Goa

THE VPI PROCESS 

 

 

INTRODUCTION TO VACUUM PRESSURE IMPREGNATION SYSTEM Drawback of earlier VPI SYSTEM Failures were due to two types of problems: Tape separation Excessive relaxation of the main ground insulation

Vacuum Pressure Impregnation of resin poor insulated jobs 









Preheating:the completed stator for period of 12 hrs at 60 deg ,temp>85deg Lifting and shifting Vacuum cycle: vacuum pressure of about 0.2 mb is maintained for about 17 HRS Vacuum drop test Heating the resin

  

  

Resin admission. Resin settling Pressure cycle: subject resin to pressure cycle of 4 kg/ cm2 of dry nitrogen, subj for 2 hrs. Aeration Post curing cycle Cleaning

FACILITIES AVAILABLE IN VPI PLANT IN BHEL    

  

Steam furnace for preheating Size of chamber: 2 * 2 * 6.5 M Maximum temperature: 160°C Electrical power consumption: 75KW Work place: 1425 Work centre: 3215 Stream inlet: 200-250°C

Date and time

RTD-I(°C)

RTD-II(°C)

Furnace air temperature

Remarks Rotor temperatur e is reached to 60±3°C at 2:00hrs on 31.5.2007 and it is maintained for 4 hrs i.e., up to 6:00 on 31.5.2007

30.5.2007

19:00

32.0

30.0

45.6

30.5.2007

20:00

45.4

48.6

57.9

30.5.2007

21:00

49.9

50.9

63.4

30.5.2007

22:00

52.5

54.3

70.5

30.5.2007

23:00

53.3

55.1

73.4

30.5.2007

24:00

56.6

57.3

75.6

31.5.2007

1:00

59.9

60.2

75.1

31.5.2007

2:00

62.4

63.9

77.0

31.5.2007

3:00

62.3

64.7

77.0

Rotor is switched to vac 140 tank at 7:00 hrs on 31.5.2007

31.5.2007

4:00

63.3

64.1

75.0

31.5.2007

5:00

63.3

64.0

75.6

31.5.2007

6:00

63.1

63.7

75.6

Date and Time

Resin cycle

Vacuum in graph (mbar)

Vacuum in meter (mbar)

Job temperature (°C)

8.5.2007 22:00

--

--

54.37

Resin tanks 025,102 are heated for impregnation

8.5.2007 0:00

--

--

54.89

Viscosity of resin at 60°C is 33CP

9.5.2007 2:00

--

--

59.02

Viscosity after aging is 36.10CP

9.5.2007 3:30

0.65

0.65

61.6

9.5.2007 and 10.5.2007

9.5.2007 5:30

0.41

0.40

63.59

Resin admission started at 19:45hrs

9.5.2007 7:30

0.28

0.29

64.2

Resin admission completed at 19:55hrs

9.5.2007 9:30

0.22

0.22

63.2

Pressurisation started at 20:00hrs

9.5.2007 11:30

0.19

0.19

62.3

Pressurisation of 4kg/sq.cm reached at 21:20hrs

9.5.2007 13:30

0.18

0.18

62.1

Pressurisation hold up for 3hrs is at 0:20hrs

9.5.2007 15:30

0.17

0.17

62.0

Resin withdrawn to storage tanks is from 0:30hrs –1:00hrs

9.5.2007 17:30

0.14

0.14

61.8

Stator loaded in hot air furnace from 1:00hrs – 1:30hrs on 10.5.2007

Date and Time

ESOH 15T

TSOH 06B

ESW 02

TSW 13

Core

Room temperature

10.5.2007 1:30hrs

70.0

76.4

62.4

62.5

63.4

33.1

10.5.2007 4:30hrs

126.7

131.4

94.7

102.3

98.8

31.7

10.5.2007 7:30hrs

144.3

154.1

125.4

134.5

126.1

31.6

10.5.2007 10:30hrs

147.7

154.9

139.9

145.1

140.6

34.8

10.5.2007 13:30hrs

137.6

144.4

139.3

141.6

140.7

38.0

10.5.2007 16:30hrs

136.9

144.2

140.0

140.9

140.6

38.4

10.5.2007 19:30hrs

140.2

143.6

140.1

140.7

140.2

37.2

Remarks

10.5.2007 22:30hrs

144.4

151.3

143.7

145.1

144.1

35.9

11.5.2007 1:30hrs

143.1

146.7

145.2

145.1

145.2

33.8

11.5.2007 4:30hrs

144.3

151.0

143.6

144.0

144.7

31.1

11.5.2007 7:30hrs

135.7

142.1

144.3

145.1

145.0

31.3

11.5.2007 10:30hrs

135.0

135.7

135.1

135.0

135.8

34.8

11.5.2007 13:30hrs

135.6

141.4

135.4

135.6

135.9

38.3

11.5.2007 17:30hrs

148.0

149.2

142.8

142.2

142.1

39.8

Job temp. is reached to 140±5°C i.e., from 136.2°C to 145.6°C at 9:30hrs on 10.5.2007 and it is maintained for 32hrs i.e. up to 17:30hrs on 11.5.2007.

Furnace is switched off at 17:30hrs on 11.5.2007 and circulation fans kept running till the job temperature is reached from 70°C- 75°C







Impregnated tubs for keeping jobs For vertical impregnation: As per respective tech. Document. For horizontal impregnation: As per respective tech. Document

  



      

  

Specifications of plant: Impregnation medium Epoxy resin (class F solvent free) and hardener mix in 1:1 ratio as per TG34967 Epoxy resin (class F solvent free) and hardener mix in 1:1 ratio as per TG34931 Horizontal impregnation chamber Diameter: 4000mm Cylindrical length: 9000 mm Operating over pressure: 6 bar Operating vacuum: 0.15 mbar Operating temperature: 90°C Loading weight of impregnation object: maximum of 120 tonnes Maximum leakage rate: less than 1mbar/lit/sec. Moving load: 140 tonnes. Static load: 170 tonnes

   

        

Pressure medium for impregnation Pressure medium: dry nitrogen Operating pressure: 6 bar. Nitrogen storage capacity: 52cubic meter at 25 bar. Resin storage capacity Total storage: 5*9000L+1*3000L Operating parameters of each tank Operating vacuum: 0.5mbar Operating over pressure: 0.5bar Operating temperature: 80°C Resin filters(stainless steel washable) Filter fineness: 150microns Output (maximum): 1000lits/min

     

 

   

        

Vacuum system Root pumps: 2No.s, 5.5KW each Suction capacity: 2000cubic meter/hr Vacuum pumps(4No.s, 7.5KW each) Suction capacity: 250 cubic meter/hr This system is provided with separator filter with activated carbon filters, to protect the vacuum pumps from resin and hardener vapours. Refrigeration system The resin inside the tanks has to be stored at 10±2°C. this can be stored for indefinite period with a brine chilling/refrigeration system. The brine storage capacity: 1*25000L+1*26000L Composition of brine: 40%Mono Ethylene glycol and 60%water Heating and cooling system The heating of resin in the storage tanks and the impregnation chamber is by circulating the heated brine through the heat exchangers, to heat by saturated steam. The hot brine is cooled to about 40°C by circulating water through coolers and then the brine is chilled to -10°C and stored in the tanks. Post heating of job Explosion proof steam drier and electrical heating superposed. Size: 7*4.5*4.5M Maximum weight of job: 80 tonnes Maximum temperature: 150°C Indirectly heated hot air circulating oven (gas fired) Size: 9*4.5*4.5M Maximum weight of job: 170 T/120T with facility for rotation. Maximum temperature: 150°C

DATA COLLECTION OF SAMPLES 

INDO-BHARAT-II ROTOR

Preheating: Indo Bharat II rotor is loaded for preheating in steam furnace on 30-5-2007 at 18:00hrs.

RESIN POOR SYSTEM

• • • • • •

RESIN RICH SYSTEM

The insulation tape used in this system has 40% resin. This method follows thermosetting process. There is a need for addition of resin from outside. Reduction in time cycle for this process

•

No tests are carried out while at processing Processing of bars along with stator and with conductors and processing of exciter Coils along with exciter is possible.

•

•

The cost of repair is more

•

The overall cost is less compared to resin rich system.

• • •

• • •

The insulation tape used in this is 7% of 40% resin. Same as in resin poor. Further addition of resin is not required from outside. It is very long process and time consuming while at processing stage. Tests are being carried out Stage. Processing of stator bars is only possible in resin rich systems. Repairing work is easy. The total cost in this process is more.

JUSTIFICATION  

Justification can be done by two tests HV and TAN δ tests

PRESENT INSULATION SYSTEMS IN THE WORLD 

 



1. Vacuum pressure impregnation (VPI) of individual coils and bars 2. Global VPI of complete stators 3. Hydraulic molding of individual coils and bars using resin-rich tapes 4. Press curing of individual coils and bars, also using resin-rich tapes

Westinghouse Electric Co.: Thermalastic™  General Electric Co. :Micapals I anII™,EpoxyMicaMat™, Micapal HT™, and hydromat™  Alsthom, GEC Alsthom, Alstom Power: Isotenax™, Resitherm™, 

Siemens AG, KWU: Micalastic™

 

 



ABB Industrie AG: Micadur™, Toshiba Corporation: Tosrich™ and Tostight- I™ Mitsubishi Electric Corporation Hitachi, Ltd.: Hi-Resin™, Hi-Mold™, and Super Hi-Resin™ Summary of Present-Day Insulation Systems

A NEW hype IN INSULATION SYSTEM 

MICALASTIC  The MICALASTIC Insulation in ITAIPU™  Manufacturing and Design  Fitting of Roebel Bars into Slots:  Thermal Stability

CONCLUSION: