1. ORBITAL WELDING
AN EXPERIENCE
AT KKNPP

2. PLANT CAPACITY – 2 X 1000 MWe 3 Nos. per unit STEAM TURBINE
1 HPC + 3 LPC
3 Nos. per unit
CONDENSER
TITANIUM TUBES
Size 25 X 0.6mm
15 meters long
90000 Nos.

3. Process – GTAW without filler wire addition
ORBITAL WELDING
Purpose – To provide leak proof joint between Tube to tube sheet in Condenser in addition to Forced expansion
Process – GTAW without filler wire addition
SIGNIFICANT ASPECTS
Material-Titanium
Large Qty of welding
Welding in position & at site
Material supply by Russians

4. TITANIUM TUBES Grade : ASTM B 338 Gr2 Tube Sheet : 35 + 5 mm thick
Material : ASTM A516Gr ASTM B 265 Gr 1 CLAD
Why Titanium is used?
Provides excellent resistance to general and localized attack under most oxidizing, neutral and inhibited reducing conditions in aqueous environments.

5. Titanium Cont….
Corrosion Resistance due to stable, protective strongly adherent oxide film which forms instantly when a fresh surface is exposed to air moisture.
This film is transparent and not deducted by visual means.
Titanium resist corrosion by sea water to temperature as high as C.
Even exposed to sea water for many years at a depth of over a mile shows no measurable corrosion.

6. Titanium Cont….
Provides over 25 years of trouble free sea water service for chemical refinery de-salination and nuclear industries
Has the ability to resist erosion by high velocity sea water
The presence of abrasive particles such as sand has only a small effect on the corrosion resistance of Titanium

7. Production began in the late 1950s
Most widely used titanium is commercial pure (99.5 % Ti)
Manufacturing Process
Ingot →slab → Hot strip → cold strip → Slitting → Forming → TIG Welding → Stress relieving → Eddy Current & Ultrasonic testing

8. Physical Testing
Tensile, flare, flattening & reverse flattening
Visual Inspection
Cleanliness, ID, OD, Surface condition, end condition and marking.
Tube to tube sheet joining
Contact Rolling (0 to 5 % wall thinning for a length of 10 mm)
Orbital Welding – For highly reliable leak tightness
Forced Rolling (8 to 10 % wall thinning for a length of 25mm)

9. Titanium tube insertion
PROCESS FLOW CHART
Sh 1 of 3
Front / Rear end tube sheet cleaning – wire brush mounted in portable drilling machine followed by acetone
Visual inspection
Titanium tube insertion
Initial cleaning before contact rolling
Initial contact rolling up to 10mm

10. Final expansion 8 to 10 % by lubricating SAE 40 oil
PROCESS FLOW CHART CONTD…
Sh 2 of 3
End facing of tube & tube sheet up to 0.05 mm
Welding
Excess length trimming in the rear side
Visual inspection
Rectification of repair work
Final expansion 8 to 10 % by lubricating SAE 40 oil

11. Final cleaning by acetone
PROCESS FLOW CHART CONTD…
Sh 3 of 3
Final cleaning by acetone
Dye Penetrant testing
Tube tightness test by MAUS Gun G-150

12. RUSSIAN REFERENCE DOCUMENTS
GOST 3242 – 79 Welding joints Quality Control Methods
RD (Guide lines welding joints of mixed steam, gas and Hydraulic Turbines)
PNAEG Welder qualification
PNAEG Acceptance standard

13. WORK PROCEDURES Condenser Tubing and expansion
(Doc.No: BHEL / KKNPP / WP / 023)
Condenser Tube Welding
(Doc.No: BHEL / KKNPP / WP / 024)
Condenser Tube to Tube sheet welding repair procedure (Doc.No: BHEL / KKNPP / WP / 031)

14. TUBE SPECIFICATION

15. UNIT-2 TUBE INSERTION

16. AFTER TUBE INSERTION

17. TUBE SHEET PROTECTION

18. FRONIUS MODEL - FPA 2000 (AUSTRIAN MAKE)
PROGRAMABLE ORBITAL WELDING MACHINES
FRONIUS MODEL - FPA 2000 (AUSTRIAN MAKE)

19. Welding parameters for FRONIUS MODEL - FPA 2000
Process : GTAW (Automatic ) No of weld passes 1 Argon Gas flow rate to 6 ltr /min Pre Gas time T Sec Post Gas time T Sec Pre Fusion current I A Pre fusion current time T Sec Pulse current I A Time of pulse current T msec

20. Welding parameters for FRONIUS MODEL - FPA 2000 (Cont…)
Back ground current I A
Time of back ground current T m sec
Down slope state N D
Down slope time T Sec
Welding Speed V = 125%
Tungsten electrode:
Grade- WL10
Diameter- 1.6 mm
Inclined Angle – 2 0
Grinding Angle – 15 0

21. PROGRAMABLE ORBITAL WELDING MACHINES
VJ MARCONS - HYDERABAD (Indian Make)

22. WELDING PARAMETERS FOR VJ MARCONS HYDERABAD
Name of the weld programme :KK1 No of weld passes : 1 Aux Gas shield required : Yes Torch shield gas delay, Sec :10 Pre gas time, sec : 3.0 Overlap required, mm :8.0 Up slope time, sec : 2.0 Pre heating time, sec : 1.0 Down slope time, sec : 5.0 Post weld gas flow time, sec :3.0 Aux Gas turn off delay, sec :5.0 Pulse welding : Yes Peak Current, amps : 90.0

23. WELDING PARAMETERS FOR VJ MARCONS HYDERABAD (Cont…)
Base Current, amps : 20.0
Peak time, sec : 0.1
Base time, sec : 0.1
Welding speed, RPM : 2.0
Diameter of the tube, mm : 25

24. WPS AND PQR
WPS: BHEL/KKNPP/WPS/004 & 005 PQR: BHEL/KKNPP/PQR/004 & 005
Welding Process: Automatic TIG Welding with out filler material addition 7 Welds Per Machine Per Operator
NDT – Visual (Uniform contour free from spatter, burn-through, cracks, surface pores etc.
Weld spillage, undercut, weld color, DPT etc.
Destructive Testing
Metallographic Examination – Minimum leak path, Weld width and height.

25. METALLOGRAPHIC TESTING
Sample ID: 2
Measurement of individual inclusions and clusters as per Table .19 of PNAEG of metallographic analysis:
L = mm
No. of inclusions present – Nil
a =0.620 mm
h=1.02 mm
H=1.39 mm
W=3.48 mm
Mag: 10x Etchant:5%HF
Calculation of Minimum Leak Path (L) = a + Σdp > 0.7t
dp = d1 + d2 where d = dia of the pore
t = Thickness of the tube = 0.6mm
L =
a = 0.620
W=3.48 mm
H=1.39 mm
h=1.02 mm

26. MACHINE & OPERATOR QUALIFICATION
WELDING MACHINES:
FRONIUS MODEL - FPA Nos
VJ MARCONS - HYDERABAD Nos
CONTACT & FORCED ROLLING MACHINES
CONTACT ROLLING SUGINO 502 L Nos
FORCED ROLLING SUGINO 506 L Nos
OPERATORS
WELDERS
CONTACT ROLLING
FORCED ROLLING

27. TUBE TO TUBE SHEET WELDING

28. WELDING HISTORY Start of welding in Unit-1 :29-03-06
Completion in Unit-2 :
Average out put
FRONIUS MODEL - FPA : 250 Joints/Shift/Machine
VJ MARCONS - HYDERABAD :200 Joints/Shift/Machine

29. TUBE TIGHTNESS CHECK BY MAUS GUN G-150
Compressed Air System Pressure
3 to 9 Bar
Air flow rate
30 l/min
Test pressure holding time
5 to10 sec

30. CLEAN ROOM

31. WATER BOX

32. TYPE OF WELD DEFECTS
Transverse Cracks
Color Change
Blow Holes
Pores

33. TYPE OF WELD DEFECTS Defective Shape Surface pores Burn Through-Minor
Burn Through-Major
Burn Through-Minor

34. WELD DEFECTS RECTIFICATION
Efforts to change the acceptance norm-2 Letters
Repair – by machine or manual
Manual-Filler wire (Russian), ASTM
-Color change (Gas lens), Trailing shield
-Trailing shield (Half circle, Rectangle)
-Qualification requirement
-Creation of defects
-welder availability

35. Welding Accessories

36. Heat Sink

37. Manual Welding

38. Trailing Shield

39. RECTIFICATION USING Ti DISC
CRITICAL WELD DEFECTS
RECTIFICATION USING Ti DISC

40. MOCK UP BLOCK WITH CRATED CRACKS

41. PULSE TIG MACHINE

42. Ti DISC WITH HOLDER

43. Ti DISC FIXING

44. DRILLING

45. FINISHED HOLES

46. FINISHED HOLES

47. ESSENTIALS FOR GOOD WELD JOINT
Joint preparation-Paint removal, cleanliness, end facing
Clean room environment
Process parameters, Welding machine, Operators
Parent material & Cladding Quality
Heat in put & Post expansion control

48. Titanium is a Royal material and one does not learn unless burn his finger

49. THANK YOU