6. welding symbols & weld preparations

Copyright © 2004, TWI Ltd World Centre for Materials Joining TechnologyWorld Centre for Materials Joining Technology

TWICSWIP 3.1

WIS 5 WELDING INSPECTION

WELDING SYMBOLS AND WELD PREPARATION

TWICSWIP 3.1

WIS 5 WELDING INSPECTION

WELDING SYMBOLS AND WELD PREPARATION


Joints may be indicated:Joints may be indicated:

- by detailed sketches, showing every - by detailed sketches, showing every dimensiondimension

- by symbolic - by symbolic representationrepresentation

Weld symbols on drawingsWeld symbols on drawings


A method of transferring information from A method of transferring information from the design office to the workshop is:the design office to the workshop is:

The above information does not tell us much The above information does not tell us much about the wishes of the designer. We obviously about the wishes of the designer. We obviously need some sort of code which would be need some sort of code which would be understood by everyone.understood by everyone.Most countries have their own standards for Most countries have their own standards for symbols. symbols.

Some of them are BS 499 Part 2, AWS A2.4 &Some of them are BS 499 Part 2, AWS A2.4 &

BS EN 22553 (ISO 2553)BS EN 22553 (ISO 2553)

Please weld Please weld herehere



Advantages of symbolic representation:Advantages of symbolic representation:

Weld symbols on drawingsWeld symbols on drawingsWeld symbols on drawingsWeld symbols on drawings

Disadvantages of symbolic representation:Disadvantages of symbolic representation:

• simple and quick plotting on the drawingsimple and quick plotting on the drawing• does not over-burden the drawingdoes not over-burden the drawing• no need for additional viewno need for additional view• gives all necessary indications regarding gives all necessary indications regarding

the specific joint to be obtained the specific joint to be obtained

• used only for usual jointsused only for usual joints• requires training for properly requires training for properly

understanding of symbolsunderstanding of symbols


Usually, the symbolic representation Usually, the symbolic representation includes: includes:

Weld symbols on drawingsWeld symbols on drawingsWeld symbols on drawingsWeld symbols on drawings

The elementary symbol may be The elementary symbol may be completed by: completed by:

• an arrow linean arrow line• a reference linea reference line• an elementary symbol an elementary symbol

• a supplementary symbola supplementary symbol• a means of showing dimensionsa means of showing dimensions• some complementary indications some complementary indications


Weld elementary symbolsWeld elementary symbols

Various categories of joints are Various categories of joints are characterised by an elementary symbol.characterised by an elementary symbol.

This symbol is similar to the shape of the This symbol is similar to the shape of the weld to be made.weld to be made.

Square butt weldSquare butt weld

Weld typeWeld type SketchSketch SymbolSymbol

Single V butt weldSingle V butt weld



Single-V butt Single-V butt weld with broad weld with broad root faceroot face


Single bevel Single bevel butt weldbutt weld

Single bevel Single bevel butt weld with butt weld with broad root facebroad root face

Backing runBacking run



Single-USingle-U

butt weld butt weld


Single-JSingle-J

butt weldbutt weld

Fillet weldFillet weld

SurfacingSurfacing


Convention of the arrow line (BS EN & Convention of the arrow line (BS EN & AWS):AWS):

Arrow line

a) a) ShallShall touch the joint intersection touch the joint intersection

b)b) ShallShall not be parallel to the drawing not be parallel to the drawing

c)c) ShallShall point towards a single plate point towards a single plate preparation (when only one plate has preparation (when only one plate has preparation)preparation)


Convention of the reference line AWS Convention of the reference line AWS A 2.4 A 2.4

Reference line

a) a) ShallShall touch the arrow line touch the arrow line

b) b) ShallShall be parallel to the bottom of the be parallel to the bottom of the drawingdrawing


Convention of the reference Convention of the reference line (BS EN ISO 22553):line (BS EN ISO 22553):

oorr

Reference line

a) a) ShallShall touch the arrow line touch the arrow line

b)b) ShallShall be parallel to the bottom of the be parallel to the bottom of the drawingdrawing

c)c) There shallThere shall be a further broken line be a further broken line above or beneath the reference line (Not above or beneath the reference line (Not necessary where the weld is symmetrical!)necessary where the weld is symmetrical!)


Welds “Welds “on arrow side”on arrow side” of joint go of joint go underneathunderneath the reference line while the reference line while welds “welds “the other side”the other side” of the joint, go of the joint, go on topon top of the reference line of the reference line

Symbols with a Symbols with a vertical linevertical line component must be component must be drawn with the vertical line to the drawn with the vertical line to the left sideleft side of of the symbolthe symbol

All All CSACSA dimensions are shown to the dimensions are shown to the leftleft of the of the symbolsymbol

All All linear linear dimensions are shown on the dimensions are shown on the rightright of of the symbol i.e. number of welds, length of the symbol i.e. number of welds, length of welds, length of any spaceswelds, length of any spaces

Included angle and root opening are shown on Included angle and root opening are shown on toptop of the symbol of the symbol

AWS A 2.4 rules


1010 3 x 50 (70)3 x 50 (70)

AWS A 2.4 rules-example

1010

5050

7070


Welds Welds this sidethis side of joint, go on the of joint, go on the unbrokenunbroken reference line while reference line while welds welds the other sidethe other side of the of the joint, go on the joint, go on the brokenbroken reference line reference line

Symbols with a Symbols with a vertical linevertical line component must be component must be drawn with the vertical line to the drawn with the vertical line to the leftleft side of side of the symbolthe symbol

All All CSACSA dimensions are shown to the dimensions are shown to the leftleft of the of the symbolsymbol

All All linearlinear dimensions are shown on the dimensions are shown on the rightright of of the symbol i.e. number of welds, length of the symbol i.e. number of welds, length of welds, length of any spaces welds, length of any spaces

Included angle and root opening are shown on Included angle and root opening are shown on toptop of the symbol of the symbol

BS EN 22553 rulesBS EN 22553 rules


z 10z 10 3 x 50 3 x 50 (50)(50)

BS EN 22553 rules - example

1010

5050

5050

All leg lengths All leg lengths shallshall be preceded by z and be preceded by z and throat by a or s (in case of deep penetration throat by a or s (in case of deep penetration welds)welds)


8888

55

5 x 85 x 8

88

Fillet weld dimensions according AWS A Fillet weld dimensions according AWS A 2.42.4

Fillet weldsFillet welds

5 leg on 5 leg on vertical vertical membermember


55

a 5 (z 8)a 5 (z 8)

88

Fillet weld dimensions according BS EN Fillet weld dimensions according BS EN 2255322553

oror

88

z 8z 8oror

z 8z 8

a 5 (z 8)a 5 (z 8)

Fillet weldsFillet welds


Intermittent fillet weldsIntermittent fillet welds

Chain intermittent fillet weldChain intermittent fillet weld

length length (l)(l)

pitch pitch (e)(e)

aa

zz

aa n×l(en×l(e))aa n×l(en×l(e))

zz n×l(en×l(e))zz n×l(en×l(e)) oror

Symbol to BS EN 22553Symbol to BS EN 22553



Chain intermittent fillet weldChain intermittent fillet weld


pitch pitch (e)(e)

zz

zz l - el - e

zz l - el - e

Symbol to AWS A2.4Symbol to AWS A2.4



Staggered intermittent fillet weldStaggered intermittent fillet weld


pitch pitch (e)(e)

aa

zz

aa n×l n×l (e)(e)aa n×l n×l (e)(e)

zz n×l n×l (e)(e)zz n×l n×l (e)(e) oror

Symbol to BS EN 22553Symbol to BS EN 22553



Staggered intermittent fillet weldStaggered intermittent fillet weld


pitch pitch (e)(e)

zz

zz l - el - e

zz l - el - e

Symbol to AWS A2.4Symbol to AWS A2.4

e/2e/2


Concave or Concave or ConvexConvex

Supplementary weld Supplementary weld symbolssymbols

Toes to be ground Toes to be ground smoothly (BS EN smoothly (BS EN only)only)

Site Site WeldWeld

Weld all Weld all roundround

Supplementary symbolsSupplementary symbols


Supplementary weld Supplementary weld symbolssymbols

Ground Ground flushflush

111111

Further supplementary information, such as Further supplementary information, such as WPS number, or NDT may be placed in the WPS number, or NDT may be placed in the fish tailfish tail

Supplementary symbolsSupplementary symbols

Welding Welding process process numerical BS numerical BS ENEN MRMR

Removable Removable backing backing stripstrip

Permanent Permanent backing backing stripstrip

MM


Fillet Fillet weldweld

Double Double VV

Double Double bevelbevel

Double UDouble U

Double JDouble J

Representation of welds done from Representation of welds done from both both sidessides of the joint intersection, touched by of the joint intersection, touched by the arrow headthe arrow head

Double side weld symbolsDouble side weld symbols


Example:Example:

Produce a drawing giving symbols for the weld Produce a drawing giving symbols for the weld given as shown below to the specification AWS given as shown below to the specification AWS A2.4A2.4

Weld DrawingWeld Drawing

Symbol Symbol DrawingDrawing

MMMMAA



Example:Example:

Draw the symbols for the weld given as Draw the symbols for the weld given as shown below to the specification BS EN shown below to the specification BS EN 2255322553

Weld drawingWeld drawing

Symbol Symbol DrawingDrawing

111111

Weld symbols on drawings

MMMMAA


1010

2020

30303535

1515

77

Student symbols exerciseStudent symbols exercise

Complete a symbols drawing for the welded Complete a symbols drawing for the welded joint given below to AWS A2.4 & BS EN joint given below to AWS A2.4 & BS EN 2255322553

All fillet weld leg lengths are 10 mmAll fillet weld leg lengths are 10 mm



Solution AWS Solution AWS A2.4A2.4 1010

3030

20201010

1010

3535

15151010



Solution BS EN Solution BS EN 2255322553 z z

1010s 30s 30

s 20s 20 z z 1010

a 7 z a 7 z 1010s 35s 35

s 15s 15z 10z 10



This has major effects on economics and This has major effects on economics and distortion control!distortion control!

The basic rule is this:The basic rule is this:

The more you take out, then the more you must put back in!

The purposes of a weld preparation is to The purposes of a weld preparation is to allow access for the welding process, allow access for the welding process, penetration and fusion through the area of penetration and fusion through the area of the joint and its facesthe joint and its faces

Weld preparationsWeld preparationsWeld preparationsWeld preparations


Weld preparationWeld preparationWeld preparation depend on:Weld preparation depend on:

•welding processwelding process

•preparation method availablepreparation method available

•accessaccess

•type of jointtype of joint

•type of parent materialtype of parent material

•thicknessthickness

•welding positionwelding position

•in-service type of loadingin-service type of loading

Weld preparation for arc welding - see BS EN Weld preparation for arc welding - see BS EN 29692!29692!


Weld preparationWeld preparation

Welding process impacts upon weld preparationWelding process impacts upon weld preparation

Arc Arc weldingwelding

EBEBWW


Weld preparationWeld preparationWelding process impacts upon weld preparationWelding process impacts upon weld preparation

MMAMMA MAMAGG

high heat input process allow a larger root face, less high heat input process allow a larger root face, less weld metal required, less distortions, higher weld metal required, less distortions, higher productivityproductivity

if gap is too big risk of possible burn-throughif gap is too big risk of possible burn-through

if gap is too small risk of lack of penetration if gap is too small risk of lack of penetration


Weld preparationWeld preparationPreparation method impacts upon weld Preparation method impacts upon weld

preparationpreparation

Requires machining slow Requires machining slow and expensiveand expensive

Tight tolerance easier set-Tight tolerance easier set-upup

Can be flame/plasma cut Can be flame/plasma cut fast and cheapfast and cheap

Large tolerance set-up can Large tolerance set-up can be difficultbe difficult


Weld preparationWeld preparationPreparation method impacts upon weld Preparation method impacts upon weld

preparationpreparation

Variations in Variations in cutting linecutting line

Root face too large lack Root face too large lack of penetrationof penetration

Root face too small burn-Root face too small burn-throughthrough

Variations in Variations in cutting anglecutting angle

Included angle too large Included angle too large heavy distortions, heavy distortions, increase amount of filler increase amount of filler metal requiredmetal required

Included angle too small Included angle too small lack of penetration, lack lack of penetration, lack of side wall fusionof side wall fusion


Weld preparationWeld preparationPreparation method impacts upon weld Preparation method impacts upon weld preparation - corrective measurespreparation - corrective measures

Backing strip (6 mm Backing strip (6 mm or more, same or more, same material)material)

No root No root faceface

Root face too Root face too largelarge

Recut groove preparationRecut groove preparation Increase root gap and Increase root gap and use backing stripuse backing strip



Preparation method impacts upon weld Preparation method impacts upon weld preparation - corrective measurespreparation - corrective measures

Too big/too Too big/too small included small included angleangle

Recut groove preparationRecut groove preparation Increase root gap and Increase root gap and use backing stripuse backing strip

Warning! Backing strips give a built-in creviceWarning! Backing strips give a built-in crevice

•susceptible to corrosionsusceptible to corrosion

•give a lower fatigue lifegive a lower fatigue life


Weld preparationsWeld preparations

Access impacts upon weld preparationAccess impacts upon weld preparation




Pipe weld preparation - one side access only!Pipe weld preparation - one side access only!

for wall thickness up to 3 for wall thickness up to 3 mmmmfor wall thickness 3 to 20 for wall thickness 3 to 20 mmmm

for wall thickness over 20 for wall thickness over 20 mmmm




Pipe weld preparation - one side access only!Pipe weld preparation - one side access only!

•self-adjusting itemsself-adjusting items

•no danger of burn-no danger of burn-throughthrough

•susceptible to susceptible to corrosioncorrosion

•lower fatigue lifelower fatigue lifeTo ensure minimum To ensure minimum root mismatch, the root mismatch, the internal bore is internal bore is sometimes machined sometimes machined with a low angled with a low angled bevelbevel


Weld preparationsWeld preparationsType of joint impacts upon weld preparationType of joint impacts upon weld preparation

•danger of burn-danger of burn-throughthrough

•difficult to set-updifficult to set-up

•easy set-upeasy set-up

•no burn-no burn-throughthrough

•corner joints require offsetcorner joints require offset

offseoffsett


Weld preparationsWeld preparationsType of joint impacts upon weld preparationType of joint impacts upon weld preparation

Bevel angle = 30ºBevel angle = 30º

Included angle = Included angle = 60º60º

Included angle = Included angle = Bevel angle = 50ºBevel angle = 50º

•lap and square edge butt joints do not lap and square edge butt joints do not require preparationrequire preparation


Weld preparationsWeld preparationsType of parent material impacts upon weld Type of parent material impacts upon weld preparationpreparation

SteelSteel AluminiumAluminium

•to reduce distortions on stainless steels to reduce distortions on stainless steels welds, reduce included angle and increase root welds, reduce included angle and increase root faceface

•to avoid lack of side wall fusion problems to avoid lack of side wall fusion problems aluminium require larger included angles than aluminium require larger included angles than steelsteel

60º60º

30º30º

70-90º70-90º

35-45º35-45º


Weld preparationsWeld preparationsThickness of parent material impacts upon Thickness of parent material impacts upon weld preparationweld preparation

•a single bevel groove requires a volume of a single bevel groove requires a volume of weld metal proportional to the square of plate weld metal proportional to the square of plate thicknessthickness

•its lack of symmetry lead to distortionsits lack of symmetry lead to distortions

Reduce shrinkage by:Reduce shrinkage by:

•reduce weld volumereduce weld volume

•use single pass weldinguse single pass welding



Reduce weld volume by:Reduce weld volume by:

•reduce included anglereduce included angle

Thickness of parent material impacts upon Thickness of parent material impacts upon weld preparationweld preparation

•reduce root gapreduce root gap




•increase root faceincrease root face


•use double bevel weld prepuse double bevel weld prep




•use U prep instead V prepuse U prep instead V prep


U prep better than V U prep better than V prepprepV prep better than U V prep better than U prepprep



Reduce distortions by using an asymmetric V Reduce distortions by using an asymmetric V prep instead of a symmetric V prepprep instead of a symmetric V prep


t/3t/3tt

•weld first into deeper sideweld first into deeper side

•after welding half of depth, root back after welding half of depth, root back gouginggouging

•weld completely on backsideweld completely on backside

•complete welding on first sidecomplete welding on first side



PF symmetric PF symmetric preparationpreparation

Welding position impacts upon weld Welding position impacts upon weld preparationpreparation

PC asymmetric PC asymmetric preparationpreparation

If symmetric preparation is used in the PC If symmetric preparation is used in the PC position the weld may spill out of the grooveposition the weld may spill out of the groove

60º60º

30º30º 60º60º

15º15º



Type of loading impacts upon weld preparationType of loading impacts upon weld preparation

Static loads - prohibited application of one Static loads - prohibited application of one sided fillet weldsided fillet weld




Static loads - equal throat T jointsStatic loads - equal throat T joints

13 mm13 mm

weld area = 160 weld area = 160 mmmm22

weld area = 90 weld area = 90 mmmm22

13 mm13 mm

•no preparation requiredno preparation required

•danger of lamellar danger of lamellar tearingtearing

•preparation requiredpreparation required

•reduced distortionsreduced distortions

6060ºº




Static loads - equal throat T beams in bendingStatic loads - equal throat T beams in bending

neutraneutral axisl axis

deep deep penetration penetration fillet weldsfillet welds

normal fillet normal fillet weldswelds

neutraneutral axisl axis

Lower neutral axis is more advantageous Lower neutral axis is more advantageous (also helps to reduce residual distortions!)(also helps to reduce residual distortions!)




Dynamic loads - full vs. partial penetration Dynamic loads - full vs. partial penetration weldswelds

double bevel double bevel weldweld

fillet weldsfillet welds

Lack of penetration promotes cracking!Lack of penetration promotes cracking!

cyclic loadcyclic load

6. welding symbols & weld preparations

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