FIELD OF INVENTION:
TG (Turbo Generator) rotors and exciter rotors are two main components of turbo
generators. In brushless variant of TG contact between the exciter and TG rotor has to
be made through contact pins. For this purpose axial holes are drilled in both the rotors
to accommodate the contact pins. The pins are silver coated at the outer surface. The
holes in both the TG and exciter rotors are silver coated in-situ, to ensure good electrical
conductivity between exciter rotor and the field windings, as the field current is of the
order of 4000 A. In case of TG, 210 MW the field current is lower and hence field lead
core bars are made of steel instead of copper which is coated with a layer of copper and
then with a layer of silver. The present invention generally relates to electroplating of the
contact pins, axial pin hole in the field lead core bars which connect exciter rotor output
to the field winding at the TG rotor. The old method of electroplating experienced several
problems which resulted in loss of production time and added heavily to the production
cost. The present invention specifically relates to a solution of overcoming the limitation
of prior art by designing an electroplating machine exclusively for this purpose.
BACKGROUND OF THE INVENTION:
For Electroplating of axial pin holes in Field lead core bar, the following steps are
involved:
1. Cleaning of holes with Tri-chloro-ethylene
2. Sealing of chamber for electroplating to avoid liquid entry to the insulation area
3. Degreasing of hole surface with Caustic Soda solution
4. Removal of degreasing solution with compressed air
5. Rinsing with water and cleaning

6. Copper coating with Copper Cyanide solution (in case of Steel, Field Lead core
bar)
7. Removal of Copper cyanide with compressed air
8. Rinsing with water and cleaning
9. Striking silver in cyanide solution
10. Removal of cyanide solution with compressed air
11. Main Silver Plating (in cyanide solution) in the holes for about 45 minutes to
achieve desired coating of silver i.e. 10 to 15 microns.
As the silver plating is required to a thickness of 10-15 microns and the base metal for
500 MW TG core bar is copper 99.99% and 210 MW TG is steel, an attempt was made to
design and fabricate the electroplating device to electroplate copper and silver on axial
holes of the dummy/model pieces before coating on the actual components using
conventional cyanide baths. This machine was not properly functioning for desired recycle
of chemicals containing cyanide solution.
After complete pre-heating and finishing cycle as per the above method, the solenoid
valves of electroplating machine were observed to be frequently jammed. Machine was
under breakdown as solutions were unable to be discharged back to their respective
tanks. In some cases, the solutions were discharged into the wrong tanks causing
solution contamination.
The solution cannot be disposed openly because it is hazardous to health and also
pollutes the environment. The solution was tested by Pollution Control Board and after
suitable disposal norms it was liable to be disposed off.

Maintenance people were reluctant to perform the maintenance works due to the
potassium cyanide residue remaining in the machine i.e. the residual solution was not
properly discharged.
Solenoid valve had to be opened and repaired by the machine operator. Consequent
upon the repairing works, it was very difficult to identify the jammed solenoid valves.
There are 4 buckets containing 10. L of caustic soda solution, Copper cyanide solution,
Striking silver cyanide solution and main silver cyanide solution respectively on many
occasions. The solution was manually pumped into the job due to urgency.
During charging of pump from one bucket to another, a lot of time was wasted leading to
the oxidation of intermediate layer and subsequent failure of the succeeding layer. This
resulted in rework in about 50% of the jobs.
The residual cyanide solution in the machine was recycled and collected in the reservoir
with the help of compressed air. And this caused all the solenoid valves to remain open
resulting in intermixing of chemicals, and thereby jamming of solenoid valve. This was
rendering the entire solution useless (about 50L) which caused a lot of material wastage.
SUMMARY OF THE INVENTION:
The electroplatating machines of the present invention have four tanks. The tanks
contain degreasing solution, silver striking solution and main silver solution.

Also there is a circulating pump connected with a timer and a set of valves. Degreasing
tank and copper solution tank are fitted with heaters to raise the temperature of the
solution to 40°C. At first degreasing operation is carried out by switching on the pump for
circulation of degreasing solution for the degreasing tank. After degreasing operation is
over compressed air charged to drain out all the trapped degreasing solution in the
system. Then traces of degreasing solution are washed by clear water. Compressed air is
again supplied to dry out droplet of water. Then silver striking and main silver plating
operations done by switching D.C. current to the copper or silver anodes fitted in the
adopter for electroplating.
ACCOMPAYING DRAWINGS:
Figure 1: Schematic Fluid Flow Diagram of Mobile Metallising Equipment:-
A- Degreasing Tank SS
B- Copper Tank SS
C- Striking Silver Tank SS
D- Main Silver Tank SS
E- Magnetic Chemical Pump with Timer
F- Adopter
G- DC Power Supply
H- 4Nos Anode SS/ Silver
I- Heater with Thermostate
Figure 2: Lay out of mobile metalising equipment

DETAILEP DESCRIPTION OF PREFERRED EMBODIMENT:
The invention will now be described in an exemplary embodiment as depicted in the
accompanying drawing. There can however be other embodiments of the same invention,
all of which are deemed covered by this description.
The invented machine has following components:-
S.S. Tanks (A, B, C, D) Figure 1 has four numbers of stainless steel tanks each of 12 Lts.
capacity. These tanks contain Degreasing Solution (A), Copper Solution (B), Silver striking
Solution (C) and main Silver Solution (D). Degreasing Tank (A) and Copper Solution Tank
(B) are fitted with electric heaters to raise temperature of the solution to 40° C.
Circulating Pump (E) has capacity of circulating 1800 Lts. of fluid per hour. This pump is
suitable for hot chemicals.
Circulating pump (E) is connected with a timer which is set for 20 minutes for degreasing,
30 minutes for copper solution, 15 minutes for silver striking and 30 minutes for main
silver plating. After circulating required solutions for set period of time, pump
automatically stops.
Glove Valves (Item 1-19) total 19 number of valves have been used in the pipe lines
connecting tanks to the pump and pump to the Electroplating adopter mounted on the
Core Bar. Valve no- 1, 2, 3 and 4 are mounted on the pipe lines connecting tanks to the
inlet of the pump.

Valve no- 5, 7, 9 and 11 are mounted on the pipe lines connecting tanks and out let of
the adopter. After circulation chemical return back through these valves to the respective
tanks. Valve no- 6, 8,10 and 12 are connected on the branch line drawn from outlet from
the adopter. These branch lines are opening in the tank. Valve no-14 is used for
compressed air and valve no-15 is used for supply of clean water. Valve no- 16, 17, 18
and 19 are connected on the drain line from each tank. First of all non-metallic Adopter
(F) is mounted on the Core Bar fitted in the shaft in which Electroplating is to be done.
Four numbers of Anodes (H) (Steel) are fixed in the adopter for degreasing operation.
Technological bolt fitted in the Core Bar is used as Cathode. Outlet from the pump is
connected with the inlet of the adopter (F) with flexible pipes. Outlet from the adopter is
connected with the inlet pipe line going to the tanks. Anode (Steel) and Cathode (Core
Bar) connected with the 2.5 Volt DC (G) supply source (Rectifier). At first step degreasing
operation is carried out. Timer is set for 20 minutes operation of the pump. Valve no- 1,
5, 8, 10 and 12 are opened and rest of the valve are kept closed. Pump is switched-on
for circulation of degreasing solution. Once the degreasing operation is over, valve no-1
is closed. New valve no- 14 is opened for supply of compressed air. Purpose of
compressed air is to drain out all the trapped degreasing solution in the system. Now
valve no- 14 is closed and valve no- 15 and 6 are opened for supply and drain of clean
water to wash out traces of degreasing solution. Compressed air is again supplied to dry
out water droplets from the system after closing valve no 15 and 6.
Before starting Copper plating, Silver Striking and main Silver plating operation, DC
source is switched on to supply current to the Copper or Silver Anodes fitted in the
adopter for electroplating on steel or copper core bar. Supply of copper solution at 40° C
is required only for steel core bars for Copper plating prior to silver plating.

Supply of fluid from copper solution tank (B) at 40° C, silver striking tank (C) and main
silver tank (D) at normal temperature to adopter through pump and return of the fluid to
the respective tank is done by opening and closing of concerned valves in similar fashion
in case of degreasing operation. After completion of each stage, supply of compressed air
followed by circulation of clean water and then again blowing with compressed air is
repeated. In case of final Electroplating operation additional operation of circulating half
water and subsequent blowing with compressed air is carried out to eliminate any
possibility of cyanide traces inside the system.

WE CLAIM:
1. A device for electroplating axial pin holes in generator rotor, exciter rotor and slip
ring shaft core bars in turbo generators comprising:-
• stainless steel tanks (A, B, C, D)
• circulating pump (E) with timer
• glove valves (Item 1 to 19)
• electroplating adopter (F)
• pipe line
• D.C. supply source (G)

2. The device as claimed in claim 1, wherein 4 no of such tanks each of 12 It.
capacity, contain degreasing solution (A), copper solution (B), silver striking
solution (C) and main silver solution (D).
3. The device as claimed in claim 2, wherein degreasing tank (A) and copper solution
tank (B) are fitted with electric heaters to raise the temperature of the solution to
40° C.
4. The device as claimed in claim 1, wherein the circulating pump (E) has capacity of
pumping 1800 liters of fluid per hour and is suitable for hot chemicals.
5. The device as claimed in claim 1, wherein a timer is connected with the circulating
(E) pump which can be set for predetermined time for degreasing, circulating,
silver striking and main silver plating operation.

6. The device as claimed in claim 1, wherein the pump automatically stops after
circulating required solutions for a predetermined period of time.
7. The device as claimed in claim 1, wherein 19 no. of glove valves are in operation
in pipe lines which connect respective tank to the pump and pump to the
electroplating adopter mounted on the core bar, or the outlet of the adopter to the
effluent tank, or supply of clean water or compressed air or connect drain line to
individual tank.
8. The device as claimed in claim 7, wherein valve no 1, 2, 3 and 4 are mounted on
the pipe line connecting tanks to the inlet of the pump, and valve nos. 5, 7, 9 and
11 are mounted on the pipe line connecting tanks and outlet of the adopter, so
that after circulating chemical returns back through these valves to the respective
tank.
9. The device as claimed in claim 8, wherein valve nos. 6, 8, 10 and 12 are
connected on the branch line drawn from the outlet of the adopter, which open on
the effluent tank.
10. The device as claimed in claim 1, wherein in valve no 14 is used for compressed
air, and valve no 15 for supply of clean water and valve "no 16,17,18, and 19 are
connected on the drain line from each tank.
11. The device as claimed in claim 1, wherein inlet and outlet pipes are of 1/z inch
diameter.

12.The device as claimed in claim 1, wherein D.C. supply is of 2.5 volt and is supplied
through a rectifier.
13. A method for working the electroplating machine as claimed in claim 1 comprising
steps of:
• mounting the non-metallic adopter on the core bar fitted in the shaft
• fixing four numbers of steel anode in the adopter for degreasing
operation
• using technological bolt in the core bar as cathode
• connecting outlet from the pump with the inlet of the adopter with
flexible pipes
• connecting outlet from the adopter with the inlet pipe line going to
the tanks
• connecting anode (steel) and cathode (core bar) with 2.5 V D.C.
supply source (rectifier)
• degreasing
• copper plating
• silver striking
• main silver plating
• draining
14. A method as claimed in claim 13, wherein degreasing operation is carried out by
switching on the pump for circulation of degreasing solution by setting the timer
for 20 minutes, and opening valve no 1, 5, 8, 10 and 12 keeping the rest of the
valves closed.

15. A method as claimed in claim 14, wherein the valve nol is closed once the
degreasing operation is over, and valve no 14 is opened for supplying compressed
air.
16. A method as claimed in claim 15, wherein valve no 14 in closed and valve no. 15
and 16 are opened for supply and drain of clean water to wash out traces of
degreasing solution.
17. A method as claimed in claim 16, wherein compressed air is again supplied to dry
out water droplets from the system after closing valve no. 15 and 6.
18. A method as claimed in claim 13, wherein 2.5 Volt D.C; supply is switched on to
supply current to the copper or silver anodes fitted in the adopter (F) for
electroplating on steel or copper core bar, before starting copper plating, silver
striking and main silver plating operation.
19. A method as claimed in claim 13, wherein supply of copper solution at 40° C is
made from copper solution tank (B) to the adopter through circulation pump (E)
for 30 minutes by setting the timer for electroplating of copper in steel core bars
only and the fluid is allowed to return to the tank by opening valve nos. 2, 7, 10
and 12 and keeping the rest no. of valves closed.
20. A method as claimed in claim 13, wherein supply of striking sliver solution and
main silver solution is made successively from tank (C) and tank (D) respectively
at normal temperature to the adopter through circulation pump (E) by setting the
timer for 15 minutes and 30 minutes for silver striking and main silver plating by
opening valve no. 3, 9, and 12 and valve no. 4 and 11 respectively and keeping
other valve closed for return of the fluid to the respective tank.

21. A method as claimed in claim 15, wherein supply of compressed air is followed by
circulation of clean water and then again blowing with compressed air repeated
after completion of each stage, and in case of final electroplating operation
additional operation of circulating half water and subsequent blowing with
compressed air is carried out to eliminate any possibility of cyanide traces inside
the system.

A device for electroplating axial pin holes in generator rotor, exciter rotor and slip ring
shaft core bars in turbo generators. It comprises of four tanks (A, B, C, D) containing
degreasing solution (A), copper solution (B), silver striking solution (C) and main silver
solution (D). The tanks are connected to the circulating pump (E) and to the
electroplating adopter (F). The adopter is used as anode and core bar as cathode. Output
of adopter is connected individual tank or to effluent tank. The machine is also connected
to a source of compressed air and clean water. The flow of fluid takes place through a
pipe line controlled by 19 no. valves. At first degreasing in done by pumping degreasing
solution from tank (A) into the system by opening and closing a set of valves for a set
period of time. Then copper plating is done by pumping copper solution at 400 C to the
adopter for a set time for steel core bar, followed by circulation of silver, striking solution
and main silver solution at room temperature. Finally it is washed and dried by clean
water and compressed air to remove traces of cyanide.