TWI CSWIP VISUAL INSPECTION OF WELDS
Terminology Butt Joints
Square Edged
Closed
Open Single Sided Butt
Vee
Bevel
Double Sided Butt Bevel Vee
Terminology Fillet Joints
Tee
Lap
Corner
Terminology Included Angle
60-700
0-2 mm 2-4 mm Root Gap
Root Face
Terminology Butt Weld Features
9
7
10
8 2
1 5
4 3 6
Terminology Fillet Weld Features
10 9 4 7 3
2
5
8
1 6
Joint Design Butt Weld
Lap Joint
Corner Joint
Tee Joint Edge Weld
Zones in Fusion Welds • • •
Parent Material or Base Metal Heat Affected Zone Fusion Zone
Visual Inspection Procedures Important things to consider When do I carry out inspections? How do I carry out inspections? What do I look for? What equipment do I need? How do I interpret the code or standard requirements? 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 • • • •
• • • •
Welding Checklist Before Welding Commences • • • • •
Documentation Materials Weld preparations Fit up for welding Welding equipment
Welding Checklist During Welding • • • • • • • •
Correct parameters WPS at the work place Inter run cleanliness and quality Interpass temperature Consumable control Maintenance of preheat Process control NDE regime Weld records and maintenance of weld maps
Welding Checklist Welding Completion Visual inspection and records NDE PWHT Final testing Cleaning, painting, preservation, packing Final documentation
• • • • • •
Features to Consider Butt welds - Size Weld cap width Excess weld metal height
Root penetration Root bead width
Features to Consider Fillet welds - Size Excess weld metal
Minimum and maximum leg length size
Actual throat thickness
Design throat thickness
Features to Consider Importance of Fillet weld leg length Size (a)
(b)
4mm
8mm 6mm
4mm
What size is the Throat thickness of (a) What size is the Throat thickness of (b)
Features to Consider Importance of Fillet weld leg length Size (a)
(b)
4mm
6mm 4mm
6mm
How much bigger is (a) in volume than (b)
Features to Consider (a)
(b)
4mm
6mm 4mm (a) volume = 4 x 4 = 8mm2 2
6mm (b) volume = 6 x 6 = 18mm2 2
The volume of (b) is over double the volume of (a) Without the extra reinforcement being added
Features to Consider Fillet welds - Size & Shape Convex Mitre
Concave
Features to Consider Fillet welds - Toe Blend
Features to Consider EFFECTIVE THROAT THICKNESS “a” = Nominal throat thickness “s” = Effective throat thickness
a
s
Deep throat fillet welds from FCAW & SAW etc
Features to Consider Butt welds - Profile
x x
x
Features to Consider Butt welds - Toe Blend
x x
x
Features to Consider Butt welds - Weld Width
A Weld : Definitions BS 499 •
A union between pieces of metal at faces rendered plastic or liquid by heat,pressure or both.
NASA •
A continuous defect surrounded by parent material
Welds An ideal weld must give a strong bond between materials with the interfaces disappearing To achieve this •
Smooth,flat or matching surfaces
•
Surfaces shall be free from contaminants
•
Metals shall be free from impurities
•
Metals shall have identical crystalline structures
Electric Arc Welding
Electrode Power supply Work piece Clamp(Earth)
Electric Arc Welding •
•
•
•
•
Electric discharge produced between cathode and anode by a potential difference (40 to 60 volts) Discharge ionises air and produces -ve electrons and +ve ions
Electrons impact upon anode, ions upon cathode Impact of particles converts kinetic energy to heat (7000o C) and light Amperage controls number of ions and electrons, Voltage controls their velocity
Manual Metal Arc Welding
•
• •
Shielding provided by decomposition of flux covering Electrode consumable Manual process
Welder controls Arc length Angle of electrode Speed of travel Amperage settings • • • •
Manual Metal Arc Welding POWER SOURCE POWER SOURCE:-
Input 240v (single phase) or 415v ( 2 live phases of 3 phase supply) Output AC (O.C.V. 80v) or DC (O.C.V. 50v) or both. AC for Shop DC for site work as it is SAFER (lower OCV). Also for shop work.. Current adjustment control
TYPES:-
Transformers – AC only Transformer/Rectifiers – AC and DC Petrol or Diesel driven Generators – Site work – DC Inverters – AC and DC
Manual Metal Arc Welding Power control panel
Electrode oven Electrodes Power return cable Safety visor (With dark lens) *
Power source. Transformer/ Rectifier Heated quiver Inverter power source Electrode holder Power cable
Manual Metal Arc (MMA)
Tungsten Inert Gas (TIG) Power control panel
Transformer/ Rectifier
Power return cable
Inverter power source
Torch assemblies
Power control panel
Tungsten electrodes
Power cable Flow-meter
Tungsten Inert Gas (TIG) POWER SOURCE POWER SOURCE 440v 50Hz 3 phase or 240v single phase input
Transformers for AC – aluminium alloys Rectifiers for DC - steels Transformer/rectifier for AC/DC Inverters for AC/DC – more portable - expensive
TORCH
Sizes/types vary depending on current/application
TORCH HOSE
Flexible – may carry current, gas, cooling water.
RETURN LEAD
Note that current actually flows from this lead
INERT GAS SUPPLY (Cylinder & regulator)
Correct type for application.(ar, he, ar/he mixture) Argon/hydrogen for austenitic stainless steel
FLOWMETER (graduated in ltr/min)
To deliver correct gas flow (velocity) depending on welding position and joint configuration.
Tungsten Inert Gas (TIG) TORCH
WELDING LEAD + GAS SUPPLY
NORMALLY DC-VE
ARC
_
OUTPUT 80 OCV MAX
EARTH*
+ RETURN LEAD
*CHECK WITH HSE GUIDANCE NOTE
METERS (OPTIONAL) VARIABLE CURRENT CONTROLLER
THE POWER SOURCE AC/DC CONSTANT CURRENT ARC STRIKING DEVICE
I
V
GAS SUPPLY
I N E R T G A S
Tungsten Inert Gas (TIG) Tungsten housing
Tungsten electrodes
Fitted ceramic shielding cup
Ceramic shield cup
On/Off switch Gas lens Split collet Gas diffuser Spare ceramic shielding cup *
Torch body
Tungsten Inert Gas (TIG)
Metal Inert Gas (MIG) External wire feed unit
Internal wire feed system
Transformer/ Rectifier
Power cable & hose assembly
Power control panel Liner for wire 15kg wire spool Power return cable*
Welding gun assembly
Metal Inert Gas (MIG)
Submerged Arc
Welding Defects Cracks Classified by Shape Longitudinal Transverse Branched Chevron • • • •
Classified by Position HAZ Centreline Crater Fusion zone Parent metal • • • • •
Welding Defects Cracks 4 Crack Types Solidification cracks Hydrogen induced cracks Lamellar tearing Reheat cracks • • • •
Welding Defects Cracks 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 e.g. Crater cracking • •
• • •
Welding Defects Solidification Cracking
Welding Defects Deeper and narrow weld beads are prone to solidification cracking (depth to width ratio over 2:1)
In order to avoid solidification cracking, reduce penetration and increase bead width (depth to width ratio 0,5:1)
Welding Defects Cracks 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 •
• •
• •
Welding Defects Hydrogen Cracking
Welding Defects Hydrogen Cracking
Welding Defects Cracks 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 • • • •
•
Welding Defects Lamellar Tearing
Welding Defects Lamellar Tearing
Restraint High contractional stress Lamellar tear
Welding Defects Lamellar Tearing Grind and infill with ductile weld metal
Re-design weld
Control restraint
For critical work a forged “T” piece may be used Forged “T” Piece
Welding Defects Cracks 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 •
• •
Welding Defects Incomplete root penetration
Causes Too small a root gap Arc too long Wrong polarity Electrode too large for joint preparation Incorrect electrode angle Too fast a speed of travel for current • • • •
• •
Welding Defects a) Excessively thick root face b) Too small a root gap c) Misplaced welds d) Power input too low
e) Arc (heat) input too low
Welding Defects Too large diameter electrode
Smaller (correct) diameter electrode
Lack of sidewall fusion due to arc deflection
Welding Defects Incomplete root Fusion
Causes Too small a root gap Arc too long Wrong polarity Electrode too large for joint preparation Incorrect electrode angle Too fast a speed of travel for current • • • •
• •
Welding Defects Root concavity
Causes Root gap too large Insufficient arc energy Excessive back purge TIG • • •
Welding Defects Excess Root Penetration
Causes Excessive amperage during welding of root Excessive root gap Poor fit up Excessive root grinding Improper welding technique •
• • • •
Welding Defects Root undercut
Causes Root gap too large Excessive arc energy Small or no root face • • •
Welding Defects Cap Undercut
Causes Excessive welding current Welding speed too high Incorrect electrode angle Excessive weave Electrode too large • • • • •
Welding Defects Overlap
Excess weld metal
Welding Defects Lack of fusion
Causes Contaminated weld preparation Amperage too low Amperage too high (welder increases speed of travel) • • •
Welding Defects Incompletely Filled Groove & Lack of Side wall Fusion
• • •
Causes Insufficient weld metal deposited Improper welding technique
Welding Defects Inter run Incompletely Filled Groove
Causes Insufficient weld metal deposited Improper welding technique • •
Welding Defects Gas pores / Porosity
Causes Excessive moisture in flux or preparation Contaminated preparation Low welding current Arc length too long Damaged electrode flux Removal of gas shield • • • • • •
Welding Defects Gas pores / Porosity
Welding Defects Inclusions - Slag
Causes Insufficient cleaning between passes Contaminated weld preparation Welding over irregular profile Incorrect welding speed Arc length too long • • • • •
Welding Defects Inclusions - Slag
Causes Insufficient cleaning between passes Contaminated weld preparation Welding over irregular profile Incorrect welding speed Arc length too long • • • • •
Welding Defects Poor (convex) weld bead profile resulted in pockets of slag being trapped between the weld runs
Smooth weld bead profile allows the slag to be readily removed between runs
Welding Defects Inclusions - Tungsten
Causes Contamination of weld Caused by tungsten touching weld metal or parent metal during welding using the TIG welding process •
Welding Defects Burn Through
Causes Excessive amperage during welding of root Excessive root grinding Improper welding technique • • •
Welding Defects Spatter
Causes Excessive arc energy Excessive arc length Damp electrodes Arc blow • • • •
Welding Defects Arc Strikes Causes •
•
•
Electrode straying onto parent metal Electrode holder with poor insulation
Poor contact of earth clamp
Welding Defects Mechanical Damage Chisel Marks Chisel Marks
Pitting Corrosion
Grinding Marks
Welding Defects Non-alignment of two abutting edges
EXAMPLE PLATE REPORT
Page 1 of 3
Name: [Block capitals] Mr. I C Plenty Code/Specification used: TWI 09-09-03 Welding position: Flat /PA M E A S U R E
D A T U M E D G E
I C Plenty
Welding process:
Test piece ident:
A
Date
Length & thickness of plate: 300mm x 10 mm
B
Lack of sidewall fusion
22/08/2003
87
51
Slag inclusion NOTES:
230
22
153
8
C
Gas pore 1.5 Ø
Undercut smooth 1.5 max 236 30
40 Arc Strike
Centreline crack
001
Joint type: Single V Butt
MMA/SMAW
WELD FACE
F R O M T H I S
Signature:
241
Cap height : 4mm. Weld width: 12-14mm Toe blend: Poor Misalignment: 2mm Angular Distortion 3mm in 50mm Spatter along weld length or scale on the plate surface
EXAMPLE PLATE REPORT
Page 2 of 3
M E A S U R E F R O M
WELD ROOT A
Root concavity 2 deep 23
E D G E
247
128
50
Incomplete root penetration NOTES: Penetration height : Linear Misalignment: Angular Distortion: Any scale on plate surface
C
LACK OF ROOT FUSION
10
T H I S D A T U M
B
4mm. 2mm 3mm in 50mm
20
EXAMPLE WELD INSPECTION REPORT/SENTENCE SHEET PRINT FULL NAME
I C Plenty 001
SPECIMEN NUMBER EXTERNAL DEFECTS
Defect Type
Defects Noted
Pipe/Plate Section 1
Code or Specification Reference
Accumulative Total 2
Maximum Allowance 3
Section/ Table No 4
Accept/Reject 5
Excess weld metal height
AC
4mm
3mm
15
Reject
Excess weld metal appearance
A-C
Poor blend
Smooth
19
Reject
Incomplete filling
A-C
22mm
None
8
Reject
Inadequate weld width
A-C
NONE
------------
----------
Accept
Slag Inclusions
A-C
1x 8mm long
2mm
3
Reject
Undercut
A-C
1.5mm depth
1mm
11
Reject
Surface Porosity
A-C
1.5mm
1mm
2
Reject
Cracks/Crack-like defects
A-C
40mm
NONE
1
Reject*
Lack of fusion
A-C
22mm
NONE
5
Reject
A-C
30x25
------------
12
Mechanical damage
A-C
NONE
------------
----------
Accept
Laps/Laminations
A-C
NONE
------------
----------
Accept
Misalignment (Linear)
A-C
2mm
2mm
9
Accept
Longitudinal seams
A-C
NONE
------------
----------
Accept
Arc strikes
Seek advise***
Root Defects Misalignment
A-C
2mm
2mm
9
Accept
Excessive Root Penetration
A-C
4mm
2mm
16
Reject
Incomplete Root Penetration
A-C
50mm
NONE
6
Reject
Lack of Root Fusion
A-C
20mm
NONE
5
Reject
Root Concavity
A-C
2mm depth
1mm
20
Reject
Root Undercut
A-C
NONE
------------
----------
Accept
Cracks/Crack-like defects
A-C
NONE
------------
----------
Accept
Slag inclusions
A-C
NONE
------------
----------
Accept
Porosity
A-C
NONE
------------
----------
Accept
Laps/Laminations
A-C
NONE
------------
----------
Accept
TWI 09-09-03 This *pipe/plate has been examined to the requirements of code/specification ......................................... and is accepted/rejected accordingly. Comments: * Request MPI testing to confirm crack and length. ** Large amount of spatter on weld face. Recommend this is removed and re inspected. *** Recommend arc strikes are ground flush prior to MPI testing for crack detection.
I C Plenty
Signature......................................................... *Delete which is not applicable.
22nd August 2003
Date..................................................................................... Use the other side for any comments.
Inspection Practice Specification Number TWI 09-09-03 All dimensions are given in mm No
Imperfection
Comments
Allowance
1
Cracks
Confirm with penetrant testing
Not permitted
2
Porosity
Individual pore Ø
Maximum 1mm
3
Solid Inclusions
Non metallic. Individual size
Maximum 1mm
4
Solid Inclusions
Metallic. Individual size
Not permitted
5
Lack of Fusion
Side wall/Root/Inter-run
Not permitted
6
Incomplete Root Penetration
7
Overlap/Cold lap
8
Incompletely filled groove
Not permitted
9
Linear Misalignment
0.2t Maximum 4mm
10
Angular Misalignment
Maximum 10º
11
Undercut
Smoothly blended
10%t Maximum d 1mm
12
Arc Strikes
Area to be tested by MPI
Seek advice
13
Laminations
Not permitted
14
Mechanical Damage
Not permitted
15
Cap Height
16
Penetration Bead
0 –2mm h Maximum
17
Toe Blend
Smooth
18
Spatter
Clean & Re-inspect
Refer to manufacturer
19
Weld Appearance
All runs shall blend smoothly
Regular
20
Root concavity
Not permitted Weld face/Root
Shall fall below plate surface
Not permitted
0 –3mm h Maximum
10%t Maximum
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: Visual Inspection of Welds Using the Cambridge Multi-Purpose Welding Gauge:
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: Angle of preparation: preparation: This scale reads from 00 to 600 in steps of 50. The angle is read against the chamfered edge of the plate or pipe.
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: L inea inearr Mis Misa ali lignm gnme ent nt:: The gauge may be used to measure misalignment of members by placing the edge of the gauge on the lower member and rotating the segment until the pointed finger contacts the higher member.
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: Excess Weld Metal/Root penetration: The scale is used to measure excess weld metal or root penetration, by placing the edge of the gauge on the plate and rotating the segment until the pointed finger contacts the excess weld metal or root bead at its highest point.
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: Undercut / mechanical damage (grinding etc) The gauge may be used to measure the depth of undercut by placing the edge of the gauge on the plate and rotating the segment until the pointed finger contacts the lowest depth of the undercut. The reading is taken on the scale to the left of the zero mark in mm or inches.
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: Fillet Weld Actual Throat Thickness: The small sliding pointer reads up to 20mm, or ¾ inch. When checking the throat you measure the actual throat thickness also note! that there is a „nominal‟ design throat thickness,
TWI CAMBRIDGE MULTI-PURPOSE WELDING GAUGE: Fillet Weld Leg Length: The gauge may be used to measure fillet weld leg lengths of up to 25mm, as shown on left.
TWI CSWIP 3.0 INSPECTION OF FILLET WELDS
Fillet Weld Inspection CSWIP 3.0 Fillet Welded T Joint
F 123
Part of the CSWIP 3.0 examination is to inspect & assess a Fillet welded Tee for it’s size & visual
acceptance to the applicable code.
Fillet Weld Inspection 1. The plate reference number must be recorded in the top left hand corner of the report sheet, then the thickness of the plate must be measured and entered in the top right hand corner of the report sheet in the boxes provided. Specimen Number F123
Material thickness: 6mm
Fillet Weld Inspection 2)
Both the Vertical and Horizontal fillet weld leg lengths must be measured to find the minimum and maximum size‟s. These values are entered in the boxes provided on the report sheet. Use the gauge as shown below:
Fillet Weld Leg Length: The gauge may be used to measure fillet weld leg lengths up to a maximum of 25mm, as shown on left.
Fillet Weld Inspection 3) The minimum and maximum throat thickness are measured and entered in the boxes provided on the report sheet. These values are measured as shown below: Fillet Weld Throat Thickness: The small sliding pointer reads up to 20mm, or ¾ inch. When measuring the throat it is supposed that the fillet weld has a nominal throat thickness, as an effective throat thickness cannot be measured in this manner.
Fillet Weld Inspection Having made all the above measurements they can be assessed to a set of values that may be simply calculated from the plate thickness. a) The minimum leg length size is the plate thickness b) The maximum leg length size is: The plate thickness + 3mm c) The minimum throat thickness is: The plate thickness x 0.7 d) The maximum throat thickness is: The plate thickness + 0.5mm
Fillet Weld Inspection For example if the plate thickness is 6mm then the following will apply:
6mm
F 123
a) The minimum leg length size is 6mm (Plate thickness) b) The maximum leg length size is 9mm (Plate thickness + 3mm) c) The minimum throat thickness is 4.2mm (Plate thickness x 0.7) d) The maximum throat thickness is 6.5mm (Plate thickness + 0.5mm
Fillet Weld Inspection This means that the measurements taken must fall inside BOTH the tolerances calculated i.e. Leg lengths must be between 6mm – 9mm Throat thickness must be between 4.2 and 6.5mm If all the values are within these tolerances they are acceptable. If any of the values fall outside of the calculated tolerances then it becomes unacceptable. It is important to remember that any change in thickness will change the acceptance values calculated above.
Fillet Weld Inspection Vertical Leg Length Lowest leg measurement 7mm Highest leg measurement 8mm Actual Throat Thickness Lowest throat measurement 4.5mm Highest throat measurement 8mm Horizontal Leg Length Lowest leg measurement 5mm Highest leg measurement 10mm
Fillet Weld Inspection Practical Exam Report Sheet Specimen Number F123
Material thickness: 6mm
1) Measure and record the following details: VERTICAL LEG LENGTH (Max & Min)
= Max 8mm
HORIZONTAL LEG LENGTH (Max & Min)
= Max 10mm Min 5mm
DESIGN THROAT THICKNESS (Max & Min) = Max 8mm
Min 7mm
Min 4.5mm
Fillet Weld Inspection 2) Sentence the fillet weld dimensions using the following design criteria: MINIMUM LEG LENGTH: Material thickness (6mm) MAXIMUM LEG LENGTH: Material thickness + 3mm (9 mm) MINIMUM THROAT THICKNESS: Material thickness x 0.7 (4.2 mm) MAXIMUM THROAT THICKNESS: Material thickness + 0.5mm (6.5 mm)
The VERTICAL LEG LENGTH Please state: ACCEPT
ACCEPT or REJECT?
The HORIZONTAL LEG LENGTH Please state: REJECT
ACCEPT or REJECT?
The THROAT THICKNESS Please state: REJECT
ACCEPT or REJECT?
Fillet Weld Inspection Having assessed the weld for its size an inspection can then be made on the surface to locate any imperfections. Firstly; the report sheet requests the inspector to indicate the number of locations that the following imperfections occur, if any? 3) The number of places that they occur should now be entered in the box as follows: UNDERCUT APPEAR? OVERLAP APPEAR? LACK OF FUSION APPEAR? CRACKS APPEAR? POROSITY APPEAR? SOLID INCULSIONS? MISC: [ARC STRIKES etc]
3 places None None None 2 Areas 1 Slag Inclusion Spatter
Fillet Weld Inspection 4) For the defects recorded state: MAXIMUM length (and DEPTH if applicable) of each defect UNDERCUT:
Length: 15 mm Depth: Smooth 1.0mm
OVERLAP:
Length: -------- Depth: ---------
LACK OF FUSION:
Length: -------- Depth: ---------
CRACKS:
Length: -------- Depth: ---------
POROSITY:
Length: 6mm
Depth: Maximum Ø
SOLID INCLUSIONS:
Length: 4mm
Depth: ---------
MISC:[ ARC STRIKES]
Length: Spatter Depth: ---------
Fillet Weld Inspection 5) Then, assess the levels of imperfections allowed by the applicable code which is provided: UNDERCUT: ACCEPT OVERLAP: ACCEPT LACK OF FUSION: ACCEPT CRACKS: ACCEPT POROSITY: REJECT SOLID INCLUSION: REJECT MISC: [ARC STRIKES] REJECT*
(Accept or Reject?) (Accept or Reject?) (Accept or Reject?) (Accept or Reject?) (Accept or Reject?) (Accept or Reject?) (Accept or Reject?)
* All spatters should have been removed prior to submission for inspection
