties of fiber reinforced composites like

high strength to weight ratio, high stiffness to weight ratio, flexibility in design, ease of
fabrication and economical as compared to metals, make it an excellent choice for
various range of products. Some of the high strength composite materials (with earlier
mentioned superior properties) like S-glass, Kevlar, Carbon fibre etc are available which
are used for high strength applications.
Using the tapered skid plate and ball bearing enabled skid shoe made of
composite materials, additional sliding effect is achieved. Usage of Slide grease, heavy
Crane lifters etc in the conventional process is reduced in the improved method. The
present method is not only efficient over the prior Art but also highly cost effective.
PRIOR ART
Patent No. US 4447739 A, titled “Rotor withdrawal arrangement for bulb
generators”
Abstract:
The present invention involves invention of apparatus for withdrawing the rotor
from the stator in a bulb-type generator makes the rotor and the inner portion of the
stator accessible for repair or maintenance without having to dissemble the housing and
stator. A pair of detachable beams are placed in the housing when the rotor is
stationary so they extend through holes provided in the rotor above the shaft on which
the rotor runs. The beams are conveniently mounted to the upper stay tower structure

at their downstream end, and to the housing at their upstream end. An additional
support member may be used between the beams and the bottom of the housing at the
upstream end of the beams. Shoes which slid ably engage the beam are placed
between the beam and the rotor to support the rotor. Preferably the shoes include a
hydraulically operated piston which can be extended to ensure positive engagement
with the beam. The rotor has an inner ring which is bolted to a driving disc on the
shaft. The bolts are removed and a hydraulic jack in used to slide the rotor outwards
along the beams clear of the stator.
Patent No. US 20050150095 A1, titled “Methods of generator rotor removal
in a combined-cycle stag application”
Abstract:
The present invention relates to a method of removing the generator from an
aligned gas turbine-generator-steam turbine configuration for maintenance and
returning the generator to useful service in the aligned gas turbine-generator-steam
turbine configuration. Support feet of a generator are mounted on foundation columns
spaced laterally one from the other, with one column having a block in a recess for
receiving the feet on one side of the generator. Guides on a radius and supported by
the generator foundation extend through notches on the underside of the block. To
locate an end of the generator displaced horizontally from the turbines, the generator is
unloaded from the foundation and the block is removed. The generator is then loaded

onto the guides and pivoted about a vertical axis to locate at least one end out of
alignment with the axis of the turbines enabling removal of the generator rotor in an
axial direction. By employing two blocks set in recesses in the opposite columns and
sets of tracks which extend into the notches, the generator can be rotated about a
vertical axis through its center to locate the generator rotor in axially non-interfering
positions with the adjacent turbines.
Patent No. WO 2014193043 A1, titled “Lifting apparatus and method of
withdrawing rotor shaft of generator in combined power generation plant
using same”
Abstract:
This is an invention relating to a method of withdrawing a rotor shaft of a
generator in a combined power generation plant using a lifting apparatus. The disclosed
method of withdrawing a rotor shaft of a generator in a combined power generation
plant using a lifting apparatus, wherein a gas turbine including an upper casing
assembly and a lower casing assembly, a generator and a steam turbine are arranged
in the combined power generation plant, comprising the steps of: separating the upper
casing assembly from the lower casing assembly, thereby forming a movable space part
in the gas turbine; separating the rotor shaft of the generator that is flange coupled to
a shaft of the gas turbine and to a shaft of the steam turbine; installing a lifting
apparatus in the generator and lifting the generator using the lifting apparatus; hanging

the lifting apparatus from an end portion of the rotor shaft exposed in the direction of
the gas turbine in the generator by using a lifting member connected to an overhead
crane; moving the overhead crane and pulling the rotor shaft in the direction of the
movable space part by means of the lifting member, thereby withdrawing a portion of
the rotor shaft; and hanging a central portion of the rotor shaft from the lifting member
and withdrawing, lifting and moving the entire rotor shaft.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved method of
rotor insertion and withdrawal from generators with tapered skid plate and skid shoe
made of high strength composite materials, which is capable of providing an efficient
rotor insertion/withdrawal arrangement.
Another object of the invention is to propose an improved method of rotor
insertion and withdrawal from generators with tapered skid plate and skid shoe made of
high strength composite materials, which is able to curb the dependency on foreign
suppliers.
A further object of the invention is to propose an improved method of rotor
insertion and withdrawal from generators with tapered skid plate and skid shoe made of
high strength composite materials, which makes the process highly economical.

SUMMARY OF THE INVENTION
The present invention deals with the installation of a turbo generator operated in
a power plant or industrial establishment and especially on improvising the performance
through modifications to the existing installation procedures.
Due to the complex nature of installation of the machine, only skilled personnel
is authorized to perform any disassembly or assembly. In the Prior Arts of rotor
withdrawal, the rotor is disengaged on the turbine end. The fan blades are removed if
the diameter of fan is greater than the inner diameter of the rotor retaining ring or if
there is a danger that the fan blades will interfere with the housing. The slide plate is
inserted carefully by preventing any damage to the rotor and stator. A thin film of slide
grease is applied on the top side of the slide plate and wrapped in sheets. The slide
plate, covered in foil, is slid in through the generator gap between rotor and stator,
above the exciter end bearings. It is placed centrally underneath the rotor by guiding it
on both sides. After this, the foil between the rotor and the slide plate is removed. The
rotor is lifted with the crane until the intermediate frame can move freely and can be
pulled out from the side. The sliding shoe is inserted between centrally aligned slide
plate and the rotor. The rotor can be lowered until its bearing is on the sliding shoe.
Finally, the rotor will be pulled out of the stator by exerting an axial pull while
continuously guiding the crane. It is ensured that the rotor and stator components do
not come into contact with each other while the rotor is being removed.

In the present invention, a tapered skid plate and a ball bearing enabled skid
shoe made of composite materials are introduced which provides great advantage.
Increasing use of composite materials in many fields of engineering has been observed
in the past few decades. The properties of fibre reinforced composites like high strength
to weight ratio, high stiffness to weight ratio, flexibility in design, ease of fabrication
and economical as compared to metals, make it an excellent choice for various range of
products. The constituents of the composite materials can be judiciously chosen so that
one or more of the advantages like high specific strength, specific modulus and material
damping capacity as desired could be obtained. The present invention aims to exploit
the advantage of composite materials to improvise the efficiency of conventional rotor
insertion/withdrawal method.
Extreme Precautions are taken throughout the installation process of generator.
Rotor insertion/withdrawal should be performed with utmost safe methods such that it
should not cause any damage to either the rotor or the stator during the process of
rotor insertion/withdrawal, which otherwise may lead to reduction in efficiency of the
machine. The present invention aims to exploit the advantage of composite materials to
improvise the efficiency of conventional rotor insertion/withdrawal method. Fabrication
of a tapered skid plate and ball bearing enabled skid shoe, using high strength
composite materials give rise to an efficient rotor insertion/withdrawal arrangement.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 Shows cross sectional view of a typical generator with rotor, stator, skid
plate and skid shoe.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Necessary precaution is taken during insertion/withdrawal of rotor from the
machine during machine installation procedure to avoid any unnecessary deflection,
vibrations etc. These may lead to decrease in efficiency and poor performance levels of
the machine. In the long runs, this leads to damage of the machine. Hence, rotor
insertion/withdrawal should be performed with utmost safe methods such that it should
not cause any damage to either the rotor or the stator during the process of rotor
insertion/withdrawal.
Fig. 1 shows cross sectional view of a typical generator pertaining to the present
invention. The tapered skid plate ‘3’ is made up of high strength composite materials
such as Kevlar, S-Glass etc. Tapering is given to provide additional sliding effect during
rotor withdrawal procedure. The tapered skid plate ‘3’ proposed for efficient rotor
insertion/withdrawal is placed centrally underneath the rotor ‘4’. The skid plate ‘3’ is
inserted carefully by preventing any damage to the rotor ‘4’ and stator ‘2’. The ball
bearing enabled skid shoe ‘1’ is a combination of high strength composite material as
well as ball bearings, which provides smooth gliding movement. The ball bearing
enabled skid shoe ‘1’ is inserted between centrally aligned skid plate ‘3’ and the rotor
‘4’.

WE CLAIM
1. An improved method of rotor withdrawal from generators with tapered skid plate
and skid shoe made of high strength composite materials, the said method comprising
the steps of;
disengaging the rotor in the turbine end;
removing fan blades if the diameter of fan is greater than the inner diameter of
the rotor retaining ring;
inserting a slide plate carefully by preventing any damage to the rotor and
stator;
applying a thin film of slide grease on top of the sliding plate and wrapped in
sheets;
sliding in the sliding plate through a generator gap between rotor and stator
above the exciter end bearings;
placing the sliding plate centrally underneath the rotor by guiding it on both
sides;
removing the foil between the rotor and side plate;
characterized in that,
a tapered skid plate (3) provided for additional sliding effect during rotor
withdrawal is placed centrally underneath the rotor (4) and inserted carefully for
preventing any damage to the rotor (4) and stator (2), wherein a ball bearing enabled

skid shoe (1) is disposed between centrally aligned skid plate (3) and the rotor (4) to
provide smooth gliding movement of the rotor when the rotor is finally pulled out of the
stator by exerting an axial pull with the help of a crane being guided continuously.
2. The method as claimed in claim 1, wherein tapered skid plate is made of high
strength composite materials.
3. The method as claimed in claim 1, wherein the ball bearing enabled skid shoe is
made of high strength composite materials.