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Manufacturing Technology- II
GOOD ENGINEERING PRACTICES
S.C.Ghosh
Date: 13/01/2006
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2. Check the seam number on the job.
( A ) BEFORE S TARTING WE LDING
1. For specific seam :Refer shop weld plan, WP S and test plan.
IMPORTANT CODE REQUIREMENT AND
PRACTICES RELATED TO WELDING
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5. Check calibrations of weldingmachine and carry out trialwhere required.
CALIBRATIONDUE ON:
31.10.99
E7018
Supercito E 7018
3. Check identification marks of welding consumables.
4. Process Quantity (max. )SMAW 15 Electrodes
SAW/FCAW 1 Wire SpoolSAW Flux 10 KgE S SC Flux 25 Kg
IMPORTANT CODE REQUIREMENT AND
PRACTICES RELATED TO WELDING
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( A ) BEFORE STAR TING WE LDING
6. Check cable connections and earthing.
8. Provide run - in, run - out plates for L - seams.
25 mm 25 mm
25 mm25 mm
7. Clean WEP+25 mm on either side. Remove rust , paint, oil etc.
IMPORTANT CODE REQUIREMENT AND
PRACTICES RELATED TO WELDING
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11. Use SS wire brush /wire wheel for SS, Inconels , Monels and
Cupro-nickels. Do not use grinding wheels used on CS.
9. Get temperature sticks for preheat & interpass.Temperature > Preheat
< Interpass
25 mm 25 mm
BURNER
10. Check preheat at least 25 mmaway from WEP on both sides.
IMPORTANT CODE REQUIREMENT AND
PRACTICES RELATED TO WELDING
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2. Weaving < 3 x Electrode diameter.Ensure specified bead length
( B ) WHILE WE LDING
1. Tacks and temporary cleats- Use specified electrodes and preheats- Qualified Welder- No hammering
4. SMAW Electrode left over after 4 hrs - return to stores.
3. No st ray arcing on job.
IMPORTANT CODE REQUIREMENT AND
PRACTICES RELATED TO WELDING
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2. Return unused consumable to shop stores.
( C ) AFT ER WE LDING
1. Welder stamp to be stamped on seams - max. 3 feet apart.
Max. 3 feet
IMPORTANT CODE REQUIREMENT AND
PRACTICES RELATED TO WELDING
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( A ) GENE RAL
1. Use correct shade of welding glass.
WRONG RIGHT
2. Keep your head out of welding fumes.
GOOD PRACTICES FOR WELDING
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3. Do not direct fan air on welding arc .
GOOD PRACTICES FOR WELDING
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4. When working in confined space ensure adequateventilation / exhaust.
CONFINED SPACE
BLOWER
WELDING
GOOD PRACTICES FOR WELDING
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1. El iminate mix-up of electrode / fil ler wire / flux.
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140 Gms / mt
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250 Gms / mt
2. Never over weld fillets ---
- 6 CFW to 8 CFW - 78 % extra weld .
- Loss of man hours + consumable
- Distortion.
GOOD PRACTICES FOR WELDING
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3. Give minimum root gaps for fi llet joints - 3mm gap on
6 CFW increases weld metal by 125 %.
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125% WELD META L
GOOD PRACTICES FOR WELDING
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5. Weld bead restart - end : return arc on crater to f ill up the craterand to avoid crater cracks - porosi ty
- restart ahead of end crater so that end crater gets melted andfilled - up.
ENDCRATE R CRACK
4. Do not give excessive reinforcements.
GOOD PRACTICES FOR WELDING
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7. For NG - SAW and ESSC follow instructions from welding Engg.
6. Burn complete electrode - max. stub and should be 50 mm.
E7018
< 50mm
E7018
> 50mm
GOOD PRACTICES FOR WELDING
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( B ) SAW
1. Use only hot flux.
2. Flux is costly - always use flux recovery units-return unused flux.
3. Re - use flux only after screening cleaning and rebaking.
4. Keep flux height 25 to 35 mm during welding.
GOOD PRACTICES FOR WELDING
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6. Adjust travel speed before starting welding .
7. Ensure that current versus wire feed rate chart is available.
8. Use constant voltage mode for DC - SAW.
35-50 mm
5. While welding circ - seams the fil ler wire should be lagging by35-50 mm.
9. If f lux is not peeling off easily, there is a problem - solve it before
continuing.
GOOD PRACTICES FOR WELDING
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NG SAW
Additional requirement
1. Ensure proper alignment of the seam and welding head.
2. Ensure that long neck grinder is available.
3. Follow proper bead sequence .
4. Ensure proper wire posit ion from side-wall.
GOOD PRACTICES FOR WELDING
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ESSC
1. Ensure cable connections and followingWelding head wrt jobCleanliness of surfaceSmooth flow of str ip thro jawsMounting arrangement of spoolLevel of jobFlux feeding arrangement
2. Adjust the Stick- out using template..
3. Ensure all welding parameters before start of overlay .
4. Ensure the correct polarity of magnetic stir ring device.
5. Ensure correct flux height
6. Ensure proper bead overlap
GOOD PRACTICES FOR WELDING
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3. End craters of S S, Inconel, Nickel, Monel overlay show crack if
current is high, arc length is longer and cleanliness i s notmaintained. Crater must be filled up.
( C ) WELD OVERLAY
1. Use only specified voltage / current / travel speed to avoid higherdilution.
4. Bead overlap must be minimum 50 %.
2. Higher dilution may result in cracking : weld with correctparameters .
GOOD PRACTICES FOR WELDING
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5. Minimum bead length per electrode must be achieved.
SS
CS
6. Clad stripping must remove complete SS material, check with
CuSo4 solution.
GOOD PRACTICES FOR WELDING
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( D ) TUB E TO TUB ES HE E T WELDS
1. Remove rust - grease from tube O.D. before insert ions.
2. Take care while tacking tube - tacks may result in poros ity.
3. Give minimum two passes. Both passes must be weldedwith fil ler wire addition.
4. Do not have common end craters for both passes - stagger
them.
5. Avoid tube edge burning or tube I.D. burn through.
GOOD PRACTICES FOR WELDING
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( E ) PIPE # PIPE BU T T JOINT S
1. Set up should be done after cleaning I.D.weld as soon as poss ible after set up
2. Thin pipes ( up to 4mm thk ) - weld using two passes ( GTAW )-do not end both passes on same location stagger the ends.
3. Root set up must be accurate - or problem of lack of penetration( less root gap, thick root face ) - will occur.
( F ) NOZZL E # SHE L L / DJOINTS ON THICK VES S E L S
1. These are highly restrained joints - and tacks may cracks.Weld thick tacks 4 - 6 passes.
2. Ensure higher preheat ( +25 C ) on nozzle forging.
3. Do not cool from preheat temperature till half the groove
thickness is welded.
GOOD PRACTICES FOR WELDING
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GOOD ENGINEERING PRACTICES FOR SS
Clean WEP + 15 mm on either side of WEP with acetone
Do not walk over the SS surface
CS/LAS consumable must not come in contact with SS
During rolling of clad plated,clean rollers to avoid dents and direct
contact of CS roller
Use only SS wire wheel/wire brush for cleaning
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GOOD ENGINEERING PRACTICES FOR SS
Do not use grinding wheel previously used used on CS/LAS
Maintain interpass temperature to avoid overheating
Do not leave welding slag after welding
All temporary attachments/run in run out plates shall be SS
During removal of temporary attachment from clad surface,ensure no
ripping of clad material
Carry out CuSO4 test after clad stripping
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GOOD ENGINEERING PRACTICES FOR SS
Clad stripping shall not be done by arc air gouging
Spatter on stainless steel damage protective surface oxides
Weaving
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GOOD ENGINEERING PRACTICES FOR SS
During welding of thin jobs(-15mm),take care of followings
More distortion in SS
Thermal conductivity of CS
Expansion of thermal coefficient 1.5 times of CS
WEP angle,Root gap,root face to be optimized
Pickling to remove all impurities