Basic Weld Symbols — EN 22553

Weld Type Symbol Illustration Description
Fillet weld △ Triangular cross-section Most common structural weld
Butt weld (square) ‖ Square edges Thin material, full penetration
Single V butt V V-shaped groove Single-sided full penetration
Double V butt X Double V groove Double-sided full penetration
Single bevel ╱ Bevel on one plate Single-sided, one plate beveled
Double bevel K K-shaped groove Double-sided bevel
Plug weld ○ Circular hole filled Lap joints, light framing
Spot weld ● Circular spot Thin sheet metal
Seam weld — Continuous seam Thin sheet, continuous

Symbol Placement

EN 22553 uses a reference line with an arrow:

        Other side symbol
        ┌──────┐
        │      │
────────┤      ├──── arrow
        │      │
        └──────┘
        Arrow side symbol

Fillet Weld Callout Structure

Standard Callout Format

  α      l_1     (e)
───◇───────────────
 a      l_2     n ×
Component Meaning Example
a Throat thickness (mm) a4
α Included angle (degrees) —
l_1 Weld length (mm) 100
l_2 Intermittent weld length (mm) 50
n × Number of intermittent segments 4×
e Spacing between segments (mm) (200)

Example Callouts

Symbol Callout Meaning
◇ a4 4 mm throat continuous fillet weld
◇ a6 100 6 mm throat, 100 mm long fillet weld
◇ a5 6×50(200) 6 intermittent 50 mm welds of a5 at 200 mm centres
◇ a8 around 8 mm throat continuous fillet all around
△ Arrow side fillet weld only

Butt Weld Symbols

Single-Sided Butt Welds

Symbol Full Penetration Notation Example Callout
V U symbol inside V V ✓ indicates full pen
V No symbol Partial penetration

Double-Sided Butt Welds

Symbol Meaning Typical Root Gap
X Double V butt — both sides 2-3 mm
K Double bevel — one piece square 2-3 mm

Supplementary Symbols

Symbol Meaning Placement
◇ (flag) Field weld At the arrow-reference line junction
○ (circle) Weld all around At the arrow-reference line junction
⌴ (square) Backing strip Below reference line
✓ Full penetration Inside the V-symbol
∪ Flat finish Above the weld symbol
⌢ Convex finish Above the weld symbol
⌣ Concave finish Above the weld symbol

Field Weld Symbol

The flag symbol at the arrow-reference line junction indicates that welding is to be performed in the field (site welding) rather than in the fabrication shop.

All Around Symbol

The circle at the arrow-reference line junction indicates that the weld extends continuously around the joint perimeter.

Practical Examples

Detail Symbol Callout
6 mm fillet both sides, full length ◇ a6 (both sides)
8 mm fillet, all around ◇ a8 with ○ at junction
Field weld, 5 mm fillet, 100 mm long ◇ a5 100 with flag
Full penetration V-butt V with ✓, a=t
Intermittent fillet, 4 runs of 50 mm at 200 mm centres ◇ a4 4×50(200)

Frequently Asked Questions

What is the difference between EN 22553 and AWS A2.4 weld symbols?

EN 22553 (ISO 2553) uses a dashed reference line where symbols above and below distinguish arrow side from other side. AWS A2.4 uses the same line but symbol placement differs slightly. The most significant difference is in the weld all around symbol (○ in both) and field weld flag (◇ in EN 22553, flag in AWS). EN 22553 uses throat thickness "a" while AWS typically uses leg length "w".

How do I indicate a field weld on EN 22553 drawings?

A field weld is indicated by a flag symbol at the junction of the arrow and reference line. The flag points toward the arrow tail. Without the flag, the weld is assumed to be performed in the fabrication shop. Site welding requires additional quality control per EN 1090-2.

Related Pages

Educational reference only. Weld symbols per EN 22553:2019 (ISO 2553:2019). Verify symbol meaning per project welding specification. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent verification.

EN ISO 2553 vs AWS A2.4 Symbol Comparison

European welding symbols (EN ISO 2553) and American symbols (AWS A2.4) serve the same purpose but use different conventions:

Feature EN ISO 2553 AWS A2.4
Reference line side Dashed line = arrow side; solid = other Arrow side vs other side by symbol position
Weld size location Left of symbol (a or z for throat/leg) Left of symbol (leg size in inches)
Weld length location Right of symbol Right of symbol
Intermittent weld l(e) notation for length and spacing Length-pitch notation (e.g., 2-5)
Peripheral weld flag Circle at arrow/reference line junction Circle at arrow/reference line junction
Site weld flag Flag symbol at junction Flag symbol at junction
Supplementary symbols Flat, convex, concave, toe blended Same set (flat, convex, concave)
Backing run symbol R on reference line Backing symbol (rectangle)

Key distinction: In ISO 2553, the dashed identification line indicates the arrow side -- if the dashed line is BELOW the solid reference line, the symbol on the solid line applies to the arrow side. AWS uses symbol position above/below the reference line with the arrow side always "near side."

Weld Strength Quick Reference for European Structural Steels

For fillet welds per EN 1993-1-8 Clause 4.5.3, design shear strength f_vw,d:

Steel Grade fu (MPa) Electrode (matching) f_vw,d (MPa) Per mm leg (kN/mm)
S235 360 E35 (35 grade) 207.8 0.147
S275 430 E42 (42 grade) 248.3 0.176
S355 490 E50 (50 grade) 282.9 0.200
S420 520 E55 (55 grade) 300.3 0.212
S460 540 E60 (60 grade) 311.8 0.221

Where fvw,d = fu / (sqrt(3) * betaw * gamma_M2), beta_w = 0.80 (S235), 0.85 (S275), 0.90 (S355-S460), gamma_M2 = 1.25.

For a 6 mm fillet weld in S355: design capacity = 0.200 * 6 = 1.20 kN/mm of weld length. A 100 mm intermittent weld segment provides 120 kN of design shear capacity.

Supplementary Weld Symbols (EN ISO 2553)

Deeper detail on supplementary symbols beyond the basic weld type symbols:

Symbol Name Meaning
--- Flat contour Weld face finished flush with base metal
~~~ Convex contour Weld face convex (as-welded, not ground)
( Concave contour Weld face concave (throat as specified)
\/ Toe blended Smooth transition at weld toe (fatigue critical)
M Machining finish Post-weld machining required
G Grinding finish Post-weld grinding to specified contour
C Chipping finish Mechanical chipping to remove slag/roughness

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