(2) pipe welding2
TRANSCRIPT
7/31/2019 (2) Pipe Welding2
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Semi automatic Flux Cored Arc welding
• Root pass welded with metal cored wires.
• Operates in dip transfer mode.
• Include small amounts of fluxing agents
and arc stabilisers.
• 1.2 mm wire can be used in place of 0.9 mm.
• Modern flux cored wires. 5ml/100gm.
• 1%Ni wires.Good CVN value down to 40 deg. C.
•
Rutile wire [0.8] in spray mode - capping pass
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Flux Cored Arc welding
Benefits:
• All position capability.
•
Good quality weldmetal deposit.• Higher deposition rate than SMAW.
•
Low operator skill required.• Metallurgical benefits that can be gained
from a flux.
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ADVANTAGES OF
ORBITAL PIPE WELDING
HIGHER DEPOSITION RATE
IMPROVED WELD QUALITYHIGHER PRODUCTIVITY
REDUCED LABOUR COST
OBVIATES THE NEED FOR SKILLED WELDERS
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Welding process Welding speed
•SMAW Low Hydrogen
•SMAW Cellulosic.
•Semi automatic GMAW.
•Fully automatic GMAW from
outside using Cu backing.
•Fully automatic GMAW root from
inside & other passes from outside.
140 mm/min
300 mm/min
350 mm/min
1000 mm/min
1250 mm/min
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Orbital
TIGWeldingHead
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Orbital TIG welding system
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Double Jointing / Triple Jointing
• Depends on access to the site.
• Welding off- line permits flat
position welding.
• SAW process can be used.
• Recently Flux Cored wires are
used for SAW.
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Wire Feeder on Floor- Type
•Uses 12.5 kg spool
•Ideal for shop use with smaller work piece
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Wire Feeder on Head Type
Uses 5 kg spool
Ideal for field erection
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WIREfeederon Head
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Pendular Oscillator Bracket for fillet
and socket weld
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Edge preparation for mechanised welding
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Typical Orbital MIG procedure
•Double V Joint Preparation.
•Internal Root welding [six bugs].
[ Broader fit-up tolerance]
•External hot pass welding.
•
Fill and capping passes•Wire 1.0 mm dia E70S-6
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Root pass from
inside using
automatic GMAW
Limitations:
• There is a min.pipe
dia. for ID welding.
• Operator correctionnot possible.
•
Equipment expensive.
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Orbital GMA Weldingfrom outside from 12 to 6O’ clock position.
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Operator making
minor
changesduring
welding.
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Orbital MAGWelding with
fuzzy controlled
power source
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•Typical FCAW procedure
•Root pass by GMAW with E70S-6.
•Hot pass by GMAW with E70S-6.
•Remaining passes by FCAW.
•Flux Cored Wire 1.2 mm dia. E81T1 - Ni1.
•
CO2 gas shielding.
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Orbital welding
of pipe using
GMAW / FCAW
processes
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Productivity advantages of Orbital
pipe welding
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Dual torch
welding head
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Advantages of dual torch GMAW
• Deposits two passes simultaneously.
• 400 joints/day on 1060mm pipe.
• 492 joints/day on 609 mm pipe.
• Higher dep. Rate [ 1.4 times of SW GMAW]
• Higher travel speed.
• Required only 4 pass to fill 12mm wall
thickness. SW GMAW 5 passes.
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TWIN TorchGMAW
Higher dep. Rate
Higher travel speed
than dual torch
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Forge Welding Processes
• Flash butt welding
• Homo-polar pulse welding
• Magnetically impelled arc welding.
• Radial friction welding.
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Flash butt welding
• Process is suitable, included in API 1104.
• Improvements in conventional welding
overshadowed.
• Scatter and occasional lower CVN values.
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Homo-polar pulse welding • It is a resistance welding process.
• A homopolar generator is used to
deliver a single very high DC pulse.
• Weld operatio takes only 2 - 3 sec.
• Very high capital investment.
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Magnetically impelled arc welding
• It is high temp. forge welding process.
• Suitable for joining small diameter,
thin wall steel pipes.
• The rotating arc does not heat the full
wall thickness.
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Radial Friction welding
• A radial compression ring is rotatedbetween two stationary pipes.
• The ring is rotated while under
compression, so heat is generated.
• Friction weld is created between the ring
and the two pipes.• An internal mandrel prevents internal flash.
• Used for joining pipes from 150 to 300 mm.
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Radial friction Welding