Orbital welding became practical for many industries in the early 1980`s when combination power supply /control systems were developed that operated from 110 VAC and were physically small enough to be carried from place to place on a construction site for multiple in ?place welds. Modern day orbital welding systems offer computer control where welding parameters for a variety of applications can be stored in memory and called up when needed for a specific application. The skills of a certified welder are thus built into the welding system, producing enormous numbers of identical welds and leaving significantly less room for error and defects..

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PLANT CAPACITY – 2 X 1000 MWe
STEAM TURBINE
ORBITAL WELDING
Purpose – To provide leak proof joint between Tube to tube sheet in Condenser in addition to Forced expansion
TITANIUM TUBES
Grade : ASTM B 338 Gr2
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 260 0 C.
Even exposed to sea water for many years at a depth of over a mile shows no measurable corrosion
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
RUSSIAN REFERENCE DOCUMENTS
GOST 3242 – 79 Welding joints Quality Control Methods
RD 24.020.00-93 (Guide lines welding joints of mixed steam, gas and Hydraulic Turbines)
PNAEG 7-003-87 Welder qualification
PNAEG 7-010-089 Acceptance standard
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
WPS AND PQR
METALLOGRAPHIC TESTING
Sample ID: 2
Measurement of individual inclusions and clusters as per Table .19 of PNAEG-07-010-89 of 11.11 metallographic analysis:
L = 0.622 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 = 0.622
a = 0.620
MACHINE & OPERATOR QUALIFICATION
WELDING MACHINES:
FRONIUS MODEL - FPA 2000 - 4 Nos
VJ MARCONS - HYDERABAD - 2 Nos
TUBE TO TUBE SHEET WELDING
WELDING HISTORY
CLEAN ROOM
WATER BOX
TYPE OF WELD DEFECTS
Efforts to change the acceptance norm-2 Letters
Welding Accessories
Heat Sink
Manual Welding
Trailing Shield
MOCK UP BLOCK WITH CRATED CRACKS
Ti DISC WITH HOLDER
Ti DISC FIXING
FINISHED HOLES
FINISHED HOLES
ESSENTIALS FOR GOOD WELD JOINT