Weld Inspection 11

No Slide TitleBS EN 17637 Non-destructive examination of fusion welds - Visual examination
Welding Inspection Personnel
should be familiar with relevant standards, rules and specifications applicable to the fabrication work to be undertaken
should be informed about the welding procedures to be used
have good vision (should be checked every 12 months)
Important Qualities Inspectors Should Have
high integrity
good general fitness
Illumination
350 lux minimum required
(recommends 500 lux - equivalent to normal shop floor or office lighting)
Access
eye should be within 600mm of the surface
viewing angle (line from eye to surface) to be not less than 30°
30°
600mm
When Access is Restricted
a mirrored boroscope or fibre optic viewing system may be used
(usually by agreement between fabricator & Client)
Other aids to Inspection
(for checking bevel angles, weld profile, fillet sizing, undercut depth)
gauges to measure weld-gap and linear misalignment (high-low)
straight edges and measuring tapes
a magnifying lens
(if magnification lens used it should have magnification between X2 to X5)
Aids to Visual Inspection (to BS EN 970)
Copyright © 2005, TWI Ltd
Stages of Visual Inspection (to BS EN 970)
How much inspection, and when it is required, should be specified by the Application Standard (Code) or be agreed between the contracting parties
It is normal practice to visually inspect the finished weld for all classes of work
For high integrity fabrications, a Welding Inspector will usually have inspection duties throughout the whole of the fabrication process, namely: -
before welding (preparation & checking materials etc)
during welding (checking welding parameters etc)
after welding (visual inspection etc)
The sort of inspection duties that a Welding Inspector may have when working on high integrity fabrications are considered to be: -
‘The Duties of the Welding Inspector’
manipulation of electrode to ensure sidewall fusion
Bevel Angle
allow controlled root fusion
Too small = burn-through
Root Gap
Terminology & Typical Dimensions: V-Joints
for mechanised GMAW of pipework
for MMA welding of pipe joints > ~20mm (compound bevel)
12 to 15°
1 = excess weld metal
10 = cap profile or contour
convex fillet
concave fillet
The fillet weld shape that may not satisfy design requirements
Leg length = 1.4 x throat thickness (Z = 1.4 x a)
Throat thickness = O.7 x leg length (a = 0.7 x Z)
Z
Z
a
Weld Imperfections
lack of root fusion on one, or both sides, of the root
Lack of Fusion
welding current too low
bevel angle too small
incorrect electrode angle
‘flooding’ the joint with too much weld metal
incomplete penetration or lack of cross-penetration
Note: may be called lack of root fusion
actual penetration
root gap too small
welding speed too high
root undercut (may also be called shrinkage grooves)
inter-run undercut - in weld metal
most common at vertical toe of fillet welds
burn-through (excessive melt through)

angle is >> 90° - the normal aim to give a good/smooth ‘toe blend’

angle is relatively small (close to 90°) and gives a poor/sharp ‘toe blend’
Typical Causes of Imperfect Shape (including poor toe blend)
Poor welding technique is the usual cause these imperfections - such as: -
electrode size for the cap passes is too large
welding speed too slow
poor manipulation of the electrode
incorrect weld bead positioning / placement
Weld Imperfections
Incomplete Filling
associated with no fusion of the sidewall at the weld surface & often referred to as ‘missed edges’
edges not fused
localised incomplete filling
current too high - overhead welding
welding speed too slow - overhead welding
welding current too high for 2nd pass
back-purge pressure too high - for TIG welding
Weld Imperfections
Other imperfections associated with fabricated components
Arc strike or stray arc - accidental striking of an arc on to base material
- loss of welding cable insulation
- poor connection of ’current return’ cable
Spatter - excessive current or voltage
Slag residue - poor workmanship (inadequate cleaning)
Grinding mark / mechanical damage

Weld Inspection 11

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