Weld Symbols

Understanding weld symbol components:

Reference Line:
- Horizontal line
- Always present
- Information attached to it
- Foundation of symbol

Arrow:
- Points to joint
- Identifies joint location
- Can have break (for specific sides)
- May point to one or both members

Arrow Side vs Other Side:
- Below reference line = arrow side
- Above reference line = other side
- Arrow points to arrow side
- Critical for interpretation

Tail:
- Optional element
- Contains specifications:
- Welding process
- Filler metal
- Reference standards
- Omitted if not needed

Basic Weld Symbols:

Fillet Weld:
- Triangle shape
- Most common weld
- Size on left of symbol
- Length/pitch on right

Groove Welds:
- V-groove, bevel, J, U
- Shape indicates preparation
- Angle and root opening specified
- Complete or partial penetration

Plug/Slot:
- Rectangle (plug) or elongated
- Size and spacing specified
- Fill depth if partial

Surfacing:
- Semicircle below line
- Height specified
- For buildup/hardfacing

Supplementary Symbols:

Contour:
- Flat, convex, or concave
- Finishing method if specified
- G = grind, M = machine, C = chip

Weld All Around:
- Circle at reference/arrow junction
- Complete perimeter weld

Field Weld:
- Flag at reference/arrow
- Not done in shop

Backing/Spacer:
- Rectangle on reference line
- R if removed after welding
- M for removable spacer

Stagger:
- Staggered intermittent welds
- Symbols offset on reference line

Specifying weld size and extent:

Fillet Weld Sizing:

Leg Size:
- Number to left of symbol
- Single number = equal legs
- Two numbers = unequal legs
- In inches or mm

Length:
- Number to right of symbol
- In inches or mm
- No dimension = full length

Intermittent:
- Length-pitch format
- Example: 2-4 (2" welds on 4" centers)
- Both sides specified independently

Groove Weld Specifications:

Depth of Preparation:
- In parentheses
- Left of weld symbol
- Indicates preparation depth

Effective Throat:
- No parentheses
- Left of symbol
- Actual weld penetration

Root Opening:
- Inside weld symbol
- Gap at root
- Required for some joints

Groove Angle:
- Outside weld symbol
- Degrees of preparation
- For V, bevel, J grooves

Complete Joint Penetration:
- CJP in tail or on symbol
- Full penetration required
- No depth specified

Multiple Reference Lines:

Purpose:
- Show sequence of operations
- First operation closest to arrow
- Subsequent operations further

Example:
- First: root pass
- Second: fill passes
- Third: finishing

Quality Designations:

In Tail:
- Process specification
- Filler metal class
- NDE requirements

On Drawing:
- Welding procedure reference
- Testing requirements
- Acceptance criteria

Standard References:
- AWS D1.1, D1.2, etc.
- ASME Section IX
- Company specifications

Practical weld symbol usage:

Fillet Weld Examples:

Equal Leg Fillet:
```
|
5 |___
| /|
| / |
|/__|
```
5/16" or 5mm leg size both sides

Unequal Leg:
```
3
|
5 |___
|
```
Oriented with longer leg against reference

Groove Weld Examples:

V-Groove CJP:
- V symbol both sides
- No depth = complete penetration
- Angle and root specified

Partial Penetration:
- Depth in parentheses
- Specific throat requirement

Combination Welds:

Fillet + Groove:
- Both symbols on reference line
- Common for corner joints
- Each sized independently

Both Sides:
- Symbol above and below line
- May be same or different
- Indicates two welds

Special Cases:

Back Weld:
- After main weld
- Reinforcement opposite side
- Symbol on opposite side of reference

Backing:
- Before main weld
- Supports root pass
- Square on reference line

Staggered Intermittent:
- Symbols offset vertically
- Specified length-pitch
- Alternating pattern

Reading Complex Symbols:

Process:
1. Identify joint location (arrow)
2. Determine which side(s)
3. Read weld type(s)
4. Note sizes and lengths
5. Check supplementary symbols
6. Review tail specifications

Using weld symbol knowledge:

For Welders:
- Read and execute specifications
- Understand quality requirements
- Avoid interpretation errors
- Communicate with engineering

For Inspectors:
- Verify correct interpretation
- Check dimensional compliance
- Document findings
- Reference specifications

For Engineers:
- Specify requirements clearly
- Communicate design intent
- Match symbols to analysis
- Review fabrication

Training Resources:

Standards:
- AWS A2.4 (comprehensive reference)
- AWS B1.11 (workmanship standards)
- ISO 2553 (international)

Courses:
- AWS welding symbol courses
- Trade school programs
- Online training
- In-house training

Practice:
- Symbol flashcards
- Drawing interpretation exercises
- Practical application
- Mentor review

Certifications:

Welders:
- AWS QC1 (Certified Welder)
- Must demonstrate symbol knowledge
- Part of qualification testing

Inspectors:
- CWI includes symbol interpretation
- Essential for certification
- Tested on exam

Career Impact:

Entry Level:
- Basic symbol reading
- Common weld types
- Standard dimensioning

Intermediate:
- Complex symbols
- Multiple reference lines
- All weld types

Advanced:
- Symbol specification
- Standard development
- Training capability

Weld symbol proficiency is fundamental to welding and fabrication careers.