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SMAW Welding Skill W 01 1
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1
SMAW SKILLSMAW SKILL
PRESENTED BY: HARDISH TRIVEDI
2
Welding process in brief
• Welding is a process of joining two metals permanently with or without heat, with or without filler metal.
• Heat sources: - Electric Arc,
- Electrical resistance - Friction
- Oxy - Fuel Flame
PRESENTED BY: HARDISH TRIVEDI
3
Welding processes
• Gas welding
- OXYFUELwelding
• Arc welding
- SMAW,GTAW,SAW,GMAW,FCAW - EBW,LBW, PAW
• Resistance welding
PRESENTED BY: HARDISH TRIVEDI
4
Arc welding processes
• Heat source
- Arc generated between electrode and base metals
• Shielding of liquid metal
- Flux-slag system
- Inert or non-reactive gas shielding
- Mixture of above two
PRESENTED BY: HARDISH TRIVEDI
5PRESENTED BY: HARDISH TRIVEDI
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Machine & accessories
• Machine must be calibrated
• Meters must be in working condition.
• Cable should be crimped by machine.
• Earthing lugs should be properly fitted.
• Earthing cable to be attached to job directly.
PRESENTED BY: HARDISH TRIVEDI
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Advantages of SMAW
• All position welding
• welding in areas of restricted access
• Wide variety of materials
• Any thickness above 3 mm can be welded
• Simpler & lighter equipment
• Low-investment
PRESENTED BY: HARDISH TRIVEDI
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Limitations of SMAW
• Slow process-low productivity
• Electrodes not available for few materials
• No scope for mechanization
• Flux coatings have limited life
• Difficult to weld open root with single side full
penetration joint.
PRESENTED BY: HARDISH TRIVEDI
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Quality of SMAW
• Welder skill in position & technique
• Welding procedure (current,voltage,bead length per electrode,weaving,arc length)
• Preheat,post heating,post weld heat treatment
• Proper condition of flux coating,baking of electrode
• Base metal & interpass cleaning
PRESENTED BY: HARDISH TRIVEDI
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Welding parameters
• Polarity
(A) DCEP (DC Electrode positive )
Reverse Polarity
(B) DCEN (DC Electrode negative)
Straight Polarity
PRESENTED BY: HARDISH TRIVEDI
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Preheat• Requirement of preheat
- Preheat min.1 inch on either side of joint
- Use only LPG / Electrical heating
- Carry out uniform preheat
- Use temperature stick to check preheat
• Advantages
- To remove oil moisture
- Prevent Fast cooling (reduce rate of
cooling.
- Minimise cracking tendencyPRESENTED BY: HARDISH TRIVEDI
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MATERIAL THICKNESS PREHEAT TEMPERATURE ( mm ) ( Deg. C )
(A) CARBON STEEL UP TO 25 10 SA 516 GR60 / 70 26 - 50 75 SA 106 GRB 51 - 75 100 SA 537 CL1 76 - 100 125
100 AND ABOVE 150(B) LOW ALLOY STEEL UP TO 25 100 ( P3 GR1,2 ) 26 - 50 125 SA 335 P1 51 - 75 150 SA 182 F1 76 - 100 175 SA 204 GRB 100 AND ABOVE 200(C) LOW ALLOY STEEL UP TO 25 125 ( P4 GR1 ) 26 - 50 150 SA 182 GRF11 51 - 75 175 SA 335 P11 76 - 100 200 SA 387GR12 CL2 100 AND ABOVE 225 (D) LOW ALLOY STEEL UP TO 25 150 ( P5A GR1 ) 26 - 50 175 SA 182 GRF22 51 - 75 200 SA 213 T22 75 AND ABOVE 225 SA 387GR22 CL2 SA 335 P22REFER SHOP WELDING PLAN / WPS FOR ACTUAL PREHEAT
Preheat
PRESENTED BY: HARDISH TRIVEDI
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Interpass temperature
• Interpass temperature - always with Upper limit - Controls Heat input - Impact properties - Chemical composition of Weld metal
- To be checked with Temp. Stick only.
The temperature of previously laid bead,
just prior to striking the next bead on it.
PRESENTED BY: HARDISH TRIVEDI
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Post heating
• Ex . : Heating at 300- 3500c, for minimum 3 and maximum 4 hrs. before allowing weld to cool to room temperature from preheat temp.
• After post heating cover the joint with asbestos cloth to control rate of cooling.
• Advantage
- To avoid crack, minimise hardness of weld metal
Raising the preheat temp. to a higher range and maintained it for specific duration before preheat temp. cools down to room temp.
PRESENTED BY: HARDISH TRIVEDI
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Cleanliness
• Weld joint must be cleaned 25mm on both
side of WEP before welding
• Oil, grease, dust, paint etc..should be
removed
(If not properly cleaned, welding will be defective - Porosity )
PRESENTED BY: HARDISH TRIVEDI
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Angle
• Electrode angle depends on welding position.
• Improper angle may result in poor bead placement.
PRESENTED BY: HARDISH TRIVEDI
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Arc length
• Gap between e tip of the electrode & the
surface of the molten weld pool.
• Proper arc length result sound weld metal.
• Generally arc length should be equal or
shorter than core diameter of electrode.
PRESENTED BY: HARDISH TRIVEDI
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Selection of electrode
• Types of electrodes
- Chemical composition of base metal
- Mechanical properties of base metal
• Dia.of electrode
- Base metal thickness
- Position of welding
- WEP
PRESENTED BY: HARDISH TRIVEDI
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Electrode dia.-current
• Generally electrode - dia. current is as below :
Dia. (mm) L (mm) Current (amp)
2.50 350 70-90
3.15 450 100-130
4.00 450 140-170
5.00 450 170-240
6.30 450 270-340
PRESENTED BY: HARDISH TRIVEDI
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Baking of electrode
• Baking is done to remove hydrogen from the electrode which may be in electrode due to moisture
• If not done which may result in repairs like porosity & crack
PRESENTED BY: HARDISH TRIVEDI
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Tacking & its importance
• Tack should be welded by qualified welder
- Use WPS
-Tack should be of approx.of 2 inch. length
• Tack should be uniformly staggered
- Put min.2-3 layers
• Importance
- To hold s/u, To avoid cracking in LAS PRESENTED BY: HARDISH TRIVEDI
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Bead placement• Sequence of passes to achieve required size of weld
and reinforcement. Joint may be Grooved or Fillet.
Improper bead placement may result in….
• Lack of fusion• Merge & re-shoot in RT (RT rework)• Poor bead finish
PRESENTED BY: HARDISH TRIVEDI
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Bead length / welding speed
• Bead length/welding speed is also important factor in case of welding. It depends on welding position & diameter, length of electrode .
• Min.bead length per electrode is as below:
Dia. Length min.bead length/Electrode
2.5 350 50mm
3.2 450 75mm
4.0 450 125mm
5.0 450 275mmPRESENTED BY: HARDISH TRIVEDI
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Weaving techniques
• Weaving permitted is max. 3 times of core dia. of
electrode
• Excessive weaving may result in ….. 1. Excessive
heat input
2. Poor mechanical properties
3. Loss of chemical ingredients
4. Excessive distortion
PRESENTED BY: HARDISH TRIVEDI
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Annealing bead welding
• Annealing bead welding is the last bead to be welded & which shall not touch base metal.
ANNEALING BEAD
PRESENTED BY: HARDISH TRIVEDI
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Bead finish & interpretation of RT
• Ensure good bead overlap (bead placement)
• Use stringer bead
• Avoid valleys & ridges
• Avoid undercuts
• Ensure uniform grinding
• Remove spatters
PRESENTED BY: HARDISH TRIVEDI
27PRESENTED BY: HARDISH TRIVEDI
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• STRAY ARCING
• CRATER CRACKS
• LAMELLAR TEARS IN PLATES
WELDING DEFECTS
PRESENTED BY: HARDISH TRIVEDI
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• SET-UP MORE THAN 24HRS OLD ( PIPE # PIPE JOINT )
• RAINY WEATHER- DRY OFF MOISTURE
• ARC BLOW DUE TO RESIDUAL MAGNETISM
WELDING DEFECTS
POROSITIES:
PRESENTED BY: HARDISH TRIVEDI
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WELD JOINT NOT CLEAN
LOWER PREHEAT TEMPERATURE
WELDING DEFECTS
POROSITIES:
• STRONG WIND FLOW ON ARC
PRESENTED BY: HARDISH TRIVEDI
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- SMAW :
DAMAGED ELECTRODE TIP
E7018
• UNBAKED- COLD ELECTRODE
WELDING DEFECTS
POROSITIES:
PRESENTED BY: HARDISH TRIVEDI
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• USE OF EXCESS CURRENT IN OUT OF POSITION WELD OR
USE OF LOWER CURRENT
START
• FAULTY RESTART TECHNIQUE
WELDING DEFECTS
POROSITIES:
PRESENTED BY: HARDISH TRIVEDI
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UNBAKED ELECTRODES / FLUXESLOW PREHEATINSUFFICIENT POST HEATINGUNCLEAN WELD JOINTS
WELDING DEFECTS
CRACKS
PRESENTED BY: HARDISH TRIVEDI
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• HEAVY RESTRAINT- WELD TACKS WITH HIGHER CROSS SECTION
• EXCESSIVE LOCAL HEATING - USE OF RING BURNERS ( NOZZLE# SHELL/ D.END JOINTS )
• USE OF WRONG ELECTRODE / FLUX
• FAULTY CONS. QUALITY / SELECTION
WELDING DEFECTS
CRACKS
PRESENTED BY: HARDISH TRIVEDI
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HANDLING OF COMPONENTS BEFORE ISR / SR IN LAS
EXCESSIVE DILUTION IN BARRIER LAYER OF SS O/L
EXCESS CURRENT / INTERPASS TEMP DURING SS WELDING
WELDING DEFECTS
CRACKS
PRESENTED BY: HARDISH TRIVEDI
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IMPROPER INTERPASS CLEANING
POOR BEAD FINISH- ROUGH, LUMPY BEADS NOT DRESSED
BEFORE WELDING
FAULTY RESTART - LUMP AT STARING POINT - TO BE
GROUND
WELDING PARAMETERS (I,V, T.S) NOT AS PER WPS
WRONG BEAD PLACEMENT
SLAG INCLUSIONS:
WELDING DEFECTS
PRESENTED BY: HARDISH TRIVEDI
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• LESS INCLUDED ANGLE
• INSUFFICIENT CHIPBACK DEPTH
SLAG INCLUSIONS:
WELDING DEFECTS
• EXCESSIVE WEAVING
• IMPROPER EARTHING / FEED BACK WIRE
CONNECTION• JERKY MOTION OF CIRC. SEAM DUE TO TANK
ROTATOR / DRIFT/ LONG. SEAM REINFORCEMENTPRESENTED BY: HARDISH TRIVEDI
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LOWER CURRENT
WELDING DEFECTS
LACK OF FUSION / PENETRATION
LFLP
• POOR WEP / SET-UP - LOW ROOT GAP,
HIGH ROOT FACE, LOWER INCLUDED ANGLE
• RUST / PAINT ON WEPPRESENTED BY: HARDISH TRIVEDI
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• BEAD SHAPE AND BEAD PLACEMENT
• EXCESSIVE WEAVING
• HIGHER VOLTAGE IN SAW / FCAW
WELDING DEFECTS
LACK OF FUSION / PENETRATION
LFLP
PRESENTED BY: HARDISH TRIVEDI
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GOOD ENGINEERING
PRACTICES
PRESENTED BY: HARDISH TRIVEDI
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IMPORTANT CODE REQUIREMENT AND PRACTICES RELATED TO WELDING
2. Check the seam number on the job.
( A ) BEFORE STARTING WELDING
1. For specific seam : Refer shop weld plan, WPS and test plan.
PRESENTED BY: HARDISH TRIVEDI
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5. Check calibrations of welding machine and carry out trial where required.
CALIBRATIONDUE ON:
31.10.99
E7018
Supercito E 7018
3. Check identification marks of welding consumables.
IMPORTANT CODE REQUIREMENT AND PRACTICES RELATED TO WELDING
4. Process Quantity (max. )SMAW 15 ElectrodesSAW/FCAW 1 Wire SpoolSAW Flux 10 KgESSC Flux 25 Kg
PRESENTED BY: HARDISH TRIVEDI
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6. Check cable connections and earthing.
IMPORTANT CODE REQUIREMENT AND PRACTICES RELATED TO WELDING
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.
PRESENTED BY: HARDISH TRIVEDI
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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 mm away from WEP on both sides.
IMPORTANT CODE REQUIREMENT AND PRACTICES RELATED TO WELDING
PRESENTED BY: HARDISH TRIVEDI
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IMPORTANT CODE REQUIREMENT AND PRACTICES RELATED TO WELDING
2. Weaving < 3 x Electrode diameter.
( B ) WHILE WELDING
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 stray arcing on job.
PRESENTED BY: HARDISH TRIVEDI
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2. Return unused consumable to shop stores.
( C ) AFTER WELDING
1. Welder stamp to be stamped on seams - max. 3 feet apart.
Max. 3 feet
IMPORTANT CODE REQUIREMENT AND PRACTICES RELATED TO WELDING
PRESENTED BY: HARDISH TRIVEDI
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GOOD PRACTICES FOR WELDING
( A ) GENERAL
1. Use correct shade of welding glass.
WRONG RIGHT
2. Keep your head out of welding fumes.
PRESENTED BY: HARDISH TRIVEDI
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3. Do not direct fan air on welding arc .
GOOD PRACTICES FOR WELDING
PRESENTED BY: HARDISH TRIVEDI
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4. When working in confined space ensure adequate ventilation / exhaust.
CONFINED SPACE
BLOWER
WELDING
GOOD PRACTICES FOR WELDING
PRESENTED BY: HARDISH TRIVEDI
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5. Eliminate mix-up of electrode / filler wire / flux.
GOOD PRACTICES FOR WELDING
6
6
140 Gms / mt
8
8
250 Gms / mt
6. Never over weld fillets ---
- 6 CFW to 8 CFW - 78 % extra weld .
- Loss of man hours + consumable
- Distortion.
PRESENTED BY: HARDISH TRIVEDI
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GOOD PRACTICES FOR WELDING
7. Give minimum root gaps for fillet joints - 3 mm gap on 6 CFW increases weld metal by 125 %.
6
6
6
6
125% WELD METAL
PRESENTED BY: HARDISH TRIVEDI
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9. Weld bead restart - end : return arc on crater to fill up the crater and to avoid crater cracks - porosity
- restart ahead of end crater so that end crater gets melted and filled - up.
ENDCRATER CRACK
GOOD PRACTICES FOR WELDING
8. Do not give excessive reinforcements.
PRESENTED BY: HARDISH TRIVEDI
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11. For NG - SAW and ESSC follow instructions from welding Engg.
GOOD PRACTICES FOR WELDING
10. Burn complete electrode - max. stub end should be 50 mm.
E7018
< 50mm
E7018
> 50mm
PRESENTED BY: HARDISH TRIVEDI
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3. End craters of SS, Inconel, Nickel, Monel overlay show crack if current is high, arc length is longer and cleanliness is not maintained. Crater must be filled up.
GOOD PRACTICES FOR WELDING
( B ) WELD OVERLAY
1. Use only specified voltage / current / travel speed to avoid higher dilution.
4. Bead overlap must be minimum 50 %.
2. Higher dilution may result in cracking : weld with correct parameters .
PRESENTED BY: HARDISH TRIVEDI
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5. Minimum bead length per electrode must be achieved.
GOOD PRACTICES FOR WELDING
SS
CS
6. Clad stripping must remove complete SS material, check with
CuSo4 solution.
PRESENTED BY: HARDISH TRIVEDI
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( C ) PIPE # PIPE BUTT JOINTS
1. Set up should be done after cleaning I.D. weld as soon as possible 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.
( D ) NOZZLE # SHELL / D’JOINTS ON THICK VESSELS
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
PRESENTED BY: HARDISH TRIVEDI
57PRESENTED BY: HARDISH TRIVEDI