TITLE: AN APPARATUS FOR INTEGRATION IN OPERATION OF TWO
IMPREGNATION TANKS
FIELD OF INVENTION:
This present invention is related to an apparatus for integration is the operation of two
impregnation tank used in Vacuum Preserve impregnation process of stator bars for
turbo generators of 210MW, 500MW, 600MW, 700MW & 800MW etc. rating. More
particularly this invention relates to, a system developed through which, consumption
of epoxy resin-hardener, electrical energy, man power & other resources are reduced
during Vacuum Preserve impregnation (VPI) process and more productivity is achieved
through integral operation of two identical machines.
BACK GROUND AND PRIOR ART OF INVENTION:
The insulation of high voltage rotating machines usually consists of mica, a carrier
material and binder Resin-hardener mix. Mica tape is wrapped around the surface of
the conductor to form the insulation wall. When the stator bar is fully covered by mica
tape, any space between the mica tapes is filled with Resin-hardener mix in order to
reduce air insulation, with the process, called Vacuum Preserve impregnation (VPI)
process.
Vaccum Preserve impregnation (VPI) process for void free insulation of stator bars in
Turbo generator is done through VPI process as follow,
Heating of Stator Bars at temperature of 70 ± 10°C for around 10 hour to extract all
possible gaseous impurities, moisture etc.
Simultaneously, Vaccum is created up to 0.2 mbar in order to extract air to make the
easy penetration of resin-hardener mixture in layers of mica tape insulation.
Resin-Hardener mixture is heated at 70 + 3°C temperature before dipping the job in it.
Stator bars are dipped in Resin so that Resin-Hardener mix penetrates the mica tape
layers.
Five bar pressure of Nitrogen gas in applied to make better penetration.
Above said process is carried out in a machine called Impregnation tank (1). Stator
bard are placed in Impregnation tray (2). After completion of VPI process, stator bars
are taken out & pressed on baking wagon & then cured in a oven for about 10 hours
at 140°C. This process is shown in lay out diagram in Fig 1.

At present, in BHEL Haridwar Unit, there are two identical impregnation tanks, which
impregnation six stator bars in each & provided to dedicated wagons facility for .
pressing. After pressing, both wagon are send to dedicated ovens. These two separate
machines are situated in separate work center & operates independently. It is being
showing in Fig 1.
Since the impregnation tank consist heaters, vacuum pump system, numerous valves,
motors, pumps & controllers, any fault or mal functioning of any of these,
impregnation process can not be done. So this machine is very dedicate towards
maintenance. Whenever, there is any fault or maintenance in any impregnation tank,
following problems came,
1- Output to next stage is discontinued & respective wagon & oven remain unloaded
as shown in Fig 2.
2- Work man remains idle in this work area leads to loss in organization.
3- Production schedule is disturbed.
To overcome the above said problems face during production in VPI process, the
present invention provides an apparatus that integrate operation of both impregnation
tanks, so that output of both tank (6+6=12 stator bars) can be impregnated in single
impregnation tank keeping other facilities fully loaded. This is named here as Integral
operation'.
OBJECT OF THE INVENTION:
It is therefore, an object of the present invention is to utilized single Impregnation
Tank for two or more auxiliary facilities
Another object of the present invention is to reduce consumption of resin-hardener,
electricity, compressed nitrogen gas etc.
Another object of the present invention is to save idle man power of operators during
maintenance.
Ye another object of the present invention is to provide immunity against breakdown
in production line.

SUMMARY OF THE INVENTION;
According to this invention, there is provided an apparatus for integration in operation
of two Impregnation Tanks, the apparatus comprising of: a plurality of stator bars; an
impregnation tray; and a hanger; wherein first six stator bars are placed in the
impregnation tray, and the second six stator bars are placed a second tier supported
by a hanger.
BRIEF DESCIPTION OF ACCOMPANYING DRAWINGS:
Fig 1 shows the layout diagram of two impregnation tanks operating independently.
Fig 2 shows lay out diagram for the non-operation of one impregnation tank due to
maintenance work & related facilities at next stages are idle.
Fig 3 shows the cross sectional view of Impregnation tank (1) with vacuum pump
system (4). Tray (2) impregnation tank has six stator bars (3).
Fig 4 shows the hanger (4) for supporting next six stator bars.
Fig 5 shows the 12 stator bars in impregnation tank. Next six stator bars (5) are
supported by hangers (4).
Fig 6 shows the lay out diagram of integral operation of impregnation tank.
DETAILED DESCRIPTION OF THE INVENTION:
The present invention provides an apparatus that is. developed through integral
operation of two similar impregnation tanks, in which total output remain intact even
if one impregnation tank is in maintenance. Thus this invention provides immunity
against breakdown in machines & reduction in resources consumption.
To integral operation of both impregnation tanks, total output of 12 bars (i.e. 6 bars
form each tank) are to be taken out from single tank.
As per present practice, impregnation tray (2) is designed for only placing six stator
bars (3). So here for next six stator bars (5), a arrangement has to be developed.
Following options are available,
1- Development of new impregnation tray for accompanying 12 bars at a time.
2- Development of new supporting arrangement in existing tray.

Instead of new tray, new supports in form of hanger (4) is designed & developed as
shown in fig -4 & can be used to support next sic\x stator bars (5) as in fig. -5
Design & Dimensions of hangers may vary according to the dimension of stator bars,
tray width, height etc. With this integral operation, following additional benefits are
achieved in form of resources saved from non-operation impregnation tank,
1- In case of breakdown/ maintenance in one impregnation tank, the output of tank
(in maintenance) can be obtained from another tank & thus, input to the next work
center can be delivered. SO, productivity remains intact & immunity develops in
production line against breakdowns / maintenance work as in fig 6.
2- Electricity consumed in operation of impregnation tank 85 its vacuum pump system,
heating of resin-hardener etc. is saved in non-operational impregnation tank.
3- After each impregnation cycle, an amount of resin hardener remains on the surface
of tray due to spacing bodies, rubber supports for stator bars, & do not transferred
back to storage tank. This residual Resin-Hardener is wiped out which is approx. 25-
30 Kg. 8s hence gone waste. In integral operation, this amount is saved for non-
operational impregnation tank.
4- In integral operation, heating-cooling cycle of stored Resin-Hardener mix for non
operative impregnation tank is reduced, so due to less exposure to heat, its aging i.e.
rate of viscosity rise is reduced.
5- Similarly, compressed nitrogen gas is saved for non operative impregnation tank.
After impregnation of 12 stator bars, six stator bars (5) are sent to another work center
loc.ated in non-operative impregnation tank area by trolley. All stator bars with this
developed system were offered to quality assurance for high voltage endurance test 8s
tan delta test. It has been found that measured values are in specified limit 8s also
comparable with values measured for stator bars impregnated in a lot if six nos.
During this operation, few precautions are to be taken,
1- While placing if bars on support, care has to be taken about prevention of damaging
of inclusion layers.
2- Overhang of Stator bars should not collide with each other.
3- After pacing of 12 bars in tray, Level of Resin-Hardener must be maintained in tray
according to highest point of insulating portion.

4- During transportation of six bars to another area, impregnated bars must be well
covered so that excess resin-hardener do not fell on floor during transportation of
impregnated bars.
In case of non operation of one impregnation tank, to deliver its output in addition
with output of another impregnation tank, 12 stator bars has to be accommodate in a
impregnation tray (2), first six stator bars (3) are placed as usual. Another six stator
bars (5) are placed on second tier supported by a hanger (4). This hanger (4) is
designed to support six stator bars (5) so that VPI process is carried out without
affecting impregnability of resin-hardener mix. i.e. quality of VPI process remain intact
(fig.5). Size, dimension of hangers are largely depends on six of stator bars (5), tray (2)
etc. these hangers (4) are placed in 4-5 nos. along the length of stator bars (5). Since
the height of stator bars (5) us higher that the height if stator bars (3), so the level of
Resin-Hardener is kept accordingly high to ensure complete dipping of stator bars (5).
Once the impregnation tank (1) complete integral operation i.e. produces 12 stator
bars, six stator bars (5) are sent to work area of non operational impregnation tank for
feeding inputs to wagon as in fig. -6.
Advantages of the integral operation of two impregnation tanks
1. Operational integration between two identical Impregnation plants installed in same
works.
2. Development of a hanger (4) for supporting stator bars (5) in impregnation tray (2).
3. Impregnation of 12 stator bars at a time for feeding two different wagons.
4. Saving of Resin-Hardener (apprpx. 25-30 Kg.) remains residue after each
impregnation cycle.
5. Enhancing stored life of Resin-hardener mix due of reduction in heating cycles &
hence reduction in aging effect.
6. Immunity at impregnation process area in production line against breakdowns.
Since breakdown in two similar machines rarely occurred simultaneously.
7. Man-hour saving of operators for operation of second impregnation tank.
8. Idle man-hour saving during maintenance of one impregnation through containing
inputs from another impregnation tank.

9. Saving of electrical energy due to non operating impregnation tank.
10. No deviation in quality of impregnated stator bars.
11. Process remains in limit of statistical quality control.
12. More productivity due to reduction in consumption of required inputs.
13. Cost cutting in VPI process of 210MW, 500MW, 600MW, 700MW, 800MW etc
stator bars.

WE CLAIM:
1. An apparatus for integration in operation of two Impregnation Tanks, the
apparatus comprising of
a plurality of first stator bars (3);
a plurality of second stator bars (5)
an impregnation tray (2); and
a hanger (4);
wherein the first six stator bars (3) are placed in the impregnation tray (2), and
the second six stator bars (5) are placed on a second tier supported by a hanger
(4).
2. The apparatus as claimed in claim 1, wherein the hanger (4) is designed to
support six stator bars (5) so that Vacuum Preserve impregnation (VPI) process
is carried out without affecting impregnability of resin-hardener mix.
3. The apparatus as claimed in claim 1, wherein the hangers (4) are placed in 4-5
nos. along the length of stator bars (5).
4. The apparatus as claimed in claim 1, wherein the level of Resin-Hardener is
kept accordingly high to ensure complete dipping of stator bars (5).