Welding Symbols South Africa: How to Read Weld Symbols, Fabrication Drawings, Joints & Welding Instructions

QUICK ANSWER

Welding symbols are a standardised way of communicating what weld must be produced on an engineering or fabrication drawing. A welding symbol can tell the welder where the weld belongs, what type of weld is required, its dimensions, length, spacing, contour and other fabrication requirements.

South African fabrication personnel may encounter both the ISO 2553 system and the AWS A2.4 system. The systems are related in purpose but should not be casually treated as identical. SAIW currently teaches both systems because South African welders, supervisors, inspectors, draughting personnel and quality staff can encounter both in practice. SAIW

Question	Fast Answer
What is a welding symbol?	A drawing instruction used to communicate a welding requirement
Who must understand them?	Welders, fabricators, supervisors, inspectors, QC personnel, designers and draughting staff
Are weld symbols and welding symbols the same thing?	Not exactly — the weld symbol is normally one component within the complete welding symbol
Which standards may South African welders encounter?	ISO 2553 and AWS A2.4 are two important systems
Can a symbol show weld size?	Yes
Can it show length and spacing?	Yes
Can it indicate which side of the joint is welded?	Yes
Does reading a symbol replace a WPS?	No
Should a welder guess if the drawing is unclear?	No — ambiguity should be resolved before welding

Why Welding Symbols Matter in Real Fabrication

A fabrication drawing has to communicate far more than:

“Weld these two pieces together.”

The workshop may need to know:

• which joint is involved;

• where the weld must be placed;

• what weld type is required;

• how large the weld must be;

• whether welding is continuous or intermittent;

• how long the weld must be;

• whether spacing is specified;

• whether all-around welding is required;

• whether a particular contour is required;

• whether finishing is specified;

• whether a procedure or additional instruction applies.

That is why welding symbols exist.

ISO 2553 defines rules for representing welded joints symbolically on technical drawings and states that the representation can communicate information relating to weld geometry, manufacture, quality and testing. ISO

AWS A2.4 similarly provides a system for communicating welding, brazing and nondestructive-examination requirements by means of symbols. AWS Publications

A welder who cannot interpret the drawing correctly can produce a technically competent weld in the wrong place, wrong size or wrong configuration.

That is not a small mistake.

It is a fabrication error.

Weld Symbol vs Welding Symbol: What Is the Difference?

These two terms are often used interchangeably, but technically there is a useful distinction.

ISO describes a welding symbol as the complete graphical instruction that includes elements such as the arrow line and reference line and may also include elementary symbols, supplementary symbols, dimensions and a tail. ISO

Think of it this way:

Weld symbol

The small graphical element identifying the type of weld.

Examples can represent:

• fillet weld;

• square groove;

• V-groove;

• bevel groove;

• U-groove;

• plug/slot weld;

• spot weld;

• seam weld;

• surfacing;

• edge weld.

Welding symbol

The complete instruction containing the weld symbol plus the information required to interpret the welding requirement.

That can include:

arrow + reference line + weld symbol + dimensions + supplementary information + tail

This distinction matters because recognising a triangle as a fillet weld symbol is only the beginning.

The fabricator still needs to determine:

Where?What size?How long?How many?What spacing?Which side?What contour?What additional instruction?

Anatomy of a Welding Symbol

A welding symbol should be read systematically rather than visually guessed.

1. Arrow

The arrow points to the relevant joint or location on the drawing.

It tells the reader:

This is the joint to which this welding instruction applies.

The arrow itself does not always tell you everything about weld placement.

You still need to interpret the reference-line convention being used.

2. Reference line

The reference line is the central organisational element of the welding symbol.

Other information is positioned relative to it.

It acts like the sentence onto which the remaining welding instruction is written.

3. Weld symbol

The weld symbol identifies the basic type of weld being requested.

For example:

fillet → groove → plug → slot → spot → seam → edge

The welder should not select a completely different joint merely because it is easier to weld.

The drawing requirement must first be understood.

4. Dimensions

Dimensions surrounding the symbol may communicate information such as:

• weld size;

• groove depth;

• root opening;

• effective throat;

• weld length;

• pitch;

• number of welds;

• angle.

Exactly how this information is represented depends on the standard and drawing convention.

5. Supplementary symbols

Additional graphical information can specify characteristics such as:

• all-around welding;

• site/field welding;

• contour;

• backing;

• melt-through;

• other supplementary requirements depending on the applicable system.

6. Tail

The tail can provide additional information where required.

Depending on the drawing and standard, it may reference:

• process;

• specification;

• procedure;

• standard;

• other instruction.

A tail being present does not mean a welder should automatically invent the missing information.

Read what is actually specified.

The Most Important Rule: Identify the Standard First

This is one of the most important improvements SSA can make over generic welding-symbol articles.

Before decoding individual marks, ask:

Which symbolic system is this drawing using?

That matters because South African fabrication environments can encounter both ISO and AWS conventions.

SAIW specifically teaches both:

• ISO 2553

• AWS A2.4

and notes that difficulties can arise in engineering design and fabrication workshops because two systems are used. SAIW

Do not assume:

“A welding symbol is a welding symbol.”

The general concepts overlap.

The precise interpretation conventions may differ.

ISO 2553 Welding Symbols

ISO 2553 is the international standard covering symbolic representation of welded joints on technical drawings.

The current published edition at the time of writing is ISO 2553:2019, although ISO has a replacement edition under development in 2026. ISO

ISO 2553 recognises two approaches for identifying the sides of a joint:

• a dual-reference-line system;

• a single-reference-line system.

That is one reason readers should identify the drawing system before assuming that a symbol placed in one location carries the same meaning under another convention. ISO

Important 2026 note

Because a new ISO 2553 edition is currently under development, employers, designers and fabricators should verify the contractual or drawing standard actually specified for the project rather than assuming that the newest draft automatically governs existing work. ISO

AWS A2.4 Welding Symbols

AWS A2.4 is the American Welding Society standard for:

welding, brazing and nondestructive examination symbols.

The current AWS edition is AWS A2.4:2020. AWS describes it as establishing a method for communicating welding, brazing and examination information through symbols. AWS Publications

AWS documentation also emphasises correct interpretation of the arrow-side / other-side convention, because misunderstanding this can cause the weld to be placed on the wrong side of a joint. American Welding Society

For a South African welder, this reinforces one principle:

Never interpret the symbol in isolation from the drawing standard.

ISO vs AWS: Do Not Treat Them as Identical

Question	ISO 2553	AWS A2.4
International standard?	Yes	Primarily AWS / American system
Used for welding symbols?	Yes	Yes
Covers welded-joint representation?	Yes	Yes
May be encountered in South Africa?	Yes	Yes
Same conventions in every respect?	No	No
Should the drawing standard be identified first?	Yes	Yes

The mistake to avoid is learning a single chart and then assuming every drawing globally is interpreted in exactly the same way.

That approach can produce serious workshop errors.

Common Weld Types You May See on Fabrication Drawings

Fillet weld

Fillet welds are among the most common welds in fabrication.

They are frequently used in:

• T-joints;

• lap joints;

• corner configurations;

• brackets;

• stiffeners;

• frames;

• structural assemblies.

A fillet weld symbol usually needs more interpretation than:

“Make a fillet weld.”

The drawing may also specify:

• size;

• length;

• spacing;

• whether the weld is continuous;

• whether it is intermittent;

• which side is welded;

• whether both sides are welded;

• contour.

Groove / Butt Weld Symbols

Groove welds are often associated with joints requiring preparation before welding.

Possible joint preparations include:

• square;

• V;

• bevel;

• U;

• J;

• flare configurations.

The drawing may need to communicate:

• groove form;

• included angle;

• root face;

• root opening;

• depth of preparation;

• weld size;

• penetration requirement.

A welder should not casually grind a V-groove because “that is how we normally do it.”

The drawing, WPS and fabrication procedure must agree.

Plug and Slot Welds

Plug and slot welds can be used to join overlapping components through prepared openings.

The reader may need to interpret information relating to:

• opening dimensions;

• number of welds;

• spacing;

• fill;

• location.

Again, the symbol is a production instruction.

It should not be interpreted from appearance alone.

Spot and Seam Welds

Spot and seam welding symbols may appear in sheet-metal and production environments.

Relevant information can include:

• spacing;

• number;

• length;

• weld location;

• pitch.

These are not automatically interpreted in the same manner as a manual fillet-weld callout.

Surfacing Welds

Surfacing can involve depositing weld metal onto a surface rather than joining two separate components.

Applications may include:

• build-up;

• repair;

• dimensional restoration;

• wear resistance;

• hardfacing.

The symbol therefore communicates a different manufacturing purpose from an ordinary joint weld.

Arrow Side vs Other Side: Where Does the Weld Go?

This is where many beginners become confused.

The drawing may point to a joint, but the weld itself can be required on:

• the arrow side;

• the other side;

• both sides.

The exact graphical convention depends on the standard.

AWS explicitly treats arrow-side/other-side interpretation as a critical part of correct symbol use. American Welding Society

The safe workflow is:

identify standard → locate arrow → identify reference-line convention → locate weld symbol → establish required side

Do not simply weld whichever side is physically easiest to access.

What Does Weld Size Mean?

A welding symbol can communicate weld dimensions.

For fillet welding, size is particularly important because an apparently large weld is not automatically the correct weld.

Potential problems from incorrect sizing include:

Too small

• insufficient required weld size;

• inadequate design capacity;

• rejection during inspection.

Too large

• unnecessary filler-metal consumption;

• extra heat input;

• slower production;

• increased distortion;

• increased labour;

• unnecessary cost.

The correct objective is not:

“Make the biggest weld possible.”

It is:

Produce the weld specified by the design and applicable procedure.

Weld Length

A welding symbol may specify the required length of weld.

This matters because a weld may be:

• continuous;

• limited to a defined length;

• repeated intermittently.

If the drawing requires 50 mm of weld, welding the whole joint is not automatically an improvement.

Additional welding can change:

• heat input;

• distortion;

• production time;

• cost;

• residual stress.

Follow the design.

What Is Weld Pitch?

Pitch generally relates to spacing in intermittent welding.

A drawing can require repeated weld segments separated according to a specified pattern.

The fabricator therefore needs to establish:

• weld length;

• centre-to-centre spacing;

• number/location;

• staggered or chain arrangement where applicable.

Do not confuse:

weld length with pitch.

They answer different questions.

Continuous vs Intermittent Welding

Continuous welding

The weld runs continuously through the specified length.

Intermittent welding

Separate weld segments are placed according to the drawing.

Intermittent arrangements can be used where full continuous welding is unnecessary or where design and fabrication considerations favour segmented welding.

The operator should never convert one to the other without authorisation.

Chain vs Staggered Intermittent Welds

Where welds occur on both sides of a joint, intermittent welds may be arranged differently.

Chain arrangement

Segments occur opposite each other.

Staggered arrangement

Segments alternate.

The difference affects where the welds are physically placed.

This is another reason a welder must interpret the complete symbol instead of seeing only the basic fillet symbol.

What Does the All-Around Symbol Mean?

An all-around indication tells the fabrication team that welding is required around the applicable joint or feature rather than only along one local segment.

That does not mean:

“Weld every visible edge.”

It means the symbol must be interpreted in relation to the indicated joint.

What Does a Field / Site Weld Symbol Mean?

Some symbolic systems include a method of indicating that a weld is to be made at site or in the field rather than in the original fabrication shop.

That distinction can matter for:

• sequencing;

• access;

• inspection;

• transport;

• erection;

• temporary fit-up;

• environmental controls.

Field welding can also introduce different practical conditions from controlled workshop welding.

Weld Contour Symbols

A drawing may specify the desired weld surface contour.

Common concepts include:

• flush/flat;

• convex;

• concave.

The required contour should not be confused with the operator's personal preference.

The design or specification determines the requirement.

Finish Requirements

A drawing may also specify a required method or finish associated with the weld profile.

This could relate to processes such as:

• grinding;

• machining;

• finishing.

Again:

do not grind a weld flush merely because it looks neater.

Removing weld metal can change the final weld geometry.

Welding Symbol vs WPS: Which One Controls the Welder?

They perform different jobs.

Document / Instruction	Primary Job
Drawing	Shows what must be fabricated
Welding symbol	Communicates the required weld on that drawing
WPS	Defines how the weld should be produced within the qualified procedure
Welder qualification	Demonstrates that the welder can perform within a defined qualification range
Inspection criteria	Determines how the completed weld is evaluated

A symbol might tell you:

Make this type and size of weld here.

The WPS can tell you:

• process;

• consumable;

• current;

• voltage;

• travel control;

• preheat;

• interpass requirements;

• shielding;

• joint preparation;

• other procedure variables.

The welder must reconcile both.

A beautifully executed weld that does not match the drawing is not correct fabrication.

A weld matching the symbol but produced outside the applicable WPS may also create a compliance problem.

How to Read a Welding Symbol Step by Step

Do not begin by staring at the triangle or groove symbol.

Use a sequence.

Step 1 — Identify the applicable standard

Look at:

• drawing notes;

• title block;

• project specification;

• welding specification.

Ask:

ISO or AWS?

Step 2 — Identify the joint

Determine what components are being joined.

Possible examples:

• butt joint;

• T-joint;

• lap joint;

• corner joint;

• edge joint.

Step 3 — Follow the arrow

Identify the exact joint or feature being referenced.

Step 4 — Read the weld symbol

Determine the required weld type.

Examples:

• fillet;

• V-groove;

• bevel;

• square groove;

• plug;

• slot;

• spot;

• seam;

• surfacing.

Step 5 — Determine the side

Ask:

• arrow side?

• other side?

• both sides?

Interpret this according to the governing symbol system.

Step 6 — Read the dimensions

Check for:

• weld size;

• preparation depth;

• root opening;

• angle;

• weld length;

• pitch;

• quantity.

Step 7 — Read supplementary information

Look for:

• all-around;

• site/field weld;

• contour;

• finish;

• backing;

• additional requirements.

Step 8 — Check the tail

Determine whether a process, standard or other instruction is referenced.

Step 9 — Find the applicable WPS

The drawing tells you the required result.

The WPS tells you how the welding operation is controlled.

Step 10 — Resolve ambiguity before welding

If the symbol appears contradictory, incomplete or unclear:

STOP.

Ask:

• supervisor;

• welding coordinator;

• inspector;

• responsible engineer;

• authorised technical person.

Do not guess.

Practical Drawing Interpretation Example

Imagine a fabrication drawing points to a T-joint.

The symbol indicates:

• fillet weld;

• specified side;

• particular weld size;

• defined length.

Before starting, the welder should establish:

1. Which symbolic system applies?

2. Which side of the joint is required?

3. What fillet size is specified?

4. Is the weld continuous or limited length?

5. Is there an intermittent pitch?

6. Is a contour requirement shown?

7. Is an all-around requirement present?

8. Does the tail reference anything?

9. Which WPS applies?

10. Does joint preparation match the drawing?

That is professional drawing interpretation.

Not:

“I saw a triangle so I made a fillet weld.”

Why Welding Symbols Matter for Coded Welders

A coded welder may be tested or employed within work controlled by:

• procedures;

• drawings;

• specifications;

• code requirements.

Your ability to physically produce a good weld is only part of the job.

You must also understand what you are being instructed to produce.

SSA's coded-welding guide already emphasises that a coded welder must understand the actual procedure, process, material, joint and test requirement rather than treating “coded” as a universal qualification. Swift Skills Academy

Welding-symbol literacy strengthens that same discipline.

Why Welding Symbols Matter for Visual Weld Inspection

An inspector cannot properly determine whether the finished weld corresponds to the drawing without understanding:

• required weld type;

• size;

• location;

• length;

• profile;

• supplementary instructions.

Inspection is therefore not simply:

“Does this weld look nice?”

It is:

Does the physical weld comply with the specified requirement?

That is a completely different standard of thinking.

Why Welding Symbols Matter to Employers

For employers, welding-symbol competence affects:

Productivity

Fewer drawing-interpretation errors.

Rework

Incorrect weld placement or size can require removal and repair.

Material usage

Overwelding consumes more:

• filler;

• gas;

• electricity;

• labour;

• grinding time.

Quality

Work can be compared to specified fabrication requirements.

Communication

Designers, supervisors, welders and inspectors work from a common technical language.

Common Welding-Symbol Mistakes

Mistake 1 — Looking only at the basic weld symbol

A triangle alone is not the whole instruction.

Read everything around it.

Mistake 2 — Ignoring arrow side vs other side

This can put a perfectly acceptable weld on the wrong side of the joint.

Mistake 3 — Confusing weld length and pitch

They represent different requirements.

Mistake 4 — Assuming bigger is better

Overwelding can increase:

• heat input;

• distortion;

• cost;

• production time.

Mistake 5 — Ignoring the drawing standard

ISO and AWS conventions should not be assumed to be identical.

Mistake 6 — Ignoring the WPS

Drawing interpretation and procedure compliance must work together.

Mistake 7 — Grinding every weld flush

Only do so when required and permitted.

Mistake 8 — Guessing unclear symbols

Ambiguity should be escalated.

Welding Symbols for Beginners: What Should You Learn First?

A beginner does not need to memorise an entire welding-symbol standard on day one.

Learn in layers.

Stage 1

Understand:

• arrow;

• reference line;

• joint;

• weld symbol.

Stage 2

Learn:

• fillet welds;

• groove welds;

• side/location.

Stage 3

Add:

• size;

• length;

• pitch;

• intermittent welding.

Stage 4

Add:

• contour;

• all-around;

• site weld;

• supplementary symbols.

Stage 5

Practise:

drawing → symbol → joint → WPS → physical weld

That last step converts symbol knowledge into workshop competence.

Can You Learn Welding Symbols Without Learning Welding?

You can study the graphical language independently.

But practical welding knowledge makes the symbols far easier to understand.

Someone who understands:

• joints;

• groove preparation;

• fillet size;

• penetration;

• weld positions;

• distortion;

• welding procedures;

can connect the drawing instruction to the physical fabrication task.

That is why symbol training is especially useful alongside actual fabrication and welding experience.

Who Should Learn Welding Symbols?

SAIW identifies a broad audience for welding-symbol training, including fabrication personnel, supervisors, quality controllers, inspectors, designers, draughting personnel and detailers. SAIW

For SSA's audience, this includes:

• beginner welders;

• experienced welders;

• fabricators;

• boilermakers;

• coded-welder candidates;

• workshop supervisors;

• welding inspectors;

• QC personnel;

• engineering draughting staff;

• maintenance teams;

• employer technical teams.

Welding Symbols and South African Qualifications

There is historical South African unit-standard material specifically addressing welding definitions and symbols.

SAQA's older Unit Standard 14713 — Use welding definitions and symbols states that learners in fabrication and welding should be able to:

• interpret welding definitions;

• identify and apply welding symbols;

• sketch and describe welding symbols.

It also links welding symbols to weld preparation, fabrication requirements and use of a WPS. That older standard has passed its end date and was replaced by Unit Standard 253736, also titled Use welding definitions and symbols. SAQA

This historical material remains useful for understanding the importance South African occupational training placed on drawing and symbol literacy.

But do not market the old record as though it were automatically a currently open enrolment route.

That distinction matters.

Is Welding-Symbol Knowledge a Qualification?

No.

Knowing how to interpret welding symbols does not automatically make someone:

• a qualified artisan;

• a Red Seal welder;

• a coded welder;

• a welding inspector;

• a welding engineer.

It is an important technical competency.

Its value depends on how it integrates with:

• practical welding skill;

• fabrication knowledge;

• procedure understanding;

• inspection;

• occupational competence.

What Should a Welder Check Before Starting Work From a Drawing?

Use this checklist:

Check	Question
Drawing revision	Am I using the current approved drawing?
Standard	ISO, AWS or another specified system?
Joint	Which components are being joined?
Arrow	Which joint does this instruction apply to?
Weld type	What weld is specified?
Side	Arrow side, other side or both?
Size	What dimension is required?
Length	Continuous or specified length?
Pitch	Is intermittent spacing specified?
Contour	Is a profile required?
Finish	Is finishing specified?
Tail	Is additional information referenced?
WPS	Which procedure applies?
Material	Does it match the procedure?
Fit-up	Is joint preparation correct?
Clarification	Is anything ambiguous?

This would also form the core of the downloadable PDF.

What Should Employers Assess?

An employer can test symbol competence practically.

Give the employee a controlled fabrication drawing and ask them to identify:

1. joint type;

2. weld type;

3. welding side;

4. weld size;

5. length;

6. pitch;

7. contour;

8. supplementary requirements;

9. applicable WPS;

10. physical preparation required.

That provides far more meaningful evidence than asking:

“Do you know welding symbols?”

Frequently Asked Questions

What are welding symbols?

Welding symbols are graphical instructions used on technical drawings to communicate welding requirements such as weld type, location, dimensions and supplementary fabrication information.

What is the difference between a weld symbol and a welding symbol?

The weld symbol identifies the basic type of weld. The welding symbol is the complete instruction containing the reference line, arrow and potentially weld symbols, dimensions, supplementary information and tail. ISO explicitly distinguishes these concepts. ISO

Which welding-symbol standard is used in South Africa?

South African fabrication environments can encounter more than one system. SAIW specifically trains both ISO 2553 and AWS A2.4 because both systems may be encountered in industry. SAIW

What is ISO 2553?

ISO 2553 is the international standard for symbolic representation of welded joints on technical drawings. The current published edition is ISO 2553:2019, with a replacement edition under development in 2026. ISO

What is AWS A2.4?

AWS A2.4 is the American Welding Society standard governing symbols used for welding, brazing and nondestructive examination. The current AWS edition is A2.4:2020. AWS Publications

What does the triangle welding symbol mean?

A triangular weld symbol is commonly associated with a fillet weld. The complete requirement still depends on its position, dimensions and other information attached to the welding symbol.

What does a number next to a welding symbol mean?

It may specify a dimension such as weld size, length, pitch or another requirement depending on its location and the applicable standard. Do not interpret the number without reading the complete symbol.

What does arrow side mean in welding?

Arrow side identifies the side of the joint associated with the arrow under the applicable symbolic convention. The exact placement rules should be interpreted according to the governing standard.

What does pitch mean on a welding symbol?

Pitch generally relates to the spacing of repeated intermittent welds. It should not be confused with the length of each weld segment.

What does all-around welding mean?

It indicates that welding is required around the relevant joint or feature defined by the symbol rather than only at one isolated location.

Does a welding symbol tell you how to weld?

Not completely. The drawing defines the fabrication requirement. The applicable WPS provides controlled welding instructions such as process, consumable, parameters and other procedure variables.

Can welders use a welding-symbol chart at work?

A quick-reference chart can help with recognition and training, but project drawings should always be interpreted under the specified standard, procedure and employer requirements.

Do coded welders need to understand welding symbols?

For fabrication work involving drawings and procedures, the ability to interpret technical requirements is highly valuable. A coded qualification itself remains specific to its own defined process, material, position, standard and test range. Swift Skills Academy

Is there a South African welding-symbol course?

SAIW currently offers a dedicated one-day Welding Symbols course covering ISO 2553 and AWS A2.4, aimed at fabrication, inspection, quality, design and draughting personnel. SAIW

Authoritative Sources & Regulatory References

Authoritative Source	What It Supports
ISO – ISO 2553:2019	International rules for symbolic representation of welded joints and the distinction between reference-line systems.
ISO – Draft Replacement for ISO 2553	Confirms a replacement edition is under development in 2026.
American Welding Society – AWS A2.4:2020	Current AWS standard covering welding, brazing and NDE symbols.
American Welding Society – Definitions & Symbols Committee	Confirms AWS A2.4:2020 and AWS welding-symbol chart resources.
SAIW – Welding Symbols	South African industry context, ISO/AWS systems and target fabrication audiences.
SAQA – Use Welding Definitions and Symbols	Historical South African occupational outcomes involving symbol interpretation, joint terminology and WPS awareness.

Read More

Read More	Why Read It
Coded Welding South Africa: How to Become a Coded Welder	Understand how drawings, procedures, welding position, process and qualification scope connect to coded-welder preparation.
Welding Course Requirements South Africa	Compare beginner, advanced, coded-welding and artisan pathways before choosing training.
Welding Courses Cape Town	Explore MIG, TIG, Stick, gas, pipe and coded-welding pathways in the wider Cape Town training cluster.

Final Word

A welder who understands only how to strike an arc can produce a weld.

A welder who can also interpret:

drawing → symbol → joint → dimensions → WPS → finished weld

can operate at a completely different level of fabrication discipline.

That is why welding symbols should not be treated as obscure classroom theory.

They are part of the language connecting:

designer → draughtsperson → supervisor → welder → inspector → finished component

For South African learners, employers and fabrication teams, the strongest approach is not simply to memorise symbols.

It is to learn how to read the complete welding instruction, identify the applicable standard, connect the drawing to the WPS, and turn that information into the correct physical weld.

And when anything on the drawing is unclear:

do not guess — clarify before welding.