Download - (2) Pipe Welding2

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



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.



ADVANTAGES OF

ORBITAL PIPE WELDING

HIGHER DEPOSITION RATE

IMPROVED WELD QUALITYHIGHER PRODUCTIVITY

REDUCED LABOUR COST

OBVIATES THE NEED FOR SKILLED WELDERS



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



Orbital

TIGWeldingHead



Orbital TIG welding system


http://slidepdf.com/reader/full/2-pipe-welding2 7/33Welding in overhead position


http://slidepdf.com/reader/full/2-pipe-welding2 8/33Installation of cross country pipeline



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.



Wire Feeder on Floor- Type

•Uses 12.5 kg spool

•Ideal for shop use with smaller work piece



Wire Feeder on Head Type

Uses 5 kg spool

Ideal for field erection



WIREfeederon Head



Pendular Oscillator Bracket for fillet

and socket weld



Edge preparation for mechanised welding



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


http://slidepdf.com/reader/full/2-pipe-welding2 16/33Positioning the internal welder



Root pass from

inside using

automatic GMAW

Limitations:

• There is a min.pipe

dia. for ID welding.

• Operator correctionnot possible.

•

Equipment expensive.



Orbital GMA Weldingfrom outside from 12 to 6O’ clock position.


http://slidepdf.com/reader/full/2-pipe-welding2 19/33Shack for protecting the welding



Operator making

minor

changesduring

welding.



Orbital MAGWelding with

fuzzy controlled

power source



•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.



Orbital welding

of pipe using

GMAW / FCAW

processes



Productivity advantages of Orbital

pipe welding



Dual torch

welding head



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.



TWIN TorchGMAW

Higher dep. Rate

Higher travel speed

than dual torch



Forge Welding Processes

• Flash butt welding

• Homo-polar pulse welding

• Magnetically impelled arc welding.

• Radial friction welding.



Flash butt welding

• Process is suitable, included in API 1104.

• Improvements in conventional welding

overshadowed.

• Scatter and occasional lower CVN values.



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.



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.



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.



Radial friction Welding