1

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

2

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

3

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.

4

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

5

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

6

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.

7

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.

8

Welding ProcessesWelding Processes

9

Shielded Metal Arc WeldingShielded Metal Arc Welding

10

Tungsten Arc WeldingTungsten Arc Welding

11

Gas Metal Arc WeldingGas Metal Arc Welding

12

Submerged Arc WeldingSubmerged Arc Welding

13

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

14

Problems Associated With Problems Associated With Incorrect Weld Joint Fit UpIncorrect Weld Joint Fit Up

15

Root ProblemsRoot Problems

Gap size too large:

b) burn-througha) excess penetration

c) shrinkage grooves d) gas entrapment

16

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

17

Root ProblemsRoot Problems

Root face too large:

a) incomplete root penetration b) incomplete root fusion

18

Root ProblemsRoot Problems

Root face too small:

1) excessive penetration 2) burnthrough

3) root concavity 4) root undercut

19

Included Angle Too largeIncluded Angle Too large

a) excess penetration b) incomplete filled groove

20

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

21

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

22

Discontinuities - CracksDiscontinuities - CracksHot Cracks - develop at/near Solidification

23

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.

24

Cracks.Cracks.

• ROOT CRACKS• THROAT CRACKS• TOE CRACKS• UNDERBEAD AND HAZ CRACKS• CRATER CRACKS

25

Discontinuities - FusionDiscontinuities - Fusion

Molten weld metal running over un-melted base metal

Faulty electrode manipulation

Overlap - weld metal rollover

Incomplete fusion caused by:

26

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.

27

Discontinuities - PenetrationDiscontinuities - Penetration

Procedure / preparation conflict

Inept welding shop supervision

Failure to penetrate to joint root caused by improper procedure:

28

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:

29

Discontinuities - InclusionsDiscontinuities - Inclusions

Non-metallic

Slag

Oxide

Solid inclusions: Metallic

Tungsten

Copper

Foreign bodies

30

Using Welding Inspection Using Welding Inspection ToolsTools

31

Measurements of Welding -Measurements of Welding -Fillet WeldsFillet Welds

Most used

Weld strength - ‘Effective Throat’

Weld cost - function of weld size

Fillet welds:

32

Fillet Weld Gage.Fillet Weld Gage.

33

Throat Thickness Throat Thickness

Fillet Weld

34

Weld Profile GaugeWeld Profile Gauge

Measuring

Fillet Welds

Measuring Bevel Angle

Measuring Cap Reinforcement/ Misalignment

Scale in inches or mm

35

Hi Lo Gage Hi Lo Gage

Measures Hi Lo… Pipe Thickness… Bevel Angle…

36

Cap ReinforcementCap Reinforcement

Measuring the height of the cap

37

Bevel AngleBevel Angle

Measuring the pipe bevel angle

Readout

38

MisalignmentMisalignment

Shown on scale

39

Misalignment (Hi Lo)Misalignment (Hi Lo)Pipe Misalignment

40

AnyQuestionsQuestions

?

Thank You!Thank You!