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Visual Inspection of Welds:Visual Inspection of Welds: The The Key to Successful Quality Assurance Key to Successful Quality Assurance
ProgramProgram
Presented By:Presented By:
Usman Basha Usman Basha Sr. Mech Inspector, YPIUSr. Mech Inspector, YPIU
September 16, 2003September 16, 2003
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Flow of PresentationFlow of Presentation Importance of Visual welding InspectionImportance of Visual welding Inspection
Welding ProcessesWelding Processes
Welding DefectsWelding Defects
Welding inspection ToolsWelding inspection Tools
ConclusionsConclusions
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Visual InspectionVisual Inspection• Visual examination can be an invaluable tool.
• Excellent process control technique to help identify welder’s problems.
• Visual examination is a method for identifying surface flaws and imperfections.
• Quality control program
• It has been shown that a conscientious program of visual inspection occurring before, during, and after welding can result in discovery of the majority of all defects.
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Prior to WeldingPrior to WeldingPrior to welding, some typical action items requiring attention by the visual inspector include:
1. Review drawings and specifications.
2. Check qualification of welders to be utilized.
3. Review materials and Equipment to be utilized.
4. Check fit-up and alignment of weld joints.
5. Check preheat, if required.
6. Check for calibration of power supplies of welding machines
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Joint Fit-UpJoint Fit-Up
Items that may be considered prior to welding include:
1. Grove angle
2. Root openings
3. Joint alignment
4. Backing
5. Consumable insert
6. Joint cleanliness
7. Tack welds
8. Preheat & Stress
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During WeldingDuring Welding Check amperage, voltage, polarity.Check amperage, voltage, polarity.
Ensure correct welding technique.Ensure correct welding technique.
Ensure correct welding direction.Ensure correct welding direction.
Check welding time.Check welding time.
Ensure adequate cleaning between passes.Ensure adequate cleaning between passes.
Correct interpass temperature.Correct interpass temperature.
Check root internally.Check root internally.
Check all back gouged welds.Check all back gouged welds.
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After WeldingAfter Welding
1. Final weld appearance,cleaning, arc strikes
2. Final weld size
3. Weld length
4. Dimensional accuracy
5. Amount of distortion, PWHT, NDT
The basic purpose of final weld inspection is to assure the weld’s quality.
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Welding ProcessesWelding Processes
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Shielded Metal Arc WeldingShielded Metal Arc Welding
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Tungsten Arc WeldingTungsten Arc Welding
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Gas Metal Arc WeldingGas Metal Arc Welding
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Submerged Arc WeldingSubmerged Arc Welding
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Discontinuities.Discontinuities.Typical discontinuities found in welds are:
While code requirements may permit limited amounts of some of these discontinuities, cracks, and incomplete fusion defects are never allowed.
1. Porosity
2. Incomplete fusion
3. Incomplete penetration
4. Undercut
5. Overlap
6. Cracks
7. Slag inclusions
8. Excessive reinforcement
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Problems Associated With Problems Associated With Incorrect Weld Joint Fit UpIncorrect Weld Joint Fit Up
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Root ProblemsRoot Problems
Gap size too large:
b) burn-througha) excess penetration
c) shrinkage grooves d) gas entrapment
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Root ProblemsRoot Problems
Gap size too small:
1) incomplete penetration
2) incomplete root fusion 3) incomplete side wall fusion
4) slag inclusions 5) root concavity
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Root ProblemsRoot Problems
Root face too large:
a) incomplete root penetration b) incomplete root fusion
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Root ProblemsRoot Problems
Root face too small:
1) excessive penetration 2) burnthrough
3) root concavity 4) root undercut
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Included Angle Too largeIncluded Angle Too large
a) excess penetration b) incomplete filled groove
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Fillet WeldsFillet Welds
Gap size too large:
1) reduced root penetration 2) slag inclusions
3) gas inclusions
4) reduced vertical leg length size
5) cracking
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Included Angle Too SmallIncluded Angle Too Small
1) incomplete root penetration
2) incomplete interun fusion
3) incomplete root fusion
4) incomplete sidewall fusion
5) excessive cap
6) poor toe blend
7) slag inclusions
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Discontinuities - CracksDiscontinuities - CracksHot Cracks - develop at/near Solidification
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Cracks.Cracks.
Cracks form in the weld and base metal when localized stresses exceed the ultimate strength of the material.
Cracks can be classified as either hot cracks or cold cracks.
Cracking associated with hydrogen embrittlement, commonly referred to as “delayed cracking.” Is a form of cold cracking. Hot cracks propagate along grain boundaries. Cold cracks propagate both along grain boundaries and through grains.
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Cracks.Cracks.
• ROOT CRACKS• THROAT CRACKS• TOE CRACKS• UNDERBEAD AND HAZ CRACKS• CRATER CRACKS
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Discontinuities - FusionDiscontinuities - Fusion
Molten weld metal running over un-melted base metal
Faulty electrode manipulation
Overlap - weld metal rollover
Incomplete fusion caused by:
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UndercutUndercutUndercut creates a transition which should be evaluated for a reduction in cross section, and for stress concentrations or notch effect which fatigue is a consideration
Overlap Overlap is the protrusion of weld metal beyond the weld toe, or weld root.
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Discontinuities - PenetrationDiscontinuities - Penetration
Procedure / preparation conflict
Inept welding shop supervision
Failure to penetrate to joint root caused by improper procedure:
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Discontinuities - WeldingDiscontinuities - Welding
Unsuitable welding parameters
Inappropriate arc manipulation
Usually no major significance but detracts from appearance and it affects coating.
Spatter:
Live part of welding circuit makes accidental job contact
Corrective action required
Arc Strike:
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Discontinuities - InclusionsDiscontinuities - Inclusions
Non-metallic
Slag
Oxide
Solid inclusions: Metallic
Tungsten
Copper
Foreign bodies
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Using Welding Inspection Using Welding Inspection ToolsTools
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Measurements of Welding -Measurements of Welding -Fillet WeldsFillet Welds
Most used
Weld strength - ‘Effective Throat’
Weld cost - function of weld size
Fillet welds:
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Fillet Weld Gage.Fillet Weld Gage.
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Throat Thickness Throat Thickness
Fillet Weld
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Weld Profile GaugeWeld Profile Gauge
Measuring
Fillet Welds
Measuring Bevel Angle
Measuring Cap Reinforcement/ Misalignment
Scale in inches or mm
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Hi Lo Gage Hi Lo Gage
Measures Hi Lo… Pipe Thickness… Bevel Angle…
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Cap ReinforcementCap Reinforcement
Measuring the height of the cap
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Bevel AngleBevel Angle
Measuring the pipe bevel angle
Readout
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MisalignmentMisalignment
Shown on scale
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Misalignment (Hi Lo)Misalignment (Hi Lo)Pipe Misalignment
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AnyQuestionsQuestions
?
Thank You!Thank You!