6. Types of Joint Preparation
Included angle
Root Gap
Root Face
Angle of
bevel
Root Face
Root Gap
Included angle
Root
Radius
Single -V Butt Single - U Butt
TWI
7. Types of Joint Preparation
Root Gap
Root Face Root Face
Root Gap
Root
Radius
Single Bevel Butt Single J Butt
Angle of
bevel
Angle of
bevel
Land
TWI
13. Welding Positions
Flat position
UK (USA) 1G rotated
ISO/EN PA
UK (USA): 1G
ISO/EN: PA
UK (USA) 2G Fixed
ISO/EN PC
UK (USA): 2G
ISO/EN: PC
vertical
position
TWI
14. Welding Positions
Vertical
down
UK (USA) 3G
ISO/EN PG
UK (USA) 3G
ISO/EN PF
Vertical
up
UK (USA) 4G
ISO/EN PE
Overhead Position
UK (USA) 5G
ISO/EN PF, PG
Vertical Position
Pipe fixed Horizontal
TWI
18. Visual Inspection Procedures
• What is the nature of the product?
• What operating conditions will be
present?
• What is the quality of welding required?
• Is there a code or standard available to
inspect the welds to?
21. Duties of a Welding Inspector
Before Welding.
before assembly.
after assembly.
During welding.
After welding.
TWI
22. Welding Checklist
• Familirization to the relevant code and specification
• Check welding equipment and calibration certificates
• Material identification,size,type and condition
• Consumables type,size,condition,storage and handling
• Review/witness WPS and PQR test and record
• Joint preparation( check)
• Welder qualification test( Review/witness)
• Welding process involved
• Check pre-heating before welding ( if required)
Before Welding Commences
23. Welding Checklist
• Check weather condition
• Check clearance for welding/welder
• Check welder identification for weld
• Check consumables as per WPS used
• Check welding parameters as per WPS used
• Check distortion control
• Check interpass cleaning
• Check run out length ( travel speed)
• Check interpass temperature
• Check usage of line up clamps
• Maintain daily log book
During Welding
24. Welding Checklist
• Perform visual inspection
• Weld and welder identification ( check)
• Post weld heat treatment ( if required)
• Non-destructive Testing ( witness)
• Acceptance standards of NDT
• Repairs (if any)
• Dimensional check ( as per drawing)
• Document control - welding reports etc
Welding Completion
25. Welding Checklist
• Authorization for repair
• Removal and preparation for repair
• Testing of repair - visual and NDT
In the event of repair
26. How Do I Carry Out a Visual
Inspection?
• What is the nature of the product?
• What operating conditions will be
present?
• What is the quality of welding required?
• Is there a code or standard available to
inspect the welds against
27. Features to Consider
Butt welds - Size
Excess weld
metal height
Root penetration
Root bead width
Weld cap width
28. Features to Consider
Fillet welds - Size
Minimum and
maximum leg
length size
Minimum design
throat thickness
34. Weld Defects
Defects which may be detected by visual
inspection can be grouped under five headings
Cracks
Surface irregularities
Contour defects
Root defects
Miscellaneous
TWI
35. Weld Defects
Other associated defects
Cavities
Solid inclusions
Set up irregularities
Parent material defects
TWI
39. Welding Defects
Solidification
• Occurs during weld solidification process
• Steels with high sulphur content (low
ductility at elevated temperature)
• Requires high tensile stress
• Occur longitudinally down centre of weld
• eg Crater cracking
Cracks
40. Welding Defects
Hydrogen Induced
• Requires susceptible grain structure, stress
and hydrogen
• Hydrogen enters via welding arc
• Hydrogen source - atmosphere or
contamination of preparation or electrode
• Moisture diffuses out into parent metal on
cooling
• Most likely in HAZ
Cracks
41. Welding Defects
Lamellar Tearing
• Step like appearance
• Occurs in parent material or HAZ
• Only in rolled direction of the parent material
• Associated with restrained joints subjected to
through thickness stresses on corners, tees
and fillets
• Requires high sulphur or non-metallic
inclusions
Cracks
42. Welding Defects
Re-Heat Cracking
• Occurs mainly in HAZ of low alloy steels
during post weld heat treatment or service at
elevated temperatures
• Occurs in areas of high stress and existing
defects
• Prevented by toe grinding, elimination of poor
profile material selection and controlled post
weld heat treatment
Cracks
44. Undercut
An irregular groove at the toe of a weld run in
the parent metal
Excessive amps/volts
Excessive travel speed
Incorrect electrode angle
Excessive weaving
Incorrect welding technique
Electrode too large
TWI
45. Overlap
An imperfection at the toe or root of a weld caused by
metal flowing on to the surface of the parent metal
without fusing to it
Contamination
Slow travel speed
Incorrect welding
technique
Current too high
TWI
46. Crater Pipe
Depression at the end of a weld that has a insufficient
cross section.
Too fast a cooling rate
Deoxidization
reactions and liquid to
solid volume change
Contamination
TWI
Crater crack
47. Contour Defects
Incomplete filled groove Poor cap profile
Excessive cap height
TWI
Incomplete filled groove
+ Lack of sidewall fusion
48. Root Defects
Incomplete root fusion
Incomplete root penetration
Low Amps/volts
Large Root face
Small Root Gap
Fast Travel Speed
Incorrect Electrode
Angle
Contamination
TWI
49. Concave root
Root Defects
TWI
Root faces too large
Root gap too large
Excessive back purge
pressure during TIG welding
Excessive root bead grinding
before the application of the
second pass
A shallow groove, which may occur in the root of a butt weld
50. Shrinkage groove
Root Defects
TWI
Insufficient weld metal
deposited in the root
pass
Too fast a cooling rate
during the application of
the root bead pass
Poor welding technique
A shallow groove caused by contraction in the weld
metal along each side of the penetration bead
51. Root Defects
Burn through
High Amps/volts
Small Root face
Large Root Gap
Slow Travel Speed
TWI
A localized collapse of the weld pool due to excessive
penetration resulting in a hole in the root run
52. Miscellaneous Defects
Arc strike
Accidental striking of
the arc onto the parent
material
Faulty electrode holder
Poor cable insulation
Poor return lead
clamping
TWI
53. Spatter
Excessive current
Damp electrodes
Contamination
Incorrect wire feed
speed when welding
with the MAG welding
process
TWI
Miscellaneous Defects
54. TWI
Gas Cavities
Cluster porosity
Gas pore
Blow hole
Herringbone porosity
Root piping
Loss of gas shield
Damp electrodes
Contamination
Arc length too large
Damaged electrode flux
Moisture on parent
material
Welding current to low
55. TWI
Solid Inclusions
Slag originates from welding
flux
MAG and TIG welding
process produce silica
inclusions
Slag is caused by
inadequate cleaning
Other inclusions include
tungsten and copper
inclusions from the TIG and
MAG welding process
Lack of sidewall
fusion with
associated slag
Slag inclusions
Parallel slag lines
Slag inclusions are defined as a non-metallic inclusion
caused by some welding process
57. TWI
Parent Material Defects
A welding inspector should also inspect the parent
material for any visible defects
Lamination
Mechanical damage Lap
Segregation line
